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The Biology of Craniofacial Bone Regeneration.

The Biology of Craniofacial Bone Regeneration. R.T. FRANCESCHI, R. GOPALAKRISHNAN (University of Michigan, Ann Arbor, MI) This symposium will relate knowledge gained from basic studies in craniofacial and bone biology toward the development of clinically relevant regeneration strategies. An overall theme to be emphasized throughout the four talks is that bone development involves cooperative interactions between a number of signaling pathways and gene networks that may eventually be exploited to induce precisely controlled regeneration. Dr. Jill A. Helms (UCSF) will describe early patterning events and changes in gene expression necessary for the development of specific intramembranous bones of the skull. Dr. Vicki Rosen (Harvard School of Dental Medicine and Forsyth Institute) will focus her discussion on upstream and downstream events involved in bone morphogenetic protein activity and interactions between BMP and other signaling pathways in bone development and regeneration. Dr. Renny T. Franceschi (U of Michigan) will then describe the central role of the Cbfa1 transcription factor in bone development and give examples of the many ways this factor interacts with other transcription factors and signal transduction pathways to regulate bone-specific gene expression. The final talk by Dr. R. Bruce Rutherford (U of Michigan) will provide examples of how knowledge about the biology of bone formation can be exploited to design specific gene therapy strategies for craniofacial bone regeneration. This symposium will be of broad interest to basic scientists, clinicians and tissue engineers wishing to learn more about craniofacial development and bone regeneration.


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Opacities compatible with enamel fluorosis in Jamaican school children. R. WARPEHA, Ministry of Health, Kingston, Jamaica, and E.D. BELTRÁN*, Division of Oral Health, CDC, Atlanta, GA, USA

Objective: to assess enamel fluorosis (EF) prevalence and severity in a potentially high risk population using a two-step assessment system. Jamaica has had salt fluoridation since 1987. Methods: In March-April 2000, 492 Jamaican school children (age 11-14 years) were visually screened by trained dental nurses for the presence of opacities consistent with EF in permanent teeth from upper right to upper left second bicuspids. Screenings were done using tongue depressors and flashlight. Presence of any fluorosis-like opacities in 2+ teeth was the inclusion criterion. In May 2001, children with opacities were reexamined by a trained dentist who recorded EF using Dean’s Index. All clinical assessments were done after consent and assent of parents and children. Additional data on F exposure from drinking water, F supplements, and F toothpaste were obtained via self-administered questionnaires completed by parents. The sample included children living in areas with natural F in two categories: higher F (HIF, n=254, median 0.21, mode 0.27) and lower F (LOF, n=58, median 0.13, mode 0.13). Results: Of 116 children with screened opacities, 96 were confirmed by dentist’s examination (82.8%), 7 were false positives (6%); 14 children were not available for reexamination. Overall EF prevalence in this non-representative sample was 20% (96/478) including the questionable category. Logistic modeling of any fluorosis identified two risk factors: natural F in water (LOF/HIF, OR=6.6, 95%CI: 1.5-28.8) and use of F supplements (OR=6.1, 95%CI: 1.9-20.3). EF was present among those drinking water with < 0.10 ppm F and no early childhood-recalled history of supplement use or toothpaste eating, suggesting a contribution of F in salt and/or insufficient control of F from multiple sources. Conclusion: In salt fluoridation programs, natural F in the water and supplement use increase the risk of EF.


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Fluorosis prevalence after an 11-month interruption in water fluoridation. B.A. BURT*1, M.A. KEELS2, K. HELLER3, and S. PAI1, 1 U-Michigan School of Public Health, Ann Arbor, USA, 2 Duke University Medical Center, Durham, NC, USA, 3 U-Iowa College of Dentistry, Iowa City, USA

Objectives: To assess the effects of an 11-month break in water fluoridation on fluorosis prevalence. Methods: The interruption to water fluoridation in Durham, NC, occurred between Sept. 1990 and Aug. 1991. A total of 1896 children were examined between Jan. 1996 and Feb. 2001. The children were 7-10 years old (mean=8.8) at the time of examination and were born between March 1985 and March 1992. Parents or guardians completed a questionnaire on demographics and fluoride history. Cohorts, defined by their age at the time of the break, ranged from those born 5 years beforehand (cohort 5), to those born 1 year after (cohort -1). Fluorosis was defined as a TF score of 1 or higher in at least one of the maxillary incisors. Results: Fluorosis prevalence for cohorts 5, 4, 3, 2, 1, 0, and -1 was 57.1, 62.3, 33.0, 32.3, 39.8, 30.2, and 36.8%, respectively. Logistic regression analysis showed that fluorosis prevalence in cohorts 4 and 5 was significantly higher than prevalence in the other cohorts. Toothbrushing twice or more per day and use of fluoride supplements were also significantly associated with fluorosis, though race, educational level, gender, and use of fluoride rinses, fluoride gels, and bottled water were not. Conclusions: Toothbrushing frequency, fluoride supplement use, and cohort effects were significantly associated with fluorosis. The 11-month non-exposure to fluoridated water seemed to reduce fluorosis in children aged from birth 3 years at the break, and in those born 1 year after it, when compared to those aged 4-5 years at the break. Supported by NIDCR grant DE-11240.


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Reporting the extent of dental fluorosis and enamel opacities using different indices. J. MCLOUGHLIN*1, J.J. CLARKSON1, and R. ALAYAHA2, 1 Trinity College, Dublin, Ireland, 2 Riyadh Armed Forces Hospital, Saudi Arabia

The Thylstrup and Fejerskov Index (TFI) is a commonly used fluorosis index, while the Modified Developmental Defects of Enamel index (DDE) is used to monitor all types of enamel defects. The DDE diffuse opacities score 2, includes all defects similar to fluorosis. These indices use different examining conditions, different numbers of index teeth, and compare different clinical appearances. Results are commonly reported as the number/percentage of subjects with at least one tooth affected by the different scores. Objectives: The aim of this study was to determine how a change in the reporting of the data from the TFI and DDE could provide information about the extent of fluorosis/opacities. Methods: Children (354) with a mean age of 12.5 years were examined for dental fluorosis/opacities using the TFI and DDE index by a trained and calibrated examiner (R A). All were lifetime residents in a fluoridated area (0.8-1.0ppm). Results: Using the TFI, 54.2% of subjects had at least one index tooth with a TF score of 1, while 51.7% of subjects had at least one index tooth with a DDE score of 2. When the numbers of teeth affected were analyzed for both indices, 77.1% of those with fluorosis (TF score 1), and 78% of those with TF 2 or 3 had 1-4 teeth affected. Of those with diffuse opacities (DDE score 2), 62.3% had 1-4 teeth affected. Statistical analysis of these results is difficult because of the different prevalence and the different numbers of index teeth. Conclusions: The extent of fluorosis/opacities diagnosed with TF and DDE was low, with the majority of subjects having between one and four index teeth affected. Reporting the extent as the number of index teeth affected by different levels of fluorosis/opacities, may be of value in assessing the public health impact of dental fluorosis and opacities.


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Impact of dental fluorosis on well-being in Mexico City children. A.E. SOTO-ROJAS*1, E.A. MARTÍNEZ-MIER2, G. MAUPOME3, and J.L. UREÑA-CIRETT1, 1 Universidad Intercontinental, Mexico City, Mexico, 2 Indiana University School of Dentistry, Indianapolis, USA, 3 Center for Health Research, Portland, OR, USA

Objective: To assess the relationship between dental fluorosis (DF) and esthetic perceptions that may affect well-being (WB) in children in Mexico City. Methods: Dental fluorosis (DF) may have an impact on personal WB because it affects appearance of teeth and face from an esthetic point of view. Using a questionnaire to measure DF impact on WB, 41 children ages 7 to 12 years attending a pediatric dental office were asked questions to (i) assess self-representation of psychological WB caused by perceptions of dental appearance, and (ii) differentiate among esthetic concerns derived from DF and other conditions (crowding, caries, periodontal disease). DF of anterior quadrant was evaluated using TSIF. Measures of WB were correlated to DF presence. Results: 66% and 81% of children reported experiencing at least occasionally distress or being worried, respectively, because of the appearance of teeth. 61% of the children stated the appearance hindered them from smiling freely, and 34% reported them as unsatisfactory. 59% reported their teeth were not straight and 20% believed they were unhealthy. 34% reported stains on their teeth compatible with DF; 66% had DF (TSIF >1); 63% had crowding of teeth. Unpleasant teeth color was reported by 20% of children. There was a significant correlation between DF and level of concern caused by dental appearance (p < 0.05). Conclusions: Children perceptions of DF appeared to have an impact on WB, as measured by a culturally appropriate research tool.


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Impact of dental fluorosis on well-being of children’s by their parent's perception in a pediatric dental practice in Mexico City. J.L. UREÑA-CIRETT*1, E.A. MARTÍNEZ-MIER2, G. MAUPOME3, and A.E. SOTO-ROJAS1, 1 Universidad Intercontinental, Mexico City, Mexico, 2 Indiana University School of Dentistry, Indianapolis, USA, 3 Center for Health Research, Portland, OR, USA

Objective: To assess the relationship between dental fluorosis (DF) and the esthetic perceptions of parents of the children who present it. Methods: Dental fluorosis may have an impact on personal well being (WB) because it affects appearance of teeth and face from an esthetic point of view. A questionnaire to measure impact of DF on WB was applied to parents of children ages 7 to 12 years that attended a pediatric dental practice. This included questions to assess self-representation of psychological WB caused by perceptions of dental appearance of their children and one question that differentiated among esthetic concerns derived from DF to conditions, such as, crowding, caries and periodontal disease. Front teeth were evaluated for DF using TSIF index. Parent’s answers to questions regarding their children’s WB were correlated with DF. Results: 28 parents answered the questionnaire, 32% and 82 % of the parents reported at least occasionally experiencing distress or being worried, respectively, because of the appearance of their children's teeth. 18% thought that it hindered their children from smiling freely, 54% reported crowding in their children’s teeth and 39%reported them as unsatisfactory. 39% reported presence of stains in children’s teeth, compatible with DF. 71% of children had DF (TSIF >1); 64% had crowding of teeth Unpleasant color of children’s teeth was reported by 11%. There was a significant correlation between presence of DF in the children’s teeth and parent’s reported concerns (p < 0.05). Conclusion: For this sample of parents who attend this practice, perceptions of DF in their children’s teeth appear to have an impact on their WB.


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Versions and perversions of the 'precautionary principle' in a contemporary fluoridation debate. P. BEIRNE*, Oral Health Research Centre, Cork, Ireland

“When an activity raises threats of harm to human health or the environment, precautionary measures should be taken even if some cause and effect relationships are not fully established scientifically.” This definition of the precautionary principle has generated considerable debate regarding its use as a decision making tool in situations where public policy decisions have to be made under conditions of scientific uncertainty. This debate has been complicated by the absence of a universal and widely accepted definition and interpretation of the principle. Aim: The purpose of this study is to examine the rhetoric surrounding the precautionary principle during the course of a contemporary fluoridation debate in Ireland and to identify how the principle has been defined and interpreted by groups opposed to water fluoridation. Methods: Qualitative documentary analysis of anti-fluoridation media including parliamentary questions, press releases, websites and anti-fluoridation literature. Qualitative Results: Explicit and implicit formulations of the precautionary principle would appear to suggest that the pursuit of ‘zero risk’ is desirable. In accordance with this goal opponents of fluoridation argue that the burden of proof should rest with those advocating this public health measure, who should ‘prove’ that fluoridation is ‘safe’. Interpretations are uniform in suggesting that an application of the precautionary principle is synonymous with the cessation of water fluoridation. Conclusions: The rhetoric deployed in the invocation of the precautionary principle implies a utopian goal of ‘zero risk’. It is suggested that, as interpreted by partisans, this principle does not provide a viable basis for the regulation of risk. The definitional ambiguity surrounding the precautionary principle should be resolved to prevent distortion of the meaning of this principle in environmental debates.


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Fluoride Concentration Variation Among Bottled Water Brands by Bottling Facilities. . E.J. STORHEIM*, and J.A. LALUMANDIER, Case Western Reserve University, Cleveland, OH, USA

Objective: Individual bottled water companies throughout the United States and Canada often utilize multiple water sources and bottling facilities which can lead to fluoride variation among the same brands of water. This project studies the variation in fluoride concentration of popular brands of bottled water according to their regional bottling facilities. Method: Using information from the Canadian Bottled Water Association, The Bottled Water Web, and labels on bottled water, a telephone survey was conducted. The survey inquired as to the number of water sources, the type of source, the fluoride concentration of each source, the addition of fluoride to any source, and the region supplied by each brand of bottled water. Results: While 137 bottled water companies were contacted, only 42 could or would respond to the phone interview. Of the 42 respondents, 18 indicated multiple sources and 24 reported a single source. Those bottlers using a single source reported 9 brands having non-detectable fluoride levels, 1 brand having fluoride added at a concentration of 1 mg/L, and the remaining varying in fluoride concentration from <0.1 to 1.4 mg/L. Among brands with multiple sources, 10 were reported to contain non-detectable fluoride levels, 2 had fluoride added at a concentration of 1 mg/L, and 6 had fluoride concentrations that varied by bottling facility. Conclusion: As families with children increasingly make bottled water their primary water source, it is imperative that they be made aware of the fluoride concentration in the bottled water they drink. While the variation in fluoride concentration within the same brand was minimal, the study did show that fluoride levels among bottled water companies are typically difficult to obtain, usually well below optimal levels, and only required to be posted on the label if fluoride has been added. The study was funded by Case Western Reserve University School of Dentistry, Cleveland, OH.


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Estimated Daily Fluoride Intake of 3- to 5-Year-Olds. S.M. LEVY*, J.J. WARREN, B. BROFFITT, M.J. KANELLIS, and J.S. WEFEL, University of Iowa, Iowa City, USA

Objectives: Dental fluorosis prevalence continues to be of concern to the Dental Public Health community, while our knowledge concerning fluoride intake of young children is incomplete. Combined fluoride intake from multiple sources has rarely been estimated. This paper reports on estimated daily fluoride intake from water by itself, other beverages, dentifrice, and dietary supplements, both individually and in combination, among children in the Iowa Fluoride Study when aged 3-5 years. Methods: Children had been recruited from 8 Iowa hospitals in 1992-95, with questionnaires (including food frequency assessment) sent at 4-6 month intervals. Results: Daily mean (SD) fluoride intake (in mg) estimates were: Water by itself: 36 mo. (n=563) - .15 (.18), 48 mo. (n=530) - .16 (.18), 60 mo. (n=570) - .19 (.22) Other beverages: 36 mo. - .26 (.20), 48 mo. - .25 (.25), 60 mo. - .24 (.21) Dentifrice: 36 mo. - .28 (.29), 48 mo. - .27 (.32), 60 mo. - .21 (.28) Supplements: 36 mo. - .02 (.08), 48 mo. - .02 (.10), 60 mo. - .02 (.10) Combined: 36 mo. - .70 (.42), 48 mo. – .70 (.47), 60 mo. - .66 (.43). Some individuals’ intakes greatly exceeded the mean level, as seen by the large standard deviations. Conclusions: Results suggest that daily mean fluoride intakes from individual sources and combined are relatively stable from 36 –60 months among these children, although there is great variation. Supported by NIH grants R01-DE09551, R01-DE12101, P30-DE10126, and CRC-RR00059, and bridging funds from the University of Iowa.


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Comparing longitudinal binary outcomes among non-randomized treatment groups in an observational oral health study. B.J. SHELTON*1, G.H. GILBERT1, P. BRADSHAW2, Z. LU, L.S. CHAVERS1, and G. HOWARD1, 1 University of Alabama at Birmingham, USA, 2 University of Florida, USA

Sample selection models have been proposed in the economics literature and more recently in the medical literature as a method to adjust for selection bias due to observed and unobserved confounders in observational studies. Application of these models has been limited to cross-sectional observational data and to outcomes that are continuous in nature. Objectives: In this paper we extend application of these models to include longitudinal studies and binary outcomes. Methods: We apply a probit-logit two-stage model using GEE to compare changes in presence of chewing difficulties measured every six months during a twenty-four month period between two groups of subjects; those either receiving or not receiving dental care services, which was measured at six month intervals as well. Results: Results from our proposed model are then compared to results using a standard GEE model that ignores the potential selection bias introduced by unobserved confounders. In this application, accounting for selection bias made a major difference in the substantive conclusions about the outcomes of interest. This is due in part to an adverse selection phenomenon in which those most in need of treatment (and consequently most likely to benefit from it) are actually the ones least likely to seek it. Conclusions: Our application of sample selection models to binary longitudinal observational outcome data should serve as impetus for increased utilization of this promising set of models in other health outcomes studies.


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Validity of specific self-reported dental treatments during a 48-month period: comparison with data from dental charts. G.H. GILBERT, J.S. ROSE*, and B.J. SHELTON, University of Alabama at Birmingham, USA

Health surveys are commonly used to measure self-reported dental visits, yet to our knowledge no longitudinal study of their validity in diverse populations has been done. Objectives: Following our report on validity of self-reported use of any dental care (JDR 2001; 80(spec. iss.): 267), our objective here was to quantify validity of specific self-reported dental treatments. Methods: Data were taken from the Florida Dental Care Study, an observational study of 873 dentate persons 45 years old or older. In-person interviews & clinical examinations were done at baseline, 24, and 48 months, with 6-monthly telephone interviews between those times. Participants reported any dental visits & treatment received. Information also was subsequently abstracted from dental charts. We calculated concordance between the self-reported measure of specific treatments (biopsy, dental extraction, root canal, removable prosthodontic procedure, fixed prosthodontic procedure, dental cleaning, dental filling, x-rays, fluoride application) in the previous 6-month interval, and the measure taken from the dental chart. Results: Concordance ranged from 72%-100%, coefficients of colligation ranged from 0.43-0.99, and kappa values ranged from 0.30-0.91. Parameter estimate intervals made from single bivariate multiple logistic regressions of treatment type (1 where the outcome was the self-reported measure, 1 where the measure was taken from the dental chart) over-lapped between the self-reported and chart measures for each of 4 predictors for all 9 treatment types, although conclusions about statistical significance of 1 predictor did differ for 3 treatment types. Conclusions: The validity of self-reported dental treatments was fair to excellent, depending upon the specific treatment. There would have been few differences in conclusions made about predictors of specific treatments had chart data been available earlier.


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Assessing the Validity of Partial Site Measurements of Probing Depth and Attachment Loss. V.W. SPOLSKY*, M. MARCUS, and N. GUZMÁN-BECERRA, University of California, Los Angeles, USA

Objective: The purpose of this pilot study is to examine the relationship between full mouth probing depth (PD) and attachment loss (AL) measurements at six sites per tooth compared to lesser numbers of sites per tooth and to assess the degree of bias that occurs in using varying combinations of sites per tooth. A previous study examined only attachment loss. Methods: A convenience sample of 22 adults with minimum of 20 teeth, no prophylaxis during previous 12 months, age 30 to 72 (mean 41.9, ±2.7) and predominantly male (16M/6F) was used. The NIDCR (Miller et al 1987) diagnostic criteria and instruments were used to conduct full mouth examinations at six sites per tooth including the two sites used by the NIDCR. Paired t-test and regression analysis were used to compare probing depth at 6 sites per tooth to five partial site combinations. Results: Mean differences (paired t-test) showed that one of the partial site measures slightly underestimated the severity of PD compared with 6 sites per tooth, two partial sites did not show any statistically significant difference, and two partial site measures slightly overestimated PD (range: -9.0% to +12.2%). Using multivariate linear regression, the 4-site measure (p <.001), the 1-site measure (p <.05) and the 2-site measure (p <.05) were the best predictors of the six site measures of PD (adj. R2=0.9920). When probing depth and attachment loss are equal to 3 mm, the two 3-site measures (-1.3% and 1.6%) and 2-site measures (-9.7%) produced a negative bias for PD and AL severity. The 1-site (+3.9%) and 4-sites measures (+9.4%) were positively biased. Conclusions: The use of partial site measurements per tooth of probing depth and attachment loss to estimate the prevalence and severity of periodontal disease requires analysis of the systematic errors that occur. This study was funded by the International Center for Dental Health Policy.


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Controlling for the endogeneity of WIC on dental services use. J.Y. LEE*, R.G. ROZIER, W.F. VANN, and E.C. NORTON, University of North Carolina at Chapel Hill, USA

When a randomized controlled trial is not possible, researchers must control for nonrandom assignment to experimental groups, or estimates of the treatment effect can be biased. One technique to adjust statistically for the nonrandom assignment is called instrumental variables (IVs). Although this technique has become quite common in health services research, it rarely is used in dental research. IVs rely upon the existence of one or more variables that induce variation in the main explanatory variable, but have no direct effect on the outcome. Objective: The purpose of this study is to apply the IV technique and two-stage methodology to test and control for selection bias in examining the effects of the Women, Infants and Children's (WIC) program on dental services use by pre-school aged children enrolled in Medicaid. Methods: An analysis file was constructed of 49,512 children ages 1-5 years using five data sources (birth records, Medicaid eligibility and claims files, the WIC masterfile and the Area Resource File). They were chosen from a cohort born in 1992 and an annual file was created up to their fifth birthday. Instrumental variables (#WIC clinics, #WIC workers, #WIC hours) were used to control for WIC participation, the potentially endogenous explanatory variable. Random effects panel data techniques and two part models were used in the analyses. Results: Five specification tests showed that WIC participation was endogenous and that the instruments were valid. The effects of WIC on dental use differed after incorporation of IVs. Conclusion: This study shows that instrumental variable techniques can be used to control for potential selection bias in dental outcomes research when randomization is not possible. Supported by MCH Grant # 5 T17 MC 00015-10, AHRQ grants T32-HS-00032 and RO3-HS11607-01.


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Beyond weighted kappa when evaluating examiner agreement for ordinal responses. A. KINGMAN*, NIDCR, NIH, Bethesda, MD, USA

Weighted kappa statistics (restricted and unrestricted linear weights, ICC or squared error weights) are commonly reported for ordinally scaled variables. Although intended to measure agreement these weighted kappas really assess association and agreement, whereas model-based approaches can be useful in measuring association separately from agreement. One can model agreement structure directly by evaluating symmetry, linear association beyond agreement, and marginal homogeneity. For response variables in which the first level represents "no disease" and the remaining categories various gradations of disease, modifications need to be made in these models. Objective: In this study weighted kappas and several modeling approaches are compared and evaluated from the perspective of the effect of examiner disagreement on estimates of disease prevalence or severity and their standard errors, as the structure of diagnostic disagreements can be paramount. Methods: Exact agreement parameters for "no disease" and "gradations of disease" were included in the modeling approaches. Hypothetical gingivitis data (Loe-Silness index with 4 levels) and fluorosis (Dean's index with 6 categories) were generated and modeled and evaluated for examiner agreement and the effect on estimates of disease prevalence and severity and their standard errors. Graphical methods illustrating potential bias (lack of symmetry) and loss of precision. Results: Large values for weighted kappa do not insure high examiner agreement or comparability in prevalence estimates of disease. Significant asymmetry in diagnostic scores can produce biased estimates whereas substantial levels of symmetric disagreements inflate the standard errors. Conclusions: Weighted kappa statistics are very useful summaries for ordinal responses but need to be complemented by specific measures of examiner disagreement structure. Graphical methods illustrating asymmetry and loss of precision are useful to pinpoint specific problem areas of examiner disagreement.


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Statistical methods applied to oral health researches related to intraobserver agreement. L.C.M. LOFFREDO*1, G. SCAF1, and J.M.P. SOUZA2, 1 UNESP- Araraquara Dental School, Brazil, 2 USP- School of Public Health, São Paulo, Brazil

Statistical methods applied to oral health researches related to intraobserver agreement.

L.C.M. LOFFREDO, G. SCAF, J.M.P.SOUZA

In clinical research, statistical methods are used to determine the biological variability, in subject and in measurement method which may lead to error. The observer could show variation in replicate readings by measuring each radiography of a sample more than once. Objective: the aim of this study was to quantify the measurement error, applying three different statistical Methods: Dahlberg error (D), Student t-test (t) and intraclass correlation coefficient (icc). Methods: the sample was composed of 30 periapical radiographs and it was obtained the measurements (in mm) from the tip of the file to the radiographic apex, in two different occasions, by the same examiner. Results: the results showed that was no-significant difference in the two measurements, assessed by D=0.0188 mm, t=-0.70 (p< 0.01) and icc=0.98. Although the three statistical methods showed that the readings were not differents, the use of intraclass coefficient correlation is more indicated than the others. The idea is to plot the data as a scatter diagram, and if the points lie along the line of equality, we have perfect agreement. The intraclass correlation coefficient between pair of readings doesn´t take into account the order in which the observations were taken, comparing each pair of data.While t- Student test and Dahlberg error use the comparison of means of readings in each occasion, they could be used just to compare these means. Conclusion: the conclusion is that the intraobserver agreement is verified when the difference between observations on the same subject is small enough to use the first or the second reading interchangeably and the intraclass correlation coefficient is more indicated than the others for measuring the reliability of quantitative scales in oral health researches. Financial Support: CNPq 300952/94-5


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Non-Inferiority Trials: the "At Least As Good As" Criterion. L.L. LASTER*, University of Pennsylvania, Philadelphia, USA, and M.F. JOHNSON, PharmaNet, Inc, Princeton, NJ, USA

Objectives: To demonstrate in a clinical trial a new or experimental therapy (et) is at least as good as a standard therapy (st), a statistical test or confidence interval must rule out clinical inferiority with a high probability. Methods: The term at least as good as implies equivalent but not necessarily superior efficacy. It is statistically impossible to demonstrate equivalence (i.e., prove the null hypothesis of no difference). Blackwelder proposed a one-sided significance test to reject the null hypothesis that st is better than et by a clinically acceptable amount d. Blackwelder's approach is redefined in terms of the ratio of two means (RTrue=met / mst) based on a continuous variate with higher values denoting greater improvement. Ratio-based equivalents to Blackwelder's hypotheses are shown. Studies can be sized with high probability to show experimental therapy is at least (RLB*100)% as effective as the standard therapy, where RLB is the lower bound on the percentage effectiveness. Results: For typical at least as good as applications (when RLB < RTrue £ 1), the ratio formatted test of Ho: RTrue £ RLB is shown to be more efficient than Blackwelder's test of Ho: mst - met ³ d , thereby requiring smaller sample sizes to detect the directionally based non-null alternatives contained in H1: met / mst > RLB. When RTrue=1.0, tests of Blackwelder's hypotheses, their ratio-based equivalents and conventional superiority can be evaluated for comparative efficiency. Conclusions: Testing Ho: RTrue £ RLB with single-sided critical region of size a, versus H1: RTrue > RLB, is shown to be more efficient than excluding RLB from the lower limit of a 100(1- 2a )% two-sided symmetric confidence interval centered by estimated R. Examples are presented.


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Socioeconomic status ladder to assess perceived overall and oral health. S.A. GANSKY*1, S.E. SINISI2, P.B. CRAWFORD2, and O. PLESH1, 1 University of California, San Francisco, USA, 2 University of California, Berkeley, USA

Research has recognized health disparities exist along a socioeconomic status (SES) gradient. An ordinal SES scale (the MacArthur Subjective Status Scale (MacStatus); e. g. Adler et al., 2000) is a gestalt SES measure. Objective: The report examines the relationship between the MacStatus Ladder, other more traditional SES measures, and perceived oral and overall health ratings. Methods: In an ongoing study of community dwelling young women (N=284: 53% African-American and 47% Caucasian, currently 22-24 years old) from the NHLBI Growth and Health Study (NGHS) in Contra Costa County, California and Cincinnati, Ohio structured interviews including items about perceived overall and oral health (5 point ordinal scales: poor-excellent), education level, student status, and the MacStatus Ladder (with 10 rungs) were administered. Household income and maximum parental education at baseline of the NGHS (participants were ages 9-10) were also used as SES measures. Results: Participant education was related to overall health (partial Spearman correlation adjusting for center (rs|c)=.18, p=.006); parental education (rs|c=.13, p=.030), household income (rs|c=.16, p=.008), and participant education level (rs|c=.19, p=.004) were related to oral health. Although participant education level was the only SES variable significantly associated with MacStatus (rs|c=.24, p<.001), MacStatus was significantly related to overall (rs|c=.24, p<.001) and oral health (rs|c=.18, p=.003). Additionally, a difference in these relationships between races was noted. Among Caucasians, MacStatus was related to overall (rs|c=.21, p=.015), but not oral health (rs|c=.14, p=.140); education was related to both overall (rs|c=.23, p=.016) and oral health (rs|c=.24, p=.010). Among African-Americans, MacStatus was related to overall (rs|c=.26, p=.001) as well as oral health (rs|c=.22, p=.008); only parental education was related to oral health (rs|c=.22, p=.007). Conclusions: The MacStatus Ladder is significantly related to overall health status rating and, in young African-American women, oral health status - better than more traditional SES measures.


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"Correlationship Between Stages of Calcification of Mandibular Cuspids and Second Bicuspids with the Maxillary and Mandibular Puberal Growth Curve". R. VALVERDE*, M. ADRIAZOLA, F. WILLIAMS, A. MENESES, O. TUESTA, and E. MORZAN, Universidad Peruana Cayetano Heredia, Lima, Peru

The determination of the peak of high velocity of maxillary and mandibular growth has singular importance in orthodontic treatment. The effects in Class II division 1 malocclusion treatment using mandibular propulsors or extraoral appliances with the purpose of directing the maxillary growth are higher during the puberal growth peak. OBJECTIVE The present study tries to determinate the degree of correlation between the stages of calcification of mandibular cuspid and second bicuspid purposed by Demirjian with the maxillary and mandibular puberal growth curve purposed by Fishman. METHOD The sample calculated at a level of significance of 99.99% (p<0.001) consisted of a set of panoramic and wrist radiographs (100 females, 54.64% and 83 males 45.36%) taken the same day. The sample was subdivided according to genus and the side to which each tooth annalysed belonged. Pearson correlation index was used to determine the correlation degree between both events, chi Square test for sexual dimorphism and tables of frecuency distribution were made to see the distribution of the Stages of Fishman in the Stages of Dental Calcification purposed by Demirjian. RESULTS The correlation founded was of a high significance in all cases, the higher correlation due to Fishman was found in the right second bicuspid (0.882) and the lowest correlation was for the right cuspid (0.832), the higher correlation due dental calcification was given between the bicuspids of both sides (0.995). No sexual dimorphism or significative differences was found in our results. In women the stage 6 of Fishman (high peak of puberal growth for females) was coincident in 86.48% with the "G" stage of dental calcification purposed by Demirjian. In men the stage 7 of Fishman (high peak of puberal growth for males) was coincident in 98.21% with the "G" stage of dental calcification.


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The impact of caries experience in primary molars on the emergence of their successors. R. LEROY*1, K. BOGAERTS, E. LESAFFRE, and D. DECLERCK4, 1 Catholic University Leuven, Belgium, 2 Catholic University of Leuven, Belgium, Belgium

Objectives: In the literature there is no consensus on the influence of a history of caries in the primary dentition on the emergence of the permanent dentition. The aim of the present study was twofold: 1) to analyze whether the emergence of the successors of deciduous molars with a history of caries was delayed or advanced and 2) to evaluate whether the successors of primary molars extracted due to caries emerge at an earlier or later age. Methods: For this purpose data available from the Signal Tandmobiel® project were used. In this longitudinal epidemiological survey data were collected from a representative sample of more than 5000 children (born in 1989), examined yearly (between 7 and 12 years of age) by trained dentist-examiners. Caries experience and tooth emergence were recorded by direct inspection. Log-logistic survival analyses were performed to calculate median emergence ages. Results: 56% of all examined primary molars were sound (i.e. dmft=0). Between 2.5 and 7.2% of the first and second primary molars were extracted due to caries; the prevalence of extractions was higher in the mandible compared to the maxilla. The analysis indicated significantly later emergence ages for premolars with sound primary predecessors. The observed differences ranged between 2.4 and 4.8 months in girls and between 3.6 and 8.4 months in boys. In the maxilla, the emergence of premolars replacing deciduous molars extracted due to caries, was advanced significantly (p<0.0001); for the mandibular premolars no significant differences could be observed. Conclusion: a history of caries in the primary molars is associated with an advanced emergence of the permanent successors. (Supported by Unilever, Belgium – Research Grant OT/00/35, Catholic University Leuven.)


1659 (17599)

Patterns in congenital hypodontia. J. KWONG*, M. VALIATHAN, H.K. TIWARI, R.C. ELSTON, and M.G. HANS, Case Western Reserve University, Cleveland, OH, USA

Interest in the area of congenital hypodontia has grown in the last few years. Objectives: The present study was designed to evaluate patterns in congenital hypodontia (excluding third molars). Methods: The population consisted of patients from the Case Western Reserve University, Department of Orthodontics and a private orthodontic practice. A total of 2619 individuals, comprising 1174 males, 1445 females, 2111 Caucasians, 313 African Americans, and 195 persons of other ethnic backgrounds were examined using existing, pre-treatment panoramic radiographs. Missing teeth were denoted using the Universal numbering system and the data were entered in Excel as a dichotomous variable. The ascertained sample of 201 subjects with hypodontia consisted of 110 females, 91 males, 164 Caucasians, 26 African Americans, and 11 subjects of other ethnic origins. Pair-wise correlations were estimated for each missing tooth and other teeth using SPSS. Results: The analysis yielded significant (p-value < 0.01) correlations between missing # 12 and # 22 (0.579), # 15 and # 25 (0.688), and # 35 and # 45 (0.440). In addition, the Caucasian sample alone exhibited a significant (p-value < 0.05) correlation between tooth # 15 and # 35 (0.191), and tooth # 15 and # 45 (0.191). Similar overall trends were observed in males and females. Conclusions: These results indicate a strong association between congenital hypodontia of teeth and the corresponding contra-lateral teeth. Supported by the Department of Orthodontics and the American Association of Orthodontists Foundation.


1660 (18666)

Sexual dimorphism in tooth crown size of permanent dentition in Indonesian. R. PUSPITAWATI*, H. WIDODO, and M. JUNIASTUTI, Univ. of Indonesia, Jakarta, Indonesia

Objective: There were various data of tooth crown size and sexual dimorphism in tooth crown size among different population. Therefore, the objective of this study was to obtain data of sexual dimorphism in tooth crown size of permanent dentition in Indonesian lived in Jakarta.

Methods: The study sample consisted of 113 pairs of dental casts of 113 Indonesian children (56 females and 57 males) aged 15 to 16 years who lived in Jakarta. The measurement of the mesio-distal and bucco-lingual diameters of the crown was conducted on the study models for all teeth except for the second and third molars. There were no significant differences in tooth crown diameters between left and tight side of the dental arches (p > 0,05). Therefore, the measurements of the teeth from both right and left sides were used to represent the tooth crown size in this study. In so forth the data gained in this study consisted of 112 and 114 measurements for female and male sample respectively (for each mesio-distal and bucco-lingual measurement).

Results: With the exception of maxillary second premolar and first molar and mandibular first and second incisives, there were significant sexual dimorphism in mesio-distal and bucco-lingual tooth crown diameters where the male’s was bigger than the female’s (p < 0,05). The teeth showed greatest sexual dimorphism were canines for the mesio-distal diameter and mandibular first premolars for bucco-lingual diameter.

Conclusion: Similar as in other population previously studied, in Indonesian lived in Jakarta the tooth crown diameter was bigger in male than in female and canine showed the greatest sexual dimorphism. However, there were differences in sexual dimorphism in tooth crown size of Indonesian compared to other population and among different teeth.


1661 (20477)

Analysis of Maxillo-Dental Protrusion in Black and White Females. E.R. RICHARDSON*, and S.K. MALHOTRA, Meharry Medical College, Nashville, TN, USA

The facial profile of Black and White females is similar except for the nose and mid-face protrusion. The objective of this study was to analyze some parts of the face of Black and White females to look for similarities and differences. Materials and Methods. Annual lateral cephalograms of 41 Black females were available. There were 11 cephalograms on each person whose ages were 6 to 16 years. Both angular and linear measurements were made and analyzed, i.e., angular (somatic) S-N-Ba, S-N-ANS, S-N-Pg, (dento-alveolar) S-N-A, S-N-B. Linear measurements, S-N, PNS -ANS, PNS-Upper incisor Edge (UIE) and GO-pg. A two sample t-test was used to compare the measurements with those of a White sample from Ann Arbor by Riolo et al. We analyzed the compensating interrelationship of parts. RESULTS. The differences in the angles S-N-ANS and S-N-Pg and linear distances S -N and PNS-ANS were not statistically significant. The angles S-N-A, S-N-B and S-N-Ba were larger in Blacks as were linear distance PNS-UIE and GO-Pg. Conclusions: There are significant differences in some parts contributing to the make up of the facial profile. S-N-Ba and S-N may play a compensating role which helps offset the larger GO-Pg. Further study is indicated. Supported in part of USPH Grant DE02862.


1662 (21580)

The axial inclination of maxillary incisors as a predictor of crown-root angulation (Collum angle). T. EL-BIALY*, and S. GABALLA, Tanta University, Egypt

Previous research has shown that crown-root angulation is different in Class II Division 2 malocclusion cases. Objectives: The objective of this study was to test if there is correlation between the skeletodental pattern in patients with Class II Division 2 cases and Collum angle. Methods: Records of twenty patients having Class II division 2 malocclusion and same records of other twenty normal subjects with accepted occlusion and of comparable age range were taken. The records included study casts and lateral cephalometric radiographs. Lateral cephalometric radiographs were traced and corrected for magnification distortion. Model analysis included overbite, arch length analysis and Bolton analysis. Lateral cephalometric analysis included fifteen linear and angular measurements. Results: There was significant increase in the collum angle in Class II div. 2 cases compared to the controls (p<0.05). The axial inclination of the maxillary incisors to palatal plane, Frankfort Horizontal plane, and to the anterior cranial base (SN) showed high positive correlations to the Collum angle (p<0.05). Conclusions: Collum angle in Class II division 2 malocclusion cases was increased which can be attributed to the skeletal pattern of theses cases. Also, axial inclination of the maxillary incisors can be used as a predictor of the crown/root angulation of the maxillary incisors.


1663 (21611)

The etiology of palatally displaced canines; the evidence examined. A. MOULLAS, M. VALIATHAN*, H.K. TIWARI, and R.C. ELSTON, Case Western Reserve University, Cleveland, OH, USA

The genetic basis of craniofacial-oro-dental phenotypes has generated much interest in recent years. A familial inheritance pattern and a genetic basis has been hypothesized in the etiology of palatally displaced canines. Objective: To use a genetic epidemiology approach to estimate the familial correlations of palatally displaced canines and hence determine whether genetic and/or common environment and cultural influences are present. Methods: Thirty-five previously published pedigrees (Pirinen et. al., 1996) were entered in Excel as a dichotomous trait. The families had been singly ascertained. Data were analyzed using FCOR2 in the Statistical Analysis of Genetic Epidemiology Software (S.A.G.E). This package calculates the familial correlations of binary traits without assuming the trait is normally distributed. Results: All three familial correlations were found to be negative and non-significant; Spousal correlation was -0.0560, Parent-Offspring Correlation was -0.0518 and Sib-Sib correlation was -0.1160. Lack of affected pairs in the sample could have contributed, in part, to the non-significant correlations found. Conclusions: The data set examined does not suggest a genetic or common environmental contribution to the phenotype and, while both the genetic hypothesis and guidance theory of PDC may have merit, either could be considered credible etiologies till further information is available. Supported by the Department of Orthodontics and the American Association of Orthodontists Foundation.


1664 (14662)

Differences in Tooth Dimension Measurements Between Study Models, Periapical X-Rays, and Panoramic X-Rays. S. CARLSON*, S. BAUMRIND, R. BOYD, S. CHONG, and L. WALKER, University of the Pacific School of Dentistry, San Francisco, CA, USA

Objective: Empirical evidence suggests that periapical x-rays are more valid than panoramic x-rays in measuring tooth dimensions. Quantitative values of their difference have yet to be reported. A better understanding of the quantitative differences may allow similarly useful information to be gathered with reduced radiation. Methods: Measurements were made of mandibular right posterior teeth on 16 sets of study models, periapical x-rays, and panoramic x-rays. X-rays were taken on the same day by the same technician. Tooth landmarks were located on each x-ray by three independent judges and their averaged estimate was used. Tooth width was measured on study casts using digital calipers. The following comparisons were made: 1) Tooth width – study models vs. periapical x-rays. 2) Tooth width – study models vs. panoramic x-rays. 3) Tooth width – periapical x-rays vs. panoramic x-rays. 4) Tooth length – periapical x-rays vs. panoramic x-ray. Clinical significance was defined as a difference >0.5 mm for width and >1.0 mm for the length. Statistical significance was defined as p£ 0.05. Results: Differences between all canine measurements were not clinically or statistically significant. Differences between periapical first and second bicuspid width measurements were not clinically or statistically significant from the study models. All other bicuspid comparisons were significantly different. Differences between all first and second molar measurements were clinically and statistically significant. Enlargement of panoramic tooth measurements tended to increase gradually toward the posterior. Conclusions: Periapical x-rays showed mildly greater validity than panoramic x-rays. This data suggests that estimates of tooth size can be made from panoramic x-rays using average enlargement values, thus allowing clinicians to acquire useful information with reduced radiation.


1665 (11603)

The role of sutures in frontofacial growth: Evidence from the metopic suture. L. COBAIN*, S. NABIPOUR, and G. RICHARDS, University of the Pacific, School of Dentistry, San Francisco, CA, USA

Objectives: The life-history of the metopic suture presents a unique opportunity to investigate the role of sutures in craniofacial growth. Firstly, the metopic suture differs from other neurocranial sutures by spanning the neural and facial skull and by its, normally expressed, early fusion. Secondly, sutural obliteration in early postnatal stages raises questions about the role of sutures in neurocranial expansion and about the rate of intramembranous bone growth in this process. To delineate this sutures life-history and address the above questions we compiled a sample of 128 infants with developmental ages ranging from late fetal/new born to 3.0 years-of-age. Methods: We measured 11 dimensions of the frontofacial region and quantified the fusion sequence of the suture. Results: We found that the metopic suture begins its closure sequence endocranially in the mid-frontal region with ossification proceeding ectocranially and then posterosuperiorly and anteroinferiorly from this point. We recorded this fusion sequence in 28.5, 42.9, and 79.0% of infants aged as late fetal/new born, 0.5 years, and 0.75 years-of-age, respectively. Sutural fusion coincided with rapid expansion of the frontal. We also found that maximum and minimum frontal breadth increase equally during this period of sutural fusion. Conclusions: (1) the suture presents with a wide age range for the initiation of fusion; (2) in many individuals the metopic suture normally becomes functionally fused at or near birth; (3) cranial shape does not appear to modify the initial location or sequence of sutural obliteration; (4) sutural fusion does not appear to affect normal lateral cranial expansion; and (5) remodeling rates in intramembranous bone can be very high, most probably equaling those found in endochondral bones of the cranium.


1666 (11579)

NELL-1, a CBFA-1 Modulated Gene, Simulates Human Craniosynostosis. X. ZHANG*, Y.P. MIAO, H.-F. LEE, C. SOO, and K. TING, UCLA, Los Angeles, CA, USA

Previously, we reported we report the recreation of congenital human Craniosynostosis (CS) phenotypes without extra-cranial deformities in transgenic mice with NELL-1 over-expression. CS phenotypes in NELL-1 transgenic mice ranged from compound synostoses such as craniotelencephalic dysplasia to simple synostoses. In vitro, NELL-1 over-expression promoted calvarial osteoblast differentiation and mineralization, and concomitantly altered bone differentiation marker and growth factor expression. The objective of this study is to investigate the interaction of NELL-1 with known CS candidate genes like FGF/FGFRs in premature suture closure. Methods: Analysis of the potential NELL-1 promoter region was performed. CBFA-1 was transfected into calvarial osteoblasts Administration of exogenous TFG-ß1, FGF2, IGF1 & 2, BMP2, VEGF, and PDGF to calvarial osteoblasts to examine the expression NELL-1. Results:. Promoter region showed a well-conserved CBDA-1 (runt family) binding site, OSE2 with a core sequence AACCACA. Transfection with CBFA-1 induced NELL-1 expression. Only TFG-ß1 and FGF2 increased NELL-1 expression. CONCLUSION: Mechanistically, CBFA-1, which regulates the commitment of mesenchymal cells to the osteoblast lineage, has been strongly associated with FGF2/FGFR1 models of CS development. Both FGF2 and TGF-ß1 are known to induce or modulate CBFA-1 expression, respectively. We postulate that because NELL-1 is regulated by CBFA-1, which in turn is regulated by FGFR1 and possibly TGF-ß, NELL-1 may be a common denominator in FGF- and TGF-ß-dependent pathways for premature suture closure as an osteoblast-specific, down-stream effector. Mechanistically, NELL-1 induces suture closure by promoting calvarial bone formation. Supported by NIH K23 DE00422, AAOF, and CRC/NIH RR00865.


1667 (14203)

Negative Transcriptional Regulation of Connexin 43 by Tbx2 in Osteoblast-like Cells and Developing Rat Coronal Sutures. J.L. BORKE*1, J.C. YU1, C.M. ISALES1, R.J. BOLLAG1, M.F. ORELLANA1, and J.-R. CHEN2, 1 Medical College of Georgia, Augusta, USA, 2 National Cheng Kung University, Tainan, Taiwan

Tbx2 is a member of the T-box family of transcriptional regulatory genes with an extensive but not yet fully understood role in embryonic development.  The importance of the T-box gene family is suggested by its evolutionary conservation across species, and is manifest by the recent discoveries that mutations in certain T-box genes play a role in three human developmental syndromes, ulnarmammary syndrome, Holt-Oram syndrome, and DiGeorge syndrome.  Our study suggests a role for Tbx2 in calvarial morphogenesis through its relationship to connexin 43 (Cx43) a protein necessary for cell-to-cell communication.  Objective: We explore the hypothesis that Tbx2 participates in the formation and structural equilibrium of the cranium by a negative regulatory effect on the expression of Cx43.  Methods:  An osteoblast-like cell line ROS 17/2.8 was transiently transfected with sense or antisense Tbx2. Immunohistochemistry and Western blot analysis were used to study TBX2 and Cx43 expression in these cells and in sections of embedded developing rat coronal sutures.  Results: The cells transfected with antisense Tbx2 show a decrease in expression of TBX2 protein, and an increase in expression of endogenous Cx43.  The reverse is seen with sense tranfected cells.   The expression pattern of TBX2 in the developing coronal sutures is also reciprocal to the expression of Cx43.  TBX2 protein is concentrated in the center of the sutural blastema, an area devoid of Cx43 protein localization.  Conversely, TBX2 protein expression is low in the periphery of the sutures, where there is high Cx43 protein expression.  Conclusions:  Taken together, these studies suggest that Tbx2 is a negative regulator of Cx43 expression at the transcriptional level in bone cells and cranial sutures in vivo. Supported by NIH/NIDCR DE12812 (JLB).

 


1668 (21127)

Msx2 is required for downregulation of M-Twist in sagittal sutures. Y.-L. YEA*, W. WANG, and M.A. IGNELZI, Jr., University of Michigan, School of Dentistry, Ann Arbor, USA

Craniosynostosis, defined as a premature fusion of calvarial bones at the sutures, is a common and significant birth defect. The flat bones that comprise the top of the skull, or calvaria, are most often affected and craniosynostosis is a feature of over 100 human syndromes and conditions. Mutations in human Fibroblast Growth Factor Receptors 1, 2 and 3 and the transcription factors MSX2 and TWIST lead to craniosynostosis. We have previously shown that FGF2 soaked beads placed on wild type mouse calvaria leads to increased Msx2 expression, decreased M-Twist expression, and fusion of sutures. Objective: The purpose of this study was to determine if an epistatic relationship exists between FGF receptors, M-Twist and Msx2. Methods: FGF2 was delivered to wild type and Msx2-/- fetal day 18.5 calvaria using heparin acrylic beads. Calvaria were cultured in serum free media for 48 hours, RNA was harvested, and M-Twist expression was quantitated using RT-PCR ELISA. Differences were determined using Student’s t-test. Results: In wild type sagittal sutures, M-Twist expression decreased following FGF2 treatment compared to bead only and no bead controls (p<0.001). Interestingly, Msx2-/- sagittal sutures did not exhibit decreased expression of M-Twist following FGF2 treatment (p<0.001). Conclusion: These results suggest that Msx2 is required for the downregulation of M-Twist by FGF2. These data are consistent with the hypothesis that FGF2, Msx2 and M-Twist share common pathways in calvarial sutures.


1669 (18324)

Elevated TGF-b1, TGF-b2, TGF-b3 and Msx2 expression are associated with morphogenesis of facial sutures and active bone growth from these sites. K. ADAB*1, J.R. SAYNE2, D.S. CARLSON2, and L.A. OPPERMAN2, 1 Harvard School of Dental Medicine, Boston, MA, USA, 2 Texas A&M University System Health Science Center, Dallas, USA

TGF-b1, TGF-b2 and TGF-b3 and Msx-2 have been shown to regulate cranial suture formation and maintenance of patency. While TGF-b3 rescues cranial sutures from obliteration (Opperman et al., 2000; Cooper et al., 2001), TGF-b2 induces these sutures to fuse (Opperman et al., 2000). These factors have been linked with in-utero constraint-induced craniosynostosis (Hunenks et al. 2001), while mutations in MSX2 have been associated with Boston-type craniosynostosis (Jabs et al. 1993). Objectives: In this study, the hypothesis to be tested was that these factors have similar roles and distributions in the facial sutures during morphogenesis and postnatal growth. Methods: mRNA and protein expression patterns of TGF-b 1, TGF-b 2 and TGF-b 3 and Msx2 were examined in vivo during development and postnatal growth of the frontonasal (FN) and transpalatal (TP) sutures of the rat, using polymerase chain reaction (PCR) and imunohistochemical techniques. Results: PCR amplification of TGF-b2 and TGF-b3 identified two peaks of mRNA expression, one at embryonic days 18-20 (E18-20) and another at postnatal days 2-5 (P2-5). Immunolocalization of TGF-b1 and TGF-b3 proteins showed immunoreactivity in both cells and matrix of the sutures, while TGF-b2 was mainly detected in the osteoblasts lining the bone fronts. Two peaks of protein immunoreactivity were detected, one from E18-birth and another at P11-P15. Msx2 gene expression in both sutures showed two peaks, at E20 and P2-P5. The peaks and declines in Msx2 mRNA expression closely follow those in TGF-b2 and TGF-b3 mRNA expression, which precede by 1-2 days the peaks and declines of TGF-b1 and TGF-b3 protein expression. Conclusion: Importantly, the peaks of TGF-b protein expression coincide with the stages of active suture morphogenesis (bone overlap) and of active bone growth from the sutures postnatally. Interestingly, the TP suture, which is developmentally ahead of FN sutures, exhibits its peak earlier than FN sutures. This research is supported by grant NIH DE11978.


1670 (14596)

Inhibition of Postoperative Resynostosis With Anti-TGF-b 2 Antibody in Craniosynostotic Rabbits. M.P. MOONEY*1, H.W. LOSKEN1, A. MOURSI2, R. MITCHELL1, P. WINNARD2, O. OZERDEM1, J. BRADLEY1, K. AZARI1, O. ACARTURK1, T. CHANG1, L.A. OPPERMAN3, E. STELNICKI4, M.I. SIEGEL1, and . 5, 1 University of Pittsburgh, PA, USA, 2 Ohio State University, USA, 3 Baylor College of Dentistry, USA, 4 Cleveland Clinic, Miami FL, USA, 5 USA

Objectives: Recent studies have shown that developmental changes in the expression of the various Transforming Growth Factor-b (TGF-b ) isoforms control normal cranial suture formation, maintenance, and fusion. It has been suggested that an over-expression of TGF-b 2 causes craniosynostosis and postoperative resynostosis. Interference with TGF-b 2 production and/or function may prevent postoperative resynostosis. The present study was designed to test this hypothesis in a craniosynostotic rabbit model.

Methods: To date, 15 New Zealand white rabbits with coronal suture synostosis have been divided into 3 groups: 1) Suturectomy controls (n=6); 2) Suturectomy with non specific, control IgG antibody in a slow release collagen vehicle, (n=4); and 3) Suturectomy with anti-TGF-b 2 antibody in a slow release collagen vehicle (n=5). At 10 days of age, a 3mm x 10mm coronal suturectomy was performed in all rabbits. The sites in Groups 2 and 3 were immediately filled with 0.1cc of a slow resorbing (90-180 day), collagen gel mixed with either IgG antibody (100ug/suture) or anti-TGF-b 2 antibody (100ug/suture). Serial 3D-CT scan reconstructions of the defects were obtained at 10, 25, 42, and 84 days of age and the sutures were then harvested for histomorphometric analysis.

Results: Preliminary analysis of the 3D-CT scan data revealed that the sites which were treated with anti-TGF-b 2 antibody showed significantly (p<0.05) greater defect areas through 84 days of age compared to untreated and IgG control rabbits. Qualitative histological examination also showed that defects treated with anti-TGF-b 2 antibodies had patent suturectomy sites and more fibrous tissue in the defects when compared to control rabbits.

Conclusions: These preliminary data support our initial hypothesis that interference with TGF-b 2 production and/or function may prevent postoperative resynostosis These findings also suggest that this cytokine therapy may have potential clinical use to prevent postoperative resynostosis in infants with craniosynostosis.


1671 (21383)

Desert hedgehog is upregulated by FGF2 in mouse calvaria. A. YAVARI*, W. WANG, and M.A. IGNELZI, Jr., University of Michigan, School of Dentistry, USA

Craniosynostosis, the premature fusion of the skull bones at the sutures, is the second most common birth defect that affects the face and skull. The flat bones that comprise the top of the skull, or calvaria, are most often affected and craniosynostosis is a feature of over 100 human syndromes and conditions. Mutations in human fibroblast growth factor (FGF) receptors 1, 2 and 3, thought to result in increased signaling, have been shown to lead to craniosynostosis. We have shown that FGF2-soaked beads placed on mouse calvaria leads to premature fusion of sutures, increased expression of Msx2 and increased expression of bone marker genes Osf2/Cbfa1 and Osteocalcin. Hedgehog genes have been implicated in calvarial development. Objectives: The purpose of this study was to test the hypothesis that increased FGF signaling would lead to increased Dhh expression. Methods: Calvaria were cultured in serum free media for 48 hours, RNA was extracted, and Dhh expression was quantitated using PCR-ELISA. Experiments were repeated 3 times and statistical differences in expression were assessed using Student’s t-test. Results: FGF2 led to increased Dhh expression compared to bead only and no bead controls (p<0.01). Conclusions: These data demonstrate that Dhh is regulated by FGF2 and implicate hedgehog genes in craniosynostosis.


1672 (20011)

Continuous versus single dose FGF2 treatment of rat calvarial osteoblasts. D. MORGAN*, P.L. WINNARD, and A.M. MOURSI, Ohio State University, Columbus, USA

Normal cranial suture formation and craniosynostosis have been associated with fibroblast growth factors (FGF) and their receptors. Objectives: The purpose of this study was to determine the effect of a single dose versus continuous exposure of FGF2 on rat calvarial osteoblasts. Methods: Primary fetal rat calvarial osteoblasts were cultured in media with FGF2 (50 ng/ml) added on day 1. On day 3 single dose cultures received fresh media without FGF while continuous exposure cultures received media supplemented with fresh FGF2. These conditions were maintained with media changes every other day through day 17. Results: Continuous exposure cultures demonstrated an increase in attachment and proliferation compared to no-FGF control cultures as determined by AlamarBlue dye assay. Toluidine-blue staining confirmed the attachment and proliferation data, and showed that cells treated with FGF2 achieved an osteoblastic morphology. Mineralized surface area was similar to control in the continuous exposure cultures. In single dose cultures cell attachment and proliferation were similar to controls. However, in the single dose cultures mineralization was dramatically increased compared to controls and continuous exposure cultures. Conclusions: These results indicate that FGF2 can mediate rat osteoblast proliferation and differentiation through different mechanisms depending on the time and duration of exposure. This evidence further supports an important role for FGFs in normal cranial suture formation and craniosynostosis.


1673 (11464)

Orthodontic bond strength when using plasma light source. R.S. HOBSON*, Newcastle University, Newcastle upon Tyne, United Kingdom, and I. COZMA

Bonding of orthodontic brackets using light has achieved widespread use. Plasma lights, require less time to cure composite and initial studies into their use in orthodontic bonding have been reported (Sfondrini et al. A J Orthod 2001, 119; 30-35).

Objectives: This study investigated the effect of a plasma light in comparison with a conventional light source on bond strength.

Methods: 80 human premolar teeth were used. All teeth were cleaned using pumice and a rotary brush, acid etched for 30 seconds using 37% phosphoric acid, washed and dried before bonding 0.018 GAC Omni arch premolar brackets using Transbond (3M, Monrovia, Ca, USA) composite adhesive as described by the manufacturer. 3 groups of 20 teeth were light cursed using the Plasma light (Apollo 95E, SED, France) for 1, 3 and 6 seconds respectively. The control group was cured using a 3M light for 30 seconds. Teeth were stored in distilled water at 37oC for 24 hours. Sheer-peel bond strength was tested using an Instron.

Results: Bond strength in MPa (standard deviations) were:

1 seconds plasma light 13.23 MPa (5.46); 3 seconds plasma light 12.19 MPa (5.65); 6 seconds plasma light 20.21 MPa (6.28); 30 seconds conventional light 19.98 MPa (6.16)

Student T tests showed that there were significant differences in bond strength between 1 and 6 sec plasma (p<0.01); 3 and 6 sec plasma (p< 0.001); 1 sec plasma and control (p<0.01) and between 3 sec plasma and controls (p<0.001). There was no significant difference between 1 and 3 sec plasma (P>0.05); 6 sec plasma and controls (p>0.05).

Conclusions: It was concluded that curing Transbond with a plasma light for 6 seconds achieves the same bond strengths as conventional light curing.


1674 (13099)

Shear Bond Strength of Conventional and One-step Orthodontic Bonding Materials. T.L. CUTLER*, B.B. MAXSON, W.C. WAGNER, A.L. NEME, and R. KULBRESH, University of Detroit Mercy, MI, USA

One-step systems are now available for bonding orthodontic brackets. Objectives: It was the aim of this study to compare shear bond strength of a traditional two-step orthodontic bonding system with one-step alternatives. Methods: Traditional resin composite adhesive(Transbond XT) with acid etch and primer steps was used as the control(Group A). A one-step self-etch/primer was also used with this adhesive(Group B). A resin-modified glass ionomer(RMGI) adhesive(Fugi Ortho LC) was used in the traditional manner with its conditioner(Group C) and the RMGI was used with the one-step self-etch primer used in Group B(Group D). Extracted third molars stored in 0.2% sodium azide were randomly assigned to each of the 4 groups(n=12). Buccal surfaces were ground with 600-grit sandpaper and 1-m m diamond-polished leaving a flat enamel surface for bonding. Teeth were mounted in acrylic resin for testing, leaving buccal surfaces exposed. Enamel surfaces were treated according to manufacturer’s specifications and adhesive applied to each prepared surface by dispensing the material into a cylindrical stainless steel mold and light-curing for 60 seconds. After ³ 24 hours storage in 100% humidity, samples were shear-loaded with an Instron Universal Testing Machine at a crosshead speed of 0.5 mm/minute. Data were analyzed with ANOVA and Tukey HSD(a=0.05). Results: Mean bond strengths(MPa) were: A=17.0, B=18.6, C=10.0, D=14.6. All groups were statistically similar except the traditional RMGI(Group C). Conclusions: In conclusion, one-step orthodontic bonding materials demonstrated comparable or superior bond strengths compared to traditional methods. Supported by UDMSD student project grant. teresacutler@hotmail.com


1675 (10315)

Shear Bond Strength of Two Materials: Transbond XT and Experimental Amorphous Calcium Phosphate. J.R. OKEMWA1, E.M. KUDLICK*1, and F.C. EICHMILLER2, 1 Howard University College of Dentistry, Washington, DC, USA, 2 American Dental Association Health Foundation, Gaithersburg, MD, USA

Objectives: In this study, the shear bonding strengths of two materials were compared in order to evaluate the potential for an experimental amorphous calcium phosphate(ACP) bonding material composed of a mixture of two resins(BisGMA-24%,tryethylene dimethacrylate(TEGDMA), hydroxyethylmethacrylate(HEMA),with MPTMS, Benzoyl peroxide catalyst (BPO) and antioxidant stabilizer(BHT). The second resin also contained a comphorquinone light initiator, and two amine initiators. Both of these resins were mixed 60% by mass resin with 40% by mass ACP(amorphous calcium phosphate filler. Orthodontic brackets were bonded to 60 human premolars using Transbond XT and the ACP composite bonding materials. Methods: Using the Instrom Universal Testing Machine, the shear strength of each bonding material was tested under two different time intervals: 24 hours and 7 days in order to compare the shear bond strengths of each material and to evaluate whether there was a degradation in strength between each time interval. Results: The analysis of variance (ANOVA) showed that there was a significant difference between the two cement types, but there was no difference between the two time periods and no interaction was present between cement type and time. There was no difference between either bonding cement at 24 hours and 7 days. At both 24 hours and 7 days with Transbond XT had more than twice the fracture strength than ACP. The combined average fracture strength for Transbond XT was 123.8 Newtons while that of the ACP cement was 58.9 N. The difference in mean shear strength between the two cements was 65.5 N. Conclusions: In its current formulation, the experimental ACP bonding material did not have sufficient shear bond strength to be mechanically adequate for routine clinical use.


1676 (13497)

Laboratory performance of a self-etching primer for orthodontic bonding. Y. ALJUBOURI*1, D. MILLETT1, and W. GILMOUR2, 1 Glasgow Dental Hospital and School, United Kingdom, 2 University of Glasgow, United Kingdom

Objectives: To compare mean shear bond strength of stainless steel brackets with microetched base (3M Unitek, Monrovia, CA) bonded with a light-cure composite using a self-etching primer (Transbond XT, 3M Unitek, Monrovia, CA) or a two-stage etch and prime (Transbond XT, 3M Unitek, Monrovia, CA) system. Bonding time, adhesive remnant scores, adhesive clean up time and survival time of brackets bonded with each system were assessed also. Methods: Brackets were bonded to 30 premolars with each system according to manufacturer’s instructions. Bonding time was recorded for each specimen using a stopwatch. After storage in a humidor at 37°C for 24 hours, shear debonding force was measured using a Nene M3000 testing machine with a crosshead speed of 0.5mm/min. The Adhesive Remnant Index and adhesive clean-up time were recorded for each specimen. Another 10 premolars were bonded with each system and used to assess survival time following application of mechanical stress in a ball mill for 100 hours. Results: Bonding time of the 2 stage bonding group was longer than that of the self-etching primer group (mean difference 59 sec; 95%CI 51.8 to 66.2 sec, two sample t-test p<0.001). The mean shear bond strength of the 2 stage bonding group was significantly greater than the self-etching primer group (mean difference 17.1 N; 95% CI 4.7 to 29.5 N, two sample t-test p=0.008). Distribution of ARI scores and mean clean up times did not differ significantly between the two adhesive systems. Only one of the 2 stage bonding group failed within 1 hour in the ball mill. Conclusions: Mean shear bond strength of brackets bonded with self-etching primer was significantly less than those bonded with 2 stage bonding. Supported by 3M Unitek.


1677 (15752)

Effect of Using Cyanoacrylate Adhesive to Bond Orthodontic Brackets. S.E. BISHARA*, L. VONWALD, J. LAFFOON, and J. WARREN, University of Iowa, Iowa City, USA

During bonding of orthodontic brackets to enamel, conventional adhesive systems use three different agents: an enamel conditioner, a primer solution, and an adhesive resin. A unique characteristic of some new bonding systems, is that they neither need a priming agent nor a curing light to bond brackets. Such an approach should be more cost-effective to the clinician and indirectly to the patient. The purpose of this study was to determine the effects of using a cyanoacrylate adhesive on the shear bond strength of orthodontic brackets and also on the bracket/adhesive failure mode.

Bonding Procedure: The brackets were bonded to extracted human teeth according to one of two protocols; Group 1(Control): Teeth were etched with 37% phosphoric acid. After applying the primer, the brackets were bonded with composite adhesive Transbond XT (3M Unitek, Monrovia, CA) and light cured for 20 seconds. Group II: Teeth were etched with 35% phosphoric acid. The brackets were then bonded with Smartbond (Gestenco International, Gothenburg, Sweden).

The present in vitro findings indicated that the use of the cyanoacrylate adhesive to bond orthodontic brackets to the enamel surface did not result in a significantly different (F-value=0.71 and P=0.24) shear bond force (´=5.8 ± 2.4 MPa) as compared to the control group (´=5.2 ± 2.9 MPa). The comparison of the ARI scores indicated that there was significantly (P=0.006) less residual adhesive remaining on the tooth with the cyanoacrylate than with the conventional adhesive system.

In conclusion the new adhesive has the potential of being used to bond orthodontic brackets while reducing the total bonding time.


1678 (17739)

The effect of enamel treatment and moisture storage duration on bracket debonding characteristics. T. BROSH*, O. SARNE, and S. STROUTHOU, Tel Aviv University, Israel

Objectives: (1) To compare, in vitro, the effect of enamel conditioning procedures and different lengths of moisture exposure on orthodontic bracket debonding strength. (2) To determine the failure site by scanning the debonded brackets after the debonding procedure. Methods: Metallic brackets were bonded to the buccal surface of forty extracted premolars using Transbond XT (3M). The teeth were randomly divided into four groups: (A) Acid-etching (37% phosphoric acid), moisture exposure for 48 h (B) Similar acid-etching, moisture exposure for a year (C) Sandblasting for 3 sec 3 mm away from the treated surface, followed by the above mentioned acid-etching procedure, moisture exposure for 48 h (D) As in C, moisture exposure for a year. Before brackets were debonded, all teeth underwent thermo-cyclic treatment. Brackets were debonded using orthodontic pliers connected to a loading machine (Instron) simulating clinical debonding procedure. Peak debonding force was recorded. Debonding strength was calculated by dividing the debonding force by bracket's base area. After debonding, all brackets were scanned using scanning electron microscope (SEM) and scaled for Bracket Adhesive Remnant Index (BARI). When adhesive was found on the bracket's base, calcium presence was also scanned using Energy Dispersive X-ray Spectrometer (EDAX). Results: Debonding strength varied between 12.2. ± 3.7 and 13.0 ± 3.9 MPa with no statistical significance between treatment type or moisture exposure duration. Enamel treated with sandblasting and acid-etching resulted in a significantly higher BARI (p=0.05) compared to acid-etching treatment alone. Specimens stored for a year showed significantly higher BARI (p=0.05) for both treatments and more calcium remnant could be observed. Conclusions: Adding sandblasting to bracket bonding procedure does not require more debonding force, however, tooth damage may increase. Long moisture storage duration of bracket bonding to tooth surface increases tooth damage occurrence.


1679 (21164)

Shear bond strength of different brackets using resin modified glass ionomer. M.G.G. CARIAS*1, S. MACARI2, M.B.S. STUANI1, R.G.P. DIBB1, and M.C. BORSATTO3, 1 Faculty of Dentistry of Ribeirão Preto - University of São Paulo, Ribeirão Preto - SP, Brazil, 2 Faculty of Dentistry of Ribeirão Preto, University of São Paulo, Ribeirão Preto - SP, Brazil, 3 University of São Paulo - Ribeirão Preto Dental School, Ribeirão Preto-SP, Brazil

Objective: The aim of this study was to evaluate “in vitro” the shear bond strength of three different types of brackets using glass ionomer adhesive in bovine enamel. Method: Seventy-two bovine incisors were mounted in PVC tubes, embedded in acrylic resin and buccal surface was ground until enamel planification. After carrying out the prophylaxis with pumice. The samples were randomly divided in two groups (n=24) and three subgroups. A – Polished stain steel mesh casted bracket; B – Sand-blasted stain steel mesh casted bracket; C – Sand-blasted stain steel monoblock bracket. The brackets were bonded with ConciseTM (Co) and Fuji Ortho LCTM (Fo) following manufacturer’s instructions. Specimens were stored at 37°C for 24 hours. Universal Testing Machine (0.5 mm/min) was used to perform the bond strength with load cell of 200 Kgf. Results: The means (MPa) obtained were Co: A – 7.45 (± 2.95), B – 13.62 (± 3.53), C – 17.47 (± 7.51);and Fo: A – 12.43 (± 2.32), B – 17.21 (± 2.77), C – 18.92 (± 2.87). Data were analyzed by ANOVA and Tukey test. The bracket type was statistically significant for adhesion, since the sand-blasted stain steel mesh casted bracket and monoblock bracket showed better results. The glass ionomer adhesive Fuji Ortho LCTM showed superior results than the resin cement ConciseTM (p<0.001). It was observed superior adhesion in groups Fo B and Fo C. Conclusions: The bracket base design influenced the shear bond strength and the resin modified glass ionomer adhesive showed better results.


1680 (14250)

Shear Bond Strength (SBS) of a Ca-PO4-enriched Bonding Agent to Sound and Carious Dentin. S.H. DICKENS*, American Dental Association Health Foundation, Gaithersburg, MD, USA

A remineralizing, resin-based Ca-PO4 cement (RC), having moderate dentin SBS has previously been reported. Bonding agents (BA) placed between RC and dentin to improve SBS significantly reduced the dentin remineralization. Thus, novel dentin BAs containing dicalcium phosphate anhydrous mineral were designed to provide the potential for better dentin remineralization. Objectives:  A factorial design was used to test the effects of Ca-PO4 addition (unfilled bonding agent or Ca-PO4 –filled), dentin type (sound, natural caries, or artificial caries), and conditioner type (37% H3PO4 or a polymerizable conditioner) on the SBS of a single solution BA.  Methods: All 12 factorial combinations of treatments were tested with n=4 for each group.  36 extracted caries-free and 16 carious mounted human molars were cut to expose flat dentin surfaces. 18 of the caries-free molars were demineralized at pH of 4.8 for 48 h. Each tooth received two coats of BA followed by a 10 s light cure. Composite resin was inserted into Teflon-coated irises and light-cured. SBS was tested after 24 h water storage. Results: SBS ranged from (24 to 39) MPa.  Two-way ANOVA and Tukey test found significant differences for both filler type and substrate when using H3PO4; for the polymerizable conditioner only the substrates were different (p < 0.05). Conclusions:  A Ca-PO4-enriched BA mediated high SBS to sound and carious dentin, and may provide the potential for enhanced remineralization when used with a resin-based Ca-PO4 cement. Support: NIDCR R01-DE13298, ADAHF and NIST.


1681 (14533)

Comparison of Self-Etching Systems and Phosphoric Acid on Cut Enamel. M. SCHILTZ*, P. BROWN, L. SHARP, and B.I. SUH, Bisco, Inc, Schaumburg, IL, USA

Objective: To determine if shear bond strength (SBS) on cut enamel etched with phosphoric acid or with self-etching systems would be affected when stored at 37º C over a period of twelve weeks.  Methods: Human molars were set and the enamel ground flat using the fine side of an orthodontic grinder. The control sets consisted of 32% phosphoric acid Uni-Etch (Bisco) for 15s, rinse, and then followed by One-Step (OS)(Bisco) or One-Step Plus (OS+)(Bisco) according to manufacturer instructions.  The two self-etching systems, One-Up Bond F (1U)(Tokuyama) and Clearfil SE (SE)(Kuraray) were applied according to manufacturer’s instructions.  A light-cured composite, Universal Bisfil (Bisco), was placed into a #9 gel cap (area 0.03692 cm2), and light cured for 40s@500 mW/cm2 on two sides.  Specimens were stored at 37º C in DI water and broken at various time intervals.  All specimens were tested until failure using a universal tester at a speed of 5 mm/min.  Results:

 

2 hours

24 hours

96 hours

2 weeks

4 weeks

8 weeks

12 weeks

 

MPa(SD)

MPa(SD)

MPa(SD)

MPa(SD)

MPa(SD)

MPa(SD)

MPa(SD)

OS

30.3(6.9)

33.9(7.4)

40.4(8.7)

32.9(9.9)

35.0(7.5)

26.7(7.2)

31.9(6.3)

OS+

32.5(5.8)

37.8(7.8)

34.4(9.2)

28.6(7.2)

36.0(1.9)

32.5(3.1)

33.1(4.2)

1U

7.0(1.3)

18.3(3.2)

33.5(6.0)

10.1(2.1)

19.2(2.9)

15.7(2.6)

14.2(3.2)

SE

33.5(5.4)

30.7(12.5)

29.2(7.6)

26.7(2.3)

25.7(2.8)

22.7(6.4)

33.5(5.3)

The SBS fell into two categories: a) those that did not change over time: OS, OS+, and SE and b) those that did change over time, 1U (p<0.05).  Conclusion: The two-step self-etching system (SE) SBS is comparable to phosphoric acid, however, single-step self-etching adhesive (1U) SBS decreased during the tested time interval.


1682 (14551)

Comparison of two different dentin shear bond strength testing techniques using nine dental adhesives. P. BROWN*, M. SCHILTZ, and L. SHARP, Bisco, Inc, Schaumburg, IL, USA

Objective:  To determine if two dentin shear bond strength [SBS] techniques are significantly different from one another. Nine adhesives were selected and compared to themselves using both techniques.  Methods:  Adhesives were applied to human molars according the manufacture’s instructions.  Included were:  One-Step (BOS)[Bisco], One-Step Plus (BOSP)[Bisco], Optibond Solo Plus (OSP)[Kerr], SingleBond (SB)[3M], Prompt L-Pop (PLP)[ESPE], Prime & Bond NT (P&B)[Dentsply], SE Bond (SEB)[Kuraray], Excite (EXC)[Vivadent], and Touch & Bond (T&B)[Parkell]. The first technique involved using #5 gel cap method (GCM) [area=0.1684cm2] to apply a light curable composite [Universal Bisfil by Bisco] to the prepared dentin, soak in 37ºC water for 2 hours, then testing to failure on an Instron machine.  The Instron blade is flat with a head speed of 5mm/minute.  The second technique is an Ultradent method [UDM] using a special jig, area=0.0444cm2, and a special shaped blade in the Instron at a head speed of 1mm/minute.  Results:

 

BOSP

BOS

SEB

SB

OSP

T&B

EXC

P&B

PLP

#5 GCM

25.2

24.9

23.5

22.6

21.1

16.2

11.2

14.0

6.7

MPa [s.d.]

[2.1]

[2.4]

[4.6]

[3.1]

[3.0]

[3.1]

[7.4]

[5.8]

[1.6]

UDM

36.5

35.7

32.5

32.4

32.8

25.0

20.6

20.6

12.5

MPa [s.d.]

[4.8]

[5.3]

[9.7]

[7.8]

[8.5]

[2.4]

[11.3]

[9.9]

[4.4]

Conclusion:  Analysis of data using one-way ANOVA followed by Student-Neuman-Kuels multiple comparisons revealed that for 7 of the 9 adhesives, the two SBS techniques yielded statistically significant differences [p<0.05%].  In ranking the products, both tests gave the same order of high to low average values except for P&B which was 7th in the GCM but 8th in the UDM group.

 

 


1683 (16177)

Effects of Agitation of Self-etching Primers/Adhesives on Resin-Dentin Bond Strength. K.M. CHAN*1, F.R. TAY1, N.M. KING1, S. IMAZATO2, and D.H. PASHLEY3, 1 University of Hong Kong, Hong Kong SAR, China, 2 Osaka University, Japan, 3 Medical College of Georgia, Augusta, USA

This study compared the microtensile bond strength (µTBS) and the ultrastructure of resin-dentin interfaces of four self-etching systems that were applied to dentin with thick smear layers. Human third molars were ground with 180-grit SiC papers to expose deep coronal dentin. A 3-mm vertical slit was made along the diameter of each tooth to fit a glass cover slip, dividing each tooth into two bonding surfaces. Two two-step, self-etching primers (ABF experimental system, Kuraray and Imperva Fluoro Bond, Shofu) and two single-step, self-etching adhesives (One-Up Bond F, Tokuyama and AQ Bond, Sun Medical) were examined. Adhesives were applied to one side of the teeth passively, and to other side with continuous agitation for the same self-etching period. Incremental composite buildups were performed and beams with cross-sectional areas of 0.81mm2 were prepared for µTBS evaluation. Demineralized, bonded specimens were processed for TEM examination. Two-way ANOVA showed that both the adhesive type and the application mode significantly affected µTBS results. However, the interaction of these two factors was not statistically significant (P>0.05). For each adhesive, agitation produced significantly higher µTBS than passive application. With passive application, all systems diffused through thick smear layers and formed thin hybrid layers in intact dentin. With continuous agitation, smear layers were completely dispersed or dissolved, and thicker hybrid layers with upstanding collagen fibrils were observed. It is concluded that bonding of mild self-etching primers/adhesives to dentin with clinically relevant, thick smear layers may be improved by continuous agitation during the self-etching process. (Supported by Faculty of Dentistry, HKU and grant DE 06427 from NIDCR)


1684 (16625)

Early bond strength of MMA resin cement to dentin. Y. SEKI*, Y. KITASAKO, M. NAKAJIMA, and J. TAGAMI, Tokyo Medical and Dental University, Japan

Objectives: To evaluate early tensile bond strengths and degree of conversion of chemical-cured MMA resin cements.

Methods: Forty bovine teeth, stored frozen, were used in this study. Dentin surfaces were exposed and finished with wet 600-grit SIC paper. The bonded area was demarcated by placing a piece of tape on the prepared surface in which a 4 mm in diameter. Two commercial resin cements were used; TOKUYAMA M-Bond (TOKUYAMA) with self-etching primer, and Super-Bond C&B (SUNMEDICAL) with 10-3 conditioner. The tensile bonds were tested at 10 minutes and 24 hours after placement of the metal rod at a cross-head speed of 2.0 mm/min. To evaluate degree of conversion, gas chromatography (GC-9A, SHIMADZU) was used to analyze degree of remaining MMA resin monomer. Mean bond strengths and degree of remaining MMA resin monomer were compared statistically by one-way ANOVA and Fisher's PLSD test (p<0.05).

Results: The mean tensile bond strengths (MPa±SD) at the different time periods (10 minutes and 24 hours) for M-Bond were 7.9±2.6, and 15.0±2.3, Super-Bond C&B were 2.9±0.7, and 12.5±4.5, respectively (n=10). The mean remaining resin monomer (%) at the same time periods for M-Bond were 8.94, and 0.58, Super-Bond C&B were 40.85, and 25.02, respectively (n=3). The 24 hours bond strengths of both resin cements were significantly greater than that at 10 minutes (p<0.05). Although there were no statistical differences in mean bond strengths between M-Bond and Super-Bond C&B (p > 0.05) after 24 hours, the 10 minutes bond strengths of M-Bond were significantly greater than that of Super-Bond C&B (p<0.05). The degree of remaining MMA resin monomer of M-Bond were significantly less than that of Super-Bond C&B (p<0.05).

Conclusion: M-Bond with self-etching primer showed the higher bond strength at early cementation.


1685 (16225)

Reversal of Compromised Bonding in Carbamide Peroxide-Bleached Enamel. S. LAI*1, F.R. TAY1, Y.F. MAK1, G.S.P. CHEUNG1, M. TOLEDANO2, R. OSORIO2, R.M. CARVALHO3, and D.H. PASHLEY4, 1 The University of Hong Kong, Hong Kong SAR, China, 2 University of Granada, Spain, 3 University of São Paulo, Brazil, 4 Medical College of Georgia, Augusta, USA

This study examined the hypothesis that compromised bonding in carbamide peroxide (CP)-bleached enamel is caused by the oxidizing action of the bleaching agent, and may be reversed by treatment with a reducing agent before bonding. Unabraded, mesial and distal enamel from human third molars were etched with 32% phosphoric acid and bonded with Single Bond (3M ESPE) or Prime&Bond NT (Dentsply) after treatment with:  [1] distilled water for 8 h (control) [2] 20% CP gel (Ultradent) for 8 h; and [3] 20% CP for 8 h followed by 10% sodium ascorbate (SA) solution for 4 h. Composite buildups were performed using Z100 (3M ESPE). After 24 h at 37°C, composite-enamel bonded beams of approximately 0.8 mm2 were obtained for microtensile bond strength (µTBS)testing (N=16-21). Separated specimens were prepared with Protect Liner F (Kuraray) and processed for TEM. Additional etched, but unbonded enamel surfaces from each group were also examined using SEM. Two-way ANOVA and Tukey tests revealed significant differences among the three treatment groups (P<0.001) but not between the adhesives (P=0.196).

Adhesive

mTBS of 32% phosphoric acid-etched, unabraded enamel  (MPa)

Distilled water (Control)

20% CP

20% CP, then 10% SA

Single Bond

32.0 ± 6.0 A

24.0 ± 5.1 B

33.5 ± 8.7 A

Prime&Bond NT

33.1 ± 4.2 A

23.7 ± 7.9 B

36.2 ± 7.3 A

TEM and SEM showed uniformly-etched aprismatic enamel with partially dissolved apatite crystallites in all groups. Reduction of resin-enamel bond strengths in CP-treated etched enamel is likely related to changes in the redox potential of the bonding substrate that affect the polymerization of adhesive resin components. (Supported by Grant DE06427 from NIDCR and CNPq 300481/95-O)


1686 (19113)

Bond strength to caries-affected dentin of glass ionomer cements. R.G. PALMA DIBB*, C.G. CASTRO, R.P. RAMOS, D.T. CHIMELLO, and M.A. CHINELATTI, University of São Paulo - Ribeirão Preto Dental School, Ribeirão Preto-SP, Brazil

Objectives: The aim of this study was to evaluate the bond strength of a resin-modified (Fuji II LC – GC Corp.) and three conventional (Ketac-Fil and Ketac Molar – ESPE, and Fuji IX – GC Corp.) glass ionomer cements to caries-affected dentin. Methods: For this purpose, 40 human molars with occlusal caries in dentin were selected and embedded in acrylic resin. Specimens were grounded using water sandpapers n. 280-600 to expose the carious dentin and the infected dentin was removed with curets, following the atraumatic restoration technique (ART). Dentin surface was flattened with water sandpaper n. 400, treated using a 40% polyacrylic acid for 10 seconds, rinsed and water excess was removed. Following surface treatment, a glass ionomer cone was prepared using a teflon matrix. Fuji II LC was inserted in two increments, light-cured for 40 seconds each; the last increment was covered with a poliester strip. The conventional glass ionomer cements were inserted in a single increment, covered with strip for 8 minutes until cure was completed. The cones were protected with copal varnish. Specimens were stored in distilled water at 37o C for 24 hours in stove and after this period the bond strength test was performed with Universal testing machine (0.5 mm/min). Results: The results in MPa were: Fuji II LC: 8.33 (±2.35); Ketac-Fil: 2.46 (±1.60); Ketac Molar: 0.83 (±1.18) and Fuji IX: 1.45 (±1.70). The statistical analysis was accomplished with ANOVA and Tukey test. Fuji II LC showed higher bond strength values and was superior to the other groups. The conventional cements indicated for ART (Ketac Molar and Fuji IX) presented the lowest means. Conclusion: Based on the results obtained it may be concluded that Fuji II LC presented significant adhesion to caries-affected dentin and may be also indicated for the atraumatic restoration technique.


1687 (15514)

Effect of Surface Treatments on the Wettability of Ceramics by Resin. B. ALEGRE*, W. OH, E.M. SONG, C. SHEN, and K.J. ANUSAVICE, University of Florida, Gainesville, USA

Repair of ceramic-based prostheses generally results in relatively short clinical survival times, possibly because of poor wettability of the ceramic by the adhesive resin. The objective of this study was to test the hypothesis that chemical etching promotes the greatest surface area and wettability by a probing liquid resin. After firing, three types of ceramics (two pressed core ceramics (E) and (X), and one veneering ceramic (V) were subjected to one of three surface treatments: (1) polished through 1200 grit SiC abrasive (P); (2) grit-blasted by 50 mm A12O3 (B); and (3) etched by 5% HF for 2 min (E). Each specimen in groups B and E were also polished through 1200 grit abrasive prior to treatment. Each of 10 specimens (1.5 ´ 10 ´ 15 mm) was steam cleaned after surface treatment. Wettability of each specimen was determined by a Dynamic Contact Angle Analyzer. Probing media included HPLC water (g=72.6 mJ/m2) and a resin mixture (35% BisGMA/65% TEGDMA; g=39.7 mJ/m2 ). Both advancing (qa ) and receding (qr ) contact angle values were recorded. Generally, ceramic E exhibited the greatest contact angle (lowest wettability) followed by ceramic V and ceramic X. Two-way ANOVA revealed statistically significant differences between mean q values for each ceramic by treatment. The ranking of contact angle by treatment decreased in the order, P>B>E (p£ 0.001) for all groups. The water medium yielded lower mean qa values compared with those for the resin medium (p£0.001), while the resin medium yielded lower qr than those for water (p£ 0.001). However, the choice of medium did not alter the ranking order by surface treatment or by material. This phenomenon resulted from the higher viscosity of the resin, which caused both a slower rate of wetting during immersion and a slower rate of release during removal. Consistently high q values associated with the polished surface and frequent occurrence of zero qavalues with etched surfaces further supported the increase in wettability because of increased surface area. Surface wettability varied with the type of probing medium. To be clinically relevant the medium used should have the some composition as that of the resin adhesive. Supported by a UFCD Student Fellowship and Ivoclar North America, Inc. balegre@ufl.edu


1688 (18807)

Effect of surface conditioning methods on the bond strength of luting cement to ceramics. M. ÖZCAN*, and P. VALLITTU, University of Turku, Finland

Objective: The aim of this study was to evaluate the effect of three surface treatments on the bond strength of a BIS-GMA based luting cement to six ceramic types, namely In-Ceram (Vita Zahnfabrik), Finesse (Dentsply), ZrO2 (Nobel Biocare), Empress II (Ivoclar), Procera (Procera Sandvik), Experimental alumina (Finland). Methods: Six samples in discs were fabricated for each group (total: 218). The samples were assigned to one of the following treatment conditions: (1) Hydrofluoric acid gel (2) Sandblasting (110 µm Al2O3), (3) Silicacoating (Rocatec, 3M ESPE). Luting cement (Variolink® II, Vivadent) was bonded to the conditioned specimens using teflon tubes. All samples were tested at dry and thermocycled (6000, 5ºC-55ºC, 30 sec) conditions in a universal testing machine (1mm/min). Results: The shear bond strengths in MPa (SD) were as follows:

 

Acid etching

Al2O3

Silicacoating

 

  Dry

TC (6000)

Dry

TC (6000)

Dry

TC (6000)

Finesse

29.4 (9.0)

13.7 (11.4)

38.8 (8.1)

9.4 (6.2)

35.7 (0.4)

 9.7 (4.2)

In-Ceram

8.5 (6.5)

0.6 (1.4)

19.6 (3.4)

7.4 (1.4)

21.8 (8.5)

14.5 (6.6)

ZrO2

8.1 (3.7)

1.1 (1.4)

16.1 (4.2)

4.7 (2.6)

17.4 (5.7)

8.9 (1.6)

Empress II

26.4 (13.3)

23.7 (10.5)

20.1 (4.3)

4.4 (2.1)

30.4 (4.1)

9.2 (3.0)

Procera

5.3 (2.1)

0

6.7 (2.3)

2.35 (0.8)

8.5 (4.5)

3.7 (4.1)

Exp. alumina

18.1 (15.5)

4.7 (1.1)

12.9 (4.0)

4.25 (1.4)

17.0 (8.0)

8.5 (2.1)

ANOVA showed that bond strength values decreased significantly after thermocycling (p<0.001) in all conditioning methods. Significantly lower results were obtained for acid etched specimens than those treated with either Al2O3 or silicacoating (ANOVA p<0.001) for In-Ceram, ZrO2, Procera and experimental alumina. Conclusions: Silicacoating can be used to obtain higher bond strength of luting cement to In-Ceram, ZrO2, Procera and experimental alumina whereas acid etching could still be recommended for Finesse and Empress II.


1689 (21569)

Fluoride-containing calcium phosphate cement: A preliminary in vitro study. V.S. GARCIA*1, K. ISHIKAWA2, and M. NISHINO1, 1 The University of Tokushima,Japan and University of Baguio, Baguio City, Philippines, 2 Okayama University Graduate School, Japan

Objective: Either NaF or CaF2 was incorporated into the self-setting calcium phosphate cement (CPC) for the purpose of developing a new dental cement that may serve as a delivery system for the release of fluoride for various clinical applications. Methods: NaF was incorporated in the liquid phase in concentrations of 10, 100 and 500 mmol/L. CaF2 was incorporated in the powder phase in contents of 5, 10 and 50 mass%. CPC-fluoride (CPC(F))disk specimens were prepared at a powder to liquid ratio of 4. The mechanical strength of the set mass was measured in terms of wet diametral tensile strength (DTS) value. The %conversion of CPC to hydroxyapatite (OHAp) was assessed from 1 to 10 hrs by powder x-ray diffraction analysis. Fluoride ion release from CPC(F) was measured weekly for 8 wks. Results: CPC(F) showed the same DTS values (MPa)with CPC, except for CPC(CaF2:50 mass%) which was significantly lower (paired t-test, p<0.01). CPC(F) had higher %conversion to OHAp than CPC. Weekly fluoride release (µg/g)showed no significant difference within CPC(NaF)group and within CPC(CaF2)group, except for CPC(CaF2:50 mass%)(Fisher's PLSD test, p<0.0001). Conclusion: It is concluded that given the appropriate fluoride concentration, the physicochemical properties of CPC is improved and that CPC(F) is able to release fluoride for an extended period of time.


1690 (12118)

The Influence of the Mixed Alkali Ratio on the Solubility of Fluorcanasite Glass-Ceramic. C.W. STOKES, R.J. HAND, and R. VAN NOORT*, University of Sheffield, United Kingdom

Objectives: Fluorcanasite glass-ceramics produced to date have been found to have excessive solubility for intra-oral use. The effect of modifying the soda/potassia ratio on the solubility of fluorcanasite composition glasses was investigated.

Methods: Seven glasses were formulated using 60SiO2-(15-y)Na2O-yK2O-15CaO-10CaF2 where y was 0<=y<=15. The glasses were analysed for crystallisation temperatures using DTA at 10°C per minute. For crystalline phase determination using XRD, the glasses were heated to 850°C at 5°C per minute and held for 1 hour before furnace cooling. Beads, with an average diameter of 1.85mm, were produced using a lost-wax process from both the mixed-alkali fluorcanasite glasses and a commercially available dental ceramic system (Empress II, Ivoclar A.G., Liechtenstein). 100 beads of each glass were dried for at least 4hrs at 150°C, cooled in a dessicator and weighed to the nearest 1µg. The beads were then added to 50ml of 4% acetic acid solution at 80°C for 8 hours. Chemical solubility was calculated as µg/cm2 from the mass difference.

Results: It was found that solubility varied with alkali content being low for the low potassia content glasses (265 ±177µg/cm2) rising to a maximum solubility (2488 ±48µg/cm2) at the stoichiometric fluorcanasite composition. The solubility then reduced, exhibiting a further minimum at a [K]/[K+Na] ratio of 0.52 (389 ±128µg/cm2), before rising again. The Empress II glass-ceramic exhibited a solubility of 223 ±132 µg/cm2.

Conclusions: The chemical solubility test shows that solubility of the fluorcanasite forming glass varies with Na/K ratio suggesting that a variant of the mixed-alkali effect exists in this system. Based on these findings it is possible to produce a glass with a solubility comparable to that of other dental ceramics.


1691 (12180)

Transfer of the Methods of Evidence Based Medicine to In-Vitro-Testing: Fracture Strength of Ceramic Anterior Crowns - a Meta-analysis. A.M. BUZELLO*, S. RINKE, and A. HUELS, University of Goettingen, Germany

Objectives: The object of this study was to perform a meta-analysis comparing the fracture strength of all-ceramic anterior restorations with metal-ceramic crowns (Goldengate, Vita, FRG) which served as a gold standard. Methods: A total of 432 crowns manufactured in 24 different studies were fabricated. The metal-ceramic crowns were made of a high precious alloy (Degunorm, Degussa, FRG) and ceramically veneered (Omega 800, Vita, FRG). The all-ceramic restorations were differently manufactured. In-Ceram caps (Vita, FRG) veneered with Vitadur Alpha (Vita, FGR) and mechanically milled restorations (Cerec2-/Celay-technologies) were made of either feldspatic or leucite reinforced ceramic, resulting in 24 different types of crowns which were all identically in shape. Fracture toughness of the crowns was determined in a universal testing machine. The statistical evaluation of the recorded loads resulting in fracture was performed with t-test (p<0,05). Further analysis was done using a graphical representation according to the evidence based dentistry by a Meta-analysis. Results: All crowns of all-ceramics types showed significantly different fracture resistance as compared to the metal-ceramic restorations. Also significant differences were recorded among the different types of the all-ceramic crowns. Conclusions: It was shown, that the fracture strength of the examined all-ceramic anterior crowns was sig. lower than the one of metal-ceramic crowns, but clearly higher than 600 N which was demanded by Schwickerath.


1692 (13443)

Texture Development in Heat-Pressed Fluoramphibole Glass-Ceramics. I. DENRY*, and J. HOLLOWAY, The Ohio State University, Columbus, USA

Previous studies have shown that heat-pressing of mica-base glass-ceramics led to crystal alignment along the direction of pressing as well as a significant increase in fracture toughness in the perpendicular direction. Objectives: the purpose of the present study was to determine if heat-pressing could also promote texture development in fluoramphibole glass-ceramics. Methods: a glass composition in the system SiO2-MgO-CaO-Na2O-K2O-F was prepared by melting at 1450°C for 2 hours. The glass was cast into cylindrical ingots (60x12 mm) which were cut into disks (12x1.5mm) and cylinders (12x10mm). Bar-shaped wax patterns (24x4x2mm; n=4) were invested with a phosphate-bonded investment. The glass cylinders were heat-pressed at 800, 825, 850 or 890°C in an automated pressing machine with a total processing time of 30 minutes. Disks that were submitted to the same heat treatment as the heat-pressed specimens served as controls. The crystalline phases were analyzed by x-ray diffraction. The microstructure was investigated by SEM. The degree of texture was evaluated on digital micrographs by measuring the distribution of crystal orientations with an image analysis software. The degree of texture of the heat-pressed specimens was compared to that of the controls using a chi-squared test. Results: all specimens pressed completely. X-ray diffraction revealed the presence of mica, diopside and fluorrichterite in all specimens. The microstructure was characterized by the presence of prismatic fluorrichterite crystals and hexagonal mica platelets. The fluorrichterite crystal distribution of the heat-pressed specimens was significantly different than that of the controls (p<0.001). Heat-pressing at 850°C led to the highest degree of texture with 72 percent of the crystals oriented between 0 and 30 degrees of the direction of pressing. Conclusions: Heat-pressing led to a significant degree of texture in a fluoramphibole glass-ceramic. The highest degree of texture was obtained after heat-pressing at 850°C for 30 minutes. Supported by NIH-NIDCR Grant No. DE13570.


1693 (13523)

In-Vitro Wear Of Restorative Dental Materials. B. ABOZENADA*, R. POBER, and R. GIORDANO, Boston University, MA, USA

Restorative dental materials must fulfill many desirable properties, one of which is wear comparable to human enamel. Intra-oral wear of dental materials is a highly complex process due to the variable movements and loading which can occur and the hostile chemical (e.g. toothpastes), thermal and biological environments involved. Objectives: The purpose of this study was to test wear properties of numerous restorative materials under similar conditions to achieve at least a ranking of relative wear values. Methods:In this in-vitro study a simple pin-on-plate wear machine was used to evaluate eighteen machinable and conventional restorative materials. Repair acrylic resin and type III gold were used as references. The study composed of two parts, first a tooth-brushing abrasion test in which Oral-B toothbrushes and Crest toothpaste were used over four polished samples of each restorative material that are 20 x 14 x 2 mm (±1mm) each, volume loss was calculated after 60,000 cycles at 160 cycles/minute with an applied load of 400g. The surface roughness was measured before and after the test. Enamel abrasion was also conducted in which four square rods of the restoratives with polished tips were run over flat polished enamel surfaces with enamel rods were used as control. The volume loss of each restorative and also the volume loss of the enamel opposing it was calculated. Results:The enamel volume loss ranged from 0.36 ± 0.1(acrylic), 1.09 ± 0.04(enamel), 0.91 ± 0.25(fine grain porcelain) to 1.83 ± 0.09(coarser porcelain) mm3. Toothbrush abrasion showed that all restorative materials have higher wear rates than gold and much less wear rates than acrylic resin. Conclusions: Fine grained porcelains and composite resins showed the least amount of enamel wear which was similar to the control. Surface roughness increased significantly in composite resins and some low fusing porcelains.


1694 (13976)

The influence of interfacial surface roughness on the strength of bilayered dental ceramic composites. G.J. FLEMING*, and S.F. EL-LAKWAH, Birminghan University, Birmingham, United Kingdom

Objectives: The purpose of the current investigation was to examine the influence of interfacial surface roughness and relative layer height of reinforcing porcelain on the fracture origin and mode of failure of bilayered dental ceramic composites of Vitadur alpha core and Vitadur alpha dentine porcelain. Methods: Sets of 30 Vitadur-alpha core porcelain discs (15 mm diameter, 1.5 mm thickness) were prepared and further ground on 200 grit and 800 grit SiC abrasive paper. These specimens were bilayered to produce 180 samples with relative layer heights of 1:2, 1:1 and 2:1, respecively for the core and dentine porcelain. Mean fracture strengths, standard deviations and associated Weibull Moduli (m) were determined using bi-axial fracture (ball-on-ring) by testing either the reinforcing core or aesthetic dentine in tension. Results: The student-t-test analysis revealed a significant difference (P<0.001) between the dental ceramic composite groups tested with the core and dentine in tension. Crack propagation through the composite interface or delamination were the main failure modes. A discontinuity existed at the lower strength values in the survival probability plots for the specimens ground on 220 grit SiC abrasive paper. Conclusions: The discontinuity in the survival probability distributions appear to become more symmetric at low values of strength following further grinding treatment to remove large surface flaws. It is proposed that large flaws on the core interfacial surface of the bilayered specimens may be responsible for premature fracture in service.


1695 (18714)

Clinical Performance of Procera AllCeram Crowns. A.E. SCHMIDT*, B.H. WOLF, M.H. WALTER, and K.W. BOENING, University of Technology Dresden, Germany

Objectives: The purpose of this clinical trial was to evaluate the clinical performance and plaque accumulation of Procera AllCeram crowns in anterior and posterior teeth. The Procera AllCeram system (Nobel Biocare AB, Göteborg, Sweden) is a CAD/CAM system to fabricate full-ceramic single crowns with a dry sintered aluminum oxide core.

Methods: A total of 107 crowns (61 anterior and 46 posterior crowns) were inserted. Seventy patients (41 women, 29 men) with a mean age of 38.8 years received one or 2 artificial crowns. The clinical performance of the all-ceramic crowns was described by Kaplan-Meyer survivor analyses including the log-rank test for equality of survival distribution between anterior and posterior crowns. The quality of the restorations was evaluated by the rating system of the California Dental Association (CDA). Plaque Index (PI; Silness and Löe, 0-3) was rated at restored teeth and control teeth at 2 weeks, 3 months, 6 months, 12 months, and 18 months after placement.

Results: One anterior and three posterior crowns failed due to fracture. The over-all survivor rate at 18 months was 0.96±0.02 (cumulative survival ± standard error). The survivor rate for anterior all-ceramic crowns was 0.98±0.02; the posterior crown survivor rate was 0.93±0.04. The survival distribution of both groups did not differ significantly (p>0.05). The quality of the restorations evaluated by the rating system of the CDA was found to be satisfactory in all functioning crowns. Mean plaque scores ranged from 0.37 to 0.52 for the restored teeth, and from 0.39 to 0.54 for the control teeth. The mean plaque scores did not differ significantly between restored teeth and control at any visit (Wilcoxon-test, p>0.05).

Conclusions: It can be concluded, that anterior and posterior Procera AllCeramic crowns are a suitable option for clinical use. Posterior crowns appeared to be more prone to fracture than anterior crowns.


1696 (18940)

Leucite-Reinforced Glass Ceramic Inlays and Onlays after Eight Years in vivo. N. KRAEMER*, A. PETSCHELT, and R. FRANKENBERGER, University of Erlangen, Germany

Objective: Aim of the present study was to clinically evaluate the performance of IPS Empress inlays and onlays with cuspal replacements and margins below the amelocemental junction. Methods: Ninety six IPS Empress restorations (73 Class-II-inlays, 23 onlays / 39 premolars, 57 molars) were placed in 34 patients by six clinicians. The restorations were luted with four different composite systems (Syntac Classic with Tetric, Dual Cement, Variolink low, and Variolink ultra, all Ivoclar-Vivadent, Schaan, Liechtenstein). At baseline and after six months, one, two, four, six and eight years the restorations were assessed using modified USPHS criteria. Results: From 96 investigated restorations eight had to be replaced (failure rate 8%; survival analysis by Kaplan-Meier algorithm). Two teeth required endodontic treatment, six inlays revealed bulk fractures. Three inlays had to be replaced due to prosthodontic reasons and nine patients missed the six years recall (“dropout”). Fifty-seven of the fillings were in good condition. Between the recall assessments (A 6 months, B 1 year, C 2 years, D 4 years, E 6 years, F 8 years) significant differences (Friedman test; p<0.05) were detected for the following criteria ["excellent", "good" (="alpha"); "sufficient" (="bravo" in %]: marginal adaptation A 40/60/0 B 35/60/5 C 17/65/18 D 4/68/27 E 5/76/19 F 2/38/60; integrity inlay A 96/3/1 B 93/5/2 C 92/3/4 D 82/12/5 E 60/21/19 F 67/7/26; and integrity tooth A 84/16/0 B 90/9/1 C 78/21/1 D 53/41/6 E 34/64/2 F 18/70/12. Neither the absence of enamel margins, nor cuspal replacement significantly affected the adhesion or marginal quality of the restorations. No difference was evaluated for the following criteria [last recall, %]: surface roughness 81/19/0, colour 97/3/0, proximal contact 95/5/0, and hypersensitivity 100/0/0. Conclusion: IPS Empress® inlays and onlays bonded with Syntac® Classic were found to have a 92% survival rate after eight years of clinical service. Supported by Vivadent, Schaan, Liechtenstein.


1697 (19358)

Clinical performance of Experimental Glass-Ceramic Posterior Crowns: 3D Measurement of Clinical Wear. M.K. ETMAN*, T.F. WATSON, and M.J. WOOLFORD, Guy's King's St Thomas' Dental Institute, King's College, London University, United Kingdom

The clinical behavior of the newly developed all-ceramic systems in the posterior region of the mouth is relatively unknown. Objectives: This study reports the results of clinical evaluations of three ceramic systems {experimental hot-pressed ceramic (EC)1, Procera-AllCeram (PA)2 and metal ceramic (PFM)3}. Methods: A total of 90 posterior crowns were randomised into three groups equally in 48 patients. They were assessed at baseline following USPHS criteria and impressions were taken. Clinical images were taken after using a fluorescent dye to stain the surface changes in the crowns. Recalls were made at six-monthly intervals. The impressions were digitized using a UBM Microfocus Measurement System4. The digitized images were modelled as superimposable 3D colored surface images using 3D Scan-Surf software5. The amount of wear in the occlusal contact areas was quantitatively measured at 6, 12 and 18 months and statistically analysed using Univariate analysis of variance (Scheffe) test. Results: USPHS evaluation showed only visible wear in material PA at the region of occlusal contact with opposing teeth after 18 months, whereas EC and PFM did not alter clinically. Scheffe test showed a significant difference in the amount of enamel worn by all types of restoration over 18 months. The mean depth of enamel wear was 150mm (EC), 199mm (PA) and 124mm(PFM). There was no significant difference in the mean depth of wear of EC and PFM crowns. There was a significant difference between PA and the other two crown systems. The mean depth of wear in the restorations was 129.91mm (EC), 265.12mm(PA), and 129.89mm(PFM). Conclusions:The non-layered hot-pressed glass ceramic (EC) showed a comparable clinical performance with Procera-AllCeram (PA) crowns according to USPHS criteria, but significantly improved wear resistance. Enamel opposing EC showed less wear compared to PA.

1: Ivoclar-Vivadent, 2: NobelBiocare/Ducera, 3: Panadent/Ivoclar, 4: UBM Messtechnik, 5: 3DD Corp, USA.

 

 


1698 (19627)

Clinical investigation of ceramic inlays luted with an only light cured composite after 3 years. F. SCHAEFERS*, Private Dental Office, Hattorf, Germany, and C. KRANTZ, University of Goettingen, Germany

Objectives: Ceramic inlays have proved to be a long term solution to fill caries defects. Varying from standard clinical procedure there may be some advantages by luting the inlays with an only light curing composite instead of a dual curing composite. Purpose of the present study was to determine whether it is possible to have long term clinical success when luting the ceramic inlays with an only light curing universal composite. Methods: Teeth were prepared for loading with ceramic inlays. Empress I inlays (Ivoclar Comp., Liechtenstein) were performed in a commercial dental laboratory. Before luting rubberdam was placed. The inlays were etched with a 2% hydrofluoric acid for 2 minutes. Following Monobond S (Vivadent Comp., Liechtenstein), a silane coupling agent was used for 1 minute. After enamel etching the dentin bonding agent A.R.T. (Coltene Comp., Switzerland) was used. For luting the universal composite Z100 (3M Comp., USA) was chosen. The inlay was inserted with a special ultrasonic tip. After the inlay was in final position the composite excess could be removed in the absence of a curing process. Afterwards the inlays were light cured for 5 minutes using the Optilux 500 (Kerr Comp., USA)high output curing light with an energy of 700 mW/cm2. 53 restorations were performed between 4/97 and 8/98. The inlays were examined in 8/01 using modified Ryge criteria: Marginal integrity, margin dicoloration, postoperative sensitivity and fractures/failures, endodontic treatment. The decision was made using alpha (A), Bravo (B) and Charlie scores. Results: Marginal integrity A/B/C: 51/2/0; Marginal discoloration A/B/C: 53/0/0; Postoperative sensitivty A/B/C: 51/2/0; Fracture/Failure Yes/No: 0/53; Endodontic treatment Yes/No:2/51. The inlays show excellent results after 30 month. Conclusion: The use of an only light curing composite for adhesive luting of ceramic inlays seems to be a reliable clinical procedure. The restorations of this study should be reexamined after five and ten years.


1699 (20966)

The local biocompatibility of full ceramic crowns. S. REICH, S. HOLST, N. MUELLER, and S. STURM*, Friedrich-Alexander-University Erlangen-Nuremberg, Germany

Objective: The aim of this investigation was to examine whether there is a local inflammatory influence on the surrounding gingival tissues of adhesively luted full ceramic restorations. Methods: 20 Cerec crowns and onlays were placed in 13 patients using Syntac classic as dentine adhesive. Variolink Ultra (10 cases) and Tetric ceram (10 cases) were used as luting composites. After 6 month pocket depths, a gingiva index (Loe and Silness) and a plaque index (Silness and Loe) were measured. At the contact area between the restorations and the gingival tissues, Periotron measurements were taken - especially in the in the approximal regions. The results of the restored teeth were compared with respective measurements at reference teeth that were located according to split mouth design, whenever possible. For statistical analysis the Wilcoxon matched pairs signed rank test (p£ .05, two tailed) was used.

Results:

mean pocket depth

mesial [SD]

in mm

mean pocket depth

distal [SD]

in mm

Gingiva

index

Plaque

index

Periotron

measurement

restored teeth n=20

2.7 [0.47]

2.8 [0.44]

0.5 [0.6]

1.1 [1.1]

20.6 [16.0]

reference teeth n=20

2.5 [0.80]

2.7 [0.77]

0.4 [0.6]

1.1 [0.7]

21.2 [17.0]

The Wilcoxon matched pairs signed rank test at p£ .05 showed, that there were no statistical differences between the values of the restored teeth and the reference teeth.

Conclusion: In this investigation there was no clinical evidence, that full ceramic restorations cause clinically detectable inflammation on surrounding gingival tissues in comparison to respective reference teeth.


1700 (14182)

A Randomised 8-year Clinical Evaluation of 3 Ceramic Inlay Systems. M.K. MOLIN*, Umeå University, Umea, Sweden, and S.L. KARLSSON, Goteborg University, Sweden

Objectives: To evaluate the clinical quality of three different ceramic inlay systems, 20 patients were treated with one Cerec, one Mirage and one Empress inlay respectively, inserted in a randomly selected order in the lower jaw. All patients were also treated with one gold inlay. In total, 35 premolars and 45 molars were treated with inlays. Methods: The inlays were examined independently by two calibrated examinors immediately after luting (Ex 1), 1 year (Ex 2), 3 years (Ex 3), 5 years (Ex 4) and 8 years (Ex 5) after luting. The inlays were rated using the California Dental Association (CDA) quality evaluation system. Results: One gold inlay was replaced after 8 years due to caries. Altogether five Empress inlays, two Cerec inlays and two Mirage inlays had to be replaced due to fracture during the 8 years follow-up period. The examination showed that the mismatch of colour increased from 15% to 50% between Ex 1 and Ex 5 for all ceramic systems. The gold inlays and the ceramic inlays were registered slightly roughened in 30% and 23-53% respectively at Ex 5. For the ceramic inlays a visible evidence of ditching along the margin increased from 5% (Ex 1) to 80% (Ex 5), and an apparent discoloration of the margin between the tooth increased from 0% (Ex 1) compared to 55% (Ex 5). Conclusions: To conclude, 9 (15%) ceramic inlays were fractured during the follow-up period of 8 years. Based on the criteria of the CDA quality evaluation system 85% of the 60 ceramic inlays were rated "satisfactory" 8 years after luting.


1701 (14147)

Clinical Evaluation of Fiber-Reinforced Fixed Partial Dentures: Survival Data. M.A. FREILICH*1, J.C. MEIERS, J.P. DUNCAN, and A.J. GOLDBERG, 1 University of Connecticut School of Dental Medicine, Farmington, USA

Objectives: The purpose of this study was to evaluate the clinical performance of three-unit fixed partial dentures (FPD’s) made with pre-impregnated unidirectional fiber-reinforced composite (FRC). Methods: 39 light/heat polymerized, Sculpture™ /FibreKor™ FPD's were made with a single pontic and placed in 25 patients over 37 months. 22 extracoronal, full coverage retainer FPD's and 17 intracoronal, partial coverage retainer FPD's were evaluated. Prostheses were made with low volume (L-FRC) and high volume (H-FRC) substructures. Surface integrity (smoothness, chipping), anatomic contour, marginal integrity, structural integrity and various periodontal health indices were evaluated. SEM’s were made for representative sample prostheses. Results: Clinical survival was primarily associated with FRC substructure volume. Excluding subjects with severe parafunctional habits, 95% of all prostheses with the H-FRC substructures have survived for up to four years (3.7+ 0.1 years). This was significantly greater than the L-FRC prostheses survival rate of 62%. Retainer configuration did not have a significant influence on clinical survival time for the H-FRC prostheses. All surviving FPD's exhibited no or little change from baseline values for all clinical criteria. The surface integrity of all these prostheses was maintained and there was no chipping of the veneer except for two repairable surface defects that were not related to material failure. Conclusions: This study showed that a fiber-reinforced polymer prostheses (Sculpture™ /FibreKor™) can be used for successful short span fixed tooth replacement for up to four years when made with optimized substructure volume. This work was supported by NIH-NIDCR Research Grant DE-09126, Connecticut Innovations, Inc. and Jeneric/Pentron, Inc.


1702 (11062)

Primary endodontic therapy in a dental teaching hospital. F.M. BURKE*, C.D. LYNCH, R. NI RIORDAIN, B. LYONS, and F. RYAN, National University of Ireland, Cork, Ireland

Objectives: This study was to examine the profile and outcomes of primary endodontic therapy carried out by undergraduates at a dental teaching hospital. Methods: The sample for this study was patients who presented in the Casualty Department of the University Dental School and Hospital, Cork during the period 1993-5. The case notes for each patient were reviewed and demographic and dental factors, such as age, tooth type, and aetiology were recorded. Results: Care was provided by 78 students. There were 553 lesions in 477 patients. The age distribution of patients was; 10-19 years (36.3%), 20-29 years (35.1%), 30-39 years (13.9%), 40 years and over (14.7%). The most common aetiological factor was caries (63.3%) followed by periapical pathology (10.8%) and trauma (10.1%). Incisors were the most common tooth type treated (36.9%) followed by premolars (33.8%) and molars (29.3%). Subsequently 219 (40%) did not return to the University Dental School and Hospital for definitive endodontic therapy, 62 (11%) returned to have the tooth extracted, and 272 (49%) have not returned for any further treatment. 50% of incisors returned for definitive treatment, compared with 34% of premolars and 33% of molars (p<0.0001). 35% of lesions caused by caries returned for treatment compared to 52% of lesions caused by trauma (p<0.05). Conclusions: Undergraduates were more likely to carry out primary endodontic care on young patients with caries being the most common aetiological factor. Tooth type and aetiology influenced whether the patients returned for definitive endodontic care. The assistance of the Health Research Board, who provided funding for this project, is acknowledged.


1703 (15395)

Attitudes and confidence levels of dental students to performing Basic Life Support. J.M. FLETCHER*, and N.M. JEDYNAKIEWICZ, University of Liverpool, United Kingdom

Objectives: To determine possible changes in attitudes and confidence levels of dental students regarding Basic Life Support procedures over the five years of the dental curriculum.

Methods: The entire student cohort of the Liverpool Dental School was trained or retrained in methods of Basic Life Support (BLS). Immediately following training, each student was asked to complete an investigative questionnaire that scored their attitudes to performing BLS with regard to concerns about incorrect administration; potential legal action; the risk of infection and the aesthetic state of the victim. Perceived levels of confidence were also scored. Results were tested for significance using Kruskal-Wallis statistical procedures.

Results: 274 dental students (98%) replied. Concerns about incorrect administration reduced significantly as students progressed through the course (p<0.05) whilst concerns about potential legal action and the aesthetic state of the victim showed no significant change. Middle year students were more concerned about the personal risk of infection (p<0.05) than junior or senior years. There was no change in confidence levels during the course but females consistently scored less confidence than males (p<0.005).

Conclusions: Male dental students consistently showed greater personal confidence levels than females in their attitudes to performing Basic Life Support. Repeating the training each year of the course led to reduced concerns about incorrect administration.


1704 (21480)

The development and evaluation of computerized images for the study of Gross Anatomy. M. RUFO, N. KHRUSTCHEVA*, and C. ZEMNICK, Tufts University School of Dental Medicine, Boston, MA, USA

Objectives: To create and evaluate the effectivenes of computarized images which fascilitate student understanding of hard to vizualize concepts in Gross Anatomy. Methods: During the summer of 1999, a combination of images representing the relative positioning of the fascial spaces in the head and neck area was created. The images include photographs of the cadaver dissection, diagrams demonstrating relative positioning of fascial planes and spaces to one another, possible routes for the spread of infection, and photographs of relevant clinical cases. These images are now displayed on the Head and Neck web page of the Tufts University School of Dental Medicine Gross Anatomy web site (http://iris3.med.tufts.edu/headneck/index2.htm). The project was evaluated for its effectiveness through surveys of dental students conducted before and after the material was available. Two classes of dental students (D'2002 and D'2003) were surveyed after their completion of the Gross Anatomy course. Results: There was a 54% and 55% response rate of the D'2002 and D'2003 classes respectively. Class D'2002 did not have the computerized fascial images available to them, however class D'2003 did. It was found that 62% of the class D'2003 listed computerized images as the preferred method for studying fascial spaces vs. 3.8% of the class D'2002. Also 67.1% of the class of D'2003 thought that they were able to visualize the relative 3-dimentional positioning of the fascial spaces and their interconnection vs. 28.2% of the class of 2002. 51.9% of the class of 2003 listed diagrams as the most helpful feature on the Gross Anatomy web site vs. 25.6% of the class of 2002. Conclusions: These results prove that certain hard to visualize concepts in Gross Anatomy can be successfully presented via computerized images customized to the specific course curriculum. Computerized images can serve as a preferred study guide over many other conventional sources available to students.


1705 (18166)

Use of Faculty Evaluation Methods in U.S. Dental Schools. R.J. HUNT*, Virginia Commonwealth University, Richmond, USA

Objective: As Schools of Dentistry recruit increasing numbers of faculty members into nontenure track appointments, it becomes increasingly important for the retention of faculty that the schools have faculty performance evaluation methods that are appropriate to the differences in appointment tracks. The purpose of this study was to investigate the use of evaluation methods for tenure-track and nontenure-track faculty in U.S. dental schools.

Methods: As part of a larger investigation of faculty issues, 94% of 54 U.S. dental deans completed a mailed questionnaire about faculty evaluation methods. For analysis of survey results, 22 schools were arbitrarily classified as nontenure-emphasis on the basis of having more than 20% of the faculty in nontenure tracks, while the other 28 schools were classified as tenure-emphasis. Schools also were classified by funding source: 36 public vs. 15 private.

Results: Most schools use annual faculty review (90%) and dental student evaluation of teaching (85%), but fewer use post-tenure review (42%) or peer evaluation of teaching (52%). Teaching portfolios were widely used for promotion review (100%) and tenure review (97%), but less frequently used for annual review (44%) or post-tenure review (39%). The nontenure-emphasis schools were more likely to use peer evaluation (60% vs. 46%) and to require teaching portfolios (85% vs. 64%). All four types of schools (nontenure-emphasis, tenure-emphasis, public, private) were less likely to permit nontenure track faculty to participate in the review of other faculty, including the review of their faculty colleagues who are in similar nontenure tracks. This pattern occurred at the department, school, and university levels of performance review.

Conclusions: This study showed U.S. dental schools use a variety of methods for the evaluation of faculty performance, but nontenure track faculty do not have equal opportunity for participation.

Supported by ADEA, the W.J. Gies Foundation, and the University of North Carolina at Chapel Hill.


1706 (19812)

Personality Preference Distribution of Dental Students Admitted using a either Traditional or PBL Style Admission Process. H.A. WANG*, C.C. CHANG, K. DALRYMPLE, L. PEREIRA, A. FINCHAM, and C.F. SHULER, University of Southern California, Los Angeles, USA

A frequent criticism against Problem-Based Learning pedagogy to deliver the dental curriculum is that the students are not appropriately prepared in their pre-dental studies to succeed using PBL. We have reported previously that altering the admission procedures used to select students for a PBL parallel track can result in groups of students that more readily adapt to the pedagogy. Objective: To determine with the Myers-Briggs Type Indicator whether differences in the personality preference can be identified in first year dental students that are associated with the admissions process. Method: First year dental students admitted in 2000 and 2001 were all administered the Myer-Briggs Indicator during the orientation period prior to the start of classes. In Autumn 2000 the class had 140 students, 116 in the traditional track and 24 in the PBL track and in Autumn 2001 144 students all in the PBL curriculum. All students admitted to PBL had an admission process that included participation in a small group learning experience and observation of PBL sessions. Traditional students had individual interviews with faculty. Both student groups were required to meet the same GPA and DAT standards. Results: The personality preferences in 2000 had distinct differences between the PBL and traditional groups in the categories of Extroversion (89% PBL, 44% Traditional) and Thinking (72% PBL, 39% Traditional). In 2001 the all PBL class retained the trend towards Extroversion (69%) but had a majority in the Feeling category (54%) rather than thinking. Conclusion: The PBL style admission process can effectively change the personality preference distribution exhibited by the students who matriculate to dental school. A different distribution of student personality preferences can be associated with more successful transition to a PBL pedagogy. These results have been used to further develop a PBL style admission process for all student applications considered.


1707 (19819)

Comprehensive Assessment Measure to Monitor Student Acquisition and Retention of Curricular Learning Objectives. C.F. SHULER*, H.C. WANG, A. FINCHAM, and M.L. SNEAD, University of Southern California, Los Angeles, USA

Courses and curricular content have been organized to prepare students to meet the defined set of graduation competencies. Competencies capture a broadly based review of student abilities but do not identify mastery and retention of specific curricular learning objectives. Objective: To develop and administer a comprehensive assessment measure to dental students at different stages in their dental education and evaluate the acquisition and retention of the curricular content. Method: A 400 multiple-choice question examination was developed that containing content from Part I and Part II of the National Dental Boards. The 400 questions reflected the topic distribution published and distributed by the testing agency. The examination was administered to the students in the PBL parallel track. Newly matriculated students were examined during their orientation period. Upper class students were examined in either their second or fourth years of school. Examination scoring was one point for each correct answer and -0.25 point for each incorrect answer as a correction for guessing. The performance of students was compared both with respect to total score and score on either Part I or Part II content questions. Results: Newly matriculated students had a score average of 47 and fourth year students a score average of 326. Fourth year students had similar levels of performance on both Part I and Part II content areas. Second year students had an intermediate score heavily weighted by successfully answering Part I content questions. Conclusion: A comprehensive assessment examination can be used to monitor student retention of the curricular content. Fourth year students had excellent levels of performance on content from both the pre-clinical and clinical years of the curriculum. The examination is being administered on a yearly basis to all entering students who will be subsequently re-examined as they progress through the curriculum.


1708 (7260)

Convergence angle variation for full veneer crown preparations. A comparison between student and experienced operator groups. P.B. PATEL*, D.G. WILDGOOSE, and R.B. WINSTANLEY, University of Sheffield, United Kingdom

Objectives: To investigate the variation in convergence angle (CA) of posterior full veneer crown preparations between clinicians of different experience. Fourth and fifth year undergraduate students, clinical teachers (CTs) and general practitioners (GPs) took part. Methods: A total of 120 dies were examined in both mesio-distal (MD) and bucco-lingual (BL) planes, 30 dies per group. Dies were cast from impressions taken of clinical preparations for posterior full crowns, then trimmed and sectioned in both planes. An image of each die was projected onto a white board with an overhead projector. The axial walls of the silhouette were extended using a straight edge and the resultant angle measured with a protractor. Results: Fourth year students displayed the widest CA range (10°-62°) when comparing mean values. The degree of conformity to the ideal taper (4°-14°) was between 13% for fourth year students and 70% for GPs. The determinations of CA achieved by CTs showed 50% of BL surfaces and 35% of MD surfaces were within the prescribed range. Fourth year students showed a significant difference (p<0.05) for both MD and BL convergence angle to the other three groups. Fifth year students produced full veneer crown preparations of a taper achieved by CTs and GPs.

Group

BL

MD

BL

MD

 

Mean SD

Mean SD

Range

Range

Fourth year

24.23°± 11.23

27.03°± 15.00

11 - 51°

10 - 62°

Fifth year

14.67°± 5.04

16.33°± 5.82

6 - 24°

3 - 26°

GPs

14.33°± 7.02

16.33°± 5.82

8 - 36°

6 - 31°

CTs

17.08°± 10.39

16.77°± 6.98

0 - 44°

5 - 33°

Conclusions: The greatest CAs were produced by the least experienced students. However students with one year’s experience achieved convergence angles equal to experienced staff.


1709 (18174)

Development of Teeth for Teaching Esthetics: Knoop Hardness Values. P. MONAGHAN*1, M. PAGNOTTO2, L.T. LE2, R.R. SEGHI2, and R.A. RASHID2, 1 Marquette University, Milwaukee, WI, USA, 2 The Ohio State University, Columbus, USA

Teaching esthetic procedures preclinically poses significant problems as no suitable artificial tooth exists which effectively simulates natural tooth. Previously, we created esthetic teeth from and bonded composite resin to acrylic denture teeth (Mason, et al, and Le, et al, AADR, Chicago, 2001.) However, these teeth do not simulate natural teeth in preparation attributes or enamel bonding. Objective: This project focused on finding suitable materials to simulate dentin and enamel with respect to Knoop hardness which may work for adhesive bonding techniques. Methods: Eight materials {Kerr Prodigy [PRO], a BISCO light/heat cure composite resin [BIS], a denture tooth [DTH], three polyurethanes (unfilled [0FU], 20% glass filed [2FU], 75% glass filled [7FU]), Kilgore typodont tooth [KTT] and IPS Empress castable ceramic [EMP]} were tested for Knoop hardness and compared to the Knoop hardness of both human enamel [HEN] and dentin [HDN]. The Knoop biaxial, pyramidal diamond was stressed into the flat, metallographically polished specimens under a 25 g load for 15 s and the major axis of the indentation was measured at 40 X. Ten measurements were made on different specimens for dentin, enamel, and the experimental materials. These lengths were converted to Knoop hardness via calculation and compared to the dentin and enamel with a one-way ANOVA and the Dunnett method at 99% confidence. Results: Mean Knoop hardness values (SD) were: EMP 303 (39), HEN 281 (20), BIS 98 (14), KTT 86 (14), PRO 79 (17), HDN 55 (8), DTH 23 (2), 7FU 14 (1), 0FU 11 (1), and 2FU 10 (1). Though statistical difference was found between materials, by the Dunnett method, EMP was comparable to HEN and PRO was comparable to HDN. Conclusion: An Empress enamel shell covering a Prodigy core may yield an esthetic tooth which can simulate preparation and bonding aspects of human teeth.


1710 (14617)

Osteoporotic fractures and dental status in elderly. A.-M. BOLLEN*1, A. TAGUCHI2, P. HUJOEL1, and L.G. HOLLENDER1, 1 University of Washington, Seattle, USA, 2 Hiroshima University, Japan

Previous studies have suggested that generalized decreased bone quality (such as in osteoporosis) results in a decreased number of teeth in elderly subjects and increased residual ridge atrophy (RRA) in edentulous subjects. Improved bone metabolism resulting from hormone replacement therapy (HRT) was shown to have the opposite effects. Objectives: The purpose of this study was to evaluate whether a history of osteoporotic fractures was related to the number of teeth or residual ridge height in edentulous subjects. Methods: Patients from the University of Washington School of Dentistry, older than 60 years and with a panoramic radiograph were interviewed by phone (n=515). Information was obtained regarding fracture history, smoking, HRT and years of edentulism (if applicable). Teeth were counted on the panoramic radiograph. In edentulous subjects (n=93), residual ridge height was measured on the panoramic radiograph bilaterally at the site of the mental foramen. Results: Number of teeth was significantly dependent on smoking, age and gender. RRA was significantly dependent on age and gender. Fracture status (93 subjects reported osteoporotic fractures) and HRT (212 or 77% of the women were on HRT) did not significantly affect the number of teeth, nor the RRA. Conclusion: number of teeth and residual ridge atrophy in elderly dental school patients are more affected by age and gender (and smoking for number of teeth) than osteoporotic fracture history or hormone replacement therapy. Supported in part by DE09743.


1711 (17969)

Five Year Study on Parotid-Sparing Radiotherapy for Cancer. J.A. SHIP*, and R.N. LOPEZ, New York University College of Dentistry, USA

Salivary sparing radiotherapy (RT) has been used for 5+ years at the University of Michigan for head and neck cancers. Conformational dose-delivery techniques are able to minimize RT dosages to contralateral parotid glands while providing therapeutic dosages to tumors. Objectives: this cross-sectional study’s purpose was to provide a five year compilation of subjective and objective results from three RT studies. Methods: patients receiving unilateral (n=66; UN) and bilateral neck (n=99, BN) parotid-sparing RT and standard three beam bilateral neck RT (n=30; STD) were followed from the initiation of RT to 5 years post-RT. Unstimulated and stimulated parotid flow rates were collected from both parotid glands (spared and treated), and responses collected to three standardized xerostomia questionnaires. Results: RT dosages to treated glands were similar in all protocols (47, 55, 60 Gy; UN, BN, STD respectively), while different in the contralateral glands (4, 21, 60 Gy; UN, BN, STD respectively). Median flow rates from spared glands were initially inhibited, and became greater than pre-RT values 2 years post-RT in the UN and BN protocols. Conversely, flow rates from bilateral glands in the STD protocol remained essentially zero post-RT for the duration of the study. Xerostomia levels increased after RT until 6 months post-RT in all three protocols, and then gradually improved in the UN and BN protocols while remaining elevated in the STD protocol. Xerostomia-related quality of life also worsened up to 6 months post-RT in all three protocols. Values returned towards pre-RT values in the UN and BN protocols, yet remained higher in the STD protocol compared to the UN and BN protocols over time. Conclusions: these results demonstrate the long term preservation of salivary function and reduction of xerostomia in cancer patients receiving parotid-sparing RT techniques.


1712 (21130)

Periodontal attachment loss, tooth loss and CHD status. J.D. BECK*, J. ELTER, and S. OFFENBACHER, University of North Carolina, Chapel Hill, USA

Objective: Some studies have shown positive associations between periodontal and heart diseases, while others have shown non-significant trends. The Atherosclerosis Risk in Communities Study, which conducted oral examinations from 1996-1999 on 6,796 ARIC participants aged 52-74 from four US communities, had previously reported significant associations between extent of attachment loss of 3+mm (EAL) and ultrasound measures of carotid atherosclerosis, but the trends with prevalent CHD status were not significant. Objective: Since tooth loss(TL) could be a proxy indicator of a history of serious periodontitis, caries or other conditions, we sought to clarify the relationship between EAL, TL and CHD status. Methods: The distributions of EAL and TL were dichotomized at ³10% of sites (HighEAL) and >16 missing teeth (HighTL) forming 4 groups; LowEAL&LowTL (LL); LowEAL&HighTL (LH); HighEAL&LowTL (HL); and HighEAL&HighTL (HH). Results: The mean percent of sites with EAL in each group was LL=3.8%; LH=4.8%; HL=28.7%; HH=48.9%. The HH group had significantly greater EAL than the other groups (p<0.0001) and the LH and LL groups were not different (p=0.29). The prevalence of CHD was LL=8.3%; LH=9.5%; HL=8.8%; HH=12.1%. The HH group had significantly more CHD than the LL and HL groups (p<0.003), but not the LH group. The LH and LL groups were not different. In a multivariable logistic model, the HH group had greater odds of CHD (OR=1.5, 95%CI=1.2-2.0) adjusting for ARIC race/center, gender, age, education, hypertension, diabetes, LDL, HDL, BMI, and smoking. Conclusions: Those with extensive EAL and TL were more likely to have CHD. However, TL in the presence of low levels of EAL was not associated with higher odds of CHD, indicating that tooth loss in the absence of periodontal disease was not associated with increased risk for CHD.


1713 (20393)

Association between markers of periodontal status and c-reactive protein. E.M. GHEZZI*, R.S. LEVY, S. OFFENBACHER, G.D. SLADE, and J.D. BECK, University of North Carolina, Chapel Hill, USA

Moderately elevated serum C-reactive protein (CRP) is a systemic marker of inflammation and is a documented risk factor for cardiovascular disease in otherwise-healthy persons. However, the cause of this systemic inflammatory response in the absence of systemic disease has not been determined. A number of epidemiologic and clinical investigations have implicated periodontal disease in this association. Objectives: The purpose of this study was to evaluate the association between periodontal status and CRP levels among adults in the Atherosclerosis Risk in Communities (ARIC) study. Methods: Oral examinations were conducted in 1996-1999 on 6,796 ARIC participants aged 52-74 yrs from four U.S. communities. The outcome, elevated serum CRP measured using an ELISA assay for 5,374 subjects, was dichotomized as <15 or ³ 15 mg/L. Four measures of periodontal status were recorded around all teeth: gingival index (GI), gingival bleeding on probing (GB), periodontal pocket depth (PD), and periodontal attachment level (AL). Extent scores were computed indicating the percent of sites with: GI of 1+; GB; PD of 4+mm; and AL of 4+mm. Results: The crude odds ratio (OR) for the association between GI (dichotomized at £ 50% versus >50% of sites affected) and elevated CRP was 1.5 (95% CI=1.2-1.8). In a multivariate logistic regression model that controlled for race/study center, sex, and diabetes, the effect of GI was modified by exposure to cigarettes: compared with the reference group of non-smokers with GI £ 50%, the OR for GI >50% among non-smokers was 1.3 (95%CI=0.9-1.7), but the OR for joint effects of GI >50% and smoking was 2.7 (1.8-4.0). Other measures of periodontal status were not significantly associated with elevated CRP. Conclusions: In the ARIC population, GI and smoking were jointly associated with significantly increased odds of elevated CRP.


1714 (17804)

Toothloss and ischemic heart disease. M. HAKEBERG*, C. BENGTSSON, M. AHLQWIST, U. NYMAN, and F. FRISK, Göteborg University, Sweden

During the past decade several studies have shown positive associations between different markers of dental and cardiovascular diseases. However, these results are far from being reliable, thus more epidemiological and clinical evidence is needed. Objectives: The aim of this study was to analyze the relationship between ischemic heart disease (IHD) and toothloss. Methods: In 1992-93, a representative sample (N=1017) of women aged 38 to 84 years in Göteborg, Sweden were examined with regard to their general and dental health. In this analysis, the dependent variable was ischemic heart disease diagnosed in women with angina pectoris and/or a history of myocardial infarction (N=106). The independent variables included were age, marital status, smoking, alcohol habits, body-mass index, waist-hip ratio, serum cholesterol and triglycerides, hypertension, diabetes, and toothloss. Toothloss served as an indicator of oral disease burden over time and consisted of three categories; edentulous (E) N=126, < 17 teeth (HTL) N=245, 17 or more teeth (LTL) N=622. Results: Bivariate odds ratio (OR) between IHD and toothloss, and IHD and age were 3.20 (LTL vs E), 3.34 (LTL vs HTL) and 1.10, respectively. In a multivariable logistic regression IHD was statistically significant associated with age (OR 1.08, CI 1.04 - 1.13), serum triglycerides (OR 1.45, CI 1.11 - 1.90) and toothloss (OR 2.38 for HTL vs LTL, CI 1.42 - 3.97). However, HTL vs E was not significant (OR 1.84, CI 0.96 - 3.52). Conclusion: The results show that a high oral disease burden over time has a postive association with ischemic heart disease as measured by angina pectoris and/or myocardial infarction among middle-aged and elderly women. In addition, higher toothloss may indicate an ongoing chronic oral disease as opposed to edentulousness.


1715 (21126)

Intraoral tactile sensitivity in adults with Diabetes mellitus. R.S.A. SHINKAI*1, J.P. HATCH2, J.E. CORNELL3, and C.-K. YEH2, 1 Pontificia Universidade Catolica do Rio Grande do Sul, Porto Alegre, Brazil, 2 University of Texas Health Science Center, San Antonio, USA, 3 UTHSCSA, San Antonio, TX, USA

Diabetes mellitus(DM) can lead to peripheral sensory impairment, yet the relationship between DM status and intraoral tactile sensitivity (ITS) has not been studied. Objectives: This study compared the ITS in diabetic and non-diabetic subjects as a function of demographic variables at three intraoral sites. Methods: The sample comprised 655 participants of the project Oral Health: San Antonio Longitudinal Study of Aging. Classification of DM status used the American Diabetes Association criteria. ITS was assessed with the Oral MicroAesthesiometer (Neurocommunication Research Laboratories, Danbury, CT) with a direct scaling procedure (Weiffenbach et al., 1990). The dependent variable was the individual slopes of the psychophysical function relating physical stimulus intensity to subjects' intensity judgments. Data were analyzed using ANOVA for repeated measures with between subjects factors being Age (<65 vs. >65), Gender (Females vs. Males), Ethnic Group (Mexican-Americans vs. European-Americans), and DM (Yes vs. No), and the within subjects factor being Intraoral Site (Anterior Tongue AT vs. Posterior Tongue PT vs. Soft Palate SP). Results: Demographic variables were not significantly related to ITS (p > 0.050). The main effect for sites was statistically significant (p=8.86 x 10-7). The means ± SE were: 0.22±0.01 for AT, 0.23±0.01 for SP, and 0.27±0.01 for PT. The only significant effect involving Diabetes was the significant Site x Age x Diabetes interaction (p=0.035). Young Diabetics had significantly greater tactile sensitivity at PT (0.31±0.03) compared to Old Diabetics (0.23±0.02). There was no association of ITS and duration of DM for any site. Medications and other conditions were not controlled. Conclusions: These results suggest that DM may not directly influence intraoral tactile sensitivity. Supported by NIH/NIDCR P50DE10756 and CAPES/Brazil BEX 0807/99-0.


1716 (15797)

Health-related quality of life in Sjögren's syndrome. A.S. MCMILLAN*1, K.C.M. LEUNG1, M.C.M. WONG2, W.K. LEUNG1, C.S. LAU1, and T.M.Y. MOK1, 1 University of Hong Kong, Hong Kong, 2 The University of Hong Kong, Hong Kong

Sjögren’s syndrome (SS) is an autoimmune disease of the exocrine glands, notably the salivary and lacrimal glands, that affects 3-4% of the adult population. The objective was to measure health-related quality of life (HRQOL) in SS patients using a disease specific dry mouth questionnaire, the oral health impact profile (OHIP-49), and the SF-36 instrument. 51 SS patients, 26 primary (1º) and 25 secondary (2º) cases, diagnosed at least 1 year previously took part. 29 age and gender-matched controls also completed the questionnaires. The number of subjects reporting negative impacts for the 7 dry mouth questions and individual OHIP statements and sub-scales were calculated. SF36 data were transformed and sub-scale scores calculated. Chi-square/ANOVA tests were used to compare differences among respondents reporting negative impacts for dry mouth-related questions, OHIP statements and OHIP and SF36 sub-scale scores, between groups. There were significant differences in 3 dry mouth scores (general feeling of dry mouth, dry mouth during eating/speaking, sticky saliva), p<0.05. The mean OHIP sub-scale scores were generally quite low with no statistical difference between groups. There were significant differences in mean SF36 sub-scale scores (physical function, role-physical, general health) between groups (p<0.05). There were no differences in dry mouth and SF-36 scores between 1º and 2º SS cases. HRQOL was significantly impaired in SS patients, with similar impact in 1º and 2º cases. OHIP appeared to lack the sensitivity to discriminate oral HRQOL between groups. Supported by CRCG-HKU


1717 (10802)

Pessimism and one year survival in head and neck cancer. P.J. ALLISON*1, K. FUNG1, C. GUICHARD2, and L. GILAIN2, 1 McGill University, Montreal, Canada, 2 Centre Hospitalier Universitaire, Clermont Ferrand, France

Objectives: The study aim was to investigate the hypothesis that, independent of other known prognostic factors, pessimistic head and neck (H&N) cancer patients have a greater risk of being dead one year after diagnosis than do optimistic patients. Methods: A prospective observational study design was used with a cohort of H&N cancer patients diagnosed during the period March 1st 1997 to August 31st 1998 at the Centre Hospitalier Universitaire, Clermont Ferrand, France. Dispositional optimism (DO) was evaluated at baseline using a French version of the Life Orientation Test translated and validated for this study. One-year survival status was collected on all subjects. The analysis of the hypothesised association between DO and one-year survival was performed using multiple logistic regression analysis, controlling for other known prognostic factors. Results: The sample size was 101, representing all but one of those patients fitting the inclusion criteria diagnosed during the recruitment period. Of these, 51 were alive at one-year following diagnosis, 45 were dead and 5 were lost to follow-up. The multivariate analysis was performed in the 96 subjects in whom one-year survival status was known. Pessimistic subjects had greater odds for being dead at one year compared to optimistic subjects (OR: 4.1; 95%CI: 1.3-12.7). Conclusions: The results of this study suggest that, controlling for other known prognostic factors, pessimistic H&N cancer patients are more likely to be dead one year following diagnosis than their optimistic peers. Supported by Cooperation France-Quebec.


1718 (8505)

Comparative analysis of collagen membranes for the treatment of implant dehiscence defects. T.-J. OH*, S.J. MERAW, E.-J. LEE, W.V. GIANNOBILE, and H.-L. WANG, University of Michigan, Ann Arbor, USA

Objectives: This study was aimed to clinically and histomorphometrically compare two collagen membranes, Bio-Gide® and BioMend ExtendTM for the treatment of implant dehiscence defects in 8 mongrel dogs. Methods: Implant dehiscence defects were surgically created in edentulous ridges, followed by the placement of 3 endosseous implants bilaterally in the mandible. Each implant dehiscence defect was randomly assigned to one of 3 treatment groups: (1) Control (no membrane), (2) Porcine dermis collagen barrier (Bio-Gide®), or (3) Bovine tendon collagen barrier (BioMend Extend TM). Dogs were sacrificed at 4 and 16 weeks (4 each) after treatment. Histomorphometric analysis included % linear bone fill (LF), new bone-to-implant contact (BIC) and area of new bone fill (BF). Results: The results of the study revealed no significant differences among groups for any parameter at 4 weeks. However, at 16 weeks, more LF, BIC, and BF were noted in the membrane-treated groups than controls. BioMend ExtendTM – treated defects demonstrated significantly greater BIC than control (p < 0.05) at this time point. BIC at 16 weeks was significantly greater than 4-week BIC (p < 0.05). Membrane exposure occurred in 9 out of 15 sites examined, resulting in significantly less LF and BIC than the sites without membrane exposure (p < 0.05). Conclusions: The study concludes that: (1) GBR treatment with collagen membranes may significantly enhance bone regeneration, manifested at the late stage (16 weeks) of healing; and (2) Space maintenance and membrane coverage were the two most important factors affecting GBR using bioabsorbable collagen membranes.


1719 (20892)

Maxillary sinus floor elevation using a combination of bovine-derived bone mineral (Bio-Oss) and collagen membrane (Bio-Gide) for implant placement. C.E. FERREIRA*, and V.I. HARASZTHY, Vittoria, Brazil

Objective: The aim of the present study was to evaluate bone formation following maxillary sinus augmentation using natural bone mineral of bovine origin and a collagen membrane by means of clinical and histologic examination. Materials and Methods: A total of 71 sinus floor elevation procedures were carried out on 63 patients, according to the technique described by Tatum. The sinus cavity was augmented using bovine bone mineral (Bio – Oss, Osteohealth), covered with a collagen membrane (Bio-Gide, Osteohealth). Eight cases with residual bone >5 mm had the implants placed simultaneously with the sinus elevation. The rest of the cases had the implants placed 9-11 months after the sinus elevation. After the healing period, all patients were asked to take CT scan and panorex. At this time, a bone biopsy core (7-mm length and 3 mm diameter) was harvested from the lateral window of seven patients. Specimens were demineralized with 7,5% nitric acid for 12-24h. The samples were washed, dehydrated, infused with paraffin, and embedded. Sectioning to a thickness of 5 mm was prepared and stained with hematoxylin-eosin. Eighty-one implants were placed into the augmented sinuses. The final restoration was performed 3 months after the healing abutments were connected. Results: In three cases small residual defect remained, but did not require any further graft. The remaining procedures resulted in statistically significant bone gain (8-20 mm) as determined by CT scan and panorex. New bone formation was confirmed in biopsies of seven patients. The histology showed almost mature bone and marrow space in close contact with Bio-Oss particles. All the 81 implants were fully loaded (4-36 months) and remained clinically stable (100% success rate). Conclusion: This study indicates that deproteinized bovine bone, when used as a grafting material for augmentation of the sinus floor, may lead to proper osseointegration of a dental implant.


1720 (11362)

A clinical and histomorphometric analysis of perforating the maxillary sinus membrane during sinus grafting procedure. P. PROUSSAEFS*, J. LOZADA, A. KLEINMAN, and J. KIM, Loma Linda University, CA, USA

Objectives: The purpose of the study was to determine the results of perforating the maxillary sinus membrane (MSM) during sinus grafting (SG). Methods: A split-mouth design was followed in the current study. 5 human subjects (mean age: 64.2)were included and all recieved bilateral SG. In one side the MSM was accidentally perforated during surgery while the other was non-perforated (NP). The perforated site was repaired with a collagen membrane. Inorganic bovine mineral (IBM) alone or in combination with demineralized freeze dried bone allograft was used as graft material. Healing period was 8-15 months (mean: 9.4, SD: 1.6). Biopsies were taken from both sites during implant placement. Histologic and histomorphometric analysis was performed. The percentage of bone, soft tissue, residual graft material (RGM), and the percentage of the surface of IBM in direct contact with bone were recorded. Bone quality (I-IV) was recorded during implant placement and the implant survival rate was recorded at the second stage surgery (SSS). The Mann-Whitney U-Test was used to evaluate the data from histomorphometric analysis between perforated and NP sites. Two-sample test for binomial proportions was used to compare implant survival at SSS. Results: The perforated site had 12.80 % bone formation, 63.00 % soft tissue, 24.20 % RGM, while 16.00 % of IBM surface was in contact with bone. The corresponding numbers for NP sites were 34.40 %, 53.80 %, 12.40 %, and 40.80%. NP sites had significantly more bone formation (p=0.016). NP sites had significantly better (p=0.0146) implant survival rate at SSS (100 % vs 54.5%). Type IV bone quality was typically observed in perofrated sited (4 cases) while in NP sites type II (2 cases) or III (2 cases) was seen. Conclusion: Perforation of MSM during SG offers reduced bone formation and implant survival rate.


1721 (11687)

Labial / buccal localized alveolar ridge augmentation with the use of a resorbable collagen membrane. P. PROUSSAEFS, J. LOZADA, and E. GRAGEDA*, Loma Linda University, CA, USA

Objectives: The purpose of the current study was to evaluate the use resorbable collagen membrane for labial / buccal alveolar ridge augmentation (LBARA). Methods: 5 consecutively treated human subjects (mean age: 58.6) participated and all received LBARA before placing dental implants. Autogenous bone graft harvested from the chin (4 cases) or ascending ramus area (1 case) was used and mixed with inorganic bovine mineral (IBM). Collagen membrane was placed above the graft. The graft was allowed to heal for 6-14 months (mean: 8.0, SD: 3.46). Alginate impressions were made preoperatively, 1, and 6 months after bone grafting.Post-operative stone casts and custom acrylic resin trays were used to assess the post-operative LBARA according to a technique developped at LLU. Laboratory analysis provided volumetric and linear analysis of LBARA. During implant placement, biopsies were taken to perform histomorphometric analysis and type of bone quality (I-IV) was recorded. Periapical radiographs and tomographs were taken before the bone grafting and before implant surgery. Results: No complication at any of the cases was noticed. Type II (3 cases) or II (2 cases) bone quality was recorded. Volumetric laboratory analysis revealed average 1.27 cc (SD: 0.23) and 1.08 cc (SD:0.21) LBARA 1 and 6 months after bone grafting respectively. Linear laboratory measurements revealed 4.8 mm (SD: 0.45) of labial/facial ridge augmentation 1 month after bone grafting and 4.2 mm (SD: 0.83) 6 months after bone grafting. This revealed 14.96 % resorption. Histomorphometric analysis indicated bone present at 32.4% (SD: 10.14), soft tissue at 47.4 % (SD: 10.16), residual IBM particles at 20.2 % (SD: 14.24, while 47.0 % (SD: 19.72) of the surface of the residual IBM particles was in direct contact with bone. Radiographic analysis revealed 4.8 mm (SD: 0.84) of LBARA. Conclusion: Resorbable collagen membranes may be used for labial/buccal alveolar ridge augmentation


1722 (21837)

Structure-Activity Relationship of a Novel Synthetic Osteoblast Adhesive Peptide. D. MACDONALD*1, S. VYAS2, and B. RAPUANO2, 1 VA Medical Center/Columbia University, Bronx, NY, USA, 2 Hospital for Special Surgery, New York, NY, USA

We have previously shown that biomimetic peptides from human bone sialoprotein (hBSP) containing the integrin-binding tripeptide RGD (Arg-Gly-Asp) can promote the adhesion of osteoblasts to untreated artificial surfaces. The purpose of this investigation was to study the in vitro adhesive activities toward an osteoblast-like cell line (MC3T3-E1) of several novel fragments of hBSP that contain the RGD core domain but are missing single or multiple residues from the N or C-terminal regions of the parental molecule (containing residues 278-293 from hBSP). The hBSP peptides containing residues 281-293 (DB1), 278-290 (DB2), 279-293 (DB3), 278-292 (DB4), 279-292 (DB5) and 278-293 were coated on polystyrene surfaces in 96-well nontissue (untreated) culture plates and their osteoblast adhesive properties were tested and compared. At a concentration of 25 uM hBSP, peptides 281-293 (DB1) and 278-290 (DB2), respectively, only retained 10 % and 35 % of the adhesive activity of the parental molecule. Peptides missing either the N-terminal tyrosine (DB3) or both the N and C-terminal tyrosines (DB5) lost nearly all of the adhesive effects at concentrations from 1 to 25 uM. In contrast, peptide 278-292 (DB4) retained full adhesive activity of the parental molecule. It was also shown that 60-70 % of the peptide-stimulated adhesion promoted by peptide 278-292 could be inhibited by the pretreatment of cell suspensions with solution phase RGD. This latter finding suggests that a portion of this peptides' adhesive effects was specific and integrin-mediated although other non-RGD flanking regions were probably also involved in the mechanism of adhesion. These results demonstrate that a tyrosine residue present at the N-terminus of hBSP peptides is critical for their adhesive effects toward osteoblasts. This study has shown that synthetic cell adhesive peptides modeled after RGD-containing sequences of extracellular matrix proteins can be identified and possibly modified by the addition of tyrosine residues in order to promote optimal bioactivity in vitro, useful as potential biomimetic tools for enhancing implant osseointegration. Supported by VA Merit Grant 2894-005


1723 (16328)

Fabrication of 3D Tissue Analogs: Cell Viability and Plasmid Stability, and Distribution. W.-Y. CHAN*1, C. SUKOTJO2, I. NISHIMURA3, and B. WU1, 1 Henry Samueli School of Engineering and Applied Science, UCLA, los angeles, CA, USA, 2 The Jane and Jerry Weintraub Center for Reconstructive Biotechnology, School of Dentistry, UCLA, Los Angeles, CA, USA, 3 UCLA, Los Angeles, CA, USA

The long-term aim of this project is to derive the engineering design rules for fabricating the three dimensional tissue analogs, such as oro-facial complex, with controlled spatial distribution of multiple cell types, and controlled microenvironment for promoting proper cell differentiation. Objective: To determine ink-jet printing parameters that maintain cell viability and plasmid (pDsred) stability, and to determine the partitioning effects of substrate material on plasmid distribution. Methods: 5 x 107 cells/ml NIH3T3 fibroblasts were jetted in continuous-mode through a 68mm ceramic nozzle at 15 psi; and in a drop-on-demand-mode through a piezo-driven 70mm capillary microdroplet generator under a range of computer-driven waveform parameters (pulse amplitude, duty cycle, frequency). Cell viability was assessed with CalceinAM and Ethidium homodimer-1 stain and quantitative image analysis. 60 mg of CMV-LUX, 1.6 mg of 3xflag-CMV2, and pDsred plasmids were jetted and their structural integrity was analyzed on an agarose gel and compared to unjetted plasmids. In vitro transfection of pDsred into NIH3T3 fibroblastic cells was performed to confirm plasmid functionality. Plasmid pDsred stability over time at 25°C and 37°C, and plasmid distribution in the presence of collagen and PLGA scaffolds were inspected. Results: Cells printed in continuous-mode maintained 82±3% viability as compared to the positive controls (88±4% viability; p~0.17). Cells printed in drop-on-demand-mode only maintained a 23±7% viability compared to the controls (96%±1% viability; p<0.005). No difference was visible between the printed and unprinted plasmids. pDsred was not detected in the presence of PLGA at 37°C, but was detected at 25°C and at both temperatures in the presence of collagen. NIH3T3 cells fluoresced red in the cytoplasm after transfection with pDsred. Conclusion: Cell viability and plasmid stability was maintained after printing in the continuous-jet-mode, which aids in the design of a printer to ultimately print cells, signals, and matrix in an organized manner.


1724 (19953)

Evaluation of aBSM as a Candidate Carrier for rhBMP-2 in Alveolar (Peri-implant) Applications in the Dog. U.M. WIKESJÖ*1, R.G. SORENSEN2, A. KINOSHITA3, and J.M. WOZNEY2, 1 Temple University School of Dentistry, Philadelphia, PA, USA, 2 Genetics Institute/Wyeth-Ayerst Research, Cambridge, MA, USA, 3 Tokyo Medical and Dental University, Japan

Objectives: Recombinant human bone morphogenetic protein-2 (rhBMP-2) in a carrier has been shown to support significant alveolar bone formation. Several rhBMP-2 candidate carriers, however, lack structural integrity to offset compressive forces that may compromise rhBMP-2 bone induction, in particular for onlay indications. The objective of this pilot study was to evaluate a calcium-phosphate cement, aBSM, as a rhBMP-2 candidate carrier for alveolar augmentation and dental implant fixation.

Methods: Six, adult Hound Labrador mongrel dogs with 5-mm, critical size, supraalveolar peri-implant defects were used. Three animals received rhBMP-2/aBSM (rhBMP-2 at 0.40 and 0.75 mg/mL) in contralateral jaw quadrants (total implant volume/defect defect ~1 mL). Three animals received aBSM without rhBMP-2 (control). The animals were euthanized at 16 weeks postsurgery and block biopsies were processed for histologic and histometric analysis.

Results: rhBMP-2/aBSM induced substantial new bone formation in support of the dental implants. Control sites exhibited wound failure, exposure, loss of aBSM, and hence limited new bone formation. New bone height averaged (± SD) 4.9 ± 1.0 (rhBMP-2 at 0.40 mg/mL), 5.3 ± 0.7 (rhBMP-2 at 0.75 mg/mL), and 0.4 ± 0.6 mm (control); new bone area 8.5 ± 5.2, 9.0 ± 5.9, and 0.4 ± 0.7 mm2; new bone density 55.1 ± 14.6%, 61.1 ± 11.4%, and 69.8 ± 12.3%; and new bone-implant contact 26.6 ± 16.4%, 28.5 ± 11.1%, and 24.6 ± 30.6%, respectively. Residual aBSM comprised <1% of the rhBMP-2 induced bone. Bone density for the contiguous resident bone ranged from 65.1 ± 24.4% to 71.3 ± 12.1% and bone-implant contact from 48.6 ± 21.8% to 64.0 ± 9.6%.

Conclusions: aBSM appears an effective rhBMP-2 carrier for alveolar augmentation onlay procedures and to support immediate dental implant fixation.


1725 (21339)

Implant-Specific Gene Transfer for Tissue Engineered Bio-Integration. T. OGAWA*1, C. SUKOTJO1, S.-W. KIM2, and I. NISHIMURA1, 1 The Jane and Jerry Weintraub Center of Reconstructive Biotechnology, School of Dentistry, UCLA, Los Angeles, CA, USA, 2 School of Engineering and Applied Science, UCLA, Los Angeles, CA, USA

The potential use of gene therapy in wound healing and repair has increased with recent advances in gene transfer technology. Especially, non-viral gene delivery is emphasized useful for its less side effects. We previously identified the genes, TO1, TO2, TO3, that are specifically expressed in response to implants but not in simple wound healing or remodeling of bone. We hypothesized that molecules encoded by these genes hold keys in generating and promoting the process of tissue-implant integration. Objective: To develop a recombinant plasmid DNA transfer system of the implant-specific genes for modulating and accelerating tissue-implant integration. Methods: TO3, one of the implant-specific genes, was utilized to develop the system. A coding sequence of the rat TO3 gene was cloned into TA vector and subcloned into a 6.4k-basepair eukaryotic expression plasmid. The plasmid contained a promoter-regulatory region of human cytomegalovirus and drove a transcription of FLAG-fusion peptide constructs. In vitro assay was used to test transfection potential of the plasmid vector. NIH3T3 cells were seeded at 1x104/cm2 24 hours before transfection, and the plasmid DNA combined with cationic lipid agent was added. 24 hours after the transfection, the cells were harvested and subject to immunocytology and western-blot analyses. Results:Immunocytology showed that the cells were transfected successfully exhibiting stained cytoplasma and cell membrane. Transfection efficiency was 41.4%, 55.7% and 37.7% for the plasmid DNA concentration of 0.25 µg/cm2, 0.5 µg/cm2 and 0.75 µg/cm2, respectively. Western blot analysis of cellular protein extracts using anti-FLAG monoclonal antibody confirmed a synthesis of the recombinant peptide. Conclusion: The implant-specific gene fusion peptide can be synthesized using a non-viral plasmid DNA transfer protocol. This system will be useful to characterize roles of implant-specific genes and open the possibilities of in vivo targeted gene delivery for tissue engineered bio-integration.


1726 (10458)

Extracellular Nucleotides Activate Nuclear Factor k B in Mammalian Osteoclasts. L.N. NAEMSCH, S.M. SIMS, and S.J. DIXON*, The University of Western Ontario, London, Canada

Objectives: The transcription factor nuclear factor k B (NF-kB) is essential for osteoclast formation. Extracellular nucleotides activate P2 receptors, which are subdivided into two families: P2X (ligand-gated cation channels) and P2Y (G protein-coupled receptors). The aim of this study was to determine whether P2 receptors signal through NF-kB in osteoclasts.

Methods: Osteoclasts were isolated from long bones of neonatal rabbits. Immunofluorescence was used to stain for the p65 subunit of NF-kB, which upon activation translocates from the cytosol to the nucleus.

Results: In vehicle-treated samples, 7 + 2% of osteoclasts demonstrated nuclear localization of p65. In contrast, exposure to benzoyl-benzoyl-ATP (BzATP, a relatively potent P2X7 agonist) or UDP (a P2Y6 agonist) for 3 h induced nuclear translocation of NF-kB in 46 + 2% and 34 + 5% of cells, respectively, indicating that nucleotides activate NF-kB in osteoclasts. Interestingly, ATP (an agonist at several P2 receptors), 2MeSADP (a P2Y1-selective agonist) or UTP (a P2Y2 and P2Y4 agonist) did not induce nuclear translocation of p65. To examine the relationship between cytosolic free calcium concentration ([Ca2+]i) and activation of NF-kB, fura-2 fluorescence was used to monitor [Ca2+]i in single osteoclasts. All of the nucleotides tested induced a transient rise of [Ca2+]i, indicating that elevation of [Ca2+]i alone is not sufficient to activate NF-kB. To examine the possible involvement of receptor activator of NF-kB (RANK) ligand, osteoclasts were pretreated with osteoprotegerin (OPG), a decoy receptor for RANK ligand. OPG inhibited activation of p65 by RANK ligand, but not by BzATP or UDP, establishing that nucleotide-induced translocation of NF-kB does not involve RANK ligand.

Conclusions: Specific subtypes of P2 nucleotide receptors are coupled to activation of NF-kB in osteoclasts. Thus nucleotides, released at sites of inflammation or in response to mechanical stimuli, may act through NF-kB to regulate osteoclast formation and activity.


1727 (16507)

Cathepsin-K Activity in Osteoclasts from Rabbit Long Bones and Scapulae. S.S. CHATTHA*, S. SHOREY, and J.N.M. HEERSCHE, University of Toronto, Mississauga, Canada

Objective: Current data suggests that long bone (endochondral bone) osteoclasts utilize cathepsin-K to a greater extent during bone resorption than calvarial (intramembranous bone) osteoclasts. The purpose of this study was to confirm and extend these studies by evaluating the effects of a cysteine protease inhibitor (E-64), on resorptive activity of endochondral and intramembranous bone osteoclasts. Methods: Osteoclasts from long bone and scapula of newborn New Zealand white rabbits were isolated and cultured on bovine bone slices for 48 hours in a-minimal essential media in the presence and absence of E-64 (40 mM) at 37oC in humidified air containing 5%CO2. After 48 hours, the cells were fixed and stained with tartrate-resistant acid phosphatase (TRAP). Resorption activity was quantified by measuring surface area of lacunae immunostained using anticollagen type I antibody. Results: The resorbed area in E-64 treated and control long bone osteoclasts was 1118.97 mm2/osteoclast and 2768.98 mm2/osteoclast respectively. Resorbed area for E-64 treated and control scapula osteoclasts was 956.72 mm2/osteoclast and 1166.84 mm2/osteoclast respectively. Thus, E-64 treatment of long bone osteoclasts resulted in a 60% reduction (n=6, p<0.05) and for scapula osteoclasts only an 18% reduction (n=6, p<0.01) in surface area resorption per osteoclast. Conclusions: These results provide further evidence that long bone osteoclasts use cathepsin K to a greater extent during bone resorption than do osteoclasts from scapula. Supported by the Faculty of Dentistry and by CIHR grant # MT-15654.


1728 (10029)

Interaction between Vacuolar H+-ATPase and Microfilaments in Osteoclasts is Regulated by Phosphatidylinositol 3-kinase. L.S. HOLLIDAY*1, S.-H. CHEN1, M. LU2, and S.L. GLUCK2, 1 University of Florida College of Dentistry, Gainesville, USA, 2 University of Florida College of Medicine, Gainesville, USA

Objectives: We recently identified a high affinity interaction between vacuolar H+-ATPase (V-ATPase) and microfilaments in osteoclasts and proposed that this binding is crucial for the transport of V-ATPase to ruffled membranes as osteoclasts activate. Phosphatidylinositol 3-kinase (PI3-kinase) has been shown by others to regulate formation of both ruffled membranes, which are rich in V-ATPase, and actin rings in osteoclasts. We therefore hypothesized that PI3-kinase might regulate binding of V-ATPase to microfilaments and sought to test this idea. Methods: Activated mouse osteoclasts on bone slices were treated for ten minutes with either wortmannin (100 nM) or LY294002 (50 µM) to inhibit PI3-kinase activity or, with vehicle as a control. The distributions of V-ATPase and F-actin were determined by fluorecence microscopy using the monoclonal antibody E11 to detect V-ATPase and phalloidin to stain F-actin. Binding between V-ATPase and F-actin was assayed in pelleting assays and in immunoprecipitation studies using E11 conjugated beads. Results: As expected, little co-localization between V-ATPase and F-actin was detected in vehicle-treated control osteoclasts. F-actin was in the actin rings and V-ATPase in the ruffled membranes. In contrast, ten-minute wortmannin treatment disrupted 89% of the actin rings compared with controls, and the actin ring microfilaments coalesced into patches focused at the site of the ruffled membranes, where the filaments co-localized with V-ATPase. Consistent with this result, the amount of V-ATPase recovered bound to F-actin shifted from 8.2% in vehicle-treated osteoclasts to 94.1% after 10-minute treatment with wortmannin. Osteoclasts recovered within 2H after wortmannin was washed out. As a control, treatment with jasplakinolide (100 nM), a membrane-permeable marine toxin which stabilizes actin filaments, disrupted actin rings but did not trigger an increase in V-ATPase bound to microfilaments. CONCLUSION: Our data support the hypothesis that PI3-kinase activity controls the binding interaction between V-ATPase and microfilaments in osteoclasts.


1729 (11932)

1a,25(OH)2D3 Regulates PKC via Activation of Phospholipase Cb and Gaq. S. GRUWELL*1, Z. SCHWARTZ2, V.L. SYLVIA1, D.D. DEAN1, and B.D. BOYAN1, 1 The University of Texas Health Science Center at San Antonio, USA, 2 Hebrew University Hadassah Faculty of Dental Medicine, Jerusalem, Israel

Objectives:  Changes in phospholipid metabolism are important in mediating the effects of 1a,25-(OH)2D3 (1,25) and 24R,25-(OH)2D3 (24,25).  Both regulate diacylglycerol, required for activation of protein kinase C (PKC).  1,25 stimulates PKC in chondrocytes from the upper hypertrophic zone (GC) of costochondral cartilage, and this is blocked by phospholipase C (PLC) inhibition.  24,25 stimulates PKC activity in resting zone (RC) cells, and this is blocked by phospholipase D (PLD) inhibition.  PLD activity and mRNA are greater in RC cells and are increased by 24,25, suggesting that PLC levels may be greater in GC cells and regulated by 1,25.  Methods:  To test this, we examined PLC specific activity in GC and RC chondrocytes in response to 1,25 (10-10-10-8 M) and 24,25 (10-9-10-7 M) over time.  Cultures were treated with the general G-protein inhibitor, GDPbS and the Gi protein inhibitor pertussis toxin.  Results:  1,25 dose-dependently increased PLC within 1 min, which was sustained for 90 min.  Neither 1b,25 nor 24,25 affected PLC.  GDPbS inhibited control and 1,25–stimulated PLC; pertussis toxin had no effect.  RC had comparable PLC activity to GC cells; 24,25 and 24S,25 had no effect.  Conclusions:  A PLCb family member mediates the effect of 1,25, since this family is regulated via Gaq, which is insensitive to pertussis toxin.  Responsiveness to 1,25 and 24,25 is receptor-mediated and not due to differences in basal PLC activity.  (NIH grant DE-05937, NIDCR Summer Fellowship, and CEBBI)


1730 (16340)

Differentiation of HME Chondrocytes in a Three-Dimensional Culture System. A.S. BENOIT*1, D. MONTUFAR-SOLIS1, J.T. HECHT2, and P.J. DUKE1, 1 The University of Texas Health Science Center at Houston - Dental Branch, USA, 2 University of Texas at Houston Health Science Center - Medical School, USA

Hereditary Multiple Exostoses (HME) is an autosomal dominant condition affecting endochondral bones, producing numerous juxtaepiphyseal osteochondromas (cartilage capped exostoses). Mutations in the EXT gene disrupt signaling events necessary for the proper orientation of cells in the growth plate. Conventional culture methods have not been successful in supporting differentiation of chondrocytes isolated from the cartilage cap of these exostoses. Preliminary studies using a rotating bioreactor (Synthecon, Inc.) indicated that HME chondrocytes could differentiate in this three-dimensional system. Objective: The objective of the current study was to assess cartilage differentiation and expression of the HME mutant phenotype (i.e. excessive actin fibers) in aggregates of HME chondrocytes grown in the bioreactor. Methods: Cells from the cartilage cap were grown as monolayers, trypsinzed to form a suspension and aggregated on a rotary shaker table for 48 hours. Aggregates were then placed in the bioreactor (50 ml capacity) and cultured for 3 weeks. Results: Many cells attached to the gas exchange membrane of the vessel, forming a large, thick layer. Unattached cells remained suspended as a spherical aggregate. Both spherical and flat aggregates were fixed and processed for light microscopy and immunostaining. Staining with Toluidine blue and with anti-type II collagen revealed much more differentiation, organization and metachromatic matrix production in the attached aggregate than in the floating one. Immunofluoresence staining for actin was also positive. Conclusions: This study shows that the bioreactor provides a useful system for the recreation of the phenotype of HME in vitro. Additionally, the growth of cells on the gas exchange membrane may allow us to address the HME chondrocyte’s loss of directionality which leads to formation of an exostosis.


1731 (21175)

Endochondral ossification of murine chondrocytes in a rotating bioreactor. N. HORN*, D. MONTUFAR-SOLIS, and P.J. DUKE, The University of Texas Health Science Center-Houston, Dental Branch, USA

Tissue engineering involves the use of in vitro culture systems to produce living tissues in quantities suitable for implantation into patients to repair defects. Although bone induction using demineralized bone or bone products goes through a cartilaginous phase before undergoing endochondral ossification, cartilage has rarely been used to replace bone, partly because chondrocytes have long been known to lose their phenotype when cultured in vitro. The rotating bioreactor (Synthecon, Inc.) has proved to be an excellent environment for chondrocyte culture in three dimensions, with retention of the chondrocyte phenotype. Objective: In this study, we evaluated the ability of the rotating bioreactor to support the growth and differentiation of murine chondrocytes. Methods: We cultured cells harvested from limb buds of E10.5 or E12 ICR mice in the bioreactor for three weeks. Results: Evaluation by light microscopy showed that the outer layer of the nodules has the histological appearance of a perichondrium. In the E10.5 cultures, the cells arranged themselves into what appear histomorphologically to be growth plates. These structures have areas with characteristics of reserve, proliferative and hypertrophic zones. Furthermore, Von Kossa staining showed areas of calcification. Hypertrophic cells secreted matrix containing collagen as confirmed with Goldner's trichrome stain. E12 embryo aggregates had regions that appeared to be vessels lined with endothelial cells. Further analysis of the sections is underway, including immunohistochemical staining for the products of endochondral ossification including collagen II, collagen X, osteopontin, and CD31 for vessel formation. Conclusions: The bioreactor is an excellent system for the culture of chondrocytes. Cells grown in this system show differentiation into four of the five zones found in endochondral ossification. Furthermore, chondrocytes grown in the bioreactor may provide clues to the means by which the growth plate is organized and how it grows longitudinally. (Supported in part by NIH/NIDCR Training Grant T35DE07252.)


1732 (12890)

Resorption of Bone in the Subosteoclastic Resorption Zone does not require Cathepsin B or L Activity. V. EVERTS*1, P. SAFTIG2, D. BROMME3, C. PETERS4, W. ROTH4, J. DEUSSING4, and W. BEERTSEN1, 1 ACTA, Amsterdam, Netherlands, 2 UNIVERSITY OF GOETTINGEN, Germany, 3 MOUNT SINAI HOSPITAL, NEW YORK, NY, USA, 4 UNIVERSITY FREIBURG, Germany

Cysteine proteinases (CPs), in particular cathepsin K, are essential for resorption of bone matrix by osteoclasts. Yet, bone-site specific differences appear to exist in the level of cathepsin K: high in long bone and low in calvaria (FASEB J, 13, 1219-30, 1999). This might suggest that also other CPs participate in resorption. Objective: To investigate the role of other CPs in bone resorption. This was analyzed: (1) in calvariae and long bones of mice with null-mutations for cathepsin K, B, L and K/L and (2) in bone explants cultured in the presence of selective CP inhibitors. Methods: Long bones and calvariae of cathepsin deficient mice were processed for microscopic examination. In addition bones from normal mice were cultured for 24 h in the absence or presence of a general CP-inhibitor (APC 2863; Axys Pharmaceut., CA), a selective inhibitor of cathepsin K (Z-GPL) and an inhibitor which blocks cathepsins B, L, and S but not cathepsin K (APC 3073; Axys Pharmaceut.). Results: Microscopic examination and morphometric analyses of long bones revealed in cathepsin K- and K/L-deficient mice large areas of non-digested demineralized bone matrix adjacent to osteoclasts. In calvarial explants such areas were much smaller. This effect was not seen in cathepsin B- or L-deficient mice. Analyses of inhibitor-cultured bones revealed that the general CP-inhibitor similarly blocked matrix digestion in both types of bone. The cathepsin K inhibitor strongly affected resorption in long bones but not in calvariae. Inhibition of the cathepsins B, L, and S had no effect. Conclusions: The data suggest that (1) cathepsin K is essential for digestion of long bones but less important for resorption of calvarial bone, and (2) other CPs, but not cathepsins B, L or S, participate in osteoclastic bone digestion.


1733 (11821)

Poisson’s Ratio Measurements of the Porcine Temporomandibular Joint Disc. M.W. BEATTY*1, K. EVANS2, A. HOYT3, A. JACOBSEN4, B. SIMETICH1, J.C. NICKEL1, and L.R. IWASAKI1, 1 University of Nebraska Medical Center College of Dentistry, Lincoln, USA, 2 University of Nebraska-Lincoln, USA, 3 University of Nebraska Medical Center College of Medicine, Omaha, USA, 4 University of Washington, Seattle, USA

Poisson’s ratio values derived for cartilage may not apply to the TMJ disc, which exhibits a directional collagen network and is orthotropic in tension.  Objectives: To measure Poisson’s ratio values in 3 dimensions and compare measurements at different extensions.  Methods: Porcine TMJ discs were sectioned into dumbbells with the tensile axis oriented in either the anteroposterior (AP) or mediolateral (ML) directions. Upper and lower marks were placed on the gauge length with India ink to measure strain occurring // and _|_ to the tensile axis.  Marks were placed on either width (AP, ML) or thickness (superior-inferior, SI) surfaces, in order to view strain occurring in one of two planes. Dumbbells were elongated at 1 N/s for ML, 5 N/s for AP, in order to generate linear elastic responses.  Mark separation was recorded with a digital video camera and stress-strain (SS) curves recorded.  The linear region was divided into three sections, and video frames for each section were used to measure distances between marks with Scion Image (Frederick, MD).  Four Poisson’s ratio values were calculated (n=5): AP/ML, SI/ML, ML/AP, SI/AP.  For each trial, a mean value was calculated for each section of the SS curve and a “pooled” mean calculated for three sections combined.  Best and worst measurement groups were identified based on their deviation from the pooled mean.  Results: Mean + s.e.m. for best group were AP/ML=1.2+0.19, SI/ML=1.1+0.15, ML/AP=2.3+0.38 and SI/AP=1.1+0.46, which differed from the worst group (p<0.05).  Conclusions: The best values were obtained by measuring extension over a long region of linear elasticity.  AP/ML values were larger than expected, possibly because AP fibers were shortened during sectioning of ML dumbbells, resulting in excessive transverse strain.


1734 (11961)

TMJ Disc Stresses During Stress-Field Translation. J.C. NICKEL*, L.E. ROTHE, L.R. IWASAKI, and M.W. BEATTY, UNMC College of Dentistry, Lincoln, NE, USA

It has been hypothesized that fatigue failure of the TMJ disc may be due to asymmetric distribution of compressive and shear stresses during movement of stress-fields. Objective: To test if asymmetric stress distribution occurs. Method: 10 porcine TMJ discs were used in a laboratory apparatus to measure the pressure distribution beneath the disc during movement of an acrylic indenter over the condylar surface of the disc. Each disc was statically loaded with 11 N for 60 s, after which the loaded indenter was translated mediolaterally over the condylar surface at 104 ± 16 mm/s. Stress distribution under each disc was measured using a linear array of nine transducers which had 3 mm between pressure sensitive areas and an accuracy of ± 6% full scale. All experiments were performed twice, with 2 h intervening between experiments to allow for disc rehydration. Pressure data under the leading and following edges of the stress-fields were plotted, and shear stresses and normalized pressure gradients were calculated. Results: Peak compressive stresses in excess of 80 Pa were recorded. The first pass of the indenter over the disc caused leading edge compressive stress gradients to be nearly twice that of the following gradients (p<0.001). After the third pass of the indenter there were no significant differences in gradients (p > 0.05). For all cycles, average shear stresses were 2.2 times greater for the lateral half compared to the medial half of the disc (range: 0.6 - 6.3, p < .01). Conclusion: Asymmetry in pressure distribution and shear stresses occurred during movement of a stress-field, and may explain why the lateral half of the disc is more prone to failure. L.E.R. was supported by a UNMC College of Dentistry Student Research Scholarship.


1735 (16617)

Dynamic Micromechanical Characterization of Maturing Rabbit Mandibular Fibrocartilage by Atomic Force Microscopy. K. HU*, P. RADHAKRISHNAN, R.V. PATEL, K. ROJAHN, and J.J. MAO, University of Illinois at Chicago, USA

The dynamic material properties of maturing rabbit mandibular fibrocartilage have rarely been investigated. Objective: Here we studied the dynamic micromechanical properties of the articular fibrocartilage of the mandibular condyle in maturing rabbits with atomic force microscopy (AFM). Methods: The articular surface of each of 18 condylar fibrocartilage samples, harvested from 9, eight-week-old, New Zealand White rabbits, was divided into the anteromedial, anterolateral, posteromedial and posterolateral regions, each of approximately 3 mm3 volume containing articular fibrocartilage and subchondral bone. After mounting the bony surface of the sample to the AFM, the cartilaginous surface was subjected to dynamic nanoindentation to obtain both topography and force spectroscopy in AFM's contact mode with oxide-sharpened Si3N4 tips. Results: Young's moduli differed significantly among the four regions in a descending range of 2.34 (±0.26) to 0.95 (±0.06) MPa: highest for the anteromedial region and lowest for the posterolateral region (p < 0.01). A third-order polynomial equation, Y=-354.98X3 + 480.95X2 - 201.69X + 27.84, provided the best fit for the distribution of Young's moduli of the four regions. The Poisson's ratios had the same trend of distribution as Young's moduli: highest for the anteromedial region (0.46±0.05) and lowest for the posterolateral region (0.31±0.05) (p < 0.01). The anterior regions showed more robust surface topography than the posterior regions. Conclusions: The articular fibrocartilage of the mandibular condyle in maturing rabbits is anisotropic with overall dynamic material properties that are capable of withstanding mechanical loads. Differential distribution of surface micromechanical properties likely results from regional variation of functional loads, leading to a new hypothesis that regional variation in micromechanical properties is general for other maturing fibrocartilaginous tissues such as the intervertebral disk. Supported by Whitaker Biomedical Engineering Research Grant and NIH grants DE13088 and DE13964.


1736 (10471)

Cartilage matrix gene expression in rabbit TMJ bilaminar zone. Z. GU1, J. FENG1, T. SHIBATA*2, Z. ZHANG3, and J. HU1, 1 Zhejiang University, Hangzhou, Zhejiang Province, China, 2 Yamagata University, Japan, 3 Piking University, Beijing, China

Objectives: In order to study the pathological changes and cartilage matrix gene expression in rabbit TMJ bilaminar zone (BZ) following disc displacement. Methods: Forty adult Japanese white rabbits were studied. The right joints of 28 among the 40 rabbits were subjected to surgical operation of disc displacement. Four rabbits in the surgical group were killed in 4 days, 1, 2, 4, 6, 8 and 12 weeks respectively after operation. Their TMJs were studied by histochemistry and in situ hybridization. The aggrecan and type ¢ò collagen mRNA expression was researched in the BZ following disc displacement. Results: In the experimental animals, the collagen fibers in BZ became densely, especially near the posterior band of the disc. Chondrocytes were found not only in the discs, but also in the BZs. There were two types of chondrocytes in the BZs. One was located among the collagen fibers, other was close to the surface of BZs. Sometimes the cartilage formation were seen in BZ and disc. The type ¢ò collagen mRNA expression was detected first in BZ in four days post-operative animal, and the gene expression seemed to be stronger and stronger after then. The aggrecan expression decreased at first, then increased gradually in 4 weeks post-operation. Conclusions: Some cells in the BZs changed their gene expression and the BZs became a fibrocartilage after disc displacement. In the situation, the BZ may work as a disc .


1737 (6700)

Condylar movement analysis in normal subjects, using an amorphous sensor. H. IOI*1, A.L. COUNTS2, and R.S. NANDA2, 1 Kyushu University, Fukuoka, Japan, 2 University of Oklahoma, College of Dentistry, Oklahoma City, USA

The purpose of this study was to determine the range of condylar movements in normal subjects by the use of an amorphous sensor. The pair-matched sample consisted of 17 Caucasian males (aged 25.8 ± 2.5 years) and 17 Caucasian females (aged 25.5 ± 2.8 years) who had no subjective or objective symptoms related to temporomandibular joint sounds. Bilateral condylar and jaw movements were recorded. Correlation coefficients (r) were calculated between any two measurements of condylar movement parameters. The results showed that the typical condylar movement points plotted on the X-Y co-ordinates indicated a uniform or approximately straight line, that is X=Y. The mean ± standard deviation (SD) for the maximum velocity of condylar movement during the opening and closing phases was 32.6 ± 16.9 and 39.8 ± 21.5 mm/sec, respectively. The mean ± SD for the degree of jaw opening at the turning point of condylar movement was 36.9 ± 21.7%. Significant correlations existed between any two measurements of maximum velocity of condylar movement (r=0.36 to 0.80). Significant correlations existed between the left and right sides in the degree of jaw opening at the turning point of condylar movement (r=0.71). These results suggest that a range of normal values of condylar movements can be developed by utilizing the amorphous sensor.


1738 (9864)

The effect of occlusal contact area on soft food chewing ability. Y.-Y. SHIAU*, H.-J. CHEN, C.-M. WANG, and K.-L. LOU, Graduate Institute of Oral Biology, College of Medicine, National Taiwan University, Taipei, Taiwan

Based on our previous findings that the homogeneity of HA particles (Calcitite 40-60 mesh, Calcitek, Sulzer, CA) in the chewing gum bolus after chewing can represent the soft food chewing efficiency of a subject. Objectives: The purpose of this study was to apply the HA containing chewing gum for the evaluation of dental occlusion on the chewing gum chewing efficiency. Methods: Ten males and 10 females (ages: 18 to 25 years) who had complete dentition and normal TMJ and muscle function were observed. Their centric occlusal contact area was calculated by using Prescale pressure sensitive film (Fuji film, Japan) and an image analysis system. After 10, 20, 30 and 40 times of chewing, the gum bolus was spit and frozen, and then sectioned. The HA distribution (in %) in a section of 1.0 mm thickness was observed with digital X-ray images and related to the occlusal contact area. Results: It was found that the homogeneity increased from 20.9± 6.7% to 60.5± 11.0% and was linearly related to the chewing stroke numbers before 30 chewing strokes in both male and female groups (r=0.75 and 0.64, P<0.01). After 30 chewing strokes, it became a plateau. The homogeneity was not closely related to the occlusal contact area (r=0.13 and 0.22, P>0.05). Conclusions: Based on the limit of this study, it was concluded that for soft food chewing, dental occlusal contact area does not strongly influence the chewing efficiency. Perhaps the manipulation of the bolus by soft tissues such as tongue and cheek is more important. (NSC 90-2314-B002-341)


1739 (16546)

Occlusal alterations influence multiple ipsilateral condylar points' movements during laterotrusion. B.-Y. HUANG*, C.W.L. JOHNSON, C.J. DURRANT, and G.M. MURRAY, University of Sydney, Westmead,NSW, Australia

Dental restorations often change tooth shape; however, there is little information about their effect on temporomandibular joint function. Previous studies of the effect of an occlusal alteration (OA) on condylar movements used only one point to represent the condyle, a 3-D object. Objectives: This study investigated the effect of a reversible OA on the tracings of multiple condylar points during laterotrusion. Methods: From 3 healthy subjects, CT scans were used to determine 5 ipsilateral anatomical condylar points (accuracy: ~0.5 mm): most superior, most anterior, and most posterior points, and lateral and medial poles. Jaw movements were controlled by visual feedback and recorded, in 6 d-of-f, using JAWS3D. 10 trials of right jaw movement were repeated under 3 conditions: Control 1 (before OA), OA (on right side), and Control 2 (after OA removal). Each trial had 5 phases: intercuspal position (IP) (2.6 s), outgoing (1.9 mm/s), holding (2.6 s), return (1.9 mm/s), and IP (2.6 s). Results: In all 3 subjects, OA caused a significant (p<0.05) change in condylar tracings at 6th mm of mid-incisal point displacement (MIPD) from IP for outgoing and return phases. At 3rd mm of MIPD, OA significantly altered condylar tracings at outgoing (n=2) and return (n=1) phases. At outgoing phase (n=1), OA changed the direction of movement supero-inferiorly in all points except the medial pole. Conclusions: The results suggest that an OA changes ipsilateral condylar movement. Supported by Australian Prosthodontic Society, Inc. and Australian Dental Research Foundation, Inc. bhuang@mail.usyd.edu.au


1740 (20505)

Correlation of the coronal form of condyle and disc on MR imaging. M.Q. WANG*, T. SHIBATA, and Y. ZHANG, Stomatological College, Fourth MIlitary Medical University, Xi'an, China

TMJ condyle has a vast variety in form. How about disc? The present study was conducted to invest the relationship of the form of condyle and disc. Materials and Methods: Bilateral TMJ of 78 TMD patients were examined with MRI (TR 2000, TE 16, THK 3.0) and the coronal MR imagines were studied focused on coronal form of condyles and discs following double blinding principle. Results: 1. The condyle form could be divided into four types. Type A, the condyle showed as a shuttle, both of the lateral and medial poles projected significantly. Type B, irregular round, one or both of the poles disappeared and the lateral-medial dimension was short to be as the condyle height. Type C, the medi-form of Type A and Type B. Type D, the condyle run upward obliquely from lateral to medial, with medial pole seated upmost. The discs could be divided into four types too. Type I, a very thin line between the cartilage images of condyle and fossa. Type II, no disc image could be found. Type III, disc imagined thick totally or locally. Type IV, dollop form of disc at or below the lateral or medial pole of condyle. Type IV disk is a kind of disc that used to be diagnosed as disc side displacement. The forms of condyle and disc had a close relationship with each other (x2=48.84, p<0.01). Type A (shuttle) condyle was more frequently found with Type I (26/78) or Type III (36/78) disc while the irregular condyle (Type C) with more dollop disc Type IV (16/21). Conclusion: The disc form had a close relationship with that of condyle. It may have influence on TMJ diagnosis. Supported by Foundation for University Key Teacher by the Ministry of Education of China.


1741 (21800)

Prevalence of HPV in the oral cavity of HIV+ individuals. J.E. CAMERON, P. HICKMAN, A.M. GAFFGA, M.E. O'BRIEN, P.L. FIDEL JR., M.E. HAGENSEE, and J.E. LEIGH*, Louisiana State University Health Sciences Center, New Orleans, USA

Objective: Recent reports have indicated a change in the frequency of oral lesions in HIV+ individuals since the introduction of HAART therapy with a reported increase in oral condylomas. Human papillomavirus (HPV) is the etiological agent of condylomatous lesions. Our objective was to examine the prevalence and risk factors for detection of HPV DNA in the oral cavity of HIV+ individuals.

Methods: Unstimulated saliva was collected from 50 HIV- and 100 HIV + individuals. DNA was extracted from epithelial cells, HPV amplified by L1 consensus primers, and genotype determined by line blot hybridization. Demographic and clinical variables were extracted from the Adult Spectrum of Disease database, and Fisher’s exact test used to compare groups.

Results: HPV DNA was detected in 6.1% of HIV- and 36.4% of HIV+ individuals (p<0.001). The most frequently detected HPV types were HPV-16 and MM7, with 28% being untypable and may contain oral-specific HPVs. The HIV+ population was predominantly male (63%), African-American (AA, 63%), and older than 34 (66%). Oral HPV DNA detection was less often seen in HIV+ AAs, with trends for increased risk for males and those older than 34. Intravenous drug use was a predictor for HPV DNA detection in AAs whereas HAART and being male were predictors for HPV DNA detection in Caucasians. HPV DNA detection was not associated with lower CD4 counts, higher HIV viral load, or concurrent oropharyngeal candidiasis (OPC).

Conclusions: HIV+ individuals were more likely to have oral HPV detected. The majority of the HPV types were genital types. HPV DNA detection was not associated with markers of advanced immune/disease status (OPC, CD4 count, viral load). Indeed HAART was not protective and potentially a risk factor for oral HPV infection in Caucasians. Further longitudinal studies are needed to better define the role of HAART in the natural history of oral HPV infection.


1742 (12452)

The Effects of Illicit Drugs, Alcohol and Smoking on Salivary Gland Disease in HIV Positive Women. R. MULLIGAN*1, M. NAVAZESH1, M.E.A.F. ALVES2, D. GREENSPAN3, and J. PHELAN4, 1 University of Southern California School of Dentistry, Los Angeles, USA, 2 University of Illinois at Chicago, USA, 3 University of California at San Francisco, USA, 4 New York University, NY, USA

Objectives: This study examines the relationship of behaviors such as illicit drug use during at least two different examination intervals (marijuana, crack/cocaine/heroin, methadone not prescribed by a doctor or amphetamine), drinking alcohol in the past 6 months and current cigarette smoking on salivary gland disease (SGD) in women enrolled in the multi-center Women's Interagency HIV Study (WHIS). These relationships were evaluated overall, by HIV status and, among HIV+ women, by HAART (Highly Active Anti-Retroviral Therapy) and baseline CD4 levels.

Methods: At each six-month visit over 4 years, SGD was assessed for the indicators enlargement (ENL), tenderness (TEN), or absence of saliva upon palpation (ABS) as being non-existent, unilaterally, or bilaterally present. Women were questioned on their involvement in the specific behaviors of use of illicit drugs, alcohol or cigarette smoking. Relative risks (RR) and 95% confidence intervals (CI) of SGD incidence associated with these behaviors were estimated using Cox regression.

Results: 451 HIV+ and 137 HIV- women were followed for a median of 3 years. In HIV+ women, 43% were illicit drug users, 59% were smokers and 59% used alcohol. Compared to HIV- women, the HIV+ were less likely to be drug users (p=0.03) and smokers (p=0.03). In HIV+ women, relative risk (RR) of bilateral submandibular/sublingual (SUB) SGD associated with illicit drug use was 1.7 (C.I.=1.2, 2.4); HIV+ women with lower CD4 counts (< 360) had a higher RR compared to those with higher CD4 levels [2.1 (CI=1.3, 3.6) versus 1.4 (CI=0.8, 2.4)], regardless of HAART status. In HIV- women, RR of bilateral enlargement associated with alcohol use was 0.2 (CI=0.1, 0.9). Smoking was not associated with SGD in either HIV+ or HIV- women.

Conclusions: In HIV+ women SGD incidence was increased by illicit drug use, but not by alcohol use or cigarette smoking.

Supported by NIH cooperative agreement number HD32632 and NIDCR.


1743 (18397)

Oral health characteristics of gay/bisexual men who practice oral sex exclusively. C.H. SHIBOSKI*1, J. BALLS1, A. HERNANDEZ1, D. GREENSPAN1, D. OSMOND1, J. DILLEY2, and K. SHAFER1, 1 University of California San Francisco, USA, 2 AIDS Health Project, San Francisco, CA, USA

Objectives: Little is known about the risk of HIV transmission associated with receptive oral sex (ROS). Poor oral health may increase any risk of oral transmission, and as part of the ongoing HIV Oral Transmission study we examined oral health practices among men who reported practicing oral sex exclusively and were eligible for this study. Methods: We recruited participants among users of anonymous HIV counseling and testing services in San Francisco. To be eligible a person had to have practiced oral sex exclusively in the past 6 months (no anal/vaginal sex) and should not have used injection drugs. Prior to HIV testing eligible participants received a face-to-face interview which measured, among other things, past oral sex practices and relevant oral health history. Results: The 194 gay/bisexual men eligible for our study were predominantly White (80%), median age of 38 years, and reported a median of 3 ROS partners in the past 6 months. Twenty percent reported ROS with an HIV+ partner, 89% of those did not use a condom, and 40% swallowed ejaculate. No HIV infection was detected in this group. A majority reported visiting a dentist (75%) and having their teeth cleaned (88%) in the past 6 months. Only 23 (12%) had a mouth/throat infection within the past 6 months. There was no association between history of such infection and number of ROS partners or report of ejaculation in the oral cavity. Conclusion: The prevalence of use of dental care (preventative care in particular) was very high in this group of men who reported having practiced oral sex exclusively in the past 6 months but among whom no HIV infection was detected. Good oral health may be a protective factor against oral acquisition of HIV infection. We are currently collecting clinical oral health data in this group to further study this hypothesis.


1744 (17819)

Oral lesions in HIV+/AIDS patients under highly active antiretroviral therapy for long time. A. CEBALLOS*1, L. GAITÁN2, and L. CEBALLOS1, 1 University of Granada, Spain, 2 National University of Mexico, México, Mexico

Objective: The highly active antiretroviral therapy (HAART) has been associated to a decrease of opportunistic oral infection (OOI) associated to Human Immunodeficiency Virus (HIV) infection. It has not been established the influence of time under antiretroviral therapy on OOI in HIV+/AIDS patients, therefore the principal objective of this work is to determinate OOI prevalence in HIV+/AIDS patients under different times of HAART. Method: 412 HIV+/AIDS patients, (304 males, 108 women, age mean 36.2 year old, ± 7.5), coming from Hospital Regional Carlos Haya, Málaga, Spain, were studied. All of the patient were under triple antiretroviral therapy (two nucleoside analogue and one protease inhibitor). The patients were classified into: Short time HAART group (154 patients): 24-28 weeks under HAART; and long time HAART group (258 patients): 104 weeks under HAART. The patients of both groups were divided according their quantity of RNA-HIV-1 viral copies/ml (<50 copies; >50 - <10,000 copies; >10,000 copies), and CD4+ lymphocytes cells count (>500; >200 - <500; <200). All of the patients were orally examinated, and opportunistic oral lesions diagnosed. Chi square test was performed by statistically significance (95%). Results: Short time Group. OOI prevalence 53.2%; Oral Candidosis 34.4%, Hairy Leucoplakia 26.6%. Long Time HAART group. OOI prevalence 66.7%; Oral Candidosis 39.1 %; Hairy Leucoplakia 30.2%. Of the subjects with CD4+ lymphocytes cells counts < 200/ml, lower prevalence of OOI and OC (p<0.05) was observed in short time HAART group. It was observed a statistically significant (p<0.05) relation between highest prevalence of OOI, OC and HL, and patients with highest viral loads, independently of time under HAART. Conclusions: The time under HAART is not directly associated to decrease of opportunistic oral lesions; OC and HL maintain their prognostic utility, independently of time under HAART.


1745 (15748)

Dental caries in Mexican HIV+/AIDS children in relation to immune and virologic status. L. GAITÁN*1, V. CUAIRÁN2, E. LEYVA1, R. FRAGOSO2, J. MORALES2, and C. AVILA2, 1 National University of Mexico, México, Mexico, 2 Child's Hospital of Mexico Federico Gomez, México, Mexico

Objectives: Since human immunodeficiency virus (HIV) infection is characterized by continuous decrease of CD4 lymphocytes cells, conditioning the presence of oral opportunists infections, it is not known if dental caries, an infectious oral disease, is related to severe immunosupresion and/or highest viral load. Therefore the principal objective of this work was to determine DMF index of Mexican HIV+/AIDS children in relation to immunosupresion degree and quantity of RNA-HIV-1 copies/mL. Methods: 41 Mexican HIV+/AIDS children (26 girls, 15 boys), under 13 years old, coming from Immunodeficiency Clinic of Child’s Hospital of México, México city, were enrolled in the present study. The children were divided according to gender, age (0 – 3 years old, 4-6 years old, >6 years old), CD4+ lymphocytes cells counts/mL in relation to age (moderate immunodepresion, mild immunodepresion, severe immunodepresion); quantity of RNA-HIV-1 viral copies/mL (undetectable viral load, <100,000 viral copies; >100,000 viral copies). All of the children was orally and dental examinated and their DMF index score was determinate. It was performed “t” Test for statistically significance between demographics subgroups(p<0.05). Results: DMF index score obtained from Mexican HIV+/AIDS children was 9.14. The subpopulation groups with highest DMF index score were >6 years old group, moderate immunosupresion group, and <100,000 viral copies group, not statistically significance were observe in any group (p>0.05 in all cases). Conclusions: DMF index in Mexican HIV+/AIDS children is not related to immunosupresion degree or viral load or gender, however it is in relation to age.


1746 (21417)

Oral Candidiasis In Human Immunodeficiency Virus-Infected Patients. A. JARAMILLO*, Universidad del Valle, Cali, Colombia

This study was carried out in HIV-infected patients of the Instituto de Seguros Sociales in Cali, Colombia. Objectives: To determine the prevalence of the different types of oral clinical candidiasis, to find risk factors associated with oral candidiasis, and to identify fungi species associated to ethiology. Methods: 81 patients were clinically evaluated to identify and classify oral candidiasis. Cultures of salivary samples were growth and identified by the color of the colonies cultured in a chromogenic agar, CHROMagar Candida®, the use of germ tube test and API 20 C® biochemical commercial yeast identification system. Results: There were studied 71 men and 10 women, aged from 19 to 63 years old. The prevalence of oral candidiasis was 34.6% (28/81). Candida albicans was the most frequent yeast, isolated in 56.8% of patients (46/81), even in those without oral candidiasis. Less frequent isolated species were Candida glabrata, Candida tropicalis, Candida inconspicua, Candida parapsilosis, Candida lusitaniae, Candida guilliermondii, Candida lambica, Candida krusei, Saccharomyces cerevisiae, Cryptococcus laurentii and Rhodotorula rubra. Acute pseudomembranous candidiasis was the most frequent clinical presentation in 71.4% of patients (20/28), followed by acute and chronic atrophic, chronic hiperplasic and angular cheilitis. Risk factors associated with oral candidiasis were O'Leary plaque index > 20% DFMT index > 11, Russell's periodontal index > 6 and number of CD4+ cells < 200. Conclusions: This study determined a high prevalence of oral candidiasis (34.6%). There were found a variety of clinical presentations, being acute pseudomembranous the predominant form. A high proportion of oral carriers of yeasts were found, and the most frequent yeast was C. albicans.


1747 (21762)

Detection of Kaposi’s associated Herpesvirus in the oral cavity of Immunocompetent and Immunosuppressed Individuals. J. WEBSTER-CYRIAQUE*, and K. KENDRICK, University of North Carolina at Chapel Hill, USA

The human Herpesviruses are generally shed in the oral cavity and transmission occurs via salivary route. These agents are generally detected with high prevalence in the general population with elevated viral loads during immunosuppression and occasional development of virus associated oral disease. The high frequency of Kaposi’s Sarcoma (KS) in HIV infected homosexual men has lead to the thinking that Kaposi’s Sarcoma associated Herpesvirus (KSHV/ HHV8) is sexually transmitted. Current serological tests for KSHV do not demonstrate superior sensitivity and specificity for detection of viral antigens in the blood and have determined that the seroprevalence within the US general population is 1-2 percent. Objective: To determine whether KSHV replicates in tissues of the oropharynx of immunocompetent, HIV-negative, Kaposi’s Sarcoma-negative heterosexual individuals and may be transmitted via saliva. Methods: Throat washings, peripheral blood and buccal scrapings were obtained from 30 HIV-positive and HIV-negative patients. DNA was isolated and PCR performed with KSHV specific primers within 4 distinct regions of the KSHV genome: ORF 26, K1, K9 and K15. PCR products were transferred by Southern blot and hybridized with internal probes and were purified and sequenced bidirectionally. Phylogenetic analysis compared viral strain variation within this population to viral sequences from KS lesions. Immunofluoresence determined expression of KSHV specific protein in oral epithelia. Results: In 80% of healthy individuals KSHV specific DNA was consistently detected within throat washings. Cluster analysis determined that the viral strains harbored within the oral cavity were similar to those detected in KS lesions. LANA immunofluoresence, detected consistent nuclear expression of the latent KSHV protein in the majority of buccal epithelial cell specimens assayed. Conclusions: These data suggest that non-sexual transmission of KSHV is operating within the immunocompetent US population and that saliva is a potential source of KSHV spread in the general population.


1748 (7532)

Periodontitis and Pregnancy Loss. S. LIEFF*1, K. BOGGESS1, H. JARED1, P. MADIANOS1, R. MCKAIG1, A. MURTHA2, K. MOSS1, M. WORLEY1, F. SMITH1, J. BECK1, and S. OFFENBACHER1, 1 University of North Carolina, Chapel Hill, USA, 2 Duke University, Durham, NC, USA

Objectives: Oral Conditions and Pregnancy (OCAP) is a prospective study designed to evaluate the contribution of periodontal disease (PD) to pregnancy complications. The purpose of this investigation was to compare risk for PD among women with term and preterm live births and women with fetal loss. Methods: A nested case-control design of the OCAP cohort was used to examine the relationship between fetal loss and clinical PD. Cases were defined as women experiencing fetal loss (either spontaneous abortion < 20 weeks or intrauterine fetal demise at >20 weeks gestation). Two randomly selected control groups were used, one of women with term live births (>37 weeks), and a second of mothers of preterm live infants. Controls were frequency matched by maternal age and race at a ratio of 2:1. Measures of PD were taken at enrollment, with disease categorized as none, mild or moderate/severe. Results: 682 pregnancies have resulted in term births, 162 in preterm births and 88 in fetal loss. Clinical data were available for 36 women experiencing fetal loss. The prevalence of no and moderate/severe PD among women with fetal loss was 14% and 17% respectively, compared to 25% and 6%, for women with term births. Compared to mothers of term infants, the unadjusted OR for severe PD among women experiencing fetal loss was 5.0 (95%CI 1.1-22.0). The adjusted OR for risk of severe PD among women with fetal loss compared to women with term live births was 4.8 (1.1-21.7). Similar risk for severe PD was noted in women with fetal loss when compared to women with preterm live births. Conclusions: Women with fetal loss are more likely to have severe periodontal disease. These findings suggest the need for further research on periodontal disease and fetal loss. Supported by NIDCR DE-12453.


1749 (14258)

Periodontal Disease Status and Preterm Birth In High Risk Women. T.M. SUNDELL1, D. BEAZLEY1, M.R. PATTERS*1, T.L. CARR1, J.A. BLANKENSHIP1, and B.M. MERCER2, 1 University of Tennessee Health Science Center, Memphis, USA, 2 MetroHealth Medical Center, Cleveland, OH, USA

Objectives: To determine prospectively the relationship between periodontal disease status and preterm birth (PTB) in women at high risk.

Methods: High-risk women <32 weeks gestation, defined as having prior PTB, preterm labor or tocolysis in current pregnancy, twins or higher order gestation, preterm contractions, abnormal cervical exam, abnormal cervical sonogram, substance abuse, or cervical incompetence, underwent a baseline periodontal examination utilizing the subset of teeth described by Ramfjord (#3,9,12,19,25,28). Each tooth was evaluated for plaque accumulation (PI), gingival inflammation (GI), probing depth (PD), bleeding on probing (BP), and clinical probing attachment loss (CAL) in 4 (PI, GI) or 6 (PD, BP, CAL) sites per tooth. Women with subsequent PTB (<37 weeks) or spontaneous PTB (SPB) due to preterm labor or premature rupture of membranes were compared with those delivering at term for differences in the listed periodontal disease parameters (t-test or chi-squared as appropriate, p<0.05 considered significant).

Results: 144 examined women have subsequently delivered. The incidences of PTB and SPB were 43.8% and 32.7%, respectively. We found no association between PTB and any index for periodontal disease status including mean PI (1.27±0.05 vs 1.26±0.06), mean GI (1.24±0.04 vs 1.20±0.05), mean percentage of BP (42.5±2.5% vs 42.9±2.6%), mean PD (3.2±0.1 vs 3.2±0.1 mm) or mean CAL (0.9±0.1 vs 1.0±0.1), when term gestation were compared with PTBs. Additionally, similar analyses incorporating only those subjects with parameters > 50th, ³ 75th or ³ 90th percentile demonstrated no significant association between elevated periodontal measures and PTB.

Conclusions: In this prospective trial of women at very high risk for PTB, we failed to identify a correlation between periodontal disease and subsequent preterm birth. This finding is contrary to previous reports in lower risk populations. It is possible that periodontal inflammation and destruction are not useful markers for PTB when known additional clinical risk factors are present.


1750 (15595)

Periodontal disease and adverse pregnancy outcome. A prospective study. S. MOORE*, M. IDE, R.F. WILSON, M. RANDHAWA, P.Y. COWARD, E. BORKOWSKA, and R. BAYLIS, GKT Dental Institute, London, United Kingdom

Objectives: This prospective study aimed to investigate the association between maternal periodontal disease and preterm birth (PTB, less than 37 weeks gestation) and/or low birth weight birth (LBW, less than 2500 grams) in a population delivering primarily at Guy’s and St Thomas’ Hospital Trust, London. Methods: Pregnant women were recruited at 10 to 15 weeks of pregnancy on attending an ultrasound scan. Subjects completed a questionnaire and periodontal examination, including plaque and bleeding scores, pocket probing depth and loss of attachment. Pregnancy outcome data was collected for 3186 subjects. Results: Regression analysis indicated that, despite expected relationships between pregnancy outcome and established obstetric risk factors, there were no significant relationships between the severity of periodontal disease, PTB and LBW. However, associations were found between decreasing gestational age and increasing attachment loss (p=0.004), and between miscarriage and both poorer oral hygiene (p=0.045) and higher mean probing depths (p=0.020). Some associations also existed between preterm low birth weight birth and aspects of previous dental care. However, the regression coefficients in these regression analyses were relatively low suggesting limited ability of these regression models to explain variations in pregnancy outcome. Conclusions: There appeared to be inconsistent evidence of relationships between some, but not all, markers of periodontal disease and adverse pregnancy outcome in this population.


1751 (15704)

Periodontal disease and adverse pregnancy outcome. An intervention study. S. MOORE, M. IDE*, R.F. WILSON, M. RANDHAWA, P.Y. COWARD, E. BORKOWSKA, and R. BAYLIS, GKT Dental Institute, London, United Kingdom

Objectives: This study aimed to investigate if treatment of pregnant women with severe periodontal disease would influence their pregnancy outcome. Methods: 167 of 196 suitable subjects, with at least five sites with probing depths of 5 mm or greater and three sites with 3 mm or more loss of attachment, were recruited from a larger cohort study of 3186 subjects at 10 to 15 weeks of pregnancy. Of these, 85 were assigned to the hygienist treatment group and received oral hygiene instruction, subgingival instrumentation and chlorhexidine irrigation. The 82 control subjects were advised to visit their own dentist if they so wished. All subjects were booked a periodontal reassessment at week 30 of their pregnancy. Results: Only 55 (65%) of the hygienist treatment group attended for any periodontal treatment and 42 (49%) attended for reassessment. Analysis of hygienist treatment group that received some periodontal treatment revealed no differences in the rate of adverse pregnancy outcome compared to the cohort study population. However, hygienist treatment subjects that received no periodontal treatment had a higher rate of both preterm birth (less than 37 weeks gestation) (20% versus 7%, p=0.018) and very low birth weight birth (less than 2000 grams) (11% versus 2%, p=0.037). In addition, this group had a higher rate of miscarriage (17% versus 2%, p <0.001) than the cohort study group. Similarly, hygienist subjects that did not attend a reassessment visit had a higher rate of preterm birth (19% versus 5%, p=0.048) than subjects that attended reassessment. However, analysis by change in periodontal health at reassessment demonstrated no differences in pregnancy outcome. Conclusions: Receiving periodontal treatment during pregnancy may have a protective effect against adverse pregnancy outcome, however, the poor compliance and differences in observed obstetric risk factors may have confounding effects.


1752 (17391)

Periodontitis and Labor Outcome at Term. M.C. VALLEJO*1, P. FAMILI1, A.L. PHELPS2, J. SUZUKI1, and S. RAMANATHAN1, 1 University of Pittsburgh, PA, USA, 2 Duquesne University, USA

Objectives: To determine if periodontitis has an effect on labor duration, maternal and neonatal outcome in parturients who deliver at term (>37 wks gestation). Methods: After local IRB approval, 56 term parturients (> 37 weeks gestation) received a periodontal examination using the Periodontal Screening and Recording (PSR) system. PSR scores range from code 0-4. PSR code 0 (no evidence of gingivitis or periodontitis) was compared to code 3 and 4 (mild to severe periodontitis) to determine the effect on labor outcome. Results for parity and gravidy are expressed as median and analyzed using Mann-Whitney. All proportion data were analyzed using Fisher’s Exact test. P < 0.05 is considered significant. Results: Results are expressed in the table. The percentage of periodontitis was higher in the perio group (39.3% vs. 0%, p=0.000). No significant difference was noted in age, gestation, gravidy, parity, cesarean section rate, stage II labor duration, Apgar scores < 7 at 1 minute and < 9 at 5 minutes, and birth weight between groups. The periodontits group had a longer stage I labor duration compared to the non-gingivitis/perio group. Conclusion: Periodontitis in term parturients is associated with longer stage I labor duration. This may be due to the altered hormonal-cytokine imbalance as a result of periodontitis.

 

Perio group

Non-Gingivitis/Perio

P

Age (yrs)

29.3 ± 6.4

30.7 ± 5.8

0.460

Gestation (wks)

38.8 ± 1.8

38.9 ± 2.3

0.855

Gravidy (median)

2

2

0.865

Parity (median)

1

1

0.920

Cesarean (%)

9.1

11.1

1.000

Stage I (mins)

740.9 ± 154.6

560.5 ± 203.0

0.045

Stage II (mins)

49.3 ± 51.1

37.9 ± 33.0

0.460

Apgar < 71 (%)

9.1

11.1

1.000

Apgar < 95 (%)

0

5.6

0.450

Birth wt (gms)

3462.6 ± 556.5

3512.0 ± 683.5

0.802


1753 (15787)

Prevalence of Periodontal Disease in Term Parturients. J. SUZUKI*1, M. VALLEJO1, P. FAMILI1, S. RAMANATHAN1, and A.L. PHELPS2, 1 University of Pittsburgh, PA, USA, 2 Duquesne University, USA

Objectives: The prevalence of periodontal disease during pregnancy is not known. The purpose of this study is to determine the prevalence of periodontal disease in term parturients compared to non-pregnant women using the Periodontal Screening and Recording (PSR) system.

Methods:After local IRB approval, 54 non-pregnant women (controls) and 56 term parturients (>37 weeks gestation) admitted to the labor suite received a periodontal examination using PSR. PSR is a screening classification system endorsed by the ADA and the American Academy of Periodontology to screen for the presence of periodontitis. PSR scores range from code 0-4: (0 – healthy gingival tissues, 1– bleeding after probing, 2 – supra/sub/gingival calculus and/or defective margins, 3 – probe depth > 3.5mm indicating mild periodontitis, 4 – probe depth > 5.5 mm indicating moderate to severe periodontitis). Summary statistics for age and gestation are expressed as mean ± 1SD. Mean age between the two groups was analyzed using t-test. Chi-square was used to test for independence of PSR scores. P < 0.05 is considered significant.

Results: Parturient mean gestation was 39.0 ± 1.9 weeks gestation. No differences were noted in mean age (29.0 ± 5.9 years parturients vs. 31.0 ± 8.1 years control (p=0.148). PSR scores for the presence periodontitis are presented in the table below. The prevalence rate of periodontal disease (Codes 3 + 4) in parturients is 39.3% vs. 9.3% in the control group.

Conclusion: The prevalence of periodontal disease is significantly higher in term parturients compared to controls. This most likely is due to the hormonal changes associated with pregnancy.

Table PSR Codes Parturients (%) Controls (%) P
No Perio 0+1+2 60.7 90.7 0.000
Periodontitis 3+4 39.3 9.3 0.000


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Periodontal Disease and Preterm Birth: A Case Control Study. K. JARJOURA*, P. DEVINE, A. PEREZ-DELBOY, M. D'ALTON, and P.N. PAPAPANOU, Columbia University, New York, NY, USA

Objectives: The purpose of this case-control study was to examine the association between maternal periodontal infections and preterm birth (PTB). Methods: Women giving birth prematurely (gestational age <37 weeks, “cases”) are matched for age, race, socioeconomic status and parity with women who deliver at term (controls). Women with multiple gestation, uterine or fetal anomaly, presence of cervical cerclage, elective preterm delivery secondary to medical or fetal indications, and history of a preterm delivery in a prior pregnancy are excluded. Enrolled women receive a partial-mouth periodontal examination including assessments of plaque (PI), bleeding on probing (BoP), probing depth (PD) and attachment level (CAL) at 3 buccal sites per tooth in two randomly selected, diametrically opposed quadrants. Subgingival plaque samples are collected from a maximum of 8 sites/subject (the mesial surface of one molar, premolar, canine and incisor per quadrant) and analyzed by checkerboard hybridization for the presence of 12 periodontal species. Level of serum IgG antibodies against oral bacteria is determined by means of checkerboard immunoblotting. Results: With ongoing recruitment, data from 50 cases and 38 controls is available to date. No significant differences were observed between cases and controls in mean PI (0.36 vs 0.35); BoP (0.39 vs 0.43) and PD (2.64 vs 2.62 mm). However, more pronounced clinical attachment loss was found in cases (1.75 vs 1.50 mm, p=0.004). No significant differences in the levels of all bacteria tested could be detected between the groups. Serum IgG levels against important periodontal pathogens, such as Porphyromonas gingivalis, Bacteroides forsythus, Actinobacillus actinomycetemcomitans, and Treponema denticola were found to be lower in cases than controls, although the difference did not reach statistical significance. Conclusions: These early findings are consistent with the hypothesis that maternal periodontal infections are associated with PTB.


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The Relation between General Diseases and Periodontal Diseases in Hospitalised Subjects. P.-O. SODER*1, L. JIN2, B. SODER1, S. AIRILA-MANSSON1, and B. KLINGE1, 1 Karolinska Institutet, Huddinge, Sweden, 2 University of Hong Kong, China

Objectives: The aim was to study the relation between general diseases and periodontal diseases in subjects hospitalised for general diseases in a longitudinal study. Methods: The participants were 1664 individuals 822 males, 35.87 (+- 2.8SD) yr. and 842 females 35.7 (+-2.9) yr. Their hospital care was followed during 13 years. Periodontal examinations were carried out when the participants entered the study with determination of plaque (PLI), gingivitis (GI), number of teeth with pockets 5 mm and deeper and number of remaining teeth. After 13 years the participants were divided in two groups, subjects who had been treated at the hospital for general diseases (D-group) and healthy/not treated at hospital (H-group). The first diagnosed general disease has been used according to the International Classification of Diseases, 9th Revision (ICD-9). Analysis of Variance was the statistical method used. Results: The results showed that 270 males in the D-group had in mean 1.4 (+-0.24SE) number of teeth with pockets 5 mm and deeper and 562 males in the H-group had in mean 0.9 (+-0.11SE) number of teeth with pockets 5 mm and deeper. The difference was statistically significant (p<0.05). GI was in mean 1.5 (+-0.03SE) for males in D-group and for males in H-group 1.3 (+-0.02SE). The difference was statistically significant (p<0.01). Subjects with diseases of the skin and subcutaneous tissue (ICD 680-709), diseases of the genitournary system (ICD 580-629) and diseases of the circulatory system (ICD 390-459), had in mean 2.4(+-2.3SE), 1.7 (+-0.73SE) and 1.4 (+-0.09SE) number of teeth with pockets 5 mm and deeper respectively at the start of the study. Conclusion: Periodontal diseases might have influence on general diseases. The study was supported by the Karolinska Institutet


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Differential Effects of A. actinomycetemcomitans and P. gingivalis on Cytokine Production by Oral Epithelial Cells. T. KUBOTA*1, D.F. LAPPIN2, J. SANDROS3, P.N. MANDIANOS4, P.N. PAPAPANOU5, and D.F. KINANE2, 1 Niigata University, Japan, 2 University of Glasgow, United Kingdom, 3 Göteborg University, Sweden, 4 University of North Carolina, Chapel Hill, USA, 5 Columbia University, New York, NY, USA

Objectives: to compare the effects of periodontal pathogens on the cytokine response of oral epithelial cells.  Methods: cell cultures of pocket epithelial cells and the KB oral epithelial cell line were incubated with live, heat killed or formalin fixed bacteria. In situ hybridization and immunohistochemistry were used to measure  cytokine expression by epithelial cells. Results: Porphyromonas gingivalis and Actinobacillus actinomycetemcomitans induced a rapid increase in IL-1b, IL-6 TNF-a and IL-8 gene expression in oral epithelial and KB cells manifested by an increase in mRNA and the accumulation of intracellular protein; with the maximum response generally recorded between 4 & 24 hrs.  These organisms also induced IL-10 expression, which increased gradually and reached peak levels at 72 hrs post-stimulation.  P. gingivalis had greater effects on pro-inflammatory cytokine and IL-10 expression, whereas A. actinomycetemcomitans had a greater effect on IL-8 expression (peak level at 36 hrs post-stimulation).  P. gingivalis strains low in fimbrae were less effective at stimulating cytokine expression. P. gingivalis cell viability did not influence cytokine expression since heat-killed and formalin-fixed bacteria had the same effect as live bacteria.  In contrast, cytokine stimulation by A. actinomycetemcomitans was mediated by surface structures that tended to be both heat and formalin sensitive. Conclusions: A. actinomycetemcomitans and P. gingivalis utilize different strategies during the infection process. The pathogenicity of these organisms is likely to be linked to their ability to attach to and possibly invade host tissues and to their ability to stimulate the inflammatory response of host cells.


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Cytokine secretion by and differentiation of monocytes triggered by Actinobacillus actinomycetemcomitans leukotoxin. A. JOHANSSON*1, P. KELK1, L. HÄNSTRÖM1, G. BELIBASAKIS1, and S. KALFAS2, 1 Umeå University, Sweden, 2 Aristotle University of Thessaloniki, Greece

A. actinomycetemcomitans (Aa) produces a leukotoxin that selectively kills human leukocytes. Monocytes are the most sensitive target cells and can be lysed at very low leukotoxin concentrations. However, it is unknown whether sublytic concentrations have any effect on these cells. The objectives of this study were to examine the production of pro-inflammatory cytokines by human monocytes and the differentiation of these cells when challenged with sublytic leukotoxin concentrations. Mononuclear leukocytes were isolated from human peripheral blood. Purified leukotoxin was added to monocytes and their production and secretion of cytokines was determined during the initial 20h by ELISA assays and RT-PCR. Mixtures of monocytes and lymphocytes were incubated with leukotoxin for up to 14 days and the formation of osteoclast-like cells in the cultures was followed by the activity of tartrate-resistant acid phosphatase (TRAP). Leukotoxin induced a high production and secretion of IL-1b from monocytes. Compared with other inducers of pro-inflammatory response, such as a-hemolysin or lipopolysaccharide (LPS) from Escherichia coli, Aa leukotoxin was more potent in activating IL-1b secretion. On the other hand, a-hemolysin and LPS from E. coli were more potent inducers of IL-6 and TNF-a production than Aa leukotoxin. Sublytic concentrations of Aa leukotoxin also promoted formation of TRAP-positive multinuclear osteoclast-like cells in mixtures of monocytes and lymphocytes. We conclude that sublytic concentrations of Aa leukotoxin can trigger an intense production and secretion of IL-1b in human monocytes. Aa leukotoxin also promotes the differentiation of monocytes to osteoclast-like cells.


1758 (14679)

Differential Regulation of IL-8 mRNA in Gingival Epithelial Cells by F. nucleatum or P. gingivalis. G.T.-J. HUANG*, and S.K. HAAKE, UCLA, Los Angeles, CA, USA

Prior reports have shown that IL-8 mRNA is up-regulated in epithelial cells challenged with Fusobacterium nucleatum (Fn), whereas IL-8 mRNA is simultaneously up-and down-regulated by Porphyromonas gingivalis (Pg) (Darveau et al, 1998; Huang et al, 2001). Objectives: To investigated the underlying mechanisms of these regulations. Methods: Experimental approaches included bacterial stimulation of gingival epithelial cells by either a brief challenge (2 h) or a continuous co-culture throughout the incubation period (4 h). Based on our previous report, the brief challenge resulted in IL-8 mRNA up-regulation by Pg, and the continuous co-culture is required for IL-8 mRNA down-regulation by Pg. In both approaches, epithelial cells were harvested at 4 h for analysis. Viable or nonviable (heat- or formalin-treated) Fn 12230 and Pg ATCC 33277 were used for the studies. Results: We found that nonviable Fn (heat-treated) up-regulated IL-8 mRNA less than its viable counterpart, whereas the ability of nonviable Pg (heat- or formalin-treated) to down-regulate IL-8 mRNA was lost. However, the nonviable Pg remained capable of up-regulating IL-8 mRNA. Treatment of epithelial cells with protein synthesis inhibitor cycloheximide did not affect the viable Fn to up-regulate IL-8 mRNA while it disabled the viable Pg to down-regulate IL-8 mRNA. Conclusions: Our data indicate that IL-8 mRNA up-regulation by Fn relies largely on heat sensitive bacterial factor(s) and this up-regulation does not require de novo protein synthesis in gingival epithelial cells; whereas IL-8 mRNA up-regulation by Pg is heat resistant and IL-8 mRNA down-regulation by Pg relies on heat sensitive bacterial factor(s). Furthermore, this IL-8 mRNA down-regulation by Pg appears in large part dependent on de novo protein synthesis in gingival epithelial cells. (Supported in part by a UCLA Academic Senate Research Grant and a UCLA School of Dentistry Research Opportunity Grant)


1759 (16548)

IL-1b, TNF-a and IL-10 mRNA Expression in Advanced Chronic Periodontitis. L.J. JIN*, L.K. CHAN, W.K. LEUNG, and E.F. CORBET, The University of Hong Kong, Hong Kong, SAR, China

Cytokines play key roles in periodontal pathogenesis and altered cytokine profiles may exist in uncontrolled periodontitis lesions. Objectives: This study was to investigate the mRNA expression profiles of three selected pro- and anti-inflammatory cytokines in chronic periodontitis. Methods: The participants were 13 subjects with advanced chronic periodontitis, mean age of 51.8+3.6 years. They received intensive non-surgical periodontal treatment but showed unresolved periodontitis lesions. Biopsies were collected from the sites with remaining deep pockets and adjacent non-pocket sites in a same patient during periodontal surgery. The tissue samples were evaluated for IL-1b, TNF-a and IL-10 mRNA expressions by Quantikine® mRNA quantitation kits. ANOVA and Chi-square test were used for statistical analysis. Results: The detection frequency for the three-target cytokine mRNA expressions at pocket (probing depth 6-10mm) and non-pocket (probing depth 2-3mm) sites was as follows - pocket/non-pocket: 100%/100% for IL-1b, 84.6%/85.7% for TNF-a and 92.3%/100% for IL-10. TNF-a expression was higher at pocket sites (322.0+74.4 amol/mL) than at non-pocket sites (184.6+43.5 amol/mL)(p<0.05), while no significant difference was found in the expressions of IL-10 and IL-1b between pocket and no-pocket sites. In the total expression levels of the three-target cytokines, higher relative proportion of TNF-a expression was found at pocket sites (39.7+7.2%) than at non-pocket sites (26.8+8.9%). The relative ratio of TNF-a and IL-1b expressions was also higher in pocket sites (3.7+0.5) than in non-pocket sites (2.4+0.9). A positive correlation existed in IL-10 mRNA expression between the pocket and non-pocket sites (r=0.77, p<0.05). No significant correlation was found among the three-target cytokine expressions. Conclusions: This study showed that both pro- and anti-inflammatory cytokines were expressed in pocket and non-pocket sites in unresolved chronic periodontitis. However, TNF-a mRNA expressions appeared to be upregulated in pocket sites which might reflect host-mediated periodontal destruction. Supported by the Hong Kong Research Grant Council (RGC, HKU 7310/00M & 7287/97M). ljjin@hkusua.hku.hk


1760 (21714)

Interleukin-1 beta in gingival crevicular fluid during orthodontic tooth movement and its association with the interleukin-1 genotype. S. BOBETSIS, M.V. THOMAS*, J. EBERSOLE, M. STEFFEN, and C.S. BEEMAN, University of Kentucky College of Dentistry, Lexington, USA

Objectives: The purpose of this investigation was to evaluate the presence of interleukin-1 beta (IL-1b) in the gingival crevicular fluid (GCF) during initial orthodontic tooth movement and establish a potential correlation with the IL-1 genotype. Methods: Thirty adolescent patients 9 to 14 years of age participated in this pilot study. All study participants were of northern European descent, except for one African-American. At the initial visit each patient received a periodontal prophylaxis, thorough oral hygiene instructions, and instructions to use a chlorhexidine rinse twice daily for two weeks. Two weeks later separators were placed on the mesial and distal of the upper and lower first molars unilaterally, the contralateral side serving as a negative control. Patients were recalled 24 hours following separator placement. At each visit GCF samples were collected from all four first molars using periopaper strips and were analyzed for IL-1b by means of ELISA. Unstimulated whole saliva samples were obtained from all subjects and analyzed to determine the presence of the IL-1 genotype. The volume of GCF was determined by means of a Periotron. Results: IL-1b levels in the GCF decreased after periodontal prophylaxis and increased 24 hours after separator placement in when compared to the negative controls (p<0.01). The prevalence of the IL-1 genotype in the study sample was 30%. Conclusions: the IL-1 genotype is associated with increased phenotypic expression of IL-1b in the GCF in response to mechanically-induced inflammation.


1761 (20635)

Effect of Porphyromonas gingivalis on Expression of IL-8 and MCP-1 in Human Umbilical Vein Endothelial Cells. S. MAO*1, N. MAENO2, and H. ODA2, 1 China Medical University, Shengyang Liaoning, China, 2 Kagoshima University, Japan

Objectives: To investigate the effect of Porphyromonas gingivalis (P.gingivalis)on the protein secretion and gene expression of Interleukin-8 (IL-8) and Monocyte Chemotactic Protein-1 (MCP-1) in human umbilical vein endothelial cells (HUVECs). Methods: HUVECs were derived from human umbilical vein. ELISA kits were used to determine the amount of IL-8 and MCP-1.RT-PCR and quantikine mRNA colorimetric quantification kits were employed to measure the mRNA of IL-8 and MCP-1 in HUVECs following P. gingivalis stimulation. Results: HUVECs constructive express IL-8 and MCP-1 in protein and gene level. Viable or deactivated P. gingivalis does-dependently induced both of IL-8 and MCP-1 protein secretion in HUVECs. Up-regulation of IL-8 protein in HUVECs started at 4h after infection, reached maximal level at 12 h, and kept at this level at following 8 h of co-cultivation. Whereas increased MCP-1 was found at 4 h, peaked at 8 h, kept at maximal level at 12 h and 16 h, and then decreased at 20 h after exposures of P. gingivalis. Polymyxin B and treatment of boiling, , which inhibit the effect of LPS and TNF-a respectively, did not weak the increased effect of P. gingivalis. 108 cfu /ml of P. gingivalis more strongly induced IL-8 and MCP-1 mRNA expression than that at density of 107 cfu /ml after 4 h of infection. The mRNA of IL-8 in HUVECs enhanced at 1 h after interaction with P. gingivalis and kept increasing at 3 h and 5 h of stimulation. Whereas MCP-1 mRNA started at 1 h, peaked at 3 h, and decreased at 5 h after infection.

Conclusions: Endothelial cells enhanced IL-8 and MCP-1 expression at protein and gene levels in the early time of P.gingivalis infection. The effective factor, which is anti-heating, was not P.gingival LPS. The increased IL-8 and MCP-1 might be involved in accumulation and activation of neutrophils and monocytes at the early time in periodontal pathogenesis.


1762 (19212)

Evidence for IL-4 and IL-5 expression in PBMC of patients with aggressive periodontitis. B.W. SIGUSCH*1, W. PFISTER1, S. EICK1, G. KLINGER1, E. GLOCKMANN1, J. SCHUETZE1, and H.U. SIMON2, 1 University of Jena, JENA, Germany, 2 University of Bern, Switzerland

IL-4 and IL-5 appear to be important in the pathogenesis of allergy-related diseases. We have recently reported that patients with aggressive periodontitis are more involved in positive patch test reactions suggesting that deep periodontal pockets are possibly related to an allergic disposition. But, there is little information about the involved pathogenetic mechanisms. Objective: The aim of the present study was to investigate cytokine expression in 45 patients with aggressive periodontitis (age<35 years). As controls we included age and sex-matched subjects without any signs of periodontal diseases. Methods: The levels of IFN-g , IL-2, IL-4 and IL-5 were measured in culture supernatants from PHA-activated PBMC by ELISA and cytokine mRNA expression was determined using a RNA purification kit (Quiagen, Germany) and PCR. Results: We observed significantly increased IL-4 and IL-5 levels in supernatants from the patient group compared to the values from controls. Furthermore we obtained evidence for increased IL-4 and IL-5 mRNA expression levels in PBMC from aggressive periodontitis patients compared to healthy control individuals. Odds ratios were derived from a logistic regression model. The odds ratios (95 %CI) for association with aggressive periodontitis were 1.046 (1.002-1.092) for IL-4 and 1.201 (1.009-1.429) for IL-5.

Conclusion: This case control study demonstrate that the presence of IL-4 and IL-5 expression are associated with increased risk of aggressive periodontitis. The present study was supported by a Grant of BMBF, Germany, FKZ 11ZZ9602.


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CD14 and Toll-like Receptors Regulate Lipopolysaccharide Induction of KGF-1 Protein Expression. E.E. PUTNINS*, A.-R. SANAIE, J.D. FIRTH, and Q. WU, University of British Columbia (Dentistry), Vancouver, Canada

Abnormal epithelial cell proliferation is one aspect of periodontal disease progression. Regulation of this process is complex but may include lipopolysaccharide (LPS) from Gram-negative pathogens. Objectives: This study examined LPS-specific induction of Keratinocyte Growth Factor (KGF-1, FGF-7)-1 expression by human gingival fibroblasts (HGF). This growth factor is expressed by stromal cells and acts as a specific paracrine mediator of epithelial cells. Its expression is significantly upregulated in nonoral chronic inflammatory conditions but its expression during the onset of periodontal diseases is unclear. Previously, we showed LPS purified from P. gingivalis (ATCC 33211) and E. Coli (O55:B5) induced KGF-1 protein expression in HGF but the mechanism regulating this finding is not understood. Currently, it is believed that LPS binds to serum-associated lipopolysaccharide-binding protein (LBP) and this complex interacts with either serum-associated or membrane-associated CD14 and other membrane bound receptors such as Toll-like receptor 2 or 4 (TLR-2/TLR-4). Methods: Therefore, we first examined the LPS induction of KGF-1 expression in the presence and absence of serum and recombinant CD14 (rCD14) to determine if CD14 regulates the induction process. Second, CD14, TLR-2 and TLR-4 specific blocking antibodies were used to selectively inhibit these receptors. KGF-1 protein in conditioned media was assayed using sandwich ELISA. Results: Our results showed LPS induction of KGF-1 expression was not dependent on serum-associated CD14 protein nor was it affected by the addition of rCD14. However, membrane-associated CD14 was expressed on gingival fibroblasts and blocking its functional site with a specific antibody completely inhibited LPS induction of KGF-1 expression. The signaling pathway was also dependant on the presence of functional TLR-2 and TLR-4 receptors because specific blocking antibodies to either receptor also inhibited the LPS effect. Conclusions: Therefore membrane-associated CD14 and activation of both TLR-2 and TLR-4 receptors are required for LPS induction of KGF-1 expression in HGF. Supported by CIHR, Canada


1764 (17556)

The biocompatibility of glass ionomer cement to jaw bone. An experiment in the rat. J. LUNDELL*1, N. LIOUBAVINA2, and G. BRATTHALL1, 1 Centre for Oral Health Science, Malmö University, Sweden, 2 The Royal Dental Collage, Faculty of Health Science, Aarhus, Denmark

The aim of this investigation was to evaluate bone formation around glass ionomer cement (GIC) implants to consider the possibility of using GIC as a substitute to lost periodontal tissue in the furcation area. Objectives: The experiment was carried out in 10 male 6 month-old albino rats of the wistar strain. Methods: The mandibular ramus was exposed and a Teflon capsule was placed with its opening facing the periosteum. The implants were placed in the centre of the capsule with GIC- implants on one side (test) and titanium implants (Ti) on the other side (control). After healing periods of 4 and 6 months, groups of 5 animals were sacrificed each time and embedded with the capsule in the center in metylmetacrylat. Non-decalcified centre sections approximattly 15 micrometers were obtained by Exakt cutting and grinding system (Exakt Company, Hamburg, Germany) for histological analysis. Results: All test and control specimens demonstrated production of new bone after 4 months. After 6 months the bone was more matured. None of the samples showed any sign of inflammation. The GIC- implants showed a defined fibrotic tissue space encapsulating the implant. The Ti-implants showed more bone formation and a narrow interface between bone and the implant. Conclusion: The results indicated that it might be possible to use GIC as a bone substitute in furcation involved molars.


1765 (12620)

Immunohistochemical evaluation of some matrix molecules associated with wound healing following regenerative periodontal treatment. A. SCULEAN1, N. DÜNKER1, R. JUNKER1, P. WINDISCH2, N. DONOS3, and M. BRECX*1, 1 University of Saarland, Homburg, Germany, 2 Semmelweis University, Budapest, Hungary, 3 Eastman Dental Institute, London, United Kingdom

Treatment of intrabony defects with guided tissue regeneration (GTR) or an enamel matrix protein derivative (EMD) has been shown to promote periodontal regeneration. However, up to now there are only very limited informations describing the expression of different matrix molecules in the regenerated periodontal tissues. Aim: i) to investigate immunohistochemically in monkeys and humans the expression of some matrix molecules expressed in the periodontal tissues reformed after treatment of intrabony defects with GTR or EMD. Methods: Intrabony defects were treated with GTR or EMD. At 5 and 6 months respectively, the healed periodontal tissues were evaluated immunohistochemically by means of monoclonal antibodies against osteopontin, collagen I and collagen III. The original (non-treated) parts of the periodontium served as controls. Results: The results revealed that in all investigated specimens where the healing resulted in formation of cementum, periodontal ligament and alveolar bone a strong expression of investigated matrix molecules was present. In all specimens the expression of investigated matrix molecules was stronger at the reformed than at the original sites. No differences in the expression pattern of any of the investigated matrix molecules were found between the treatments. Conclusion:The present results suggest that: i) both treatments may create an environment favorable for periodontal regeneration, and ii) the expression pattern of osteopontin, collgen I and collagen III seem to be comparable in monkeys and humans.


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BMP Gene Delivery for Alveolar Bone Repair. W.V. GIANNOBILE, Q. JIN, S.A. WEBB*, and R.B. RUTHERFORD, University of Michigan, Ann Arbor, USA

Bone morphogenetic proteins (BMPs) are potent stimulators of cementogenesis and osteogenesis. We and others have previously shown that administration of BMPs promotes periodontal tissue regeneration in vivo. Limitations of protein delivery to periodontal defects include transient biological activity of BMPs and bioavailability of factors at the wound site. Objective: The objective of this investigation was to determine the ability of BMP-7/OP-1 to stimulate periodontal bone regeneration by ex vivo gene transfer in surgically-created, periodontal alveolar bone wounds. Methods: Syngeneic dermal fibroblasts were transduced with 200 MOI of virus (adenovirus encoding a reporter (green fluorescent protein; Ad-GFP), a negative regulator of BMP bioactivity (Ad-noggin) or BMP-7/OP-1 (Ad-BMP7)). The cells (1 x 106 per site) were then transplanted to large fenestration defects using a gelatin (Gelfoam ®) carrier at the buccal aspect of the mandibular first and second molars (defect size: ~5 x 5 x 2 mm) in Lewis rats (n=4/group). Block biopsies were harvested at 10, 21 and 35 days post-gene delivery and descriptive histology and histomorphometric analyses were performed. Results: Results generated from these studies reveal high level protein expression of noggin and BMP-7 following gene transfer as determined by western blot analysis. Furthermore, defects treated with cells transduced by Ad-BMP-7 demonstrated strong evidence for bone regeneration in the defect area and a zone surrounding the gelatin carrier. Histomorphometry findings showed a greater than 3 fold increase in new bone area in BMP-7 treated sites, while lesions treated with Ad-GFP showed bone formation limited mainly to the wound margins. Ad-noggin treatment appeared to have an inhibitory effect on osteogenesis as compared to the Ad-GFP-treated specimens. Conclusion: We conclude that ex vivo gene transfer of BMP-7/OP-1 stimulates alveolar bone regeneration. Gene therapy utilizing BMPs may offer potential for periodontal tissue engineering. (Funded by NIH/NIDCR DE 11960, DE 13397, and DE 12466) e-mail: wgiannob@umich.edu.


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Effect of Enamel Matrix Proteins on Gingival Wound Healing in Rat. J. ANANTHASANE*, J.L. BORKE, D.H. PASHLEY, J. MAILHOT, M. BILLMAN, A. SMITH, and K. AGEE, Medical College of Georgia, Augusta, USA

Enamel matrix proteins (EMP) are responsible for the initiation of amelogenesis and cementogenesis during embryonic odontogenesis.  The biological characteristics of EMP are coincident with periodontal regeneration.  EmdogainÒ (EMP in propylene glycol or emd) is a product primarily marketed for use in intrabony periodontal regeneration, and promising clinical results have been achieved.  Many clinicians have also reported increases in gingival healing with emd treatment.  To date, little evidence supports this observation.  Objectives:  The purpose of this study is to determine the effects of emd on gingival wound healing indirectly by measuring ultimate tensile strength(UTS) and hydroxyproline(HP) concentration.  Methods: Fifty Sprague-Dawley rats were separated into groups as follows:1) five unwounded control(uc), 2) 15wounded control(wc), 3) 15propylene glycol treated(pg), and 15emd in propylene glyco(emd) treated.  Linear incisions were made across the hard palate of all rats except the unwounded control. All wounds were injected with emd, propylene glycol, or nothing.  Wounds were harvested and tested for UTS, and HP concentration at 3, 7, and 14 days.  Results:  There was a significant difference in UTS between the days of wounding (p<0.05 among all groups),  but no differences were found  among the groups (p>0.05).  UTS (Mean in MPa+SE) for each group was as follows: 5.49+1.11 (uc), 4.05+.058 (wc14days), 5.04+.98 (emd14days), 4.29+.52 (pg14days), 2.37+.57 (wc7days), 2.26+.5 (emd7days), 2.11+.52 (pg7days), 0.56+0.15 (wc3days), 0.19+0.057 (emd3days), and 0.58+.35 (pg3days).  There was a significant difference (p<0.05 among all groups) in HP concentration between the days, but no difference(p>0.05) was found among groups.  Hydroxyproline concentration means (ugHP/sample+SE) were 4.833+1.778(uc), 3.987+1.083 (wc14days), 3.849+1.009 (emd14days), 3.339+1.058 (pg14days), 5.249+.286 (wc7days), 6.019+.581 (emd7days), 5.081+.326 (pg7days), 5.337+.261(uc3days), 6.327+.520 (emd3days), and 5.881+.593 (pg3ddays).  Conclusion:  Our data suggests that enamel matrix proteins do not enhance nor adversely effect gingival wound healing. Supported by NIH/NIDCR DE12812 (JLB), MCG Dental Foundation, and the Wilmer B. Eames Study Club.


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Effectiveness of Coronally Advanced Flaps With or Without the Addition of Enamel Matrix Derivative in the Treatment of Marginal Tissue Recession. M.A. CUEVA*1, W.W. HALLMON1, M.E. NUNN2, E.P. ALLEN1, F. RIVERA-HIDALGO1, and F. ESLAMBOLTCHI1, 1 Baylor College of Dentistry, Dallas, TX, USA, 2 Boston University, MA, USA

Objectives: To evaluate the effectiveness of enamel matrix derivative (Emdogain® - Biora,Inc. Chicago,IL) in the treatment of marginal tissue recession.

Methods: In order to evaluate the effectiveness of enamel matrix derivative in the treatment of marginal tissue recession, 15 eligible subjects with at least two contralateral sites with ³2 mm buccal recession were enrolled in this study. A split-mouth design was utilized with contralateral sites within each subject randomized to receive coronally-positioned flaps with or without the application of enamel matrix derivative so that each subject served as his own control. Fifty sites were included in the study, 25 test sites and 25 control sites, with subjects followed for 3 months after surgery. Percent root coverage, sensitivity, and tissue keratinization of test sites after 3 months were compared to control sites utilizing the method of generalized estimating equations (GEE) to accommodate multiple contralateral pairs within some subjects. Initial clinical parameters were considered for inclusion in GEE regression models to adjust for potential baseline differences.

Results: Based on GEE regression, test sites had significantly greater root coverage after 3 months compared to control sites (p<0.001) with 88.4% root coverage for test sites compared to only 49.2% root coverage for control sites. Based on a GEE logistic regression model, control sites were significantly more likely to exhibit sensitivity after three months compared to test sites (OR=5.8, p<0.001). In addition, test sites had a somewhat greater increase in keratinized tissue after 3 months compared to control sites, although the increase was not statistically significant (p=0.078).

Conclusions: The application of enamel matrix derivative to denuded root surfaces receiving coronally-positioned flaps significantly increases root coverage and significantly reduces post-operative sensitivity. In addition, preliminary results indicate that enamel matrix derivative may lead to a greater increase in keratinized tissue at treated recession sites.


1769 (18180)

Treatment of intrabony defects with Emdogain® and two different bone substitutes. F. DÖRI*1, A. SCULEAN2, N.B. ARWEILER3, and I. GERA1, 1 Semmelweis University, Budapest, Hungary, 2 University of Saarland, Homburg, Germany, 3 Albert-Ludwigs-University Freiburg, Germany

Objective: To compare the treatment of deep intrabony defects with a combination of an enamel matrix protein derivative (EMD) and two different types of bone substitutes. Methods: Twenty two healthy patients, each of whom displayed one intrabony defect were randomly treated with a combination of EMD (Emdogain®, BIORA AB, Malmö, Sweden) and either a natural bone mineral (NBM) (Bio-Oss®, Geistlich, Wolhusen, Switzerland) or tricalcium phosphate (TCP) (Cerasorb®, Curasan, Germany). Soft tissue measurements were made at baseline and at one year following therapy. Results: No differences in any of the investigated parameters were observed at baseline between the two groups. No adverse healing response was observed in any of the patients. At 1 year after therapy the sites treated with EMD + NBM revealed a change in clinical attachment level (CAL) from 9.0 ± 1.5 mm to 5.0 ± 1.2 mm (p < 0.0001). In the group treated with EMD + TCP the CAL changed from 7.9 ± 1.6 mm to 4.9 ± 2.7 mm (p < 0.0001). Hard tissue fill was observed radiographically in all defects. Although, both treatments resulted in significant CAL gains no statistically significant differences were observed between the two groups (p>0.05). Conclusion: Within the limits of the present study it can be concluded that both therapies may lead to significant improvements of the investigated clinical parameters.


1770 (15877)

Sustained Release of Stains to Increase Cranial Bone Thickness. M.R. THYLIN*, J. MCCONNELL, M. SCHMID, and R.A. REINHARDT, University of Nebraska, Lincoln, USA

Recent reports have shown that multiple injections of the cholesterol-lowering drug simvastatin are capable of increasing short-term bone thickness in mice. The purpose of this study was to design a sustained-release system (potentially useful in periodontal bone augmentation) used to test the hypothesis that placing a single dose of simvastatin in a methylcellulose gel contained within a polylactic acid (PLA) membrane would increase long-term calvarial bone thickness. Pure simvastatin (2.2 mg, optimal dose from pilot study; Merck & Co., Inc., Rahway, NJ) was incorporated into 4% methylcellulose gel, and then 50 ml placed into domed membranes made of PLA. Membranes containing gel only (n=7) or simvastatin (n=9) were implanted subcutaneously on the calvaria of 6-week old female ICR Swiss mice, and the mice were sacrificed after 22 or 43 days. The calvaria were removed, decalcified and processed for histomorphometric evaluation with hematoxylin and eosin. Slides were digitized and measured for bone thickness and area using Sigma Pro Scan (SPSS Science, Chicago, IL), followed by analysis of variance (ANOVA). Inflammation of overlying skin occurred in the simvastatin group, but the mice continued to be active, eat and gain weight. ANOVA showed statistically significant (p < 0.05) increases in bone area (31%) and thickness (32%) when the simvastatin-treated animals were compared to gel controls. The sagittal suture area showed the greatest bone response. The increased bone noted at 22 days post-dose was not statistically different at the 43-day period. These results indicate that a single dose of simvastatin in methylcellulose gel/PLA membrane can increase long-term calvarial bone thickness in mice. Supported by Nebraska Society of Periodontology.


1771 (20472)

Effects of titanium surfaces on osteoblast gene expression profiles. P.M. BRETT*, V. SALIH, I. OLSEN, and M. TONETTI, University College London, United Kingdom

Objectives: Titanium (Ti) and Ti alloys have been widely used as dental implants because of their mechanical strength, durability and excellent biocompatibility. Specific phenotypic and functional changes have been observed in in vitro experiments using osteoblasts exposed to various Ti surfaces, however, the molecular events underlying the changes seen is as yet unknown. The aim of this study was to examine mRNA expression profiles of osteoblasts in response to conventional polished Ti and a modified Ti surface (SLA) using DNA gene arrays to determine these molecular events. Methods: Human alveolar bone cells were obtained from molar extractions and their phenotype confirmed by von Kossa staining of mineralised nodules. The osteoblasts were grown on the two different Ti surfaces for 3 h and 24 h. Morphological examination by SEM showed that there were notable differences in the effects of these surfaces on the attachment and spreading of the cells. RNA extracted from the cells was used to produce cDNA probes for hybridisation to ATLAS™ gene array filters. Results: Comparison of the hybridisation patterns obtained, using AtlasImage™ 2.0 software, showed that 29 genes were differentially expressed after 3 h and 102 genes after 24 h of culture. Conclusions: These experiments show that Ti surfaces can influence the morphological features and gene responses of osteoblast cells in vitro, and suggest the possibility that these surfaces could be modified in order to elicit enhanced biological activity and clinical efficacy. Supported by a grant from the ITI Foundation, Switzerland.


1772 (13020)

A comparison of the inhibiting potential against oral malodor of zinc ions and two antibacterial agents. A.R. YOUNG*, G. JONSKI, and G. RÖLLA, University of Oslo, Norway

Zinc ions in aqueous solution inhibit oral malodor by interaction with precursors of the volatile sulfur compounds (VSC), which are amongst known causes of oral malodor. This is furthermore the case with cetylpyridinium (CP) and chlorhexidine (CHX), both presumably operating through an unspecific antibacterial effect. Objective: To compare the anti-oral malodor effect of these agents in terms of duration, and dose/effect relationships. Method: In a clinical study oral malodor was induced in test subjects by mouth rinses with cysteine solutions. The oral VSC response to cysteine rinses, with and without pre-rinses with differing inhibiting agents, was examined. Tested agents were: Zinc acetate (ZnAc)(0.1, 0.3 and 1.0%), CHX-diacetate and CP-chloride (0.025 and 0.2%). Mouth air was analyzed by gas chromatography according to current methodology, and the 1, 2 and 3h values subsequent to a single rinse with each of the different inhibitors were recorded. Results: ZnAc reduced VSC 97-90% after 1h, and 91-37% after 3h dependent upon concentration. 0.2% CP reduced VSC 45% after 1h, and 30% after 3h. 0.025% CP reduced VSC 47% after 1h and only 15% after 3h. 0.2% CHX reduced VSC 77% after 1h, 95% after 2h and 96% after 3h. 0.025% CHX reduced VSC 46% after 1h, 40% after 2h and 40% after 3h. Conclusions: Zinc ions had a marked short-term effect that deteriorated rapidly with the lower concentrations. The high concentration had an unpleasant, metallic taste, whereas the lower concentrations were found acceptable. CP showed little enhancement of anti-VSC effect with increasing concentration, and the effect deteriorated rapidly regardless of concentration. The high concentration of CHX showed increasing effect with time whereas the low concentration maintained its effect with time. The low concentration of CHX exhibited an acceptable taste and does not appear to cause dental stain.


1773 (13007)

Anti-volatile sulfur compounds (VSC) effect of zinc-chelates with high stability constants. G. RÖLLA*, G. JONSKI, and A.R. YOUNG, University of Oslo, Norway

Lozenges containing an amino acid-chelated Zn with a high stability constant (log K1=8) have been shown to inhibit the formation of oral volatile sulfur compounds (VSC). Objectives: To examine the anti-VSC effects of other Zn-chelates. Of four Zn-chelates received as gifts (Albion Laboratory, Utah, USA), two were amino acid-chelates containing 10 and 20% Zn respectively, the third and fourth were arginine- and histidine-chelated, both with 10% Zn. The chelate containing 20% Zn was water soluble, whereas the others had low water solubility. Methods: Addition of small amounts of Zn ions to human saliva incubated overnight at 37 degress C in closed tubes inhibits the copious production of VSC in the headspace. Part A: Zn acetate (ZnAc) and different Zn chelates in dry state (=1mg Zn) were added to test tubes containing one ml of human mixed saliva. After 24 h incubation the amount of headspace VSC was measured in a GC. Part B: 1mg samples of ZnAc or Zn-chelates were added to test tubes containing one ml distilled water saturated with H2S. After 5 min incubation the amount of VSC was measured in the GC. Part C: The clinical anti-VSC effect of a solution containing the soluble Zn-chelate was examined in volunteers and compared with a solution of ZnAc containing the same amount of Zn. Oral VSC formation was enhanced with cysteine as described in previous studies. Results: A) the Zn-chelates inhibited VSC in saliva samples, B) the Zn-chelates inhibited release of Zn from water saturated with H2S, C) the soluble Zn-chelate inhibited oral H2S formation in vivo. All effects were similar to that of ZnAc, which has a very low stability constant. Conclusion: It is suggested that the Zn chelates provide Zn for oral ligands with much higher stability constants. Salivary sulfide anion produced during VSC formation is a likely candidate.


1774 (10011)

Evaluation of fluoride-containing toothpastes in Mexico. A. GALICIA-SOSA*1, D. AGUILAR-CRUZ, B. FRONTANA-URIBE1, D. JIMENEZ-FARFAN1, C. LEDESMA-MONTES1, and J. HERNANDEZ-GUERRERO1, 1 UNIVERSIDAD NACIONAL AUTONOMA DE MEXICO, MEXICO DF, Mexico

The most widely used method for applying fluoride topically is by means of toothpaste since almost all dentifrices contain fluoride. However, the early use of fluoride dentrifice and their use in large quantities have been identified as risk factors for dental fluorosis. Little is known about fluoride dentrifice use as a risk for dental fluorosis. It had been reported that children under 6 years swallow the toothpaste until 95% of the dispensed quantity. In 1993, the Mexican government implemented domestic salt fluoridation at 250 to 300 ppm. The objectives of our study were to know the actual concentration of fluoride in toothpastes sold in the Mexican market. 61 fluoridated toothpastes were analyzed using an Orion 720A potentiometer and an Orion BN 96-09 F ion-specific electrode. Fluoride concentration ranged from 0 to 2053 ppm . Mean fluoride concentration was 718.6±582.1). 55.7% of the analyzed samples had a F concentration from 0 to 878.86 ppm F. Of the analyzed samples, 11.5% were infant toothpastes and F concentration varied from 0 to 1153 ppm . Our results demostrate a wide variation in F concentration, and suggest it is necessary to implement an official policy which regulates F concentration in these products. It is important that all manufactures of dentifrices show in the label the total fluoride content of the product and also should print the recommended dosis, in order to prevent dental fluorosis lesions. This study was supported by a grant of CONACyT # 27615-M.


1775 (21033)

Laboratory Toothpaste Cleaning Power Method Parameters. J.J. HEFFERREN*1, B. MARY L.1, C. LORI1, E. EROL1, S. JEFFREY S.1, and N. LI2, 1 University of Kansas, Lawrence, USA, 2 Peking University, Beijing, China

Objective: This study was to review individual characteristics of the established toothpaste Cleaning Power Method (Stookey et al, JDR 61:1236,1984). While this laboratory method has an established correlation with clinical studies, variance of results is higher than desired. Method characteristics more likely to affect the variance were reviewed including tooth surface preparation, pre-stain etching, staining procedure, color measurement of stain, specific site measurements, dilution of toothpaste slurry and number of strokes to remove the stain. While it may be desirable to use the natural surface for specific studies, the removal of the outer, often ridged, surface provided a more consistent and flatter surface for subsequent staining and measurement. Method: Cycling the teeth through the staining medium and under infrared heat lamps with a warm airflow reduced significantly the time required to stain the teeth. This approach produced a multi-layered stain that did not materially affect the stain or its removal. Smaller diameter colorimeter measuring ports coupled with a microscope micrometer positioning device increase the ability to measure the same site before and after treatments and minimized the need for a flatter tooth surface. Results: Stain removal reached a plateau at 3,000 double strokes, thus 3,000 rather than the recommended 1,000 strokes would reduce the variance of results. Tea stain was pH stable, thus a toothpaste pH of 4.5 to 10 will have little effect upon stain removal. Dilution of toothpaste slurry affected the cleaning power of soluble abrasive systems. Conclusion: The bovine tooth Cleaning Power Method remains the preferred laboratory method to assess toothpaste functionality. Supported in part by Church and Dwight. hefferen@ukans.edu


1776 (19638)

Silica as a Reference for Laboratory Toothpaste Assessment Methods. N. LI*, Peking University, Beijing, China, J.J. HEFFERREN, University of Kansas, Lawrence, USA, A. STORECK, Degussa, Hanau, Germany, B. SCHEMEHORN, Indiana University, Indianapolis, USA, and M. LERCH, Gabelmann & Lerch, Mainz, Germany

While there is a multi-year supply of calcium pyrophosphate reference material for laboratory abrasivity and cleaning power methods to assess toothpaste and other oral care products, there has been a continuing desire to have a reference material more representative of current toothpaste ingredients. Objective: This longitudinal collaborative study was to characterize three commercially available toothpaste grade silica products, Sident® 8, 9 and 10. Methods: Representative samples from one lot of each silica were bagged and stored on pallets in environmentally controlled rooms at normal (ISO 554: 23ºC/50%RH) and tropical (40ºC/70%RH) conditions. Samples were analyzed at 4, 12, 24 and 52 weeks. Physicochemical characterization of the silica specimens as well as the clinically predictive abrasivity and cleaning power methods were done to compare samples taken at each time period. Analyses included specific surface area, loss on drying, pH of 5% suspension, viscosity of CMC dispersions, particle size, tamped density (ISO 787-11) and sodium, iron and sulfate. Abrasion levels of the silica samples were tested in two labs using the Radioactive Dentin Abrasivity Method (ISO 11609); in one lab using a profilometric method with acrylic substrate; and in a fourth lab using a copper gravimetric method. Two labs performed stain removal studies using the method of Stookey et. al, (JDR 61: 1236, 1984). Results: There was little difference between samples stored at normal and tropical conditions. Some physicochemical changes of the silica particles may signal possible, future changes in the predictive clinical values of abrasivity and cleaning power. Conclusion: Preliminary analysis of this continuing study indicate one or more of the three silica materials remains unchanged as measured by multiple established laboratory abrasivity and cleaning power methods for toothpaste and thus may be suitable as a reference material. hefferen@ukans.edu


1777 (17774)

Plaque [F] After Using a NaF or Placebo Dentifrice in a Non-fluoridated Community. G.M. WHITFORD*1, M.A.R. BUZALAF2, and M.F.B. BIJELLA2, 1 Medical College of Georgia, Augusta, USA, 2 University of São Paulo, Bauru, Brazil

This 4-week, double-blind, double-crossover study with 16 11-to-15-year-old Brazilian children was done to compare the whole saliva and plaque fluoride concentrations ([F]) associated with the use of a NaF (FD, 1000 ppm F) or F-free placebo (PD) dentifrice. A second objective was to determine the relationship between the plaque concentrations of F and calcium ([Ca]). The protocol was similar to that presented last year (AADR Abst 1618, 2001) except that the subjects were children and their drinking water had a low [F] (< 0.1 ppm). The children used the FD or PD alternately at weekly intervals. At bedtime on the 6th day of each week, the children brushed only the occlusal surfaces of their teeth to allow the accumulation of smooth-surface plaque. They were instructed not to brush again until after saliva and plaque (half mouth) had been collected the next morning immediately after which they brushed the occlusal surfaces for 1.0 min and additional collections were made 1.0 h later. Thus, the collections were made 1.0 h and approximately 12 h after having used the FD or PD. F and Ca were analyzed using the electrode after HMDS-diffusion and by AAS, respectively. The salivary [F] 1 h and 12 h after using the FD (10.4 and 4.6 µmol/L) were significantly higher than those after using the PD (1.0 µmol/L). The plaque [F] 1 h after using the FD (10.2 mmol/kg dry wt) was significantly higher than the 12-h [F] (5.1 mmol/kg) and both of these were significantly higher than the 1-h and 12-h PD [F] (2.8 and 2.2 mmol/kg). Thus, in this non-fluoridated community plaque [F] were consistently higher when the FD was used. These plaque [F], however, ranged from 55% to 79% lower (p < 0.01) than those of adults whose drinking water was optimally fluoridated (AADR Abst 1618, 2001) while the plaque [Ca] of the two studies did not differ significantly. To the extent that the results from these two studies can be compared, they suggest that fluoridated water contributes more than 50% as much fluoride to plaque as a fluoridated dentifrice. In agreement with last year’s findings, there was a strong correlation between plaque [Ca] and [F] under all experimental conditions (p=0.0001).


1778 (14733)

Sodium Hexametaphosphate Chewing Gum Effects On Salivary Conditioning Films. H.J. BUSSCHER*1, H.C. VAN DER MEI1, H.J. KAMMINGA-RASKER1, J. DE VRIES1, and D.J. WHITE2, 1 Department of Biomedical Engineering, University of Groningen, Netherlands, 2 Procter and Gamble Company, Mason, OH, USA

Salivary conditioning films (pellicle) form the interface between teeth and the oral environment. The wettability of oral surfaces in part  dictate biological adhesion phenomena such as plaque formation, calcification and staining and additionally clean  mouth perception. Objectives: This study compares effects of sodium hexametaphosphate chewing gums on the wettability of salivary conditioning films in vitro and in vivo with those of a sodium hexametaphosphate containing dentifrice. Methods: In vitro studies follow protocols detailed by Busscher et al. J Clin Dent 13: 38-43. In laboratory studies, pellicle coated bovine enamel surfaces were prepared by 16 hour immersion in reconstituted saliva buffer.   Toothpaste (1 min.25 wt. % slurry) or chewing gum treatments (immersion 15 minutes or 1 hour in ‘chewing gum stimulated saliva’ were followed by contact angle assessments of surface energy changes and pellicle film thickness via vacuum drying followed by photoelectron spectroscopy (XPS).  In vivo, subjects brushed with Crest Regular for one week and then single treatments were carried out with chewing gum containing or absent hexametaphosphate.  Water contact angles were then assessed on facial incisors.   Results:  Hexametaphosphate gum stimulated saliva produced significant reactivity on oral surfaces, reducing pellicle thickness post treatment by 59 % (15 min. – sig. p < 0.05) and increasing water contact angles + 4 degrees.  Placebo gum stimulated saliva had no effect on film thickness but did decrease contact angles (-2 to -6 degrees).  In vivo, hexametaphosphate gum produced a dramatic reduction in water contact angles (n=5) –23±15° compared to a –10±4°  for placebo gum and  –14±6°  for wax stimulation.  These changes correlate with those observed for hexametaphosphate dentifrice which is shown effective in chemical stain prevention and removal.  Conclusions:  Hexametaphosphate chewing gums were shown to produce marked surface chemistry changes on conditioning film coated surfaces both in vitro and in vivo. 

 


1779 (17914)

Light Transmission Through All-Ceramic Framework and Cement Combinations. D. EDELHOFF*, University of Aachen, Germany, and J. SORENSEN, Oregon Health & Science University, Portland, USA

Objectives: This study quantified the light transmission through all-ceramic frameworks dependent on two luting materials (LM). Methods: Disk shaped specimens (16x0.9mm) were made of various ceramics of shade A3 (Vident): A) Densely sintered Al2O3, EX) Experimental (OHSU-RWTH,IvoclarVivadent(IV)), IA) Infiltrated Al2O3 (In-Ceram(IC) Alumina,Vident), IS) Infiltrated MgAl2O4 (IC Spinell), IAZ) Infiltrated Al2O3/ZrO2 (ICZirconia), L) Lithium disilicate (Empress2,IV), Z) ZrO2-Y2O3 (LAVA,3MESPE). Ceramic disks were covered with a 0.1 mm layer of 1) zinc phospate (Harvard Dental) or 2) dual cured resin cement (Variolink transparent,IV). As reference (3)), uncovered 1 mm ceramic disks were employed. Samples (3/group) were tested after 30 days storage in artificial saliva. Light transmitted through the specimen was determined in a spectrophotometer (DU-7,Beckman) by direct transmission coefficient (tc) [%] for wavelengths (l ) from 400 to 700 nm. Results: Values are given as overall tc, calculated as integral 400-700 tc (l )dl ,means (SD):
 

A

EX

IA

IS

IAZ

L

Z

1)

37.2 (3.0)ab

42.9 (3.8)b

21.6 (1.6)

46.6 (3.2)b

5.6 (0.7)I

31.8 (2.8)a

34.1 (2.3)a

2)

61.8 (5.0)c

400.6 (34.6)

32.4 (1.5)

81.8 (4.0)d

6.3 (0.9)I

77.3 (4.9)d

51.2 (5.8)Zc

3)

55.2 (4.4)

301.7 (47.8)

26.1 (0.3)

78.5 (3.6)

4.9 (0.6)I

66.7 (3.0)

45.3 (1.1)Z

Conclusions: ANOVA showed significant (p<0.05) differences among the overall tc values dependent on type of ceramic and LM (n.s.=same superscript). Overall tc increased significantly when LM-2 was used. Higher translucency ceramics showed greater sensitivity to luting material type than the more opaque ceramics.


1780 (18994)

Natural Tooth Color Mapping using Digital Equipement. A. ÐOZIC*, ACTA, Amsterdam, Netherlands, and A.J. FEILZER, ACTA, Dental Materials Science, Amsterdam, Netherlands

Introduction: Tooth appearance interpretation with the human eye using shade guide tabs is oftenly not effective. Defining tooth color position in the one of the color spaces (Munsels or CIELAB color space) may be useful, but the complexity and the costs of sophisticated instruments make them hardly available for use in the dental offices. Simple digital photgraphy may offer a solution. Objectives: The aim of this study was to characterize natural teeth as well as VITA Shade tabs in terms of L* a* b* color maps obtained by digital photography. Materials and Methods: Patients where selected based on the VITA shade of their tooth #11. VITA shade tabs were mounted in the position of the tooth #11 of a phantom head. Digital photographs were taken (Olympus) according to a standard procedure. Color was measured at nine positions along the 0.5 mm central stroke from cervical to incisal by using the Adobe Photoshop software program. Results: In both groups specific patterns in the L* a* b* color-points composition were recognized. The L* and b* values of both groups didn’t differ siginificantly while the a* values of the natural teeth show more irregular patterns when compared to the VITA shade tabs. Discussion: This result showed the potency for color mapping of a whole tooth surface by extrapolation of the L* a* b* color values of only one part of the surface. However, with this method it may be difficult to determine translucency aspects. Conclusion: Color mapping by use of standardized digital photography may be an useful tool for a dentist to characterize tooth color. The color diversity of tooth surfaces is not always corresponding with that of the shade tabs, particularly in a red-green area (a*). A.Dozic@ACTA.nl


1781 (16393)

Evaluation of an automated color reproduction method for dental porcelain restorations. D. NATHANSON*1, S. NAGAI2, H. YAMAMOTO1, T. SHIOYAMA2, and K. ISHIBASHI3, 1 Boston University, USA, 2 Harvard School of Dental Medicine, Boston, MA, USA, 3 Iwate Medical University, School of Dentistry, USA

Objectives: The purpose of this study is to evaluate a novel computerized color measuring system and an automated color reproduction system for dental porcelain restorations. The method provides porcelain prescriptions to match the color of target teeth by a computerized calculation using a formula based on the Allen’s two constants theory. Methods: The color of the middle third of maxillary central incisors of 500 human volunteers and 62 shade tabs from 3 dental shade guides (VITAPAN CLASSICAL, VITAPAN 3D MASTER and IPS CHROMASCOP) was measured by a spectrophotometer (MSC-2000, Olympus, Japan). 34 subjects (out of 500) showed a dE > 3.6 between the tooth and the closest shade tab, indicating a poor color match. 23 subjects (out of 34 mismatches) volunteered for the evaluation of the automated color reproduction methodology. The ceramic prescription to reproduce the middle area of the target tooth color was calculated using the computerized calculation formula. Layered porcelain specimens were produced using a mix of 4 shades of opaque (5 mm thick) overlaid by one shade of dentin porcelain (1 mm thick). The colors of these specimens were compared to the target teeth by spectrophotometer and visual evaluation using a matching score from 1 (poor match) to 5 (Perfect Match). Results: The mean dE value between the ceramic specimens and the target teeth was 2.3±0.8. The Mean Visual matching score for all specimens was 4.5±0.8. Conclusions: The computerized color measuring and automated color reproduction system tested provided clinically acceptable color reproducibility of porcelain for teeth that were a poor match for conventional shade guides. (dnathan@bu.edu)


1782 (11969)

Evaluation of Newly Developed Visual Shade Matching Apparatus. R.D. PARAVINA*, University of Texas Dental Branch at Houston, USA

Objectives: It is generally considered that shade matching should be done in the daylight. However, daylight constantly changes. An apparatus named "Shademat Visual+" (SV+), which should render optically "ideal" conditions for visual shade matching, has been constructed and its influence on shade matching quality has been investigated. Methods: A group of 129 color normal evaluators, dental students and general dentists, matched the shade of 4 porcelain-fused-to-metal teeth. They were positioned onto the upper member of the artificial head and fastened to the head-rest of the dental chair or SV+. The Vitapan "Classical" shade guide, with the shade tabs arranged according to manufacturers' suggestion (MA), was used for shade matching. Shade matching was also performed with the tabs arranged according to total color difference in relation to the "lightest" tab, including group division (the alternative arrangement - AA). The evaluators matched the shade of artificial teeth both in the daylight (DL) and using the SV+ (artificial light - AL). The color coordinates were determined using digital image analysis. Based on DE* values, each shade matching result was ranked from 1 (the worst match) to 16 (the best match) points. Results: The evaluators achieved better result in AL trials than in DL trials - 13.2±1.1 vs. 12.4±1.2 points (p<.001). Compared to DL, 63.6% of evaluators improved their result, 9.3% showed no difference, while 27.1% achieved worse result in AL. The mean increase in points in AL minus DL trials for the entire group was 4.2. For the same PFM specimen 12.7±2.6 points were recorded with the MA and 13.7±2.5 with the AA (p<.001). Corresponding values for the SM+ trials were 13.6±2.4 and 14.6±1.6 points, respectively (p<.001). Conclusions: SV+ was better than DL for clinical shade matching. Shade tabs should be arranged according to AA.


1783 (10667)

Clinical Comparison of a Spectrophotometric Shade Matching System with Conventional Shade Matching. S. PAUL*, A. PETER, L. RODONI, N. PIETROBON, and C.H.F. HAMMERLE, University of Zurich, Switzerland

Objectives: To test the shade matching of single PFM restorations with the adjacent dentition if the restorations were fabricated either using conventional visual shade matching (conventional crown: CC) or using a new spectrophotometric shade matching system (spectrophotometric crown: SC). Methods: The samples of a Vita Classic shade guide were measured with the spectrophotometer to determine the CIE L*a*b* coordinates. Three dentists with a negative history of visual color deficency independently selected the best match to the upper central incisor needing a restoration on 10 patients. Each patient was standing against a white wall with ceiling lighting of 5000 K away from all windows. Pictures were taken with uniform flash light of each patient's incisor with the selections of best matching (BM) shade guide teeth of all three dentists. The 10 incisors were then measured using a reflectance spectrophotometer (SP). CIE Lab coordinates were directly recorded on the SP's 18x13 square mm detector area using a standard light source (l=400-720 nm). Resulting conventional and spectrophotometric PFM’s were tested intraorally for best match with the adjacent incisor using conventional shade matching vs. spectrophotometric measuring (øDCC, øDSC). The total color difference was calculated (øDCC - øDSC). The three dentists' and patient's choice of crown was selected for final cementation (Choice of Cr.). Results: DE values were significantly higher for conventional crowns compared to spectrophotometric crowns (Mann-Whitney, p<0.01). In 9 of 10 cases spectrophotometric crowns were preferred over conventional crowns when evaluated visually. Conclusion: Spectrophotometric shade matching could be used efficiently fabricating PFM restorations.


1784 (10866)

Variability of Porcelain Color Reproduction by Commercial Laboratories. D. DOUGLAS*, Southern Illinois University at Edwardsville, Alton, USA, and J.D. BREWER, State University of New York at Buffalo, USA

Objectives: Many investigations in the field of metal ceramics have examined materials, manipulative variables and the relationship of these factors to a restoration’s color. However, the affect of the artistic component of restoration fabrication is not known. The purpose of this study was to determine, through instrumental colorimetry, the variability in color reproduction for metal ceramic crowns fabricated by commercial dental laboratory technicians.

Methods: Sixty metal ceramic crowns were fabricated to the same shade specifications by 5 commercial dental laboratories. Color differences (DE) were determined between crowns and the prescribed shade tab. A test for homogeneity of variance was used to assess within lab consistency. Analysis of variance was used to determine if differences in color reproduction existed among labs.

Results: Color reproduction was significantly different among laboratories. Color reproduction for the incisal third was not consistent within the work of the individual technicians; however, no differences in within lab variability existed for the middle third of crowns. Mean color differences from shade tabs for individual labs ranged from 3.5 to 11.1 DE units. Labs were better at matching shades in the incisal third.

Conclusions: The ability to reproduce the color of the target shade tab differed among laboratories. Mean color difference variance among labs was approximately 6 DE units for both middle and incisal thirds. A color discrepancy of this magnitude would be considered a just-tolerable shade match under intraoral conditions. However, the cumulative effect of the variation among labs and the variation within individual technicians was sufficient to have rendered many of the crowns assessed in this study as clinically unacceptable shade matches. This places a premium on accurate shade selection by the dentist.


1785 (12788)

Coverage Error of Three Different Shade Guides in a Japanese Population. A.G. WEE*, and W.M. JOHNSTON, The Ohio State University, Columbus, USA

Objectives: The purposes of this investigation were to determine and to compare the coverage errors (CE's) of three conceptually different shade guides when selecting anterior tooth shades for a Japanese population. The CE's of the following were evaluated: (1) Vita Lumin, (2) Chromascop, (3) Vitapan 3D Master, and (4) the closest shade when all shades of the three shade guides were considered, i.e., the combined method. Methods: The spectral reflectance values of the center 1/9 (1.5 mm diameter) of each shade tab (with a black backing) were measured using a spectroradiometer (PR-750 SpectraScan, Photo Research Inc.) and two external light sources at wavelengths from 380nm to 780nm with a 2.5 nm interval. All spectral reflectance measurements were made using 0 degree observer and 45 degree illumination, and then converted to CIE L*, a* and b* values. The color values of 99 anterior teeth of Japanese subjects were measured with the method of Ishikawa-Nagai S. et al. (IJP, 1994) Using the method of O'Brien WJ et al. for determining CE (IJP, 1991), the minimum CIELAB color differences (Delta E) for each of the subjects’ 99 anterior teeth within each shade guide and within all three guides were determined and averaged. The mean CE's were then statistically analyzed using a Repeated Measures ANOVA. Results: The CE's obtained were: Vita Lumin=9.9(5.6); Chromoscop=11.7(6.2); 3D Master=8.2(5.2); All Three Guides/Combined Method=8.1(5.2). A highly statistically significant difference (p < 0.001) was found among the CE's of the three shade guides and the combined method. Conclusion: Within the limits of this study, the color difference between Japanese subjects' anterior teeth and the closest color-matched shade tab is dependent on the type of shade guide used.


1786 (20058)

Color Stability of MDX4-4210/Type A Maxillofacial Elastomer with Opacifiers and Pigments. S. KIAT-AMNUAY*1, J.C. LEMON2, and J.M. POWERS1, 1 University of Texas Dental Branch at Houston, USA, 2 M.D. Anderson Cancer Center, Houston, TX, USA

Objectives: Color instability often limits the service of facial prostheses and poses esthetic problems for patients. This study determined the effects of opacifiers used at different ratios on the color stability of pigmented MDX4-4210/Type A maxillofacial elastomer after artificial aging. Methods: Seventy-five groups (n=5) were made by variously combining 1 of 5 opacifiers [5%, 10% or 15% of Georgia kaolin [Gk], calcined kaolin [Ck], Artskin white [Aw], titanium white dry pigment [Td], or titanium white oil color [To]] with 1 of 5 dry earth pigments [no pigment [control], cosmetic red, cosmetic yellow ochre, cosmetic burnt sienna, or a mixture of all pigments]. Specimens were artificially aged in an aging chamber. CIE L* a* b* values were measured by spectrophotometer. Color differences ( delta E*) at 150, 300 and 450 kJ/m2 were subjected to 4-way analysis of variance with repeated-measures. Means were compared by Tukey-Kramer intervals at the 0.05 level of significance. Results: Adding dry earth pigments to any of the kaolin groups did not protect silicone MDX4-4210/Type A from color degradation over time. Mixing red pigment in all groups increased delta E* values from 0.2-3.1 up to 6.9-38.6. Additions of 15% of Td, Aw, To, Gk and 10% of Ck showed significantly better color stability compared to other concentrations (p<0.05). Td was the most color stable over time, followed by the pigments mixed with Ck, AW, To and Gk. Conclusions: Inorganic dry earth pigments mixed with opacifiers did not protect the MDX4-4210/Type A silicone elastomer from color degradation over time especially with cosmetic red.


1787 (21046)

Clinical evaluation of electric disinfection during early stages of en-dodontic treatment. B. BENZ*, V. SCHWEIER, and R. HICHEL, Univerity of Munich, Germany

Objectives: A fast and effective endodontic therapy is especially important in patients suffering from acute pulpal pain. In-vitro studies were able to demonstrate the efficacy of a novel electronic device in eliminating organic material (pulpal tissue and bacteria). This system (Endox, Lysis) sends high energy AC-pulses through an active electrode placed in the root canal. Whenever or-ganic material is present, the electric current leads to a considerable temperature increase (600 to 800 °C). Methods: The purpose of this clinical study was to evaluate the effect of the electric disinfection in comparison to a conventional endodontic regimen on the pain perception during the treatment of acute pulpal pain. 48 patients (50 teeth) were randomly allocated either to the AC or the conven-tional group. The pulp chambers were opened and the coronal part was cleaned. In the conven-tional group the root canals were then instrumented up to ISO size 30, rinsed with NaOCl (2.5%) and dried. In the AC group, depending on the clinical situation, up to three AC-impulses were ap-plied. After placing CaOH all cavities were closed using a temporary restorative material (Cavit, ESPE, Germany). During treatment as well as one, two and 7 days later the patients rated their pain perception on a visual analogue scale. Results: In the conventional group patients reported an average pain level above zero during treat-ment and the first postoperative day. In the AC-group pain perception was reported zero from the moment of the application of the AC-current on. The treatment time in the conventional group aver-aged 28 minutes and 17 minutes in the AC-group. Conclusions: The results of this study indicate that the use of electric disinfection in the treatment of acute pulpal pain may reduce pain perception as well as treatment time in comparison to a conventional endodontic regime.


1788 (19185)

Substantive antimicrobial activity in chlorhexidine-treated human root dentin. B.R. BASRANI*, J.M. SANTOS, L. TJÄDERHANE, H.P. LAWRENCE, and S. FRIEDMAN, University of Toronto, Canada

Introduction: Prevention of re-infection after endodontic therapy is an important goal. This study assessed antimicrobial activity in chlorhexidine-treated human root dentin. Methods: Canals of 98 roots were enlarged to standard size with Gates Glidden # 3 drills and medicated for 7 d with: (1) 2% chlorhexidine gel, (2) 0.2% chlorhexidine gel, (3) 2% chlorhexidine solution, (4) Ca(OH)2, (5) Ca (OH)2 + 0.2% chlorhexidine gel, (6) 2% chlorhexidine solution + 25% chlorhexidine-containing controlled-release device, (7) saline, and (8) gel vehicle. After washing, canals were inoculated with E. faecalis for 21 d. Dentin samples, obtained by enlarging canals with Gates-Glidden drills #4 and #5, were collected in vials containing BHI broth and incubated for 72 hrs. Results: Mean optical density values were significantly lower for groups 1, 3 and 6 than for groups 7 and 8. Other groups did not differ significantly from the controls. Conclusion: Root canal dressing for one week with 2% CHX affected antimicrobial activity against E. faecalis for at least 21 d.


1789 (14672)

Herpesvirus DNA Detection and Transcription in Periapical Lesions. M.A. SABETI*1, H. NOWZARI1, Y. VALLES2, V. KERMANI2, and J. SLOTS1, 1 University of Southern California School of Dentistry, Los Angeles, USA, 2 Immuno-Biogene, Inc, Los Angeles, CA, USA

Objectives: Recent studies have implicated members of the family Herpesviridae, and in particular herpesvirus reactivation, in the etio-pathogenesis of aggressive periodontitis. In this study, RT-PCR method was used to detect human cytomegalovirus (HMCV), Epstein-Barr virus (EBV) and herpes simplex virus (HSV) in 8 symptomatic recalcitrant periapical lesions and in 1 asymptomatic healthy periapical site (control). Methods: Periapical samples were collected in conjunction with periapical surgery and kept frozen until virologic examination. RNA was isolated from tissues by using a guanidinium isothiosyanate-acid phenol procedure (Trizol, GIBCO Laboratories) according to the manufacturer’s instructions. cDNA was generated using pre-amplification kit with oligo (dt) and random hexamers (GIBCO). Primers for RT-PCR were employed for highly conserved regions of each virus. PCR standardization of primer sensitivity and validation was carried out according to established methods. Amplification products were identified by means of gel electrophoresis. Results: HCMV transcripts were detected in all 8 test lesions, EBV transcripts in 4 lesions, and HSV transcripts were not demonstrated in any site. No transcription was detected in the control site. Conclusion: Our data suggest that productive HCMV and EBV infections participate in the pathogenesis of periapical symptomatic lesions. Mechanisms by which herpesviruses might contribute to acute periapical inflammation are discussed.


1790 (17429)

The use of species- and genus-specific PCR primers to identify bacteria in endodontic infections. A.F. FOUAD*, J. BARRY, Q. ZHU, M. CAIMANO, M. CLAWSON, R. CARVER, K. HAZLETT, and J.D. RADOLF, University of Connecticut Health Center, Farmington, USA

The microbial pathogens in endodontic infections have not been adequately characterized using molecular techniques. Objectives: The purpose of this study was to identify the presence of ten putative bacterial pathogens in root canals with necrotic pulp using PCR-based methods. The association of these microorganisms with clinical symptoms was also investigated. Methods: Microbial specimens were obtained from the root canals of 24 teeth with necrotic pulp. Preoperative clinical symptoms were dichotomized into two categories (positive and negative) based on a visual analog scale for pain, objective clinical findings and the presence of swelling. Species-level PCR primers, that target the bacterial 16S rRNA genes of Bacteroides forsythus, Fusobacterium nucleatum, Peptostreptococcus micros, Porphyromonas endodontalis, P. gingivalis, Prevotella intermedia, P. nigrescens, Streptococcus intermedius, Treponema denticola and the tuf gene for Enterococcus genus were used. Universal bacterial primers for the 16S rRNA gene were also used. Results: PCR with universal primers identified bacterial DNA in 22 specimens; the remaining two were from intact teeth that were traumatized 6 months prior to treatment. PCR with specific primers showed that F. nucleatum was the most prevalent organism detected. Preoperative symptoms were significantly associated with the presence of S. intermedius (Chi-square, p < 0.001) and the combination of F. nucleatum and S. intermedius (Chi-square, p=0.014), and were positively associated with F. nucleatum (odds ratio=3.2) and P. gingivalis (odds ratio=2.1). Conclusion: Both gram-positive and gram-negative organisms were significant in this patient population. (Supported by a grant from the American Association of Endodontists Foundation, and NIH grants AI-26756, AI-29735 and M01RR06192.)


1791 (16432)

4-META Resin inhibits the Proliferation of Oral Bacteria. S. MIYAKOSHI*, T. INOUE, K. MATSUZAKA, Y. KOIKE, and M. SHIMONO, Tokyo Dental College, Chiba, Japan

Objectives:The aim of this study was to elucidate the effect of 4-META/MMA-TBB resin (4-META resin) on the proliferation of oral bacteria in dentinal cavities. Methods:An in vivo study using oral bacteria isolated from dental plaque and saliva of beagle dogs was carried out as follows. Class V cavities were prepared at inscisors of beagle dogs and treated with 3% ferric chloride in 10% citric acid solution followed by washing and air drying. Bacteria suspended solution was applied to the dentin of the cavity floor. These teeth were divided into 3 groups. The 1st group; the teeth were extracted 3min. after bacterial solution application. The 2nd group; the cavities were applied with 4-META resin 3min. after bacterial solution application. The 3rd group; the cavities were left without application with 4-META resin. After 3 months, all the experimental teeth were extracted. And all the extracted teeth were examined morphologically. Results:As a result, in the 1st group, bacteria were found at the shallow area in the dentinal tubles. In the 3rd group, bacteria were found not only in the shallow area but in the deep area of dentinal tubles. On the other hand, in the 2nd group, a new layer containg many small particles which should be assigned to be bacteria was formed on a hybrid layer. But no bacteria were found in the dentinal tubles under a hybrid layer. Conclusions:These results suggest that 4-META resin application inhibited the proliferation of bacteria in the dentinal tubles. This study was supported by TDCHRC982A01.


1792 (20776)

Antibacterial Efficiency Of 10 Root Canal Cements On Aerobe And Anaerobe Microorganisms. . ANGUIANO P. R;.JÚAREZ O.M.; PEREA MEJÍA L.M.;GARCÍA ARANDA R.L*, Universidad Nacional Autonoma de Mexico, Mexico D.F, Mexico

Objectives: The aim of this study was to test the antimicrobial efficiency of ten root canal sealers against frequent aerobic and anaerobic microorganisms present in pulp diseases was determined by an in vitro study using two different tests: Methods: diffusion in agar and dilution broth. Evaluated cements were: Endomethasone, N2, FS, Proco-Sol, Pulp Canal Sealer, Roth Endo, Sealapex, Silco, Tubli-Seal, Viarden. While microorganisms used were: S. mitis, S. mutans, S. sanguis, S. salivarius, P. endodontalis y P. gingivalis. Antimicrobial effect for each test was evaluated in different ways. While diffusion test in agar inhibition growth of bacteria halo was evaluated for each cement placed in a 5mm diameter ditch, for the dilution broth test inhibition of bacteria growth percentage was evaluated for each cement placed in 5 x 4 mm cylinders and placed in a culture broth with each bacteria. Results: Diffusion technique in Endomethasone plate showed the best inhibition wit an average of 1.21 mm of inhibition for all bacteria, while tubliseal showed the lowest inhibition with an average of 0.2mm. In dilution technique N2 showed the highest antimicrobial activity with an average inhibition of 57% for aerobic bacteria, while the lowest percentage corresponded to procosol, with an average of 5%. For anaerobe microorganisms results were variable according to the tested m.o., being P. Gingivalis more sensitive than P. endodontalis with an inhibition percentage average higher than 65%. Some cements could not be evaluated through this technique because they were diluted in the used mediums. Conclusions: Dilution technique is an alternative technique for antimicrobial efficiency evaluation for root canal sealers, which does not depend on the diffusion capacity of its components in a solid medium, different form the diffusion in agar technique; nevertheless, it is limited by the dilution presented by some cements in the used mediums for bacteria growth.


1793 (20465)

Bond strengths of resin-based composite to Ca(OH)2-treated dentin. W.C. WINDLEY, III*, A.V. RITTER, and M. TROPE, University of North Carolina at Chapel Hill, USA

Objectives:  The purpose of this study was to evaluate the influence of calcium hydroxide (CH) treatment on the bond strengths of a resin-based composite material to bovine dentinMethods:  Thirty bovine incisors were mounted in acrylic, ground flat to expose middle dentin, polished to 600-grit, and randomly assigned to two groups (n=15): (1) 7 day storage in distilled water - control; (2) 7 day application of CH paste.  All specimens were stored in an incubator at 37OC.  Specimens were then retrieved and had the dentin surface rinsed with air/water spray from a triple syringe.  Dentin was etched with 37% phosphoric acid (PA) for 15 s, rinsed, blot dried, and coated with Single Bond (3M ESPE) adhesive according to manufacturer’s instructions.  The adhesive was light cured for 10 s and a resin-based composite (Filtek Z250, 3M ESPE) was applied to the surface with a #5 gelatin capsule (4.5 mm – internal diameter) and light cured.  Specimens were loaded in shear using an Instron universal testing machine at a crosshead speed of 0.5mm/min.  Shear bond strengths (SBS) were calculated by dividing failure load by bonded surface area.  Results: (mean SBS[SE], in MPa): Control: 12.9 (1.6); CH-treated: 15 (1.6).  ANOVA did not reveal statistically significant difference between the two groups (p=0.647).  Conclusions:Calcium hydroxide treatment for 7 days did not affect dentin bond strengths for the ethanol-based adhesive tested.


1794 (20230)

Effect of NaOCl and EDTA on mercury release from dental amalgam. I. ROTSTEIN*1, M. KARAWANI2, S. SAHAR-HELFT2, C. MOR2, and D. STEINBERG2, 1 University of Southern California, Los Angeles, USA, 2 Hebrew University-Hadassah, Jerusalem, Israel

Objectives: To assess the effect of NaOCl and EDTA on mercury release from dental amalgam in vitro using a cold-vapour atomic absorption Mercury Analyzer System. Methods: Fifty-six samples of zinc-free palladium-enriched, high-copper dental amalgam (Valiant Ph.D.) of similar size were prepared and exposed to 10 mL solution of either 1% NaOCl, 3% NaOCl, 10% EDTA in 1%ÝNaOCl or 10% EDTA in 3%ÝNaOCl for periods of 20, 40 and 60 minutes. EDTA, distilled water and phosphate buffer served as controls. Mercury concentrations in solution were measured and the differences between the groups were statistically analyzed. Results: All amalgam samples exposed to 1% NaOCl and 3% NaOCl either alone or in combination with EDTA released mercury into solution. Mercury release was significantly higher in the test groups as compared to the controls (p<0.001). Increase in the mean concentration levels of mercury in solution was time-dependent and directly related to NaOCl concentration. The addition of EDTA caused a decrease in mercury levels detected in solution. This was more significant in amalgam exposed to 1% NaOCl combined with EDTA (p<0.001). Conclusions: NaOCl solutions commonly used as root canal irrigants may alter certain chemo-physical properties of amalgam when used as sealant for root perforation, by enhancing mercury release.


1795 (10897)

Effects of Zinc on Fungicidal Activity of Salivary Histatin Peptides. C.P. GOINS*, M.M. JEFFERSON, and E.L. THOMAS, University of Tennessee, Memphis, USA

Histatins are histidine-rich antimicrobial peptides found in human saliva. Histatins are important in resistance to oral fungal infections but also have antibacterial activity. Previously we found that histatin killing of E. coli bacteria was blocked by the chelator citrate and restored by zinc. Objectives: Our aims were to determine whether chelators block histatin fungicidal activity and whether zinc promotes activity. Methods: Candida albicans cells (105/ml) were incubated 90 min at 30°C in 10 mM sodium phosphate pH 7.4 buffer with histatins purified from human parotid saliva or with synthetic histatin-5. Viability was determined by plating. Results: The chelator EGTA (100 µM) partially inhibited killing but did not block histatin activity. Adding low levels of zinc (1 to 10 µM) in the absence of chelators promoted histatin activity, but high levels of zinc (50 to 100 µM) blocked activity. Zinc without histatins had no effect on viability. Oxygen uptake by C. albicans cells was measured with an oxygen electrode to determine whether effects of zinc on histatin activity were related to zinc inhibition of fungal metabolism. Zinc (100 µM) inhibited mitochondrial respiration by 67 ± 4%, but low levels of magnesium (1 to 100 µM) protected against inhibition by zinc. Magnesium had no effect on promotion or blocking of histatin activity by zinc, indicating that these effects of zinc were unrelated to zinc inhibition of mitochondrial energy metabolism. Conclusions: (1) In a low ionic strength medium, histatins can kill C. albicans without zinc or other divalent cations in the medium; (2) Low levels of zinc (lower than the histatin concentration) promote fungicidal activity; (3) High levels of zinc block histatin fungicidal activity.


1796 (11926)

Salivary Histatin 5 Causes Cell Size Reduction and G0/G1 Cell Cycle Arrest in Candida albicans. X.S. LI*1, D. BAEV1, P.C. KENG2, and M. EDGERTON1, 1 State University of New York,at Buffalo, USA, 2 University of Rochester, NY, USA

Objectives: Salivary Histatins (Hsts) have potent in vitro candidacidal activity and induce ATP efflux from C. albicans without cytolysis. We constructed a C. albicans strain with a chromosomally encoded human salivary Hst 5 gene under the control of a regulated promoter to study the mechanism of Hst 5 fungicidal activity. Intracellular expression of Hst 5 resulted in tandom ATP efflux and cell killing comparable to that of exogenously added Hst 5. Cell cytotoxicity after 24h induction of Hst 5 caused 63% reduction in total cell viability. Methods: FACScan and microscopic analysis of induced (+Hst 5) and non-induced (-Hst 5) C. albicans cells found that induced cultures had substantially reduced mean cell size. To determine whether this small cell phenotype represented nonviable cells, induced and non-induced cell populations were sorted by cell size using flow cytometry and the viability of large and small cells was assessed by plating. Results: Nearly all (95%) large cells were viable, however, only 35% of small cells could replicate. Since yeast require a critical size to enter the cell cycle, we examined whether the small cell phenotype in induced (+Hst 5) cells was related to cell cycle arrest. C. albicans cells were stained with the DNA-specific fluorescent dye Sytox Green and the DNA content was analyzed by Modfit software using FACScan data. Expression of Hst 5 in C. albicans increased the percentage of cells in G0-G1 from 34% to 62%. Small cells collected by cell sorting from induced (+Hst 5) cultures were found to be exclusively (92%) in G0-G1 phase, whereas only 38 % of large cells from this population were in G0-G1 phase. Conclusions: These data suggest that cytotoxicity resulting from intracellular expression of Hst 5 in C. albicans may be related to reduction in cell size and G0-G1 cell-cycle arrest.


1797 (18152)

Generation of reactive oxygen species and chromosomal changes following Hst 5 treatment of Candida albicans. D.E. WUNDER*1, J. DONG1, J. DONG, D. BAEV1, D. BAEV, M. EDGERTON1, and M. EDGERTON, 1 SUNY at Buffalo, NY, USA

Objectives: Salivary Histatins (Hsts) are potent candidacidal proteins that induce a non-lytic form of cell death in C. albicans. This laboratory constructed a C. albicans strain that expresses a chromosomally encoded human salivary Hst 5 gene under regulation of an inducible promoter (DB9). DB9 has reduced viability and a significant decrease in mean cell volume associated with induction of Hst 5 compared to control strains. Since cell volume reduction is often a first sign of programmed cell death (PCD), we investigated a number of PCD related parameters, namely generation of reactive oxygen species (ROS) and protein carbonyl groups, chromosomal fragmentation (laddering), and cytochrome c release to determine if PCD plays a potential role in Hst 5 mediated toxicity in C. albicans. Methods: ROS generation in DB9 and control strains was monitored using the fluorescent dye H2DCFDA applied to cellular extracts of DB9 and control strains. Western blot analysis of cell protein extracts was used to qualitatively assess generation of protein carbonyl groups related to oxidative stress. Chromosomal fragmentation analysis of isolated genomic DNA from test strains was performed using agarose gel electrophoresis followed by DNA staining. Cytochrome c release was determined by Western blots of Hst 5 treated mitochondria isolated from C. albicans cells using an antibody to yeast cytochrome c. Results: An increase in ROS generation was noted in induced DB9 cells compared to uniduced cells, however Western blot analysis to failed to detect increased levels of protein carbonyl groups in induced cells. There was no evidence of chromosomal laddering and cytochrome c release was not observed following treatment of C. albicans mitochondria with Hst 5. Conclusion: These data, with the exception of an increase in ROS in induced DB9, seem to rule out PCD as a potential mechanism of action of Hst 5 mediated cytotoxicity.


1798 (17899)

Human Salivary MUC7 Mucin Peptides: Effect of Size, Charge and Cysteine Residues on Antifungal Activity. L.A. BOBEK*, S. MASHHOON, and H. SITU, University at Buffalo, The State University of New York, USA

Objectives: We have shown that MUC7 20-mer: N-L32AHQKPFIRKSYKCLHKRCR51-C (residues 32-51 of MUC7) possesses broad-spectrum antimicrobial activity. The aims of this study were to determine the minimum peptide length and its location within the 20-mer region required for potent antifungal activity, and to examine the effect of peptide charge as well as the role of cysteine residues on the fungicidal activity. Methods: The following MUC7 peptides were custom-synthesized: A) unaltered 20-mer fragments: 16-mer (residue 36-51), 12-mer (residues 40-51), 11-mer (residues 41-51), 10-mer (residues 42-51), 8-mer (residues 44-51), 8-mer-N (residues 32-39, or the N-terminus); B) altered 12-mer peptides: 12-mer-2 (Cys residues at positions 45 and 50 substituted by Ala), 12-mer-3 (Arg 40 and Lys 41 substituted by Ala), 12-mer-4 (Arg 40, Lys 41, Lys 44, Lys 48, Arg 49 and Arg 51 substituted by Ala). These peptides, and the positive and negative control peptides, magainin II (23 residues) and insulin chain A (21 residues), respectively, were incubated at 370C for 1.5 hours with C. albicans and C. neoformans (105 cells/ml). Cell viabilities were determined by a colony-forming assay. Results: The following fungicidal activities, expressed in ED50 values (mM), were obtained for C. albicans: 16-mer: 2.0, 12-mer: 2.2, 11-mer: 3.2, 10-mer: 20.7, 8-mer: 23.2, 8-mer-N and insulin: no activity; altered peptides: 12-mer-2: 2.1, 12-mer-3: 14.6, 12-mer-4: no activity. The MUC7 peptides were as effective or more effective against C. neoformans. Conclusions: The MUC7 12-mer and 11-mer, located at the C-terminal region of MUC7 20-mer and containing large number of positively charged residues, constitute the minimum size required for fungicidal activities comparable to that of MUC7 20-mer. Furthermore, cysteine residues are not important, while the positively charged residues are very important for the fungicidal activity of these peptides. Supported by NIH/NIDCR grant DE09820.


1799 (20787)

Fungicidal activity of human salivary MUC7 20-mer and mode of interaction at the membrane. C.J. SMITH*, H. SITU, and L.A. BOBEK, University at Buffalo, The State University of New York, USA

Objectives: To determine the effect of MUC7 20-mer (residues 32-51 of MUC7 with the following sequence: N-LAHQKPFIRKSYKCLHKRCR-C) on Candida albicans cellular membrane integrity, to examine whether it interacts with a specific fungal membrane protein(s), and if it exerts differential activity towards blastoconidia and germ tube forms of Candida albicans. Methods: Transmembrane potential was measured to monitor permeabilization using the dye DiSC3(5) for fungi exposed to 18 mM of 20-mer, magainin II, histatin-5,12-mer (N-terminal truncation of 20-mer) and 12-mer without charge using a fluorescence spectrofluorimeter over 25 minutes. Protein interaction at the membrane was examined by overlay assay with biotin labeled 20-mer and membrane derived proteins from C. albicans, C. neoformans, and S. cerevisiae prepared by glass bead disruption and sequential centrifugation. Differential activity of 20-mer towards blastoconidia and germ tube forms was carried out by incubating 6.6 x105 cells of Candida albicans in RPMI at 370C for 3 hours, centrifuging cells to remove medium, and conducting CFU assays by incubating blastoconidia and germ tubes with varying concentrations of 20-mer followed by dilution and plating on Saboraud dextrose plates. Results: Transmembrane potential experiments indicate that MUC7 20-mer and 12-mer cause significant permeabilization allowing dye efflux over 25 minutes that exceeds that caused by histatin-5 or magainin II. Elimination of charge in the 12-mer resulted in loss of permeabilization. MUC7 20-mer bound a variety of membrane proteins of all 3 fungal strains tested, indicating its non-specific interaction with cell membrane. No major difference between the activities of 20-mer on blastoconidia and germ tubes was observed. Conclusions: MUC7 20-mer causes dissipation of Candida albicans cytoplasmic transmembrane potential, and its interaction with cell membrane, unlike Histatin-5, seems nonspecific. No major discrepancy exists between the activities exerted by 20-mer on different forms of Candida albicans. Supported by NIH/NIDCR grants DE09820 and DE07301.

 

 

 

 


1800 (19742)

Assessment of the Factors that Mask the Fungicidal Activity of Parotid Saliva. B. FLORA*, E.J. HELMERHORST, H. GUSMAN, R.F. TROXLER, and F.G. OPPENHEIM, Boston University Goldman School of Dental Medicine, MA, USA

Histatins, lysozyme, lactoferrin and peroxidase are human salivary proteins that exhibit antifungal activity when tested as single components in vitro. Intact salivary secretions, however, do not display the activity expected from the contributions made by the individual proteins. Objectives: The present study focuses on the factors that altered the antifungal activity of these proteins in saliva. Methods: Since it is known that some of these fungicidal proteins are inhibited by salt, parotid secretion was collected, dialyzed with membrane tubing with a MWCO of 500, 1,000 and 10,000 Da, and tested separately for their activity against the oral opportunistic pathogen, Candida albicans. Results: Incubation of blastoconidia (OD620 0.5) for 1.5 hr at 37ºC with parotid saliva undialyzed or dialyzed with tubings with MWCO 500, 1,000, and 10,000 showed that dialysis with tubing with MWCO 1,000 and 10,000 resulted in Candida killing (50% and 100%, respectively). A dilution series of parotid saliva dialyzed with membrane tubing with a MWCO of 10,000 Da showed a dose-dependent killing effect against C. albicans. The same observations were made with parotid secretion collected from another subject. Electrophoretic analysis of protein from the dialyzed saliva samples on SDS and basic gels revealed that histatins were only partially removed upon dialysis despite the fact that the major histatins range in MW between 3,000 and 5,000 Da. Conclusions: The observed fungicidal activity of the dialyzed samples can therefore be ascribed either to the retained histatins, or to lysozyme, lactoferrin and peroxidase, since the latter three proteins have molecular weights > 10,000. The fact that fungicidal activity of histatins is inhibited by ions could explain their activation upon dialysis of salivary secretions. This dialysis procedure could be useful to test and compare the antifungal potential of saliva from healthy individuals and from patients suffering from oral candidiasis. Supported by NIH/NIDCR grants DE05672 and DE07652.


1801 (19430)

Salivary IgA responses during treatment of aggressive periodontitis patients. S. HÄGEWALD*1, D. FISHEL2, J.-P. BERNIMOULIN1, and C. CHRISTAN1, 1 Humboldt University Berlin, Germany, 2 Harvard University, Boston, MA, USA

Salivary IgA antibodies are important components of the mucosal immune defense system in the oral cavity. However, their correlation to aggressive periodontitis is still not clear. Objective: The aim of this longitudinal study was to evaluate the change of total and Porphyromonas gingivalis-reactive IgA in saliva during treatment of aggressive periodontitis patients. Methods: 22 patients with previously untreated, active aggressive periodontitis were included. Each patient underwent several visits of oral hygiene instructions, full-mouth professional tooth cleaning and subgingival scaling and root planing (SRP) under local anesthesia. Three months later, patients were randomly assigned to antibiotic treatment by doxycycline or amoxycyline and metronidazole. Patients were reevaluated at 3 and 6 months following antibiotic treatment. Seven sets of resting and stimulated whole saliva samples were collected from each patient throughout the treatment phases. Total IgA and IgA reactive to Porphyromonas gingivalis ATCC 33277 were determined by ELISA. Non-parametric statistics were done by SPSS 9.0 (SPSS, Chicago, USA). Results: All patients showed significant improvements in the clinical parameters from baseline to the completion of the study. Between baseline and 4 weeks following SRP, a significant decrease in total IgA was noted in resting (P=0.002) and stimulated (P=0.005) saliva. Twelve weeks after SRP, total IgA increased to levels not statistically different from baseline. The use of antibiotics did not yield significant changes. P. gingivalis-reactive IgA concentration was not statistically different to baseline at any timepoint. The IgA specific activity, i.e. the fraction of specific to total IgA, was significantly increased at 4 weeks after SRP (P<0.002) but was not different after antibiotic treatment. Conclusions: SRP in aggressive periodontitis patients resulted in a transient reduction of total salivary IgA along with an the increase in the specific activity, indicating an altered mucosal immune response accompanying the reduction in bacterial load.


1802 (21728)

Psychological stress as a determinant of saliva protein composition and saliva-mediated adherence and co-adherence. J.A. BOSCH*1, E.C.I. VEERMAN2, K. NAZMI2, and A.V. NIEUW AMERONGEN2, 1 Ohio State University, Columbus, USA, 2 ACTA, Amsterdam, Netherlands

Objectives: Psychological stress has been identified as a risk factor in the development infectious oral diseases. The salivary proteins play a key role in the regulation of oral microflora and the maintenance of oral health. Therefore, we investigated the effects of experimental stressors on saliva composition and saliva-mediated microbial adherence and coadherence (ex vivo).

Methods: Thirty-two male undergraduates provided unstimulated saliva before and during (1) a time-pressured memory test, (2) a distressing surgery video, and (3) a control condition. We tested the adherence of viridans streptococci (viz., Streptococcus sanguis, Streptococcus gordonii, and Streptococcus mitis) to saliva-coated microplates. In addition, we tested the adherence of Candida albicans to saliva-coated layers of S. gordonii. Correlation analyses were performed to determine the relationships between changes in microbial adherence and changes in the concentration and output of potential salivary ligands (viz., cystatin S, the mucins MUC5B and MUC7, S-IgA, lactoferrin, a-amylase, and total salivary protein).

Results: Stress enhanced saliva-mediated adherence between 200% and 25% (p<.001), in the following order; S. sanguis > S. gordonii > S. mitis. The co-adherence between Candida albicans and S. gordonii was decreased during stress (p<.05). Moderately high correlations were observed between stress-induced changes in MUC7 and changes in the adherence of S. sanguis and S. gordonii (r>.50; p<.01). Other proteins that correlated with changes in adherence were lactoferrin, a-amylase, and total salivary protein. Changes in adherence and co-adherence were independent of changes in salivary flow rate.

Conclusions: The results show that even moderate stressors, by altering salivary protein composition, may affect basic colonization processes such as adherence and coadherence. This study hereby presents a mechanism by which stress may affect plaque formation and susceptibility to oral disease.


1803 (12158)

In vitro evaluation of five root canal sealer's antibacterial activity using two different methods. F.K. COBANKARA1, H.C. ALTINOZ*1, O. ERGANIS2, and S. BELLI1, 1 Selcuk University, Faculty of Dentistry, Konya, Turkey, 2 Selcuk University, Faculty of Veterinary, Konya, Turkey

- Objectives: The aim of this in vitro study was to evaluate the antibacterial activity of a polydimethylsiloxane based endodontic sealer (Roeko Seal, Roeko, Langenau, Germany), a ZOE-based endodontic sealer (Sultan, Sultan Chemists, Inc., Englewood), a glass ionomer based endodontic sealer (Ketac-Endo, ESPE, GBMH & Co., Seefeld-Oberbay, Germany), an epoxy resin based endodontic sealer (AH-Plus, Dentsply, De Trey, Konstanz, Germany) and a calcium hydroxide based endodontic sealer (Sealapex, Kerr, Romulus. MI, U.S.A.) with the use of E.feacalis as a test organism. - Methods: An agar diffusion test (ADT) and a direct contact test (DCT) were used. For the DCT, the sealers were mixed and placed on the side wall of microtiter plate wells. A 10 mL bacterial suspension was placed on the tested material samples. Bacteria were allowed to directly contact to the sealers. The first measurement was done after one hour through every 30 minutes for 19 hours by spectrofotometrically using an Anthos Labtec HT 2 . For the ADT, a 200 mL bacterial suspension was spread on BHI agar plates. Measurements were done after 24 h, 7, 14 and 21 days. - Results: DCT results showed that Ketac-Endo was a significantly more potent baterial growth inhibitor than Sealapex and RoekoSeal (p<0.05). Sultan and AH Plus were gave similar results with Ketac-Endo (not sig.). According to ADT, Roeko Seal showed the lowest and Sealapex showed the highest antibacterial activity when compared to the others (p<0.05). - Conclusions: The antibacterial efficiancy of the materials were varied according to the tests used. It was concluded that the technique, the time or ingredients of the tested materials effects the results of the microbiological studies.


1804 (18376)

Biocompatibility of three adhesive systems. H.M. TEIXEIRA*1, A.B.L. NASCIMENTO1, and C.A.S. COSTA2, 1 Pernambuco Dental School - UPE, Recife, Brazil, 2 Araraquara Dental School - UNESP, Brazil

Objectives: The aim of this in vivo study was to evaluate the biocompatibility of three adhesive systems and a hard-setting calcium hydroxide cement. Methods: Sixty polyethylene tubes filled with the experimental dental materials which were hand-mixed or light-cured according to manufacture´s recommendations: Group 1: Prime & Bond NT (PB – DENTSPLY); Group 2: Bond 1 (BO – JENERIC/PENTRON); Group 3: Optibond Solo (OP – KERR); and Group 4: Calcium Hidroxide – Dycal (CH – DENTSPLY). The materials were implanted into connective tissue of rats. After 15, 30 and 60 days, the implants were surgically excised and the animals killed. Following fixation for 48 hours in Karnovsky (pH 7,2) the specimens were processed for microscopic examination. Sections of 6 mm thickness were stained with hematoxylin and eosin and Masson’s trichrome. Results: At short-term evaluation (15 days) the bonding agents elicited a moderate-intense inflammatory connective reaction. Several venules, macrophages and a few giant cells adjacent to the tube openings gave rise to a thick capsule. These histological findings were less significant to OP. On the other hand, a discrete inflammatory reaction associated with thin fibrous capsule was observed to CH. With time, the connective healing was observed for all dental materials even through many specimens exhibited a persistent inflammatory reaction mediated by macrophages and giant cells. In group 4 (CH) complete healing associated to a thin fibrous capsule was observed at 30 days. Conclusion: It was concluded that all experimental dental materials evaluated were successfully walled off by the connective tissue of the rat. However, CH was less irritant and better tolerated by the connective tissue than the experimental bonding agents which may release their components triggering a persistent inflammatory reaction.


1805 (18525)

Pulpal cell reaction to Bis-GMA adhesive resin. K. MISHIMA*, M. FUJITANI, R. ODA, Y. NOMURA, T. TAKATA, and H. SHINTANI, Japan

Objectives: To develop biocompatible adhesives cellular response of rat pulpal cell to Bis-GMA adhesive resin was investigated. Methods: Clearfil Linerbond 2V (Kuraray, Japan) was polymerized in two different ways (one in air at room temperature for 24 hours and the other under CO2 at 60°C for 24 hours). Pulpal cells were isolated from incisors of Lewis rats with an enzymatic treatment (0.2% collagenase and 0.25% trypsin). The cells were seeded on the resins at an initial density of 1.5 x 104 cells / cm2, and cultured with DMEM + 10% FBS. 1) The number of cells was counted after 1, 3, 7 and 14 to examine the influence of the unpolymerized superficial layer, 2) Identification of dissoluted ingredients from the internal part of the anaerobically polymerized resin was performed, 3) Their concentration change with time was measured by GCMS, 4) Cell response to the ingredients was examined, and 5) Cell proliferation was examined on the resin which was preincubated in the medium for 24 hours for releasing the ingredients. Results: The unpolymerized resin layer caused fatal damage to the cells. The anaerobically polymerized resin also significantly reduced the proliferation (t-test, p<0.01). Dissolution of CQ, HEMA and reducing agents was mostly admitted within first 24 hours. The cell proliferation was slightly improved on the 24 hour-preincubated resin but was still restrained compared with the control, though it was not severely inhibited by each ingredient in such elution concentrations (p<0.01). Our other studies suggest that acute toxicity due to high degree of local concentration of the disoluting ingredients or the genotoxicity might inhibit the proliferation of the pulpal cell. Conclusions: Both the unpolymerized resin layer and the dissoluted ingredients of Bis-GMA adhesive might affect the proliferation of rat pulpal cells.


1806 (20354)

Biocompatibility test of hard-setting cements employing the implantation method. J.T. BACALHAU, Araraquara Dental School-UNESP, Brazil, A.B.L. NASCIMENTO*, Pernambuco Dental School - UPE, Recife, Brazil, J. URIBE-ECHEVARRÍA, Cordoba School of Dentistry, Argentina, C.A.S. COSTA, Araraquara Dental School - UNESP, Brazil, and N.N. URIBE-ECHEVARRÍA, Centro Dental Privado - CDP, Cordoba, Argentina

Objective: Evaluate the biocompatibility of three different hard-setting cements when implanted into subcutaneous tissue of rats. Methods: Forty-five polyethylene tubes were autoclaved and filled with the experimental dental materials which were hand-mixed according to the manufacturer’s instructions: Group 1: Mineral Trioxide Aggregate (Pro Root – MTA, Dentsply); Group 2: Calcium Hydroxide (Dycal – Dentsply), and Group 3: Zinc Oxide and Eugenol (ZOE - Dinâmica). The tubes containing the cements were implanted into surgical pockets prepared in the dorsal subcutaneous tissue of rats. Empty polyethylene tubes were used as control group. After 15, 30 and 90 days, the implants were surgically removed, fixed for 48 hours in buffered formalin and processed using routine histologic techniques. Sections of 6 mm were stained with hematoxylin and eosin and evaluated under light microscopy. Results: At short-term evaluation, the connective tissue adjacent to MTA and Dycal exhibited discrete inflammatory reaction associated to thin fibrous capsule. On the other hand, ZOE elicited moderate inflammatory reaction and thicker capsule formation. Connective healing was observed for all experimental groups over time. MTA and Dycal allowed complete healing at the 30-day evaluation while it was observed to ZOE only at 90 days after the implantation procedure. In control group, connective healing related with fibrous capsule was seen at 15-day evaluation. Conclusion: According to the experimental conditions it was concluded that all experimental dental materials are biocompatible. However, ZOE is more irritant to the connective tissue of rats than MTA and Dycal.


1807 (10071)

Human Dental Pulp Reaction to Dentine Bonded Composite Restorations: Histological & Microbial Study. S.S. KHADDOUR*, Damascus University - Faculty of Dental Medicine, Syria

Objective: The aim of this study was to investigate the human pulp reactions to single bond (3M). Methods: 3M single bond was placed in 16 of 32 cavities (2mm deep, 2mm Dm) according to manufacturer's instructions and the cavities were restored with Z100 composite resin. The remaining 16 cavities were capped with a calcium hydroxide formulation (Dycal), and restored with the Z100 composite resin.

All teeth included in this study were extracted for orthodontic purposes.

After extraction at 7 and 30 days, the teeth were fixed, sectioned and stained (H&E) and (gram stain) for Histological & Microbial Study. By using light microscopy.

Results: the table below shows the histological results according to the two kinds of restorations (Dycal-capped teeth, dentin bonded teeth) after 7 and 30 days.

Grope

Time of Extraction

No. of teeth

Odontoblast Vocubularity

The Degree of Inflammatory Reaction

 

Congestion

Fibrosis

1

2a

2c

3

4

1

2

3

Dentin Bonded Teeth

7Days

8

7

3

0

0

0

0

7

5

0

0

30 Days

8

6

4

0

2

0

0

7

7

0

0

Dycal Capped Teeth

7Days

8

6

4

0

0

0

0

5

4

0

0

30 Days

8

1

2

0

0

0

0

2

2

0

0

After 7 days, no significant differences showed between the two groups (P<0.05).

After 30 days, Dycal-capped teeth show less histological changes than Dentin bonded teeth (P>0.05).

The microbial results were negative for both groups of this study.

Conclusions:

The results of this study suggest to use calcium hydroxide as a liner in deep cavities only to limit the non-desirable effects of the dentin bonding agent on the pulp.


1808 (10514)

Pulp Inflammation and Bacterial Microleakage Associated with Various Restorative Materials. P.E. MURRAY*1, A.A. HAFEZ2, L.J. WINDSOR1, and C.F. COX3, 1 Indiana University School of Dentistry, Indianapolis, USA, 2 USC School of Dentistry, LA, CA, USA, 3 UCLA School of Dentistry, CA, USA

Objectives: Many restorative materials are claimed to be successful in preventing bacterial microleakage and minimizing pulp inflammation. However, information regarding the in vivo performance of materials in comparison with each other is limited. The aim of this study was to evaluate and compare the pulp response of nine types of restorative materials when placed in non-exposed non-human primate cavities. Methods: 279 standardized non-exposed Class V cavities, were prepared into buccal dentin. Cavities were restored with: Zinc oxide eugenol (ZnOE), Calcium hydroxide [Ca(OH)2], zinc phosphate (ZP), Resin-modified glass ionomer (RMGI), Composite resin (CR), Bonded amalgam (BA), Gutta-percha (GP), Compomer and Silicate. Pulp tissues were extracted and evaluated for inflammation according to ISO guidelines;—employing histomorphometric analysis and ANOVA (p values) statistics. Bacteria were detected using McKay stains. Results: Pulp inflammation was found to increase with bacterial microleakage around the restoration (p < 0.0001). The frequency of bacterial microleakage was found to vary between restorative materials (p < 0.0001). In rank order of preventing bacterial microleakage from best to the worst; RMGI (100%), BA (88%), ZnOE (86%), CR (80%), GP (64%), Ca(OH)2 (58%), compomer (42%), silicate (36%) and ZP (0%). Conclusions: We conclude that the most effective restorative materials to prevent bacterial microleakage and pulp injury from inflammatory activity were RMGI, BA, ZnOE and CR restorations. Bacterial microleakage and pulp inflammation can be largely avoided, provided the most appropriate restorative materials are used.


1809 (18340)

Effect of self-etching primers on vascular responses in rat carotid artery. Z.C. CEHRELI, M.A. ONUR, F. TASMAN*, A. GUMRUKCUOGLU, and E. ALOGLU, Hacettepe University, Ankara, Turkey

Objectives: To investigate the effect of self-etching bonding systems on pulpal hemorrhage control in direct pulp exposures through contraction of pulp blood vessels using the rat carotid artery model.

Methods: Six dentin bonding agents (Mac Bond, One-Up Bond F, Clearfil SE Bond, FL Bond, Prompt L-Pop and Prime&Bond NT ) were used. The efficacy of bonding agents were compared to that of epinephrine (control) in the viewpoint of the concentration applied and the contraction forces induced on the smooth muscle were recorded using a force displacement transducer. Dose dependent relaxations caused by the test materials were recorded in the same manner in comparison with papaverin. Differences in either contraction or relaxation forces between the bonding agent groups were determined by Friedman and Wilcoxon Signed ranks tests ( p=0.01 ).

Results: FL Bond, SE Bond, One Up Bond, Mac Bond produced dose dependent relaxations. Differences between these materials and papaverin for concentration-dependent relaxations were not statistically significant ( p>0.01 ) Prompt L-Pop and Prime&Bond NT produced epinephrine-like contractions on the rat carotid artery ( smooth muscle ) and the differences between the contraction force of these two adhesives were not significant ( p>0.01) As expected, epinephrine produced concentration-dependent contractions on the carotid artery for each group (P< 0.01).There was also a statistically-significant relationship between each bonding agent and epinephrine for concentration-dependent contractions ( P<0.01 )

Conclusions: For self-etching primers which produce vascular relaxation, hemorrhage control with additional chemicals may be considered if direct pulp capping is to be performed using such adhesive systems.


1810 (16217)

Response of human pulps to dental materials applied in deep cavities. C.A.S. COSTA*1, J. HEBLING1, A.B.L. NASCIMENTO2, H.M. TEIXEIRA2, and E.M.A. GIRO1, 1 Araraquara Dental School - UNESP, Brazil, 2 Pernambuco Dental School - UPE, Recife, Brazil

Objective: Evaluate the response of the pulpo-dentin complex following application of different dental materials in human teeth. Methods: Deep class V cavities were prepared on the buccal surface of 26 sound premolars. In Group 1, the cavity walls (dentin) and enamel were etched with 32% phosphoric acid and the adhesive system One Step (OS- BISCO) was applied. In Groups 2 and 3, before total etching, the cavity floor was lined with the glass-ionomer cement - Vitrebond (VIT- 3M) or the calcium hydroxide cement - Dycal (DY- DENTSPLY), respectively. The cavities were restored with Z-100 resin composite (3M). The teeth extracted between 5 and 30 days were prepared for microscopic examination. Five-micron thick sections were stained with H/E, Masson´s trichrome and Brown & Brenn techniques. Results: In Group 1, the inflammatory response was more evident than in Groups 2 and 3. Diffusion of resin components accross dentinal tubules was observed only in Group 1, in which the intensity of pulp response increased as the remaining dentin thickness decreased. Bacteria were evidenced in the lateral walls of two samples (Group 2) which exhibited no inflammatory response or tissue disorganization. Conclusions: Acid etching followed by application of the adhesive system One Step in very deep class V cavities can not be recommended as adequate procedures. In this clinical condition, the cavity floor should be lined with a biocompatible dental material, such as Vitrebond or Dycal.


1811 (7875)

Pulp Capping with an Experimental Hemostatic Agent and Calcium Hydroxide. C. PAMEIJER*, University of Connecticut SDM, Simsbury, USA, and G. NORVAL, University of Stellenbosch, School of Dentistry, Tygerberg, South Africa

Complete control over hemostasis is considered to be a critical factor in obtaining predictable favorable results in pulp capping procedures. Saline, 2% chlorhexidine and various concentrations of sodium hypochloride have been reported in the literature as being suitable. Objective:It was the objective of this experiment to determine the efficacy of an experimental hemostatic solution in pulp capping procedures. Methods:84 Cl V preparations were made in six primates divided over 4 groups. After exposure of the pulp, this non-epinephrine experimental solution was applied using a sterile cotton pellet and left in place for + 5 minutes. Two groups had Consepsis, a disinfecting solution, applied for 60s. A small amount of calcium hydroxide (Ultrablend Plus) was placed over the exposures. After light curing the cavities were restored using an acid etch/bonding agent/resin composite technique. Animals were euthanized with an overdose of ketamine and the jaws fixed in 10% neutral buffered formalin. All teeth were processed for routine histological evaluation. Three time periods were evaluated. Results: After 5 days the pulps were remarkable for minor inflammation (0.5-1.33 degrees). After 25 days only one group scored 0.18 degrees, after 75 days no inflammation was seen. All specimens after 25 and 75 days (a total of 27) were vital and had a bridge, with a quality ranging from 1.71-2.6 degrees (on a scale of 1-3). Conclusions: the experimental solution was a successful hemostatic agent, establishing a controlled environment, which allowed for the application of a light cured calcium hydroxide, resulting in predictable bridge formation. Disinfecting with 2% chlorhexidine is recommended. (Supported by Ultradent Products Inc). phpameijer@home.com


1812 (10511)

Pulp Capping and Repair Activities Responsible for Dentin Bridge Formation. A.A. HAFEZ*1, P.E. MURRAY2, L.J. WINDSOR2, T. DONOVAN1, and C.F. COX3, 1 USC School of Dentistry, LA, CA, USA, 2 Indiana University School of Dentistry, Indianapolis, USA, 3 UCLA School of Dentistry, CA, USA

Objectives: The importance of pulp capping variables which mediate pulp repair activities and dentin bridge formation following pulp exposure are not well understood. Consequently, the aim of this study was to evaluate the effects of pulp capping variables on dentin bridge formation. Methods: Calcium hydroxide [Ca(OH)2], resin modified glass ionomer (RMGI) and resin composite (RC) were used to restore pulp exposures prepared in 161 nonhuman primate teeth, according to ISO usage guidelines. Teeth were collected between 7 and 720 days to observe the pulp repair activities leading to dentin bridge formation. The dimensions of pulp exposures and dentin bridges were measured histomorphometrically using a grid eyepiece graticule under light microscopy. The presence of operative debris and tunnel defects were noted. Bacteria were detected using McKays stain. Pulp inflammatory activity were categorized according to ISO standards. Analysis of variance (ANOVA p values) statistics were used to correlate pulp capping variables with dentin bridge area. Results: The pulp capping variables in order of their relationship to dentin bridge area, from the most important to the least important were; pulp capping materials (p=0.0252), bacterial microleakage (p=0.0358) and area of operative debris in the dentin bridge (0.0362). A further 10 pulp capping variables were found to be less important (p values > 0.05). Bacteria contaminated 18.6% of RC, 22.2% of RMGI and 46.97% of Ca(OH)2 capped pulps, this caused pulpal inflammation and impaired dentin bridge formation. Operative debris increased the incidence of tunnel defects (p=0.0008) which disrupted dentin bridge formation. Conclusions: We conclude that to achieve ideal dentin bridge formation, attention should focus on avoiding the infiltration of operative debris into pulp tissue, to prevent the development of tunnel defects and complications. Most important is the placement of pulp capping materials which prevent bacterial microleakage.


1814 (16402)

Dog's pulp histological evaluation after pulpotomies whith cyanoacrylate and calcium hydroxide. D.S. ALBUQUERQUE, and L.F. GOMINHO*, Faculdade de Odontologia de Pernambuco, Recife, Brazil

Objective: to evaluate histological aspects of dog´s pulp-dentin complex when covered right after pulpotomies using ethyl-cyanoacrylate (Super Bonder) and calcium hydroxide. Methods: 24 teeth were divided into 2 groups of 12. Group 1 was categorized as the test group (ethyl-cyanoacrylate) and group 2 as the control group (calcium hydroxide). The teeth involved in the study were the second and third incisors, canines, second and third premolars. The pulpotomies were done in one appointment and the histological evaluation after 30 days. Results: In group 1, 83,3% and in group 2, 100% presented a hard tissue barrier (P=0,478). A continuous hard tissue barrier was observed in 60% of ethyl-cyanoacrylate group and 75% of calcium hydroxide group (P=0,652). The pulpar aspect of both groups showed 100% of moderate chronic inflamatory process. The groups were compared statistically using the Fisher Exact Test. Conclusion: the presence of hard tissue barrier in the control group was higher than in the test group, but this difference was not significant; the difference observed between the histological structure of barrier, continuous or non-continuous, were similar when compared between groups. A moderate chronic inflamatory process was found in all teeth, which were treated within 30 days.


1815 (18129)

Clinical evaluation of White Pro Root MTA as a direct pulp capping material. E.I. ADACHI*1, C.E. IWAMOTO1, D.M. BARNES1, C.H. PAMEIJER2, E.E. ROMBERG1, D.L. GEORGE1, and J.C. GINGELL1, 1 University of Maryland, Baltimore College of Dental Surgery, USA, 2 University of Connecticut SDM, Simsbury, USA

Objective: this study evaluates the clinical and radiographic findings of White Pro Root MTA (Tulsa Dental) as a direct pulp-capping material compared to a control, Dycal (L.D. Caulk). Methods: forty-eight human 3rd molars, caries free or with incipient decay, scheduled to be extracted were selected and randomly divided in 2 groups: Group A: (n=24) White Pro Root MTA and Group B: (n=24) Dycal. Teeth were isolated with rubber dam and Class I cavities prepared. Mechanical pulp exposure was performed using a sterile diamond bur and a sterile cotton pellet damped with saline solution was placed for 20 to 50s. The exposure was then lightly rinsed with sterile water and gently air-dried. White Pro Root MTA or Dycal was placed over the exposure site followed by a layer of light cured Dyract Flow (L.D. Caulk). Teeth were acid etched and Prime and Bond NT adhesive (L.D. Caulk) was applied and light cured. TPH composite resin (L.D. Caulk) was placed and light cured. Evaluations were performed by phone at 7 days and clinically at 30 and 120 days using standard tests and radiographs. Teeth were extracted at 120 days and fixed in formalin. Results: no significant difference was found for 7-day sensitivity between White Pro Root MTA and Dycal (p>0.05, using Mann-Whitney U test). Clinically, no significant difference was found for pulp response at 30 days (p>0.05, using a Chi-Square test) and at 120 days (p>0.05, using Fisher’s exact test) between White Pro Root MTA and Dycal. Radiographically, there was no difference at 120 days. No statistical test needed to be performed since no teeth in either group exhibited periapical lesions. Histological results are pending. Conclusion: this study has demonstrated that clinically White Pro Root MTA has the potential to be as effective pulp capping material as the control. This study was supported by Tulsa Dental, Dentsply.


1817 (15461)

Biocompatibility of Hg/amalgam Alloy in Exposed Dental Pulps. C.F. COX*1, P.E. MURRAY2, A.A. HAFEZ3, B. TARIM4, and H. KOPEL1, 1 UCLA School of Dentistry, CA, USA, 2 Indiana University School of Dentistry, Indianapolis, USA, 3 USC School of Dentistry, LA, CA, USA, 4 University of Istanbul School of Dentistry, Turkey

Objectives: Many restorative materials are known to be biologically compatible with exposed dental pulps, although the stimulation of pulpal healing and dentin bridge formation have sometimes been claimed to be attributable to calcium hydroxide[Ca(OH)2]. The purpose of this study was to compare the sequence of pulpal healing and dentin bridge formation subjacent to exposed pulps when capped with a Mercury containing, high-copper amalgam alloy Dispersalloy (Hg/amalgam) and compare these responses with hard set Ca(OH)2. Methods: Class·V cavities (n=84) were placed throughout the teeth of six rhesus monkeys. Mechanical exposures (n=26) were capped with Hg/amalgam with biological sealing using Intermediate Restoration Material (IRM). Some other unsealed mechanical exposures were capped with Hg/amalgam (n=25). For comparison, the remainder of the cavities (n=33) were pulp capped with Ca(OH)2. Pulp tissues were histologically evaluated for healing using ISO criteria for inflammation, necrosis and soft-tissue organization, as well as odontoblastoid migration and dentin bridge secretion at intervals of 3, 5, 7 10, 14, 21 and 35 days. Bacteria were detected using McKay stains. Results: Little difference was observed in the sequence of pulpal healing and odontoblastoid migration and dentin bridge secretion between pulps capped with Ca(OH)2 and biologically sealed Hg/amalgam. Whereas the pulps capped with Hg/amalgam without a biological seal were associated with delayed and inferior pulp healing, showing inflammation and necrosis. Although odontoblastoid migration was observed, no dentin bridges were secreted beneath unsealed Hg/amalgam capped pulps. Conclusions: We conclude that Hg/amalgam is not toxic to direct capped pulps. However, Hg/amalgam does not provide an environment to promote dentin bridge formation in the presence of bacterial microleakage.


1818 (17403)

The efficacy of calcium hydroxide for induced secondary dentin formation as a prophylaxis treatment for dens evaginatus. M. SOOKASAM*, S. WANACHANTARARAK, and A. BOONDEJ, Chiang Mai University, Thailand

An occlusal tubercle fracture or attrition in dens evaginatus could be resulted in a pulpal disease. For the prophylactic treatment, a calcium hydroxide was used as a direct or an indirect pulp capping in order to stimulate secondary dentin formation. But some evidences suggested that it could also produce a small abscess in the pulp due to its alkaline properties, which may interfere a secondary dentin formation. Objectives: This study was to investigate the efficacy of calcium hydroxide on an indirect pulp capping and the rate of secondary dentin formation in dens evaginatus in vivo. Methods: Seven affected premolars, subjected to extract for an orthodontic reason, were used in this experiment. In each tooth, the tubercle was removed and the cavity, class I around 1.5mm deep, was prepared at the same area. The base of cavity was filled with a thin layer of calcium hydroxide (dycal®) and the rest was filled with an amalgam. The teeth were left in the mouth for 3 and 6 months. The ground section was prepared through the middle of the tooth with thickness of approximately 100-micron. The specimens were dehydrated in ethanol and then cleared by immerged in methyl salicylate overnight. The thickness of secondary dentine was examined and measured under a light microscope. Results: All teeth were reported no clinical sign of pulpitis or any periapical lesion at the day of extraction. Both groups showed substantially increased in the thickness of a secondary dentin. The mean value of 3 month group was 0.39mm (S.D. 0.11, n=4) and for 6 months group was 0.67mm (S.D. 0.21, n=3). Conclusion: The calcium hydroxide can be used for induced a secondary dentin formation in the prophylactic treatment of dens evaginatus.


1819 (16945)

The Effects of a Denture Adhesive on Masticatory Function. T. FUJIMORI*, S. HIRANO, and I. HAYAKAWA, Tokyo Medical and Dental University, Japan

Objectives:The objective of this study was to examine whether a denture adhesive is useful for the improvement of masticatory function.Methods:Sixteen edentulous subjects wearing well-fitting complete dentures volunteered to participate in this study. According to Kapur's classification for the adequacy of denture-bearing tissues, eight subject were categorized into "poor" group and the others into "fair or good" group. All the subjects were instructed to apply a denture adhesive (Correct , Shionogi, Osaka) onto maxillary and mandibular dentures according to manufacturer's direction. Masticatory performance was measured using the sieving method with peanuts. Maximum biting forces were recorded with maximal voluntary clench using a hand-held occlusal force meter (Model GM10, Nagano, Tokyo) unilaterally and bilaterally in the molar region. During the two-week test period, subjects wore dentures with a denture adhesive for half period and without it for another half. This order was randomly assigned. Experiments were carried out at the end of each half period.Whether the use of a denture adhesive and the adequacy of denture-bearing tissues influenced on masticatory performances and maximum biting force were tested using repeated measured two-way ANOVA. In addition, the improvements of masticatory for both groups were compared using t-test.Results:Both the use of a denture adhesive and the adequacy of denture-bearing tissues showed significant positive effects for all variables (p<0.05). The improvement of masticatory function by using denture adhesive was greater for subjects with poor denture-bearing tissues than with good or fair (p<0.05).Conclusions:It was concluded that the use of a denture adhesive showed the positive effect for masticatory function of complete denture wearers.


1820 (17772)

Clinical Evaluation of Compliance of Resilient Denture Liners. A. VILLAR*1, I.J. PESUN1, J. HODGES1, M.E. BROSKY1, L. ISON1, C. DOYEN1, R. DELONG1, J. LAI2, and D. SCHNEIDER2, 1 University of Minnesota, Minniapolis, USA, 2 Lai Laboraotries, Burnsville, MN, USA

Objective:A non-destructive "compliance" test has been developed at the MDRCBB that allows for clinical evaluation of resilient denture liners. Methods:A crossover study with 20 patients had two dentures fabricated with long-term, silicone-based resilient liners, one Molloplast-B (Buffalo Dental Manufacturing Co., Syosset, N.Y.) and the other MPDS-SL (Lai Laboratories, Inc., Burnsville, MN). Each denture was worn for six months with one patient lost to follow-up. The two materials were assessed for compliance before the patient wore the dentures then after three and six months of wear. Compliance was determined by applying a 3 lb. force following a squarewave pattern on to the surface of the material using the MDRCBB MTS closed-loop servohydraulic testing system (MTS Systems, Eden Prairie, MN). The force and position values were recorded using a Nicolet 310 Storage Oscilloscope (Nicolet Instrument Corporation, Madison, WI). The compliance was determined at three locations on each denture from the oscilloscope and analyzed using DASH 300 (data acquisition) software. Results:Compliance increased from baseline to 3 months and from 3 months to the 6 month for almost all location on both materials. Molloplast-B and MPDS-SL differed in average change in compliance (p=0.007). Average change in compliance from baseline for Molloplast-B was 350 (SE 22) and 255 (SE 22) for MPDS-SL. There was a trend towards a larger difference at 6 months than at 3 months but not significantly (p=0.13). Conclusion:Overall, MPDS-SL did not change in compliance as much as Molloplast-B did over the 6 months of this study.


1821 (20366)

Patient Satisfaction with Two Resilient Denture Liners. C.D. FINES*1, I.J. PESUN1, J.S. HODGES1, L. ISON1, C. DOYEN1, M.E. BROSKY1, J. LAI2, and D. SCHNEIDER2, 1 University of Minnesota, Minneapolis, USA, 2 Lai Laboraotries, Burnsville, MN, USA

Objective: Pain and discomfort are common complaints of patients with mandibular complete dentures. This can be a result of a thin mucosa or severe alveolar ridge resorption. Resilient denture liners are prescribed for these patients who cannot adjust to hard denture bases. Methods: In this study, each of the 20 patients had two dentures fabricated with long-term, silicone-based resilient liners, one with Molloplast-B (Buffalo Dental Manufacturing Co., Syosset, N.Y.) and the other with MPDS-SL (Lai Laboratories, Inc., Burnsville, MN). Each denture was worn for six months. A satisfaction survey was completed after three months and again after six months. Comfort, appearance, ease of care, taste, smell, and the patients’ overall satisfaction were measured on a visual analog scale (VAS). Daily diaries were completed between appointments to determine specific cleansers used and how much time the dentures were worn in between appointments. Results: One patient was lost to recall. Patients’ overall satisfaction was the same for both materials (p=0.89). Patients varied in overall satisfaction, ranging from 43-100 on a scale of 1 (unsatisfactory) to 100 (Highly satisfactory) (p=0.045). The highest and only significant correlation between wear time and satisfaction was the more a patient wore the dentures, the greater their reported comfort with the dentures. (p=0.01, MPDS-SL r=0.42, Molloplast-B r=0.44). Patients did not use different cleansing method for the two materials (p>0.08 for all methods). Most patients used only one cleanser most of the time. Conclusion: Patients have a wide range of satisfaction when wearing dentures, but are consistent in the way they maintain their dentures.


1822 (19143)

Clinical Evaluation of Color of Resilient Denture Liners. A. VILLAR1, I.J. PESUN*1, J.S. HODGES1, M.E. BROSKY1, L. ISON1, C. DOYEN1, C.-C. KO1, J. LAI2, and D. SCHNEIDER2, 1 University of Minnesota, Minniapolis, USA, 2 Lai Laboraotries, Burnsville, MN, USA

Objective: Resilient denture materials are used for patients who cannot adjust to hard-based dentures due to thin mucosa or severe alveolar ridge resorption. Resilient denture liners are known to change color over time; patients can see color change and may assume that the material is degrading. Methods: Thus, color testing was undertaken for clinical evaluation of resilient denture liners. In this crossover study, each of 20 patients had two dentures fabricated with long-term, silicone-based resilient liners, one with Molloplast-B (Buffalo Dental Manufacturing Co., Syosset, N.Y.) and the other with MPDS-SL (Lai Laboratories, Inc., Burnsville, MN). Each denture was worn for six months, with one patient lost to followup. The two materials were assessed for color before the patient wore the dentures, after three months of wear and after six months of wear. Images of the dentures were captured using an Olympus SZH10 zoom stereo microscope with a charge coupled video camera and Optimas image analysis software. RGB and L*a*b* were calculated using Photoshop (Adobe Systems Inc., CA). The color was determined at three locations on each denture. Results: For both materials: color changed significantly from baseline to 3 months and from baseline to 6 months (p<0.01). MPDS-SL changed significantly less than Molloplast-B from baseline to 6 months for R (p=0.039), G (p=0.0367), B (p=0.005) and L* (p=0.042). Conclusion: MPDS-SL had less color change over 6 months than did the Molloplast-B.


1823 (17977)

Surface Irregularity and Sealant Effect on Denture Liner Fungal Growth. C.A. LEFEBVRE*, and G.S. SCHUSTER, Medical College of Georgia, Augusta, USA

Contamination of removable prostheses with microorganisms, particularly C. albicans is a common clinical problem. Surface irregularity is believed to be contributory. Sealants have been developed to control surface contamination. Purpose: To determine the effect of surface irregularity and sealant use on colonization of a denture liner (PermaSoft, Autenal, Inc.) with C. albicans. Methods: Specimen disks (5 mm x 1 mm) were fabricated aseptically (n=12) against Mylar and 60-grit sandpaper to produce a smooth or irregular surface respectively. Six disks of each surface treatment were coated with PermaSoft sealant. Disks were placed in Transwellâ dishes and covered with Sabouraud’s broth containing an ATCC strain of C. albicans and incubated at 37° for 5 days. Wells containing Teflon disks or broth alone served as controls. The disks were rinsed to remove unattached C. albicans and then sonicated in sterile water to remove surface organisms. Serial dilutions of the sonicates were plated on Sabouraud’s agar and returned to the incubator for 24 h. Colonies were counted with a Brunswick Colony Counter. The results were compared with ANOVA and Tukey intervals (a=0.05). Results: The mean number of colonies formed was 10.3± 8.4, 16.3± 14.4, 10.7± 12.9 and 10.8± 9.1 for the smooth specimens without sealant, smooth specimens with sealant, irregular specimens without sealant and irregular specimens with sealant groups respectively. There was no statistically significant difference between specimens with a smooth or irregular surface or those treated with a sealant and without. Conclusions: C. albicans is able to adhere to the surface of PermaSoftâ denture lining material regardless of surface texture or use of sealant. This research was supported by the MCG Biocompatibility Program.


1824 (18127)

Speciation of Candida from two resilient soft denture liners. M.E. BROSKY1, B. MORRISON*1, I.J. PESUN1, J. HODGES1, W. LILJEMARK1, L. ISON1, C. DOYEN1, J. LAI2, and D. SCHNEIDER2, 1 University of Minnesota, Minneapolis, USA, 2 Lai Laboraotries, Burnsville, MN, USA

Objectives: To differentiate Candida species grown on two soft denture liners. Methods: Twenty patients had two dentures fabricated with long-term, silicone-based resilient liners, one with Molloplast-B (Buffalo Dental Manufacturing Co., Syosset, N.Y.) and the other with MPDS-SL (Lai Laboratories, Inc., Burnsville, MN). Of the twenty patients enrolled one was lost to follow-up. Each mandibular denture was worn for six months. After six months a 5.0 mm circular soft-liner sample was taken from the tissue surface of the lingual flange of each denture. Samples were processed and Candida species isolated using standard techniques. Speciation of Candida was preformed using CHROMagar (Becton Dickinson, USA) and API 20C AUX strips (BioMerieux, France). Candida colonies from each denture were streaked on CHROMagar and incubated for 48h at 370C. The colonies were then speciated by color and morphology using identification tables provided. Confirmation of these Candida species was obtained by inoculating a colony on an API 20C AUX strip and incubating for 24-72h at 30° C. Results were compared to the identification table provided. Results: Of Molloplast-B’s 19 samples, 7 had no growth, 4 were positive for C. albicans, 3 for C. parapsilosis, 2 for C. glabrata, 1 for C. tropicalis, 2 for Trichosporon spp., and 2 had non-identifiable colonies. The analogous counts for the MPDS-SL were: 10, 4, 1, 3, 0, 1, 1. Of the 7 subjects for whom the dentures were not both positive or both negative, 5 were positive for Molloplast-B but not MPDS-SL, while the other 2 were positive for MPDS-SL but not Moloplast-B (p=0.45, Exact McNemar test). Conclusion: Several yeast species were cultured from each material. Molloplast-B tended to be culture-positive more often than MPDS-SL, but not significantly different.


1825 (18240)

Quantitative analysis of Candida isolated from two soft denture liners. M.E. BROSKY*1, I.J. PESUN1, J. HODGES1, W. LILJEMARK1, L. ISON1, C. DOYEN1, J. LAI2, and D. SCHNEIDER2, 1 University of Minnesota, Minneapolis, USA, 2 Lai Laboraotries, Burnsville, MN, USA

Objectives: Candida colonization of two soft denture liners. Methods: Twenty patients had two dentures fabricated with long-term, silicone-based resilient liners, one with Molloplast-B (Buffalo Dental Manufacturing Co., Syosset, N.Y.) and the other with MPDS-SL (Lai Laboratories, Inc., Burnsville, MN). Of the twenty patients enrolled one was lost to follow-up. Each mandibular denture was worn for six months. After six months a 5 mm circular soft-liner sample was taken from the tissue surface of the lingual flange of each denture. Samples were placed in sterile Todd-Hewitt broth, sonicated and serial dilutions were made. Samples of 1 ml were plated on Tryptocase-soy agar with streptomycin and vancomycin for isolation of Candida. After 48 hours of incubation at 37° C the plates were visually inspected and Candida identified as lusterless and creamy, whitish-pink or pink colonies. Candida colonies were quantified using a Quebec colony counter as colony forming unit per ml. Results: In a paired t-test on log (count+1) Molloplast-B had, on average, about 5 times as many CFU/ml as MPDSL-SL, but this was not significant (p=0.26). A sign test gave a similar non-significant trend (p=0.057). Conclusion: Candida growth on Molloplast-B was greater than on MPDS-SL but not significantly greater.


1826 (15057)

Sorption and Solubility of Surface-sealed Tissue Conditioner. F. KAWANO*, T. OHGRI, K. OKA, T. ICHIKAWA, and O. ISHIDA, The University of Tokushima, Japan

Objectives: Stability of a tissue conditioner depends on the sorption/solubility of the materials considerably. Because sorption and solubility are accompanied by a volumetric change, hardening and color change, it is a physical property of importance. The purpose of this study was to determine the sorption/solubility of 3 tissue conditioners (Co-Comfort, Soft Liner and Tissue Conditioner) with and without 2 different surface treatments. (AB Coat (silicone type) and Top Coat (polymethyl methacrylate type). Methods: The sorption/solubility test was performed as outlined in ADA Specification #12 for denture base polymers. Seven specimens of each material with and without surface treatments were tested and data collected at 1 week, 2 weeks and 1 month. Results: Sorption data varied from 1.3 to 2.9 mg/cm2 at 1wk; -3.4 to 2.3 mg/cm2 at 2 wk; -7.3 to 3.3 mg/cm2 at 1 month. Solubility data of tissue conditioner without surface treatment varied from -0.1 to 6.1 mg/cm2 at 1wk; -0.3 to 10.7 mg/cm2 at 2 wk; -0.7 to 15.7 mg/cm2 at 1 month. A statistic analysis of the data using ANOVA showed significant differences among materials, and among surface treatments at all time intervals. Conclusions: It is concluded that the surface treatment of the tissue conditioners can decrease the water uptake, but it can not prevent the solubility of the tissue conditioner. The results of this study have clinical implications since the sorption and solubility may affect the life expectancy of the tissue conditioner.


1827 (18552)

Shear bond strengths of soft-lining silicones in dry versus wet polymerization. P.G. NICOLAU*1, J. RAMOS2, and S. FANGAIA1, 1 University of Coimbra, Figueira da Foz, Portugal, 2 Coimbra University, Portugal

Adhesion failures of direct soft-lining silicones to the denture base material are most common. There are some concerns if water sorption from the wet surrounding oral tissues during polymerization can influence the adhesion of these materials to the denture base. Objectives: the purpose of this study was to compare the Shear bond Strengths(SBS) of five direct soft-lining silicones (SLS) to a denture base material in a dry versus a wet surrounding surface. The SLS studied were GC Reline Soft (GRS)- GC, Tokyama Sof Relining (TSR)- Tokuyama, Ufi Gel C (UFG)- Voco, Mucopren Soft (MUS)- Kettenbach, Mollosil plus (MLP)-Dentax. Materials and Methods:one hundred cylinder (4.5x5mm) shaped samples of Lucitone 199 (L199) -Dentsply/Detrey base material were made and randomly assigned for each group of SLS tested. The surface treatment of L199 was done uniformly by using - 240 grit silicone-carbide paper and by sandblasting for 5 s. Each group was then divided in two sub-groups (n=10), to be surface treated and bonded to the SLS in a dry or wet surrounding surface, during polymerization. All the materials were applied per manufacturers` directions. After relining, the specimens were stored in a dry place at room temperature for 24 hours and then SBS´s were measured with an Instron Testing Machine with a crosshead speed of 0.5 cm/min. Data were recorded in Newton(N) and analyzed using ANOVA and Student`s t- test (p* 0.05). Results: of average values and (SD) among the groups in a dry surrounding surface: GRS(39.5±8,6), TSR(9.0±2.6), UFG( 17.2±7,0), MUS(32.3±4.7), MLP(15.1±4.3); and in a wet surrounding surface: GRS(32.5±6.9), TSR(11.2±1.9), UFG( 19.6±5.8), MUS(32.0±6.0), MLP(17.5±4.4). Conclusions:GRS had statistically higher SBS´s in a dry then in a wet surrounding surface(p* 0.05). All the other groups had statistically similar SBS´s in a dry or wet surrounding surface. Results suggest that a wet surrounding surface does not significantly influence the SBS´s of SLS.


1828 (20912)

In-vitro comparison of the tensile bond strength of four denture adhesives. D. HALL*, C.A. MUNOZ, and A. ESPINOSA, Loma Linda University, CA, USA

Objective: The use of denture adhesives has become an acceptable treatment adjunct in complete denture therapy. Improved denture function and comfort are the benefits of the use of these products. This study evaluated the tensile bond strength of three cream denture adhesives SuperPoligrip (Block Drug), Effergrip (Warner Lambert) and Fixodent (P&G) and one wafer denture adhesive Sea-Bond (Combe ) 5 minutes after application of the adhesive, one hour, three hours, and eight hours. Methods: 2.5 cm cylinders were made of a heat polymerized denture base resin and polished to a high luster. 1.5 grams of denture adhesive or a 2.5cm wafer were sandwiched in between the two denture resin cylinders. One side of the denture cylinder was coated with a thin layer of artificial saliva and the other side was left dry. A 1.5 Kg force was applied for ten minutes and then the cylinders were placed in a humidifier at 370C for either 3,8 or 10 hours. Using an Instron testing machine the specimens were debonded in a tensile mode at a rate of 10 mm per minute. The maximum force before failure was calculated in MPa. ANOVA was used to determine if differences existed between the different time periods or materials. Results: Over the four time periods, SuperPoligrip and Effergrip had the highest tensile bond strength (range of 0.80 to 2.26 MPa) and were not statistically different. Fixodent had a tensile bond strength of 0.32 to 2.02 MPa while Seabond had the lowest bond strength overall. Conclusions: (1) SuperPoligrip can be confidently prescribed for those individuals desiring a denture adhesive with the most holding power over an extended period of time. (2) The denture wafer ( Sea-Bond) evaluated in this study had the lowest tensile bond strength.


1829 (21423)

Finite element analysis:Load to fracture of the Procera® all-ceramic bridge. B.R. LANG*1, R.-F. WANG1, and M. VASILIC2, 1 University of Michigan, Ann Arbor, USA, 2 Nobel Biocare, Yorba Linda, CA, USA

Objectives: To measure the load to fracture of a 3-unit Procera® bridge as influenced by 1) the joint between the 3 ceramic units, and 2) various luting agents used to cement the bridge.

Methods: Five bridges were constructed by the CAD/CAM method and cemented on dies with Fuji Plus for mechanical strength testing using the Instron machine. The all-ceramic bridge was also modeled for finite element analysis.

Results: From the FEA, cement failure occurred before joint failure with Zinc Phosphate (422 N). The joint failed at approximately the same load and before the cement for Fuji Plus (690 N) and Panavia 21 (688 N). In the mechanical test failure occurred at 697 ± 102 N (Fuji Plus).

Conclusions: FEA bridge failure was initiated at the lower joint border and progressed upward through the aluminum oxide material on the pontic side of the joint when cemented with Fuji Plus and Panavia 21. The mechanical tests with Fuji Plus demonstrated a similar mode of fracture. In Zinc Phosphate FEA, the cement failed initially followed by bridge failure at the bottom joint area and progressed upward through the aluminum oxide on coping side of the joint. Supported by Nobel Biocare/University of Michigan Center for Excellence.


1830 (21158)

Comparison of compressive strength: Zirconium vs. aluminum oxide copings. M.D. SNYDER*, and M.E. RAZZOOG, University of Michigan, School of Dentistry, Ann Arbor, USA

Objective: The purpose of this study was to investigate the ultimate compressive strength of the new experimental Procera® sintered Zirconia Y-TZP copings using Procera® Aluminum Oxide copings as a control. Method: In order to investigate this theory, we compared the ultimate compressive strength of Procera® sintered Zirconia Y-TZP copings to the ultimate compressive strength of Procera® Aluminum Oxide copings. The study consisted of four groups, two contained six samples and two contained five samples. Two luting agents were selected for the study. Results: Group A was Aluminum Oxide copings luted with 3M Vitremer cement. Group B was Aluminum Oxide copings luted with G.C. Fuji Plus cement. Group C was Zirconium copings luted with 3M Vitremer cement. Group D was Zirconium copings luted with G.C Fuji Plus cement. All copings were luted to standardized, grade 2, pre-milled titanium dies and stored in 100% humidity for 10 weeks. All samples were inspected prior to testing and found to be free of any detectable fractures. The samples were then loaded to fracture at the rate of 0.5mm/min. using a universal-testing machine providing the following results. Group A=78.99 +23.32Kg (S.D.), Group B=105.70 +21.01Kg (S.D.), Group C=89.97 +34.92Kg (S.D.), Group D=111.26 +13.38Kg (S.D.). The Fisher’s PLSD test was applied to the data and indicated that there was no statistical difference between the two Zirconium groups compared to the two Aluminum Oxide groups (P .6066). Conclusion: It was concluded that under the conditions of this study, the ultimate compressive strength of the experimental Procera® sintered Zirconia Y-TZP copings was not significantly different from that of the Procera® Aluminum Oxide copings. Supported by University of Michigan Nobel Biocare Center for Excellence.


1831 (8164)

Microleakage of Procera AllCeram Crowns with Different Types of Cements. F. ALBERT*, O. EL-MOWAFY, G. ZARB, and P. WATSON, University of Toronto, Canada

Objectives, this study investigated effect of different cements on microleakage of Procera AllCeram Crowns (PAC). Methods, 80 extracted molars were divided into 2 equal groups. Teeth in one group were prepared to receive PAC while teeth in the other received porcelain-fused-to-metal (PFM) crown preparations (control). PAC and PFM copings were made following standard techniques. Each group of prepared teeth was subdivided into 4 equal groups (n=10). PAC subgroups of copings were each cemented with one of 4 cements: Fleck’s (Mizzy), Fuji 1 (GC), Rely-X (3M), C&B Metabond (Parkell). PFM copings were similarly cemented. Following 24h of water storage at 37 oC specimens were subjected to thermocycling between 5 and 55 oC for a total of 500 cycles. Specimens were then sealed for microleakage and immersed in 5% basic red fuschin dye solution for 24h. Specimens were then sectioned and their images captured with and intraoral video camera. Microleakage scores were recorded from photos of sections according to a 5-point scale. Data were analyzed statistically with Chi-square. Results, a significant association was found between cement type and degree of microleakage (p < 0.001). With Fleck’s 76% of PAC copings had highest scores of microleakage while 90% of PFM copings had the same. With C&B Metabond, 34% of PAC copings had zero microleakage scores while 96% of PFM copings had the same. With Fuji I, 49% of PAC copings and 66% of PFM copings had zero microleakage scores, while with Rely-X, 10% of PAC copings and 84% of PFM copings had zero microleakage scores. Conclusions, it is concluded that use of C&B Metabond resulted in highest percentage of zero microleakage scores while use of Fleck’s resulted in highest percentage of most microleakage scores. Supported in part by Nobel Biocare.


1832 (16652)

Marginal Accuracy of CAD/CAM Composite Crown. K. HIKITA*1, T. MAIDA1, K. KOBAYASHI2, and T. YORIMOTO2, 1 Health Sciences University of Hokkaido, Sapporo, Japan, 2 Hokkaido University, Sapporo, Japan

Objectives: Recently, some dental CAD/CAM systems were used in multiple clinical trials. The purpose of this study was to evaluate the marginal fit improvement of composite crowns that were fabricated by the dental CAD/CAM system GN-I (GC, JAPAN). Methods: First, 10 abutment plaster models were made, they were then automatically measured by a spot laser. The measurement data was sent to the CAD computer. With the data, a crown was designed by the GN-I CAD software. The GN-I CAD system design margin line automatically or manually. And this margin lines were not adjusted manually. Composite blocks were then finely milled into crowns by GN-I CAM machine. Composite crowns without any adjustment were cemented to each abutment tooth model . They were sectioned into eight blocks. Marginal cement thickness of 16 sections was measured with a microscope. Results: As a result, the mean of cement thickness was 44.8 (18.9) micro meter. Conclusions: This result indicated that the composite crown fabricated by the GN-I and the conventional cast crown were of the same level in crown margin accuracy.


1833 (17891)

Effectiveness of the electrical discharge machining on marginal fit of cast commercially pure titanium and Ti-6Al-4V crowns. G.E.P. HENRIQUES*, M.F. MESQUITA, M.A.A. NÓBILO, and E.F.R. CONTRERAS, Campinas State University, Piracicaba-SP, Brazil

Titanium has been suggested as a replacement for alloys currently used in fixed partial denture. However, difficulties in casting have resulted in incomplete margins and discrepancies in marginal fit. Objectives: This study evaluated and compared the marginal fit of crowns fabricated from commercially pure titanium (cp Ti) and Ti-6Al-4V with crowns fabricated from palladium-silver (Pd-Ag; control) before and after marginal refinement by electrical discharge machining (EDM). Methods: Forty-five bovine teeth were prepared to receive full cast crowns. Stone and copper-plated dies were obtained from impressions. Fifteen crowns were cast with each casting material (cp Ti, Ti-6Al-4V and Pd-Ag). Marginal fit measurements, in mm, were recorded at 4 reference points on each casting with a traveling microscope. Marginal refinement with EDM was conducted on titanium-based crowns, and measurements were repeated. Data were analyzed by two statistical procedures (Kruskal-Wallis test and t-Student test) at a 1% probability level. Results: The Kruskal-Wallis test showed significant differences among mean values (in micrometers) of the as-cast cp Ti crowns (83.9; SD 26.1) and the other groups: Ti-6Al-4V (50.8; SD 17.2) and Pd-Ag (45.2; SD 10.4). After EDM marginal refinement, significant differences were detected among Ti-6Al-4V crowns (24.5; SD 10.9) and the other groups: cp Ti (50.6; SD 20.0) and Pd-Ag (not submitted to EDM). The t-Student test indicated that marginal refinement with EDM effectively improved the fit of cp Ti (83.9 to 50.6) and Ti-6Al-4V (50.8 to 24.5) crowns. Conclusion: Despite the superior statistical results of Ti-6Al-4V, all titanium-based crowns had clinically acceptable marginal fits compared to the Pd-Ag crowns. After EDM marginal refinement, the fit of cast cp Ti and Ti-6Al-4V crowns improved significantly.


1834 (18512)

Evaluation of marginal fit with different metal free crown systems. S. PAMUK*, A. ÇÝNAR, and M. BALKAYA, Unýversity of Istanbul Faculty of Dentistry, Turkey

 

 

Esthetics and biological needs increased the use of metal free, reinforced all ceramic systems. In addition to reinforced ceramic, a ceromer material Targis Vectris, is developed to satisfy patients demand.

Objectives: Purpose of this study is to determine the marginal deformation of five different systems at various fabrication stages.

Material and Methods: A total of 50 metal free crowns were fabricated. They were divided into 5 groups of 10 crowns each (In-ceram (Vita), IPS Empress (Ivoclar), Celay Alumina (Microna AG), Celay Feldspat (Microna AG), Targis Vectris (Ivoclar)); Rounded angle shoulder type of finish line was used for the crown preparations. Dimensional changes were measured around the crown in 18 points in horizontal and vertical plane at various preparation stages with a profile projector (SPS 200 U, SOMET). Results were analyzed first with Friedman’s test then with Mann-Whitney U-test and Kruskal-Wallis test. Results: The results are displayed in the following table.

 

 

 

Point

In-ceram

IPS Empress

Celay Alumina

Celay Feldspat

Targis Vectris

 

1.

10±48

70±46

10±42

50±75

50±38

Horizontal

4-5.

30±50

75±33

90±40

20±71

40±38

def. (µ)

9.

130±46

10±103

90±41

10±74

120±39

 

13-14.

40±48

80±64

95±42

5±71

30±40

 

1.

40±41

10±33

0±57

50±77

50±46

Vertical

4-5.

30±37

20±34

30±51

40±74

40±

def. (µ)

9.

0±41

60±38

30±56

60±58

50±50

 

13-14.

45±40

35±39

0±54

0±85

5±371

 

Results: Statistical significant differences were found in vertical and horizontal measurements (p<0.05), Maximum deformation was obtained at glaze (p<0.05), Targis Vectris showed maximum deformation in horizontal plane (p<0.05), Celay Feldspat showed no significant deformation (p>0.05) and the minimal vertical deformation was found on both Celay groups.

Conclusions: Celay Feldspat and Alumina showed maximum resistance to deformation during the fabrication procedures and an excellent marginal fit compare to other materials tested.

 


1835 (18912)

Influence of coping thickness and porcelain addition on the fit of electroformed crowns. Y. HATA*1, Y. TAWADA1, F. WATANABE1, and T.N.C. RAMOS2, 1 The Nippon Dental University, School of Dentistry at Niigata, Japan, 2 University of the Philippines College of Dentistry, Manira, Philippines

Objective: The electroforming technique of fabricating crown copings is gaining popularity because of its numerous advantages over the conventional technique. This study is to determine the fit of electroformed crowns when fabricated at different thickness and with porcelain addition. Methods: 24 prepared maxillary central incisor acrylic teeth (Nisshin Co., Tokyo Japan) were used and were divided into six groups. In groups 1-3, the copings were fabricated at 200, 250, and 300 micrometers respectively while groups 4-6 were with the same coping thickness but with porcelain veneering. The crowns and copings were fabricated by electroforming and were cemented using zinc phosphate cement under 1kg loading. The samples were then embedded in acrylic resin, sectioned labio-lingually along the crown and root axis, and then polished. The cement thickness was measured at the labial and lingual cervical margins and tip of crown portion using the Nikon Profile Projector at 500x magnification. Two-way ANOVA was applied to analyze differences in the marginal fit attributable to the thickness of coping with and without porcelain. Results: The results were the same for all the groups ranging from less than 20 to more than 60 micrometers at the labial and lingual cervical margins. There were no statistical differences on the marginal gaps at each coping thickness and with porcelain addition. Conclusion: The marginal adaptations of Galvano-formed crowns remained acceptable and were not affected by the coping thickness and the addition of porcelain. hata@ngt.ndu.ac.jp


1836 (20929)

The effect of tooth preparation design and spacer setting on fitting accuracy of CAD/CAM ceramic crowns. N. DEI*, T. NAKAMURA, K. WAKABAYASHI, and T. KOJIMA, Osaka University, Suita, Osaka, Japan

Objectives: The aim of this study was to examine the marginal and internal fitting accuracy of CAD/CAM ceramic crowns with different preparation designs and cement space modes. Methods: Using three master dies with different total occlusal convergence angle (4, 8 and 12 degrees), 45 ceramic crowns were produced by CAD/CAM system (Cerec 3, Sirona) with three kinds of spacer modes (10, 30 and 50 µm) setting up by the software, five crowns in each experimental condition. Each of the 45 crowns was returned to its original die and measured for the gaps at the mesial, distal, labial and lingual margins by using a profile projector. The internal fitting accuracy of each crown was determined using a silicone fitting paste. Statistical analysis was performed using a Bonferroni test. Results: The crowns using the die with 4 degrees total occlusal convergence angle had mean marginal gaps of 108/66/61 µm and mean film thickness of 119/116/135 µm (spacer mode 10/30/50 µm). The crowns using the die with 8 degrees total occlusal convergence angle had mean marginal gaps of 108/66/67 µm and mean film thickness of 135/132/162 µm (spacer mode 10/30/50 µm). The crowns using the die with 12 degrees total occlusal convergence angle had mean marginal gaps of 95/53/55 µm and mean film thickness of 136/141/146 µm (spacer mode 10/30/50 µm). Mean marginal gaps were significantly greater with 10 µm spacer mode than with 30 or 50 µm (p<0.001). Mean film thickness was significantly greater with 50 µm spacer mode than with 10 or 30 µm (p<0.001). Conclusion: Within the limitation of this study, it was concluded that 30 µm spacer mode was most suitable for fabricating CAD/CAM (Cerec 3) ceramic crowns regardless of the occlusal convergence angle.


1837 (20898)

A comparison of the compression resistance between ceramic and amalgam restorations. P.V.B. ROCHA*, and L.S.S. MACHADO, Feira de Santana State University, Brazil

In Dentistry, resistance is an important factor to longevity of restorations, becomes a property related to the quality to resist against occlusions forces with no fracture or teeth deformity. The dental structure destruction decreases teeth resistance. It’s often to looking for restorative materials whose can make strong the dental unit affected for injury, bring back your physiology. Objective: this study has the aim to evaluate the resistance against compression of both ceramic and amalgam restorations. Method: Upper bicuspid human healthy teeth, stored in 100% wetting and environmental temperature, were shared into four groups, ten teeth each one, as follow: group I composed by healthy teeth(control); group II composed by teeth prepared only; group III composed by teeth prepared and restored with Noritake ceramic and cemented with Enforce; and group IV composed by teeth restored with amalgam. All the experimental teeth received preparations for intra-coronary restorations MOD-like. Results: It was observed that all groups presented medium fractures values of 136,6 kgf, 60,75 kgf, 97,61 kgf e 79,38 kgf respectively, and there were no statistical differences between healthy and ceramic restorations. On the other hand, it was observed a statistical difference between healthy teeth and only prepared and amalgam restored teeth. Conclusion: Is was possible to infer that ceramic restorations were higher than amalgam restorations in make strong the compromised dental structure


1838 (17460)

Effects of framework designs with thermal analyses of resin-bonded prostheses. C.-H. CHUANG*1, C.-L. LIN1, T.-S. LIN2, Y.-H. CHANG3, and M.-Y. LEE1, 1 Chang Gung University, Taoyuan, Taiwan, 2 National Cheng Kung University, Tainan, Taiwan, 3 Chang Gung Memorial Hospital, Taoyuan, Taiwan

Objectives: Despite the bonding strength between bridge and abutments having reached an acceptable level, the biomechanics of tooth preparation, framework design or oral temperature changes are important factors in the long-term success of resin-bonded (RB) prosthesis. Additionally, computer simulations should be used as a complementary tool to calculate the physical aspects that are difficult to obtain using traditional clinical observations or experimental approaches.

Methods: Significant differences in thermal expansion and conductivity between porcelain and type IV gold alloy were selected as the bridge materials to investigate the effects of various retainer thickness' and thermal-relations for RB prostheses/abutments using the three-dimensional finite element method. Thermal and vonMises stress distributions were observed in 12 simulated models in this study.

Results: The results indicated that the stress values for the bridge and abutment with thin retainer thickness increased 20% and 15% compared to thick designs whenever bridge material was used. When thermal expansion was  considered with the porcelain material used, the peak vonMises stresses for the  prosthesis (£mP, max) in different bridge designs increased to 1.5 times the structural analysis values. Conversely, the peak stresses of the abutment (£mA, max) decreased to half due to the balance between compressive occlusal forces and the tensile thermal stress of teeth expansion. The values of £mP, max and £mA, max obtained from various retainer thickness designs with a gold alloy bridge both increased 2 and 1.12 times the  structural analysis values.

Conclusions:For long-term success of RB prosthesis, bridge material with lower thermal expansion and conductivity might profoundly decrease the unfavorable stress on the remaining tooth. The optimum thickness of RB prosthesis retainers is a more significant issue than the thermal-relations for the failure of bridge and tooth tissue.

 


1839 (15175)

Biomechanical Investigation of Posterior Resin-bonded Prostheses. T.-S. LIN*1, C.-H. CHANG1, and C.-L. LIN2, 1 National Cheng Kung University, Tainan, Taiwan, 2 Chang Gung University, Kwei-Shan, Taoyuan, Taiwan

Biomechanical Investigation of Posterior Resin-bonded Prostheses Since the introduction of resin-bonded prostheses, modifications of bridge design have been proposed. However many of these modifications lack the comprehensive support of biomechanical evaluations and some of them might be the outcomes of engineering intuition. Objectives: The objectives of this study were, therefore, to evaluate the biomechanical effects of bridge designs such as retainer thickness, material stiffness and occlusal rests with finite element simulation. Methods: The solid model of posterior mandibular resin-bonded bridge, which included the abutments (second molar and second premolar) and metal framework, was constructed and meshed with brick elements to perform the stress analyses. Eleven types of occlusal force were applied individually to examine the stress level on the connectors and interface between retainer and abutments. Results: The results showed that the location and direction of occlusal force were major factors in the evaluation of bridge designs. Correct determination of occlusal force for various regions of resin-bonded bridge application is important to reflect the true responses of different bridge designs. In general, a compatible stiffness of retainer with the abutment would decrease the interface stress between the retainer and abutment with a price of generating higher stress in the bridge connectors. The design of occlusal rests could be beneficial to the resin-bonded bridge with better stress distributions on the components. Conclusions: Multiple loading modes should be examined on various designs of resin-bonded prostheses to confirm their clinical performance.


1840 (14393)

STRAIN LEVELS IN CEMENTED AND SCREW RETAINED THREE UNIT FPDs. W. WINTER*1, M. KARL1, S.M. HECKMANN1, F. GRAEF1, T. TAYLOR2, and M.G. WICHMANN1, 1 University of Erlangen-Nuremberg, Germany, 2 University of Connecticut, USA

Objectives: The aim of the in vitro study presented was to quantify the strains around the implants and on the FPD pontics. Methods: 2 dental implants were anchored in a measurement model. Strain gauges were fixed mesially and distally adjacent to each implant and on the bridge pontics. Ten cementable FPDs were directly waxed up on the measurement model (group 1), ten cementable FPDs were fabricated on master casts received from repositioning technique impressions (group 2) and 10 cementable FPDs were fabricated from pick up technique impressions (group 3). 10 screw retained FPDs were made from burn out plastic copings (group 4), ten screw retained FPDs were made casting pontics to gold cylinders (group 5) and 10 FPDs were fabricated with separately cast pontics and glued to gold cylinders on the measurement model (group 6). All screwable FPDs were made based on pick up technique impression models. For statistical analysis multivariate two sample tests were performed, setting the level of significance at p=0.1. Results: The mean strain values for each SG of the different bridge types ranged from 11 µm/m to 566 µm/m with no truly passive fit. The FPDs of group 1 showed the lowest strain levels with significant differences towards all other FPDs except group 2 (p=0.14). Group 6 FPDs showed the next higher strain levels being still more passive than all other groups except group 5 (p=0.26). The differences between group 2 and 3 (different impression techniques) as well as the differences between group 4 and 5 (different modes of fabrication) were not significant (p=0.19 and p=0.43 respectively). Conclusions: All FPDs showed remarkable strains. Impression taking seems to be a major determinant for bridge accuracy. Luting bridge pontics to prefabricated implant components intraorally may help reducing the occurring strains thus leading to more passively fitting superstructures.


1841 (13777)

Effects of materials and structures of adhesive restorations on stress distributions. T. YORIMOTO*1, K. KOBAYASHI1, and K. HIKITA2, 1 Hokkaido University, Sapporo, Japan, 2 Health Sciences University of Hokkaido, Sapporo, Japan

Objectives: In this study, the three-dimensional finite element method was used to evaluate the effects of materials and structures of adhesive restorations on stress distributions. Methods: FEM models were created by reference to extracted human maxillary first premolars. The crown was cut perpendicularly to the tooth axis at a distance of 2 mm (form 1) or 4 mm (form 2) from the central groove. Four types of restoration were used in this study: one type made from resin composite (type A), one type made from porcelain (type B), one type in which the part corresponding to enamel was made from porcelain and the part corresponding to dentin was made from resin composite (type C), and one type in which the occlusal surface layer of 2 mm in thickness was made from porcelain, and other part was made from resin composite (type D). All of the restorations were bonded to abutments with adhesive resin cement. A vertical load of 500 N was applied to the center of the buccal cusp ridge, and the distribution of stresses on the adhesive resin cement layer was investigated using ANSYS/Structural 5.7 (ANSYS, Inc.). Results: In the case of form 1, the maximum stress magnitudes were 42.8 MPa (type A), 40.2 MPa (type B), 44.1 MPa (type C), and 40.7 MPa (type D). The stress distributions in all types of restoration were similar. In the case of form 2, the maximum stress magnitudes were 28.9 MPa (type A), 34.5 MPa (type B), 40.3 MPa (type C), and 28.2 MPa (type D). The results suggested that the stresses in types A and D were reduced by the properties of the restorative materials. Conclusions: The results indicated that type D restoration would be the most useful clinically in terms of wear resistance and mechanical strength as an occlusal material.


1842 (11955)

Effect of Casting Design on Stresses Generated in Vertically Fractured Teeth. A. PLANELLS*, C. JOHNSON, R. HOARD, and A.A. CAPUTO, UCLA School of dentistry, Los Angeles, CA, USA

Objectives: Full coverage castings have been the traditional treatment choice for teeth with incomplete vertical fractures. However, no biomechanical investigations have compared the stressgenerated in such teeth by full coverage castings with that of partial coverage castings. The purpose of this study was to investigate photoelastically the stress production of different casting designs for the treatment of teeth with partial vertical fractures. Methods: Full sized, three-dimensional photoelastic models were made of a maxillary premolarReproducible partial longitudinal cracks were formed s by controlled pressing of a blade into the models. The model teeth were then prepared as follows: inlay, shoed onlay (one shoed cusp and one capped), capped onlay (both cusps capped), and full crown. Gold castings were made for meach tooth model using conventional techniques. With the castings on the models, simulated vertical occlusal loads were applied and resulting stresses were monitored and recorded photographically in the field of a circular polariscope. Results: Under load, the stresses at the crack edge of the inlay model increased substantially and tended to cause propagation of the crack. This effect also was seen, but to a lesser degree, with both onlay designs. In contrast, loading of the full crown tended to decrease the stresses at the crack tip, thereby inhibiting propagation of the crack. Conclusions: The results suggest that the most favorable treatment modality for teeth with partial vertical fractures includes full coverage extending apical to the initial vertical fracture


1843 (16106)

Preliminary Study of the Moisture Spectrum for Different Solvent-based Adhesive Systems. A. REIS*, A.D. LOGUERCIO, and R.H.M. GRANDE, University of São Paulo - Dental Materials, Brazil

 

Objectives: to analyze the moisture spectrum of two different solvent-based systems: Single Bond (SB) and One-Step (OS). Methods:Twenty-four third human molars had the occlusal surface removed to expose a flat dentine surface. An area of about 52 mm2 was delimitated using an adhesive tape. All dentine surfaces were etched (15s), rinsed (15s) and air-dried (30s). Two coats of adhesive were brushed on dry surfaces (0ml) or rewetted surfaces with different amounts of water (1.5; 2.5; 3.5; 4.0; 4.5ml). After a brief air-drying, the adhesive was light-cured for 10s with a light output of 600mW/cm2 (VIP, Bisco). Three layers of resin (Z-250) of ±1.5mm each were light-cured for 30s each. After storage in distilled water at 37°C for 24h, the teeth were longitudinally sectioned in both “x” and “y” directions in order to obtain several sticks with cross-sectional area of ±0.8mm2. The specimens were tested in an INSTROM (0.5mm/min). The data were submitted to ANOVA and Tukey test (a=0.05). Results: The means of bond strength in MPa (±SD), the number of sticks [#] and the results are shown in the table above.
Adhesive 0ml 1.5ml 2.5ml 3.5ml 4.0ml 4.5ml
SB 27.0 (5.8) [58] c 44.5 (11.4) [59] a 40.0 (10.8) [50] a, b 37.8 (16.3) [47] b 21.7 (8.1)   [44] c 18.3 (2.6)   [12] c
OS 24.3 (9.2) [40] c 41.4 (12.7) [35] a, b 42.1 (11.8) [44] a, b 45.7 (11.6) [47] a 42.3 (12.5) [45] a, b --

Conclusion: The adhesive systems behaved differently according to the moisture spectrum, being the adhesive OS more effective in wetter substrate. Supported by CAPES; FAPESP 99/05124-0 and CNPq 300086/01-6

 


1844 (8336)

Comprehensive Boundary Effect of Microhardness. Y.-S. CHENG*, and W.H. DOUGLAS, University of Minnesota, Minneapolis, USA

 

The microhardness test (ASTM, E-384) is applied extensively in dental materials. The problem of boundary effect of microhardness is often encountered when we measure the microhardness from enamel (HK=343) to dentin (HK=68). Objective: This study investigates the comprehensive boundary effect of microhardness. Methods:The sample consists of the composite P60 (15mm x19mm x 4mm) and orthodontic resin medium, its total size is 41.3mm x 41.3mm x 8.0mm. The hardness tests were performed in the BUEHLER Micromet 2004 Microhardness tester. Results: Where L(μm) is the indentation center-boundary distance, and HV is the Vickers Hardness, for P60 under a load of 1000gf the results were as follows:

L(um)

85

117

195

228

321

847

1219

2038

2412

3292

4045

HV

82.1

82.2

85.2

85.7

86.2

87.7

88.3

89.1

89.1

89.9

89.3

For orthodontic resin medium we used the load at 50gf and the results as follows:

L(um)

40

42

66

71

87

90

106

116

211

810

1833

HV

11.9

11.1

8.4

8.6

8.9

8.8

8.4

8.4

8.5

8.4

8.4

The HV asymptotic value of P60 was 89, the orthodontic resin medium was 8.4. Conclusions: The test showed that from P60 to orthodontic resin medium the boundary effect is pronounced (c.f. 82.1 in Table 1and 11.9 in Table 2). When L>10b (where b (μm) is the length of Vickers mean diagonal) the boundary effect can be ignored. Therefore, it is suggest that these boundary rules be considered when microhardness measurements cross the hard tissue and restorative boundaries. Supported by MDRCBB and 3M ESPE, Dental Products.


1845 (11300)

The Effect of Solvent and Filler on Adhesive Shear Bond Strength. R.S. SHADDY*, J.D. O'MEARA, and M.A. LATTA, Creighton University, Omaha, NE, USA

There is some speculation about the adhesive effectiveness to dentin as it relates to the type of solvent used within the adhesive (alcohol, acetone, or water) or whether the resin is filled or unfilled. Objectives: The purpose of this study is to compare the shear bond strength (SBS) to dentin of six 1-component adhesives to include: acetone-base, alcohol-based, water-based, filled, and unfilled adhesives. Methods: Using 600 grit silicon carbide paper on a water-cooled wheel, 48 human extracted molars were ground flat on the buccal surface to expose a complete dentin center. Eight teeth were assigned to each of the following adhesive systems: Prime & Bond NT – acetone/filled (PB) (Dentsply/Caulk), Gluma Comfort Bond and Desensitizer – ethanol/filled (GC) (Heraeus Kulzer), PQ1 – ethanol/filled (PQ) (Ultradent), Single Bond – ethanol/unfilled (SB) (3M Products), One Step – acetone/unfilled (OS) (Bisco), One-Up Bond F – water/unfilled (OU) (J. Morita). Using a #5 gelatin capsule, cylinders of composite resin (Prodigy) were polymerized to the dentin for 60 seconds. Following water storage for 24 hours at 37° C, the specimens were debonded in an Instron testing machine equipped with a chisel-shaped rod at a crosshead speed of 5mm/min. Results: Mean SBS in Megapascals (MPa) for each system was: PQ - 20.3 ± 3.4, SB - 19.1 ± 4.1, PB - 18.6 ± 4.6, GC - 17.4 ± 5.2, OS - 15.5 ± 2.8, OU - 15.2 ± 2.5. A Fisher’s Least-Significant-Difference Test revealed significant differences in the groups (p<0.10).  Symbols denote similar performances.

 

N=8                      Mean (MPAs)       Std. Deviation        Solvent                  Filled/Unfilled

PQ*                      20.3                       3.4                         Ethanol                  Filled

SB*  +                  19.1                       4.1                         Ethanol                  Unfilled

PB*  +   *             18.6                       4.6                         Acetone                 Nanofilled

GC*  +  *  +         17.4                       5.2                         Ethanol                  Unfilled

OS         *  +         15.5                       2.8                         Acetone                 Unfilled

OU             +         15.2                       2.5                         Water                    Unfilled

Conclusions: Laboratory bond strengths were not impacted by solvent or filler.


1846 (14328)

Development of New Organophosphorus Compomer Dental Restoratives With Improved Properties. G.O. ADUSEI*, J.W. NICHOLSON, and S. DEB, GKT Dental Institute, London, United Kingdom

Compomers are designed to combine certain features of conventional composite resin chemistry with that of glass-ionomers. Experimental vinyl phosphonic acid (VPA)-based compomer restoratives A and B have been developed and properties such as wear resistance (WR) using tooth brushing technique and adhesion to tooth using shear bond strength (SBS) evaluated and compared to those of commercial products. Materials A and B contain 3% and 0.3% VPA respectively. Results obtained showed improved properties.

Material

SBS (Standard deviation – (SD)),/MPa

Wear (SD)/microns

1 day

1 week

4 weeks

Material A

13.4, (1.3)

13.0, (1.2)

16.2, (1.2)

56, (4)

Material B

7.5, (1.2)

7.3, (1.2)

8.0, (2.2)

36, (6)

Compoglass F®

12.8, (2.2)

12.6, (1.9)

12.9, (1.6)

114, (8)

Dyract AP®

12.6 (1.4)

12.4, (2.0)

13.6 (1.5)

119, (12)

One-way ANOVA (p<0.05) showed significantly higher SBS in material A at 4 weeks storage in artificial saliva and higher wear resistance than the commercial materials. A higher SBS in material A than in B may be due higher VPA-tooth interaction that enhances adhesion. Experimental VPA-based compomers have improved wear and enhanced adhesion compared with the existing materials.


1847 (7129)

Effect of solvents on bonding to root canal dentin. A. ERDEMIR*1, A.U. ELDENIZ1, S. BELLI1, and D.H. PASHLEY2, 1 Selcuk University, Faculty of Dentistry, Konya, Turkey, 2 Medical College of Georgia, Augusta, USA

Objectives: With the advent of improvements in adhesive dentistry, adhesive post/core systems are becoming popular. The goal is to achieve perfect bonds between adhesive resins and root dentin. The adverse effect of some irrigation solutions or medicaments on bond strength to dentin were have recently been reported. The purpose of this in vitro study was to evaluate the effect of two gutta percha solvents on microtensile bond strength to root canal dentin. Methodology: Thirty extracted human single rooted teeth were used. The crowns and the pulp tissues were removed. The root canals were instrumented and widened to the same size (#70). The teeth were then randomly divided into three groups including ten teeth each. The root canal dentin walls of the roots were treated with chloroform or halothane for 60 s. One group left without treatment as a control. The root canals were obturated using C&B Metabond (Parkell). After 24 h of storage in distilled water, serial 1-mm-thick cross-sections were cut. Microtensile bond strengths to apical, medial and cronal root canal dentin were then measured by using an Instron machine. The data were recorded and expressed as MPa. Results: When the microtensile bond strength values were evaluated according to the regions (apical, medial and cronal), there was no significant difference (p>0,05). The results indicated that chloroform and halothane treatment decreased bond strength to root canal dentin significantly (Control: 23,93 MPa, Chloroform: 18,26 MPa, Halothane: 17,04 MPa) (p<0,05). Conclusion: Gutta-percha solvents have adverse effect on bond strength to root canal dentin.


1848 (8121)

Effect of high-purity glyceryl mono-methacrylate as a dentin primer. C. TANI*, A. MANABE, K. ITOH, H. HISAMITSU, and S. WAKUMOTO, Showa University, Tokyo, Japan

Objectives: The purpose of the present study was to examine the efficacy of high purity glyceryl mono-methacrylate as a dentin primer. Methods: The experimental dentin primers were prepared by diluting one of 90.0%(GM), 96.0%(P-GM96) or 99.9%(P-GM99) purity guaranteed glyceryl mono-methacrylate in the distilled water at the concentration of 35vol%. The efficacy of experimental dentin primers were evaluated by measuring the polymerization contraction gap width of the resin composite (Silux Plus; 3M, USA) restored in a cylindrical dentin cavity and by measuring tensile bond strength to the flat dentin surface. The dentin substrates in the extracted human molar was conditioned with 0.5 mol/L EDTA for 60 sec. The dentin was then primed with one of three experimental dentin primers for 60 sec and the cavity was dried completely. The commercial dentin bonding agent (Clearfil Photo Bond; Kuraray, Japan) was applied in the cavity and irradiated for 10 sec followed by Silux Plus filling. The tensile bond strength of the dentin adhesives was measured 24h after polymerization of composite(Cross-head speed; 0.5mm/min). For the control group, the resin composite was filled into the cavity without the dentin priming. The results were analyzed statistically with StudentÕs t-test(p<0.05). Results: The contraction gap formation was completely prevented in all of the specimens regardless of purity of GM. The tensile bond strength was not significantly affected by the purity of the GM. Conclusions: It was possible to conclude that the clinical use of the high purity glyceryl mono-methacrylate was desirable to avoid the side effect by the impurities.


1849 (21098)

Adhesives for Cationic curing Materials – Bulk Filling and Time Dependance. T. LUCHTERHANDT*, W. WEINMANN, R. GUGGENBERGER, S. THEN, A. STIPPSCHILD, K. DEDE, and R. RICHTER, 3M ESPE AG, Seefeld, Germany

The literature shows that methacrylate composites have decreasing adhesion values when the composite thickness or the storing time is increased[1]. Objectives: The goal of this study was to compare an experimental cationic curing Silorane composite with a shrinkage of 0.8 % and its adapted selfetching all-in-one adhesive (SIL) with a conventional methacrylate composite/adhesive system (Exite/Tetric Ceram [Exc],Vivadent, Schaan) over different composite thicknesses and different storing times. Methods: Tensile bond strength (TBS in MPa)[2] on dentin with 2, 4 and 6 mm increment sizes (Is) after 24 hours were measured for both systems. Also 2 mm increments were used for measurement after 1h, 24 h and one week (time to measurement=Ttm, in hours) on dentin. Results: Results are shown in the table. Statistics (LSD-test, 95% confidence level) revealed, that there is no significant difference with both systems tested, when varying increment sizes or times to measurement where used. Conclusion: This study does not support the results of the literature, and suggests, that further investigation is needed.

Is/system

TBS

Ttm/system

TBS

2/Exc

3,5 ± 1,7a

1/Exc

3,7 ± 1,4a

4/Exc

6,0 ± 2,6b

24/Exc

3,5 ± 1,7a

6/Exc

2,3 ± 0,8a

168/Exc

2,3 ± 0,8a

2/SIL

2,7 ± 1,5a

1/SIL

4,5 ± 1,0ab

4/SIL

2,8 ± 1,7a

24/SIL

2,7 ± 1,5a

6/SIL

3,4 ± 1,9a

168/SIL

3,0 ± 0,7a

[1] R. B. Price, J can Dent Assoc, 66:35 – 39, 2000; [2] Test method of # 2397 (IADR 1997) was used.


1850 (13830)

Characteristics of a New Antibacterial and Fluoride-releasing Bonding System. M. KAWASHIMA*, K. NAKATSUKA, K. OKADA, and J. YAMAUCHI, Kuraray Co., Ltd, Kurashiki, Okayama, Japan

A new antibacterial and fluoride-releasing bonding system (ABF) has recently been developed as an advanced type of "CLEARFIL SE BOND" (SE, Kuraray). ABF consists of self-etching primer (ABP) which is comprised of the adhesive phosphate monomer (MDP), HEMA, water, initiators and the antibacterial monomer 12-methacryloyloxydodecyl pyridinium bromide (MDPB), and bonding agent (KBF) which is comprised of MDP, HEMA, comonomers, initiators and functionalized sodium fluoride. Previous study has shown that ABP provides an excellent antibacterial activity against Streptococcus mutans in some tests ('01 IADR, #1445). Objectives: The purpose of this study was to compare the adhesive properties to tooth structures and fluoride releasing ability of ABF with SE. Methods: & Results: Adhesion tests: bovine enamel (E) and dentin (D) surfaces were treated with self-etching primer for 20 sec., and then gently air-dried without water rinsing. Bonding agent was applied to the surfaces and cured with a visible light. Light cured composite resin CLEARFIL AP-X (Kuraray) was applied following bonding agent. Tensile bond strengths (ABF / SE)[MPa, (SD)] were: after 1day; (E) 23.9(5.9) / 23.8(6.4), (D) 21.9(1.1) / 21.7(2.6) after thermocycling 4000 cycles; (E) 23.5(5.8) / 24.0(5.9), (D) 20.5(4.5) / 20.3(3.3). Fluoride releasing test: bonding agent disk specimens which were cured in 15mm diameter x 1mm were incubated at 37°C in 4ml phosphate buffer solution (pH 7). The eluted fluoride concentrations were determined using a fluoride electrode connected to a digital readout electrometer. Amount of released fluoride from disks for 1 month (ABF / SE)[µg/g] were: 450 / 0. Conclusion: This study demonstrates that ABF provides superior adhesion to tooth substrates as well as SE. In addition, ABF shows effective fluoride releasing. These properties, such as superior adhesion, fluoride releasing and antibacterial activity of ABF would be effective performances for minimally invasive restorations.


1851 (15310)

1-year Evaluation for Bond Strength of an Antibacterial Adhesive System. K. OHMORI*, N. AKIMOTO, A. TAKAO, N. MAEDA, and A. KOHNO, Tsurumi University School of Dental Medicine, Yokohama, Japan

Objectives: An experimental adhesive system (ABF, Kuraray, Osaka, Japan) with antibacterial self-etching primer (ABP) and fluoride-releasing bonding agent (KBF) have shown the same bond strengths as Clearfil SE Bond (Kuraray) to artificial carious dentin over 3 months (Ohmori et al., 2001). The purpose of this study was to evaluate the bond strength of ABF to artificial carious dentin over 1 year. Methods: Streptococcus mutans (108 CFU / ml) was inoculated on class I cavity of sterilized human molar. The tooth was cultivated into bottle that contained BHI agar according to an in vitro tooth model method for making of artificial carious dentin. After incubation for 2 weeks, specimens were divided three groups as follows; Group 1: The cavity was treated with ABP and KBF following manufacturerfs directions. Group 2: The cavity was treated with ABP and Clearfil SE Bond bonding agent. Group 3: The cavities were treated with Clearfil SE Bond. The cavity was built up with Clearfil AP-X (Kuraray) and light cured. The samples were placed into BHI agar and cultivated for 1 year. Sterilized water was applied into the bottles several times to prevent dehydration of BHI agar during cultivation. Micro-tensile bond strengths of the specimens were determined (n=15). The fracture surfaces were also observed by SEM. Results: The results were analyzed by one-way ANOVA and fisherfs PLSD test (p<0.05). Results showed that micro-tensile bond strengths (MPa) and S.D. for 3 groups after 1-year cultivation were 11.0 } 2.6 (Group 1), 8.0 } 3.9 (Group 2) and 9.1 } 3.8 (Group 3). Significant differences were not found among 3 groups to artificial carious dentin between 1-day and 1-year cultivation. Conclusions: In conclusion, the bond strengths of ABF system and SE Bond to artificial carious dentin have not changed over 1 year by using this tooth model method.


1852 (17337)

Effects of adhesion promoters on bond strength of Art-Glass to a luting cement. T.A. PEGORARO*1, N.R.F.A. SILVA1, L.F. PEGORARO1, R.M. CARVALHO1, and M. YAMAUTI2, 1 FOB-USP, Bauru, Brazil, 2 Tokyo Medical and Dental University, Japan

Objectives: To test the effects of several adhesion promoters on the bond strength of a luting cement (Bistite II SC, Tokuyama) to an indirect resin composite material (Art-Glass, Kulzer). Methods: Blocks of resin measuring 10mm x 10mm x 5mm were produced from a silicone mold. Before cementing the blocks to one another, the surfaces were sandblasted with 50 µm AlOx for 30s and treated as follow: G1, Art-Glass liquid; G2, primer A + B of the cement; G3, Art-Glass liquid plus A + B primer; G4, etched with 10% hydrofluoridric acid for 5 min plus Art-Glass liquid; G5, etched plus primer A + B; G6, etched plus Art-Glass liquid plus primer A + B. Control group was cemented after sandblasting with no further treatment. After storage of the cemented blocks for 48h at 37oC, they were vertically sectioned in both “x” and “y” directions to produce several beams of approximately 0.6 mm2 of cross-sectional area. Beams were tested in tension at 0.5 mm/min. Results: Values are in MPa ± SD (N).

Groups

Bond Strength

Significance

G1

45.4 ± 9.6 (23)

A

G2

33.3 ± 8.4 (19)

B

G3

49.2 ± 11.0 (20)

A

G4

24.3 ± 3.9 (19)

C

G5

24.5 ± 10.0 (11)

B C

G6

29.9 ± 6.8 (17)

B C

ANOVA showed that bond strengths were significantly higher when Art-Glass liquid was applied, either alone or in combination with the cement primer (p<0.05). Application of hydroflouridric acid significantly reduced the bond strength (p<0.05). This could be partially recovered by further application of both Art-Glass liquid and primer A+B. Sandblasting alone produced no testable bond strengths. Conclusions: The use of the Art-Glass liquid and the cement primer is of paramount importance to improve bond strength of Bistite II SC to Art-Glass resin composite. Supported by CAPES, CNPq 300481/95-0.


1853 (19872)

Effect of Camphoroquinone Contents on the Shear Bond Strength of Experimental Composites to Bovine Enamel. K.-S. LEE*, and H.-N. LIM, Kyung-Hee University, Seoul, South Korea

A purpose of this study was to confirm the influence of camphoroquione contents on the shear bond strength of experimental light curing composite resins to bovine enamel. Five experimental composites were manufactured experimentally with varying the concentrations of camphoroquinone as 0.2%, 0.3%, 0.4%, 0.5%, 0.6%. Basic composition of experimental composites were monomer (a mixture of Bis-GMA 3 parts and TEG-DMA 1 part) 25% and filler (25micron crushed silica treated with 1% silane at 80°) 75% by weight. Amine were added as 0.2% to total weight. Then camphoroquinone were incorporated with various concentrations. Experimental groups were five including control group. 0.2% camphoroquinone containing composites was considered as a control group. Bovine enamel embedded in resin blocks were flattened on 600# emory paper and etched with 37% phosphoric acid for one minute. After rinse and dry, on etched enamel surface, 3mm dia. and 1mm thick mold was attached as cavity, and filled with each composites. 60 seconds illumination was done. Bonded specimens were immersed in 37° water for 1 day, and shear bond strengths were measured with 1mm/min speed in Instron 4467. 10 measurements were done for each group. Non-linear regression analysis was done between camphoroquinone concentrations and shear bond strength. One-way ANOVA test for Duncan's grouping was done between groups. Results: Results are presented as means and s.d. with MPa. * is a control group.

Groups

Shear Bond Strength

Duncan Group

Camphoroquinone 0.2%*

31.03 (7.40)

A

Camphoroquinone 0.3%

36.56 (3.87)

A

Camphoroquinone 0.4%

39.49 (6.24)

A

Camphoroquinone 0.5%

36.28 (9.09)

A

Camphoroquinone 0.6%

34.02 (5.41)

A

Correlation equation between camphoroquinone contents and shear bond strength was y=-155.14x2+129.81x+11.476 (r2=0.9278). However p-value between groups was 0.3718(p>0.05) which means no statistical differences. Conclusion: These results indicate that although the statistical differences was not confirmed, the optimal concentrations of camphoroquinone for highest shear bond strength may be 0.4%. Kisslee@khu.ac.kr


1854 (21477)

Evaluation of the influence of the primer of a glass-ionomer cement in the dentin adhesion. A. TEDESCO*, A.R.C. DIAS, A.C. LAMOSA, M.A. PARAIZO, K.R.H.C. DIAS, and M.S.D. MIRANDA, Dental School of State University of Rio de Janeiro, Brazil

Objectives: During the application of the glass-ionomer cement primer it is almost impossible to condition only the dentin area that will be lined, therefore the surrounding walls are also conditioned. The purpose of this study was to evaluate by Scanning Electronic Microscopy (SEM) and Shear Stress Test (SST) the ability of the phosphoric acid to remove the Vitremer (3M) primer out of the dentin surface and its influence in the adhesion of the Scotch Bond MP (3M) to the dentin. Methods: Twenty discs of superficial dentin made from 5 newly extracted third human molars were leveled with emery paper, arranged in two groups of ten discs each, and the Vitremer primer was applied. The Group 2 received an aditional application of 37% phosphoric acid (Dentsply) for 15 sec. The remaining primer on dentin was evaluated with the help of SEM by three scorers using a score of 0=no removal to 2=total removal. For the Shear stress test (SHR) twenty teeth were embedded in resin, divided in two groups, the occlusal surface exposed. Each group received the same treatment of the SEM test and one resin cylinder of TPH (Dentsply) with 4 mm high and 3 wide. The SHR were performed in an Instron testing machine at 0.5mm/min. Results: The mean ranking of the SEM evaluations were treated by Kruskal-Wallis and Mann-Whitney tests. The results were: Gr.1=5,50 and Gr.2=15,50. The averages of SHR tests were treated by ANOVA and Tukey test. The results were: Gr.1=14.01 and Gr.2=7,86. All tests showed statistical difference between the two groups. Conclusion: The authors concluded that, in the conditions of the experiment, the phosphoric acid was able to remove partially the glass-ionomer cement primer and this affects the adhesion of the adhesive system to the dentin.


1855 (15942)

Tensile Bond Strength of Composite Resins to Zirconia Ceramic with Different Surface Conditions. F. LEHMANN*, and M. KERN, Christian-Albrechts University at Kiel, Germany

Objective: The purpose of this study was the evaluation of the bond strength and its durability of two modern composite resins to densely sintered zirconia ceramic with different surface conditions. Methods: Plexiglas tubes (inner diameter 3.2 mm) filled with resin Clearfil FII (Kuraray, Japan) were bonded to zirconia ceramic discs with a diameter of 6.4 mm (Cercon, Degussa, FRG). After ultrasonic cleansing in 96% isopropanol, groups of 20 samples were bonded either (P) with Panavia F (Kuraray) or (V) with Variolink II (Vivadent, FL) to the ceramic discs with the following three surface conditions: (O) original surface as supplied by the manufacturer, (A) cleaned for 15 sec with an air-powder-water spray with sodium hydrocarbonate solution, and (S) sandblasted for 15 sec with 50 µm Al2O3 at 2.5 bars pressure. Subgroups of 10 bonded samples were stored for 3 days in tap water at 37°C either (1) for 3 days or (2) for 150 days and additionally thermocycled for 37,500 cycles from 5°C to 55°C. The tensile bond strength was tested at crosshead speed of 2 mm/min. Results: The mean tensile bond strengths (TBS) in MPa were: (PO-3) 20.0±7.9; (VO-3) 10.7±5.2; (VO-150) 0.0±0.0; (PA-3) 28.8±8.9; (PA-150) 2.4±4.2; (VA-3) 8.8±1.9; (VA-150) 0.0±0.0; (PS-3) 44.7±2.2; (PS-150) 39.5±7.6. There were statistically significant differences (SSD) among groups as revealed by the Kruskal-Wallis-test (p<0.001). Groups bonded with Variolink showed SSD to groups bonded with Panavia F (p<0.05, Wilcoxon test). After 150 days storage all samples of groups VO, VA and VS had debonded spontaneously, while in group PA only 3 of the 8 samples did not debond. However after 150 days, group PS showed a high and durable resin bond strength to zirconia ceramic. Conclusions: The use of the phosphate monomer containing composite resin Panavia F on sandblasted zirconia ceramic can be recommended as promising bonding method. Supported by Degussa, FRG.


1856 (17912)

Effect of variation in conditioning times on dentin bond strength. A. ABUHANNA*, University of Florida, Gainesville, USA

It was speculated that incomplete infiltration of the demineralized collagen network could result in a weak zone within the hybrid layer and between the hybrid layer and intact dentin that is susceptible to long-term degradation. Demineralization to a depth greater than monomers can infiltrate and reinforce the collagen network may produce this weak zone. Objectives: The current study evaluates whether reducing the conditioning time to 5 sec or increasing it to 30 sec, from the standard 15 sec conditioning time, has an effect on dentin bonding. Methods: 120 teeth were assigned into 4 groups based on the type of bonding agents, which included three experimental groups of 36 teeth and one control group of 12 teeth .The bonding agents were Single Bond, one-step, Syntac Single Component & All-Bond 2 as a control. Each group was divided into equal three sub-groups (n=12), with each sub-group (a, b and c) conditioned for three different length of times 5, 15, and 30 sec. All groups were bonded with Z 100 composite resin according to the manufacturer's instructions. Results: With all 3 groups combined the mean bond strength results for 5 seconds were higher than both 15 and 30 seconds the significant differences were between 5 and 30 seconds. There were no significant differences between 5 and 15 seconds. There were no significant differences between 15 and 30 sec. significant differences existed among all 3 types of adhesives. For single bond and one step there were no significant differences among the three etching times (5,15,30). For Syntac there were significant differences among the 3 etching times. Conclusions: Etching dentin for less than 15 sec should be considered. Clinically it may not be necessarily to etch dentin more than 5 sec.


1857 (14140)

Effect of Conditioning Time on Bond Strength to Dentin. M.A. LATTA, and T.S. HALD*, Creighton University School of Dentistry, Omaha, NE, USA

Overconditioning dentin with phosphoric acid can lead to demineralization to a depth unable to be penetrated by the resin adhesive. So-called "self-etching"(SE) systems are thought to be self-limiting with respect to overconditioning. Objectives:   The purpose of this study was to determine the shear bond strengths (SBS) of composite to dentin using a conventional and SE systems and various conditioning times. Methods:  Dentin bonding sites were prepared on buccal surfaces of 120 caries-free third molars.  Prime & Bond NT with 34 % phosphoric acid (Dentsply) SE Bond (Kuraray) and Prompt L-Pop (3M/ESPE) were applied at the manufacturer’s conditioning times and at extended times. Spectrum TPH composite was bonded to each dentin site using a gelatin capsule matrix. Following storage in 37 °C water for 14 days debonding was accomplished using a chisel-shaped rod in an Model 1123 Instron testing machine with a crosshead speed of 5 mm per minute. Mean SBS was calculated in Megapascals (MPa)  A 2-way ANOVA with post hoc Tukey’s test was used to analyze the data. Results: 

Bonding Adhesive

Group 1

(Manufacturer recommended time)*

Group 2

(30 seconds)

Group 3

(60 seconds)

Group 4

(90 seconds)

Prime & Bond NT (Dentsply)

19.6 ± 4.2

(15 seconds)

15.4 ± 3.2

10.6 ± 3.6

7.0 ± 6.8

SE Bond (Kuraray)

21.6 ± 5.9

(20 seconds)

19.8 ± 4.6

15.8 ± 4.7

4.5 ± 3.3

Prompt-L Pop (ESPE)

14.3 ± 4.9

(15 seconds)

13.2 ± 3.6

9.2 ± 4.5

3.6 ± 2.7

Both the adhesive system and conditioning time were significant factors (p<0.05). All systems demonstrated lower SBS at longer conditioning times (p<0.05). The SE systems were less sensitive to variations in conditioning time except at 90 seconds. Conclusions:  Excessive over-conditioning reduces SBS of conventional and SE adhesives.


1858 (14307)

Micoleakage of Composite Resin Restorations Using Different Etchant Pre-treatments. D.Y. LIM*, and B.M. OWENS, University of Tennessee, Memphis, USA

The purpose of this in-vitro study was to compare the microleakage of composites using four tooth etchant groups and a control group (no etchant). The groups included: 1) Ultra-Etch™ (Ultradent Products, Inc.) 35% phosphoric acid gel, 2) Ultra-Etch AB™ (Ultradent, Inc.) 35% phosphoric acid gel with Cetylpyridinium Chloride antibacterial agent, 3) 35% phosphoric acid gel followed by Concepsis™ (Ultradent, Inc.) Chlorhexidine Antibacterial solution. 4) Consepsis Scrub™ (Ultradent, Inc.) Chlorhexidine antibacterial slurry, and 5) no etchant (control group). Circular preparations were cut in enamel with a 1 mm bevel. The preparations were treated with/without the appropriate etchant/bonding adhesive (PQ1™-Ultradent, Inc.) The composite resin, Vitalescence™ (Ultradent, Inc.) was placed, cured for forty seconds, and polished. The teeth were thermocycled, sealed with nail varnish, placed in dye for four hours, and sectioned. Leakage was assessed (occlusal margin) using 20x magnification. Scores for microleakage evaluation were: 0-no leakage, 1-leakage one half of the cavity depth, 2-leakage higher than one half of the preparation depth, and 3-leakage including the axial wall. Results from the study indicate that: the groups with no etchant (92%-score 2>) and those with Consepsis slurry (100%-score 2>) revealed more leakage than the other pre-treated cavity preparations (35% phosphoric acid with/without antibacterial agent). Sixty-seven percent of the preparations etched with phosphoric acid only, had a score of 0 (no leakage). Conclusion: etchants containing antibacterial agents can adversely effect microleakage and possibly cause defective restorations. This study was supported by Ultradent Products, Inc.


1859 (14552)

Evaluation of different NaOCl concentrations on shear bond Strength of two adhesive systems. V.G. ARIAS*, A.R. PERIS, A.K. BEDRAN DE CASTRO, and L.A. PIMENTA, Piracicaba School of Dentistry - Unicamp, Piracicaba - SP, Brazil

Objectives: The aim of this study was to evaluate the influence of different concentrations of NaOCl solutions (1, 5, 10%), on shear bond strength of two adhesive systems. Methods: 80 bovine teeth were seccionated in fragments. The buccal surfaces were ground flat to expose dentin and polished on water cooled mechanical grinder with Al2O3 abrasive paper. The specimens were randomly assigned into 8 groups (n=10). The adhesive system Prime & Bond 2.1(Dentsply) - acetone based - was applied on G1, G2, G3 and G4 and Gluma Comfort (Heraeus-Kulzer) - ethanol based - was used in G5, G6, G7 and G8. G1 and G5 were used as control groups. The NaOCl 1% was applied on groups 2 and 6, during 60s. The NaOCl 5% was applied on groups 3 and 7, during 60s and NaOCl 10% was applied on groups 4 and 8, during 60s.The specimens were restored with composite resin Z 250 (3M), the shear bond strength was performed in a Universal testing machine and the data was recorded in MPa. Results: The data were analyzed to 2-way ANOVA and Tukey°¯s test. The means of the adhesive system Prime & Bond 2.1 were: G1=9.11 +/-2.02b; G2=11.84 +/-4.44ab; G3=13.40=/-5.83ab; G4=15.36=/-6.33a (p=0.03); and the means of the adhesive system Gluma Comfort were: G5=17.07=/- 3.54a; G6=16.44+/-4.54a; G7=10.41+/-4.03b ; G8=13.65+/-3.92ab (p=0.03). The results showed statistical differences between the G1 and G4 for Prime & Bond 2.1 and between the G5,G6 and G7 for Gluma Comfort. Conclusion: The use of different concentrations of NaOCl interfered the values of shear Bond strength depending of the adhesive systems used.


1860 (14635)

Variations in Surface Treatments for Composite Repair. J.M. FURGESON*, J.L. VIVAS, P. YAMAN, and G.W. TAYLOR, The University of Michigan, Ann Arbor, USA

Introduction: A major advantage of composite resin is their repairability; however, little information exists on the best technique to successfully bond to a new or existing composite. Objectives: To compare the shear bond strengths of repair interfaces using 3 techniques for surface preparation and repair of composite resin restorations. Methods: Composite samples, 8mm in diameter x 3mm thick, were fabricated and embedded in dental stone. Three groups of 12 samples each were subjected to a different form of surface preparation. All samples were etched with 35% phosphoric acid. Group A (control) received no further preparation. Group B was air-abraded with 50m aluminous oxide at 100 psi and Group C received two parallel, 1mm-deep grooves using a ¼-round bur in a high-speed handpiece. A bonding agent was placed on each sample and light cured. A 2mm Teflon jig was positioned over the exposed composite and filled with an increment of composite resin 2mm thick and light cured per manufacturer’s instruction. The samples were thermocycled 500 times between 5°C and 55°C. The samples were then loaded until failure using a shear stress protocol in an Instron Universal Testing Machine at a rate of 0.5mm/min. Results: The mean shear bond strengths in megapascals were: Group A=24.49 (s.d.=4.36), Group B=28.49 (s.d.=4.25), and Group C=26.98 (s.d.=2.80). Analysis of Variance indicated a statistically significant difference in shear bond strength among the groups (p=0.0503). Groups B and C were significantly different than Group A, but not each other. Conclusion: Additional surface treatment with air-abrasion and/or mechanical retention grooves provided a significant increase in bond strength of the repair interfaces. This suggests a higher success rate for repaired composite restorations may be attainable by the addition of mechanical retention at the repair interface.


1861 (15642)

Effect of dentin surface treatment and storage time on dentin bond strengths. A.K.B. BEDRAN DE CASTRO*1, C.M. AMARAL1, L.A. PIMENTA1, and A.V. RITTER2, 1 Piracicaba School of Dentistry - Unicamp, Piracicaba - SP, Brazil, 2 University of North Carolina at Chapel Hill, USA

Objectives: The purposes of this study were to evaluate the influence of different dentin surface treatment techniques and storage time on dentin bond strengths. Methods: 135 bovine incisors were collected, mounted, ground to expose middle dentin, and randomly divided in 3 groups according to dentin surface treatment (n=45): (1) 37% phosphoric acid (PA) etch + Single Bond (SB, 3M); (2) PA etch + collagen depletion with 10% NaOCl solution + SB; and (3) Experimental self-etching adhesive (EXL 547, 3M). Filtek Z-250 (3M) was applied to the treated surface using a Teflon matrix and thoroughly cured. Each group was further stratified in three subgroups according to storage time: 1-day storage (1d); 7-day storage (7d); and 30-day storage (30d). Specimens were stored in distilled water at 37oC. Shear bond strengths (SBS) were determined using an EMIC universal testing machine at a crosshead speed of 0.5mm/min. The values were analyzed with two-way ANOVA and Tukey’s test (p=0.05). Results: Results are shown in the Table (mean SBS[SD], in MPa):

(1) SB

(2) NaOCL + SB

(3) EXL 547

1d ab

7d a

30d ab

1d bc

7d c

30d bc

1d a

7d abc

30d abc

15.4 (4.4)

17.4 (4.4)

15.3 (3.9)

10.9 (3.4)

9   (1.9)

10.4 (3.6)

16.4 (3.7)

14    (5)

13 (5.8)

Same superscript letters indicate p>0.05

No interaction was observed between surface treatments and storage time. The storage time did not affect bond strengths significantly. Statistically significant differences were observed among the different surface treatments. Conclusions:The experimental self-etching adhesive presents similar dentin bonding potential when compared to SB up to 30 days after bonding. Collagen depletion with NaOCl after acid etching reduced the bond strengths for SB. Storage time did not affect dentin bond strengths for the materials tested.

Adhesives provided for by 3M

 

 


1862 (17486)

Effects of Bonding Adhesives and Conditioners on the Shear Bond Strength of Brackets and Decalcified Enamel. W.-G. CHANG*1, B. LIM, Y. LEE1, and C. KIM, 1 Seoul National University, College of Dentistry, South Korea

Decalcification around bracket is one of major problem in direct bracket bonding. To reduce enamel decalcification, fluoride releasing materials and different enamel conditioners were suggested. Objective: The purpose of this study was to compare the shear bonding strength (SBS) using fluoride releasing and non-fluoride releasing resin bonding system with 34% phosphoric acid and salicylic-lactic (SL) acid. Method: RmGIC also tested with 10% polyacrylic acid conditioning and no etching. Halogen light and Plasma arc light were used. 150 freshly extracted human premolars were collected and stored 0.5% thymol solution. After metal bracket bonding, the specimens were stored in decalcified solution (hydroxyethyl cellulose gel, pH 4.0) for 72 hours at 37 oC and thermocycling at 5 oC and 55 oC in distilled water. The shear bond strength was measured with an universal testing machine (Instron 4465, England) with a cross-head speed of 0.5 mm/min. Nine specimens for each groups were tested. Etched enamel and decalcified pattern were examined with SEM and Confocal Laser Spectroscopy. Results: Means (MPa) and S.D. of SBS were summarized as follows.

 

34 % phosphoric acid

Salicylic-lactic acid

10 % Polyacrylic acid

No conditioning

Halogen

Plasma arc

Halogen

Plasma arc

Halogen

Plasma arc

Halogen

Plasma arc

Enlight

24.40(5.51)

18.21(4.03)

23.79(4.04)

21.23(4.10)

-

-

-

-

Lightbond

26.76(3.08)

25.09(3.73)

22.89(3.57)

16.24(3.14)

-

-

-

-

FujiOrthod

-

-

-

-

16.56(2.29)

17.71(3.47)

6.53(2.27)

9.84(2.12)

Conclusion: SBS of groups using SL acid etching was comparable to 34 % phosphoric acid etching groups. RmGIC showed proper SBS when 10 % PAA was used as conditioner. There were no significantly differences in SBS between two light curing methods (p>0.05). In Confocal Laser Spectroscopy observation, RmGIC and fluoride-releasing resin bond system showed a thinner carious lesion than non-releasing resin bond system. SL etching was shown much smooth surface than the phosphoric acid by visual and SEM.

 

 

 


1863 (18325)

Effect of different root dentin mineralization levels on microtensile bond strength. A.T. HARA*1, C.S. QUEIROZ1, M. GIANNINI1, J.A. CURY1, and M.C. SERRA2, 1 Faculty of Dentistry of Piracicaba / UNICAMP, Brazil, 2 Faculty of Dentistry of Ribeirão Preto / USP, Brazil

Objectives: Adhesion to root dentin seems to be affected by the mineral content of the substrate. The aim of this in vitro study was to evaluate the microtensile bond strength of an one bottle adhesive system (Single Bond/3M) to three root dentin substrates: sound or control [Co], demineralized [De] and remineralized [Re]. Methods: Thirty-six bovine root dentin fragments (5.0x5.0 mm) were obtained and planed (n=12). An area (4.0x4.0 mm) on the planed surface was demarcated with acid resistant varnish, and the fragments were submitted to the following protocols: [Co]: immersion in artificial saliva (pH 7.0) during the experimental period; [De]: immersion in demineralizing solution (1.4 mM Ca, 0.9 mM P, 0.05 M acetate buffer, 0.07 ppm F, pH 5.0) for 32 h; [Re]: immersion in demineralizing solution for 32 h, followed by the immersion in remineralizing solution (1.5 mM Ca, 0.9 mM P, 0.1 M Tris buffer, 10 ppm F, pH 7.0) for 8 days. The fragments were removed from the solutions, rinsed and randomly assigned for bonding procedures. The adhesive system was applied to the exposed surface according to manufacturer’s instructions, and 4.0 mm high composite resin build-up was made. After 24 h, the bonded fragments were serially sectioned to obtain slices (0.7 mm thick) that were trimmed to an hourglass shape. Specimens were tested in tension in an Instron testing machine (4411) at 0.5 mm/min. Results: The bond strength values in MPa were submitted to One-way ANOVA and Tukey’s test (a=0.05). The means (SD) were: control: 19.12(8.04)a, demineralized: 13.51(7.00)ab and remineralized: 6.73(3.02)b (statistical differences were expressed by different letters following the means). Conclusion: The microtensile strength values of remineralized dentin were significantly lower than the normal dentin. The data suggest that the root dentin mineralization level may affect the bond strength.

Supported by FAPESP (process # 00/14278-0).


1864 (18359)

Resin-Dentin Infiltrated Layer and Bond Strength of Self-Etching primers vs One-Bottle Adhesives. P.S. QUAGLIATTO*, Dentistry School of Uberlândia,FOUFU, Brazil, C.L.A. PORTO, (Dentistry School of Araraquara, UNESP, São Paulo), São Carlos-SP, Brazil, and F. GARCIA-GODOY, TUFTS UNIVERSITY, BOSTON, MA, USA

Objectives: To evaluate the resin-dentin interfacial morphology and shear bond strength to dentin of new self-etching primers, an experimental dentin bonding system, and one-bottle enamel-dentin adhesives. Methods: 72 healthy human molars were selected. Flat occlusal surfaces were made with a series of SiC paper into the superficial-to-middle dentin. The following groups were established (12 teeth per group): (G1) SE Bond; (G2) Experimental ABF Bond; (G3) Prime & Bond NT; (G4) Single-Bond; (G5) Tenure Quick F and (G6) Gluma Comfort Bond + Desensitizer. For all groups P60 (3M) composite was used. All adhesives were handled according to the manufacturers' instructions. Immediately after bonding, the specimens were stored in water for 48 hrs and then thermocycled (500x, 5-55°C). Specimens were sheared at a crosshead speed of 1 mm/min in an Instron / MTS machine. The results were analyzed with an ANOVA and Student-Newman-Keuls (SNK) test. All samples were treated with glutaraldehyde, 37% phosphoric acid, NaOCl, HCL, and gold-palladium to be inspected under SEM (Model 840A, JEOL). Results: In MPa: (1) 22.9 ± 4.3; (2) 23.9 ± 3.1; (3) 18.0 ± 2.2; (4) 25.0 ± 4.9; (5) 23.5 ± 4.7;(G6) 22.7 ± 3.2. ANOVA showed a statistically significant difference (P< 0.05) among the groups. SNK test showed that groups 1 vs 3, 2 vs 3, 4 vs 3, 5 vs 3 and 6 vs 3 were statistically significantly different (P<0.05).SE Bond, Experimental ABF Bond, Single-Bond, Tenure Quick F and Gluma Comfort Bond + Desensitizer showed no significant differences among them, but were different from Prime-Bond NT. All adhesives systems produced resin-infiltrated dentin layer with resin tags. Conclusions: Bond strength did not correlate well with the thickness and morphology of resin-infiltrated dentin layer.


1865 (19422)

Shear bond strenght of adhesives systems with and without previous etching. A.M.V.C. LYRA*, D.C.R.E. DANTAS, S.C. LORETTO, L. CORRER SOBRINHO, M.N. CORREIA, and R. BRAZ, Faculdade de Odontologia de Pernambuco, Camaragibe, Brazil

Objective: The aim of this in vitro study was to compare the shear bond strenght of four adhesive systems: Prompt-L-Pop(3M-ESPE), Etch & Prime 3.0 (Degussa), Prime & Bond NT (Dentsply) and Excite (Vivadent), used with and without previous etching. Methods: forty human molars were divided in two groups: the group 1 with etching (37% phosphoric acid) and group 2 without etching. Each group was divided in 8 subgroups with 10 teeth. The crowns were removed at cementum-enamel level, and the remnants crowns were cut off in the mesio-distal way, obtaining two halves, one buccal and another lingual. The dental halves were included in a self-cured acrylic resin and worn out in a mechanical lathe under water refrigeration in order to obtain a plane srface in dentin. The adhesive systems were applied on the dentin with and without previous etching, following by composite resin Filtek Z-250(3M). The samples were stored in distilled water at 37ºC for 24 hours, and submitted to a shear bond strenght test in a universal testing machine (KRATOS) in a speed of 0,5mm/min.Results: ADHESIVE SYSTEM WITH ETCHING MEAN VALUE(MPa) SD Prompt-L-Pop 10,52 3,36 Etch & Prime 3.0 9,14 1,73 Prime & Bond NT 12,21 2,87 Excite 9,66 2,89

ADHESIVE SYSTEM WITHOUT ETCHING MEAN VALUE(MPa) SD Prompt-L-Pop 9,09 2,25 Etch & Prime 3.0 5,56 2,20 Prime & Bond NT 8,88 2,60 Excite 8,44 2,43 The results were analyzed by ANOVA and Tukey Test on the level of significance of 5%. Conclusion: there was no statistical difference between the systems when applied previous etching.


1866 (20616)

Etching Time Effects on the Bond Strength of Two Adhesive Systems. H.D. PHAM*, S.S.A. OLIVEIRA, L.G. WATANABE, G.W. MARSHALL, and S.J. MARSHALL, University of California San Francisco, USA

Dentin bonding begins with demineralization of the substrate. While demineralization of permanent teeth has been extensively studied, optimal demineralization of primary teeth is controversial. Objectives: to evaluate whether the same demineralization protocol for permanent dentin should be applied to primary dentin. Methods:  12 groups of 6 samples of human dentin (primary anterior teeth and permanent third molars) were tested to determine the shear bond strength (SBS) with two adhesives: a self etching primer (SEP) - (Clearfil SE, Kuraray) and Single Bond (SB) (3M) at 3 etching times {5s, manufacturer recommended time (SEP-20s, SB-15s), and 60s}. The acid used with SB was 35% phosphoric acid (3M); the composite was Z100 (3M). Data was analyzed using three-way ANOVA and Tukey-Kramer test. SEM of the fractured specimens was performed to determine the failure mode.  Results: There was no significant difference between the SBS of primary and permanent dentin with the two adhesive systems. Bond strength obtained with the SEP was significantly higher than with SB.  While 5 sec etch produced the highest bond strength to primary and permanent dentin with SB, there was no significant difference with SEP.  Failure mode was cohesive within the adhesive.

 

 

SEP

 

 

SB

 

      Etch Time

      5s

     20s

    60s

      5s

    15s

     60s

Permanent Dentin

30.3±6.8

35.3±2.9

33.1±5.8

35.3±3.7

28.9±2.9

27.3±5.0

  Primary Dentin

35.7±4.4

36.0±6.2

34.9±5.8

33.9±4.3

31.9±3.9

26.2±4.4

Conclusions: Shorter etching time did not adversely affect the bond strength to primary and permanent dentin with SB and SEP. Supported by NIH/NIDCR Grant DE 09859.

 


1867 (20761)

Effect of different treatment on porcelain micro-tensile bond strength to resin. A. MEYER*, L.C.C. VIEIRA, G.C. LOPES, and L.N. BARATIERI, Universidade Federal de Santa Catarina, Florianópolis S.C, Brazil

 

Objective: The aim of this in vitro study was to evaluate the porcelain micro-tensile bond strengths (m-TBS) to resin with three different porcelain pre-treatments: Hydrofluoric Acid (HF), Silanization (S) and HF plus Silanization (HF+S). Methods: Six cylindrical ingots of Lithium Dissilicate (IPS Empress II, Ivoclar) were polished to 600-grid, microetched (50mm) for 15 seconds and rinsed in a ultrason for 10 minutes in distillated water. For group HF the porcelain were acid etched for 20 seconds with 9,5% hydrofluoric acid (Porcelain Etch, Ultradent). For group S, the silane (Porcelain Primer, 3M) was applied on the surface, allowed to evaporate for 3 minutes and air dried for 30 seconds. For group HF+S, both pre-treatment were conducted. The adhesive of Scotchbond MP system (3M) was applied on porcelain and a hybrid composite resin (Filtek Z250, 3M) was inserted and light-cured in four increments of 1mm. After 24 h in water, the specimens were cut in two perpendicular directions to obtain sticks with a low-speed diamond saw (Isomet 1000, Buehler) with a cross section of approx. 0.9mm2 (n=20). The m-TBS was measured in a Bencor device in an Instron machine at a crosshead speed of 0.5mm/min. The data were analyzed with one-way ANOVA. Results: SBS in MPa (Mean±SD):

Porcelain Treatment

HF+S

S

HF

m-TBS

56.8±10.4a

44.8±11.6b

35.1±7.7c

Means with different letter are statistically different at p<0.05

Conclusion: Surface treatment with silane is preferable to etching with hydrofluoric acid. Porcelain etching with hydrofluoric acid combined with silanization results in the highest m-TBS to resin.

 


1868 (21519)

Clinical evaluation of two adhesives on dry vs. moist dentin. A.R. CARMO*1, S. GERALDELI2, J. PERDIGÃO2, and H.R. DUTRA1, 1 University of Mogi das Cruzes, Mogi das Cruzes, SP, Brazil, 2 University of Minnesota School of Dentistry, MN, Minneapolis, USA

Objectives: Some clinicians still dry the cavity preparation after rinsing off the etching gel to check for the enamel frosted aspect. The null hypothesis tested in this clinical study was that drying dentin with air for 3 sec upon rinsing off the acid would not result in lower retention rates than when the cavity was left visibly moist. Methods: Upon IRB approval, 35 patients were enrolled in this study. A total of 128 non-carious class V lesions were divided into four groups: (A) Prime & Bond NT, an acetone-based adhesive applied on moist dentin; (B) Prime & Bond NT applied on dentin dried with air for 3 sec; (C) Single Bond, an ethanol- and water-based adhesive applied on moist dentin; (D) Single Bond applied on dentin dried with air for 3 sec. A microfilled composite resin (Filtek A110, 3M ESPE) was used for all restorations. Clinical evaluations were carried out at baseline and at 6 months using the UNC-modified USPHS direct evaluation criteria. One-hundred and nineteen restorations (a 93% recall rate) were evaluated at 6 months. Retention was computed vs. “adhesive” and “surface moisture” using the Fisher’s Exact test. Results: Retention rates were 97% (one failure) for Single Bond/Moist Dentin and 100% for the remaining three groups. There were not significant differences at p<0.05 (retention rate vs adhesive; retention rate vs moisture). Conclusions: When tested in a short-term period, dentin substrate in non-carious lesions may be less sensitive to variations in dentin moisture than the “ideal” dentin substrate used in the laboratory environment.


1869 (21551)

Micro-Tensile bond strength of a single-bottle adhesive system to cervical sclerotic dentin – Effect of etching time. G.C. LOPES, C.M. BARATIERI*, S. MONTEIRO JR., L.C.C. VIEIRA, and L.N. BARATIERI, Universidade Federal de Santa Catarina, Florianópolis S.C, Brazil

Objective: The aim of this in vitro study was to evaluate the micro-tensile bond strengths (m -TBS) of a total-etch adhesive systems to cervical natural lesions with 2 different etching times (15 seconds vs. 30 seconds). Methods: Sixteen human canines and pre-molars with noncarious cervical lesions saucer-shape were cleaned and randomly assigned to 2 groups. The adhesive system (Single Bond, 3M) was applied on cervical dentin after acid etching with 35% phosphoric acid (Scotchbond Etchant Gel, 3M) for 15 seconds (manufacture’s instruction) or for 30 seconds. The hybrid composite resin (Filtek Z250, 3M) was inserted in three increments and light-cured. After 24 h in water, the specimens were cut perpendicularly with a low-speed diamond saw (Isomet 1000, Buehler) to obtain slices with a cross section of approx. 0.7mm. After that, the slices were trimmed with diamond bur to obtain a surface area of 0.5mm2 (n=25). The m -TBS was measured in a Bencor device in an Instron machine at a crosshead speed of 0.5mm/min. A t-test was computed to compare m -TBS between etching time. Results: m -TBS in MPa (mean± SD):

Etching time

15 sec.

30 sec.

m -TBS

39.1±13.3a

47.3±20.2b

Means with the different letter are statistically different at p<0.05.

A t-test showed that etching with 35% phosphoric acid for 30 seconds resulted in the highest m -TBS to cervical sclerotic dentin than 15 seconds. Conclusion: Extending etching time to 30 seconds may result in a more predictable bond to noncarious cervical sclerotic dentin.


1870 (12422)

Bond Strengths of Nd:YAP Laser-Irradiated Dentins to Composite Resin. M.-S. HUANG*, S.-J. DING, C.-H. LI, M.-T. LI, and C.-C. HSU, Chung Shan Medical University, Taichung, Taiwan

Objectives: Various adhesive systems have been developed, such as phosphoric acid, self-etching, and dental laser-treatment, to use to modify the complex dentinal structures. Laser irradiation has been recognized as a promising method in dental applications of caries prevention. The aim of this study was to investigate the effect of different treatment methods on shear bond strength between resin composite and dentin. Methods: Freshly extracted human molars were sectioned to expose dentin surface, followed by polishing up to 600-grit SiC sandpaper. Four different treatments including phosphoric acid (Scotch Bond, 3M), Liner Bond II (Kuraray, Osaka, Japan), SE Bond (Kuraray) and Nd:YAP laser irradiation (Lokki, France) were carried out. Some specimens were assigned into three groups, NaOCl, EDTA, and phosphoric acid when laser irradiation was conducted previously. All specimens were evaluated using shear bond strength test (EZ test, Shimadzu, Japan) at 0.5 mm/min until failure. Fracture surfaces were examined by scanning electron microscope. Results: The morphologies of dentin surfaces essentially depended on the surface techniques. Laser irradiation could seal the dentinal tubule openings. After conventional phosphoric acid processing, the diameter of the tubules on the dentin surface were opened and enlarged to approximately 5 micro twice more than those for untreated dentin. Shear strengths of phosphoric acid, Liner Bond II, SE Bond, and Nd:YAP laser-treatment dentins were 18.9, 11.5, 15.1, and 13.5 MPa, respectively. Secondary-treatment groups with NaOCl, EDTA, and phosphoric acid after laser irradiation became 13.9, 14.9, and 16.7 MPa of bond strength, respectively, without statistical difference (p > 0.05). There were not significantly different among laser and self-etching groups (p > 0.05). Fracture observation indicated that failure mostly appeared at the interface between composite resin and dental specimen. Conclusions: Laser irradiation can effectively seal the dentinal tubules with a comparable shear strength to those acquired using the self-etching system.


1872 (13374)

Effect of Er:YAG laser on adhesion of resin composite to dentin. D.B. LEGRAMANDI*, M.C. VERONEZI, M.T.A.A. BASTOS, S.E. BERNARDI, and C.E. FRANCISCHONE, University of Sacred Heart, Bauru, Brazil

Er:YAG lasers have been used to remove caries. Adhesive material are required to restore these cavities. Objectives: the aim of this study was to evaluate the effect on dentin surface of Er:YAG laser with 60mJ or 100mJ of power on the bond strength to composite. Methods: fifty extracted human third molars were divided into five groups of 10 teeth. Group 1: surface treatment with Er:YAG laser with 60 mJ of power; group 2: surface treatment with Er:YAG laser with 100mJ; group 3: same conditions of group 1 plus etching with phosphoric acid; group 4: same conditions of group 2 plus etching with phosphoric acid, and group 5: etched with phosphoric acid (control). After surface treatment, adhesive system Single Bond (3M) was applied and cylinders of composite Z100 (3M) were bonded. After 24 hours of storage at 37° C, the specimens were shear tested in an universal testing machine (Kratos) at 0.5mm/min crosshead speed. Results: the mean values in Mpa were: group 1, 7.98±3.23; group 2, 12.64±4.49; group 3, 18.43±7.36; group 4, 12.15±3.59 and control group, 20.80±3.76. Conclusions: the data submitted to Two-way ANOVA allowed to conclude that increasing laser power, shear bond strength increases, acid etching after laser application increases shear bond strength and etching dentin surface with phosphoric acid provides the highest strength between dentin and composite.


1873 (18001)

Effect of Er:YAG laser and air-abrasion on bond strength of two restorative systems. D.T. CHIMELLO*, M.A. CHINELATTI, R.P. RAMOS, J.D. PÉCORA, R.G. PALMA DIBB, and S.A.M. CORONA, University of São Paulo - Ribeirão Preto Dental School, Ribeirão Preto-SP, Brazil

Objectives: The aim of this work was to assess in vitro the effect of Er:YAG laser and aluminum oxide air-abrasion on bond strength of two restorative systems (Z250 – 3M and Flow It! – Jeneric/Pentron). Methods: Forty human molars were selected. Roots were removed and teeth were bisected in a mesiodistal direction and embedded in acrylic resin. Surfaces were grounded with water sandpapers n.180 to 600 until exposure of superficial dentine, obtaining 80 samples, which were randomly assigned into 4 groups (n=20). Dentine was treated with: I - Er:YAG laser (80 mJ and 2 Hz); II - association of laser + phosphoric acid for 15 seconds; III – association of air-abrasion + phosphoric acid, and IV – control - only acid. The adhesive system (Single Bond (A) or Bond 1 (B)) was applied on dentine and then, a cone was prepared with composite resin (Z250 or Flow It!). The specimens were stored in distilled water at 37oC for 24 hours and submitted to the bond strength test using Universal Testing Machine (0.5 mm/min). Results: The means in MPa were: I (A):10.45(±1.73); (B):10.02(±4.11); II (A):14.21(±5.11); (B):7.09(±2.96); III (A):16.47(±4.73); (B):18.21(±5.61); IV (A):16.93(±2.56); (B):9.61(±2.96). Data were submitted to statistical analysis using ANOVA and Tukey test. It was observed that the superficial treatment influenced significantly the bond strength, which was decreased by the laser and increased by the air-abrasion. Z250 restorative system presented the highest averages. Flow-It! system showed the highest value when the air abrasion was employed, which was similar to Z250 with the same treatment or with acid. Conclusions: It can be concluded that the type of superficial dentine treatment influenced the bond strength of the restorative systems. Er:YAG laser alone did not provide an effective bond strength. However the aluminum oxide air-abrasion may improve the adhesion depending on the material employed.


1874 (19015)

Effect of Er:YAG laser on bond strength to dentin of different adhesive systems. R.P. RAMOS*, M.A. CHINELATTI, D.T. CHIMELLO, T. NONAKA, J.D. PÉCORA, and R.G. PALMA DIBB, University of São Paulo - Ribeirão Preto Dental School, Ribeirão Preto-SP, Brazil

Objective: The aim of this in vitro study was to assess the effect of Er:YAG laser on bond strength to dentin of three adhesive systems: a self-etching primer (Clearfil Liner Bond 2V (CL), Kuraray Co.) and two single-bottle bonding agents (Excite (E), Vivadent and Gluma One Bond (GB), Heraeus Kulzer). Method: For such purpose, 30 sound human molars were selected. Roots were removed and teeth were bisected in a mesiodistal direction, performing a total of 60 halves. Each half was embedded in acrylic resin using PVC cylinders and grounded in a polishing machine (Politriz DP-9U2) with water sandpapers n.120-600 until flattened dentin surface was obtained. The adhesion area (3mm diameter) was delimited. Specimens were randomly assigned into 6 equal groups (n=10): for groups I (CL), II (E) and III (GB), the delimited area was treated by a short pulsed Er:YAG laser (80mJ, 2Hz) on defocused mode at a distance of 20 mm; groups IV (CL), V (E) and VI (GB) were not lased. The adhesive systems were applied following manufacturers’ instructions. After surface treatment, for each sample, a composite resin (Filtek Z-250, 3M) cone was prepared using a teflon matrix. After a 24-hour storage in distilled water at 37ºC, bond strength was tested using Universal Testing Machine (0.5mm/min). Results: The results in MPa were: I-21.62(±5.29); II-19.45(±3.84); III-16.30(±3.56); IV-19.20(±2.99); V-15.02(±2.21); VI-15.52(±5.28); Statistical analysis was performed using ANOVA and Tukey test. The analysis of data showed a decrease in bond strength when dentin surface was treated by Er:YAG laser; however, only for Excite, it was statistically significant. Among the adhesive systems, regardless the surface treatment, Clearfil showed statistically superior values. Conclusion: Based of these results, it may be concluded that the use of Er:YAG laser may affect bond strength in higher or lower degree, depending on the adhesive system used.


1875 (20828)

Bond strength of enamel-resinous systems interfaces conditioned with Er:YAG laser. M. GONÇALVES*1, S.A.M. CORONA2, M.C. BORSATTO2, P.C.G. SILVA1, and J.D. PÉCORA2, 1 School of Dentistry of Ribeirão Preto, Ribeirão Preto-SP, Brazil, 2 University of São Paulo - Ribeirão Preto Dental School, Ribeirão Preto-SP, Brazil

Objective: The aim of this in vitro study was to assess tensile bond strength of enamel-resinous restorative systems interface after Er:YAG laser irradiation. Methods: It was used twenty-eight human enamel surfaces from upper extracted third molars, conserved in 0,5% chloramine aqueous solution in refrigerator, planed and divided in two experimental groups and two control groups. The restorative systems selected were Alert (Jeneric/Pentron) and Prodigy (Kerr), with dental adhesives Bond 1 and Optibond Solo, respectively. A special system of alignment composed including tensile specimen, rods and a specific alignment block proposed by ISO TR 11405 (1994) Technical Report Document was used for the tensile strength tests. Result: After statistical analysis using Kruskal Wallis Test, the results demonstrated were: Group IE (laser + acid + Alert): 17, 06 MPa had no difference from Group IC (acid + Alert): 17,02 MPa. The Group IIE (laser + acid + Prodigy): 10,45 MPa for tensile strength and revealed statistical difference from Group IIC (acid + Prodigy): 18,88 MPa of bond resistance. Conclusion: It was concluded that the previously treatment with Er:YAG laser on dental enamel did not increase the bonding resistance for the two condensable resin systems.


1876 (21696)

Evaluation of the tensile bond stength of differents adhesive systems in dentin irradiated with Er:YAG laser. M. PROTO*, Dental school of State University of Rio de Janeiro, Brazil, and K.R.H.C. DIAS, Dental School of State University of Rio de Janeiro, Brazil

Objectives: The purpose of this study was to evaluate the tensile bond strength to dentin irradiated by Er:YAG Laser of composite resin restorations, accomplished with different adhesive systems. Methods: Fifty freshly extracted human third molar teeth had their occlusal enamel removed and were divided in 5 groups: Group 1: 37 % phosphoric acid + the adhesive system Scotchbond Multi Purpose (3M); Group 2: adhesive system Etch & Prime (Degussa); Group 3 Er:YAG laser + 37% fosforic acid + adhesive system Scotchbond Multi Purpose; Group 4: Er:YAG laser + adhesive system Etch & Prime; and Group 5: Er:YAG laser + adhesive system Scothbond Multi Purpose. The ER:YAG laser was used in dentin for 1 minute with energy of 200mJ and 4 Hz of frequency totaling 50 J of energy and 250 pulses. The samples were individually mischievous to a Teflon matrix to make the cylinders of composite resin. After these procedures the specimens were stored in Distilled water at 37oC for 7 days and were submitted to the tensile Strength test. Results: The results (em MPa) were analyzed with Tukey, a parametric test (P<0,05). Their comparison showed no significant differences among the results of the groups 1 and 3, which were respectively 12,76 + 6,5MPa and 8,27+2,2MPa and the same were showed among the results of the groups 2, 4 and 5 that were respectively 3,77+2,39 MPa; 7,57+ 1,86 MPa and 7,1+ 2,2 MPa. However, groups 1 and 3 were statistically better than groups 2, 4 and 5. Conclusions: Based in the results, the authors concluded that the Er:YAG laser is an alternative to etch the dentin and that regardless of the use of that laser, 37% phosphoric acid etching, provides the best adhesion values.


1877 (21752)

Bond strength of dentin submited to the action of aluminum oxide jet. P.C.G. SILVA*1, M. GONÇALVES2, A.L.B. CENTOLA3, T.N.D. NASCIMENTO2, J.T.D. MORAES2, and S.D.T. PORTO NETO1, 1 Faculdade de Odontologia "Julio de Mesquita Filho" - Araraquara - UNESP, Brazil, 2 School of Dentistry of Ribeirão Preto, Ribeirão Preto-SP, Brazil, 3 Faculdade de Odontologia de Ribeirão Preto, Ribeirao Preto, Brazil

Objectives: For the study, tensile test was performed to assess dentin bond strength after treatment with aluminum oxide jet. Methods: It was used the proposal presented by ISO-TR 11405(1994) which suggest a methodological standartization. Results: According to the experimental group distribution, the D1 group (aluminum oxide jet) showed the worst medium value (1,87MPa); the D2 group (aluminum oxide jet + union agent application) presented the medium value of 15,52MPa; D3 (aluminum oxide jet + phosphoric acid + union agent + flowable resin) presented the mediun value of 19,03MP; and for the D4 group (phosphoric acid + union agent+ flowable resin)the medium value was 17,28MPa. Statistical analisys show significances at p<0,01 and p<0,05 levels. Conclusions: It was concluded that the best result of bond strength was achieved by air abrasion treatment associated with phosphoric acid conditioning and bonding agent application.


1878 (18964)

Microleakage in class V cavities after load cycling. S.H. KANG, T.Y. LEE*, and H.H. SON, Seoul National University, South Korea

Flowable and microfill composites have been recommended for Class V cavities. But the use of flowable composites is controversial because of its physical properties. Objectives: The aim of this study was to evaluate the microleakage of 6 composites (2 hybrids, 2 microfills, and 2 flowable composites) with/without load cycling. Methods: Notch-shaped Class V cavities were prepared on buccal surfaces of 180 extracted human upper premolars and then divided into non-load cycling group(G1) and load cycling group(G2). All preparations were restored with 6 composites shown in the Table (n=15). Samples of G2 were subjected to occlusal load (100N/50,000cycles;MTS 858, MTS Systems Corp., Minneapolis, Minn.). All samples were immersed in 2% methylene blue for 24 hours, and sectioned. Enamel and dentin margins were analyzed on a scale of 0(no leakage) to 3(3/3 of wall). Kruscal-Wallis One way analysis and Mann-Whitney U-test were used to analyze the results. Results: There was no significant difference among 6 composites in both enamel and dentin margins of G1 and G2. Load cycling did affect dentin margins restored with Revolution only (P<0.05).

 

Z-250

Denfil

Heliomolar RO

Micronew

AeliteFlo

Revolution

G1/E

0.07 (0.26)

0

0

0

0.13 (0.35)

0

G1/D

1.27 (1.03)

1.33 (0.82)

1.27 (0.80)

1.33 (0.62)

1.4 (0.99)

1.47 (0.74)

G2/E

0.33 (0.82)

0.6 (0.83)

0.27 (0.80)

0.07 (0.26)

0.07 (0.26)

0.07 (0.26)

G2/D

1.87 (0.99)

2 (1.13)

1.73 (1.03)

1.73 (1.10)

1.73 (0.88)

2.4 (0.83)

Table. Mean microleakage value (S.D.)

Conclusions: There was no significant differences in microleakage of Class V cavities restored with hybrid, microfills, and flowable composites (P>0.05). Microleakage was not increased under load cycling except dentin margins restored with Revolution.


1879 (19190)

Microleakage in composite restorations using pulse delay technique. M. POLONIATO*1, P.A. BURMANN2, P.E.C. CARDOSO3, and T. MELO2, 1 University Cidade de São Paulo, Brazil, 2 Federal University of Santa Maria, Brazil, 3 University of São Paulo, Brazil

Recent researches indicate that high-intensity polymerization generates high levels of tension, which may promote marginal fractures and microcracks. One of the suggestions to eliminate this problem is the use of alternative fotopolymerization techniques. Objectives: This study attempts to evaluate the microleakage of occlusal composite resin restorations cured through the pulse delay technique. Material & Methods: 20 extracted human third molars were prepared for class I occlusal restorations (5mm length, 3mm width, 3.5mm depth). Single Bond (3M-ESPE - USA) was applied according to manufacturer’s instructions, and the restorations were incrementally build up with Filtek Z250 composite resin (3M-ESPE - USA), cured through the occlusal position by the following protocol: Group 1: each increment was cured for 30 seconds - 500 mW/cm2 (n=10); Group 2: the first two increments (filling the cavity up to the dentin-enamel junction) were cured for 30 seconds - 500 mW/cm2, and the third (last) increment was cured for 3 seconds - 300 mW/cm2, followed by a 5 minutes waiting period, and a final cure for 30 seconds - 500 mW/cm2 (n=10). The specimens (sp) were stored in water for 24 hours, subjected to 700 cycles of thermal challenge (5 - 55oC, 1 minute dwell time), and finally sealed with nail varnish, in such a way that only the restoration and its margins were exposed to the silver nitrate solution utilized to mark the leakage spots. The visual evaluation was carried after sectioning the sp. Results: all the interfaces evaluated presented zero degree microleakage. Kruskall-Wallis showed no significant differences (P>0.05). Conclusions: the fotopolymerization technique had no influence on microleakage of composite resin class I restorations surrounded by enamel.


1880 (19504)

Influence of mechanical load cycling in cervical microleakage of class II resin restorations associated with self-etching adhesive system. R. BRAZ*, R.C. UCHÔA, M.N. CORREIA, A.M.V.C. LYRA, and S.C. LORETTO, Faculdade de Odontologia de Pernambuco, Camaragibe, Brazil

Objective: The aim of this in vitro study was evaluate the influence of the mechanical load cycling and the capacity of marginal hinder of a self etching adhesive system in the cervical microleakege of 160 restorations(80 teeth) class II(vertical slot of Almquist)in extracted human molars, using resin composed by high load density (Filtek P-60 - 3M). Methods: the specimens were divided in 04 groups, group 1(G1), that didn`t suffer mechanical load, being established as a control group, group 2, 3 and 4(G2, G3 and G4). Each group was subdivided in two subgroups (A and B), where the subgroup A were just accomplished with the self-etching adhesive (Prompt-L-Pop - 3M/ESPE), and the subgroup B being conditioned with 37% phosphoric acid previously the application of the self-etching adhesive system. The specimens were submitted to the mechanical load cycling with totals of 10, 50 and 100 cycles respectively,through occlusal loading of 1 and 17 Kg, immersed, simultaneously, in a dye agent of 0,5% methylene blue. After, all the specimens were rinsed in flow water for 24 hours. Then, were seccionated and evaluated in optical microscope (scale from 0 to 4).Results:the values obtained were submitted to Kruskal-Wallis and Mann-Whitney Tests, with the level of significance of 5%. All groups presented microleakage not related with the number of mechanical cycles, and the use of etching previously self-etching adhesive systems was not able to avoid microleakage. Conclusion: regarding with the found results, it is indicated the use of 50 mechanical cycles for occlusal loading.


1881 (19699)

Microleakage in class V restorations of deciduous teeth prepared with Er:YAG laser. A. RAMOS*1, N. PULGA2, M. VIEIRA3, F. PULGA2, and C.P. EDUARDO4, 1 UNIVERSITY OF SÃO PAULO; UNIVERSITY OF FORTALEZA, FORTALEZA/CE, Brazil, 2 UNIVERSITY OF SÃO PAULO; IPEN, FORTALEZA/CE, Brazil, 3 IPEN, FORTALEZA/CE, Brazil, 4 UNIVERSITY OF SÃO PAULO, FORTALEZA/CE, Brazil

Objectives: the evaluation of microleakage in class V restorations of deciduous teeth prepared using Er:YAG laser and comparison to the ones observed when conventionally prepared, using composite resin and glass ionomer cement, was the subject of this study. Methods: the laser used was the KaVo KEY II with wavelength of 2.94mm, energy of the 300 mJ, repetition rate of 3 Hz and energy density of 86mJ/cm2. Twenty eight deciduous teeth were divided into four groups: G1 – prepared with high speed drill + composite resin; G2 – prepared with high speed drill + glass ionomer cement; G3 – prepared using Er:YAG laser + composite resin and G4 – prepared with Er:YAG + glass ionomer cement. After the restoration the specimens where stored at 37° C for 24 hours, thermally stressed, immersed in 50% aqueous solution of silver nitrate for 24 hours while kept in the dark . The specimens were rinsed in water, soaked in photodeveloping solution and exposed to fluorescent light for 6 hours. After this process the sample were sectioned and observed by stereomicroscopy. For comparison the groups were divided into occlusal and cervical microleakage. The results were analyzed under the Kruskal-Wallis test. Results: for the occlusal microleakage the statistical significance was 5% among the groups and the average comparison showed higher microleakage for G1 (M=35.1) than for G2 (M=24.0) as well as compared to G3 (M=22.3). The other groups didn’t present statistical differences among them. For the cervical microleakage the Kruskal-walls test didn’t present any statistical difference. Comparing the occlusal and cervical microleakage data, for every group, using the Wilcoxon teste, no statistical differences was observed. Conclusions: this study showed the Er:YAG laser to be effective for class V restorations and to result in a smaller microleakage degree using the composite resin.


1882 (19964)

Effect of Class II cavity configuration on microleakage of composite restorations. P.S.L. PRAZERES*1, P.A. BURMANN2, P.E.C. CARDOSO3, and E.H. DUTRA2, 1 Universidade Santo Amaro, São Paulo, USA, 2 Federal University of Santa Maria, Brazil, 3 University of São Paulo, Brazil

Objectives: Verify the effects of class II cavity configuration (retentive or expulsive) and the restorative system (adhesive/composite) on the marginal microleakage of restorations. Materials & Method: 80 human molars were distributed into 8 groups (n=10): Group 1) retentive class II cavity restored with Clearfil SE Bond+Clearfil APX (Kuraray) [SE/APX]; 2) expulsive cavity restored with [SE/APX]; 3) retentive cavity restored with One Step+Renew (Bisco) [OS/R]; 4) expulsive + [OS/R]; 5) retentive cavity restored with Excite+Tetric Ceram (Vivadent) [E/TC]; 6) expulsive + [E/TC]; 7) retentive cavity restored with Single Bond+Z250 (3M, USA) [SB/Z250]; 8) expulsive + [SB/Z250]. The composites were cured (VIP, Bisco) in three layers. The samples were stored for 24 hours and then polished, after which they were submitted to thermocycling (5-55 oC 700 x 1 min.), sealed using fingernail varnish and stained in silver nitrate. The teeth were sectioned in the middle (MD) resulting in one evaluation for each restoration. The images of the sections were digitalized in order to evaluate the microleakage. Results: The average results of 3 examiners were submitted to statistical analysis (ANOVA).

Group

1

2

3

4

5

6

7

8

Scores

0.27 a

0.66 a

2.52 b

2.5 b

3.02 b

2.62 b

0.58 a

0.75 a

Conclusions: For all restorative systems tested the cavity configuration (retentive or expulsive) did not affect the results of microleakage. However, it was possible to detect that the systems SE/APX and SB/Z250 presented statistically lower marginal microleakage than the systems [OS/R] and [E/TC].


1883 (20124)

Marginal adaptation of condensable composite resin using different curing techniques. S.K. PEREIRA*, J.C. SOUZA, L.L. SOUZA, M.I. TRIERWEILER, and F.A. SANTOS, UNIVERSIDADE ESTADUAL DE PONTA GROSSA and UNIVERSIDADE PARANAENSE, PONTA GROSSA - PR, Brazil

Advances in technology have introduced new materials and new curing methods to the market. Objectives: The aim of this in vitro study was to examine the effect of three curing techniques on the extent of marginal gap in class II cavities restored with one condensable resin Surefil (Dentsply) and Prime & Bond NT. Methods: Conservative class II cavities (n=60) were prepared in 30 extracted human teeth (on mesial and distal faces) with cervical margins placed in enamel. The cavities (4x3x2mm) were prepared using a diamond bur (4137 KG Sorensen). All the restorations were cured with the light source KM-100R (DMC-Ltda) for 40 seconds. The teeth were divided into three groups as follows: GI- the cavities were restored using poliester matrix and reflective wedge with three-sited light curing technique; GII- steel matrix and wood wedge were used and the material was cured with softstart-polymerization; GIII- steel matrix and wood wedge were associated with bulk technique and conventional cure. The cervical margins were evaluated after thermal cycling (5ºC and 55ºC for 500 cycles) by quantitative scanning electron microscope (SEM) analysis using an image analyzing system. Results: The ANOVA test revealed significant differences among the GI and GIII (p<0.05). The three-sited technique (GI) showed the lowest gap formation when compared to the bulk technique (GIII). Conclusions: These findings indicated that the curing technique did affect the marginal gap formation of class II condensable resin restorations.This study was supported by PIBIC/CNPq- Brazil.


1884 (20535)

Microleakage of indirect class-V restorations using a new self-etching dentin bonding agent. C.A. MUNOZ, A. ESPINOSA*, J.R. DUNN, and J. SY, Loma Linda University School of Dentistry, CA, USA

Objective: This study evaluated the microleakage of class V indirect composite restorations using two Self etching dentin bonding agent (DBA) (Excite SE) and Clearfil SE Bond and two conventional DBA (Single Bond (3M) and Excite DSC (Ivoclar). Methods: Forty-second molars had Class V preparations on the mesial and distal walls so that the upper wall of the preparation was on enamel and the cervical wall is at the level of the cemento-enamel junction. For Excite SE, Excite DSC and Clearfil SE Bond, Heliomolar indirect restorations were made. For Single Bond, Z100 resin was used. The inlays were cemented using manufacturer's recommended technique for placement of the DBA and the cement. A new Astralis 10 (Ivoclar/Vivadent) was used to polymerize the specimens for 40 seconds. The teeth were stored for 7 days at 37 C in 100% humidity and thermocycled for 2000 cycles (5-55 C). The teeth were sealed and immersed in Fuchsin die for 24 hours, pumiced, sectioned M-D and microleakage was ranked 0 to 4 with 0=no microleakage and 4=Dye penetration along axial wall. Ten Class-V restorations were made for each group. ANOVA and Newman Keuls Test were used to identify differences (P<0.05). Results: Excite SE had a mean occlusal microleakage of 0.29 and 0.01 in dentin as compared to Single Bond that had 0.08 and 0.46 respectively. Clearfil Se Bond had 0.21 on enamel and 0.01 in dentin. Excite DSC had 0.01 on enamel and 0,5 on dentin. Microleakage was not statistically different between Clearfil SE Bond and Excite SE. There was also no difference between Excite DSC and Single Bond. Conclusions: (1) All materials exhibited Microleakage at the dentin and the enamel interface. (2) The self-etching adhesives had more microleakage at the enamel, while the conventional adhesives had more microleakage at the dentin.


1885 (20731)

Influence of salivary contamination on marginal microleakage of pits and fissures sealants. M.C. BORSATTO*, A.G. ALVES, S.A.M. CORONA, D.T. CHIMELLO, and R.G. PALMA DIBB, University of São Paulo - Ribeirão Preto Dental School, Ribeirão Preto-SP, Brazil

Objectives: The aim of this study was to assess quantitatively “in vitro” the influence of salivary contamination on marginal microleakage of pits and fissures sealants. Methods: Forty-eight sound third molars were selected and randomly assigned into six groups: I – application of resinous sealant; II – salivary contamination + resinous sealant; III – adhesive system + resinous sealant; IV – salivary contamination + adhesive system + resinous sealant; V – ionomeric sealant; and VI – salivary contamination + ionomeric sealant. Acid etching was accomplished with 40% polyacrylic acid and 37% phosphoric acid, previously to the application of the ionomeric and resinous sealants, respectively. For contamination of the specimens, it was used 0.01ml of fresh human saliva from an only person, for 20 seconds, followed by surface drying. The ionomeric sealant Ketac-Fil (ESPE/3M), the adhesive system Single Bond (3M) and the resinous sealant Fluroshield (Dentsply) were used. The samples were thermocycled for 500 cycles, immersed in 0.2% Rodamine B for 24 hours, embedded in acrylic resin and sectioned. Microleakage analysis was accomplished by using an optical microscope linked to a camera and a computer. A digitized image was obtained and dye penetration at buccal and lingual cusp heights was assessed quantitatively in millimeters. Results: The averages obtained were: I-0% (±0%); II-31.71% (±31.69%); III-0% (±0%); IV-0% (±0%); V-0.98% (± 2.79%) e VI-11.82% (± 15.45%). The results were submitted to ANOVA and Tukey Test, and it was observed that salivary contamination favoured significantly marginal leakage. The association of adhesive system/sealant promoted a complete marginal sealing, independently of the condition. Conclusions: It was concluded that in the presence of salivary contamination, the association of the adhesive system to the resinuos sealant sealed completely the tooth/sealant interface. The ionomeric sealant presented a better marginal sealing than the resinous sealant under contamination.


1886 (20857)

Effect of composite type and placement technique on resin-dentin interface of posterior restorations. G.C. LOPES*, L.C.C. VIEIRA, L.N. BARATIERI, L. AGUIAR, P. KLAUSS, and C.M. BARATIERI, Universidade Federal de Santa Catarina, Florianópolis S.C, Brazil

Objective: To evaluate the seal capacity of a total-etch one-bottle adhesive system (Prime&Bond NT, Dentsply) with two posterior composite placement techniques (incremental vs. bulk) and two composite resins: a high viscosity packable (SureFil, Dentsply) or a hybrid (TPH Spectrum, Dentsply). Methods: Thirty-two Class II cavities with margins in enamel (2,5mm X 2,5mm X 5mm) were prepared in caries-free fresh-extracted pre-molars (n=8). The cavities were restored with SureFil or TPH as bulk technique (bulk); and SureFil or TPH as an horizontal increment technique (Incr.). After 24 hours in water, teeth were termocycled (500x, 5-55º C, 60s dwell time). After one week in water, the teeth were sectioned mesio-distally with a low-speed diamond saw (Isomet 1000, Buehler) and a PVS impression taken from the resin-dentin interface to control for artifacts during the preparation for SEM. The specimens were subsequently processed for SEM, according to Perdigão et al. 1996. J Biomed Mater Res. The specimens were then embedded in epoxy resin, polished to a high-gloss, sputter coated, and observed under a SEM. The data of % of gap formation were analyzed with two-way ANOVA. A t-test was computed to compare mean gap formation for Bulk vs. Incr. Results: Mean % of gap formation (epoxi replica as control): Incr./TPH=11.3%a; Incr./SureFil=9.8%a; Bulk/TPH=37.9%b; Bulk/SureFil=21.9%a (means with the same letter are not statistically different at p<0.05). Two-way ANOVA showed that Surefil with bulk technique had similar gap formation than incremental technique with TPH or Surefil. TPH with bulk placement had a statistically higher % of gap formation than other groups. A t-test showed that incremental placement resulted in statistically lower percentage of gap formation than bulk technique. Conclusion: Incremental placement technique for posterior composite restorations may still provide better seal than bulk technique. However, if the bulk technique is selected, the use of a packable composite may result in a better seal capacity.


1887 (20885)

Microleakage of resin liners and packable composites using filled and unfilled adhesives. S. DELIPERI*1, D. BARDWELL1, A. PAPATHANASIOU1, K. FALCONE2, D. CONGIU2, and S. KASTALI1, 1 Tufts University School of Dental Medicine, Boston, MA, USA, 2 USA

Objectives: To evaluate the efficacy of differing resin based liner materials in reducing microleakage. Methods: Eighty freshly extracted caries free human premolars and molars were used. MO/DO Class II standardized preparations were performed with the gingival margin placed 1 mm above the CEJ. Teeth were randomly divided into 2 groups each one was divided into 4 subgroups (A-B-C-D for Group I and E-F-G-H for Group II). Each prepared tooth was etched with 32% H3PO4 (Uni Etch-BISCO); in Group I one coat of One Step-BISCO and in Group II 2 coats / 2 cures of P&B NT-DENTSPLY/CAULK adhesives were applied. In each group 1 mm layer of three different liners was used: A2 Heliomolar RO-VIVADENT for A and E; A2 Heliomolar Flow-VIVADENT for B and F; A2 Bisfil 2B-BISCO for C and G. No liner was used for D and H subgroups. Teeth were then restored using 2 mm increments of Pyramid A2 Dentin and A1 Enamel-BISCO and cured with a VIP curing light (BISCO). Teeth were thermocycled 500x between 5°C and 55°C with a dwell of 30 seconds and then placed in a 0.5% methylene blue dye solution for 24 hours at 37°C. Samples were sectioned longitudinally and evaluated for microleakage at the gingival margin under a stereomicroscope at 30x magnification. Dye penetration was scored using an Ordinal Scoring System where 0: no penetration; 1: enamel penetration; 2: dentin penetration. Results: A Chi Square Test revealed a statistically significant difference between Group I and Groups II (p<0.001). Group I yielded the most microleakage. No statistically significant difference was noted between the subgroups; a statistically significant difference of B and D vs. E and H (p<0.01>0.001) and B vs. G and D ( p<0.05>0.01) was also noted. Conclusions: The dentin bonding agent in Group II contributed to a reduction of microleakage when compared to Group I .


1888 (21463)

Effect of Acid and Flowable Resin on Microleakage of a Self-Etching System. P. SOONTHORNSAWAD*, P.A. MIGUEZ, and P.N.R. PEREIRA, University of North Carolina at Chapel Hill, USA

Objective: The purpose of this study was to evaluate the effect of acid etching and use of flowable resin on microleakage of a self-etching primer adhesive system in Class II composite restorations. Methods: Standardized mesial and distal class II slot restorations were prepared in 28 human premolars with dentin or enamel margins and randomly assigned to four groups according to the restorative procedure to be used. Group SE: SE Bond (Kuraray) was the control. Group SE+F: SE Bond and flowable composite resin, Revolution (Kerr). Group Ac+SE: the teeth were acid-etched with 35% phosphoric (3M ESPE) acid prior the application of SE Bond.  Group Ac+SE+FL: the teeth were acid-etched and bonded with SE Bond prior to the flowable composite resin. All teeth were restored with hybrid composite resin, Herculite XRV (Kerr), using incremental technique. After 24 hours at 37C, the teeth were immersed in 1% methylene blue for 24 hours, sectioned and evaluated for microleakage using an ordinal score under a stereomicroscope at 25x magnification: 0-no leakage, 1-leakage to half the gingival wall, 2-leakage to full extension of gingival wall, 3- leakage to the axial wall. Data were analyzed by Wilcoxon Signed Ranks Test (p<0.05).

Results:

 

Enamel

Dentin

Score

SE Bond

SE+FL

Ac+SE

AC+SE+FL

SE Bond

SE+FL

Ac+SE

AC+SE+FL

0

4

5

4

4

6

3

4

6

1

3

1

3

3

0

1

2

1

2

0

0

0

0

1

1

1

0

3

0

1

0

0

0

1

0

0

 There were no statistically significant differences among any group (p>0.05) or between enamel and dentin margins (p>0.05).  SE+FL was the only group that disclosed score 3 for both enamel and dentin.  Conclusions: Acid etching or use of a flowable resin did not improve marginal leakage when using a self-etching primer.

 


1889 (21523)

Microleakage of Class II composite restorations: influence of matrix systems. F.F. DEMARCO, M.S. CENCI*, C.L. PEREIRA, and O.L.V. RAMOS, Federal University of Pelotas, Brazil

Objectives: This study investigated the effect of different matrix systems on microleakage of Class II composite restorations. Methods: Forty proximal standard slot preparations were prepared in 20 non-carious human third molars. In each tooth, mesial cavity had the gingival margin located at enamel level and distal gingival margin was located in cementum/dentin. To simulate clinical conditions teeth were included in a matrix with adjacent teeth. Specimens were randomly divided in two groups (n=20) and restored as follow: Group I – restorations were performed using metal matrix and wooden wedge; and Group II – restorations were performed using transparent polyester matrix and reflexive wedge. All cavities were restored using Single Bond adhesive system (3M) and Z250 composite resin (3M), which were used according to manufacturer’s indications. The incremental Pollack technique was used to fill the cavities. In the metal matrix group polymerization was performed from occlusal aspect, while in polyester matrix polymerization was performed throw the reflexive wedge. A XL 3000 (3M) was used during the experiment. Specimens were stored in distilled water for 7 days and then they were polished. Specimens were submitted to thermal cycling (500 cycles between 5 and 55oC). After that, specimens were isolated with two coats of nail varnish, except the gingival margins and 1mm surrounding them. Specimens were immersed in methylene blue for 8 hours, followed by washing in tap water. Then, specimens were sectioned using a diamond saw and microleakage was assessed using a standard ranking, under magnification (40X). Results: Data were subjected to statistical analysis using non-parametric Kruskal-Wallis. No statistical difference was found between matrix systems employed. Dye leakage was minimum at enamel, being statistically lower (p<0.05) than cementum/dentin margin. Conclusions: Matrix system had no influence on microleakage of class II composite restorations and enamel margins provided better sealing.


1890 (21601)

Effect of different composite resin restorative techniques on microleakage in Class II cavities. J.A. COSTA, C. FRANCCI, F. PINHEIRO, and A.C. SAADIA*, University of São Paulo, Brazil

Objective: The aim of this study is to evaluate different restorative techniques with composite resin in Class II restorations using a microleakage test. Methods: A total of 30 human molars had mesio-oclusal and disto-oclusal cavities prepared. All 60 preparations were randomly assigned to 10 groups (n=6), being 5 groups with cavo-surface margin in enamel (E) and the other 5 groups with cavosurface margin in dentin (D). The restorative techniques studied were: (1) incremental technique; (2) Glass inserts (megafillers) (b-quartz, Lee Pharmaceutics); (3) Self-curing composite resin (Bisfil 2B, Bisco) inside the proximal box and light-cured filling the remaining cavity; (4) Pre-polymerized inserts of composite resin, and (5) Composite matrix technique. The adhesive system used was One Step (Bisco), the light-cured packable composite resin was Pyramid (Bisco) and the self-cured composite resin was Bisfil 2B (Bisco). After finishing, the teeth were thermocycled (700X, 5-55oC, 1 min each), and immersed in 50% silver nitrate, sectioned longitudinally and observed under an optical microscope with magnifications up to 500X. The means for microleakage at the gingival wall were analyzed with ANOVA and compared with Tukey’s post-hoc test (superscript letters, p<0.05). Results: Results in mm (Mean±SD). Enamel: Group 1 –770.3a±340.6; Group 2 - 622.0a±368.6; Group 3 - 581.7a±391.4; Group 4 – 1645.8b±181.4; Group 5 – 850.7a±175.0. Dentin: Group 1 – 413.2a±354.0; Group 2 - 649.8a±252.8; Group 3 – 734.2a±317.6; Group 4 – 1344.7b±308.7; Group 5 – 746.2a±159.9. Conclusions: The restorative technique with pre-polymerized inserts showed higher microleakage at the cervical wall for both enamel and dentin. All the other restorative techniques resulted in similar microleakage scores. No restorative technique was able to seal the cervical interfaces in enamel and in dentin.


1891 (21679)

Fissure sealing with self-etching primers. K.-H. KUNZELMANN, K. BADER*, and R. HICKEL, Dental School of the LMU, Munich, Germany

 

Objective: It would be beneficial if the extra rinsing step during fissure sealing could be avoided by self etching primers. The purpose of this study was to evaluate and compare fissure sealing materials using self etching primers with a conventionally etched (phosphoric acid) fissure sealer.

Methods: The teeth were cleaned with Prophyflex Z 2021 (Kavo, Germany) and the teeth were randomly assigned to the following test groups.

Group 1 :               Helioseal F  was applied to phosphoric acid etched enamel

Group 2 :               NRC, Prime&Bond NT,  Dyract Seal

Group 3 :               Clearfil Liner Bond 2

Group 4 :               NRC , Prime&Bond NT

Group 5 :               PrompLPop and Helioseal F

Group 6 :               Phosphoric acid and Dyract Seal

Group 7 :               Seal&Protect

Group 8 :               NRC, Prime&BondNT, Helioseal F

Each group consists of 10 teeth. Marginal adaptation was evaluated with dye penetration (5 % Methylen-blue, application time: 5 min.). Then the teeth were sectioned longitudinally in the buccolingual direction (3 slices). Afterwards the samples were examined in the light microscope (magnification:10x 4.0) with regard to dye penetration, shape of the fissures, sealer adaptation and air bubbles. In addition the interface morphology was evaluated. The surface of the cut teeth was polished and cleaned. After that they were treated with HCl (6 mol/L ,10 sec.) and NaOCl (12,5 %, 10 min.). Every section was examined in the SEM ( magnification: 3000, 1000, 540).

Results:

 

 The results show that sealing with bonding resin only is not effective. Sealing with self-etching primers in combination with composites showed better results then primer and compomer. The morphological adaptation to the fissure wall was better with sealants in combination with bonding.

Conclusion: There are possibilities to simplify the procedure of fissure sealing, but this should be proofed in a clinical study.


1892 (21726)

Comparative study the microleakage utilizing conventional adhesive technique and selfetching adhesive. Vieira, FLT*; Leao, EC. F. VIEIRA*, Pernambuco University school of dentristry, Camaragibe, Brazil

ObjectiveS:The aim of this “in vitro” study was to do an analysis and a comparison between the dentin adhesives Prime & Bond 2.1 (Dentsply) and Etch & Prime 3.0 ( Degussa ) relative to their capacity to protect the dentin/pulp complex, therefore, decreasing the microleakage at filling / tooth interface. MethodS:It was used 20 (twenty) pre molars human teeth with carious dentinal substratum obtained from the Teeth Banc of Pos Graduation Dentistry Course of UFPE, wich requisits were to be owner of bucal, lingual and pulpal walls. ResultS:The choosen teeth had the carious tissue removed and were divided into two groups: Group 1 : wich cavities were filled by Conventional Adhesive Technique, conditioned with 37 % phosphoric acid and primed with Prime & Bond 2.1 containing fluoride ( Dentsply ). Group 2 – wich cavities were filled by the use of a selfetching adhesive, Etch & Prime 3.0 ( Degussa ) that release acid etch previously. Conclusion:It was used “Definite”resin ( Gegussa ) to fill the booth group specimens. The statistic analysis didn’t reveal significant diferences between the dentin adhesive systems used.


1893 (21742)

The influence of the insertion technique on the marginal microleakage of glass ionomer cements developed to ART technique. D.A. NOGUEIRA*, S. PITHAN, and R.S. VIEIRA, Universidade Federal de Santa Catarina, Florianópolis, AK, Brazil

Objective: The marginal leakage and bubbles presence and localization were compared in class V restorations performed in primary teeth using two high viscosity glass ionomer cements: Ketac-Molar (KM) and Fuji IX (FJ) and two different insertion techniques. Methods: 40 primary sound canines were used in which class V were prepared in their buccal surface laying in enamel and in dentin/cementum. The teeth were randomly divided into four groups and the restorative procedures were performed according to the ART technique. In the first group, the material used was KM and it was inserted into the cavity using an applier syringe Centrix and in group two, the same material was inserted into the cavity using an hand instrument. Groups three and four followed the same steps but the restorative material used was FJ. The teeth laid 24 hours in 37°C with 100% of humidity and after they were submitted to thermal cycling. After, the teeth were immersed in 0,5% basic fuchsin for a period of 24 hours in 37°C and cut at buccal-lingual surface at the center of the restoration. The specimens were evaluate in relation to the marginal leakage both at enamel and dentin/cementum margins and in relation to bubbles presence and localization, under a stereoscopic microscope with 25 times amplification. Results: Marginal leakage means were 1.5 to KM and 1.38 to FJ without differences significant statistically and were observed to be statistically higher at the dentin/cementum margins than at the enamel margins. Bubbles were observed more frequently when the hand instrument. Conclusion: The technique insertion didn't influence in the marginal infiltration, even so the use of the syringe decreased the occurrence of bubbles.


1894 (8267)

Effect of additional acid etching on resin tag formation of self-etching adhesives. K.-T. JANG*, Seoul National University, South Korea, and F. GARCIA-GODOY, Tufts University, Boston, MA, USA

Objectives: To observe resin tag formation of the resin/enamel, dentin interface produced by self-etching adhesive systems and to evaluate effect of additional acid etching on resin tag formation. Methods: Three self-etching primers (SE bond, AQ Bond and Prompt L-Pop) and a one bottle adhesive (Single Bond) were used. Flat occlusal enamel and dentin disks were obtained from extracted human molars. A total of 20 surfaces were collected and divided into four groups of 5 samples each. One-half of each specimen in each group was etched with 35% phosphoric acid prior to the application of each adhesive system, and the second half was kept unetched. Subsequently, resin composite was placed and polymerized. The samples were sectioned with a Silverstone-Taylor microtome and immersed in HCl and NaOCl solutions, followed by drying and sputter coating for examination with the SEM. Results and Conclusions: Additional etching of dentin displayed longer and thicker resin tag than the unetched dentin in all self-etching adhesive groups. In enamel, additional etching displayed deeper and more distinct etching patterns than the unetched group, except for Prompt L-Pop. Ultramorphologically, there was no difference between etched and unetched enamel with Prompt L-Pop.


1895 (9854)

Micro-Raman Spectroscopy of Resin Penetration into Dried, Etched Dentin. M. MIYAZAKI*1, H. ONOSE1, B.K. MOORE2, and J.A. PLATT2, 1 Nihon University, Tokyo, Japan, 2 INDIANA UNIVERSITY, Indianapolis, USA

Objectives: To investigate the pattern of resin penetration into dried, etched dentin using a micro-Raman spectroscopic system (Renishaw). Methods: A one-bottle adhesive system, Single Bond (3M Dental Products) was employed. The facial surface of bovine mandibular incisors were ground wet on 600-grid SiC paper. After etching the dentin, the surface was rinsed with water followed by air blow for 5 sec (dry) or blot dried (wet). Adhesive was applied followed by the resin composite Filtek Z250. After 24 h storage in water, specimens were sectioned through the bonded interface. The sectioned surfaces were then polished with diamond pastes down to 1.0 mm particle size. Raman spectra were successively recorded along a line perpendicular to the dentin/resin interface with the He-Ne laser of a focal size of 0.6 mm. The sample stage was moved by steps of 0.2 mm on a computer controlled X-Y precision table. Additional spectra from regions of dentin and bonding resin were recorded for the control. The relative amounts of the hydroxyapatite (960cm-1, P-O), bonding agent (640cm-1, aromatic ring), and alkyl group (1450cm-1, C-H) in the bonding interface were calculated. Results: From the Raman spectroscopy, a gradual decrease in hydroxyapatite was estimated to extend 2.6-3.0 mm for both groups. The width of collagen rich zone was 3.2-3.8 mm for wet group and 1.8-2.4 mm for dry group. The dentin/resin interface represents a gradual transition of bonding agent from resin side to tooth side and the penetration of the adhesive resin into the demineralized dentin for the dry group was less than for the wet group. Conclusions: From the results of this study, a gradient in resin infiltration into the demineralized dentin was detected and the pattern of resin infiltration of dried, etched dentin was different from that of wet, etched dentin.


1896 (10360)

Nondestructive Measurement of the Quality of the Hybrid Layer with One-Bottle Adhesive Systems. Y. WANG*, and P. SPENCER, University of Missouri-Kansas City, USA

Objectives: Determining the quality of the hybrid layer (HL) has been a formidable problem with the most popular techniques relying on morphologic characterization following treatment of the HL with caustic reagents. The purpose of this study was to evaluate the HL formed at the dentin interface with six contemporary one-bottle adhesive systems using a nondestructive differential staining technique. This technique, which identifies exposed collagenous protein at the light microscope level, does not require vacuum, drying, specimen fixation or resin embedding. Methods: The following adhesive systems were used: Single Bond (SB, 3M), Optibond OLO (OP, Kerr), One-Step (OS, Bisco), Prime & Bond NT (PB, Caulk), Dentastic UNO (UNO, Pulpdent ), PermaQuik PQ1 (PQ, Ultradent). The occlusal 1/3 was removed from 36 extracted, unerupted human 3rd molars. Smear layers were created by abrading the dentin with 600 grit SiC under water. The exposed dentin was treated with one of the adhesive systems per manufacturers' instructions. After 24h aqueous storage, 3 µm thick sections of the d/a interface were cut and stained with Golder's trichrome. Stained sections from each prepared tooth were imaged with light microscopy. Results: The staining technique provided a clear representation of the depth of dentin demineralization, degree of adhesive penetration and infiltration of the exposed collagen. The extent and degree to which the adhesive envelops the exposed collagen is clearly reflected in the color differences in the stained sections. The depth of demineralization appeared comparable among these 6 systems, but adhesive infiltration varied from highest to lowest as follows: PQ > UNO > OS > PB > SB > OP. Conclusion: The composition of the one-bottle adhesive system, including the type/concentration of solvent and ratio of hydrophobic/hydrophilic components, has a substantial effect on resin infiltration of demineralized dentin and the interfacial structure of the hybrid layer. Supported in part by USPHS DE12487.


1897 (10461)

Shear bond strength and interfacial morphology across dentin primed with experimental adhesives. E. VELAZQUEZ1, J. VAIDYANATHAN*1, T.K. VAIDYANATHAN1, M. HOUPT1, Z. SHEY1, and S. VON HAGEN2, 1 UMDNJ-NJ Dental School, Newark, NJ, USA, 2 UMDNJ-NJ Medical School, Newark, NJ, USA

Objective: The objective of this study was to evaluate the dentin shear bond strength and dentin-adhesive interface morphology differences through use of experimental adhesive primers with solvent and curing differences in their formulations.  Methods: The primers were based on commercial formulations (Jeneric Pentron Inc.) of light cure type Bond 1 and dual-cure type Bond 1 C & B using acetone and ethanol as different solvents in a factorial design. Four formulations LC-A, LC-E, DC-A and DC-E (where LC designates light cure, DC- dual cure, A- acetone and E- ethanol) were evaluated. Shear bond strength of composite disks bonded to dentin under standardized methods were determined using Bencor Multi –T testing system. Etched dentin disks were also treated with primer formulations and the interfacial morphology at the tissue-restoration interface was evaluated by scanning electron microscopy after demineralization and deproteination of the samples. Results: The mean and (SD) of shear bond strength (MPa) are: LC-A: 12.0 (2.0), LC-E: 13 (2.5) ; DC-A: 25 (2.5) ; and DC-E: 22 (2.5). Two way ANOVA showed significant differences between mean values of pooled DC and LC groups with DC group showing significantly higher bond strength (p<<0.05). No significant differences were observed between pooled A and E groups (p>0.05). The results indicate non-significant effects due to different solvents used, but significant effects due to polymerization differences.  All samples showed distinct hybrid layer, but no clear differences in their depth profile. Conclusions: Analysis of the results suggests that oxygen inhibition of thin layers may retard polymerization of LC adhesives in the hybrid layer, leading to reduced bond strength.


1898 (11916)

The Morphology Study of Several Self-Etching Adhesive Systems. Y. WANG*, L. SHARP, and B.I. SUH, Bisco, Inc, Schaumburg, IL, USA

Objective: To explore the morphology of self-etching adhesives at the composite-adhesive-dentin interface, and the etching patterns of dentin and enamel. Method: Four products, One-Up Bond F (OU) (Tokuyama), SE Bond (Kuraray), Prompt L-Pop (LP) (3M-ESPE) and Bisco experimental self-etching adhesive (ES) (Bisco), were evaluated, and One-Step (OS) (Bisco) with 32% H3PO4 was used as a control. SEM was used to reveal the resin layer and hybrid layer, the etching pattern of dentin and enamel, and resin tag formation of the four self-etching adhesive systems. Occlusal part of tooth specimens was ground off to expose flat dentin surface. Each adhesive system was applied according to its manufacturer’s instructions and cured with light-cure composite on the top of it. The specimens of resin tag formation were then placed in 1% NaOCl solution for 10min. after soaked in 6N HCL solution over night. The interfacial specimens were sliced perpendicular to bonding interface, about 3mm thick, polished by 1500 Grit Sic paper, 1 µm and 0.3µm alumino slurry, and soaked in 1% NaOCl solution for 10min.   The etching time for etching pattern specimens of each adhesive was according to its manufacturer’s instructions.  The adhesive was rinsed off by acetone followed by water. Result: OU and SE Bond have short resin tags and thin hybrid layer, and LP and ES have relatively long resin tags and thicker hybrid layer.  Tubules on etched dentin of four systems were all opened. Except ES, ground and unground enamel of OU, SE and LP are not totally etched compare with 32% H3PO4. Debonded area in the interface of composite-adhesive-tooth exists in OU and LP. No deboned area was found in SE and ES interfaces. Conclusion: The morphology of the ES is the closest to the fifth generation adhesive system among the four products investigated.


1899 (12535)

Confocal microscopic evidence of the involvement of proteoglycans in the dentin adhesion. A. OYARZÚN*, and E. DREYER, Chile University Dental School, Santiago, Chile

Our previous study, at light and electron microscopic level, (A.Oyarzún and E.Dreyer, J Dent Res, Vol 80 Special Issue,2001) indicated that intratubular glycosaminoglycans-proteoglycans complexes were embedded within the hybrid layer and were detected associated with the lamina limitans. Objective: The aim of this study was to examine by means of confocal laser scanning microscopy the structural interactions between intratubular proteoglycans and dentin adhesives in a total-etch wet-bonding technique. Methods: For that purpose, cervical root dentin segments (n=30) obtained from human teeth extracted for orthodontics reasons were used. The etched surfaces with 35% phosphoric acid gel were bonded using Scotchbond Multi-Purpose (3M Dental Products, St. Paul, MN, USA) according to the manufacturer’s instructions. The primer solution was labeled with TRITC (1 mg/ml). Dentin segments were fixed in an ethanol-formaldehyde-acetic acid solution, demineralized in formic acid and embedded in paraffin. Sections of 20 um were treated with a mouse monoclonal antibody anti-chondroitin sulfate (clone CS-56) and then exposed to FITC conjugated anti-mouse IgG. Confocal optical sections were collected with a confocal laser scanning microscope LSM 410 Invert (Carl Zeiss;Germany). Results:The merged confocal images of immunolabeling and the adhesive system demonstrated that resin tags beneath the hybrid layer were only observed within lamina limitans in all optical sections. TRITC fluorescence was never detected between lamina limitans and the tubule walls composed by intertubular matrix. Moreover, colocalization of chondroitin sulfate epitopes with the adhesive was not observed. Conclusions: Our observations proved that lamina limitans, composed at least by chondroitin sulfates, provided a restricted pathway for adhesive penetration and determined the tag morphology. However,the lack of colocalization between both fluorescent labels suggest that morphological or chemical interactions between dentin proteoglycans and the adhesive system was not observed with this method. Supported by 3M, St. Paul MN, USA and DID grant ODO-013/2 University of Chile.


1900 (15496)

Microstructural Aspects of Restorative Bonding to Potassium Oxalate Treated Dentin: An SEM Study. T. BONSTEIN*, and P.J. BUSH, University at Buffalo, NY, USA

Application of potassium oxalate to dentin reduces sensitivity by formation of calcium oxalate crystals in dentin tubules. In situations where restorations follow desensitizing treatment, success of bonding may be affected by precipitated oxalate. Objectives: To examine microstructural relationships of the oxalate, bonding agent and dentin, and to assess the effect of repeated application of desensitizer. Methods: Dentin slices from freshly extracted human third molars were etched with 37% phosphoric acid (Total Etch, VIVADENT). Dentin desensitizer (SuperSeal, Phoenix Dental) was applied once or twice each for 30 seconds, and then dried for 5 seconds. DBA ( Prime & Bond NT, DENTSPLY) was applied next. The samples were cured for 60 seconds following application of resin composite (Tetric Flow, VIVADENT). The slices were fractured and examined by SEM. Results: The dentin surface appeared etched, with crystalline deposits evident in tubules. The heaviest deposits appeared in a zone between 2 and 10 microns from the dentin surface. Tubules in this zone appeared widened. Above this reaction zone was a layer of demineralized dentin. The crystals exhibited various morphologies; eight-face bi-pyramid typical of calcium oxalate di-hydrate and more frequently ovoid or microlithic morphology associated with calcium oxalate mono-hydrate. These latter were indicative of massive calcium oxalate precipitation. Repeated desensitizer application showed no apparent increase in tubule orifice occlusion. After application of DBA and resin, DBA was evident in tubules above the oxalate crystals. Further penetration into dentin was not evident. DBA infiltration of the demineralized zone was clearly evident. Conclusions: The dual action of phosphoric acid and oxalic acid resulted in a hybrid layer up to 10 microns thick. As the hybrid layer plays a large role in bond success, SEM results predict that bonding should be unaffected by application of potassium oxalate desensitizer. No apparent effect was noted after repeated desensitizer application.


1901 (15609)

Computer modeling and Conformational search for candidate dentin adhesive ligands. S. RANA*, J. VAIDYANATHAN, and T.K. VAIDYANATHAN, UMDNJ-NJ Dental School, Newark, NJ, USA

The results of ongoing studies have shown that computer modeling, systematic conformational search and fit-superposition methods are potentially useful to identify ligands with potential to bind (at the molecular level) to intact collagen fibrils exposed by demineralization of dentin (Vaidyanathan et al, In press, Biomaterials, 2001). Objectives: The purpose of this study was to evaluate monomers containing nitrogen as a hetero-atom, using systematic conformational search followed by molecular fitting of low energy conformations identified by the search. Methods: The molecules included in the study were N-methacryloyl-g-n-butyric acid (NMBu), N-metacryloyl-a-glycine (NMGly) and N-methacryloyl-a-glutamic acid (NMGlu), N-methacryloyl-a-hydroxy proline (NMHP), N-acryloyl aspartic acid (NAAA). 3-D structures of the ligands were modeled by sketching in Sybyl and geometry optimization with Maxmin2 energy minimizer using TRIPOS forcefield parameters. The molecules were subjected to a systematic conformational search with interatomic distance constraints between selected atoms to identify low energy conformations with a common recognition site for potential interaction to a common receptor site. Number of conformations possessing such an active site with respect to a complementary collagen receptor site was identified. The energies of the different conformations were evaluated and compared within and between different molecules. Molecular fitting of the lowest energy conformations of different monomers was used to analyze the RMS values of superposition along the recognition sites. Results: The systematic search resulted in less than 20 conformations with the desired recognition site for interaction with receptor sites. Analysis of the energies of different conformations, electrostatic potential differences and the RMS values of fit indicate potential differences for steric and charge interaction with a common receptor site. Conclusions: The results indicate important differences between ligands and confirm that computer modeling can be used as a biomimetic tool to characterize potential adhesive properties of candidate ligands.


1902 (15897)

Collagen Ligand Interaction: Evaluation of Dentin Primers through Immunochemical Binding Assay. H. JOO*, J. VAIDYANATHAN, C. KASINATHAN, and T.K. VAIDYANATHAN, UMDNJ-NJ Dental School, NEWARK, NJ, USA

The nature of interaction between collagen and ligands in the hybridized dentin formed during dentin bonding is not currently understood properly. Objectives: The objective of this investigation is to characterize collagen-ligand binding of selected dentin adhesive primers using an immunochemical binding assay. Methods: Acid soluble type 1 collagen and two ligands [2-hydroxyethyl methacrylate (HEMA) and acryloyloxy ethyl phosphate (PA)] were used for the analysis. 2.5 mL spots of the collagen solution were made on individual sheets of nitrocellulose paper, and then soaked in solutions of (a) HEMA in ethanol (b) PA in ethanol and (c) ethanol control. After three hours of exposure in the solutions, the sheets were removed, treated with a wash buffer, and then with a blocking solution (TRIS Buffer, BSA) overnight and a wash buffer. A primary antibody (anticollagen type 1) solution was then allowed to soak the sheets for 1-hour. After washing with wash buffer as before, the sheets were exposed to a secondary antibody (anti-goat anti-mouse IgG) conjugated to alkaline phosphatase for 1 hr. After a final wash, the dots were stained (with tetrazolium substrate). The intensity of the color in the collagen spot (both visual comparison and densitometry measurement) was used to differentiate the extent of bound collagen antibody. Results: Differences in the color intensity were detected between the control spot (maximum staining), HEMA treated spot (intermediate staining) and PA treated spot (low staining). The mean gray level range of the stains varied from a low of 104 (control) to a high of 189 for PA. Intensity differences as a function of ligand concentration were also found. Conclusions: Direct evidence for binding interactions between type 1 collagen and dentin primers has been demonstrated for the first time in this study. Collagen ligand binding is influenced by differences in structure and concentrations of ligands.

 

 

 

 


1903 (15936)

The effect of different caries removal techniques on the ultrastructure of dentin. A.C. SEMPRUM*1, J. ALMEIDA1, M.C. PETERS1, J.E. NOR1, S.I. MYAKI2, and E.Y. TANJI3, 1 University of Michigan, ANN ARBOR, USA, 2 UNESP-SJC, Sao Jose dos Campos, Brazil, 3 University of Sao Paulo, Brazil

Objectives: This in vitro study analyzed dentin surfaces after caries removal using various techniques: mechanical (spoon excavator [EX] or carbide bur [CA], N=5), chemo-mechanical (Carisolv™, Mediteam [CS], N=10) and hydromechanical (Er:YAG laser [LA], N=10). Methods: Fifteen freshly extracted (<24 hrs) deep carious molars were ground flat and affected dentin was exposed using a carbide bur. Each sample was fractured in half to obtain two carious surfaces. CS gel was applied for 30 s to one half of the carious lesion and gentle excavation was performed with a specially designed blunt excavator. This procedure was repeated with fresh gel until caries removal was completed. Completion of caries removal was determined by the color and hardness of the lesion with a sharp explorer. Er:YAG laser irradiation (Opus 20-Opusdent, 300 mJ,10 Hz) was applied to the other half to remove the caries. Five samples were treated as external control using spoon excavator or carbide bur for excavation. For each technique, 50 [EX,CA] or 100 [CS,LA] SEM fields (1500x) were evaluated blindly by two investigators. Results: After mechanical excavation by EX or CA the dentin was 100% covered with smear layer. The use of CS with designated instruments resulted in 3/52/45% open/partially open/occluded tubules, respectively. Using LA for caries removal, the remaining dentin showed 57/42/1% for the respective categories, which confirms the need to continue the use of conditioning after LA to achieve a reliable bonding surface. Conclusions: The laser-ablated dentin showed significantly more open tubules (p<0.05) compared to CS-treated surfaces. This data demonstrated that subsequent to caries removal and independent of method used, the remaining dentin needs acidic conditioning to be receptive to bonding.

This study was in part supported by Mediteam, Sweden.


1904 (16575)

Computer visualization of phosphate adhesive molecules used in dentin bonding. M. DEVITO*, J. VAIDYANATHAN, and T.K. VAIDYANATHAN, UMDNJ-NJ Dental School, Newark, NJ, USA

Selected hydrophilic primer molecules used in dentin bonding are based on functional groups with phosphorus as hetero-atom. Objectives: The objective of this investigation was to characterize five phosphate molecules by computer modeling and visualization. Methods: The molecules studied were: 2-acryloyloxy ethylphosphate (PA), 2-methacryloyloxy ethylphosphate (PM), Monomethacryl propanediol monophosphate (MPDM), Monomethacryl glycol phenylphosphate (Phenyl P), and dimethacrylglycol monophosphate (GPDM). The investigation was carried out using a SGI Octane workstation with Sybyl software. The molecules were sketched using an appropriate combination of atom-atom bonds and the fragment structures available in the database. Geometry optimized and energy minimized (via TRIPOS force-field parameters) 3-D structures of molecules were subjected to a systematic search to identify low energy conformations of individual molecules. The energies of low energy conformations of different molecules were computed using molecular mechanics algorithms. The electrostatic and steric complementarities of the molecules were also visualized by computer modeling. Results: There were important differences in the spatial and electrostatic characteristics as revealed by 3-D structures and electrostatic potential maps. Important differences in the van der Waals and electrostatic contributions to the overall energy were also identified. Analysis of the steric and electrostatic complementarities of the molecules and visual comparisons of their structural features, and the charge and morphological features of a collagen receptor molecule were used to qualitatively assess their potential interaction. Conclusions: The results indicate that computer modeling of ligand and receptor molecules can be used as a valuable biomimetic tool to configure favorable structures for adhesive interaction to appropriate sites in receptor molecule.


1905 (17196)

Effect of ultrasonic vibration on resin-dentin bonding : SEM study. J.-W. KIM*, K.-T. JANG, S.-H. LEE, C.-C. KIM, and S.-H. HAHN, Seoul National University, South Korea

Purpose: To observe the effect of ultrasonic vibration on resin-dentin bonding by better resin tag formation. Methods: Ethanol-based one bottle adhesive (Single Bond) and acetone-based one bottle adhesive (Onestep) were used. Flat occlusal dentin disks were obtained from extracted human molars. A total of 10 surfaces were collected and divided into two groups of 5 samples each. One-half of each specimen in each group was treated by recommendation of manufacturer, and then resin composite was placed and polymerized. The second half was vibrated by ultrasonic scaler for 10 seconds after coated with adhesive, and then resin composite was placed and polymerized. The samples were sectioned with a diamond saw and immersed in HCl and NaOCl solutions, followed by drying and sputter coating for examination with SEM. Results: Ultrasonic vibration resulted longer and thicker resin tag with more lateral branches. Conclusions: Better resin tag formation was obtained by ultrasonic vibration than conventional bonding method in both adhesives. Better resin-dentin bonding was obtained by ultrasonic vibration.


1906 (17226)

The effect of laser and surface treatment on dentin and resin/dentin interface. J. ALMEIDA*1, M.C. PETERS1, J.E. NOR1, S.I. MYAKI2, and E.Y. TANJI3, 1 University of Michigan, Ann Arbor, USA, 2 UNESP-SJC, Sao Jose dos Campos, Brazil, 3 University of Sao Paulo, Brazil

Objectives: Optimal adhesion to dentin requires modification or removal of smear layer. Laser treatment of dentin results in a debris-free surface promising good bonding. This in vitro study analyzed dentin surfaces and resin/dentin interfaces cut with Er:YAG laser (KaVo-KEY laser) or carbide bur, and subsequently treated with phosphoric acid (P), non-rinse conditioner (N) or no surface conditioning (-).

Methods: For surface evaluation, the labial surfaces of 10 permanent incisors were prepared into dentin by Er:YAG (250mJ, 2Hz) or carbide, divided in two halves, each receiving one of three surface treatments. For each combination, 50 SEM-fields (1,500 x) from 5 teeth were evaluated blindly by two investigators.

Results: Surfaces:

Dentin Tubules

Er:YAG laser

Carbide bur

 

P

N

-

P

N

-

Open

49

40

29

14

12

0

Partially open

1

10

11

25

34

0

Occluded

0

0

10

11

4

50

The dentin surface treated with Er:YAG laser produced a notably cleaner surface than carbide burs. The laser-treated dentin surfaces showed significantly (p<0.05) more open tubules when conditioned with P (98%), N (80%) or – (58%) in comparison with carbide (all less than 28%).

Interfaces: For evaluation of resin/dentin interfaces, flattened occlusal surfaces of 10 third molars were treated with Er:YAG, followed by surface treatment (P,N, -) and restored with adhesive/resin (N=5). Five ablated surfaces were restored with resin only. All 20 interfaces were analyzed by SEM for formation of hybrid layer and sealing of interfaces.

Conclusions: Laser ablation of dentin, followed by restoration with adhesive and resin, resulted in 100% sealed interfaces independent of surface treatment,

This data demonstrated that Er:YAG laser treatment of dentin resulted in a surface that is receptive to bonding. 


1907 (17928)

X-Ray Microanalysis (EDS) and X-Ray Diffraction (XRD) of dentin treated with KOx and Fluoride based desensitising agents. In vitro study. A.D. SEGALA*, and J.C. PEREIRA, Bauru Dental School, University of Sao Paulo, Curitiba, Pr, Brazil

Introduction: Studies have shown that the reaction of potassium oxalate (KOx)with dentin substrate may result in precipitation of relatively insoluble calcium oxalate (CaOx) crystals on and inside dentin tubules, reducing fluid filtration and dentin hypersensitivity. Objectives: This study aimed to evaluate qualitatively the elemental analysis and the molecular composition of the crystals resulted from the reaction of 4 different desensitizers with dentin: 3 KOx and 1 fluoride (AFP) gels. Materials and Method: EDS and XRD were used for this purpose. Twenty six dentin discs, 1 mm in thickness, were obtained from human extracted third molars. Eight dentin discs for EDS were divided in four groups and treated for 3 minutes with respectively: M1 - 3 % KOx gel - pH 4 (Oxa-Gel, Art-Dent, Br); M2 - 6 % KOx gel - pH 4 (experimental); M3 - 3 % KOx gel - pH 2,5 (experimental) and; M4 - 1,23 % AFP gel - pH 3,6-3,9 (Nupro Acidulated Gel - Dentsply, USA). Sixteen dentin discs for XRD (8 etched and 8 non-etched - EDTA 0.5M) were treated with the same desensitizing agents for 3 and 12 minutes. Two dentin discs with and without smear layer were used as control. Results: EDS: calcium, phosphorus and oxygen were identified equally in the four groups studied. XRD: M1 precipitated CaOx on non-etched dentin for both periods of time and only after 12 minutes on etched dentin; no CaOx was detected with M2 for all the conditions studied; M3 precipitated CaOx in both dentin conditions for the two periods of time; M4 showed CaF precipitation equally for all the conditions studied. Conclusion: Concentration, pH, time and substrate condition may be considered for the prediction of calcium oxalate precipitation from KOx products. Supported by FAPESP # 95/07011-8, Brazil. adsegala@uol.com.br


1908 (18476)

Evaluation of self-etching primer system-enamel interface by SEM after bracket debonding. S. MIASTA*1, M. PARAIZO2, M. MIRANDA2, and K. DIAS2, 1 PUC - RIO DE JANEIRO, Brazil, 2 PUC, UERJ and UFRJ DENTAL SCHOOL, RIO DE JANEIRO, Brazil

Objectives: The aim of this study was to analyze composite resin-adhesive-enamel interface using self etching primers adhesive systems after bracket debonding. Methods: Brackets were bonded to extracted human teeth (five for each group) with one of three adhesive systems following the manufacturers instructions: Gr 1 – Concise adhesive system (as control); Gr 2 - Clearfil Liner Bond 2V acidic primer; and Gr 3 - Etch & Prime 3.0 acidic primer. After debonding procedure, samples were included in Epoxi resin and the adhesive interface was observed by SEM. Three calibrated examiners assessed adhesive remaining on the tooth surface by the following score: 1 – less than 25%; 2 – more than 25% but less than 50%; 3 – more than 50% but less than 75%; and 4 – more than 75%. Results: The average rank were: Gr 1 – 11.90; Gr 2 – 7.90; and Gr 3 – 5.50. Data were analyzed by Kruskal-Wallis and Mann-Whitney tests. There was statistically significant diference among groups (p< 0.05). Conclusions: The authors concluded that acidic primers systems left less residual resin. Clearfil Liner Bond 2V was more promising since composite resin remains bonded to the tooth after bracket removal with minimum impregnation, while Etch & Prime 3.0 didn’t show enough impregnation.


1909 (19485)

Morphological analysis of adhesive/dentin interfaces and dentin surface after different superficial treatments. J.S. BARRETO*, D.T. CHIMELLO, S.A.M. CORONA, R.G. PALMA DIBB, and M.C. BORSATTO, University of São Paulo - Ribeirão Preto Dental School, Ribeirão Preto-SP, Brazil

Objective: The aim of this study was to analyze the adhesive/dentin interfaces, as well as the morphological changes on dentin after different superficial treatments, using Scanner Electron Microscopy. Methods: For this purpose, ten disks from human molars (1mm thick) were grounded with water sandpapers n. 280-600 to provide a standardized smear layer. The specimens were randomly assigned into five groups: I- 37% phosphoric acid, II- aluminum oxide air abrasion, III- air abrasion + 37% phosphoric acid, IV- Er:YAG laser (80mJ/2Hz) and V- Er:YAG laser + 37% phosphoric acid. Before superficial treatment, the disks were bisected and one half the restorative system was applied (Single Bong/Filtek Z-250 - 3M) and other half only surface treatment was accomplished. The samples were bisected perpendicularly to the surface and prepared for SEM analysis. Results: The presence of irregularities on dentin surface, obliterated, left debris in the tubules and absence of hybrid layer were observed when the surface treatment was performed with air abrasion. The same result was found when the laser was used, except dentin tubules that were opened. In the group laser + acid, there was not homogeneous hybrid layer formation. A satisfactory result was observed in the group air abrasion + acid. Irregularities on the surface and open tubules allowing the observation of the hybrid layer and tags were found in the group air abrasion + acid. These results were similar to those reached when acid-etching technique was used. The analysis of the dentin surface showed no enlargement of the tubules when the laser was used. Conclusions: Based on the results, it may be concluded that the association of aluminum oxide air abrasion and phosphoric acid etching is required to provide an adequate surface for hybrid layer formation and a satisfactory adhesive/dentin interface.


1910 (19582)

Identification of dentin collagen fibrils and proteoglycans: a double labeling technique. L. BRESCHI1, G. PASQUANTONIO*1, M.M. LOPES2, P. GOBBI1, M. FALCONI1, and J. PERDIGÃO2, 1 University of Bologna, Italy, 2 University of Minnesota, Minneapolis, USA

Objectives: The aim of this study was to analyze the effectiveness of different acids to expose the collagen fibrils (CF) and the proteoglycans (PG) of the dentin matrix using a double labeling immunocytochemical technique and high resolution SEM. Methods: Dentin disks obtained from human molars were etched for 15 sec with 10% maleic acid, 10% citric acid, or 35% H3PO4; control specimens were prepared by conditioning the dentin surface with EDTA pH 7.0 for 45 min. Specimens were immunolabeled with a monoclonal antibody anti-chondroitin sulphate and a monoclonal antibody anti-type I collagen. Gold labeling was performed using secondary antibodies conjugated with 15 nm colloidal gold particles (for the PG visualization) and with 30 nm colloidal gold particles (for the CF visualization). Specimens were then fixed, dehydrated in ascending ethanol and observed under an high resolution SEM (Jeol 890). Results: Maleic and citric acid conditioned specimens revealed an intense labeling of CF both in the intertubular dentin and on the peritubular matrix. PG were identified as a network of lateral branching fibrils connecting and stabilizing the major CF. On dentin etched with 35% H3PO4 the dentin PG were clustered in spots of colloidal gold particles, mostly localized in the peritubular dentin, few spots were evident on the intertubular area. Details of the clusters revealed a preferential localization of the gold particles on globular structures intimately joined to the dentin CF. The globules showed as spherical electron reflective material with a diameter ranging from 20 to 50 nm. EDTA conditioned specimens revealed a distinct labeling of CF and PG, particularly localized on the peritubular dentin. Conclusions: The use of 35% H3PO4 on dentin produced significant structural modifications in the dentin matrix. Both CF and on the PG revealed morphological modifications induced by H3PO4 which were not visualized with the application of weaker organic acid such as citric and maleic acid.


1911 (19892)

TEM analysis of the hybrid layer: a double labeling immunocytochemical approach. M.M. LOPES*1, L. BRESCHI2, M. FALCONI2, C. PRATI2, G. PASQUANTONIO2, and J. PERDIGAO1, 1 University of Minnesota School of Dentistry, Minneapolis, MN, USA, 2 University of Bologna, Italy

Objectives: Type I collagen fibrils (CF) and proteoglycans (PG) are the main constituents of the dentin organic matrix. After etching with acid, CF and PG are embedded in the adhesive forming a hybrid layer (HL). The aim of this study was to identify type I CF and PG using a double labeling immunocytochemical technique under the TEM. Methods: Recently extracted premolars were sectioned in 1 mm-thick dentin disks. Dentin wafers were prepared with the following adhesive agents: (1) Prime&Bond NT, (2) OptiBond SOLO Plus, (3) Single Bond, (4) APF. All materials were applied following the manufacturers’ instructions. Fixation was carried out by immersion in 4% paraformaldehyde in 0.1 M. sodium cacodylate buffer pH 7.2, dehydration in graded concentrations of ethanol, and embedding in LR White. Thin sections (80nm) were cut with a diamond knife, mounted on Formvar nickel grids and the incubated with a IgG monoclonal antibody anti-type I collagen and a IgM monoclonal antibody anti-chondroitin 4 and 6 sulphate. Secondary antibodies were then incubated overnight in a anti-mouse IgG conjugated with 30 nm colloidal gold particles (for the CF visualization) and a anti-mouse IgM conjugated with 15 nm colloidal gold particles (for the PG visualization). Specimens were then analysed under TEM Results: TEM analysis confirmed the formation of a HL and the embedding of the CF and PG into the polymerized adhesive agent. Detection of the CF and PG within the HL was evident for the tested adhesives. In particular the hybridization of the peritubular dentin revealed intense labeling of the dentin matrix. Conclusions: The use of a double labeling immunocytochemical technique allowed us to analyze the fine morphological and structural details of the HL as well as the relationship between the dentin adhesives and the dentin matrix.


1912 (21622)

Effect of phosphoric acid etching on sclerotic dentin – An AFM and FE-SEM Analysis. G.C. LOPES, L.F. MARTINS, E.M. ARAÚJO, Jr.*, L.N. BARATIERI, L.C.C. VIEIRA, and M.A.C. ANDRADA, Universidade Federal de Santa Catarina, Florianópolis, Brazil

Objective: To evaluate ultra-morphology of human sclerotic dentin etched with phosphoric acid using an AFM and a FE-SEM. Methods: Sixteen human molars with caries were transversally cut with a diamond saw under refrigeration. The occlusal surfaces were grid until remove the carious lesion, exposing regions with sclerotic dentin and regions with normal dentin. A visual examination and a microhardness test was conducted to select between sclerotic dentin (i.e. translucent and harder region) and normal dentin. Smear layer was created by abrading the dentin with 600-grid SiC, roots were cut and 16 dentin discs were obtained. One half of the specimens were analyzed under AFM (PicoScan SPM, Molecular Image) before and after being treated with 35% phosphoric acid (3M) for 15 seconds and rinsed off with water for 10 seconds. Similarly, the other half were fixed, dehydrated, fractured, sputter coated, and observed under a FE-SEM (XL-30FEG, Philips). Results: The thin and soft smear layer permitted the scanning probe of AFM to examine the dentin structure. The sclerotic dentin showed tubules with lower diameter and a prominent peritubular dentin. Acid etched specimens showed a deposit of mineral on intertubular dentin not present on normal dentin, with some tubules occluded by mineral deposits. The FE-SEM examination of the fractured specimens showed a crystalline mineral deposit inside of the some tubules and the demineralyzed zone was not evident. The transversal images of etched sclerotic dentin showed mineral amounts, not removed by acid etching on intertubular dentin, occluding the lumen of tubules in some areas. On normal dentin, the acid etching results in an intertubular demineralyzed zone of 2-3 um. Conclusion: Sclerotic dentin showed to be a high mineralized substrate which has morphological differences compared to normal dentin and does not react at same manner when exposed to acid etching.


1913 (11207)

Flexural Strength of Repaired Composite Materials: Function of Surface Treatment. A.V. RITTER*, J.Y. THOMPSON, and E.J. SWIFT JR, University of North Carolina at Chapel Hill, USA

Objectives: The purpose of this study was to evaluate the flexural strength of composite specimens repaired using different surface treatments.  Methods: 20 rectangular composite specimens (Charisma, Heraeus Kulzer) were fabricated using a split 15/2/2.5mm aluminum mold.  A spacer was used to generate 8 mm-long specimens.  After thorough light curing and removal from the mold, specimens were saved in distilled water at 37C for 30 days.  After the incubation period, one end of each specimen was wet polished to 600-grit, and sandblasted (Microetcher II, Danville Engineering) for 5 s with one of the following abrasive particles (n=10): 50 mm Al2O3 particles (Ortho-Direct, Inc.) or 30 mm Al2O3 particles with silanized silica coating (CoJet, 3M ESPE).  The sandblasted surfaces were treated with CompoConnect (Heraeus Kulzer) and returned to the split mold.  Composite (Charisma) was added to the mold and light-cured, generating 15/2/2.5mm-repaired specimens.  Control non-repaired specimens were prepared using the same dimensions (n=10).  All composite specimens were fully cured with a XL 3000 light-curing unit (3M ESPE).  Specimens were loaded to fracture in an Instron universal testing machine using a four-point bending setup.  Flexural strengths were calculated in MPa by factoring specimen dimensions, peak load, support span, and loading span.  Values were submitted to statistical analysis using the SPSS package.  Results: Results are in the Table (mean, SD, in MPa):

Control (intact)

30 mm Al2O3 CoJet

50 mm Al2O3

80.54 (20.5)

72.77 (12.3)

71.75 (23.89)

Means not statistically different at p=0.05                     

Conclusion: Both repair methods yielded specimens with flexural strengths statistically equivalent to that of the control intact specimens.


1914 (17222)

The shear bond strength of light-curing composite resin to fiber-reinforced composite. T.M. LASTUMÄKI*, University of Turku, Finland, and P. VALLITTU, Univ. of Turku, Finland

Objective: This study examined the shear bond strength of visible light-curing composite resin (VCR) to novel glass fiber reinforced composite (FRC) with multiphase polymer matrix. Methods: Linear polymethyl methacrylate (PMMA) and dimethacrylate monomer preimpregnated unidirectional glass fiber reinforcement (everStick, Stick Tech Ltd.) was used as an adhesion substrate for low viscosity diacrylate laboratory composite resin (Sinfony Dentin, 3M-ESPE; SD) and restorative composite resin (Z100, 3M-ESPE). The test specimens were divided according to composite resin brand and the use of intermediate adhesive resin (IMR). IMRs used were either hydroxyethyl methacrylate (HEMA) containing Bis-GMA resin (3M Multipurpose Resin; MP), Bis-GMA-TEGDMA containing resin (Stick Resin; SR), or the controls were left without adhesive resin treatment. Inside of each three groups the test specimens were divided into four categories according to the water storage (2 weeks) or dry storage (2 weeks) of the FRC-substrates before adhering the composite on the FRC substrate. Thermocycling was used for aging the adhesive joint. There were five specimens in each of the testing categories. The shear bond strengths of the test specimens were measured and the results were analyzed with ANOVA. Results: The highest shear bond strength (23.9 +/- 3.7 MPa) was achieved with thermocycled FRC/IMR:MP/Z100 combination when the FRC substrate was water stored and adhesive joint was thermocycled. FRC/IMR:SR/SD combination resulted in 15.7+/-5.9 MPa after thermocycling. The poorest shear bond strength value (1.0 MPa) was obtained with thermocycled FRC/SD combination when the FRC substrate was water stored and thermocycled. Significant differences were found in mean values between the three groups (p<0.001). Conclusions: The linear PMMA phases of the multiphase matrix of FRC may have an influence on shear bond strength of FRC to VCR allowing formation of interpenetrating polymer networks (IPN) between the materials by dissolving capability of HEMA monomers on FRC surface.


1915 (19575)

Enamel treatment effect on leakage of pit and fissure sealants. L. LUPI-PEGURIER*, M. MULLER-BOLLA, M.F. BERTRAND, J.P. ROCCA, and M. BOLLA, Laboratory of Dental Biomaterials and Experimental Odontology, University of Nice-Sophia Antipolis, France

Objectives: The aim of this study was to assess the microleakage of a pit and fissure sealant on laser irradiated enamel with and without etching. Methods: Sixty non carious extracted third molars were cleaned without pumice. In each mesial half, the fissures were widened mechanically with a diamond bur and etched during 15s with a 35% phosphoric acid. Then, the teeth were randomly assigned to two groups of 30. In group 1, the distal halves were treated with laser alone. In group 2, they were treated with laser, followed by a 15s etching. The laser apparatus was pulsed Er:YAG laser (Opus 20, Sharplan, Israel), 1000 mJ/pulse and 10 pps in the presence of a constant air/water flow. Then, the sealant was applied (Ultraseal XT®, Ultradent Products, USA) corresponding to the manufacturer’s recommendations. The teeth were placed in distilled water for 48 hours and thermocycled (500 x, 5°C-55°C, dwell time 30s) prior to staining with 2% methylen blue. The samples were embedded into resin and sectioned in the middle of each half, in the bucco-lingual direction using a low-speed water cooled diamond saw. The extent of microleakage was measured with a digital-image analyser (Visilog 5.2®, Noesis Vision, Canada). The results were subjected to chi-square, ANOVA and paired samples t-test. Results: Laser showed the highest number of specimens with microleakage (63.3%) (p<0.02) and the highest mean of microleakage expressed in mm of dye penetration from the border of the sealant (0.76 vs 0.12 (bur), 0.17 (bur) and 0.18 (laser+etching) - p<0.01). No statistically significant difference in microleakage was noted between the two types of enamel preparation when etching was performed. Conclusions: Laser irradiation did not eliminate the need for etching the enamel surface before applying the sealant. Laser and bur preparations were equally successful in achieving low microleakage when used with etching.


1916 (6543)

Comparison of pretreatment methods of adhesively fixed FRC-molar crowns. M. SIKORA*, M. BEHR, M. ROSENTRITT, P. KARL, and G. HANDEL, University of Regensburg, Germany

Objectives: this study compared the influence of pretreatment methods of the inner crown surface on the fracture resistance and marginal adaptation of adhesively fixed FRC-molar crowns. Vectris/Targis crowns have an inner framework of glassfibers, which is cemented directly on the tooth, while other systems have a composite coping between the fiber-framework and the tooth-substance. Methods: after previous investigations the method most carefully and with the best bond strength (sandblasting A2O3; 50µm grain size, 2 bar, 20s, silane), the method using a composite coping and no pretreatment as control were chosen. Three groups of 8 Vectris/Targis molar crowns were constructed, two with exposed glassfibers on the inner surface, one with a composite coping. The adhesively on extracted human teeth cemented specimens were thermal-cycled and mechanically loaded (TCML: 6000x5°/55°; 1.2 x106x 50N, 1.66 Hz). The marginal analysis before and after TCML was evaluated and the fracture resistance was investigated using a Zwick universal testing machine. Results: after TCML the criteria "perfect margin" of the unpretreated group decreased significantly for the interface crown/cement and tooth/cement to less than 80%. The coping- and the pretreated group did not show a significant decrease of the marginal adaptation after aging. The fracture resistance was not statistically significant different between the three groups: (median/Q1/Q3) unpretreated: 1407N/1118N/1883N; sandblasting: 1755N/1647N/ 2247N; coping:1688N/1500N/1959N. Conclusions: the inner surface of FRC frameworks should be covered with a composite or the recommended pretreatment method should be carried out to achieve a high fracture strength and a reliable marginal adaptation.


1917 (7097)

Refrigerated Amalgambond-Plus/HPA MOD Amalgam Restorations: Fracture Strength at Six Months. M.S. HAGGE, University of the Pacific, San Francisco, CA, USA, and J.S. LINDEMUTH*, Travis Air Force Base, CA, USA

Objectives: The purpose of this study was to determine what effect prolonged water immersion and multiple sessions of thermocycling had on the fracture strength of extracted human third molars restored using refrigerated (3 °C) Amalgambond Plus with HPA (AB+/HPA) and Tytin amalgam. Methods: 3-mm deep MOD channels were prepared in one tooth from each of 19 contralateral pairs, with cavity width set at 1/3 of the buccolingual intercuspal distance. Following restoration, intact and restored teeth were thermocycled 1000 times from 5–55 °C with 30 second dwell times, then stored in 37 °C water for 6 months, with removal every 2 months for repeated thermocycling sessions. At the end of this period, the teeth were fractured in a universal testing machine at 2 mm min-1 in compression mode with a rounded probe engaged on triangular ridges. Fracture strengths were recorded in pounds and the data were analyzed using a paired t-test. Secondary effects of tooth location (maxillary versus mandibular) and tooth size on fracture strength were also examined using parametric and non-parametric analyses. Results: The paired t-test revealed that prepared/restored teeth (mean=654.09) were not statistically different in fracture strength than intact contralateral pairs (mean=676.94) (p >.05). Maxillary teeth had lower fracture strengths than mandibular teeth (p <.05). Tooth size had no effect on fracture strength (p >.05). Conclusions: Extracted third molars that had large MOD amalgam restorations bonded with refrigerated AB+/HPA had equivalent fracture strengths to their intact contralateral pairs following 6 months of water storage with 4 equidistant thermocycling sessions. AB+/HPA proved to be extremely durable under the severe conditions of this study. Performed under USAF Surgeon General-approved Clinical Investigation No. FDG20000041E


1918 (11112)

Adaptation of resin retained fiber posts cemented in extracted teeth. W.M. AHLSTRAND*, Private Practice, Stockholm, Sweden, and W.J. FINGER, University of Cologne, Germany

Objectives: To investigate the adaptation of 3 resin luting cements, retaining fiber posts in roots of extracted human canines. Methods: Resin fiber posts (Snowpost, Carbotech) were cemented in canine roots following endodontic treatment. The canal preparation was made two 2 days after root filling with gutta-percha using standard burs. In ten teeth each posts (1.5 mm Ø) were seated with 1. Post Cement HI-X/Bisco (HIX) and All-Bond 2/Bisco (AB2), 2. Bistite SC/Tokuyama (BIS), and 3. Panavia 21/Kuraray (PAN). The specimens were immersed in 23° C water for 24 hours. The roots were cut perpendicular to the post axis in the coronal, middle, and apical third of the canal preparation. The apical sites of the sections were polished with SiC (4000) and Al2O3 slurry prior to microscopic inspection. For each of the 90 sections the average resin cement thickness was determined from registration of the widths at 4 locations 90° apart. Maximum gap widths (MGW) were registered at the dentin and post sites. Presence of voids in the resin cement were recorded. Statistical analysis: One-way ANOVA, Kruskal-Wallis procedure, and post hoc testing at p<0.05. Results: Average cement thicknesses were 19.9, 23.3, and 16.1 µm (mean s.d. 9.6) for HIX, BIS, and PAN, respectively (BIS, HIX>HIX, PAN). No de-bonding was seen at the post interface. Average MGWs at dentin walls were HIX 1.7, BIS 0.7, and PAN 0.4 µm (HIX, BIS > BIS, PAN). Five PAN, 3 BIS and 0 HIX of the 10 specimens each were gap-free at all inspected sites. HIX showed more voids than BIS and PAN. Conclusions: No specimen showed consistently perfect root dentin sealing, whereas adaptation to the fiber post was perfect in all three groups. The adaptation to root dentin with BIS and PAN was significantly better than with the combined treatment AB2 and HIX.


1919 (7099)

Effect of Post Space Preparation Sequencing on Post Retention Strength. M.S. HAGGE*1, R.D.M. WONG1, and J.S. LINDEMUTH2, 1 University of the Pacific, San Francisco, CA, USA, 2 Travis Air Force Base, CA, USA

Objectives: This investigation examined what effect post-obturation sequencing had on retention of endodontic posts luted with a composite resin cement into canals previously obturated using a eugenol-based sealer. Methods: Sixty-four single rooted teeth were decoronated, filed, cleaned, and shaped with size 2-5 Gates Glidden drills and 0.12 taper rotary instrumentation. Teeth were then divided into 4 groups of 16 samples each. Group 1 was not obturated, and served as a control. The other 3 groups were obturated with warm gutta percha and a eugenol-based sealer. Post space preparation and concurrent post cementation were then completed at three different post-obturation intervals - Immediate (Group 2), 1 week (Group 3), and 4 weeks (Group 4). 10-mm deep post spaces were prepared with a size 6 Gates Glidden drill, and size 5 Paraposts were cemented with Panavia 21 OP. Following 48 hours of storage, samples were mounted in PVC pipe with acrylic, and the posts were removed in tensile mode using a universal testing machine at 1 mm min-1, with data recorded in kilograms. Results: Group 1 (Controls) mean=61.80, SD=16.21; Group 2 (Immediate) mean=38.70, SD=12.97; Group 3 (1 week) mean=43.15, SD=14.66; Group 4 (4 weeks) mean=18.82, SD=8.00. Using ANOVA and Bonferroni tests, Group 1 demonstrated significantly greater mean retention strength values (MRSV) than Groups 2 and 3 (p < 0.05), which in turn had significantly greater MRSV than Group 4 (p < 0.05). Conclusions: When posts are luted with resin cement into root canals previously obturated using a eugenol-based sealer, canal space preparation and post cementation should not be unnecessarily delayed; completion immediately or at 1 week is recommended. Performed under USAF Surgeon General-approved Clinical Investigation No. FDG20010027E


1920 (18266)

Artificial marginal secondary caries after use of self-etching and total etching bonding systems. C. PRATI*, A. SAPONARA TEUTONICO, L. BRESCHI, S. MARCHIONNI, L. SAVARINO, and G. MAZZOTTI, University of Bologna, Italy

Objectives: Enamel margin of restoration is a critical area where composite shrinkage stress and marginal gaps formations are responsible for secondary caries formation. Etching procedures may probably increase the porosity of enamel just close the margin of the restoration and increase the rate of demineralization. The purpose of this study was to evaluate the role of composite and fluoride releasing-materials to prevent demineralization produced by cariogenic solution. Methods: Twelve class V restorations were placed in vitro in human extracted third molars and immersed in demineralizing solution to simulate the formation of secondary caries and its effect on marginal integrity of composite restorations. Scotchbond 1+Z 250, SE Bond+APX and ABF+APX were used in the study. Each sample was stored in demineralizing solution (lactic acid, pH 4.5) at 37° for 4 days and changed three times a day. Microhardness evaluations were performed at 3 different sites of enamel: immediately close to the margin, approx. 1 mm from the margin and at 2 mm from the margin but in a protect (with nail varnish) area. A Leica VMHT 30A microindenter device working at 50 gr for 15 seconds and with indentations at 20 microns was used. Results: (mean ± SD; n=; ANOVA plus t test for paired data).

Material Groups (n=40)

Marginal  Enamel

Vickers degrees

Exposed Enamel

Vickers degrees

Protected Enamel

Vickers degrees

P

P*

P**

Scotchbond 1+Z 250

256.4             ±  83.7

352.9 ±  77.0

 

477.9 ±  126.7

0.002

<0.001

0.002

SE Bond+APX

109.1  ±  48.2

356.5  ±  57.7

420.6  ±   37.0

<0.001

<0.001

<0.001

ABF+APX

220.3  ±  41.1

311.7 ±  50.3

503.9 ±  106.4

<0.001

<0.001

<0.001

Conclusions: Enamel close to restoration margins frequently showed the highest rate of demineralization, as demonstrated by the lowest rate of microhardness number. The study demonstrated that exposed marginal enamel shows the highest rate of demineralization and for this reasons it may be rapidly affected by secondary caries formation. The use of total-etch technique did not increase the rate of marginal demineralization and the risk for secondary caries.


1921 (10674)

The quality of anterior veneers placed on composite restorations. Y.-H. CHUN*, H. PFEIFFER, C. RAFFELT, U. BLUNCK, and J.F. ROULET, Humboldt University of Berlin, Germany

Objective: Bonded ceramic veneers aesthetically restore anterior teeth. Often preexisting composite restorations must be dealt with. It is not clear if these restorations have an influence on the superimposed veneer. This study investigated the fracture resistance and the margin quality of such complex restorations. Methods: Each of the 60 intact, extracted, human, maxillary central incisors were filled with Herculite XRV Cl. III or IV composite fillings. The restored teeth were prepared to receive IPS-Empress veneers which were bonded with Syntac Variolink II using the Ecusit-CR, Artglass-liquid or no composite repair material (control) for the composite-composite bond. After water storage for 21 days, the teeth were ther-mocycled (TC) (2000x, 5-55°C). Based on replicas before and after TC, a quantitative margin analysis (SEM 200x) was done and the teeth were loaded up to fracture (40° in-clination, cross head speed 0.5mm/min). Fracture mode was analyzed in the SEM at 200x. Results: After TC, the composite repair materials yielded significantly better margin quality than the control (Kruskal-Wallis test). With Cl. IV restorations, Artglass liquid got the best margin quality (93% excellent margin) and yielded the least adhesive fractures at the composite-composite interface. Neither the composite restoration class nor the repair ma-terials had a significant influence on the fracture strength of the restored teeth being 780N–1000N (median). Conclusion: Based on these in vitro results, veneers can be bonded on preex-isting composite fillings; the use of composite repair materials is recommended.


1922 (15687)

Short-Term Shear Bond Strengths of Selected Indirect Orthodontic Resins. S.S. KHAJOTIA*, M.L. KHAKHRIA, R.S. NANDA, and M.G. DUNCANSON, Jr., University of Oklahoma College of Dentistry, Oklahoma City, USA

Objectives: to measure the immediate and developing shear bond strengths over a 60 minute time interval of three orthodontic resins used in the indirect bonding technique. Methods: Adhesive pre-coated brackets (Victory, 3M Unitek) were positioned on stone casts of bovine teeth (n=96 casts, 4 teeth per cast) using composite resin which was subsequently polymerized. The brackets were transferred to the teeth using custom-fabricated delivery trays, and were bonded with Custom I.Q. (CI), Sondhi Rapid-Set Indirect Bonding Adhesive (SR) or Transbond XT (TX) bonding resins. For the four teeth on each cast, debonding in shear was accomplished at 5 (immediate), 10, 30 and 60 minute intervals, respectively, using an Instron universal testing machine at a crosshead rate of 0.5 mm/min. The data were analyzed using two-way ANOVA and post hoc SNK tests (a=0.05). Results: Means and standard deviations for shear bond strengths by time were:

5 min.
10 min.
30 min.
60 min.
CI (MPa) 10.02 ± 5.64 A 10.88 ± 6.55 B 11.27 ± 6.87 B 10.57 ± 7.07 B
TX (MPa) 12.65 ± 3.87 A 13.05 ± 5.12 B/A 13.76 ± 5.03 B/A 14.29 ± 6.20 A
SR (MPa) 10.57 ± 5.64 A 15.21 ± 7.42 A 15.31 ± 6.89 A 15.48 ± 8.37 A

Analysis of bond strengths by resin showed no statistical differences among the test times except for SR, whose immediate (5 minute) bond strength value was statistically lower (p < 0.05) than the mean bond strengths at the other intervals. Conclusions: Mean bond strengths of the products immediately after bonding were not significantly different. Although the mean bond strength of SR increased significantly between the 5 and 10 minute tests, the mean values were comparable to TX at all test times. CI had a significantly lower bond strength at 60 minutes.


1923 (11206)

Problems related to posterior composite resin restorations among dental practitioners. B.A. LOOMANS*, N.J. OPDAM, J.J. ROETERS, M.A. VAN 'T HOF, and R.C. BURGERSDIJK, University of Nijmegen, Netherlands

Objectives: To investigate which problems dental practitioners experienced when placing posterior composite resin restorations. Furthermore, weather these problems are correlated to applied materials and techniques. Methods: A questionnaire was sent to a random sample of 750 Dutch dental practitioners. Data over the period 1999-2000 were collected about problems, which the practitioners experienced when placing posterior composite resin restorations and which materials and techniques they used. The data were statistically analysed using a t-test, Multiple Regression Analysis and Chi-Square test at p=0.05. Results: The response rate was 35% (n=252), representative for age and region. Most important problems experienced by the dental practitioners were postoperative sensitivity (61%) and achieving adequate approximal contacts (82%). Practitioners using specific self-etching primer adhesive systems experienced less problems associated to postoperative sensitivity (p=0.039). No correlation could be found between sensitivity and the use of other adhesive systems, placement of a lining or base and incremental placement of the composite (p>0.05). Difficulties in achieving proper approximal contacts were correlated to an earlier year of graduation of the dentists (p=0.035). The use of packable composites was correlated to more difficulties in achieving approximal contacts (p=0.043). Most dentists used traditional metal matrix systems (64%). Sectional matrix systems (15%) and separation rings (15%) were not commonly used. An earlier year of graduation was correlated to an increased use of hand instruments instead of an injection technique for composite application (p<0.001). Conclusions: Dental practitioners reported problems when placing posterior composite restorations associated to postoperative sensitivity and achieving approximal contacts.


1924 (14472)

Adhesion evaluation of a glass ionomer cement compared with different root canal sealers. A.L. NAJAR*, L.P. VANSAN, M.D. SOUSA NETO, and P.C. SAQUY, Ribeirão Preto University, Brazil

Objectives: The present study evaluated, in vitro, the adhesion of Ketac Endo, a glass ionomer sealer, with and without the presence of smear layer, in relation to two other root canal sealers: Grossman and Sealer 26. Methods: Sixty human molars were used and had their oclusal faces prepared until a plain dentin surface were obtained. The teeth were divided into three groups according to the tested cements. Each group was subdivided into two other groups of ten teeth each. Ten of them the smear layer was not removed. In the other ten, the smear layer was removed applying to the dentin surface EDTAC for 5 minutes. After this, the surfaces were washed for one minute and dried for 30 seconds. The powder/liquid relation and setting time of each sealer were established before hand. A universal testing machine, Instron 4444, was used for the adhesion test. Results: The results showed that the adhesion of Ketac Endo and Grossman sealers were, statistically similar and presented inferior values to Sealer 26 root canal sealer (p<0,01), independing of the smear layer being removed or not. Conclusions: The Sealer 26 presented, statistically, superior adhesion than the other tested sealers and the removal of smear layer increased even more its adhesion.


1925 (21634)

Evaluation of shear bond strength of two post systems with two core build-up materials. A.A. XIBLE*, A.L. VALLE, R.R. JESUS TAVAREZ, and S.C. KANO, Bauru Dental School, Universidade de São Paulo, Brazil

A zirconia and resin composite post and core build-up system was introduced in dentistry. Objectives:this study evaluated the shear bond strength between two core build-up materials (Tetric Ceram Resin Composite - Vivadent and IPS Empress Cosmo Glass Ceramic - Ivoclar) with two post systems (Tenax Stainless Steel - Whaledent and Cosmopost Zirconia Ceramic- Ivoclar dowels). Methods:three groups of 10 specimens each were made as follow: 1) zirconia posts and Glass Ceramic, 2) Zirconia posts and Composite Resin and 3) Stainless Steel posts and Composite Resin. For all groups, cores had the same dimensions involving the post surface. All specimens were positioned onto a metal base, which was mounted on a Universal Kratos Machine. Load was applied at the head of the posts until failure. Results:Mean and Standard Deviation bond strength (in MPa) were: for Group 1: 22,90 ( 0,22 ); group 2: 12,66 ( 1,86 ) and Group 3: 23,45 ( 1,42 ). ANOVA and Tukey tests were applied to the results (p<0,001), and there was no statistically significant difference between Group 1 and 3, but they were both statistically different from Group 2. Conclusions:the mechanical and chemical union between glass ceramic and zirconia posts were similar to that obtained between the head of the stainless steel posts and resin composite, which were statistically and numerical different from that obtained between zirconia posts and resin composite. This study was founded by CAPES - Brazil


1926 (14584)

Fracture strength of weakened human premolars restored with condensable resin with and without cusp coverage. R.F.L. MONDELLI*1, O. OLIVEIRA FILHO2, E.B. FRANCO1, and M.H. SILVA E SOUZA JÚNIOR1, 1 Bauru Dental SCHOOL - USP, BAURU, Brazil, 2 UNIVERSITY CAMILO CASTELO BRANCO, Campinas, Brazil

Endodontic posterior treated teeth can be fractured by the occlusal load because of removal of the pulp chamber's roof. Generally, this teeth are restored by indirect restoration, to protect the cusp. Objectives: to test the fracture strength of weakened human premolars restored with condensable resin with and without cusp coverage. Methods: thirty human maxillary premolars were divided into three groups: Group A (control), uncut teeth; Group B, wide MOD cavities prepared and the pulp chamber's roof removed. The teeth were restored with Surefil without cusp coverage; Group C, same as Group B plus 2.0 mm of cusp reduction and restored with condensable resin. The teeth were included in metal rings with self-curing acrylic resin and stored in water for 24 hrs. The restorations were refined, polished and further stored in water for 24 hrs before being subjected to a compressive axial load in an universal testing machine at 0.5 mm/min. Results: the mean fracture strength obtained was: Group A: 151.40 + 55.32 Kgf, Group B: 60.54 + 12.61 Kgf, Group C: 141.90 + 30.82 Kgf. The Group B was statistically significantly different (p < 0.05) from the others. The condensable resin restoration of weakened human premolars with cusp coverage significantly increased the fracture strength of the teeth as compared to teeth restored without cusp coverage. Conclusions: the results showed that cusp coverage with condensable resin might be an option for restoring weakened endodontically-treated teeth.


1927 (15550)

An Evaluation of Orthodontic Bracket Failure Utilizing Image Analysis Software. E.M. SACKS*, H.A. BROSNAN, M.N. JANAL, E.D. REKOW, and A.L. MAGANZINI, University of Medicine and Dentistry of New Jersey, Newark, USA

Various methods are used to measure the amounts of residual adhesive on tooth surfaces following debonding of orthodontic brackets. This study uses image analysis software as a technique to analyze and quantify residual adhesive on teeth experiencing bracket failure. The cement used in this experiment was a resin-reinforced glass ionomer adhesive (Fuji-Ortho LC). Objectives: To quantitatively evaluate the resin remaining on tooth surfaces following in-vivo orthodontic bracket failure using image analysis software. Methods: For six months, eighteen patients undergoing orthodontic treatment were monitored for bracket failures, forty-nine failures occurred in total. Quadrant alginate impressions were taken of each tooth with bracket failure. Each impression was sectioned to isolate the labial surface, poured with epoxy resin, and mounted to facilitate microscopic analysis. The outlines of eight bracket bases were scanned, saved and superimposed onto images of the teeth experiencing debonds. The surface areas of the eight bracket bases ranged from 9,899,313 square microns for an upper central incisor to 8,774,180 square microns for an upper lateral incisor. Surface areas with residual cement were calculated and divided by the total surface area of the bracket base. The measurements were categorized as anterior maxillary and mandibular and posterior maxillary and mandibular groups for analysis. Results: The residual resin in the bracket bases’ total surface area was 9.0% +/- 11.9% (maxillary anterior), 4.3% +/- 4.4% (maxillary posterior), 3.7% +/- 8.1% (mandibular anterior), and 3.2% +/- 7.4% (mandibular posterior). One-way analysis of variance determined that these numbers were not statistically different from one another. Conclusions: The bracket failures that occur when utilizing Fuji-Ortho LC are adhesive failures with little, or no, adhesive remaining on the tooth surface. The nature of bracket failure was consistent in maxillary and mandibular arches and anterior and posterior segments.


1928 (16049)

Evaluation of the oclusion loading in the integrity of restorations class II. P.E.G.D.A. CAMPOS*, UERJ , UNIVERSO, Rio de Janeiro, Brazil, and H.R. SAMPAIO, FOUERJ, Rio de Janeiro, Brazil

Objectives: The objective of this study was to evaluate the cervical microleakage in class II composite direct restorations , submitted or not to a occlusal loading . Methods: Twenty human molars were used with standardized cavities ("slot") proximal with terminations in enamel and cement. After being restored with condensable composite, they were divided in two groups, one that served as a control and another one that received 4.000 cycles of 150N for 1 min. The samples were submitted to a stain infiltration, and then were evaluated according to the penetration of the stain.

Results: In the group control it was found significant statistical differences (test Wilcoxon , p-value < 0,05) of the infiltration degree in enamel and cement. It was also found significant statistical difference in the group loading , with a p < 0,05 . When compared the groups control and loading there was significant statistical difference in level of the enamel (tests Mann-Whitney, p < 0,05), however it was not found significant difference in level of the cement (p> 0,05).

Conclusions: The authors could conclude that larger microleakage happens in cement when compared with the enamel. The occlusal loading acts increasing the decisively microleakage index .


1929 (17401)

In vitro evaluation of the reduction of the core diameter on the removal of radicular posts with ultrasound. E. ALFREDO, Â.D.B. GARRIDO*, C.B. SOUZA FILHO, A.M. CRUZ FILHO, and M.D. SOUSA NETO, Ribeirão Preto University, Brazil

Objectives: the objective of this study was to evaluate the reduction of the core diameter on the removal of radicular posts when associated to the ultrasound. Methods: twenty-four teeth were divided in two groups. Group I received cores with the same diameter of the radicular post, while Group II received cores 1mm larger than the posts. Zinc phosphate cement was used in all groups. Half of the samples of each group received ultrasonic energy for 8 minutes, 2 minutes for each face of the tooth. All samples were submitted to traction on an Instron machine (model 4444). Results: maximum strength values necessary to displace the posts from the roots were recorded and submitted to statistical analysis, revealing significant differences (p<0.05) between groups. Conclusions: the authors concluded that the mean strength necessary to displace the posts from the roots was reduced in 26% when ultrasound was applied. The reduction of the core diameter reduced the necessary strength to remove them in 24%, compared to larger cores.


1930 (17581)

Comparison of overhang formation with metal and light matrices. M. BADAWI*, H. LANG, M. R., and W.H.-M. RAAB, Heinrich-Heine-University, Duesseldorf, Germany

Objectives: In this study overhang formation at the proximal margins of composite and compomer restorations using metal or transparent matrices in class 2 cavities were compared. Methods: Sixty human, freshly extracted teeth were cleaned, standardized mod-cavities were prepared with their gingival margins located below the cemento-enamel junction (1-1.5 mm) and the teeth were divided in three groups a n=20. The cavities were restored using a compomer material (Dyract AP® / Prime&Bond® NT, Dentsply, Germany), a hybrid composite (Tetric® / Syntac® Classic, Vivadent, Liechtenstein) or a flowable composite (Tetric® flow / Syntac® Classic, Vivadent, Liechtenstein). The teeth were filled using an incremental technique (each layer: 1,5 mm) and the materials were light-cured. One part was filled using a metal matrix-system and the other part using a transparent matrix-system. The amount of overhang formed at the proximal margins was assessed by SEM and light microscopy. Results: The results showed that the mean values of overhang formation of hybrid composite, flowable composite and compomer restorations, which were filled using a metal matrix-system, were 41.26%, 30.60% and 36.48% respectively. While the mean values of overhang formation of hybrid composite, flowable composite and compomer, which were filled using a light matrix-system, were 76.53%, 58.20% and 61.41% respectively. The results indicate that overhang formation increases with the use of transparent matrices when compared to the use of metal matrices. Furthermore, the amount of overhang formed with standard hybrid composites is higher than that formed with flowable composites. Conclusion: The study shows that the type of matrix used with composite and compomer restorations is an important factor influencing overhang formation at the proximal margins.


1931 (17710)

Evaluation of diamond burs grinding and its influence on microleakage of composite restorations. A.B. BORGES*, B.N. CAVALCANTI, A.C.S. TAVARES, F.A. CLARO, M.A.M. ARAÚJO, and M.C. VALERA, UNESP - São José dos Campos, Brazil

Objective: The aim of this study was to evaluate the grinding of diamond burs used in cavity preparations and its influence on microleakage of composite restorations. Methods: 50 bovine teeth and 10 diamond burs (KG Sorensen) were used. 20 teeth were just used for the bur grinding simulation and were then discharged. The remaining 30 teeth were divided into three groups (n=10): Group 1- preparations made with new burs (control); Group II- burs used after 4 preparations (5th preparation); Group III- burs used after 9 preparations (10th preparation). The cavities were restored with Prime & Bond 2.1/TPH (Dentsply). The teeth were thermocycled (500 cycles – 5oC and 55oC), stored in 0.2% Rodhamin dye for 12h and sectioned buccal-lingually. The specimens were evaluated in stereomicroscope for microleakage. The diamond burs were analyzed in stereomicroscope before they were used and after the 1st, 5th and 10th preparations to evaluate the grinding. Results: The microleakage data were subjected to Kruskal-Wallis test (5%) and showed no statistical significance among the groups. The diamond burs grinding data were subjected to Kruskal-Wallis test and multiple comparison Dunn’s Method (5%). Statistical significant differences were found among burs never used and burs after 5th and 10th preparations. Conclusion: Although the diamond burs exhibited a discrete grinding, there was no influence on microleakage.


1932 (18938)

Cytotoxic Effect of One-step Adhesive Systems. M. KAGA*, A. EDAHIRO, M. SAKURAI, T. OOKA, M. NODA, and H. OGUCHI, Hokkaido University, Sapporo, Japan

The toxicity and pulpal irritation of adhesives is in dispute. Objectives: new one-step adhesive systems containing etching, priming, and bonding agents in a single bottle have been developed. The aim of this study was to investigate the cytotoxic effect of eluates from cured one step adhesives. Methods: disks (6 mm dia. ~ 1 mm thick) of One-up Bond F (OB, Tokuyama), Xeno CF Bond (XC, Sankin /Deggusa), and Reactomer Bond (RB, Shofu) were light-cured for 40s. Rat pulpal cells (Kasugai et. al.,1988) were seeded in 12-well plates and grown until confluent sheaths in D-MEM supplemented with 10% FCS. To keep specimens away from cells, the disk specimen was held in the medium with cell culture insert (Falcon, 3182). A glass disk was used as a control. The cellular viability was assessed by MTT assay after 24 h incubation, and calculated as a percentage of control (n=4). Results: the viability showed control (100}36.9)* , RB (56.5}7.4)*, OP (57.6}6.5)* , XC (22.9} 16.8)** (no significant differences in the same symbols, ANOVA, Tukey, p < 0.05). Conclusion: the results suggest that clinical exposure to the uncured dentin bonding resin should be minimized.


1933 (19098)

Post systems: compressive strength of roots prepared at 2/3 and 1/2 length restored with post systems. P.A. BURMANN*1, P.E.C. CARDOSO2, J.F.F. SANTOS2, and L.F. SOARES1, 1 Federal University of Santa Maria, Brazil, 2 University of São Paulo, Brazil

Objectives: Evaluate the mechanical resistance of roots restored with pre fabricated posts. Materials and Methods: Forty sounds upper human central incisors, had the crown removed using a diamond disc (Labcut, USA) and the roots were endodontically treated (guta percha points + Sealer 26 – Caulk-Dentsply, USA). After 24 hours the root canals were prepared using low rotation, going 2/3 or 1/2 down the depth of the root, and divided into 4 groups (n=10). Group A: 10 roots were prepared on 2/3 of the depth for the cementation of Unimetric posts (Maillefer-Dentsply, USA) [UNI] using Clearfil Liner Bond 2V + Panavia F (Kuraray Co., Japan), according to manufacture’s instructions; Group B: 10 roots were prepared 1/2 deep into the root canal for the cementation of [UNI] posts with the same adhesive system as group A; Group C: 10 roots were prepared on 2/3 of the depth for the cementation of the Aesthetic Post [AES] using All Bond 2 + Post Cement Hi-X (Bisco Inc., USA); Group D: 10 roots were prepared 1/2 deep into the root canal for the cementation of [AES] using the same adhesive system as Group C. 3 mm of the posts were left out of the root canal, on the cervical portion, to allow the fixation of the core restoration with composite resin (Z250 – 3M-ESPE, USA), simulating preparation for a crown. The specimens underwent compression at 45º on an universal testing machine, at a speed of 0.5 mm/min, until fracture. Results: The mean values of load obtained at fracture (Group A=93.4 Kgf, Group B=88.4 Kgf, Group C=95.7 Kgf, Group D=96,3 Kgf) were statiscally tested using the ANOVA two-way test. All groups showed statiscally similar result (p>0.05). Conclusion: the different preparation depths of the root canals did not influence the results of the strength tests.


1934 (19154)

Post systems: adhesive strength at different root levels. J.F.F. SANTOS1, P.A. BURMANN*2, P.E.C. CARDOSO1, and C.C.S. LOUREIRO1, 1 University of São Paulo, Brazil, 2 Federal University of Santa Maria, Brazil

Objectives: The purpose of this study was to evaluate the bond strength of pre fabricated post/adhesive system to the radicular dentin on its cervical [C] and apical [A] portion. Materials and Method: Ten upper human central incisors, caries free, had the crown removed and the roots were endodontically treated (guta percha points + sealer 26 – Caulk-Dentsply, USA). After 24 hours the canals were prepared on low rotation with a depth of 10 mm, for the pre fabricated Unimetric posts (Maillefer-Dentsply, USA) to be placed. The posts were blasted with aluminum oxide (100 µm – micro etcher – Danville, USA) and cemented with Clearfil liner bond 2V + Panavia F (Kuraray Co., Japan), according to manufacturer’s instructions. After 24 hours the roots were cut transversally, originating slices 2 mm wide. 10 slices of the [C] portion and 10 slices of the [A] portion were tested by the push method, on an universal testing machine (0.5 mm/min). Results: the bond strength at the [C] portion was 18 MPa and at the [A] portion it was 8.3 MPa. The statistical analyses was done using one-way ANOVA, and showed difference among the 2 groups (p<0.05). Conclusions: The bond strength obtained on the apical portion was lower than the bond strength obtained for the cervical portion of the root canals.


1935 (19476)

Depth of cure and hardness of various composites using a new LED curing light. C.A. MUNOZ, N. JESSOP, G. BERNAL*, and J.R. DUNN, Loma Linda University, CA, USA

Objective: A new system that uses a light emitting diode (LED), which produces a focused light source, less heat, and are said to be portable has been introduced. This study compared the polymerization hardness of a new LED light-curing lamp to a conventional halogen curing light (501, Demetron/Kerr). Methods: Z 250 (3M/ESPE), Esthetic-X (L.D. Caulk/Dentsply) and Point 4 (Kerr) were evaluated using shades B1 and C4. A specially fabricated specimen holder 6 mm in depth and 6 mm in diameter was placed on a glass slab, composite condensed and polymerized for 40 sec using a new LED curing light and the conventional. Immediate Knoop hardness of the top of the composite was measured with a Leco M-400 H1 hardness tester. Five locations were measured for each specimen and surface. The specimens were then sectioned, lightly polished and hardness measurements were made at 0.5, 2, 4, and 6 mm. Results: Overall Halogen light produced a slightly higher Knoop Hardness numbers that the LED light. An exception was Esthet-X C4, in which the LED had higher values than the halogen light. With the exception of Point 4 C4, all materials had a KHN of 50 or above at 2.00 mm of depth. Point 4 C4 had the lowest polymerization depth that was measurable, which was at 2 mm. Conclusions: (1) The data indicates that the LED curing light (375 mW/cm2), with less than half the light output than the halogen light (800mW/cm2), is able to produce acceptable curing depths for all the composites. (2) Z250 B1 and C4 had the highest Knoop Hardness number, while Point 4 B1 and C4 had the lowest KHN. (3) All the light shades had the greatest polymerization depth measured at 5 mm of depth.


1936 (15317)

Influence of surface roughness on cone crack formation in glass-ceramic. T. YAMAMOTO*, R. NISHIURA, T. SAMPEI, and A. KOHNO, Tsurumi University School of Dental Medicine, Yokohama, Japan

Objectives: The objective of this study was to evaluate the influence of roughness in compressive surface on cone crack formation in a mica-based glass-ceramic, OCC (Olympus Optical Co., Tokyo, Japan) referring to a study of Tsai et al. (Int J Prosthodont 18:27-32, 1998). Methods: Twenty-five OCC disks sized 1.5-mm-thick X 14-mm-diameter were fabricated, and a surface of each disk was ground through 180- (Group 1: 0.904 ƒÊm Ra), 220- (Group 2: 0.486 ƒÊm Ra), 400- (Group 3: 0.188 ƒÊm Ra), 1200-grit SiC abrasive (Group 4: 0.102 ƒÊm Ra), or 1 ƒÊm diamond paste (Group 5: 0.050 ƒÊm Ra). Resin core disks (Clearfil DC Core, Kuraray, Osaka, Japan) sized 2.0-mm-thick X 15-mm-diameter were bonded to the unground surfaces of the ceramic disks using a resin cement (Panavia F, Kuraray, Osaka, Japan). The bonded specimens were loaded at the center of the ceramic with a 3-mm-diameter pin at a cross-head speed of 0.1 mm/min until cone crack was produced. Resulting data were statistically analyzed by one-way ANOVA and Fisher's PLSD at p < 0.05. Results: Mean loads and standard deviations at the cone crack formation were: Group 1; 2826 } 765 N, Group 2; 2530 } 604 N, Group 3; 2211 } 774 N, Group 4; 2266 } 504 N, and Group 5; 2862 } 780 N. There were no significant differences among the groups. Conclusions: The surface roughness in the compressive surface had no influence on the cone crack formation in the mica-based glass-ceramic.


1937 (15691)

Effect of Deposition Conditions on the Strength of a Sputter-Coated Dental Ceramic. D.E. RUDDELL*, B.R. STONER, and J.Y. THOMPSON, University of North Carolina Chapel Hill, USA

Objectives: Previous work has shown that the apparent fracture strength of dental ceramics can be increased by the application of sputter-deposited thin-film coatings. To be clinically useful, the coating needs to aesthetically acceptable, that is, it should not alter the aesthetic properties of the underlying material. Alumina is a relatively tough, ceramic, which can be fabricated to be translucent, that could be used for this application. The properties of alumina thin-films are greatly influenced by the conditions under which they are deposited. The purpose of this study was to investigate the effect of deposition parameters (temperature and bias voltage) on the flexural strength of alumina bars modified with sputter-deposited alumina thin-films. Methods: Alumina bars (2 x 2 x 15mm, Ferroceramic Grinding, Inc.) were polished through 1200-grit SiC abrasive, air abraded, and coated with a 5 mm thick alumina film using RF-magnetron sputtering (CVC Products, SC-400). The sputtering target was 99.99% alumina (Target Materials Incorporated.) Deposition temperature was either 400 or 600° C. A DC bias of –50V was applied to the substrate holder in three cases. The bars were fractured in 3-point bending (Instron 4411), and examined under SEM. Crystal structure was determined by XRD. Data was analyzed by ANOVA with post-hoc Tukey's test. Results: The mean flexure strength for each deposition condition (N=10 bars/group) was as follows: No coating, 345 MPa; 400° C, 359 MPa; 600° C, 354 MPa; 400° C with bias, 364 MPa; 600° C with bias, 353 MPa; Bias only (no coating), 366 MPa. X-ray Diffraction showed that the films deposited with a bias were crystalline, while those deposited without a bias were amorphous. Conclusions: Statistical analysis indicated that the flexural strength did not vary significantly among the test groups for the significance level chosen (P<0.05). This work was supported by NIH 5R01DE013511-01.


1938 (17111)

Relationship between the mechanical properties and crystalline structure of the submicronic Al2O3-ZrO2 ceramics. S. KOMATSU*1, H. AOYAGI1, K. KAKUTA1, H. OGURA1, Y. HATA1, and Q.B. WAN2, 1 The Nippon Dental University, School of Dentistry at Niigata, Japan, 2 West China University of Medical Sciences, Chengdu, China

Objectives: We have evaluated the mechanical properties of the submicronic Al 2O 3 - ZrO 2 ceramics (Al 2O 3: A and ZrO 2: Z) consisting of five different contents of these two materials with 20% intervals as regarded to Vicker's hardness, flexural strength and sintering shrinkage. The specimen has been prepared using slip cast method to evaluate (J Dent Res 79: 0250,558,2001). Aim of this study was to investigate the relationship between the mechanical properties and the crystalline structure of this ceramics. Methods: The fractured surface of each ceramics was observed and measured the size of crystalline particle under SEM. The element distribution of the ceramics was analyzed with the Element Map Method using an Electron Probe Microanalyze (JXA-8900, JOEL) and the chemical shift of each elements were determined by Electron Spectroscopy for Chemical Analysis (JPS-9000, JEOL). Results: The crystalline structure of these ceramics showed that (Z) crystalline particle surrounded (A) crystalline particle and both crystalline particle did not diffuse each other. (Z) crystalline particle size was almost the same regardless of the (A)-(Z) content, whereas (A) crystalline particle size decreased with the increase in (Z) content. The crack propagation of (A) crystalline particle was observed at 0 and 20% Z content and they showed lower flexural strength. The interfacial crack growth was induced at higher content of (Z) and these contents of crack propagation showed higher flexural strength. Conclusions: The Yttria-stabilized Zirconia could toughen the fracture strength of Alumina ceramics and this mechanism can be basically related to their crystalline structures. Supported by Kyocera Company. skomatsu@ngt.ndu.ac.jp


1939 (17250)

Improved Contraction of Porcelain Inlays by CIP Method. C. KAWAMOTO*, J. KONISHI, F. WATARI, and H. SANO, Hokkaido University, Sapporo, Japan

Objectives: Previous study reported a new approach for the fabrication of porcelain inlays using cold isostatic press (CIP) method. Using this method, uniform quality of porcelain inlays could be simply achieved and mechanical properties were compatible to the conventional method. However, firing contraction was still not satisfactory. This study investigated the effect of experimental particles on contraction and mechanical properties of porcelain inlays processed by CIP methods. Methods: One commercial crushed porcelain powder (G-CERA COSMOTECH II, cosmo) and three experimental porcelain powder: spherical porcelain powder (Exp.1), spherical porcelain powder with polyacrylic acid binder (Exp.2), spherical porcelain powder with gum arabic as a binder (Exp.3) were used. After porcelain powder was filled in excess into refractory models and rubber sealed, press molding was conducted by the CIP apparatus at pressures of 200MPa and then fired at 970ºC. Linear contraction, Vickers hardness (Hv) and bi-axial flexural strength were measured. Data were analyzed by Kruskal Wallis and Mann-Whitney tests (p<0.05). Results: Identical superscripts show groups with no significant differences in the table.

The contractions of three spherical porcelain powders were lower than cosmo (crushed powder). Especially, addition of binder achieved less contraction, whereas, it resulted in lower flexural strength compared with cosmo. However, obtained values of spherical powder were acceptable for clinical use. Conclusion: The experimental spherical porcelain powders reduced contraction of fired porcelain inlays therefore, those were suitable for the CIP method.  


1940 (18223)

In-vitro Wear Assessment of Feldspathic and Low-Fusing Porcelain vs. Enamel. M.A. LATTA, J.L. SHEETS*, and B. SIMISTER, Creighton University School of Dentistry, Omaha, NE, USA

The compatibility of enamel opposed by porcelain is of concern to the restorative dentist. Newer low-fusing ceramics may have the potential for less enamel attrition in occlusal function. Objectives: The purpose of this in vitro study was to compare the wear of a conventional feldspatic porcelain and a low-fusing porcelain against human enamel. Methods: Eight Porcelain specimens each were made from a feldspathic porcelain (Ceramco II) and a low-fusing porcelain (Finesse). Samples were polished to a smooth surface using 600 grit sandpaper. Enamel specimens were contoured using a diamond tool into standardized conical styli. Samples were subjected to wear in a Leinfelder wear simulator. The enamel styli were mounted in spring-loaded pistons calibrated to deliver a force of 79 N to the porcelain surface using a counter-rotation motion. Pre-test enamel and porcelain surfaces were profiled using a MTS 3-D profilometer. Samples were subjected to 400,000 wear cycles and re-profiled. Volume loss was calculated for each porcelain surface and enamel stylus. Student's T-Test was used for statistical comparison. Results: Mean volume loss (mm3) for the flat porcelain specimens: Ceramco II- 0.0083 ± 0.0068, Finesse 0.0080 ± 0.0039. Volume loss for the enamel antagainsts: Ceramco II- 0.0338 ± 0.0179, Finesse-0.0104 ± 0.0037). Material loss of the ceramic specimens was not significantly different (p>0.05) but enamel loss opposing Ceramco II was higher than Finesse (p<0.05). After the trials, visual analysis of the surface of the Ceramco II porcelain appeared more porous when compared with the worn Finesse surface which remained smoother. Conclusions: There was significantly greater wear of enamel against the feldspathic porcelain than against the low-fusing porcelain material. Further work is needed to determine the clinical correlation of this in vitro wear model.


1941 (18225)

Maximum load to fracture of resin cement from sintered ceramic materials. A. MACEDO*, J. DELGADO, M. SIERRAALTA, and M. RAZZOOG, The University of Michigan, Ann Arbor, USA

Objective: Aluminum oxide cannot be altered by acid etching yet it is claimed that resin cements may be bonded to the surface. Previous studies have looked at the shear bond strength of only a few of the popular cements. This study attempted to evaluate the maximum load to fracture of a resin cement commonly used for all ceramic crowns to densely sintered aluminum oxide and a experimental sintered Zirconia Y-TZP.

Method: Twenty specimens of densely sintered aluminum oxide and 5 of a sintered Zirconia Y-TZP (Procera„¥) were fabricated so that one side of the sample replicated the pressed portion of the coping. The pressed surface was positioned so that the cement rod was at a right angle to the force application. Aluminum oxide samples were etched, conditioned and bonding agent applied according to manufacturer specifications. Den-Mat, Ultra-Bond Quik was dispensed using a standard mold to develop a consistent bonding area of 2.379 mm for testing. The cement was light cured for 25 seconds and stored for 24 hours. A shear load was applied at the junction of the ceramic samples and cement with a knife-edge rod at a crosshead speed of 0.5mm/min in a Universal testing machine.

Results: The mean maximum load to fracture the resin cement from the densely sintered aluminum oxide pressed surface was 31.57 N. The mean maximum load to fracture the resin cement from the experimental sintered Zirconia Y-TZP was 25.96N. Data from the two samples were analyzed using a unilateral t-test with no significant difference at P=0.05.

Conclusion: There was no statistically significant difference between the load fracture of the resin cement from the densely sintered aluminum oxide or the experimental sintered Zirconia Y-TZP.

Supported by NobelBiocare/ University of Michigan Center for Excellence


1942 (18342)

Cross-section microhardness analysis of alumina ceramic after glass infiltration. M.K. ITINOCHE*, M.A.J. ARAUJO, E. MIYASHITA, A.A. CATRO FILHO, D.K. OYAFUSO, and M.A. BOTTINO, São José dos Campos University, UNESP - School of Dentistry, São Paulo, Brazil

Objectives: This study evaluated the transversal-section microhardness of structures made of In-Ceram Alumina (Vita) on two different sites. Methods: Ten metallic structures were milled (3X4X15mm). They were moulded by a duplicator silicon and removed from the mould. The left spaces were filled up with In-Ceram Alumina oxide mass, which were dehydrated and removed to be baked onto a platinum plate in a especial oven. The specimens were infiltered with glass and burnt in a special oven according to manufacture's instructions .For all of them a cross section was done and Vickers hardness test was realized in and out of the center. Differences in colour were observed and they suggested absence of glass infiltration. Results: Data was submitted to t-Student (alfa=5%) statistic analysis and the results showed significant statistics differences between the center and out of that with averages of 1481,4 and 1613,1 HV, respectively. Conclusions: The authors concluded that the glass infiltration didn’t reach efficiently the specimen’s center, which provide less hardness comparing to the periphery of the specimens.(FAPESP: Process-99/10957-1).


1943 (18757)

The Mechanical Properties of Three Pressable All-ceramic Dental Materials. M. ALBAKRY*, M. GUAZZATO, and M. SWAIN, The University of Sydney, Australia

Objectives: The aim of this study was to appraise the mechanical properties (flexural strength, fracture toughness, hardness, Elastic modulus, and Poisson's ratio) of three different pressable dental materials: Empress 1 (Em1), Empress 2 (Em2) and a new experimental framework glass-ceramic (EC).

Methods: Forty disc specimens and three bars per material were prepared. Discs were used to determine the biaxial flexure strength. Fracture toughness was measured with two different techniques: Indentation strength (IS) and Indentation fracture (IF). Elastic modulus and Poisson's ratio were measured with the bars. X-ray diffraction was also performed to distinguish the crystalline phases.

Results: Mean strengths were: Em1 140.3 (SD 25.7), Em2 331 (SD 39.7) and EC 356 (SD 44.4) MPa. Fracture toughness using the (IS) technique were: Em1 0.85 (SD 0.12), Em2 1.60 (SD 0.2), EC 1.54 (SD 0.18) MPa · m1/2. The IF technique generated orthogonal cracks for Em2 and EC with different lengths whether perpendicular or parallel to the lithium disilicate elongated crystals. Thus, two values were reported: Em2 {1.5 (SD 0.19), 1.16 (SD 0.2)} and EC {1.67 (SD 0.26), 1.15 (SD 0.15)} MPa · m1/2. Em1 IF result was (1.37 SD 0.31) MPa · m1/2.

Conclusion: There was no statistical difference between Em2 and EC strength and toughness p³0.05. Both Em2 and EC were significantly stronger, and tougher using the IS technique, than Em1 p£0.01. Utilizing the IF technique, EC was tougher than Em1 only for cracks perpendicular to the lithium disilicate crystals p£0.05.


1944 (20177)

Crystal size and their distribution in hot-pressed Empress ceramics. N.-Z. ZHANG*, and K.J. ANUSAVICE, University of Florida, Gainesville, USA

Hot-pressed Empress dental ceramics exhibit a wide variability in fracture toughness (0.9 - 3.4 MPa·m1/2) (Anusavice et al, 2001). These values are associated with differences in crystal phases, size, and crystal size distribution in the core ceramics of IPS Empress (E1C), Empress 2 (E2C) and an experimental ceramic (EXC) (Ivoclar AG). The crystal distribution coefficient (P) has been used to describe the inhomogeneity of microstructure for fluorcanasite glass-ceramics (Zhang & Anusavice, 2001). However, the relationship between crystal size and crystal distribution coefficient (P) for these ceramics has not been previously reported. Objective: To test the hypothesis that the uniformity of crystal distribution in these ceramics is increased by a decrease in crystal size and a decrease in the crystal distribution coefficient (P). Methods: Three groups of 6 specimens each were prepared according to the manufacturer’s instructions: (1) E1C; (2) E2C; and (3) EXC. The polished cross-sections of bars were carbon coated and analyzed using scanning electron microscopy. Elemental analyses were performed at several regions using energy dispersive spectroscopy (EDS). X-ray diffraction analysis was performed for phase identification. Results: The mean crystal size, 0.73 ± 0.27 µm2 of EXC was significantly lower (p £ 0.05) than that (1.91 ± 1.68 µ m2) of E2C. The mean crystal distribution coefficient (P) was 1.09 for EXC, 1.40 for E1C, and 1.75 for E2C. A crystal distribution coefficient (P) of 1 indicates a perfectly homogeneous structure and a value much greater than 1 is associated with an inhomogeneous crystal distribution. X-ray and SEM analysis revealed the presence of leucite (KAlSi2O6) crystals in E1C, lithium disilicate (Li2Si2O5) crystals in E2C, and EXC. Conclusion: The smaller crystal size and crystal distribution coefficient (1.09) of EXC supports a more homogeneous microstructure compared with those of E1C and E2C.


1945 (20337)

Bilayered ceramic spheres:Useful test for thermal incompatibility?. A.A. BARRETT*1, K.J. ANUSAVICE1, and P.H. DEHOFF2, 1 University of Florida, Gainesville, USA, 2 University of North Carolina Charlotte, USA

Thermal incompatibility stresses may result in crack initiation and/or propagation within ceramic/ceramic and metal/ceramic prostheses.  Comparison of thermal contraction or expansion coefficients is not a reliable indicator of incompatibility failure.   Objective: This in vitro study tested the use of bilayered ceramic spheres as an indicator of thermal incompatibility stresses of dental ceramics with matched and mismatched coefficients of thermal contraction.  Methods: Empress 2 core ceramic (E2C) and an experimental lithia-based core ceramic (EXC) were hot pressed per the manufacturer's recommendation.  Groups of six 6.3mm-dia. cores were veneered with a 1.8mm-thick layer of Empress 2 veneer ceramic (E2V), an experimental veneer ceramic (EXV), and Vita body porcelain (VV) and fired once.  Results: The respective a500-25°C values for E2C and EXC ceramics are 10.2 and 10.4 ppm/oC, respectively.  The respective a500-25°C for E2V, EXV, and VV ceramics are 9.91, 9.96, and 12.8 ppm/oC, respectively.  Thermal compatibility was determined by the absence or presence of cracks in the veneer of each specimen.  Cracks were determined visually using fiberoptic transillumination.  Approximately 72h after cooling to room temperature, cracks were detected as follows: E2C/E2V (16%); E2C/EXV (0%); E2C/VV (100%) with average alpha (a500-25°C) differences (ac–av) of +0.27, +0.22, and -2.62 ppm/oC, respectively.  The experimental core ceramic failures were: EXC/E2V (0%); EXC/EXV (0%); EXC/VV (100%) with average alpha (a500-25°C) differences (ac–av) of +0.47, +0.42, and -2.42 ppm/oC, respectively.  Viscoelastic finite element stress calculations were generally in agreement with the experimental results in that low transient tensile stresses (<10MPa) and low residual tensile stresses (<5MPa) in veneer at the interface were associated with the compatible systems and high transient and residual stresses (>79MPa) developed in the incompatible systems. Conclusion: The results of this study suggest that the sphere can be used as a thermal incompatibility test model for bilayered ceramic structures.

This study was supported by NIH-NIDCR Grant DE06672.

 

 


1946 (20810)

Cyclic Fatigue Behavior of Baria-Silicate Glass-Ceramics. K. SUPUTTAMONGKOL*, K.J. ANUSAVICE, and J.J. MECHOLSKY, University of Florida, Gainesville, USA

Objective: To test the hypothesis that the mean strength of baria-silicate glass-ceramic model materials subjected to cyclic loading is rapidly degraded because of the creation of a new flaw population. Methods: Baria-silicate glass bars were heat-treated at a specified temperature and time to produce glass-ceramics with two aspect ratios (3.6/1 and 8/1). Bar-shaped glass and glass-ceramic specimens were prepared and subjected to cyclic loading from 0 to 100,000 cycles at a maximum load of 200 N and a frequency of 3 Hz. A 4.8 mm-diameter steel ball was used to apply the load at the center of each bar. The cyclic fatigue test was performed in air at room temperature and in deionized water to determine the effect of environment on crack propagation under fatigue loading conditions. A four-point bending test was used to determine strength degradation of glass and glass-ceramic specimens subjected to repeated loading. Results: The mean flexural strength of baria-silicate glass decreased significantly from 94 ± 22 MPa to 46 ± 9 MPa after 100,000 cycles. The mean flexural strength of glass-ceramic with the highest aspect ratio decreased from 246 ± 7 MPa to 83 ± 25 MPa (P < 0.05). Deionized water caused the greatest decrease in the glass-ceramics with the highest aspect ratio. Failure of baria-silicate glass specimens initiated from a cone-crack that developed during the cyclic loading test. For baria-silicate glass-ceramic specimens with the highest aspect ratio, failure initiated from surface cracks caused by polishing. Conclusions: (1) The strength of baria silicate glass-ceramics is degraded by cyclic loading. (2) Control of microstructure by heat treatment can greatly affect the strength and toughness of glass-ceramics during cyclic fatigue testing. Supported by NIH-NIDCR Grant DE06672 and The Royal Thai Government


1947 (21072)

Flexural Strength of a New Ceramic Core Material. R.P. RUSIN, R.F. MURPHY, and J.C. ROLF*, 3M ESPE Dental Products, St. Paul, MN, USA

A new ceramic core material for CAD/CAM is under development for use in all-ceramic restorations. Surface flaws from machining or finishing can weaken materials, particularly ceramics. Thus, it is critical to prepare these materials for strength measurement in the same way as they are used clinically. The objective of this study was to compare the flexural strength of a new CAD/CAM milled core material before and after firing. 2.5x1.5x12 mm bars were milled on a Sirona™ CEREC™ 2 system from the new material. Group A was tested as-milled; group B was fired once at 950C/1 min; group C was fired 3x at 950C/1 min. All samples were broken in a 3-point bending fixture. The data were analyzed via one-way ANOVA and compared with Tukey’s T-test (p<0.05). The flexural strengths were: group A 329±20 MPa; group B 349±22 MPa; group C 342±18 MPa. The as-milled and fired samples were statistically equivalent. jcrolf@mmm.com


1948 (21397)

Impact Stress propagation in Diopside Glass-Ceramic Bridge. K. MURASE*, Kinki University, Higashihirosima, Japan, S. TSUTSUMI, Kyoto University, Japan, and M. FUKUMA, Osaka Dental Institute College, Japan

Objectives: In this study, the distribution patterns on impact stress propagation in glass-ceramic bridges were investigated to evaluate the clinical applicability of those bridges by the high precision three-dimensional finite element analyses. Methods: The finite element models of anterior three-unit bridge were prepared in a typical clinical design measured by the laser scanning system. The bridges were composed of glass-ceramic DIOPSIDE (CaO-MgO-2SiO2) that has high strength (350Mpa) and toughness (2.7MPaEm1/2). An impact force of 300N was applied to the pontic. The force compressed the tip of the pontic at first, and then the loading point was moved to the central area of that. Two types of dental cements (Young' s modulus: 8GPa and 2GPa) were used with 30micron m thickness. As the design parameter the size of connecting area between pontic and abutments were selected and changed. The computations were performed from 0 to 100ms after impact. Results: The simulation results showed the concentrated impact force rose over 30MPa of maximum tensile stresses in the cervical neck area and the central of the dental cement layer which are about 10 times higher than those under the static loading condition. The peak of impact tensile stresses increased according to the decrease of the connecting area of the bridge. Especially, the tensile stresses in cervical area increased 3 times up to 120MPa when the connecting area was reduced to 50%. Conclusions: These results revealed that the impact forces make a quite serious stress distribution compared with static loadings, and the consideration for the shape design at the connecting area of the bridge and that for the mechanical properties of dental cements are important against oblique impact loading.


1949 (21768)

Flexural resistance of glass-infiltrated porcelain after repairing. E. MIYASHITA*, M.K. ITINOCHE, L.G. VAZ, M.A. BOTTINO, and M.A.J. ARAUJO, São José dos Campos University, UNESP - School of Dentistry, São Paulo, Brazil

The Objectives: of this study was to compare de flexural resistance of In-Ceram Alumina and In-Ceram Zirconia, glass-infiltrated porcelains used for substructure for all-ceramic three unit bridge. Materials and Methods: four groups of ten specimens each were obtained, measuring 15mm X 3mm X 4mm. (G1) In-Ceram Alumina sintering according manufacturer's recommendations process at 1120°C for 2 hours, and infiltrated with melting glass at 1100°C for 2 hours; (G2) the specimens of In-Ceram Alumina after sintering process, are cutted in the middle with a diamond disc and repaired with the alumina porcelain and repeated the sintering process and realize the infiltration glass firing. (G3) In-Ceram Zirconia are sintering with two cicles of firing according manufacturer's recommendations process the first at 1120°C for 2 hours and another at 1180°C for 2 hours, and infiltrated with melting glass at 1140°C for 2 hours (G4) the specimens of In-Ceram Zirconia after sintering process, are separated in the middle with a diamond disc and repaired with the zirconia porcelain and repeated the sintering process and realize the infiltration glass firing. The four groups were submitted a three-point bend test in an universal test machine (MTS) at a speed of 0,75mm/min., loaded on the narrow surface. Data obtained were submitted to two way analysis of variance. The Results: (G1=420.966±79.400MPa; G2=188.768±39.081MPa; G3=580.100±74.010MPa; G4=240.484±45.536MPa). This study Conclusions: are that there is no statistically significant difference between the groups G2 and G4 (P<0.05).


1950 (6745)

Effectiveness of 5.3% hydrogen peroxide whitening strips in teenagers with fluorosis or white/brown enamel discoloration. K.J. DONLY1, A. SEGURA1, L. BAHARLOO*1, X. ZHOU2, and R.W. GERLACH2, 1 University of Texas Health Science Center--San Antonio, USA, 2 The Procter & Gamble Company, Mason, OH, USA

Objective: The purpose of the clinical study was to evaluate response of a 5.3% hydrogen peroxide tooth whitening strip system in conditions of fluorosis or other white/brown enamel discoloration. Methods: A total of 46 subjects 10 to 18 years of age used 5.3% hydrogen peroxide whitening strips. Of these, 18 subjects (39%) had visible fluorosis or other white/brown enamel discoloration prior to treatment, while the remaining 28 subjects had more uniform yellow tooth discoloration. Treatment was twice daily over an 8-week period (maxillary arch followed by mandibular arch), with efficacy measured using digital image analysis. Results: Mean baseline tooth color was less yellow (p =0.01) and brighter (p =0.08) among subjects with enamel discoloration. The following changes (CIE units) were noted:

 

Enamel Discoloration

No Enamel Discoloration

DL*

2wks: 1.9

4wks: 2.3

2wks 2.0

4wks 2.2

Db*

2wks -2.0

4wks -2.4

2wks -2.2

4wks -2.9

DE*

2wks 3.1

4wks 3.8

2wks 3.2

4wks 3.9

Both groups experienced significant (p < 0.0001) color improvements after 2 or 4 weeks whitening strip treatment. The two diagnostic categories did not differ significantly (p > 0.30) with respect to response at any time points. Less than 11% of subjects reported tooth sensitivity or oral irritation, and no subject discontinued treatment early due to an adverse event. Conclusion: These data demonstrated statistically significant improvement in color for pre-teens and teens with enamel discoloration, similar in magnitude to that seen for children without these enamel defects.


1951 (19308)

Clinical comparison of whitening with 6.0% and 5.3% hydrogen peroxide whitening strips. P.A. SAGEL, M.L. BARKER, C.R. MAYER*, and R.W. GERLACH, The Procter & Gamble Co, Mason, OH, USA

Objective: This research was conducted to compare the clinical response of two different peroxide-containing gel formulations delivered using self-applied whitening strips. Methods: A meta-analysis was conducted to assess the effectiveness of two different whitening gel formulations: a low water 5.3% hydrogen peroxide gel and a high water 6.0% hydrogen peroxide gel. Both studies were randomized, double blind trials. The maxillary teeth were treated twice daily over a 2-week period with whitening strips. Efficacy (L*a*b* color change) was measured objectively by digital image analysis. Results: A total of 60 adults ranging from 19-85 years of age participated in the research. Both treatments were effective in whitening teeth, as evidenced by a statistically significant improvement from baseline (p < 0.05). After adjusting for study effects and baseline, mean Db* (SE) for the high water content 6.0% hydrogen peroxide gel strip was –1.85 (0.151) compared to –1.41 (0.164) for the low water content 5.3% strip, with these treatments differing significantly (p=0.023). For the primary response variable Db*, this represented a 31.4% improvement in whitening for the higher water/higher concentration gel compared to the lower water/lower concentration gel. Outcomes for the other color parameters favored the 6.0% formulation. Both treatments were well-tolerated, and no subjects discontinued treatment due to adverse events related to bleaching. Conclusion: For whitening strips, this research demonstrates that a high water 6.0% hydrogen peroxide gel provides superior whitening clinical response compared to a low water 5.3% hydrogen peroxide formula.


1952 (19508)

Clinical trial comparing whitening strips to a carbamide peroxide potassium nitrate tray system. R.W. GERLACH, H. SHAHIDI*, and X. ZHOU, The Procter & Gamble Co, Mason, OH, USA

Objective: Several factors may impact bleaching-related sensitivity, including peroxide concentration, contact time, delivery system, use of desensitizing agents and others. This randomized clinical trial was conducted to evaluate the clinical response of a low peroxide bleaching system with a desensitizing agent relative to a marketed control. Methods: Balancing for baseline color and age, 34 healthy adult volunteers were randomized to one of two marketed bleaching systems. Subjects received either 5% carbamide peroxide bleaching gel + potassium nitrate in a custom tray or 6.0% hydrogen peroxide bleaching strips. Daily contact time was 6-8 hours for the tray system compared to 1 hour for the strip system, following manufacturers instructions. Whitening was measured objectively using digital image analysis to assess L*a*b* after 7 days. Results: The predominantly female (85%) and non-smoking (91%) study population ranged from 21-47 years of age. Both treatments yielded a statistically significant (p < 0.01) whitening benefit with respect to reduction in yellowness (Db*), as well as secondary endpoints (DL* and DE*). The strip group experienced greater color improvement on average for all color parameters in the study. After 7 days treatment, mean Db* was –1.20 in the strip group and –0.68 in the tray group, with these groups differing significantly (p=0.03). Tooth sensitivity was reported by 13% of subjects using the hydrogen peroxide strips, compared to 22% of subjects using the carbamide peroxide potassium nitrate tray system. No subjects discontinued treatment early due to an adverse event. Conclusion: The 6.0% hydrogen peroxide whitening strip system had greater whitening and less tooth sensitivity compared to the 5% carbamide peroxide potassium nitrate tray system.


1953 (16478)

Efficacy and safety of vital bleaching in teenagers using 6.5% hydrogen peroxide strips during the day or 10% carbamide peroxide tray system overnight. K.J. DONLY*1, F. GARCIA-GODOY2, A. SEGURA1, L. BAHARLOO1, E. ROJAS-CANDELAS1, X. ZHOU3, and R.W. GERLACH3, 1 University of Texas Health Science Center--San Antonio, USA, 2 Tufts University, Boston, MA, USA, 3 The Procter & Gamble Company, Mason, OH, USA

Objective: The purpose of the study was to compare a 6.5% hydrogen peroxide impregnated polyethylene strip tooth whitening system to a standard 10% carbamide peroxide tooth whitening system utilized overnight in a nightguard tray delivery system. Methods: One hundred and six subjects 11 to 18 years of age (mean 14.7 years) were recruited to participate in this randomized clinical trial. The study population included 61 females and 45 males. Treatment groups were balanced with respect to demographic characteristics and baseline tooth color. Thirty-five subjects used a 10% carbamide peroxide gel, delivered overnight in a nightguard tray. Seventy-one subjects used a 6.5% hydrogen peroxide whitening strip for 30 minutes twice per day. Results: Digital images were obtained at baseline, and again, after two and four weeks treatment, and outcomes were measured in terms of CIE units, where DL* indicates lightness, Db* indicates yellowness and DE* represents composite color. The following changes (CIE units) were noted:

 

Nightguard Whitening

Strip Whitening

DL*

2wks: 2.9

4wks: 3.3

2wks 2.5

4wks 2.6

Db*

2wks -3.3

4wks -4.1

2wks -2.9

4wks -3.5

DE*

2wks 4.6

4wks 5.4

2wks 4.1

4wks 4.6

Conclusion: Results demonstrated both tooth whitening systems significantly whitened teeth (p<0.0001). Both systems were well tolerated, and most events were mild in severity following the instructed use of the two systems.

(This research was supported, in part, by The Procter & Gamble Co.)


1954 (17881)

Clinical response of maxillary and mandibular teeth following use of 6.5% hydrogen peroxide whitening strips. R.W. GERLACH, R.D. GIBB*, and X. ZHOU, The Procter & Gamble Co, Mason, OH, USA

Objective: In traditional tray-based bleaching systems, increasing peroxide concentration is reported to impact on both whitening effectiveness and tolerability. This research summarizes the clinical response following use of a higher concentration whitening strip system. Methods: Data from three single center, parallel group, randomized clinical trials were pooled to assess the clinical response following extended use of a 6.5% hydrogen peroxide whitening strip. The study population consisted of teens and adults who underwent tooth bleaching (maxilla and mandible) twice daily for up to a 4-week period. Digital images of the 12 maxillary and mandibular anterior teeth were collected at baseline, and again throughout the study period to measure L*a*b* color change. Longitudinal analysis was used to estimate response over the treatment period. Results: The 101 study subjects exhibited considerable diversity with respect to age (11-56 years), ethnicity (49% non-white) and gender (59% female). For the primary response variable, change in yellowness (Db*), color improvement was evident after 1 week and continued through week 4. Mean changes in b* (SE) were -1.78 (0.13), -2.43 (0.16), -2.72 (0.28) and -3.12 (0.17) at Weeks 1, 2, 3 and 4 respectively. At each time point, color improvement differed significantly from baseline (p < 0.0001). The higher concentration strips were generally well-tolerated, with minor tooth sensitivity (33%) and oral irritation (31%) representing the most commonly reported events associated with treatment. Conclusion: This research involving a diverse population demonstrates that use of a 6.5% hydrogen peroxide whitening strip results in significant color improvement over a 4-week period.


1955 (19032)

Placebo-controlled clinical trial of a 6.0% H2O2 tooth whitener. E. SWIFT*1, H. HEYMANN, A. WILDER, A. ST-GEORGES, and M. NUNES, 1 University of North Carolina, Chapel Hill, USA

At-home tooth bleaching, which was formally introduced in 1989 by Haywood and Heymann, traditionally involves fabrication and use of a custom-fitted soft plastic tray for delivery of a carbamide peroxide or hydrogen peroxide gel.  Numerous laboratory and clinical studies indicate that at-home whitening is a safe and effective procedure.  Recently, a new delivery system was developed; it contains a measured dose of 6.0% hydrogen peroxide on a polyethylene strip.  Objectives: The purpose of this study was to compare the safety and efficacy of the new system (Crest Whitestrips, CWS) versus a placebo control.  Methods: Forty adult patients with teeth darker than A3 on a value-oriented Vita shade guide were enrolled in the study, and were randomly assigned to experimental and control groups.  All subjects applied the assigned agent to the maxillary anterior teeth for 30 minutes twice a day over a six-week period (or until the tooth shade was B1, the lightest Vita shade).  Efficacy was measured by digital imaging at 2, 4, and 6 weeks.  Safety was evaluated using an oral soft tissue examination at the same intervals.  Data were subjected to analysis of covariance.  Results: Use of CWS resulted in a mean Db* (decrease in yellow) of 3.25 units, compared with a change of 0.38 units for the placebo.  The corresponding values for DL* (increased lightness) were 2.73 and 0.21 units, respectively.  Differences were statistically significant (p<0.0001).  The most common adverse events were tooth hypersensitivity and gingival irritation.  Although both occurred mainly in the experimental group, the events were generally mild and transient.  Conclusion: The results of this study indicate that Crest Whitestrips provide statistically significant tooth whitening compared with a placebo as measured by digital imaging.  Supported by Procter & Gamble.


1956 (20394)

Clinical evaluation of professional vs over-the-counter tooth whitening agents. C.A. MUNOZ, T. EHRLER, B. DEIHL, M. ERICKSON, and M. DRUAN*, Loma Linda University School of Dentistry, CA, USA

Objective: Dental product manufacturers are now marketing tooth whitening products directly to patients. The purpose of this study was to compare an over-the-counter product (Crest Whitestrips™, Procter & Gamble) with a professional administered tooth whitening material (15% Opalescence, Ultradent). Methods: Using a simultaneous split-mouth protocol, 30 patients ranging from 18 to 45 years of age were selected to wear the over-the-counter whitening strips on the maxillary left quadrant and a professionally made custom tray on their maxillary right quadrant. Chromameter and Vita shade readings were taken at baseline, after two weeks of bleaching, and two weeks after treatment was completed (week 4). During the two weeks of bleaching, patients used both products for two 30-minute applications every day. Data were analyzed using a one-way analysis of variance (ANOVA) followed by the Student-Newman-Keuls method when significant differences were found (P<0.05). Results: Both test products produced a measurable amount of tooth whitening with no statistically significant differences in efficacy, color regression, or side effect (P>0.05). Although no cases of tooth sensitivity were reported, some patients experienced gingival sensitivity. Overall, patient satisfaction was higher with the professionally made custom tray technique than with the over-the-counter strips. Conclusions: Both products were found to be clinically effective in tooth whitening. In fact, there were no statistical differences in the amount of whitening achieved immediately after two weeks of bleaching and two-weeks after treatment. The patients found the strips less stable on the teeth and not as well adapted as the custom tray, especially to malposed teeth. The strips only extend from canine to canine, so some patients with a wide smile felt that they did not achieve complete esthetic results.


1957 (18135)

Use of a chroma meter to compare the shade change for two professional tooth whitening systems. R.W. GERLACH, K.L. CAMPOLONGO*, and X. ZHOU, The Procter & Gamble Co, Mason, OH, USA

Objective: Although common, use of shade guides to measure bleaching effectiveness carries risk for bias, particularly in comparative trials involving dissimilar products. This randomized clinical trial evaluated an objective method for shade measurement to compare shade changes for two professional vital bleaching systems. Methods: Twenty healthy adults were randomized to either a whitening strip containing 6.5% hydrogen peroxide or a custom tray-based, hydrogen + carbamide peroxide bleaching system. Shade change was measured objectively over a 14-day period using a portable chroma meter (Shofu® ShadeEye-Ex). Shade measurements were collected in triplicate from the facial cervical one-third of the maxillary right central and lateral incisors. Effectiveness was determined by comparing ranked (1-16) shade scores using standard methods. Results: In the 6.5% whitening strip group, individual improvement averaged 4.0 shades compared to 1.4 shades for the hydrogen + carbamide peroxide tray group. Both the strip group (p < 0.0001) and tray group (p=0.013) differed significantly from baseline with respect to objectively measured tooth shade. Between-group comparisons showed that the 6.5% whitening strip averaged an additional 2.7 shades improvement over the hydrogen + carbamide peroxide tray system, with these groups differing statistically (p=0.0011). Conclusion: When shade change is measured objectively using a chroma meter, the 6.5% hydrogen peroxide strip system yielded a nearly three-fold shade change compared to the hydrogen peroxide + carbamide peroxide, custom tray-based system. Such methods may help limit examiner bias in bleaching clinical trials.


1958 (9340)

Zero Sensitivity Tooth Whitening. R.M. POHJOLA*, W.D. BROWNING, S.T. HACKMAN, M.L. MYERS, and M.C. DOWNEY, Medical College of Georgia School of Dentistry, Augusta, USA

Many bleaching products have claimed to produce whitening of the teeth with reports of little or no sensitivity. Objective: Three commercially available dentist-prescribed home-applied bleaching systems were evaluated to identify the incidence of sensitivity and to compare the efficacy of whitening the maxillary anterior teeth of 18 patients. Methods: NiteWhite Excel 2Z (Discus Dental), fx (Challenge Products) and Rembrandt Xtra-Comfort (DenMat Corp) were randomly assigned to six patients each. The fx product was used as a control since it was not advertised as a zero sensitivity product. The manufacturer’s instructions for tray fabrication and use were followed while the patients bleached for two weeks. The patients kept a diary and were recalled at 1 week, 2 weeks and 4 weeks. The shade change and the presence or absence of any sensitivity were evaluated at each recall. Results: NiteWhite Excel 2Z was used for 83 total days of treatment with the following percentage of positive sensitivity reported: 0% hot and cold, 2.4% throat sensitivity, 2.4% tongue sensitivity and 25.3% gingival sensitivity. Rembrandt Xtra-Comfort was used for 84 total days and reported 0% hot and cold, 0% throat, 11.9% tongue and 27.4% gingival sensitivity. The fx product was used for 83 total days and resulted in 14.5% hot and cold, 7.14% throat, 1.2% tongue and 16.9% gingival sensitivity. All products lightened the teeth an average of 8 shade tabs on the Vita guide. There was a statistically significant difference between the groups when comparing the presence of sensitivity (Chi square: p<0.001), but not when comparing the shade tab change. Conclusion: Of the products tested, all produced similar change in shade tab value, none were sensitivity free, but NiteWhite Excel 2Z and Rembrandt Xtra-Comfort did not produce thermal sensitivity.


1959 (10317)

Densensitizing Gel Efficacy During Whitening in an at Risk Population. L.R. SMITH*, R.H. LEONARD, G.E. GARLAND, and D.J. CAPLAN, University of North Carolina, Chapel Hill, USA

Introduction: From a previous nightguard vital bleaching (NGVB) study, it was concluded that subjects answering “yes” to a questionnaire regarding preexisting sensitivity and/or consuming citrus drinks or sodas on a daily basis were at risk for tooth sensitivity(TS). Objective: The purpose of this study was to determine if the daily use of an active desensitizing gel (DSG) (UltraEZTM, Ultradent Inc) during (NGVB) would decrease (TS) in an at risk population when compared to a placebo. Methods: Forty subjects participated in this single blind, randomized clinical trial, that had indicated sensitivity or other risk factors prior to treatment. To evaluate TS caused by the tray alone, subjects wore custom-fitted maxillary whitening trays containing no DSG or whitening solution during Week 1. Subjects were randomly assigned to apply either the active DSG or placebo daily for 14 days in the trays for 30 minutes prior to whitening. The placebo was the same formulation as Ultra EZTM but without the desensitizing agents (3% potassium nitrate and 0.11% by weight fluoride ion). The bleaching solution was a 10% carbamide peroxide whitening solution (OpalescenceTM, Ultradent Inc.). Post-treatment, subjects were followed for one week while they used neither trays nor solutions. Throughout the study subjects completed a daily diary to record their perception of TS and the time they wore the tray with the whitening solution. Results: Forty-one percent of the active group had at least one day of TS during treatment compared to 78% of the placebo group. The difference was statistically significant (p>0.027) using the two-tailed Fisher’s exact test. Conclusions: This study suggests that this active DSG decreases TS when compared to placebo among subjects at risk for developing TS when whitening. Research Support: Ultadent, Inc. EMAIL: Lynn_Smith@dentistry.unc.edu


1960 (13907)

Sensitivity After Cavity Lining Or Etching And Sealing In Practice. J.F. MCCABE, J.M. WHITWORTH, R.K. WAIN*, and J.A. SMITH, University of Newcastle upon Tyne, United Kingdom

Objectives: We tested the hypothesis that etching, priming and sealing (E) cavities is no less effective in preventing postoperative sensitivity than traditional lining (L) with calcium hydroxide cement. Methods: Five hundred and seventy nine vital posterior teeth requiring an occlusal or proximal restoration were recruited from consecutive consenting patients in five general practices. Before cavity preparation, teeth were randomly allocated for L or E. Choice of bulk restorative material, amalgam (A) or composite (C), was at the discretion of the dentist. Patients recorded postoperative sensitivity at 24h, 4d and 7d on 100mm visual analogue scales (0=no sensitivity, 100=unbearable sensitivity). 362 amalgams (182L,177E) and 217 composites (92L,125E) were placed.Results:There was no significant difference amongst the mean sensitivity scores of any restorative combination at any given postoprative period. Mean sensitivity diminished with time for all combinations of cavity treatment and bulk restorative material. At 24h, the probability of a visual analogue score >50mm was 6.3% for L and 5.1% for E (p=0.182). The probability of recording a score >50mm was 7.8% for A and 3.6% for C (p=0.258). Regardless of threshold set, there was no significant difference in the likelihood of postoperative sensitivity for L or E teeth. Teeth restored with A were significantly more likely to yield sensitivity scores >80mm than those restored with C (p=0.021). Conclusions: There is no significant difference in early postoperative discomfort experienced by patients whose cavities were E or L. Primary care dentists can be confident that patients will not suffer increased postoperative sensitivity after cavity sealing with adhesive resins. Funded by UK NHS Primary Dental Care R&D scheme.


1961 (15727)

Effectiveness of Systemp.desensitizer in controlling dentinal hypersensitivity. R.J. CRISP*1, F.J.T. BURKE1, S. MCHUGH2, and U. LENDENMANN3, 1 University of Birmingham School of Dentistry, United Kingdom, 2 University of Glasgow, United Kingdom, 3 Ivoclar Vivadent, Schaan, Liechtenstein

Objectives:This study reports the effectiveness of Systemp.desensitizer (Ivoclar-Vivadent), which contains polyethylenglycol-dimethacrylate and glutaraldehyde in an aqueous solution, when used both with and without an acid-etch step, in treating dentinal hypersensitivity in UK dental practice patients. Method: After ethical approval, 10 dentists, with 91 suitable patients, were recruited from two practice-based research groups. Systemp.desensitizer was applied to the hypersensitivity areas, with 50% of cases etched with 35% phosphoric acid pre-application. Patients self-assessed their sensitivity before treatment, immediately post-treatment, and at one week, one month and three months by scoring their sensitivity on a proforma with 10cm Visual Analogue Scales, where no sensitivity scored zero, and severe sensitivity scored 10. Results: To date, 69 patient forms (76%), to 3 months, had been received. The data was analysed statistically, determining pain reduction and assessing any differences between etched (E) and non-etched (NE) groups. Overall, about 80% (80% for NE, 78% for E) of patients reported a reduction in pain immediately after treatment, rising to 90% (91% for NE, 87% for E) after one week, 91% (88% for NE, 95% for E) after one month and 93% (94% for NE, 90% for E) at 3 months, indicating a different pattern of change in pain score across the two groups. There were significant reductions in pain scores for both groups at all time points, but there was no significant difference between E and NE groups. Conclusion: It is concluded that Systemp.desensitizer was effective in reducing pain from dentinal hypersensitivity in the patients treated, and this was unaffected by whether the tooth was acid etched prior to resin application. The support of Ivoclar-Vivadent, Schaan, Liechtenstein is acknowledged.


1962 (9820)

Nightguard Vital Bleaching of Tetracycline Stained Teeth 7.5 Years Post-treatment. R.H. LEONARD*1, V.B. HAYWOOD2, D. CAPLAN1, and N. TART1, 1 UNC Chapel Hill, NC, USA, 2 Medical College of Gerogia, August, GA, USA

Objective:The purposes of this longitudinal whitening study were to determine the stability, post-treatment side effects, and patient satisfaction after six months active treatment of tetracycline teeth with 10% carbamide peroxide (Opalescenceâ) at 7.5 years (84-100 months).  Methods:Fifteen of the 21 patients participating in the study (71%) were contacted and asked to participate in a survey concerning their whitening experience.  Subjects were asked whether or not there had been any change in the shade of their teeth post-treatment.  Subjects were also asked if they had experienced any side effects during the post-treatment period that were whitening related and their perception of the procedure.  Results: Nine (60%) reported no obvious change or only a slight darkening not noticed by others, 1 (7%) reported a slight darkening that is probably noticeable by other people, 1 (7%) reported moderate darkening.  No one reported darkening back to original shade; however, 4 participants (27%) reported retreating their teeth.  All respondents (15) denied having to have a crown, or root canal, that they felt was whitening related.  One participant (7%) reported having TS and/or GI post-treatment; however, they also reported sensitivity to hot and cold pre-treatment.  All 15 participants (100%) were glad they went through the whitening process and 14 (93%) would go through it again.  Eight of the 15 participated in a clinical exam.  The gingival texture, contour, and color of each patient were WNL.  No periapical pathology (abscess, external resorption) was noted on radiographic examination and enamel surface morphology as viewed under the SEM at 200 and 2000 magnification appeared normal.  Conclusions:This whitening study suggests that shade stability may last at least 7.5 years (range 84-100 months) post-treatment in patients with tetracycline-stained teeth with minimal side effects.  In terms of patient satisfaction, patients are overwhelmingly positive about the procedure. Research Support: Ultradent, Inc.   


1963 (18249)

Clinical Evaluation of an In-Office Tooth Whitening System. D. BARDWELL*, A. PAPATHANASIOU, and P. GEORGI, Tufts University School of Dental Medicine, Boston, MA, USA

Objectives: The purpose of this study was to evaluate the efficacy of a 15% hydrogen peroxide in-office tooth whitening system (Illumine¢ Whitening System, Dentsply Professional) in a stand alone technique. Methods: Twenty (20) patients with no compromised medical history or tooth sensitivity participated in this randomized, parallel clinical evaluation. Only six maxillary anterior teeth with minor uniform intrinsic staining or discoloration with a shade no lighter than A-3 were selected. The six mandibular anterior teeth were used as the control group. After receiving a prophylaxis, each patient was evaluated for initial (baseline) shade by three evaluators, pre-calibrated at 85% rate reliability before the onset of this project. Shades were assessed using the Standard Vita Shade Guide arranged in value order. Alginate impressions were taken for fabrication of upper custom bleaching trays. Each patient received a 30 minutes initial in-office treatment utilizing the custom tray to deliver the 15% hydrogen peroxide material (Illumine¢ Whitening System, Dentsply). Patients returned at 24 and 72 hours for shade evaluation and additional applications. Patients were requested to return after 7 days and at 6 months after the final bleaching application for shade evaluation. Results: The results of this study revealed an average of 8.4±1.6 shade change. Shade changes were determined from the number of shades on the Vita Shade Guide when arranged in Value Order. One Way Anova revealed significant difference between pre-treatment and post-treatment recalls (p<.01). T-test revealed no significant difference between 7 day and 6mo. recall. Conclusions: In conclusion, the results of this study reveal significant shade lightening after 3 consecutive applications of this 15% hydrogen peroxide. Furthermore, no significant difference in shade change(rebound) was observed from 7day through 6 mo. recall.


1964 (18537)

Effect of hydroxyapatite toothpaste on vital tooth color. C. GUO*1, H. LIU1, and I. KATAYAMA2, 1 Peking University, Beijing, China, 2 Meikai University School of Dentistry, Sakado, Saitama Pref, Japan

Objectives: Hydroxyapatite (HAP) adsorbs cariogenic bacteria and remineralizes subsurface demineralized areas of tooth enamel, and is a registered anticaries toothpaste ingredient in Japan. We examined its effect on tooth color, which reportedly changes up to 2 Lumin shades when treated with bleaches like hydrogen peroxide. Method: Two 6-person groups brushed their teeth 5 minutes 3 times daily for 30 days, one using HAP toothpaste (Apagard, Sangi Co., Ltd.) and the other an identical toothpaste without HAP. The color of subjectsf central incisors was measured initially, then every 2-3 days (3 measurements each at the center of the labial surface) using a Photoresearch Spectra-Scan PR-650 photocolorimeter. The difference between initial and final average CIE L*a*b* values (DE) was calculated for each subject and compared with the average DE for reddish brown tabs (A1 through A4) and reddish yellow tabs (B1 through B4) on the Lumin Vacuum guide, calculated using a Murakami CMS-35FS spectrophotometer. Two groups of extracted human teeth were brushed 5 minutes 3 times daily for 7 days using the same toothpastes respectively, then examined by SEM (Hitachi S-4500). Results: Vital teeth in the HAP group showed increased L* and an average DE of 3.48, against 1.45 and no change in L* for the non-HAP group. Comparison with Lumin average DE values (2.52 for A tabs and 3.55 for B tabs) showed the HAP group color change was equivalent to 1.4 shades on the reddish brown scale and 1.0 shade for reddish yellow. SEM observation showed a fine particle coating on extracted teeth in the HAP group, but not in the non-HAP group. Conclusion: Though less powerful than harmful bleaches, the results suggest HAP toothpaste can alter tooth color by at least one shade with daily brushing, and this effect may be related to its plaque-adsorbtion and enamel remineralization properties.


1965 (18222)

Impact of behavioral, clinical and demographic parameters on whitening response: Evidence from 18 clinical trials. X. ZHOU*, M.L. BARKER, R.D. GIBB, and R.W. GERLACH, The Procter & Gamble Co, Mason, OH, USA

Objective: This research investigates the impact of behavioral, clinical and demographic parameters on whitening response using an extensive clinical trials database collected as part of the development of a strip-based tooth whitening system. Methods: Data from 18 different clinical trials were included in the analysis. This inclusive assessment involved study subjects who used a flexible polyethylene, whitening strip coated with an adhesive hydrogen peroxide bleaching gel. All subjects used a common regimen, wherein whitening strips were worn twice daily over a 2-week period. Efficacy was measured in a common fashion using digital images of maxillary anterior teeth to objectively determine tooth color change in CIELAB units (b* yellowness, L* lightness, and a* redness). Results: The analysis included 300 subjects with complete demographic, behavioral and effectiveness data. Initial tooth color, age, tobacco use and race were significantly (p < 0.05) related to the primary clinical response (Db*). Subjects who regularly used tobacco experienced less whitening (0.33 Db*) on average compared to non-users. Coffee/tea/cola consumption was not significantly related to clinical response. Initial tooth color was the most significant (p < 0.0001) factor related to whitening. For subjects having the same age, racial background and smoking habits, each 1-unit increase in baseline yellow tooth color resulted in approximately 10% more color improvement after 14 days of treatment. Conclusion: This meta-analysis of whitening strip research demonstrates that baseline color and other factors are significant determinants of whitening effectiveness.


1966 (14480)

Functional polyorganosiloxane-based low-stress composite. R. YIN*, L. SHARP, and B.I. SUH, Bisco, Inc, Schaumburg, IL, USA

Objective: To synthesize and investigate a functional polyorganosiloxane (POS) as a low contraction stress monomer in dental composite. Method: Five POS monomers have been prepared through two steps hydrolysis and condensation using different organotrialkoxysilane and Methacryloxypropyltrimethoxysilane. The functionality was controlled by molecular ratio.  The composites consisted of 22% light-curable POS resins (POS/BisGMA/UDMA/TEGDMA) and two types of fillers, Degussa OX-50 (0.04 µm) and Schott Barium glass (0.7µm). Microstrain test was carried out using a microstrain gauge which was attached to an acrylic ring to measure the strain as a representation of the contraction stress caused by composite shrinkage. Acuvol and Instron 4466 were employed to determine shrinkage and diametral tensile strength (DTS), respectively. Result: The microstrain of POS resin was much lower than the control and also can be reduced more than 60 % with pulse-delay cure technique.  POS-UDMA IPN showed only 700 µm/m microstrain. However, the microstrain of POS composite was not affected with silanaed and non-silanated fillers. A good mechanical property and high filler loading could be obtained by adding 20 % POS to the resin.

Resins and

Control

POS

Control

POS

POS-IPN

Composites

Resin

Resin

Composite

Composite

Composite

Microstrain(µm/m)

2400±120

2000±100

1800±60

1400±70

700±45

Shrinkage (vol %)

9.61±0.02

4.52±0.01

3.52±0.05

2.10±0.03

2.85±0.02

DTS (MPa)

32.4±6.5

29.8±4.5

49.2±5.6

51.9±7.8

50.5±5.3

Conclusion: POS has the potential to serve as a new monomer in dental composite due to its low contraction stress and good compatibility with glass filler.

 


1967 (14663)

Mechanical Strength and Water Sorption of Amorphous Calcium Phosphate-filled Bis-GMA-based Composites. D. SKRTIC*, American Dental Association Health Foundation, Gaithersburg, MD, USA, and J.M. ANTONUCCI, National Institute of Standards and Technology, Gaithersburg, MD, USA

We have previously described several photocurable, potentially bioactive composites consisting of conventional dental resins and amorphous calcium phosphate (ACP) fillers. Objective: To determine the effect of varying the hydrophilicity of Bis-GMA resins on the biaxial flexure strength (BFS) and water sorption (WS) of the unfilled polymers and their composites. Materials & Methods: Triethylene glycol dimethacrylate (TEGDMA), 2-hydroxyethyl methacrylate (HEMA), glycerol dimethacrylate (GDMA), and ethylene glycol methacrylate phosphate (PHEMA) were used as co-monomers with Bis-GMA (BT, BH, BG, and BP resins, respectively, at 1:1.79 mole ratio). Silica-hybridized ACP (Si-ACP) was used as the filler at a mass fraction of 25 % or 40 %. BFS was determined before (dry) and after one-month exposure of disk specimens to buffered saline solutions (wet). WS was measured gravimetrically by recording mass changes of specimens exposed to 75 % relative humidity for 40 days. Data were analyzed by multi-factorial ANOVA (a=0.05) and by pair-wise multiple comparisons. Results: BFS of both dry and wet unfilled BT, BH and BG resins ((140±18) MPa) was significantly higher than the BFS of dry BP resins ((57±12) MPa). Introduction of Si-ACP reduced the BFS of dry specimens up to 76 %. BFS of all composites further deteriorated upon soaking; BT composites deteriorated less than BH, BG or BP composites. Unfilled BP resins absorbed 3.5 times more water than BT, BH or BG resins (mass fraction of (9.2±0.5) % vs. (2.6±0.4)%). WS increased with increasing levels of ACP in BT, BH and BG composites. In BP composites ACP inversely affected the WS, due to specific ACP-PHEMA interaction(s). Conclusion: All hydrophilic co-monomers for BisGMA/ACP composites had an adverse effect on BFS after aqueous exposure, especially in the case of  BP composites. Supported by NIDCR R01-DE13169, ADAHF, and NIST.


1968 (15945)

Vinyl Ester/Initiator Effects on the Flexural Strength of Experimental Resin Composites. D.A. LONERGAN*1, G.E. SCHUMACHER2, J.M. ANTONUCCI3, A.A. GIUSEPPETTI2, and W.F. GUTHRIE3, 1 U.S. Navy, Bethesda, MD, USA, 2 American Dental Association Health Foundation, Gaithersburg, MD, USA, 3 National Institute of Standards and Technology, Gaithersburg, MD, USA

Objectives: The aim of this study was to investigate the effects of both a vinyl ester monomer additive and two photoinitiator systems (redox vs. a-cleavage at two levels) on the flexural strength (FS) of glass-filled Bis-GMA/TEGDMA composites. Methods: The experimental resin (comprising Bis-GMA [50 %], TEGDMA [40 %] and neo-decyl vinyl ester [Neo-10, 10 %]) was activated at 2 levels (1 or 2 %) with either camphorquinone (CQ) + ethyl 4-N,N-dimethylaminobenzoate (4E) or a bis (acyl phosphine oxide) modified with a UV photoinitiator (BAPO). The photoactivated resins were reinforced with a silanized glass filler (0.7 µm) at a loading of 85.7 %. (% indicates mass fraction.) Similarly loaded control composites were formulated from Bis-GMA/TEGDMA (1:1 by mass), also activated with CQ/4E or BAPO at 2 levels (1 and 2 %). A randomized, 23 factorial design was utilized consisting of eight composite groups, n=8/group. Sixty-four composite bars, (2 x 2 x 25) mm, were fabricated by light curing for 60 s/side and tested by 3-point bending at a crosshead speed of 0.5 mm/min after aqueous storage for 24 h at 37 °C. The resulting data were analyzed using a 3-way ANOVA (a=0.05). Results: ANOVA showed that all three factors (presence of Neo-10, the initiator type, and the initiator concentration) have significant main effects on the FS (p<0.05). Two-factor interaction between the initiator type and concentration was also significant (p<0.03). Of the eight composite groups, mean FS ranged from 138.1 (Neo-10 + BAPO, 2 %) to 96.8 (1850, 1 %) MPa. Conclusions: Both the presence of Neo-10 and BAPO initiator significantly increased the FS of the composites. Use of higher initiator concentration also significantly increased the FS. The judicious use of both Neo-10 and BAPO show promise as a means to strengthen resin composite restorative materials. Supported by NIST/NIDCR Interagency agreement Y1-DE-10021-02 and ADAHF.


1969 (15969)

Effect of Solvent Type on Absorption Profile of Camphorquinone. L. MOSS*1, F.A. RUEGGEBERG1, and J.W. STANSBURY2, 1 Medical College of Georgia, School of Dentistry, Augusta, USA, 2 University of Colorado Health Sciences Center, Denver, USA

The absorption spectrum of camphorquinone (CQ) is typically performed in methanol. Objective: The effect of a variety of different solvents was investigated on peak absorption wavelength of a commonly used photoinitiator in dentistry, CQ. Methods: Commercial CQ was used, being a mixture of both optical isomers. The mass (mg) of CQ per mL solvent was 4.33. CQ was dissolved in a variety of solvents representing a range of polarities, some of which are commonly used as solvents in dentin bonding agents, as well as some dental monomers: (presented in decreasing rank of polarity) water, glycerol, methanol, HEMA, MMA, TEGDMA, and mineral oil. The visible light absorbance spectrum was obtained using a UV-VIS spectrometer (Chem 2000, Ocean Optics). The wavelength (nm) associated with peak absorbance was determined from each spectral run. Four specimens were made for each test condition. Statistical analysis: 1-way ANOVA, Tukey-Kramer post-hoc test, significance level p<0.05. Results: Similar small case letters connect statistically equivalent values:

Water

Glycerol

Methanol

HEMA

MMA

TEGDMA

Mineral Oil

456.8±0.5a

463.82±0.4

467.1±0.5a

468.1±0.8a

472.9±0.5

474.4±0.2

484.7±0.5

Conclusion: Solvent had a significant influence on the peak absorption wavelength of CQ. With increasing solvent polarity, the peak absorbance wavelength increased. These absorbance shifts might influence the ability of narrow spectral emission light sources in their interaction with the photoinitiator.


1970 (16168)

Effects of Silane Coupling Agents on the Fluoride Release from Experimental Dental Composites. X. DING*, L. LING, X. XU, and J.O. BURGESS, Louisiana State University Health Science Center, School of Dentistry, New Orleans, USA

Silane coupling agents play an important role in increasing the mechanical strength and wear resistance of dental composites. However, they also significantly reduce the fluoride release from the filler particles. Objectives: the objective of this study was to investigate the effects of the silane coupling agents with different hydrophilicity on the fluoride release of dental composites. Methods: eight experimental composites were fabricated using two polymer resins. Resin 1 consisted of 40% Bis-GMA, 40% TEGMA and 20% UEDMA. Resin 2 had the same composition except that Bis-GMA was replaced with an experimental fluoride-releasing monomer containing metal chelate. Fluoride–releasing fillers (5 mm, Industrial Inc.) were treated with three silanes: a hydrophobic silane [γ-methacryloyloxypropyltrimethoxysilane] (S1) (Sigma-Aldrich) and two hydrophilic silanes: [O-(methacryloxyethyl)-N-(triethoxysilylpropyl)urethane (SO) and N-(3-methacryloxy-2-hydroxypropyl)-3-aminopropyltriethoxysilane] (SN) (Gelest, Inc.). The filler particles were treated with 3% silane-toluene solution at room temperature for 24 hours and heated at 60oC for 24 hours before mixing with the resin with the resin/particle ratio of 40/60. Cylindrical specimens 4x9 mm (n=5) were prepared and light cured for 40s on each surface and longitude side. The specimens were stored in 3 ml deionized water.  Fluoride concentrations were measured daily using an ion selective electrode (Orion) for 21 days. Results: the cumulative fluoride released in 21 days (mg/cm2) ± SD was shown below. The data were analyzed using ANOVA and Tukey B post-hoc tests.

Materials

No Silane

S1

SO

SN

Resin 1 (Bis-GMA/ TEGMA/UEDMA)

77.39 ± 7.55

25.13 ± 3.16

36.90 ± 7.19

62.93 ± 5.52

Resin 2 (Exp. Monomer/ TEGMA/UEDMA)

141.54 ± 7.14

62.99 ± 16.07

79.98 ± 12.58

91.58 ± 10.74

Conclusion: Composites with hydrophilic silane coupling agents release significantly more fluoride than composites with hydrophobic silane. The composites from monomer containing metal chelate have significant higher fluoride release than conventional dental composite. Supported by the Brown Foundation.

 


1971 (17088)

Development of Novel Hard Relining Material with Odorless Monomer. M. YAMASHITA*, T. KAWAGUCHI, and O. IWAMOTO, Tokuyama Dental Corp, Tsukuba, Japan

Objectives: Chair-side hard denture reline materials with no methylmathacrylate as monomer composition have been developed and widely used clinically. Recently, we have successfully developed a novel hard denture reline material, "trial A", which uses a newly developed methacylic monomer that possesses acetoacetoxy group "AAEM" which involves reduced heat, odor and chemical irritation to allow the material to cure completely in the mouth. The purpose of this study was to clarify the properties of this newly developed hard reline material "trial A" and to compare it with that of commercially available materials. Methods: The hardening time and temperature rise were measured according to ADAS No.17. The odor and chemical irritation were evaluated clinically by 3 degrees(E: excellent, G: good, P: poor). The polishing of surface-roughed relining material was performed by using a chair-side polishing system, "TOKUSO REBASE POLISHING SYSTEMTM". Results:

  

trial A

TOKUSO REBASETM

GC RELINETM

Ufi Gel hardTM

DENTURE LINERTM

Fast

normal

fast

normal

odor /irritation

E/E

E/E

P/E

P/E

P/E

G/E

G/E

hardening time (temp.)

4'40"(53.6)

6'27"(51.4)

4'45"(59.4)

6'22"(56.5)

5'20"(59.4)

4'50" (52.2)

7'35"(50.2)

polishing period

fast

fast

medium

medium

medium

very slow

medium

Conclusion: Main advantage of a newly developed denture reline material was odorless in the mouth and the shorter polishing period compared to those of other materials.


1972 (17642)

Self-curing dental composition with improved shelf-life stability. S. JIN*1, W. JIA1, W. JIA, A. PRASAD1, and A. PRASAD, 1 Jeneric/Pentron Inc, Wallingford, CT, USA

Self-curing Dental Composition with Improved Shelf-life Stability

Shuhua Jin*, Weitao Jia, and Arun Prasad

Jeneric/Pentron, Inc., Wallingford, CT 06492

The purpose of this study was to determine whether a new self-curing initiating system possesses improved shelf-life stability over the conventional benzoyl peroxide/amine system. The new dental composition used a redox self-curing system consisting of a hydroperoxide oxidizing agent and a substituted thiourea reducing agent. This self-curing system is believed to be more stable at elevated temperatures. Methods: Cumene hydroperoxide (CHP) and acetyl thiourea (ATU) were selected as a pair of the redox initiator system vs. conventional BPO/DHEPT system in a paste/paste composition of resin matrix of BISGMA and TEGDMA and barium glass filler. Shelf-life stability was tested after aging the pastes at 37° and 50°C for different time intervals. Curing test of the two self-curing systems was performed at 22oC using 1:1 weight ratio of catalyst and base. Results: Gel and set times are as follows:

Aging

Aging time

Gel time/setting time

Temperature

(week)

BPO/DHEPT system

CHP/ATU system

 

370C

0

1

2

3

4

2’30"/3’40"

1’30"/2’20"

1’20"/2’10"

1’30"/2’20"

1’40"/2’20"

4’30"/6’10"

4’00"/5’30"

4’00"/5’30"

4’10"/5’10"

3’50"/5’00"

 

500C

0

1

2

3

4

BPO paste hardened

in two days

4’30"/6’10"

4’00"/5’30"

4’50"/6’20"

6’30"/8’30"

6’30"/8’30"

The results show CHP/ATU system being quite stable for four weeks of aging at 37oC. While BPO catalyst paste gelled in two days at 50oC, CHP paste did not gel after four weeks. Though the gel and set times after 4 weeks were slower, CHP/ATU pastes displayed good curability. Conclusion: the CHP/ATU initiator system in self-cured dental compositions improved shelf-life stability. Further study, especially bio-compatibility evaluation, is still needed. Supported by DOD grant DAMD17-99-C-9017.


1973 (17691)

Novel tris-methacrylate monomers having Low Viscosity and LPS for dental resins. F. GAO*, S.R. SCHRICKER, and B.M. CULBERTSON, Ohio State University, Columbus, USA

Objective: We have previously reported the synthesis of trimethacrylate monomers based on 1,1,1-tris(4-hydroxyphenyl)ethane. Here we report a new derivative with a more disordered structure in order to further lower the viscosity of the resin. Methods: 1,1,1-tris-[4-(1-methacryloxy-2-methyl-ethyloxy)phenyl] ethane (TMMPE) was synthesized in a good yield. The new monomer has a low viscosity of 131(± 12) Poise at 25oC. It was mixed with triethyleneglycol dimethacrylate [TEGDMA] for neat resin evaluation, with a BisGMA/TEGDMA as control. The solution viscosity (h ) before photopolymerization (VLC), linear polymerization shrinkage (LPS), double bond conversion (DC), glass transition temperature (Tg) of cured resin, and mechanical strength such as compressive strength (CS), compressive modulus (E) and flexural strength (FS), were measured. Results:

Sample

h * (Poise)

LPS* (%)

DC (%)

Tg*(° C)

CS* (MPa)

E* (GPa)

FS* (MPa)

aBisGMA/TEGDMA

0.58(0.11)

6.69(0.21)

80.8

42.45(2.1)

384(18)

2.46(0.44)

72.6(3.8)

aTMMPE/TEGDMA

0.22(0.06)

5.85(0.14)

86.3

53.89(2.8)

391(23)

2.65(0.38)

84.4(6.8)

bBisGMA/TEGDMA

7.44(0.93)

4.86(0.10)

77.6

45.92(2.4)

425(27)

3.24(0.25)

105.3(4.4)

bTMMPE/TEGDMA

1.87(0.14)

3.49(0.16)

85.9

55.74(2.0)

452(41)

3.12(0.22)

97.2(9.8)

Samples a and b are formulated by two components of 50/50 and 70/30 wt., respectively. *All entries in the Table are the mean value of six specimens with the standard deviations in the parentheses. LPS were determined by using the simple "deflecting disk" method, DC were measured by 13C-NMR; Tg were obtained by DSC. Conclusions: The results show that TMMPE/TEGDMA resins have lower viscosity and LPS as well as higher double bond conversion, without losing physical properties .


1974 (17837)

Development of experimental molecule for composites in order to valuate the mechanical behavior in comparison with commercial molecules. C. MORALES-ZAVALA*, F. BARCELÓ, and C. ALVAREZ-GAYOSSO, Universidad Nacional Autónoma de México, Mexico City, Mexico

Objective: The mechanical properties of a composite are important to predict its behavior and longevity in oral cavity. The purpose of this study is valuate a experimental composite in comparison with commercial composites.

Methods: We developed a molecule with Bisphenol-A-glycidyl dimethacrylate (Bis-GMA or Monomer of Bowen). Bis-GMA experimental, TEGDMA, Benzoyl peroxide (BPO), N,N-Dimethyl-p-toluidine (DMPT) and silica was used in order to produce a self curing resin. This blend was called sample (A). Several comparisons were studied: 1. Commercial molecule (without TEGMA), TEGDMA, BPO, DMPT and silice: (B), 2. Commercial molecule (with TEGDMA), BPO, DMPT and silice: (C), and 3. Commercial compound: (D) were tested. Compressive and flexural strength tests were analyzed. Average values were obtained to according 27 A.D.A. Specification.

Results: Compression strength values of 71.95 Mpa for sample (A), 90.46 Mpa for (B), (C): 94.56 Mpa and (D): 80.14 Mpa were obtained. Flexural strength values were: (A) 77.93, (B) 29.50, (C) 55.90 and (D) 93.72.Mpa.

Conclusions: The results show that composite with experimental molecule presents acceptable characteristics. The study will continue and these results are an advance of the principal goal of the work. This project is supported by DGPA.UNAM IN201799.


1975 (18617)

Study of Polymethyl Methacrylate Bone Cement containing Bovine-derived Defatting Demineralized Bone Powder. U.-K. KIM*, S.-I. CHO, S.-G. KIM, and J.-K. KOOK, Oral Biology Research Institute, Chosun University, Kwang-ju, South Korea

Objectives: Addition of bovine bone drived defatting demineralized bone (BBDDDB) powders to a PMMA bone cement is shown to produce a class of composites that due to their microstructure and mechanical properties may be suitable for application as bone substitutes. In order to investigate the influence of BBDDDB reinforcement on the PMMA bone cement. Methods: We mixed PMMA (Osteobond) and BBDDDB(Made by Wongang bone bank recommand) with 1:1,1:2, 2:1 weight%. Specimens employed in the fleural, compressive, tensile test. The compressive, indirect tensile and flexible strengths were measured and discussed for BBDDDB-PMMA composites. Result: Mechanical properties of 1:1 composites is superior as 1:2, 2:1 composites(P<0.01). Conclusion: The PMMA forms a solid cellular matrix with open cells about 100 micrometer in size and incorporating BBDDDB. BBDDDB aggregates inside the cells form a porous network, with average mesopore diameters of about 250-400¥ìm, that is accessible from the outer surface. If BBDDDB is added to PMMA in the form of dried powders, the composites are applicable as bone substitutes. The mechanical and material properties of the BBDDDB-PMMA bone substitute composites are competitive with those properties of a porous ceramic matrix of other hydroxyapatite and with those of natural bones.


1976 (19312)

The Effects of Filler Loading on an Intercalated Dental Nanocomposite. L.M. SMUCKER*1, K.M. ISLAM1, and T.J. PINNAVAIA2, 1 Dental Technologies, Inc, Lincolnwood, IL, USA, 2 Michigan State University, East Lansing, USA

Objectives: In order to determine the optimum filler loading for a novel dental nanocomposite, this study investigated the effects of varying the amount of intercalated layered silicate platelets on the compressive and flexural strength of the nanocomposite. Methods: Surface treated smectite clay particles were suspended in a methacrylate functional monomer blend at 0, 4, 5, 6, 10, 15 and 20 wt%. The average size of the silicate platelets range from 100 – 1000 nm by 1 nm. Upon chemically initiated polymerization of the monomer, the suspended silicate platelets became intercalated within the resin matrix as confirmed by TEM analysis. XRD patterns indicated an average spacing of 40nm between platelets. Samples were prepared according to ANSI/ADA Specification No. 27 for compressive and flexural strength determination using a Universal Testing Machine (Instron 1011). A minimum of 5 samples was prepared for each analysis.

Results: Ave (s.d.)

Filler Load (wt%)

0%

4%

5%

6%

10%

15%

20%

Compressive Strength (MPa)

177.2

(10.5)

190.1

(9.7)

225.1

(10.5)

201.2

(8.7)

211.4

(12.6)

202.2

(18.8)

200.0

(10.2)

Flexural Strength (MPa)

84.2

(8.4)

73.9

(7.4)

80.7

(8.4)

76.4

(4.2)

66.5

(6.5)

64.8

(6.3)

61.4

(10.5)

Conclusions: These results indicate that the optimum filler loads for both compressive and flexural strengths were 5 wt%. The flexural strength of the neat polymer was higher without incorporation of the filler and the compressive strength was significantly improved with the addition of this novel filler.


1977 (21660)

Brief screening of new di- and tri- methacrylated POSS monomers for dental resins. Y. SUN*, F. GAO, S.R. SCHRICKER, and B.M. CULBERTSON, Ohio State University, Columbus, USA

Objective: Polyhedral Oligomeric Silsesquioxanes (POSS) are nanostructured organic/inorganic hybrid compounds, having potential for as fillers in nanocomposites. We present some preliminary data on two methacryloyl functionalized POSS molecules. Methods: Two POSS monomers, MA-I and MA-II were provided by Hybrid Plastics. MA-I is an open cage POSS structure with two methacrylate groups and MA-II is a similar structure with three methacrylate groups. Both structures were formulated with a 2:1:3 mixture of BisEMA:HDMA (hexanediol dimethacrylate):t-BMA (t-butyl methacrylate) as shown in the table below and photopolymerized, with the compressive strength (CS) of the material measured. The control is methacrylate mixture without POSS and the monomers were polymerized neat. A non-standard methacrylate control was used because of solubility problems with standard BisGMA based resins, one of the goals of this work is to help develop POSS that are highly soluble in dental resins. Results: In the 5 and 10% formulations of MA-I and MA-II the CS was higher than either the control or neat POSS. This is also true for the MA-II 20%. The remaining formulations had properties at least as good as the control.

MA-I*

Control

MA-I 100%

MA-I 5%

MA-I 10%

MA-I 20%

MA-I 40%

CS MPa (SD)

229.5 (23)

74.8 (11)

327.5 (42)

307.5 (34)

240.5 (31)

204.2 (16)

             

MA-II*

Control

MA-II 100%

MA-II 5%

MA-II 10%

MA-II 20%

MA-II 40%

CS MPa (SD)

229.5 (23)

92.9 (14)

322.9 (13)

325.1 (46)

300.7 (13)

267.3 (18)

*Sample Size N=4 Conclusions: Methacrylated POSS monomers can be formulated with methacrylated resins to produce materials with improved properties over the individual components. This suggests that POSS has potential for use in dental restorative nanocomposites.


1978 (21760)

A high-strength liquid crystal monomer based resin composite. B.K. NORLING*, J.L. PAGE, N. SATSANGI, H.L. CARDENAS, and H.R. RAWLS, University of Texas Health Science Center at San Antonio, USA

Cure (polymerization) shrinkage remains a major barrier to universal use of resin restoratives in large posterior cavity preparations. Previously, we have reported on a liquid crystal (LC) monomer system consisting of C6-t-butyl-diacrylate and its naturally occurring Michael-like reaction byproduct which yielded a resin composite with 0.84 volume percent shrinkage when filled 80 wt. % with silica. Unfortunately, the composite was mechanically weak. Objectives: The goal of this study was to develop a LC based composite with good mechanical properties. Methods: Experimental composites were mixed at 82 wt. % filler in a Whip-Mix single die vacuum mixer using the Tetric (Ivoclar, Lichtenstein) filler system and the Tetric monomer system (T), the diacrylate mixture previously described (DA) and a blend of 90 wt. % of the dimethacrylate analog of the diacrylate monomer and 10 wt % Bis-EMA (DMA). The latter two monomers were photoinitiated with camphoroquinone/DMAEMA. To ensure that the mixing procedure was adequate, commercial Tetric was used for comparison (CT). Transverse strengths and moduli were measured according to ISO 4049-2000 using an Instron/MTA universal testing machine. Results: The resulting transverse strengths (s.d.) are CT: 127 (17), T: 117 (19), DA: 38 (11), DMA: 118 (14) MPa. Related moduli (s.d.) are CT: 12.0 (0.0), T: 12.6 (1.9), DA: 3.0 (0.7), DMA: 13.4 (2.3) GPa. For both measures, DA fell into a statistical subset by S-N-K, p < 0.01. Conclusions: The Whip-Mix mixer proved suitable for mixing resin composites. The DMA LC based composite was statistically as strong and stiff as the commercial conventional monomer analog. Supported by NIH-NIDCR Grant P01DE11688.


1979 (9704)

Synthesis and evaluation of new oligomers containing both carboxyl and vinyl functionalities for dental restoratives. D. XIE*, The University of Alabama at Birmingham, USA

The objective of this study was to synthesize and characterize new oligomers containing both carboxyl and vinyl functionalities, formulate the formed composites, as well as evaluate their mechanical properties. The oligomers were the addition products of diphenylcarboxylic dianhydride with glycerol dimethacrylate (BPTCDAGDMA) and with 2-hydroxyethyl methacrylate (BPTCDAHEMA), respectively. The structures of the oligomers were characterized using FTIR and 1HNMR. Compressive (CS) and diametral tensile strengths (DTS) of the synthesized oligomers formulated with TEGDMA or TEGDMA/TMPTA-N were determined after conditioned in distilled water at 37oC for 24 hours. Mechanical testing was performed in a Universal Testing Machine with a crosshead speed of 1 mm/min. Commercial Fuji II LC (FL) glass was used to formulate the composite and used as control. The letters A to F represent different liquid formulations. The powder/liquid ratio of 4/1 was applied. Results are summarized in the following table.

Material

Formulation

CS [MPa] (S.D.)

DTS [MPa] (S.D.)

A

50/50

276.1 (33.2)

35.61 (3.21)

B

70/30

257.2 (36.2)

22.87 (2.22)

C

30/70

263.4 (24.1)

37.79 (6.01)

D

70/30

228.2 (18.1)

17.48 (2.56)

E

50/10/40

245.9 (25.0)

26.33 (4.47)

F

50/40/10

308.7 (30.5)

38.92 (3.86)

FL

-

183.9 (18.9)

20.55 (3.81)

Results show that the newly synthesized oligomers formulated with TEGDMA or TEGDMA/TMPTA-N demonstrated much higher mechanical strengths than the FL. The BPTCDA-GDMA formulated composites were higher in both CS and DTS than the BPTCDA-HEMA composite. The new oligomers have potential to be used as biomedical restoratives such as dental composites or adhesives.


1981 (11278)

Hyperbranched multi-methacrylate with modulated shell chemistry for dental resin. S.R. SCHRICKER*, F. GAO, and B.M. CULBERTSON, Ohio State University, Columbus, USA

Objective: We previously reported that a fully methacrylated hyperbranched polyester polyol (Boltron H-30 by Perstorp Corp.) could be a potential replacement for BisGMA. However, the multimethacrylate failed to have acceptable polymerization shrinkage and viscosity. It was reasoned that it was not necessary for the shell –OH of H30 to be fully methacrylated, which contributes to polymerization shrinkage. Methods: We synthesized multi-methacrylated H30s with half of the -OH groups methacrylated and the other half esterificated by different carboxylic acids, i.e., acetate, propionate, butyrate and isobutyrate. These multi-methacryaltes were blended with TEGDMA (50/50, wt/wt) to formulate dental resins for evaluation, compared to BisGMA/TEGDMA (50/50, wt/wt) as a control. The solution viscosity (h ) before photopolymerization (VLC), linear polymerization shrinkage (LPS), double bond conversion (DC), and mechanical properties such as compressive strength (CS), compressive modulus (E) and flexural strength (FS) and Vickers hardness, were measured. Results:

Sample

h * (P)

LPS* (%)

DC (%)

CS* (MPa)

E* (GPa)

FS* (MPa)

Hardness*

Control

1.62(0.21)

6.69(0.21)

80.8

384 (18)

2.46(0.44)

72.6(3.8)

104 (5)

H30-Ac

0.81(0.10)

3.93(0.41)

84.4

347 (34)

2.34(0.29)

69.5(3.3)

92 (5)

H30-Pr

0.45(0.08)

3.66(0.32)

82.7

275 (38)

1.67(0.18)

67.2(4.4)

42 (5)

H30-Bu

0.13(0.02)

3.71(0.34)

86.2

101 (29)

0.58(0.31)

39.5(3.2)

< 23

H30-iBu

1.07(0.20)

3.27(0.40)

88.3

92 (24)

0.49(0.22)

36.4(2.9)

< 23

*Entries are mean values of six specimen with standard deviations in parentheses. Conclusions: The results show that the partial methacrylated H30 has lower shrinkage but fail to provide needed mechanical strength, due to plasticization of the matrix by the higher aliphatic (C3 and C4) carboxylates on the terminus of the shell branches.


1982 (12909)

Espectroscopy of leached inorganic components from aged dental composites. J. MARTOS1, W. OSINAGA*1, M. TOLEDANO2, and R. OSORIO2, 1 Federal University of Pelotas, Pelotas RS, Brazil, 2 University of Granada, Spain

Objectives: To evaluate the leached inorganic components of four resin composites: Alert (Jeneric-Pentron), Artglass (Heraeus-Kulzer), Belleglass (Kerr) and  Z250 (3M). after aging in distilled water. Methods: Cylindric specimens (8 mm x 2.5 mm) of each material were prepared and polymerized: Alert and Z250 – direct visible light polymerization during 120 s at 400 mW/cm2 (KM-100DR-DMC Co.); Artglass –intense visible light pulsed in unit UniX S (Heraeus-Kulzer) 520 nm/20 Hz during 180 s; Belleglass – photopolymerization with unit Tekliteat 500 nm during 60 s and post-cured with HP curing unit to 138 ºC under pressure (29 lb/pol2) in a nitrogen atmosphere for 20 min. The specimens were stored in sealed propylene vials inert chemically with 10 ml of distilled water, at 37 ºC during 30 and 90 days. Concentrations of Al, Ba, B, Sb, Sr, Si and Mg released into the storage solution were obtained by plasma-emission spectroscopy (ICP/AES. Spectroflame Modula, Spectro Co.). Mean values and standard deviation were calculated for each inorganic element and each material. Results: Mean values (mg/ml) of the different leached elements are shown in the table:

Conclusions: The amount of the inorganic leachables increased with the storage time, except for Z-250. Belleglass and Z-250 showed the smallest levels of inorganic leachables. (Supported by: CICYT. Gran#MAT2001-2843-C02)


1983 (16542)

The influence of additional cassava starch for alginate impression material. B. IRAWAN, Univ.Of Indonesia, Jakarta, Indonesia, and M. FEBRIANI*, Univ.Of.Prof.DR.Moestopo, Jakarta, Indonesia

Objectives:The effect of cassava starch addition to the imported alginate and its ability to reproduce detailed reproduction using type III gypsum.

Methods:120 specimens were divided into 6 groups of study.The percentage comparison of alginate to cassava starch in A1 group to A5 group are 55%:45% ; 52,5%:47,5% ;50%:50% :47,5%:52,5% ;45%:55%.A0 as a control group without the addition of cassava starch.The specimens then being impressed with detail reproduction tool ( ISO 1563/78 ), and the result is then analyzed under a stereo microscope.

Results:The result indicated that there were no significant differences between the alginate impression and modified alginate with cassava starch in 0.05 mm and 0.075 mm in depth.

Conclusions:The alginate impression with cassava starch with ratio up to 47,5%:52,5% can be used as an impression material.


1984 (17331)

Comparing 2 and 3-body wear of dental materials. S. MOLYVDA*, S.L. ROLLAND, and J.F. MCCABE, University of Newcastle upon Tyne, United Kingdom

Objectives: The purpose of this study was to compare 2 and 3-body wear testing of a range of dental materials. Methods: The materials used were Z100 [Z] (3M, hybrid composite), Silux Plus [S] (3M, microfilled composite), Dyract AP [D] (Dentsply, compomer), Vitremer [V] (3M, RMGI), GlassIonomer FX [G1], GlassIonomer Type II [G2] (Shofu, GICs), and Amalcap Plus [A] (Vivadent, amalgam). 2-body wear testing was conducted using the method previously described in Wassell et al (J. Dent. Res., 1994). 3-body wear testing utilised the tooth brushing testing equipment described by the British Standard Specification for Toothpastes (B.S.5136:1974). A profilometer was used to monitor material wear. Results are shown in the Table. Statistically significant differences were identified using ANOVA and Tukeys multiple range test (p<0.05). There was no correlation between wear values found in the two methods. Conclusions: The glass-ionomers tended to perform worse in the 2-body wear test but performed much better in the 3-body test, showing wear similar to that of amalgam and resin-based materials. This indicates GICs would not perform well in stress-bearing situations, but in areas prone to tooth-brushing abrasion, they would perform as well as other materials. Amalgam gave a relatively small wear value in both test methods. In predicting clinical performance it is clearly inappropriate to rely upon a single test method.

Results:

D

V

Z

S

G1

G2

A

2-body wear (m m2*10-3)

53.68b,c (11.07)

61.04b,c(8.46)

74.82b (15.05)

43.5c (4.11)

116.53a(19.18)

69.55b (8.06)

6.09d (1.81)

3-body wear (m m)

19.39a (2.84)

11.50b (2.89)

4.11d (0.87)

8.58c (1.41)

4.24d (1.57)

4.29d (0.85)

5.41d (0.66)

Mean values with same superscript letter in the same row are not significantly different. Standard deviations are the values in parenthesis.


1985 (17442)

Rheological Properties of Flowable Composites and Compomers. G. LARSON, S. JOSEPHS, and E.C. COMBE*, University of Minnesota School of Dentistry, Minneapolis, USA

Flowable composites and compomers are now widely available but there is little information on their rheological properties, which may have important implications for the handling and properties of the materials. In this work four flowable composites and two flowable compomers were studied, using a Dynamic Stress Rheometer (Rheometrics Scientific Inc, Piscataway, NJ) with cone and plate geometry. The materials were studied at 21±1°C, with a light shield to prevent premature polymerization of the pastes during measurement. For each material, the stress that caused shear fracture was determined, and subsequent experiments were carried out well below this figure. In general, creep tests showed a small degree of thixotropy. Plots of log (shear rate) versus log (shear stress) were obtained and subjected to linear regression analysis, to determine flow index (n) and regression coefficient (R2). Experimental data: three composites (Florestore, Den-Mat; Revolution 2, Kerr and Starflow, Danville) and both compomers (Compoglass Flow, Vivadent; Dyract Flow, Dentsply) were pseudoplastic, with n values from 0.34-0.61, but one composite was near-Newtonian (Henry Schein). In all cases R2 ≥ 0.98. Further, the apparent viscosity differed between materials, with Henry Schein material being much less viscous that the other composites, and the Dyract material showing a viscosity an order of magnitude less than the Compoglass product. It was concluded that for both flowable composites and compomers, there are important differences between materials both in terms of viscosity and type of rheological behavior. Supported by Division of Pediatric Dentistry and the Minnesota Dental Research Center for Biomaterials and Biomechanics, University of Minnesota.


1986 (17619)

In vitro Study on the Occlusal Wear of Different Restorative Materials on Primary Teeth. P. VILLALTA*, and C.R.M.D. RODRIGUES, Universidade de São Paulo, Baltimore, MD, Brazil

The aim of this study was to assess the wear of resin composite (Filtek Z250), polyacid-modified resin composite (Dyract AP), resin-modified glass-ionomer cement (Vitremer) and amalgam (Dispersalloy) compare it with that of the enamel of deciduous teeth. This study used healthy labial and/or palatal surfaces of deciduous molars selected from the Human Teeth Bank the Pediatric Dental Department of the University of São Paulo. The surfaces were ground flat but still leaving an enamel surface. After embedded with self-curing acrylic resin into polyvinyl tubes,, cylindrical cavities (3mm deep x 2mm diameter) were prepared in the central area of the surfaces. Following, the cavities were restored with the tested materials. Specimens were submitted to mechanical cycling load up to 400.000 and 800.000 cycles. The results showed that resin-modified glass-ionomer cement, Vitremer, exhibited statistically significantly higher wear than the other materials (p<0.01) that were statistically similar to each other (Filtek Z250=- 2,1mm; Dispersalloy=2,8mm; Dyract AP=9,6mm). The resin composite Filtek Z250 was the unique material that wore less than the deciduous enamel around the restoration, when evaluated after 800.000 cycles. There was not a significant difference between the values of wear reading of the number of cycles.


1987 (17822)

In Vitro Evaluation of Wear of Different Commercial Packable Composite Resins. J.O. LIMA*, P.E.C. CARDOSO, and F.A.J. MORENO, University of São Paulo, Brazil

Objectives: The aim of this study was to evaluate, in vitro, the wear of 5 commercial packable composite resins: Pyramid Enamel/Bisco-USA [PyE], Pyramid Dentin/Bisco-USA [PyD], Solitaire 2/Heraus Kulzer–Germany [SO2], Heliomolar HB/IvoclarVivadent–Liechenstein [HB] , Synergy Compac/Colt&egrave;ne–Switzerland [SYC]. Materials and Method: Twenty cylindrical shaped cavities (n=4) were prepared in extracted human molars. The restorations were placed according to manufacturers' instructions. The specimens were submitted to mechanical loads (8 Kgf) up to 1.000.000 cycles. The wear was measured using the M-L scale and the results were analysed using ANOVA and Tukey’s Test. Results: The results of this study are presented in the table below.

Materials

HB (sd)

PyE (sd)

PyD (sd)

SO2 (sd)

SYC (sd)

Wear (mm)

19 (4) a

13,5 (2,1) a

37,5 (5,2) b

28,8 (11,5) b

39,8 (7,4) b

Conclusions: [HB] and [PyE] presented a higher resistance to wear than the other composite resins tested. According to the results these materials may obtain a better performance under masticatory loads than [PyD], [SO2] and [SYC].

 


1988 (18447)

Radiopacity of different composite resins. M.M.L. EMERENCIANO*1, A.B.L. NASCIMENTO1, H.M. TEIXEIRA1, H. KHOURY2, and M.N. CORREIA1, 1 Pernambuco Dental School - UPE, Recife, Brazil, 2 Pernambuco Federal University - UFPE, Recife, Brazil

Objectives: The aim of this study was to establish the degree of optical density for resins employed in restorative dentistry (A 110 enamel - A110E, 3M; A110 dentin –A110D, 3M; Filtek Z-250- Z250,3M; Solitaire 2 -S2, Kulzer; Flow-it- FI, Jeneric/Pentron) and to compare it with the SDI amalgam’s one. Methods: Five samples of each material were prepared with the following dimensions: diameter of 10mm and thickness of 2mm. To polymerize the samples a Gnatus curing light was used for 40s with 500mW/cm2. A specimen of each material, an aluminum stepwedge and a lead block were placed on Ektaspeed Plus oclusal film and radiographed using an X- ray Spectro II apparatus (Dabi Atlante) at 70 KVp, 10 mA, 0.4s and at the distance film-focus of 40 cm. The optical density (OD) of each sample was measured with an MRA photodensitometer. Results: The average of the OD was obtained with the OD values of the five samples of each resins and it was correlated to the aluminum thickness in mm (Al thick) with equivalent OD. The values of the equivalent aluminum thickness and OD obtained were: Al tick (mean/S.D.): A110E (0.64; 0.037), A110D (0.58; 0.038), Z250 (3.42; 0.48), S2 (2.02; 0.090), FI (2.55; 0.60), Amalgam (16.89; 0.40); OD (mean/S.D.) A110E (0.93; 0.028), A110D (0.95; 0.027), Z250 (0.46; 0.026), S2 (0.60; 0.32), FI (0.54; 0.076), Amalgam (0.0076; 0.0043). Conclusions: All the resin materials showed OD lower than the minimum recommended by the American Dental Association that is the equivalent of 4mm aluminum thickness and amalgam specimens.


1989 (19837)

Microtensile bond strength of bonding agents added microfiller to bovine teeth. J.M. KWON*, H.-Y. CHOI, S.-J. PARK, G.-W. CHOI, and K.-K. CHOI, Kyung-Hee University, Seoul, South Korea

Most of dental practitioner want to use a restorative system that has less technical sensitivity and is simplified procedure in manipulation. Objectives: the objectives of this study was to evaluate the physical properties such as microtensile bond strength and flexural strength of few adhesives varied with microfiller level. The adhesive agent used were self-priming system; Single Bond(SB) and self-etching system; Clearfil SE Bond(CB) and UniFil Bond(UB). Methods: Microfiller particles were added to a bonding agent at various level: 0,5,10,15,20, and 25wt%. Bovine teeth were cut and grind with #600 SiC paper serially and exposed dentin surface. After pretreatment as instruction, experimental bonding agents with microfiller were applied on bovine dentin and composite resin(Clearfil AP-X) for attaching to testing zig was filled and cured in the Teflon mold. After specimens were stored in 37 Celsius for 24hours, vertical slices approximately 1mm thick were made perpendicular to the bonded surface. Each slice was trimmed with high-speed diamond point to make hour-glass shape that the area of adhesive interface was 1mm2. Specimen was attached to microtensile zig placed testing machine(Shimadzu, Japan) and performed test at a CHS of 1mm/min. ANOVA/Tukey¢s test was used to at P£0.05. Results: In the microtensile strength(Mpa), Control group of SB is 27.9, 5% is 27.1, 10% is 35.3, 15% is 37.8, 20% is 41.7, 25% is 22.6, Control group of CB is 36.9, 5% is 44.8, 10% is 49.3, 15% is 45.2, 20% is 39.4 and Control group of UB is 43.1, 5% is 35.1, 10% is 29.9, 15% is 37.4, 20% is 36.2, 25% is 36.7. In all experimental groups higher dentin bond strength were obtained with filler content of 10-20wt% and decreased with filler level more than that. Conclusions: Addition of filler to bonding agent may not only foresee the possibility of self-adhesive restorative material but also simplify bonding procedure.


1990 (21625)

Bonding agent prevents tooth from citric acid attack. R.C. BITHA BEYIDI*1, J. ONANA1, E.M. MENDOMO EYA'ANE1, A. TOHAM1, C. EWO1, G. SEBATIGITA MBE EMANE1, and P. NDOBO-EPOY2, 1 University of Yaoundé, Cameroon, 2 University Victor Segalen Bordeaux 2, France

Objective: The purpose of this in vitro study was to highlight how can bonding agent protects tooth against citric acid attack. Methods: An extracted human tooth served to realize cavity preparation using a cylindrical diamond drill 1mm of diameter, mounted on a turbine (speed 30 000 turns per minute), to obtain a 3 mm deep box. The tooth is transfixed at the apex, using the same drill, this apical aperture serves as a stenopeical passage for a 0.2 mm diameter nylon thread. A whitened Calcium hydroxide «bleu de nil» mixture becoming always blue in acid environment serves as a filling material for the cavity; the scotchbond bonding is rigorously lay-coated on the whole tooth and classically polymerize. This specimen , carefully handled is stored in plastic test tube containing 10 ml of a 25% citric acidic solution. The test tube is closed, stored at environmental temperature, the specimen is submitted in a colorimetrical longitudinal study. Results: The whitened Calcium hydroxide «bleu de nil» mixture remains still white months and months later proving that there is no citric acid attack. Conclusion: We concluded that bonding protects tooth surfaces against citric acid attack.


1991 (14518)

Pressure effects on porosity of dental composites during curing. D. BOSKOCEVIC*, S.J. DURAY, and B.I. SUH, Bisco, Inc, Schaumburg, IL, USA

Objective:  The objective of this study is to demonstrate the effect of pressure on porosity of dental composites during the curing process.  Method:  Pressure curing was accomplished utilizing BISCO’s TESCERA light/heat/pressure curing device for indirect restorations.  The composite  (BISCO Pyramid™ Enamel Translucent) was mixed by hand for 15min to introduce porosity.  Approximately 0.4g of composite was pressed by hand between two glass plates using a shade disk mold as spacer (i.d. 1.15mm, dia 25.0mm).  The pressure of Nitrogen was varied while holding constant the length of time the specimen is held under Nitrogen pressure prior to the light cure/heat cycle (1min @ 20psi, 40psi, 60psi, & 80 psi).  The cured composite disk was removed from the mold and examined under a light microscope for porosity and photographed.  A control sample was cured in a light box (Pro-Lite DLS, Pro-Den Systems, Inc., Portland, OR) at ambient pressure for 5 min.  Results:  The photographs of specimens cured under ambient pressure show many bubbles.  Photographs of specimens cured at increasing pressure demonstrate that the quantity of bubbles decrease with pressure, gradually coalescing into large bubbles.  Photographs of a specimen cured under 80psi pressure revealed no visible bubbles.  Conclusion:  It is possible to remove porosity in a high-viscosity composite by curing it under pressure.


1992 (15528)

Localized Wear of Hybrid and Flowable Composite Resins. M.A. LATTA, B.G. SIMISTER*, and T.M. WILWERDING, Creighton University School of Dentistry, Omaha, NE, USA

Low viscosity (flowable) composite resins have gained popularity for a variety of applications including restoring tooth surfaces in occlusal function. Objectives: The purpose of this study was to evaluate the localized wear of 2 hybrid and 2 flowable resins. Methods:  8 specimens of Tetric Ceram, Tetric Flow, Esthet-X, and Esthet-X Flow  were prepared by polymerizing each resin in a 5mm deep by 6mm diameter  machined cavity in a custom fixture. The specimens were ground flat and polished to a final surface finish of 4000 grit. Conical steel styli were mounted in the spring-loaded piston assembly of a Leinfelder wear apparatus. The pistons were calibrated to deliver a force of 79 N to the resin surface using a counter-rotation motion. Pre-test resin and enamel surfaces were profiled using an MTS 3-D profilometer. The specimens were subjected to 400,000 cycles and re-profiled. Pre-and post-test data sets were compared using ANSURÔ software. Volume loss and maximum depth (height) loss were calculated for each flat resin surface. ANOVA and post-hoc Tukey’s test were used for statistical comparison. Results: (volume in mm3, depth in microns)

 

Volume loss

Max .Depth

Tetric Ceram (T)

0.027 ± 0.011

99.1 ± 14.8

Esthet-X(E)

0.029 ± 0.009

114.5 ± 21.2

Esthet-X Flow (EF)

0.038 ± 0.010

119.9 ± 10.4

Tetric Flow (TF)

0.061 ± 0.020

150.4 ± 18.8

T and E had statistically similar volume loss (p>0.05) but less than EF which was less than TF (p<0.05). TF exhibited the greatest depth compared to T, E and EF. (p<0.05). Conclusions: Both flowable resins exhibited greater wear than their conventional hybrid counterparts. Between the low viscosity materials EF demonstrated less wear than TF.


1993 (15904)

Effect of Spherical Silica's Particle Size on Fracture Toughness. S. KONDO*1, Y. NODASAKA2, T. KAMADA2, and H. SHIMOKOBE3, 1 Private Laboratory, Sapporo, Japan, 2 Graduate School of Dental Medicine, Hokkaido University, Sapporo, Japan, 3 Meirin College, Niigata, Japan

Objective: The objective of this research was to examine the effect of the particle size of spherical filler on fracture toughness for experimental composite resin. Methods: The matrix resin was formulated with 50 mol% urethanetetramethacylate-50 mol% trimethyrolpropane trimethacrylate using visible light initiator system (0.5wt% camphorquinone and 0.5wt% N,N-dimethylaminoethyl methacrylate). The g-methacryloxypropyltrimethoxy silane-treated spherical fillers of various particle sizes from 1.0 to 15 mm in mean particle diameter were used. The filler of 80 % by wt. was incorporated to the matrix resin. The specimen of fracture toughness test was prepared using single edge-notched Teflon mold (length 20, width 5.0, thickness 2.5 and notch length 2.5 in mm) and a precrack was created with fresh cutter blade on the notch bottom. The specimens were stored in a distilled water at 37 Ž for 24 h. The test was carried out for wet specimen at a crosshead speed of 0.5 mm/min in environment at 23 Ž. Fracture toughness values were calculated from maximum fracture load using ASTM E399-1983 equation. The values were shown with mean and standard deviation in parentheses of five specimens. Results: The fracture toughness generally increased with enlarging the particle size of filler. The fracture toughness for 1.0, 8.0 and 15 mm in mean particle diameter was 0.74(0.09) ,1.14(0.14) and 0.99(0.06) MPaEm1/2, respectively. A statistically significant difference was found among their fracture toughness (ANOVA, p<0.05). Conclusion: These results indicated that the silane-treated spherical filler of the limited particle size may improve the resistance of crack propagation due to crack bowing and deflection.


1994 (19573)

Comparing marginal chipping of two flowable composites at 45° and 90° surface angles. R.F. BARNES, P.C. MOON, R.E. BOGACKI, and A. NAIMINEJAD*, Virginia Commonwealth University, Richmond, USA

Objective:  To Compare marginal chipping in two flowable composites at  45° and 90°prep angles made in nylon cylinders to simulate teeth.   The composites tested were Versaflo (V), and Revolution (R).  Methods: The restoration were made by first treating  surface of the nylon with glutaraldehyde and HEMA  for bonding.   Next the composites were VLC and finished with Soflex discs to remove any flash present on nylon surfaces. These simulated restorations were then triturated with 3 ball bearings at each end of the cylinder in a VariMix(L.speed) for 1 to 5 minutes.   The marginal chipping was measured by viewing the cylinder ends in a goniometer and summing the angles where marginal chipping was evident.   Results:  Table1

Table1:  Mean Marginal Chipping (degrees) and 95% confidence interval(T= time,1=45°,2=90°)

T

1Minute

2Minutes

3Minutes

4Minutes

5Minutes

1

R:9.0(5.5-12.2)

V:17.3(9.2-25.4)

R:51.5(41.0-62.0)

V:56.3(44.0-68.5)

R:124.9(108.5-141.2)

V: 140.5(114.3-166.7)

R:211.5(187.6-235.3)

V:248.3(216.6-2800)

 

R:283.8(260.9-306.6)

V:308.2(281.0-335.3)

 

2

R:19.5(12.2-26.8)

V:29.3(22.5-36.1)

R:41.2(34.0-48.3)

V:52.8(39.4-66.1)

R:98.0(81.7-114.2)

V:118.4(99.1-137.6)

R:197.5(183.5-211.5)

V:214.3(194.7-233.8)

R:268.9(242.2-295.5)

V:307.3(270.5-344.0)

 

ANOVA showed that there is significant difference in extent of marginal chipping between 45°and 90°     at 1 , 2, and 3 Minute(s) (p<0.05).  At 1 minute 90° surface margins chipped more than 45°, and at 2and 3 minutes 45°margins showed more marginal chipping.  At 4, and 5 minutes the difference in marginal chipping is not significant between 45° and 90° (p>0.05) Conclusion:  Marginal chipping for 90°is significantly more at 1 minute and significantly less at 2 and 3 minutes as compared to marginal chipping of  45° surface angles.  This study was supported by the A.D. Williams fund and the materials were supplied by the respective Dental Manufacturers.  (R: Kerr, and V: Centrix) 


1995 (19276)

Dehydration shrinkage and water binding characteristics of tooth-coloured restorative materials. S.K. SIDHU*, T.E. CARRICK, and J.F. MCCABE, University of Newcastle upon Tyne, United Kingdom

Objectives: Dimensional changes of restorative materials can have a marked effect on clinical performance. This study assessed the dehydration shrinkage and water binding characteristics of tooth-coloured materials on heating.

Method: 5 cylindrical specimens (6x4mm) were made (using a stainless steel mould) of each of the following: the conventional glass-ionomers Ketac Fil Aplicap (ESPE) [K] or Fuji IX (GC) [F9]; a resin-modified glass-ionomer, Fuji II LC Improved (GC) [F2]; a compomer, Dyract AP (Dentsply) [D]; or a composite resin, Z100 (3M Dental) [Z]. The light-activated materials were thoroughly light-cured. Specimens were stored in distilled water at 37°C for one week. Each sample was then placed on a thermocouple in a Differential Thermal Analyser (Stanton Redcroft, UK), heated from 25 to 150°C at 10°C min-1 and the differential heat in the system recorded, with particular attention up to 60°C. The weight and length of each sample were recorded before and after the heating process (after the sample had cooled to 25°C).

Results: The mean results were:

 

K

F9

F2

D

Z

% dehydration shrinkage

2.8 (0.2)a

3.4 (0.3) a

2.4 (0.1) a

0.2 (0.2) b

0.2 (0.1) b

% dehydration weight loss

7.9 (0.4) a

7.6 (0.5) a

6.6 (0.5) a

0.5 (0.4) b

0.6 (0.3) b

Endothermic heat of water loss up to 60°C (mJ/mg)

3.8 (0.2) a

2.1 (0.6) a

0.6 (0.9) b

0.0 (0.0) c

0.0 (0.0) c

1-way ANOVA and Tukey’s pairwise comparisons indicated significant differences between materials for each property. (The superscripts refer to mean values which are not significantly different). The glass-ionomers were significantly different from the other materials in terms of each property.

Conclusion: Glass ionomers contain labile water which is partly lost at temperatures below 60°C, resulting in shrinkage.

 


1996 (8606)

Radiopacity of Flowable and Posterior Dental Composites. S. TOLBERT*, X. XU, J.O. BURGESS, and K. THUNTHY, Louisiana State University Health Science Center, School of Dentistry, New Orleans, USA

Restorative composite resin must have adequate radiopacity to be distinguished from radiolucent caries around the restoration. According to ISO Standard, dental composite must have radiopacity twice of aluminum. The radiopacity of flowable composites is questionable because of their low filler content. Objective: This study measures the radiopacity of 5 flowable composites and 4 posterior composites. Methods: 6x10x2 mm rectangular specimens (n=6) mm were made in brass mold; light cured for 40s and ground with 1200 grit SiC paper to 2.00 mm thick. The specimens were then photographed along with an aluminum step-wedge (Nuclear Associates) having 15 steps of 0.4mm. The X-ray unit was operated under 70 KV and 10 mA at a target-film distance of 40 cm. The radiographic density of developed films was measured with a transmission densitometer (Macbeth TD502, Macbeth). The radiopacity value of the composites was determined as thickness of equivalent aluminum based on the fitted calibration curve using the step-wedge. The data was analyzed using One-way ANOVA post hoc. Results:

Materials

Tetric Flow

Revolution

Flow It

Matrixx Flow

Synergy Flow

Radiopacity (SD)

5.65 (0.07)

2.15 (0.10)

3.17 (0.13)

2.71 (0.17)

2.09 (0.14)

Materials

Matrixx P

Surefil

Prodigy

P60

 

Radiopacity (SD)

3.31 (0.12)

4.76 (0.30)

4.35 (0.26)

5.74 (0.14)

 

Conclusion: in general,the radiopacity of flowable composite resins is significantly lower than posterior composite resins and may not meet the standard requirement. However, Tetric Flow is an exception. Supported by Discus Dental, Inc.


1997 (20101)

In Vitro Wear and Toothbrush Abrasion of Flowable and Posterior Dental Composites. X. XU*, X. XIN, J. WEATHERSBY, and J.O. BURGESS, LSUHSC School of Dentistry, New Orleans, LA, USA

Objectives: the objectives of this study were: 1) to evaluate the wear resistance of flowable and posterior dental composites using an in vitro three body wear tester (Leinfelder simulator, Caulk/Dentsply) and a toothbrush machine; 2) to investigate the correlation between the two in-vitro test methods. Methods: Five flowable composites and four posterior composites were placed into cylindrical cavities 4x3 mm prepared in Macor disks (Ceramic Products) following the manufacturer’s instructions. The specimens were finished with 5-micron alumina slurry. Eight specimens of each material were used in each wear and toothbrush abrasion test. The wear test was conducted using a polymer beads slurry (15g+9ml H2O) and 8kg pressure for 400,000 cycles (50 hrs). The toothbrush abrasion test was conducted using a pumice slurry (30g fine Mayco pumice+120ml H2O) and 300g pressure for 10800 cycles (1 hr), during which the specimens were changed to different stages and rotated 90 degrees every 2700 cycles (15 min). The lost volumes and maximum wear depths were measured by a 3D profilometer (TalyScan 150, Taylor Hobson). The data were analyzed using a two-way ANOVA and Tukey’s B tests. Results: the Wear volumes (SD) (mm3) were:Flow-it 0.169 (.041), Matrixx Flow 0.199 (.127), Revolution 0.161 (.025), Synergy Flow 0.092 (.030), Tetric Flow 0.096 (.032), Matrixx P 0.054 (.015), P60 0.023 (.015), Prodigy 0.032(.011), Surefil 0.013 (.004). The toothbrush abrasion volumes (SD)(mm3) were: Flow-it 0.965 (.410), Matrixx Flow 0.969 (.367), Revolution 0.696 (.111), Synergy Flow 1.06 (.182), Tetric Flow 0.946 (.126), Matrixx P 1.12 (.300), P60 0.235 (.069), Prodigy 0.676 (.139), Surefil 0.071 (.056). Conclusion: Flowable composites have significantly less wear resistance than posterior composites (p<0.05). Toothbrush abrasion can generate wear more efficiently than Leinfelder simulator (p<0.05). There is little correlation between the two methods (r2=0.161). Supported by Discus Dental, Inc.


1998 (9987)

Shade Effects on Flexural Properties and Impact Strength of Microhybrid Composites. J.C. ONTIVEROS, M. WARD*, and J.M. POWERS, University of Texas Dental Branch at Houston, USA

Objectives: The purpose of the study was to compare the flexural strength (FS), flexural modulus (FM), and impact strength (IS) of a translucent enamel shade, a dentin shade, and a white opaque shade of two commercial microhybrid composites; CE, A3, WO-Esthet-X (Dentsply/Caulk), and TF, A3, OS -Vitalescence (Ultradent). Controls were a microfill, UO-Silux Plus (3M ESPE) and a hybrid composite, A3-Herculite XRV (SDS Kerr). Methods: All tests were conducted according to ISO specifications. Specimens of each shade were made (n=8) for a total of 24 groups and 192 specimens. Specimens were stored in water at 37°C for 24 hours before testing. Results: Mean values are listed.

Material

Shade

FS (MPa)

FM (GPa)

IS (J/m)

Herculite XRV

A3

142 (25)

10.7 (1.7)

1.9 (0.3)

Silux Plus

UO

69 (8)

6.6 (0.3)

0.6 (1.4)

Esthet-X

A3

132 (11)

10.8 (0.5)

1.9 (0.3)

Esthet-X

CE

125 (27)

10.9 (1.0)

1.8 (0.2)

Esthet-X

WO

126 (16)

11.8 (0.5)

5.4 (3.2)

Vitalescence

A3

145 (13)

10.0 (0.5)

5.0 (1.6)

Vitalescence

TF

150 (10)

10.4 (0.7)

4.5 (1.1)

Vitalescence

OS

150 (17)

10.0 (0.7)

3.8 (1.2)

Data were analyzed by two-way ANOVA. Tukey-Kramer intervals (p=0.05) for comparisons among 3 shades and between 2 composites were 1.4 and 1.0 J/m for IS, and 0.6 and 0.4 GPa for FM. The Tukey-Kramer interval for comparisons between 2 composites for FS was 10 MPa. Conclusions: The results showed that shade affected FM and IS but not FS of two commercial microhybrid composites. This study was supported by Dentsply/Caulk and Ultradent.


1999 (16037)

Effect of Light-Barrier and Pigment on the Microhardness of Composite Resins. E. MONDRAGON*, V.V. GORDAN, C. SHEN, and I.A. MJÖR, University of Florida, Gainesville, USA

Objectives: This study tested the hypothesis that light-barriers and the pigment used for shades can affect the microhardness values of composite resins.

Methods: A 10-mm glass-cylinder (3mm diameter) with sidewall shielded from room light was used to prepare 18 specimens each from a pre-reacted glass ionomer filler (PRG) bonded resin, Beautifil (shade A1 and C3; Shoufu Inc.), and a resin-based composite (RBC), Z-100 (shade A1 and C4; 3M/ESPE Dental Products). The specimens were polymerized using a light source (Optilux-VCL401) spaced 2mm from one side of the cylinder (top). Curing conditions included (a) the light tip wrapped with a plastic barrier, (b) same as (a) with additional Mylar strip on the composite surface, and (c) no barrier or Mylar strip was used. The light output of each condition was measured with a radiometer (Optilux-100). The polymerized specimens were polished longitudinally through 1200-grit to expose the center portion of the specimen for Vickers microhardness measurement. Indentations were made within 0.1mm from the top of cylinder. Six additional indentations were made 0.5mm apart toward the bottom of the cylinder. Each experiment was repeated in triplicate.

Results: Hardness values of all specimens tested decreased exponentially with the depth. Analysis of variance shows that RBC exhibited higher hardness values than PRG (p<0.0001), lighter shade specimens are generally harder than those of darker shade for both materials but are statistically significant only near surface layer of RBC, and curing condition had a significant influence (p<0.0001) on the microhardness (c,a>b for RBC and c,b>a for PRG). The light output was 447, 477 and 580 mw/cm2 for curing condition a, b and c, respectively.

Conclusions: Light-barriers reduced the energy delivered to the specimens. The two materials differed considerably in their response to variation in light intensity. Darker shade reduced hardness values but significantly only near the surface of curing.


2000 (10607)

Novel Fluorescence Method for Cure Monitoring of Photo-Cured Composites. K. KOMATSU*1, F.W. WANG2, and K. NEMOTO1, 1 Nihon University School of Dentistry at Matsudo, Matsudo, Chiba, Japan, 2 National Institute of Standards and Technology, Gaithersburg, MD, USA

Objective: The mechanical properties of a composite resin depend greatly on the degree of its conversion.  This study used a fluorescence monitoring system to investigate the dependence of the conversion of a photo-cured composite resin on its filler content.  In this system, a curing light was used not only to cure the composite resin but also to excite a fluorescent probe dissolved in the resin.  Method: The photo-cured composite resin was prepared from spherical silica particles [mass fraction: (20, 40, 60 or 80) %] and a mixed monomer (Bis-GMA and TEGDMA, mass ratio of one) containing a photo-initiator (CQ and EDMAB) and a fluorescent probe (AHPBS).  The composite resin was placed in a cylindrical cavity (6 mm in diameter and 4 mm in depth), and its fluorescence was detected at the distal ends of the optical fibers (0.5 mm in diameter) located at the center and at the edge of the composite resin.   After the exposure of the composite resin to the curing light for 100 s, the fluorescence spectrum of the fluorescent probe, excited at 460 nm by the curing light, was measured with a spectrometer.  Result: The ratio of the fluorescence intensities at 622 nm and 718 nm decreased with increasing filler content of the composite resin for both detection positions.  This result indicated that the conversion of the monomer in the composite resin decreased with increasing filler content because the attenuation of the curing-light intensity by silica particles depended on the filler content of the composite resin.  Conclusion: It was concluded that the degree of conversion of a photo-cured composite resin depended on its filler content.


2001 (15435)

Color Changes of Anterior Restorative Materials Before and After Polymerization. R.D. WILSON*, D.C.N. CHAN, and W.D. BROWNING, Medical College of Georgia, Augusta, USA

Objectives: This investigation evaluated the color change of two anterior composites before and immediately after polymerization, then at 30 minutes and 7 days storage in water. Methods: Eleven shades of Esthet.X (Dentsply/Caulk) and 12 shades of Vitalescence (Ultradent) were analyzed. Transparent molds in the shape of tooth#10 were made from 0.9mm thickness Sof-Tray sheets (Ultradent). Three teeth specimens were fabricated from a single mold for each shade. The differences in the lightness coordinate (L*), red-green and yellow-blue chromaticity values (a*, b*) were determined by an intra-oral spectrophotometer (Chromident, JJL Technologies). Both facial and lingual measurements were taken. Immediate post-cure is used as the reference for all Delta E calculations. Results: Delta E and Standard Error of the Mean (SEM) for all different shades and at different time intervals are summarized as follows:
 

Manufacturers

Before Polymerization

Immediately After Polymerization

30 min

7 days

Esthet.X

Dentsply

/Caulk

7.36 (1.653)

Reference

3.43 (1.653)

10.92 (1.653)

Vitalescence

Ultradent

14.47 (1.583)

Reference

3.03 (1.583)

7.25 (1.583)

Results were analyzed by two way repeated measure ANOVA and Tukey post hoc tests (alpha=0.05). Conclusions: There is not a significant difference with materials. Time (p<0.001) and Material X Time (p=0.006) is statistically significant. Perceivable color changes are evident at all time periods. Color mock-up is advised for shade selection for complex esthetic cases.


2002 (19010)

Extension of the total energy concept by curing efficiency. M. HARTUNG*, and R. KUERSCHNER, 3M ESPE AG, Seefeld, Germany

Objectives: The aim of this study was to evaluate , whether the total energy (TE) concept for lightcured restorative materials could be extended to consider different spectra of light curing units (LCU). Methods: Depth of cure values (d) of Filtek Z 250, A 3.5 (3M ESPE) have been evaluated according to ISO 4049 from samples with 4 mm diameter, cured at fixed TE in the range of 5 and 30 J/cm² with a halogen and a light emitting diode LCU (TL, Elipar TriLight, 3M ESPE and CL, prototype of a corded LED LCU). Results: The following means of groups (5 samples each) for TL and FL respectively have been found each TE (units of TE: J/cm² and d: mm). 5: 1.88(0.03), 2.17(0.05); 10: 2.18(0.05), 2.53(0.07); 15: 2.44(0.09), 2.83(0.04); 20: 2.71(0.06), 3.01(0.04); 25: 2.84(0.05), 3.19(0.04); 30: 3.01(0.03), 3.27(0.04). As tested by ANOVA the means for each TE were statistically different (p<0.01). Best fit for the d vs. TE dependence was found with a logarithmic model by means of regression analysis with two separate curves for both LCU. Now the TE were replaced by an effective TE (ETE), that was defined as TE times a theoretically predicted LCU specific efficiency factor E, obtained from the convolution integral of the spectral emission spectrum with the camphoroquinone photoinitiator absorption. For TL a E-value of 0.51 and 0.82 for CL was found. The d vs. ETE dependence could now be described with the same regression curve for both LCU at a confidence level of 95 percent. Conclusions: With the modification of the TE concept by a spectral efficiency factor E the LCU specific spectral efficiency can be considered. TE alone is not sufficient to predict the curing capability of the tested LCU. A significantly higher spectral efficiency of CL was found.


2003 (19556)

Comparison of Tooth Colored Restoratives Using a VITA Shade Guide. B.M. OWENS*, J. KALMOWICZ, and K.L. ARHEART, University of Tennessee, Memphis, USA

The purpose of this in-vitro study was to compare shade changes of tooth colored restorative materials using a VirtuosoÔ (Den-Mat) xenon (VX) arch polymerization light (3 second cure time) and a SheinÔ (Shein-Sullivan) standard, visible (SV) polymerization light (40 second cure time). A VITAÔ (H. Rauter GmbH & Co.) shade guide was used as the control for comparison. Light (high color value, low chroma) and dark (low value, high chroma) shades of five tooth colored restoratives were evaluated by 50 dental personnel for shade changes. A 5-point scale was used for the shade matching (1=very poor shade match: 5=excellent color match). Tooth colored materials included: 1) Z-100Ô (3M Dental Products) hybrid composite (C1), shades A1 and A4. 2) VitalescenceÔ (Ultradent, Inc.) (C2) hybrid composite, shades A1 and A4. 3) Fuji II LCÔ (GC America) resin modified glass ionomer (GIC), shades A1 and A3.5. 4) SynergyÔ (Coltene/Whaledent, Inc.) compactable composite (C3), shades A1 and A4, and 5) Dyract APÔ (Dentsply/Caulk) compomer (AP), shades B1 and A4. Results from the study indicate that: 1) Using the SV curing light the C2 (dark shade) had a significantly (p<.001) better shade match than all other composites. 2) when using the SV light the C2 (light shade) had a significantly (p<.001) better shade match than C1, a significantly (p=.005) better shade match than GIC, a significantly (p<.001) better shade match than C3, and a significantly (p<.001) better shade match than AP, 3) using the VX curing light the C2 (dark shade) had a significantly (p<.001) better shade match than GIC, C3, and AP, but not a significantly (p<.111) better shade match than C1, and 4) using the VX light the C2 (light shade) had a significantly (p<.001) better shade match than GIC, C3, and AP and a significantly (p<.007) better shade match than C1. Conclusion: C2 works equally well with the SV and VX curing lights. The compactable composite (C3), displayed lesser shade matching abilities when using both the SC and VX lights. This study was supported by Den-Mat Corporation.


2004 (11619)

Utilizing gas pycnometer for measuring polymerization contraction of composite resins. R. CILLI, A. PRAKKI*, and M.A.J. ARAÚJO, PAULISTA STATE UNIVERSITY AT SÃO JOSÉ DOS CAMPOS - UNESP, BAURU, Brazil

Objectives: The objective of this laboratory study was to evaluate the volumetric contraction of five current composite resins: Durafil VS (Heraeus-Kulzer), Z100, Z250, P60 (3M Co.) and Surefil (Dentsply). A helium gas pycnometer (Micromeritics, Norcross-USA) was used to determine the volume of specimens prior to and after photo polymerization from which total volumetric contraction was obtained.

Methods: The non-polymerized resin was previously weighed in an analytic balance (Ohaus Analytical plus, Switzerland), inserted in the pycnometer chamber, the volume of which is known, and hermetically sealed. The volume of the specimen was determined by measuring the pressure change of helium when it was opened up to the specimen chamber. In this study, 15 cycles of pressurizing were done for initial volume determination, for each specimen. The arithmetic mean of volume was obtained. Out of the chamber, the resin composite specimens were then polymerized in increments and weighed again. The final volume was evaluated by the pycnometer as done before.

The percentage contraction (P) was calculated by:

SV=Volume /mass and P=SVi - SVf / SVi

Where SV is specific volume and the suffixes i and f indicate the initial and final measurements, respectively.

Results: The percentage values obtained are shown in the following table:

Composites

Durafil VS

Z100

Z250

P60

Surefil

P

2,40%

1,97%

0,56%

3,26%

1,11%

The standard deviation of percentage contraction is ± 0.3%

Conclusion: The helium gas pycnometry is a simple method to evaluate polymerization contraction of composites resins. The Z250 (3M) composite presented the least percentage contraction among five materials examined.


2005 (18868)

Bleaching effect found in discolored resin-based restoratives in vitro. R. NISHIURA*1, S. NOMURA1, S.L. ROLLAND2, Y. MOMOI1, and A. KOHNO1, 1 Tsurumi University School of Dental Medicine, Yokohama, Japan, 2 University of Newcastle upon Tyne, United Kingdom

Objectives: Bleaching effect using a dual activated bleaching system was evaluated for nine resin-based aesthetic restoratives which were discolored beforehand by a long-term immersion in staining solution. Methods: Disc shaped specimens were prepared of two resin composites (Z100/3M, Herculite XRV/Kerr), two compomers (Dyract AP/Dentsply De Trey, F2000/3M), two resin-modified glass-ionomers (Fuji II LC/GC, Vitremer/3M), and three polymer ceramics (Estenia/Kuraray, Gradia/GC, Artglass/Heraeus Kulzer). All specimens were immersed in stain solution (coffee) for 4 months after which they were removed from the solution, rinsed thoroughly under the running water and placed in an ultrasonic bath for 30 seconds and dried again shortly prior to color measurement. Discoloration of each restorative was evaluated based on CIELab color system. All restoratives (n=9) showed observable discoloration after the immersion in which the mean (S.D.) of the color difference (‡™E) was 3.7 (0.2) for Z-100, 3.8 (0.8) for Herculite, 6.7 (1.3) for Dyract, 4.1 (1.5) for F2000, 6.9 (1.7) for Fuji II LC, 11.5 (1.0) for Vitremer, 3.2 (0.4) for Estenia, 3.8 (0.8) for Gradia, 6.5 (1.8) for Artglass. All discolored specimens were then bleached with the dual activated bleaching system (Hi Lite, SHOFU INC., Japan). After bleaching, specimens were rinsed under the running water and dried shortly prior to color measurement. Results: Mean (S.D.) of color difference after bleaching was 0.8 (0.2) for Z100, 2.0 (0.9) for Herculite, 4.1 (1.0) for Dyract, 6.1 (1.2) for F2000, 3.4 (0.8) for Fuji II LC, 9.5 (0.7) for Vitremer, 3.6 (1.2) for Estenia, 1.5 (0.4) for Gradia, and 3.4 (0.9) for Artglass. Color difference (‡™E) was the greatest in one of resin-modified glass-ionomers which was followed by compomers. Conclusions: Bleaching effect was found for all restoratives tested and was significant (‡™E >3.3) for resin-modified glass-ionomers, compomers and polymer ceramics except Estenia, but not for resin composites.


2006 (19036)

Changing Shrinkage Polymerization Vector. R.Y. BALLESTER*, L.L. FRANCO, A.D. LOGUERCIO, and M. SCHROEDER, University of São Paulo - Dental Materials, Brazil

 

 

Objective:To demonstrate the existence of shrinkage polymerization vector which direction and/or modulus change according to direction of the light activation beam and the bonding resistance to the cavity walls.  Methods:The %LPS of a composite resin (Herculite XRV, shade A3 ‑ Kerr) was evaluated according to: 1) activation light direction and  2)  application of silane or not on the 2 glass walls which contained the specimen.  2 mm edge cubic specimens, were irradiated with light intensity 600 mW/cm2, for 40s. The light beam incised  in the same direction, or perpendicular to the %LPS measurement direction (n=5) by means of an extensometer (Instron). Results: The  %LPS values at 5 min were treated by ANOVA and Tukey test (a=0,05), which have shown significant  differences for both, the main factors and their interaction. The results are listed in the table (mean ± SD). Same letters mean statistical similarity

% LPS

Axial

Perpendicular

silanized

1.14 ± 0.11 (bc)

1.34 ± 0.08 (a)

not silanized

1.25 ± 0.11 (b)

1.71 ± 0.11 (a)

Conclusion: The activation light direction and glass walls silanization have influenced the %LPS, in the direction it was measured. Supported by CAPES and FAPESP grants 00/005500-0 and 99/05124-0.

 

 

 


2007 (19673)

Color Stability of Composite Resins Cured with Two Techniques. B. COMEAUX*, J.O. BURGESS, and L. LI, LSUHSC School of Dentistry, New Orleans, LA, USA

The pulse delay curing technique has been advocated to polymerize composite resin and reduce stress; however this technique may affect color stability of the cured resin. Objective: This study examined the color stability using a Chroma Meter 201 to measure the L*, a*, b* values of three composite resins cured with a VIP curing light (BISCO) using the pulse delay technique compared to the E light (GC America) turbo cure for 40 sec. Each specimen (n=7) was tested for color values immediately after curing, after dark storage for 5 days and after 24 hours in a color stability tester. Methods: Disks (3 X 5 mm) of each composite resin restorative material were made in split molds, covered with a Mylar strip and glass slide and cured using the pulse delay technique (Z100-A2) for 3 seconds at 100mw/cm2, 5 minutes later cured for 30 sec at 500mw/cm2; Tetric Ceram A shade- cured for 3 seconds at 200, 5 min later cured for 30 seconds at 500; Synergy Super White shade, cured for 3 sec at 200, 5 min later cured for 30 sec at 500. After polymerization L*, a*, b* values were determined for all specimens. The specimens were stored for 5 days in the dark and L*, a*, b* values again were measured. The specimens were placed in a Color aging machine for 24 hours and the specimens exposed to UV light and heat L*, a*, b* values were again measured. ANOVA for Repeated Measures and Tukey B tests were used to determine inter-group differences. Results: Curing light technique was not a significant factor (p>.05), L* increased after accelerated aging (p<.05), Conclusion: Curing technique does not affect color of composite resin.


2008 (17246)

Interactive effect of UV light and humidity exposures on color changes in restorative resins. S. JORDAN1, J. VAIDYANATHAN1, T.K. VAIDYANATHAN1, R. MEHRA*1, and A. PRASAD2, 1 UMDNJ-NJ Dental School, Newark, NJ, USA, 2 JENERIC/PENTRON, INC, Wallingford, CT, USA

Objectives: The objective of this investigation was to characterize the interactive colorimetric changes in selected dental resin formulations due to humidity and UV light exposures. Methods: The compositions of three light cure resins studied were R1: PCBisGMA/EBPADMA/TEGDMA  (30:50:20 percent ratio), R2: EBPADMA/BisGMA/TEGDMA (30:50:20) and R3: EBPADMA/ PCDMA (70:30). 20 mm dia x 2mm thick disk specimens were cured in stainless steel molds between glass slides by light exposures (in quadrants) from an ESPE Elipar light source operating at 400 mW/cm2. A sample size of N=3 was used in the study. Nine specimens were prepared for each formulation and divided into three groups. Two groups of specimens were subjected to two 24 hr exposure cycles of humidity (H) and UV light (U) exposures: one group in the H, U sequence (HU group) and the second group in U, H sequence (UH group). A Minolta Chromameter CR 221 was used to evaluate color changes after each of H and U exposure steps for both groups as well as for cumulative effect (C) of treatments. One group was used as untreated control for visual comparisons with the treated groups. The changes in L*, a* and b* as well as overall color changes (DE) were analyzed by ANOVA. Results: The mean DE for the three resins were: (HU) group: H effects: 1.03, 1.57, 1.76; U effects: 4.09,4.36, 6.59; C effects: 3.94, 3.91, 4.83;(UH) group: U effects: 2.65, 2.56, 3.70; H effects: 0.33, 0.78, 0.61; C effects: 2.48, 2.51, 3.09. The results revealed significant main and interactive changes in CIE L*a*b* color space due to treatment and formulation variables (p<0.05). Conclusions: The results indicate greater UV effects than H effects on color changes, and this suggests that secondary cure and de-polymerization (such as scission of molecules) from UV exposure may contribute to color changes.


2009 (19840)

Effect of Surface Finishing and Storage Solution on Color Stability of Composites. S.B. PATEL*, V.V. GORDAN, A.A. BARRETT, and C. SHEN, University of Florida, Gainesville, USA

Objectives: This study tested the following hypotheses: 1) finishing treatments affect the staining of composites (RBC); 2) the unfilled (UR) component is the most susceptible to staining; 3) polishing removes staining. Methods: A total of 54 RBC and 54 UR discs (3M/ESPE) were prepared using a polyethylene mold (2.4mm thick x 16.7mm dia.), polymerized through a Mylar® strip and divided into three treatment groups: 1mm Al2O3 slurry (AL); 15mm Diamond (DD) and Mylar strip (ML). Specimens were immersed in water at 37ºC for 2 days and transferred to one of the following storage solutions for additional 7 days at 37ºC: coffee (F), cola (K) or red wine (W). After immersion, specimens were polished with 1mm Al2O3 slurry. CIELAB color was recorded with a Minolta CR-300 colorimeter before immersion, 1 and 2 days in water (W1, W2), 1, 2, 3, and 7 days in solutions (S1 to S7) and after polishing (PP). CIELAB color difference parameters DE, DC, DL, Da, and Db were calculated. Results: The trend of color changes was very similar at each measurement. ANOVA of the changes between W2 and S7 shows that finishing and storage solution had significant influence (p<0.0001) on the DE: ML(6.0±1.4)>DD(2.7±0.6)>AL(1.7±0.5) and W(5.5±1.0)>F(3.8±1.0)>K(1.1±0.5) for RBC, and DD(2.7±0.9), ML(2.7±0.6)>AL(1.7±0.4); W(2.9±0.9)>K(2.56±0.4)>F(1.8±0.6) for UR. Similar significance was observed for other parameters. Initial finishing also affected the final staining removal (p<0.0001), the effectiveness was in the order of ML>DD,AL for RBC and DD>AL> ML for UR. The largest shift in DL occurred on S2 and S3. Conclusions: These results indicate that finishing treatments and solutions significantly affect the surface staining of RBC materials. RBC Mylar finishing and red wine produced the highest amount of color change after 7 days. Polishing reduced the stain, however it was still perceivable to human eye (DE>1).

Supported by Center for Dental Biomaterial, UFCD, and 3M/ESPE Company.


2010 (21243)

Fluoride Varnish Effect on Hue and Value of Restorative Materials. J. AUTIO-GOLD*, and A.A. BARRETT, University of Florida, Gainesville, USA

Fluoride varnishes used as caries preventive applications deposit an adherent film resulting in possible temporary changes in color of restorative materials. Objective: This in vitro study measured the effect of four fluoride varnishes on color for two hybrid composites and one glass-ionomer after two fluoride applications. Methods: Discs (10mm X 2mm) were prepared using a teflon mold. The materials and shades were: Z100TM (3M Dental Products, St. Paul, MN)(A1, A2) and Esthet-X (Dentsply Caulk, Milford, DE)(A1, A2); GC Fuji IX GP Fast (GC Corporation, Tokyo, Japan)(A2). Specimens were divided into five treatment groups (n=15). Untreated specimens were incubated in Fusyama artificial saliva (FAS) at 37ºC for two days. Duraphat®(DP) (Colgate Oral Pharmaceutical Inc., Canton MA, USA), CavityShield®(CS) (OMNII Oral PharmaceuticalsTM, West Palm Beach, FL, USA), Duraflor®(DF) (Pharmascience Inc. Montreal, Canada) and FluorProtectorTM(FP) (Vivadent, Ivoclar North America, Amherst, NY, USA) were applied to specimens (FV1). Controls were not treated. All specimens were incubated in fresh FAS at 37ºC for 1d (FV1), cleaned and the process repeated (FV2). After FV2 the specimens were cleaned using an electronic toothbrush. CIE L* a* b* measurements were taken at baseline, and after 2d-FAS, FV1, FV2 and brushing using a Minolta CR-300 tristimulus colorimeter with an 8 mm aperture (Ramsey, NJ, USA). Calculations were performed for CIE parameters; DE, DL*, Da*, Db*, DC*. Results: After brushing, the statistically significant changes (ANOVA) were found only with DP in following groups when compared with control: Z-100A1 (DE=1.5±0.11, p=0.002), Z-100A2 (DE=2.53±0.93, p=0.007), FA2 (DE=2.53±0.93, p=0.007), EA1 (DE=1.10±0.35, p=0.02), EA2 (DE=2.53±2.87, p=0.03) with DP. Also, both FA2 and ZA2 had DL>-1, indicating a significant decrease in value. Conclusions: DP caused perceptible, yet clinically acceptable color changes (DE<3) in tested composites and glass-inomer. Fluoride varnishes can be used without adversely affecting the hue and value of restorative materials.


2011 (12268)

TMA dilatometry method for monitoring curing shrinkage of an unfilled resin. N.C. SHAH*, and R.L. SAKAGUCHI, Oregon Health & Science University, portland, USA

Objective: To develop a method for measuring curing shrinkage of an unfilled resin during light activation and polymerization. The hypothesis to be tested was that curing contraction is initiated simultaneously with light exposure. Methods: 5.0mm OD borosilicate glass cylinders (n=5) were bonded to 4mm glass plates with cyanoacrylate and placed on the quartz stage of a thermomechanical analyzer (TMA 2940, TA Instruments, New Castle, DE, USA). The glass cylinders were filled with 25mm3 of a 50:50wt% blend of BisGMA/TEGDMA resin. A 2.83mm quartz dilatometer probe recorded displacement of the top free surface of the cylinder at 1Hz during light exposure (VIP, Bisco, Inc, Schaumburg, IL, USA) for 60s, 36J/cm2. Sampling frequency was 1 per sec. Displacement was monitored for 5min. Results: Contraction strain was observed immediately after light activation. A constant, maximum, shrinkage rate continued for the first 21.6s during light exposure (linear regression r2=0.964, 0.117 + .004 mm/mm per min). The net contraction at 5min after light activation was 6.4% + 0.14. Conclusions: TMA dilatometry provides a simple method for monitoring cure shrinkage of an unfilled resin that is difficult to achieve using methods designed for filled composites. Contraction is simultaneous with light exposure and continues at a constant, rapid rate for over 20s during light activation. This project was supported by NIDR DE09431. Email: shahn@ohsu.edu.


2012 (15038)

Characterization of resin composites polymerized with the same energy density. Y.L. WU*, W.Y. TSENG, M.H. CHEN, and R.S. CHEN, National Taiwan University, Taipei, Taiwan

Objective: By the new development of curing units, there are different curing modes be designed. The purpose of this study was to investigate the relationships between the curing modes and polymerization shrinkage, microhardness of resin composites. Methods: Forty strain gauges (EA-00-031DE-350, Measurements Group, Inc., Raleigh, NC, USA) and sixty four resin specimens (Prodigy® and Heliomolar®) were cured by one of the modes as following: I. Conventional (XL3000): 40 sec at 400mW/cm². II. Boost (Apollo 95E): 13.3 sec at 1200 mW/cm². III. Soft-start (Optilux 501): initially at 100 mW/cm², increasing exponentially to 1000 mW/cm² in thefirst 10 sec. Remains at 1000 mW/cm² for the final 10.5 sec. IV. Pulse activation (Elipar Trilight): 2 sec at 400 mW/cm², a 5-minute hiatus and an additional exposure of 19 sec at 800 mW/cm². The data were subjected to ANOVA, t-test at a level of significant of p=0.05.

Result:

 

Hybrid type (Prodigy®)

Microfill (Heliomolar®)

Modes

Top (KHN)

Bottom (KHN)

Stress (ue)

Top (KHN)

Bottom (KHN)

Stress (ue)

I

54.85+1.89 A

47.86+5.45 a

2520+932 *

26.95+1.64 P

20.44+1.84 p

2254+602 *

II

40.93+2.23 C

43.47+6.96 a

2243+800 *

24.09+1.41 Q

23.02+3.15 p

2101+484 *

III

49.64+2.96 B

43.02+2.66 a

1791+200 *

25.50+3.29 PQ

15.67+1.03 q

2219+438 *

IV

41.63+2.57 C

35.83+1.47 b

2490+783 *

23.58+1.60 Q

14.85+1.93 q

2047+334 *

Conclusions: With the same energy density(16000mJ/cm²), various curing modes resulted in the same shrinkage stress but different shrinkage dynamics and penetration ability. 510@ms60.url.com.tw

 


2013 (16759)

Depth of cure of different curing devices: a function of time and power. M. GAGLIANI*, L. STROHMENGER, and J.M. RITZMANN, University of Milan , school of dentisty, milan, Italy

Depth of cure of different curing devices: a function of time and power

M.GAGLIANI , L.STROHMENGER, J.RITZMANN

(University of Milan, School of Dentistry, Italy).

 

Objectives: Recent studies showed that the depth of cure perfomed with high power curing devices was lower compared to the results obtained by traditional curing devices. In this study the depth of cure was investigated as a function of curingtime and power of the curing device.

Methods: Three curing lamps a halogen lamp (Heliolux, Vivadent ), a plasma arc lamp (Qlight, Rotan Industries) and a micro-xenon based lamp (Aurys, DegreeK )were compared in the study. 60 - three millimeter thick - samples of composite resin,  30 samples of Enamel plus (Vitalescence)( Micerium, Ita) and 30 samples of P60 (3M, USA) were prepared using a plastic mold and divided into 6 groups of 10 samples each. Two Pasma groups were cured for 6s and 10s , the Xenon goups for 10, 15 and 20s and the Halogen group for 40 sec. Samples were stored in saliva at 37°C in the darkness for 24 h and then tested with a microhardness device to measure Vickers Hardness (VH). Two measurements on the top and two measurements on the bottom of each sample were archived. The values in the table showed the percentage of HV at 3mm depth compared the HV on top.

Results:

 

Halogen

      Plasma

Xenon

 

 

Anova

 

40s

6s

10s

10s

15s

20s

 

P60

 67,45

78,76

92,51

61,40

77,04

90,94

0.0001

Enamel

 37,15

26,73

35,53

23,01

31,25

45,59

0.0001

 

Conclusions:High power curing devices applied for shorter time didn’t show adequate curing ability in depth compared to traditional halogen lamp. Rising up the curing time nevertheless it is possible to obtain better composite curing at 3mm depth compared to the results performed by the halogen lamp.

 

 

 

 


2014 (16998)

Microfocus X-ray CT Analysis of Shrinking Direction in Resin Composite. N. INAI*1, N. KATAHIRA1, K. HASHIMOTO1, J. TAGAMI1, A. HIRAKIMOTO2, S.J. MARSHALL3, and G.W. MARSHALL3, 1 Tokyo Medical & Dental University, Japan, 2 2Shimadzu Co, Kyoto, Japan, 3 University of California San Francisco, USA

Objectives: The aim of the study was to evaluate the polymerization shrinkage of light-cured resin composite in an adhesive cavity.

Methods: A microfocus x-ray CT (computed tomography) instrument (SMX-255CT, Shimadzu Co., Kyoto, Japan) was used to analyze and characterize the pre- and post-gel phases of resin composites The KHN of resin composite in several conditions were determined along the light direction. Experimental resin composite (Tokuyama Co., Tokyo, Japan) containing spherical particles of zirconium oxide (average particle size of 60 microns in diameter), was used as a contrast medium. The resin mold with or without a bonding agent, 6mm in depth and 4mm in diameter, was filled with the experimental resin paste. The specimen was rotated at the point between an x-ray tube and a detector to acquire fluoroscopic images from every direction. The displacement of the radiopaque particles between before and after polymerization was determined on the same slice phase.

Results: The displacement of filler particles on the central axis directed to the subsurface area (1.4-1.5mm from the surface) and was larger in the deeper layer than in the superficial layer. On the top sides, the polymerization shrinkage indicated 0.13% for the non adhesive cavity, and 0.98% for the adhesive cavity. On the bottom sides, 3.10 and 0.42% respectively. Although KHN of the top side was same between non adhesive and adhesive cavities, the bottom side for the non adhesive cavity was harder than that of adhesive cavity even after irradiation from the bottom side. This reduction of the polymerization shrinkage was caused by the adhesion to the cavity wall.

Conclusion: It was concluded that the use of the adhesive on the cavity wall compensated the contraction gap space but the contraction stress could be increased. Supported by Grant-in-aid for Scientific Research No. 12307043 from the Japan Society for the Promotion of Science.


2015 (19992)

Is The Polimerization Linear Shrinkage Percentage a Constant ?. M. SCHROEDER*, R.Y. BALLESTER, and L.L. FRANCO, University of São Paulo - Dental Materials, Brazil

Objective: To evaluate if the percentage value of polymerization linear shrinkage [ %LPS ] of a resin (Herculite XRV shade A3 - Kerr) is affected by: 1) the Cavity configuration factor; 2) the total amount of mJ/cm2 applied in the light activation.  Methods: The specimens were cylindrical, sized 2mm in diameter, and either 2mm high (C factor=0.5) or 4mm high (C factor=0.25). Activating light was oriented perpendicularly to the cylinders long axle (n=5) for 15, 30, 60 or 120s with 300 or 600 mW/cm2. Results: The %LPS values, oriented in the cylinder axles, at 5 min (mean ± SD) were obtained with an extensometer (Instron). The resulting data were analyzed by ANOVA, which showed significant differences (p<0.000) for both factors, but not for their interaction. Tukey test (p<0.05) allowed us to establish the significant differences, shown in the table by the different letters, which come together with each mean (Greek characters for comparisons inside columns and Latin for comparisons inside lines).
C Factor Activation Energy (mJ/cm2)
4500 9000 18000 36000 72000
0.25 0.94 ± 0.09   (a a) 0.99 ± 0.05   (a a) 1.09 ± 0.08   (a b,c) 1.12 ± 0.06   (a c) 1.11 ± 0.09   (a c)
0.50 1.25 ± 0.11    (b a) 1.29 ± 0.09    (b a) 1.29 ± 0.12    (b b,c) 1.34 ± 0.10 (b c)