0881 Stress Intensity Factor Threshold in Dental Porcelains
F.N. SOKI1, P.F. CESAR1, and H.N. YOSHIMURA2, 1University of Sao Paulo, Brazil, 2Institute of Technological Research of the State of São Paulo, Brazil

Objectives: The stress intensity factor threshold for crack propagation (KI0 ) corresponds to the stress intensity factor under which crack velocity is null. This study aimed to determine KI0 of seven dental porcelains aged in air or saliva, and correlate results with leucite content (LC). Methods: Beams (20x3x4mm3) were fired according to manufactures' instructions and polished before induction of cracks by a Vickers indenter (load=19.6N/dwell time=20s). For each porcelain, 7 specimens were tested (4 stored in air/ambient temperature, and 3 in saliva/37oC), and five indentations were done on each one. Crack lengths were measured under optical microscopy at various times over a period of 4 months: ~0; 1; 3; 10; 30; 100; 300, 1000 and 3000h. KI0 was determined by plotting log crack velocity versus log K, considering that K=cP/c3/2 (c is an indentation coefficient), as proposed by Wan et al. [J European Ceram Soc 6 (1990) 259-268]. Data were analyzed by one-way ANOVA (Tukey's test/alpha=0.05). Results: Storage in saliva did not result in a significant change in KI0, in comparison to air storage, for any of the materials tested. However, the mean values of porcelains B and G tended to be lower in saliva. As to porcelains A and F, a numeric increase in KI0 was observed after storage in saliva. Considering only leucite-based materials (and disregarding porcelains E and F), a positive relationship was found between leucite content and KI0, mainly in saliva. Conclusions: Storage media did not significantly affect KI0 of porcelains tested. For leucite-based materials, higher leucite contents lead to higher KI0. Acknowledgments: FAPESP and CNPQ.

Porcelain

LC (%)

KI0 (MPa.m0.5)

air

saliva

A(Ceramco-I-Dentsply)

22

0.58b,c,d

0.64a,b

B(Ceramco-II-Densply)

22

0.70a

0.63a,b,c

C(Finesse-Dentsply)

6

0.38g

0.40f,g

D(d.Sign-Ivoclar)

15

0.50d,e

0.52d,e

E(Cerabien-Noritake)

0

0.48e,f

0.47e,f

F(Vitadur Alpha- Vita Zahnfabrik)

0

0.52d,e

0.58b,c,d

G(Ultropaline-Jendental)

13

0.63a,b,c

0.53c,d,e

Seq #107 - Ceramics: Mechanical Properties and Marginal Fit
3:30 PM-4:45 PM, Thursday, March 22, 2007 Ernest N. Morial Convention Center Exhibit Hall I2-J

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