| 0958 Effects of Various Concentrations of Hydrogen Peroxide Bleaching on the Flexural Strength and Modulus of Elasticity of Dentin | ||
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M. LIM, S. KHANNA, and L.E. TAM, University of Toronto, Canada Dentin is exposed to bleach indirectly via permeation through enamel, or directly by application onto exposed root or other worn surfaces. The effects of tooth bleaching procedures on the structural integrity of dentin are unknown. Objectives: The purpose of this study was to determine if hydrogen peroxide (HP) tooth bleaching affected the flexural strength (FS) and modulus of elasticity (ME) of dentin. Methods: 2x2x20 mm rectangular beams of dentin, cut from previously frozen extracted bovine incisors, were randomly distributed into 5 groups (n=8) and immersed in various treatments for 60 minutes as follows: 6.5% HP (Crest Whitestrips, Procter & Gamble) or 7.5% HP (Day White, Discus Dental), 2 sequential 30 minute applications daily; 35% HP or placebo gel (Opalescence, Ultradent), 4 sequential 15 minute applications twice per week; or distilled water (DW) (control group), 1 application daily. All treatments were carried out at 37°C, >80% RH. After each immersion, specimens were rinsed and stored in DW at 37°C. After 20 days, FS testing was performed 24 hours following the last treatment using an Instron Universal Testing Machine with a crosshead speed of 0.75 mm/min. ME was determined from graphs produced during FS testing. Results were analyzed by ANOVA and Tukey's tests (p<0.05). Results: The mean FS results for dentin exposed to HP (range: 91.0 to 94.2 MPa), while lower, were not significantly different from the results for dentin exposed to either the placebo or DW (range: 103.5 to 107.0 MPa). The mean ME results for dentin exposed to the 35% HP (6.7 GPa) was lower but not significantly different from all the other groups (range: 8.3 to 8.7 GPa). Conclusions: The FS and ME of dentin were not significantly affected by HP tooth bleaching under the conditions of this study. This study supported by Faculty of Dentistry Research Grant #02/03-2. | ||
| Seq #106 - Color and Surface Roughness of Restorative Materials 3:45 PM-5:00 PM, Thursday, 26 June 2003 Svenska Massan Exhibition Hall B | ||
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