Methods: Thirty coronal dentin discs (0.5 mm thick X 6.0 mm diameter) were prepared from bovine teeth. The dentin discs were randomly divided into three groups (n=10): control group (unbleached group); bleached with 10% carbamide peroxide for 8 hours; bleached with 38% hydrogen peroxide (the gel was applied 3 times consecutively for 15 minutes each application). The dentin discs were stored in 100% humidity during the bleaching or not. The specimens were tested in a biaxial flexural apparatus held in a universal testing machine (Instron 5844) at 1.27 mm/min until failure occurred, and biaxial mechanical properties were calculated. Within a given test parameter, data were statistically analyzed by ANOVA and Fisher`s PLSD test (pre-determined alpha = 0.05).
Table presents mean (SD) of test parameter results (MPa) among treatment groups.
|TEST PARAMETER||Control group (unbleached)||10% carbamide peroxide||38% hydrogen peroxide|
|Flexural Strength||188 (45) A||170 (53) AB||138 (51) B|
|Flexural Modulus||8969(966) a||8987 (1251) a||6848 (1155) b|
Within a test parameter, values having similar letters are not significantly different.
The 38% hydrogen peroxide demonstrated significantly lower flexural strength than the unbleached control group (p=0.0309) Hydrogen peroxide treatment resulted in significantly lower flexural modulus, when compared to control group and carbamide peroxide bleaching (p=0.0002).
Conclusions: Exposure of bovine dentin to hydrogen peroxide significantly reduces both flexural strength and modulus compared to no-treatment control, whereas exposure to carbamide peroxide did not significantly affect either parameter.
Keywords: Biaxial test, Bleach and Dentin
See more of: Dental Materials 9: Other Materials - Chemistry, Properties and Performance