Effect of peroxide bleaching on the biaxial flexural strength and modulus of bovine dentin

OBJECTIVE This study evaluated the effects of carbamide peroxide and hydrogen peroxide on the biaxial flexural strength and flexural modulus of bovine dentin. MATERIALS AND METHODS Thirty coronal dentin disks (0.5 mm thick × 6.0 mm diameter) were prepared from bovine teeth. The disks were randomly divided into three groups (n=10): A control group (unbleached), a group bleached with 10% carbamide peroxide (8 h at 37°C), and a group bleached with 38% hydrogen peroxide (three 10 min applications at 37°C). The specimens were tested in a biaxial flexural apparatus held in a universal testing machine at 1.27 mm/min until failure occurred, and the biaxial mechanical properties were calculated. For each test parameter, the data were statistically analyzed by Fisher's PLSD test (predetermined α = 0.05). RESULTS The group bleached with 38% hydrogen peroxide demonstrated significantly lower flexural strength than the unbleached control group. Hydrogen peroxide treatment resulted in a significantly lower flexural modulus compared with the control group and with carbamide peroxide bleaching. CONCLUSION Exposure of dentin to hydrogen peroxide significantly reduced both the flexural strength and the flexural modulus compared with the no-treatment control, whereas exposure to carbamide peroxide did not significantly affect either parameter.