In vitro evaluation of the effect of antioxidants on the bond strength of bleached teeth

Objective: To evaluate the in vitro effect of antioxidants on the bond strength between composite resin and enamel subjected to bleaching agents. Methods: Nineteen sound human molars had their roots sectioned, while their surfaces were flattened and filled with composite resin to produce the specimens, which were then divided into seven groups: G1 – unbleached and without antioxidant (control); G2 – 36% carbamide peroxide; G3 – 36% carbamide peroxide and 10% ascorbic acid solution; G4 – 36% carbamide peroxide and 10% ascorbic acid gel; G5 – 16% carbamide peroxide; G6 – 16% carbamide peroxide and 10% ascorbic acid solution; and G7 – 16% carbamide peroxide and 10% ascorbic acid gel. The results of microtensile strength were submitted to an analysis of variance (ANOVA) and Tukey’s test, with a significance level of 5%. Results: The bond strength between composite resin and enamel was not affected after the use of bleaching agents. In addition, ascorbic acid did not appear to neutralize the oxidative effects of these agents, given that group 3 showed the lowest mean of bond strength (13.85 MPa). In other groups, the mean of bond strength ranged from 24.06 MPa to 32.02 MPa, with no significant differences when compared to the control. Conclusion: The presence of ascorbic acid immediately after bleaching did not increase the bond strength between the resin and the enamel surface.Uniterms: Tooth bleaching. Antioxidants. Ascorbic acid. Dental enamel. Composite resins.