Effect of 16% carbamide peroxide bleaching agent on the shear bond strength of orthodontic brackets.

Objective: To determine the effect of 16% carbamide peroxide on the shear bond strength of metal brackets bonded to premolars either immediately or 30 days after bleaching and to evaluate the bond-failure sites.

Material and method: Sixty freshly extracted human premolars were randomly divided into three groups, each containing 20 teeth. Specimens in group A (control) were not bleached (etched only with 37% phosphoric acid) before bonding. The teeth in the other two groups were first bleached with 16% carbamide peroxide according to the manufacturer's recommendation. The teeth in group B were bonded immediately, while the teeth in group C were stored in artificial saliva for 30 days prior to bonding. Shear bond strength was measured and recorded in MPa. Adhesive remnant index (ARI) scores were determined after the brackets failed. Data were analyzed with analysis of variance (ANOVA) and the chi-square test.

Results: Group A showed higher shear bond strength values than groups B and C, but the differences among the three groups were not significant (P=.053). Moreover, no significant differences in ARI were found.

Conclusion: After bleaching with 16% carbamide peroxide, there is a slight, insignificant decrease in shear bond strength. The site of bond failure is not significantly affected by bleaching.