Effects of Bleaching on Bond Strength: An in vitro Study

Recent years have witnessed a drastic increase in the awareness towards cosmetic dentistry. Bleaching has become a common procedure in the field of cosmetic dentistry. Thus, it seems important to determine whether bleaching would significantly influence the bond strength of orthodontic adhesives to the enamel surface. The purpose of this study was to determine the effect of a 35% hydrogen peroxide containing in-office bleaching agent on the shear bond strength of adhesive to metallic orthodontic brackets. Materials and methods: Sixty extracted, sound premolars were randomly divided into three groups of 20 each. Teeth in group A were etched with 37% phosphoric acid before bonding metallic premolar brackets using light cure composite resin. Teeth in the other two groups were bleached with a 35% hydrogen peroxide in-office bleaching agent according to the manufacturer’s recommendations. Twenty bleached teeth (group B) were bonded immediately with light cure composite resin, and the other 20 (group C) were stored in artificial saliva for 30 days before bonding. Shear bond strength of these brackets were measured using Instron universal testing machine, recorded in MPa and compared. Results: Statistical analysis was done using ANOVA (Analysis of variances) by Fisher’s F-test. The intercomparison between the groups was calculated by Bonferroni t-test (Post-Hoc test). The shear bond strength values of groups A, B and C were 11.8850 ± 2.29651, 11.4750 ± 4.454774 and 12.7450 ± 3.82491 MPa respectively. Results of ANOVA showed no statistically significant differences in shear bond strengths between groups (p = 0.541). Conclusion: This study showed that office bleaching with 35% hydrogen peroxide does not adversely affect the bond strengths of orthodontic adhesives used to bond brackets immediately after bleaching or 30 days after bleaching.