Abstract
BACKGROUNDS: Bleaching procedure can be companied before, during, or after orthodontic treatments. However, the risk of compromised bond strength of brackets to bleached enamels is in debate. This study tried to evaluate the shear bond strength (SBS) of bonded metal brackets to the previously bleached enamels. MATERIALS AND METHODS: In this in vitro study, 60 extracted, sound, human premolars were mounted vertically in cylindrical molds. The samples were randomly divided into four groups (n = 15): Control (C); at-home bleached by 20% carbamide peroxide (HB); in-office bleached by 45% carbamide peroxide (OB); and in-office bleached by 40% hydrogen peroxide activated with diode laser (L-OB). Sixty stainless steel brackets were bonded by no-primer adhesive resin (OrthoCem). Then SBS of bonded brackets was measured after 5000 thermal cycles at 5°C and 55°C. Finally, the collected data were analyzed by one-way ANOVA, and Tukey HSD tests by using SPPS software at a significant level of 0.05 (α = 0.05). RESULTS: Group C showed significantly higher SBS values (all P < 0.001); however, there were no significant differences in SBS compared to other tests' groups with each other (all P > 0.05). CONCLUSION: The SBS of bonded orthodontic brackets were compromised after bleaching with 20% and 40% of carbamide peroxide. Diode laser activation may not eliminate the negative effect of bleaching agents on SBS of bonded orthodontic brackets, neither.