Effect of tooth bleaching on shear bond strength of a fluoride-releasing sealant

Abstract

To evaluate the effect of an in-office plus at-home bleaching protocol on shear bond strength of orthodontic buttons when using a fluoride-releasing sealant. Extracted human molars (160) were randomly divided into bleached (n = 80) and unbleached groups (n = 80). The bleached group was treated with 45% carbamide peroxide for 30 minutes, followed by five applications of 20% carbamide peroxide at 24-hour intervals. After 2 weeks, lingual buttons were bonded on the teeth in both groups using either Transbond XT primer or Pro Seal sealant. The teeth were then stored in artificial saliva and subjected to shear testing at 24 hours and 3 months using a Zwick Universal Test Machine. Comparisons of mean shear bond strength values were made with the analysis of variance test. The Fisher's exact test was used to evaluate the adhesive remnant index scores. The analysis of variance of the 24-hour results indicated a significant difference between the four subgroups (P < .0011). Further simple t-tests indicated that the differences were significant only between bleached and unbleached subgroups (P < .0011). The 3-month results showed the mean shear bond strengths of the unbleached group using Pro Seal sealant was significantly lower than that of the other, though still greater than clinically minimal suggested bond strengths. Interestingly, 15% of the bleached teeth exhibited enamel fracture at the 3-month testing. Both Pro Seal sealant and Transbond XT primer demonstrated reliable shear bond strength values on both bleached and unbleached teeth over time.