Effect of tooth bleaching on the shear bond strength of a fluoride-releasing sealant
Objective: 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. Methods and Materials: One hundred and sixty extracted human molars were randomly divided into bleached (N=80) and unbleached groups (N=80). The bleached group was treated with 45% carbamide peroxide for half an hour, followed with five applications of 20% carbamide peroxide at 24 hour intervals. After two 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 testings at 24 hours and 3 months using a Zwick Universal Test Machine. Results: The ANOVA analysis 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 statistically significantly lower than the others although still greater than clinically minimal suggested bond strengths. Interestingly, 15% of the bleached teeth exhibited enamel fracture at the 3-month testing. Conclusion: At 24 hours, both Pro Seal sealant and Transbond XT primer appear to be a reliable choice on both bleached and unbleached teeth. However, at the 3-month period, Pro Seal sealant yielded significantly lower shear bond strength on unbleached teeth, nevertheless well within the range of values considered to be "clinically acceptable".