the effect of different concentrations of carbamide peroxide on the marginal seal of composite restorations bonded with a self-etch adhesive

Introduction: bleaching of discolored tooth may affect the tooth/composite interface. the aim of this study was to evaluate the effect of different concentrations of carbamide peroxide (cp) on the marginal seal of composite restorations bonded with a self-etch adhesive.materials &methods: in this experimental study class v cavities were prepared on the buccal and lingual surfaces of 24 intact extracted human molar teeth with gingival margins in dentin and occlusal margins in enamel. the cavities were restored using the adhesive system clearfil se bond and the composite filtek z250. finally, they were randomly divided into four groups (1 control and 3 bleached groups). the control group was kept for two weeks in distilled water at 37° c. the bleached groups were bleached with 10%, 22% and 35% cp gel for 8 hours a day for 14 days. after that, the samples were immersed in 0.5% fuchsin solution and sectioned. then gingival microleakage was graded. data was analyzed using kruskal wallis and mann whitney u test (p≤0.05).results: microleakage was observed in the gingival wall of all groups. there was a significant difference between the control group and the bleached groups. microleakage in the 22% bleached group was less than the other concentrations, but this difference was not significant.conclusion: bleaching with different concentrations of cp can increase the microleakage of the gingival wall of composite restorations bonded with clearfil se bond self-etch adhesive and does not recommend.