effect of postoperative bleaching on microleakage of etch-and-rinse and self-etch adhesives

background: bleaching the discoloured teeth may affect the tooth/composite interface. the aim of this in vitro experimental study was to evaluate the effect of vital tooth bleaching on microleakage of existent class v composite resin restorations bonded with three dental bonding agents.     methods: class v cavities were prepared on buccal surfaces of 72 intact, extracted human anterior teeth with gingival margins in dentin and occlusal margins in enamel, and randomly divided into 3 groups. cavities in the three groups were treated with scotch bond multi-purpose, a total etch system and prompt l-pop and ibond, two self-etch adhesives. all teeth were restored with z250 resin composite material and thermo-cycled. each group was equally divided into the control and the bleached subgroups (n = 12). the bleached subgroups were bleached with 15% carbamide peroxide gel for 8 hours a day for 15 days. microleakage scores were evaluated on the incisal and cervical walls. data were analyzed using kruskal-wallis, mann-whitney and bonferroni post-hoc tests (α = 0.05). results: bleaching with carbamide peroxide gel significantly increased the microleakage of composite restorations in prompt l-pop group at dentinal walls (p = 0.001). bleaching had no effect on microleakage of restorations in the scotch bond multi-purpose and ibond groups. conclusion: vital tooth bleaching with carbamide peroxide gel has an adverse effect on marginal seal of dentinal walls of existent composite resin restorations bonded with prompt l-pop self-etch adhesive.