Effect of Internal Bleaching on the Microshear Bond Strength of Composite Resin to Dentin in Recently Restored Teeth

Background: this study aimed to assess the effect of internal bleaching on the microshear bond strength of composite resin to dentin in recently restored teeth. methods: this in vitro, experimental study evaluated 40 sound human premolars. the teeth were sectioned below their cementoenamel junction. access cavity was prepared, pulpal tissue was removed and filled with glass ionomer. the teeth were then randomly divided into 4 groups. in the control group, no internal bleaching was performed and dentin surface was restored with composite. in group 2, internal bleaching with 35% hydrogen peroxide (opalescence, ultradent) was performed 4 weeks after composite restoration. bleaching was performed immediately after restoration of teeth in groups 3 and 4. teeth were etched with 35% phosphoric acid for 15 seconds, rinsed, dried, and primer and adhesive (adper scotchbond multipurpose) were applied. the teeth were then restored with z250 (3m espe) microhybrid resin composite. teeth were sectioned into 1 mm2 sections and underwent micro-shear bond strength test. in groups 1 to 3, bond strength was measured after 24 hours while in group 4, it was measured after 1 month. data were analyzed using one-way anova. results: the mean micro-shear bond strength of composite to dentin was maximum in group 2 and minimum in group 3. however, the difference in this respect was not significant among the groups (p>0.05). conclusion: in teeth requiring immediate esthetic restorations, treatments can be performed after non-vital bleaching with no time restriction and adequately high bond strength comparable to nonbleached teeth.