Dentin Bond Strength of Two One-Bottle Adhesives after Delayed Activation of Light-Cured Resin Composites

Objective: adverse surface interactions between one-bottle adhesives and chemical-curedcomposites may occur with delayed light activation of light-cured composites. the purposeof this study was to assess the effects of delayed activation of light-cured compositeson shear bond strength of two one-bottle adhesives with different acidity to bovine dentin.materials and methods: flat dentin surface was prepared on sixty-six bovine incisorsusing 600 grit carbide papers. prime&bond nt, and one-step adhesives and resin compositewere applied in six groups: 1) immediate curing of the composite, 2) the compositewas left 2.5 minutes over the cured adhesive before light activation, 3) prior to delayedactivation of the composite, the cured adhesive was covered with a layer of nonacidic hydrophobicporcelain bonding resin (choice 2) and cured immediately. after thermocycling,shear bond strength (sbs) test was performed using a universal testing machine at1 mm/min crosshead speed. data were analyzed with friedmans two-way non-parametricanova.results: the sbs of delayed activation of prime&bond was significantly lower than immediate activated (p<0.05). decrease in the sbs of one-step was not statistically significant after delayed activation. the sbs of delayed activation of prime&bond and one- step with an additional resin layer was significantly higher than delayed activation (p<0.001).conclusion: the bond strength of prime&bond might be compromised by the higher acidity of this adhesive during the 2.5 minutes delayed activation of light-cured composite. addition of a layer of hydrophobic resin compensated the effect of delayed activation and improved the bond strength.