Materials and methods. The labial surfaces of 150 sound bovine incisor teeth were abraded with abrasive paper. The teeth were randomly divided into 8 groups: A: control B: bleached with 35% hydrogen peroxide C: bleached with 35% hydrogen peroxide + sodium ascorbate gel and D: bleached with 35% hydrogen peroxide + delayed bonding. In groups A‒D, silorane adhesive system and Filtek silorane composite resin were used. In groups E‒H, the same preparation methods of groups A‒D were used. Two-step self-etch Clearfil SE Bond adhesive systems and AP-X composite resin were administered. Shear bond strength of each group was measured. Two samples were prepared for each surface preparation for ultra-structural evaluation. Two-way ANOVA and Tukey test were used for data analysis at P< 0.05. 

Results. The interaction between the adhesive system type and surface preparation protocol was significant (P=0.014), with significant differences in shear bond strengths in terms of the adhesive systems (P< 0.01). There were significant differences in shear bond strength in terms of surface preparation techniques irrespective of the adhesive system (P< 0.01).

Conclusion. The results showed that bleaching with 35% hydrogen peroxide decreased the shear bond strength values with both adhesive systems, and a one-week delay in bonding and 10% sodium ascorbate for 10 minutes restored the bond strength in both adhesive systems.