This study aimed to evaluate the effect of sodium hypochlorite (NaOCl) pretreatment on bond strength of adhesive systems to different dentin regions.

Forty human molars were randomly assigned according to different adhesive systems (Adper Single Bond 2; Clearfil SE Bond; Adper SE Plus; G-Bond), pretreatments (control and NaOCl - deproteinization) and dentin regions (proximal, superficial occlusal [SO] and deep occlusal [DO]), n = 5. Cylindrical cavities were performed at the proximal and occlusal surfaces of each sample. For deproteinization, 10% NaOCl was applied on conditioned dentin for 60 s before the adhesive systems application. Two occlusal and one proximal slice were obtained from each sample and submitted to the push-out test. The mode of fracture was analyzed. The data were subjected to three-way ANOVA and Tukey test (P < 0.05).

There was statistically significant difference between the adhesive systems (P < 0.01) and dentin regions (P < 0.01); however, the pretreatment did not significantly affect the bond strength values (P > 0.05). The bond strength values were higher for the proximal surface, followed by SO and later by DO, being influenced by the adhesive system. The two-step self-etch adhesive systems presented the highest bond strength results.

The deproteinization pretreatment showed similar bonding effectiveness to the conventional adhesive technique. The dentin region plays a rule on the bond strength values.