The aim of this study was to evaluate the effect of sodium hypochlorite (NaOCl) on the shear bond strength (SBS) using three bonding systems in primary dentin. Forty-five sound extracted primary molars were selected. The crowns were longitudinally sectioned, embedded in polystyrene resin, and flattened until a dentin surface was reached. The samples were assigned to 6 groups (n = 15): G1, Single Bond (SB); G2, NaOCl + SB; G3, Prime & Bond 2.1 (PB); G4, NaOCl + PB; G5, Clearfil SE Bond (CSE); G6, NaOCl + CSE. All the adhesive systems were applied according to the manufacturers’ instructions, except for the application of 10% NaOCl solution for 60 s in groups 2, 4 (after acid etching), and 6 (before applying adhesive system). The composite resin was placed in increments in a mold and light cured for 20 s. The samples were stored in distilled water at 37°C for 24 h and submitted to SBS testing with a crosshead speed of 0.5 mm/min. The failure sites were observed with SEM. The data were treated with ANOVA and Tukey’s tests (p < 0.05). There was no statistically significant difference between the groups with or without treatment of the substrate with NaOCl, regardless the material used. The SBS averages in MPa (± SD) were: G1: 15.8(1.9)a; G2: 14.6(1.3)a; G3: 10.2(0.7)a; G4: 9.9(0.2)a; G5: 13.3(1.2)a; and G6: 10.7(1.0)a. There was a statistically significant difference between the materials (SB ≥ CSE ≥ PB). Mixed failure was the failure type most frequently observed for all groups. Dentin surface treatment with NaOCl did not affect the resin-dentin bonding strength in primary teeth.

Keywords: sodium hypochlorite, primary teeth, dentin bonding