Self-etch Adhesive Systems: Effect of Acid and Proteolytic Etching on Bond Strength

Objective: To evaluate the bond strength to dentin of four self-etch adhesive systems using different bond strategies. Methods: Sixty human molars were sectioned in the mesiodistal direction. The hemi-sections (B and L) were randomly assigned to four groups: G1: Clearfil SE Bond (Kuraray), G2: AdheSE (Dentsply), G3: Self Etch (Vigodent) and G4: Vitremer (3M/ESPE). Each group was divided in 3 subgroups (n=10), according the bond strategy: maintenance (a), removal of smear layer (b) or removal of collagen (c), respectively. A split metallic matrix was used for fabrication of composite resin cylinders, the material being inserted in increments photoactivated during 40 seconds. All specimens were stored in distilled water at 37 degrees C during 24 hours until the shear bond strength test. The minimum and maximum values, mean, median, standard deviation and variation coefficient were calculated and analyzed using two-way F test (ANOVA) with interaction, one-way F test (ANOVA) and Tukey's paired comparisons at a significance level of 5% (alpha = 0.05). Results: Regardless of the bond strategy, G1 presented the highest mean bond strength values. Clearfil SE Bond and Self Etch Bond differed significantly (p<0.05) from the other adhesive systems when used according to the manufacturers' instructions (no smear layer removal). Clearfil SE Bond differed significantly from the other adhesive systems when smear layer or collagen was removed. Conclusion: Changes in the bond strategies of self-etch adhesive systems are not justified when they are applied according to the manufacturers' instructions.