Method: Eighty epoxy polymer discs (12 mm in diameter x 2 mm thickness) were made, and divided into 8 groups (n=10): G1: Control Group, without etching (CG); etched with G2: 10%, G3: 24%, G4: 35% and G5: 50% Hydrogen Peroxide (HP); G6: Sodium Ethoxide (SE); G7: Potassium Permanganate (PP); and G8: Citrate Buffer (CB). The adhesive system was applied on epoxy polymer disc and a customized 2-mm-thick elastomer molds, each with three cylinder-shaped orifices (1.2 mm in diameter) were placed on the epoxy polymer discs, allowing the bonding area to be delimited. The adhesive was light activated for 20 s with the light-tip placed directly onto the elastomer mold. The orifices were filled with a photoactivated composite and light activated for 20 s. Thirty cilinders were obtained for each group. All specimens were stored in distilled water at 37oC for 24 h and submitted to a microshear bond strength test at a crosshead speed of 0.5mm/min until failure. Data were submitted to ANOVA and Tukey’s post-hoc test (p<0.05).
Result: The microshear bond strength values (MPa; mean ± standard deviation) were: Group 5 (16.4±3.2) was significantly higher than groups 1 (9.2±1.8), group 2 (9.8±1.6), 3 (10.5±2.4), 4 (13.9±2.9), 6 (11.2±2.2), 7 (10.5±2.2) and 8 (12.4±2.7). Groups 4 and 8 were significantly higher than groups 1, 2 and 3. No significant difference was found between groups 4 and 8, among groups 6, 7 and 8 and among groups 1, 2, 3 and 7.
Conclusion: Etched with 50% hydrogen peroxide showed the highest values of the microshear bond strength. Control group without etched showed the lowest values of the microshear bond strength.