Effect of surface treatment and the use of mouthwashes on repaired composite bond strength

Objectives: The purpose of this study was to evaluate the effect of mouthwashes on composite Knoop microhardness, and to assess the influence of the contact with mouthwashes and mechanical surface treatment on the shear bond strength of repaired composite resins. Methods: One hundred twenty composite resin (GrandioSO) specimens were prepared and randomly divided into four experimental groups, according to the used mouthwash (distilled water; Listerine Teeth & Gum; Eludril Perio; Lacer Oros). After a period of 5 days in water (37ºC), during which the specimens were submitted to twelve cycles of 2 hours of immersion in the respective mouthwash, the Knoop microhardness was determined. Then, each group was divided into three subgroups based on the mechanical surface treatment performed (no treatment; 50-µm Al2O3 sandblasting; abrasion with diamond bur), the repair protocol was performed (Solobond M and GansdioSO) and specimens were submitted to shear bond strength tests until failure. Data were analyzed using ANOVA followed by Student-Newman-Keuls post-hoc tests (α=0.05). Results: The group of specimens aged in distilled water presented a significantly harder surface than the other experimental groups (p<0.05). No statistically significant differences were found (p>0.05) between other groups. Neither the immersion media (p=0.214) nor the mechanical surface treatments (p=0.165) had a significant effect on the bond strength. Conclusions: Although the hardness of the composite was negatively affected by contact with the mouthwashes used in this study, the bond strength of composite repair was not affected.