The Effect of Adhesive Procedures on the Repair Bond Strength of Aged Universal Composites

Background: The purpose of this study is to evaluate the repair bond strength of aged universal composites after surface treatment and different adhesive applications. Methods: Three universal composites (GC Achord, Filtek Ultimate, Clearfil Majesty) were used to prepare 315 specimens (n=105 per composite). Seven groups were created: a negative control (NC) (only polished), a positive control (PC) (bur–roughened-only) and five experimental groups in which roughened surfaces were treated with G2-Bond Universal (G2), Prime&Bond Universal (PB), Clearfil SE Bond (SE), the hydrophobic bond of G2 (G2B), the hydrophobic bond of SE (SEB). Repair restorations were completed using Nova Compo HS. Shear bond strength was measured at a crosshead speed of 1 mm/min, and values were recorded in MPa. Fracture modes were classified as adhesive, cohesive, or mixed. Data were analyzed using the Kruskal–Wallis test (p<0.05). Results: The lowest bond strength values were observed in the negative control groups. In contrast, the highest values were found in the G2 groups; for all composites, G2, PB, and G2B showed significantly higher repair bond strengths than the other groups. The PC, SE, and SEB groups demonstrated similar bond strengths, which were significantly higher than those of the NC. No significant differences were observed among the different universal composites within any of the adhesive groups. Conclusions: Only polishing resulted in the lowest repair bond strength. G2, G2B, and PB provided superior repair bonding compared with SE, SEB, and bur-roughened-only groups. All tested universal composites exhibited comparable repair bond strengths when adhesives were applied.