Immediate and Delayed Repair Bond Strength of Amalgam -Composite Resin with Various Universal Adhesives and Surface Treatments

Introduction: Amalgam is a safe and effective option for direct restorations. For amalgam repairs, it is recommended to use composite resin along with an adhesive agent on pretreated amalgam surfaces. This study investigated the shear bond strength (SBS) between composite and both new and aged amalgam, using different universal adhesives on the pretreated alloy surfaces. Methods: In this experimental in-vitro study, a total of 132 amalgam discs were prepared and divided into two main groups: fresh and aged (6 months water storage + 2000 thermal cycles). The aged amalgam specimens were randomly treated with sandblasting, pumice, or bur. Based on the type of adhesive used, each treated group was further divided into three subgroups: Single Bond Universal, Clearfil Universal Bond, and G-Premio Bond. Fresh amalgam groups were randomly divided into the Single Bond Universal and Clearfil Universal Bond subgroups. All samples were repaired with composite and then subjected to 2000 thermal cycles, followed by SBS assessment using a universal testing machine. One-way and two-way ANOVA, post-hoc Tukey’s, Kruskal-Wallis, Mann-Whitney, and T-tests were used for statistical analysis. Results: Single Bond Universal + pumice exhibited the highest SBS and Clearfil Universal Bond + bur was associated with the lowest SBS. Among the aged samples, groups prepared with bur had significantly lower SBS values compared to those treated with sandblasting or pumice. The SBS values for the Single Bond Universal groups were significantly greater than those for the Clearfil Universal Bond groups. Conclusion: Pretreatment with pumice and sandblasting yielded the highest SBS between aged amalgam and composite. Furthermore, Single Bond Universal resulted in the best SBS values.