Effect of different adhesive protocols on bond strength between composite resins for indirect use and repair materials

The aim of this work is to evaluate the effect of different adhesive protocols on the bond strength (SBS) of composite resin for indirect use to repairs of bulk-fill or conventional nanoparticulated composites. Forty-eight cylindrical specimens of composite resin for indirect use were prepared, aged, and randomly divided into four groups (n = 12), a control group without any adhesion protocol, and three experimental groups: Silane + Scotch Bond Multipurpose adhesive (S + SBMP), Tetric N Bond Universal (TBU), and Single Bond Universal (SBU). The treated surfaces were restored using two different composite resins: Filtek Bulk-Fill or Filtek Z350XT. Then, the specimens were submitted to the SBS test, and the resultant data were analyzed with ANOVA on ranks test and Tukey’s test (α = 0.05). There were no significant differences between the two types of resins used as repair material. For both resins, the groups treated with S + SBMP obtained the highest values (p < 0.001). Groups TBU and SBU did not have statistically significant differences between them. Pre-treatment with a silane coupling agent and a layer of a hydrophobic adhesive can improve the bond strength of repairs performed on a composite resin for indirect use.