Silane Coupling Agents are Beneficial for Resin Composite Repair: A Systematic Review and Meta-Analysis of In Vitro Studies

To systematically review the literature to determine whether silane combined with adhesive application improves the repair bond strength of direct methacrylate-based resin composites in comparison to the use of an adhesive alone.

The literature up to December 2019 was searched through PubMed/MEDLINE, Scopus, and Lilacs databases with no publication year or language limits. From 676 potentially eligible studies, 81 were selected for full-text analysis, and 19 were included in the systematic review. Two reviewers independently selected the studies, extracted data, and assessed the risk of bias. Meta-analyses were conducted using a random effects model to calculate pooled mean differences between adhesive- vs silane-plus-adhesive surface treatments (global meta-analysis) and considering subgroup analyses (immediate and aged repair bond strengths and type of silane - hydrolyzed or nonhydrolyzed). Statistical analyses were performed using RevMan5.3 at a significance level of 5%.

Global meta-analysis showed that the use of silane prior to adhesive application produced significantly higher repair bond strengths (p=0.003). A higher mean difference (effect size: 7.30, 95% CI: 2.91-17.51) between groups was found when nonhydrolyzed silanes were used. The heterogeneity was high. Studies scored between medium and high risk of bias.

An additional silane application step could increase the repair bond strength of methacrylate-based resin composites.