Bonding Efficacy of Universal Resin Adhesives to Zirconia Substrates: Systematic Review and Meta-Analysis

Purpose: To provide an overview of the in-vitro bond strength of universal adhesives to zirconia and analyze whether these adhesives are a reliable alternative to conventional zirconia primers. Materials and Methods: A systematic search was conducted in PubMed/Medline, Scopus, and ISI Web of Science databases up to August 2021. Investigations published in English, assessing resin-mediated bond to zirconia using universal adhesives compared to phosphate/silane-based primer or phosphate-based primer were included. After study selection and data extraction, risk of bias analysis was performed. Statistical analyses were performed using RevMan 5.4, with a random effects model, at a significance level of 0.05. Results: In total, 23 studies were included for qualitative and quantitative analysis. Universal adhesives showed higher bond strengths than did phosphate-based primers (p < 0.00001) to aged zirconia without airborne alumina-particle abrasion. Similar results were observed when the zirconia surface was airborne-particle abraded at baseline and after dynamic aging (p < 0.0001). When universal adhesives and phosphate-silane based primers were compared, similar bond strengths (p >= 0.001) were observed after surface abrasion, regardless of storage condition. Conclusion: The results showed that universal adhesives generate higher bond strengths when compared to conventional zirconia primers.