Influence of Plasma Treatment on the Bonding Strength and Hydrophilicity of Zirconia: A Systematic Review and Meta-Analysis

Achieving reliable adhesion between resin-based materials and zirconia remains challenging because zirconia has a chemically inert surface and low intrinsic wettability. Plasma surface treatment has been proposed as a non-destructive method to improve surface energy, hydrophilicity, and bonding performance without altering the bulk structure of zirconia. However, variations in plasma type, gas composition, exposure duration, and testing protocols have limited clear conclusions regarding its effectiveness. This systematic review and meta-analysis were conducted in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) 2020 guidelines and registered in the International Prospective Register of Systematic Reviews (PROSPERO) (reference ID: CRD42025640563). Electronic searches of PubMed/MEDLINE, Scopus, Embase, Web of Science, and the Cochrane Library were performed up to January 31, 2026. Fourteen in vitro studies met the inclusion criteria. Risk of bias was assessed using the QUIN (Quality Assessment Tool for In Vitro Studies) tool. Overall, plasma-treated zirconia showed improved wettability and enhanced bond strength compared with untreated controls. Several studies also reported bond strength values comparable to or greater than those achieved with alumina sandblasting, particularly when plasma treatment was combined with 10-methacryloyloxydecyl dihydrogen phosphate (MDP)-containing primers. A meta-analysis showed a significant improvement in shear bond strength for plasma-treated zirconia compared with untreated zirconia (standardized mean difference (SMD) 3.04; 95% CI: 1.76-4.32), although heterogeneity was high. In the comparison with sandblasting, the primary pooled analysis was not significant, but the sensitivity analysis favored plasma treatment. Plasma surface treatment appears to be a promising strategy for improving zirconia bonding, although standardized protocols and clinical studies are still needed.