Comparative effect of Zircos-E and airborne-particle abrasion on zirconia surface treatment: A meta-analysis

Debonding of zirconia restorations remains a significant clinical challenge due to its glass-free microstructure, which limits micromechanical and chemical adhesion. Zircos-E, a nitric-hydrofluoric acid mixture, has been proposed as a simplified room-temperature alternative to airborne-particle abrasion (APA). This meta-analysis aimed to compare the shear bond strength (SBS) of zirconia surfaces treated with Zircos-E etching versus APA.

A systematic search of PubMed, Web of Science, and Scopus databases identified in vitro studies published from 2015 to January 2025 comparing Zircos-E etching with APA and reporting SBS values with standard deviations and sample sizes. Eight studies (308 specimens) met the inclusion criteria. Quality assessment was performed using the QUIN tool. A random-effects model was applied to calculate standardized mean differences (SMDs) with 95% confidence intervals (CIs). Subgroup analyses were conducted according to aluminum oxide particle size, and heterogeneity was assessed using the I² statistic.

Overall, Zircos-E etching significantly increased SBS compared with APA (SMD = 1.54; 95% CI: 0.08-3.00; p = 0.04), with substantial heterogeneity (I² = 95%). Subgroup analysis showed no significant difference between 50 and 110 µm Al₂O₃ particle sizes (p = 0.86). Sensitivity analysis excluding the study with the largest effect size reduced the pooled effect (SMD = 1.16; 95% CI: -0.06 to 2.38) and statistical significance (p = 0.06), although the direction of effect remained consistent. In the subgroup analysis by aging protocol, Zircos-E demonstrated a statistically significant improvement in the non-thermocycled subgroup (SMD = 1.72, 95% CI: 0.23-3.21, p = 0.03), while no significant difference was found in the thermocycled subgroup (SMD = 1.38, 95% CI: -1.80 to 4.55, p = 0.30).