Comparative Evaluation of the Marginal Fit of Zirconia and Polyetheretherketone Copings Fabricated Using...

Accurate marginal adaptation is essential for the clinical longevity of fixed dental restorations. Zirconia and polyetheretherketone (PEEK) have emerged as popular computer-aided design and computer-aided manufacturing (CAD/CAM) materials for dental copings, but limited evidence exists directly comparing their marginal fit. This systematic review aimed to critically evaluate and compare the marginal fit of zirconia and PEEK copings fabricated using CAD/CAM systems. This review protocol was prospectively registered in PROSPERO (CRD42024604881). An electronic literature search was conducted in PubMed, SCOPUS, Web of Science, Google Scholar, Embase, and EBSCOHost to identify studies published between 2016 and 2025. Eligible studies included in vitro experiments comparing the marginal fit of zirconia and PEEK copings using quantitative measurements. Data extraction and risk of bias assessment were independently performed by two reviewers using a standardized form and the QUIN tool. A meta-analysis was conducted using Review Manager software where appropriate, and heterogeneity was assessed using I² statistics. Eight studies met the inclusion criteria. Sample sizes ranged from 18 to 40, using extracted teeth or typodont/resin models. Zirconia demonstrated superior marginal fit in six of eight studies, with mean gap values ranging from 17 to 60 µm. Meta-analysis of five studies (n=126 samples) showed a standardized mean difference (SMD) of 1.72 µm (95% CI: -0.46 to 3.90 µm; p = 0.12) favoring zirconia, though the result was not statistically significant. High heterogeneity (I² = 95%) was observed. Both zirconia and PEEK copings exhibit clinically acceptable marginal adaptation. Zirconia generally shows better consistency, while PEEK remains a promising alternative under optimized fabrication conditions. Further standardized in vitro and clinical studies with aging simulations are warranted to guide evidence-based material selection.