Influence of Digital Versus Analogue Workflows on the Clinical Marginal and Internal Fit of CAD/CAM Zirconia Fixed Restorations: A Systematic Review and Meta-Analysis

Background/Objectives: Marginal and internal adaptation are important determinants of the clinical performance of CAD/CAM zirconia fixed restorations. This systematic review and meta-analysis evaluated the influence of workflow type (digital versus analogue impression workflows) on the clinical marginal and internal fit of tooth-supported CAD/CAM zirconia fixed restorations. Methods: The review was conducted in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) 2020 statement and was prospectively registered in PROSPERO. PubMed/MEDLINE, Embase, Web of Science, Cochrane CENTRAL, IEEE Xplore, ClinicalTrials.gov, and Google Scholar were searched for clinical studies published from January 2014 through June 2026. Ten clinical studies met the eligibility criteria. Because most comparative studies used within-subject designs, the paired nature of the data was incorporated into the quantitative synthesis. Random-effects meta-analyses were performed using restricted maximum likelihood estimation and Hartung–Knapp adjusted confidence intervals, with sensitivity analyses across plausible within-pair correlations. Results: Four studies provided directly comparable data for quantitative synthesis of marginal fit and overall internal fit. Digital workflows showed a trend toward smaller marginal and internal discrepancies than analogue workflows (MD = −21.89 μm; 95% CI, −57.59 to 13.81 μm; p = 0.146; I2 = 88.3%), but the difference was not statistically significant. Overall internal fit similarly favoured digital workflows (MD = −21.65 μm; 95% CI, −57.66 to 14.36 μm; p = 0.152; I2 = 68.7%) without a statistically significant difference. Exploratory location-specific analyses of internal fit also showed no statistically significant differences. Sensitivity analyses across different assumed within-pair correlations did not materially alter the conclusions. Conclusions: Digital impression workflows showed a trend toward smaller marginal and internal discrepancies than analogue workflows; however, the pooled differences were not statistically significant. The considerable heterogeneity and limited number of quantitatively comparable studies warrant cautious interpretation. Further clinical studies using standardized fit definitions, measurement protocols, and appropriate reporting of paired outcomes are needed.