Mechanical Performance of CAD/CAM-Milled Versus 3D-Printed Resins for Prosthetic Applications: A Systematic Review and Meta-Analysis

Background: Digital fabrication techniques such as CAD/CAM milling and 3D printing are widely used for provisional dental restorations. However, differences in mechanical performance remain controversial. Objective: To compare the hardness and flexural strength of CAD/CAM-milled resins versus 3D-printed resins used in restorative dentistry. Methods: A systematic review and meta-analysis were conducted following PRISMA 2020 guidelines and registered in PROSPERO (CRD420251045547). Electronic searches were performed in PubMed, Scopus, Web of Science, Embase, and LILACS. In vitro studies comparing CAD/CAM-milled and 3D-printed resins in terms of hardness and/or flexural strength were included. A random-effects inverse-variance model was applied using standardized mean difference (SMD) with 95% confidence intervals (CI). Risk of bias was assessed using the RoB-Iv tool. Results: Four studies (n = 124 specimens) were included in the hardness meta-analysis. CAD/CAM-milled resins showed significantly higher hardness (SMD = 2.92; 95% CI: 0.34–5.49; p = 0.026), although heterogeneity was high (I2 = 94.9%). Funnel plot asymmetry suggested possible small-study effects. For flexural strength, three studies (n = 40 specimens) were analyzed, demonstrating a significant effect favoring milled resins (SMD = 1.28; 95% CI: 0.42–2.14; p = 0.0036) with low-to-moderate heterogeneity (I2 = 27.8%). Sensitivity analyses confirmed robustness for both outcomes. Overall methodological quality was acceptable, with no high risk of bias identified in strength studies. Conclusions: CAD/CAM-milled resins tend to demonstrate higher hardness and flexural strength compared with 3D-printed resins. However, the substantial heterogeneity observed, particularly for hardness, and the potential influence of methodological variability, warrant cautious interpretation of these findings.