Accuracy of marginal and internal fit of additively manufactured single unit crowns: A systematic review and meta-analysis

STATEMENT OF PROBLEM: Three-dimensional (3D) printing is becoming more popular in restorative dentistry. However, evidence on the level of accuracy of additively manufactured single crowns is limited. PURPOSE: The purpose of this systematic review and meta-analysis was to evaluate the available literature and research on the accuracy of fit of single crowns produced by additive manufacturing (AM) in comparison with subtractive computer-aided design and computer-aided manufacturing (CAD-CAM) and conventional methods. MATERIAL AND METHODS: Electronic databases (PubMed, Scopus, and Cochrane) were searched for relevant articles published between January 1990 and July 2023. Two independent reviewers conducted the study selection, data extraction, and quality assessment. Standardized mean difference (SMD) with 95% confidence intervals (CIs) was calculated to evaluate all outcomes. A Cochrane chi-squared test was conducted to evaluate heterogeneity among articles, and the risk of bias was assessed using a modified methodological index for nonrandomized studies (MINORS) (α=.05). RESULTS: A total of 1271 records were identified; 25 articles fulfilled the inclusion and exclusion criteria. The results showed no statistically significant difference between AM and subtractive CAD-CAM methods in terms of marginal (SMD=-0.14; 95% CI: -0.60, 0.33; P=.57) and internal fit (SMD=-0.25; 95% CI: -0.73, 0.23; P=.30). Similar results were found for trueness and precision. A significant difference was found between AM and conventional methods for marginal fit, favoring AM (SMD=-1.18; 95% CI: -2.22, 0.14; P=.03), with no significant difference for internal fit (SMD=-0.76; 95% CI: -1.57, 0.05; P=.07). CONCLUSIONS: No significant differences were found between the AM and subtractive CAD-CAM methods. However, in terms of marginal fit, this study favored AM over conventional methods, with no significant difference in internal fit. These are promising and encouraging results for AM and indirect restorations.