Evaluation of The in Vitro Studies on Marginal and Internal Fit Accuracies of Additive Manufactured Single-Unit Crowns: A Systematic Review

Digital dentistry has witnessed significant advancements in recent years, providing increasingly reliable techniques for tooth shape recording and treatment planning. Dissimilar to conventional approaches, the novel digital methods enable instant and seamless sharing of data via electronic connections to dental laboratories. Usually, restorations that include fillings are directly placed while indirect and extensive restorations, including bridges, onlays, and crowns are done using different materials such as lithium disilicate. The increased use of advanced dental technologies can be attributed to the cost reduction of impression materials, enhanced patient experience, and accurate and effortless scanning and capturing of affected regions. Further, digital scanners manufactured 3D models enable the prevention of possible challenges related to the traditional gypsum models. In restoration production, the Standard Tessellation Language (STL) files generated using scans are vital to the creation of 3D models for CAD/CAM software. Often subtractive milling and stereolithography additive manufacturing are the preferred methods for the fabrication of models; however, this systematic review has focused on the additive method owing to its aptitude to handle undercuts and intricate shapes, which are challenging to the subtractive method due to limited machine axes, as well as challenges of errors linked to variations in bur diameters during milling. Though indirect model scanning for CAD/CAM manufacturing is considered a viable alternative, it may result in errors due to impression materials and gypsum models' impressions. Therefore, direct digitalization is considered an increasingly precise option as it bypasses the requirement for scanning and fabrication of models. The increasing interest in anesthetic materials employed in restorations has been linked to the observed advancements in technology, which has additionally led to the use of zirconia and lithium disilicate materials. Advanced machines like IPS e.max have been used to broaden the restoration methods and materials’ scope. Moreover, the restoration’s fit precisions have a significant impact on the success and survival rates, and this makes the comprehension of possible marginal gaps and inaccuracies important. Therefore, the main objective of this systematic review is to assess the fit accuracy of single-unit crowns manufactured through additive manufacturing (AM) in comparison to computer-aided design/computer-aided manufacturing (CAD/CAM) and other traditional methods. In terms of accuracy, AM manufacturing techniques are similar to CAD/CAM and conventional methods. To realize the study objective, an in-depth search was conducted on Scopus, Web of Sciences, PubMed, and Cochrane databases for literature published between 2000 and 2025. The literature selection process, quality assessment, and data extraction were undertaken by two independent reviewers. In the end, 12 studies met the set inclusion criteria and were reviewed. The systematic review disclosed that there were no significant differences in the fit of accuracy (both internal and marginal) for CAD/CAM and AM methods, as well as the accuracy and trueness of measurements. Consequently, AM was observed to have a better marginal fit than the various conventional techniques, despite having a comparable internal fit to other techniques.