Accuracy of CAD-CAM milling versus conventional lost-wax casting for single metal copings: A systematic review and meta-analysis

Abstract

Statement of problemInformation comparing the marginal and internal adaptation of single metal copings fabricated via computer-aided design and computer-aided manufacturing (CAD-CAM) milling and lost-wax casting is insufficient. PurposeThe purpose of this systematic review and meta-analysis was to compare the adaptation of single metal copings fabricated via CAD-CAM milling to that of copings fabricated via lost-wax casting and to identify factors that influenced their accuracy. Material and methodsFollowing the preferred reporting items for systematic reviews and meta-analyses (PRISMA) guidelines, Elsevier ScienceDirect, PubMed, Cochrane Library, SpringerLink, and Wiley online databases were searched to select qualified articles, which were assessed by the methodological items for nonrandomized studies (MINORS) criteria. The data on the mean absolute marginal gap, marginal gap, axial gap, occlusal gap, and internal gap values of single metal copings fabricated via CAD-CAM milling and lost-wax casting were extracted, and meta-analysis and meta-regression were used with R software (α=.05) and random-effects models to estimate differences and homogeneity between the 2 methods. ResultsFor the single metal copings, lost-wax casting and CAD-CAM milling led to similar marginal and internal accuracies, but lost-wax casting led to better absolute marginal gap values. For the cast copings, Ni-Cr alloy (92.8 μm) and noble alloy (51.5 μm) led to the largest and smallest marginal gaps, respectively, (P=.005). For milled copings, the noble alloy led to the smallest marginal gap (19.1 μm), and Co-Cr alloy to the largest (76.2 μm) (P=.012). Soft milling led to a more accurate marginal gap (41.4 μm) than hard milling (66.1 μm) (P=.04). ConclusionsWhen CAD-CAM milling was used to fabricate single metal copings, no advantage in precision was found compared with lost-wax casting, and single metal copings cast from handmade conventional wax patterns had better marginal adaptation than those fabricated via CAD-CAM milling. Noble metal copings had improved marginal accuracy than base metal copings for both the casting and milling methods. Single copings fabricated via soft milling from unsintered metal blocks had more accurate marginal adaption than copings fabricated via hard milling.