Comparison of digital and conventional methods of fit evaluation of partial removable dental prosthesis frameworks fabricated by selective laser melting

Abstract

Statement of problemThree-dimensional (3D) printing technology may improve the fit of partial removable dental prosthesis frameworks made by selective laser melting. Conventionally, the gaps between definitive casts and prostheses are evaluated by using clinical replicas, but digital evaluations may provide a better alternative. PurposeThe purpose of this in vitro study was to compare digital and conventional methods for evaluating the fit of partial removable dental prosthesis frameworks made by selective laser melting. Material and methodsA printed resin definitive cast representing a Kennedy class II modification 2 design with 5 reference markers was made from a dentiform cast. Twelve cobalt-chromium partial removable dental prosthesis frameworks were fabricated by selective laser melting on this definitive cast with a digital design software program. The gaps between the frameworks and the cast were assessed by using the clinical replica method with a silicone impression material and measuring the thickness at each marker with calipers. Digital casts of each framework and the definitive cast were scanned and then registered with the CloudCompare software program to measure 3D gaps at the 5 reference markers and 3 occlusal rests. The results were analyzed individually for each technique by 1-way analysis of variance (ANOVA) with post hoc Bonferroni tests (α=.05). ResultsFor clinical registration, the mean gap between the frameworks and definitive cast was 13.9 ±7.6 μm. For digital registration, the root mean square gap was 70.7 ±24.2 μm. Statistically significant differences among the gaps for different markers were found for both approaches (P<.05). There were no significant differences among the gaps between the different frameworks. In both situations, the gap measurements were below the 300-μm clinically acceptable standard. ConclusionsBoth registration methods determined whether the fit of a framework fabricated by selective laser melting was within a clinically acceptable standard. The differences in the values produced most likely arose from the different registration methods.