The Fit Accuracy of Removable Partial Denture Metal Frameworks Using Conventional and 3D Printed Techniques: An In Vitro Study

Abstract

To evaluate the accuracy of removable partial denture (RPD) metal frameworks fabricated by the conventional lost-wax (CLW) technique and those made by the selective laser melting (SLM). A dentoform of a mandibular Kennedy class III, modification 1 dental arch were surveyed, and rest seats were prepared on the abutment teeth. The dentoform was then duplicated into a metal die which was used as a reference model. Thirty RPD metal frameworks were fabricated by two techniques; fifteen for each technique. Polyvinyl siloxane (PVS) impression material was painted on the intaglio surface of the rests of each framework which is then seated on the reference die. PVS specimens that represent the gap under the rest were measured in four zones: buccal, lingual, marginal and central by a single examiner using a digital microscope at 50x in micrometers. Comparison between the two techniques for each abutment tooth revealed that the CLW technique had better fit in one tooth, while the SLM technique showed a better fit in two teeth. Regarding the edentulous span length within the SLM technique, the long edentulous span had a significantly better fit. When comparing the four measured rest zones, it was found that in the CLW technique group, the marginal zone had the highest fit accuracy while the lingual zone showed the lowest fit accuracy. In the SLM group, the central zone had the best fit and the buccal zone had the worst fit. RPD frameworks fabricated using the SLM technique showed better fit accuracy than those made by the CLW technique, however, the difference was not statistically significant. SLM is a promising technique for the fabrication of RPD frameworks in routine clinical practice.