Fit Accuracy of Removable Partial Denture Frameworks Fabricated from 3D-Printed Resin Patterns Versus Selective Laser Melting

Statement of Problem: Fit accuracy is not only essential to the success of prosthodontic rehabilitation with removable partial dentures (RPDs) but is also necessary to prevent trauma to the oral hard and soft tissues. Questions remain whether the fit accuracy of digitally fabricated RPD frameworks is comparable to those fabricated by more conventional techniques. Purpose: The aim of this study was to compare the fit accuracy of RPD frameworks fabricated by 3D-printed resin pattern casting versus those fabricated by selective laser melting (SLM). The null hypothesis is that there is no significant difference in the fit accuracy: (1) between 3D printed castable resin patterns and SLM-printed frameworks, and (2) among the 4 areas measured under the framework (rest, retentive arm, bracing arm, major connector) within each group. Materials and Methods: A mandibular metal reference model was milled and used for the simulation. Scanning of the model was performed using a desktop scanner. The framework was designed using CAD software. The 3D-printed resin patterns were fabricated using an SLA printer and casting was performed to fabricate the SLA-Cast frameworks. A direct metal printing machine was used to generate the SLM framework. Fit accuracy of the two groups was performed using silicone impression material and digital calipers to measure the mean vertical gaps. The independent t test was used to compare the mean vertical gaps between the 2 groups. Within each group, all 4 measured areas were compared using one-way ANOVA. Results: A clinically acceptable fit was achieved at the clasps and rests, regardless of the production method used. The overall mean vertical gaps were significantly different between the SLA-Cast and SLM frameworks – with greater gaps in the SLM frameworks. The mean vertical gaps at the 4 measured areas within the same group were all found to be significantly different from each other as well. Conclusion: The 0.12-mm difference in overall mean vertical gaps between SLA-Cast and SLM-frameworks may have no clinical significance. The greatest discrepancy in fit accuracy was observed under the major connector. There is still room for improvement in the adaptation of RPD frameworks fabricated through a digital workflow