Effect of finishing and polishing techniques on the fit accuracy and dimensions of conventional and CAD-CAM removable partial denture frameworks

Abstract

Purpose: The purpose of this study was to compare the effects of finishing and polishing techniques on the fit accuracy, metal loss, and surface roughness of conventional versus CAD-CAM removable partial denture (RPD) frameworks. Materials and Methods: A 3D-printed maxillary Kennedy class III modification I model served as the master cast. Forty impressions (20 conventional and 20 digital) were divided into four groups: lost-wax technique (Group I: LWT), CAD-printed (Group II: CAD-RP), CAD-printed from a stone cast (Group III: CAD-RPS), and lost-wax technique from resin-printed models (Group IV: LWTR). Various finishing and polishing techniques were applied, followed by digital scanning for fit accuracy assessment using surface matching software. Metal thickness loss and surface roughness were evaluated pre- and post-finishing and polishing. The Kruskal-Wallis test followed by the Scheffe post-hoc test were conducted to evaluate the fit accuracy between groups (α = 0.05). Results: Color mapping revealed significant differences (p < 0.001) between conventionally casted RPD frameworks and 3D-printed groups post-finishing and polishing. The most significant gap was observed with the guide plates from printed RPD frameworks. The D-Lyte technique resulted in less metal loss compared to the conventional finishing and polishing technique (p < 0.001). Conclusion: Within the limitations of this study, conventionally processed RPD groups exhibited better overall fit accuracy post-finishing and polishing. Both conventional cast and 3D-printed RPD frameworks showed clinically acceptable fit accuracy. The D-Lyte technique presented less metal loss and smoother surfaces compared to other groups, suggesting it as a viable alternative.