Effect of Framework Orientation at a Selective Laser Melting Building Platform on Removable Partial Denture Fit

Objectives: This in vitro study aimed to evaluate the effects of three framework orientation (FO) positions on an SLM building platform (Horizontal [H], Diagonal-45° [D45°], Diagonal-60° [D60°]) and two designs (with [B] or without [NB] stabilizing bars) on the fitting accuracy of digitally fabricated Co-Cr RPD frameworks. Materials and Methods: A custom RPD framework CAD was performed on a 3D-printed resin-model of an edentulous maxilla with three geometric tooth forms. A Co-Cr alloy was processed via SLM processing into 24 framework specimens, divided into three FO groups (n = 8: H, D45°, D60°) and two subgroups each (n = 4: B, NB). Qualitative/quantitative fit-evaluation was assessed using virtual framework-to-model seating and a custom digital protocol with GOM Inspect software (2018-Hotfix5, Rev.115656). Mean fitting distances were calculated from 220 equidistant points per specimen. Statistical comparisons were performed using ANOVA-on-ranks, Kruskal–Wallis multiple comparisons, and Bonferroni adjustment. Results: FO Sub-Group medians (Q1, Q3: 25% and 75% Quartiles) (mm) were: H/NB 0.150 (0.140, 0.164), H/B: 0.136 (0.121, 0.152), D45°/NB: 0.230 (0.219, 0.241), D45°/B: 0.144 (0.137, 0.154), D60°/NB:0.238 (0.232, 0.247), D60°/B: 0.171 (0.166,0.176). Pairwise comparisons indicated the following statistically significant (p < 0.05) FO Sub-Group differences: H/B-D45°/NB, H/B-D60°/NB, D45°/B-D45°/NB, D45°/B-D60°/NB, H/NB-D45°/NB, H/NB- D60°/NB. Conclusions: Horizontal orientation improved RPD fit accuracy regardless of bar presence. D45° accuracy is enhanced by stabilizing bars, while D60° accuracy is unaffected by bar addition.