Influence of reinforcement bar on accuracy of removable partial denture framework fabricated by casting with a 3D-printed pattern and selective laser sintering

Purpose: The purpose of this study was to investigate the accuracy of removable partial denture frameworks fabricated by 3D-printed pattern casting (AM-Cast) and selective laser sintering (SLS) under different co nditions with a reinforcement bar. Methods: A partially edentulous model was scanned with a dental laboratory scanner, and CAD software was used to design the framework. Reinforcement bars (n=0-2) were set on the lingual side of the framework. 3D scanning of the fabricated frameworks by AM-Cast and SLS was performed, and the obtained data were overlapped with the design data. The differences in shape among setting conditions of the bar were statistically compared using the Bonferroni method after the Kruskal–Wallis test. Results: The ranges in differences of the AM-Cast-0, AM-Cast-1, and AM-Cast-2 were -0.167 to 0.128 mm, -0.101 to 0.105 mm, and -0.185 to 0.015 mm, respectively. The ranges of SLS-0, SLS-1, and SLS-2 were -0.166 to 0.035 mm, -0.182 to 0.049 mm, and -0.138 to 0.038 mm, respectively. Large discrepancies were observed at the joining area of the lingual bar on the right side of the AM-Cast. A significant difference was found between the AM-Cast-0 and AM-Cast-1, and between the AM-Cast-0 and AM-Cast-2. Conclusions: The setting conditions of the reinforcement bar affected the accuracy of the lingual bar in the AM-Cast; however, no effect was observed on the displacement of the central area of the lingual bar in SLS. Setting a single reinforcing bar on the retentive latticework contributed to improving the accuracy of the lingual bar in the AM-Cast but not the displacement of the central area of the lingual bar in SLS.