Purpose: This study aimed to investigate whether the accuracy and internal porosity of removable partial denture frameworks differ depending on the build direction in the selective laser melting method.
Methods: A partially edentulous maxillary study model was scanned, and the anterior–posterior palatal bar was then digitally designed. The angles formed between the z-axis and the path of the insertion and removal were divided into five groups: –60°, –30°, 0°, 30°, and 60°. For each group, three removable partial denture metal frameworks were fabricated and used as specimens. The inner surface of each sample was scanned and superimposed on the design file to obtain the root mean square (RMS) value, and the average RMS value of each group was measured. One sample was randomly selected from each group, and the equivalent diameter and sphericity of the pores were analyzed using industrial X-ray three-dimensional computed tomography. To compare statistical differences between groups, the Kruskal–Wallis test of SPSS Statistics ver. 27.0 (IBM) was used (α=0.05).
Results: The average RMS values of the whole inner surface accuracy of the specimens were in the order of –60°<0°<–30°<30°<60° (p<0.05). The equivalent diameter and sphericity of internal pores were significantly different among groups (p<0.001).
Conclusion: The build orientation of the selective laser melting method influences the accuracy and internal porosity of removable partial denture frameworks.

Keywords: Accuracy, Porosity, Removable partial denture, Selective laser melting