Purpose: This study was conducted to evaluate the accuracy of the internal and marginal surfaces of metal copings manufactured using lost-wax casting (LWC) and selective laser melting (SLM) methods.
Methods: A prepared upper left incisor on the master model was selected as the abutment tooth and scanned using a model scanner. Copings were fabricated by casting with cobalt– chromium (Co–Cr) alloy or three-dimensional (3D) printing with Co–Cr powder (n=20). The manufactured specimens were scanned and saved in standard tessellation language format. Accuracy was measured using a 3D analysis program. Statistical analyses were conducted using the SPSS (IBM). Significant differences were evaluated using the Shapiro–Wilk test. The Mann–Whitney U-test, a nonparametric method, was used because normality was not satisfied (α=0.05).
Results: The mean root mean square (RMS) values of trueness of the internal and marginal surfaces in the LWC method were 37.12±1.21 and 59.92±4.48 μm, respectively, which were higher than the values of 20.73±1.07 and 44.61±2.67 μm, respectively, in the SLM method, with the difference being statistically significant (p<0.001 and p=0.023, respectively). The internal surface mean RMS values of precision in the LWC and SLM groups were 22.39±2.87 and 21.16±1.25 μm, respectively, which showed no statistically significant difference (p=0.872); however, the marginal surface mean RMS values were 50.97±2.24 and 22.11±1.19 μm, respectively, indicating a statistically higher precision in the SLM group (p<0.001).
Conclusion: The internal and marginal surfaces of metal copings manufactured using LWC and SLM methods showed significantly different accuracy, except for internal surface precision. Both methods yielded clinically acceptable values.

Keywords: Accuracy, Lost-wax casting, Metal coping, Selective laser melting, Subtractive manufacturing, Three-dimensional printing