Comparison of the Marginal and Internal Discrepancy of Metal-Ceramic Restorations Produced by Milling for Soft Metal, Direct Metal Laser Sintering and Casting Methods: An In Vitro Study

Abstract

Aim: To evaluate the effect of ceramic firing cycles on the internal and marginal discrepancy of restorations fabricated using conventional lost wax casting (LW), direct metal laser sintering (DMLS), and milling for soft metal (MS). Materials and Methods: A total of 45 restorations were produced by LW, DMLS, and MS methods ( n = 15), according to the digital impression on the metal die representing the prepared first molar. The internal discrepancy (ID) was measured through the silicon weight method and the marginal discrepancy (MD) was measured using a light microscope. ID and MD measurements were repeated following the metal manufacturing, ceramic application, and glazing. Statistical analyses were conducted by means of two-way analysis of variance and Tukey-HSD ( α = 0.05) tests. Results: Statistically significant differences were found between the fabrication methods ( P ≤ 0.001) both for MD and ID. The mean MD values of the restorations were 31.4 ± 13.8 µm for MS, 20.8 ± 14.4 µm for LW, and 7.3 ± 6 µm for DMLS. A statistically significant increase was observed in the mean MD values of metal frameworks ( P ≤ 0.001) following ceramic and glaze applications. However, no statistically significant difference was found between the ceramic and the glaze applied stages ( P = .072). The mean ID values were 37 ± 5.7 mg for LW, 28 ± 6.1 mg for DMLS, and 21.6 ± 7.3 mg for MS. Unlike the manufacturing method, ceramic firing cycles had no effects on the ID ( P > 0.05). Conclusion: MS had the highest mean MD, but it had the lowest ID. The ceramic firing had a significantly negative effect only on MD.