Abstract:
Statement of problem: The effect of repeated firing on the marginal and internal adaptation of copings fabricated with different techniques, thicknesses, and alloy types is unclear. Purpose: The purpose of this in vitro study was to compare the effects of repeated firing cycles on the marginal and internal adaptation of metal copings with different thicknesses fabricated by using casting, selective laser sintering (SLS), presintered soft metal milling (PSMM), postsintered hard metal milling (PHMM), and titanium milling methods. Material and methods: Single-unit implant-supported copings (N=120) were fabricated with 0.5-mm and 1.5-mm thicknesses, and porcelain was applied in accordance with the manufacturer's instructions (n=12). The marginal and internal adaptation of the metal copings were examined before the firing cycles and after the fourth and seventh firing cycles by using a silicone replica technique with a stereomicroscope at ×80 magnification. The results were analyzed by using 3-way analysis of variance for repeated measurements on a single factor, 2-way analysis of variance, and an independent samples t test (α=.05). Results: As a result of the repeated firing cycles, the changes in the marginal discrepancy and internal discrepancy values in the PSMM, PHMM, and titanium milling groups and the change in the internal discrepancy value in the casting group were statistically significantly different (P<.05). The effect of the interaction of the firing, method, and thickness difference on the marginal discrepancy and internal discrepancy values was not statistically significantly different (P>.05). Conclusions: After the firing cycles, the PSMM, SLS, and titanium milling groups were found to have better marginal and internal adaptation for both thicknesses than the casting and PHMM groups. © 2020 Editorial Council for the Journal of Prosthetic Dentistry