Effects of repeated firing on the marginal accuracy of Co-Cr copings fabricated by selective laser melting

Abstract

Statement of problemSelective laser melting (SLM) is a technique used to fabricate Co-Cr dental restorations; however, because marginal accuracy is important for the long-term success of restorations, the marginal accuracy of SLM after repeated firings must be considered. PurposeThe purpose of this study was to evaluate the marginal accuracy of dental Co-Cr alloy copings fabricated by SLM and to investigate the effects of repeated firing on the marginal fit of these copings. Material and methodsSLM-fabricated and cast Co-Cr alloy copings (n=15) were prepared for a zirconia die. The marginal gap widths of each group were evaluated with a silicone replica technique after the first, third, fifth, and seventh firing cycle. The thickness of the reference point was measured with a stereomicroscope with ×100 magnification. Analysis of variance was used to evaluate the effect of repeated firing on the marginal accuracy of the 2 alloys. The Student t test was used to compare the marginal gap widths of the SLM-fabricated and cast Co-Cr alloy copings after repeated firing (α=.05). ResultsThe marginal gap width values between the 2 groups at all firing periods were statistically significant (P<.05). The mean marginal gap width values for SLM-fabricated copings were 36 μm, 37 μm, 38 μm, and 38 μm after the first, third, fifth, and seventh firing, while the mean marginal gap width values for cast copings were 67 μm, 71 μm, 72 μm, and 73 μm at the same number of firings. The marginal gap width values within the 2 groups were not statistically different from each other with additional firing (P>.05). ConclusionsThe SLM copings demonstrated superior marginal accuracy at all firings. Repeated firing had no significant influence on the marginal accuracy of both copings, and the marginal fit of both copings after repeated firing was within a clinically acceptable range.