Evaluation of fits of metal copings fabricated by using selective laser melting at various angles

Information on the fabrication of metal by selective laser melting (SLM) systems positioned at different angles is sparse.

The purpose of this in vitro study was to evaluate the extent of marginal and internal gaps in metal copings fabricated at different angles by using an SLM fabrication system.

A master metal model was produced and replicated (N=10) with silicone impressions and dental stone. Standard tessellation language (STL) files of the 10 coping designs were then obtained by using a model scanner and a 3D design software program on a scannable working die. Co-Cr alloy metal copings were fabricated by the SLM fabrication system at 45, 90, and 180 degrees. The marginal and internal gaps were measured by the silicone replica technique. The measured data were analyzed by using the nonparametric Kruskal-Wallis H test (α=.05).

The specimens fabricated at 180 degrees showed the best fit in terms of the marginal gap, while the worst fit was observed in the specimens fabricated at 90 degrees. Statistically significant differences were seen among the marginal gaps produced in the 3 groups (P<.001). In terms of internal fit, the axial wall gap showed the best fit, and the occlusal gap the worst. The best fit overall was 66 μm at the axial wall of the 180-degree group, and the worst in the 90-degree group, at 663 μm. Statistically significant differences were observed between the chamfers, axial walls, and the occlusal gaps of the 3 groups (P<.001).

Restorations fabricated by using an SLM system at 180 degrees were clinically acceptable. However, more research is required to investigate the performance of metal copings produced at 45 and 90 degrees to evaluate their clinical acceptability.