Dimensional accuracy and internal and marginal fit evaluation of Co-Cr crowns prepared by SLM / 实用口腔医学杂志

ABSTRACT

Objective: To study the dimensional accuracy of the Co-Cr crowns prepared by selective laser melting(SLM) technology and to evaluate their internal and marginal fit by "Virtual seating". Methods: The Co-Cr metal crowns were fabricated with 2 different methods(n = 10) milling wax with lost-wax method in the control group and SLM in the test group. After collecting the data of the die and crowns, "virtual seating" was completed by the software of reverse engineering. The gaps between the die and crowns on the 2D cross-sectional were measured by the same software. At last, crowns were cemented on the dies. And the thickness of the crowns and the cement films were measured under a scanning electron microscope. Data were statistically analyzed. Results: The most appropriate pre-set die spacer thickness was 50 μm. The relative errors of the crown thickness of SLM group and the control group were 1. 80％ and 2. 20％ respectively(P＞ 0. 05). No statistically significant difference was found in both internal and marginal fit between the 2 groups (P＞ 0. 05). And there was no statistical difference between the 2 measuring methods (P＞ 0. 05). Conclusion: SLM technique achieves clinically values for internal and marginal fit. "Virtual seating" can be used for evaluate crown dimensional accuracy.