Internal Fit Evaluation of Laser-Sintered Co-Cr Alloy Crowns

Clinical selection of base metal dental alloys might be enhanced if new techniques are employed that avoid present dental laboratory casting of these alloys. Crown fit is one of the most important criteria for dental restoration success. Objective: To compare the internal fit of laser-sintered Co-Cr alloy crowns with base metal Ni-Cr (Wiron 99, Bego, Germany) and Co-Cr (WBC 9581, Bego) alloy crowns prepared by conventional casting. Methods: 9 specimens were prepared for each of the three groups. Fit of crowns was evaluated using two different techniques. One method was weighing the light-body silicone impression material filling the inner gap between the preparation surface and the restoration, while the other method was measuring the internal gap width on longitudinally sectioned specimens at five standardized points. ANOVA followed by Tukey test was used for statistical analysis. Results: Significantly higher silicone weights (p < 0.001) were observed for the laser-sintered crown group (14.15 mg ± 1.63 mg) compared to the conventionally cast Ni-Cr alloy group (9.02 mg ± 1.98 mg) and Co-Cr alloy group (7.75 mg ± 0.99). Mean internal gap widths with standard deviations were 62.4 ± 21.2 µm, 41.1 ± 19.9 µm, and 57.8 ± 12.1 µm, respectively, for the cast Ni-Cr and Co-Cr alloy groups, and the laser-sintered Co-Cr alloy group. No statistically significant difference was observed between three groups for internal gap widths (p = 0.051). Conclusions: Weighing the light-body silicone is a convenient method for 3-dimensional internal fit evaluation of dental crowns. The internal fit of laser-sintered Co-Cr crowns was found to be comparable with the fit of crowns made from commonly used cast Ni-Cr and Co-Cr alloys. Even though laser-sintering of Co-Cr crowns seems to be a promising technique, follow-up research with patients is needed to further evaluate its clinical performance.