Internal fit evaluation of crowns prepared using a new dental crown fabrication technique: laser-sintered Co-Cr crowns

Abstract

Statement of problem: Difficulties encountered during casting of base metal dental alloys limit their use. Application of these alloys might be enhanced if new techniques are used.

Purpose: The purpose of this study was to compare the internal fit of laser-sintered Co-Cr alloy crowns with base metal restorations prepared from another Co-Cr alloy and a Ni-Cr alloy using conventional casting techniques.

Material and methods: Internal fit of laser-sintered Co-Cr crowns was compared with the fit of conventionally cast Ni-Cr and Co-Cr alloy crowns. Twelve crown-shaped specimens were prepared on a stainless steel die representing a prepared maxillary right central incisor for each group. Fit of crowns was evaluated using 2 different techniques: (1) weighing the light-body addition silicone that simulated a cement material, and (2) measuring the internal gap width on a die for longitudinally sectioned specimens. One-way ANOVA followed by Tukey multiple comparison test was used for statistical analysis (alpha=.05).

Results: Significantly higher mean (SD) light-body silicone weights (P<.001) were observed in the laser-sintered Co-Cr alloy group (14.34 (1.67) mg) compared to the conventionally cast Ni-Cr alloy group (9.36 (1.97) mg) and Co-Cr alloy group (7.85 (1.19) mg). Mean internal gap widths (SDs) were 58.21 (19.92) microm, 50.55 (25.1) microm, and 62.57 (21.62) microm, respectively, for the cast Ni-Cr and Co-Cr alloy groups and the laser-sintered Co-Cr alloy group. No significant difference was observed between the 3 groups for internal gap widths (P=.42).

Conclusions: Weighing the light-body addition silicone is a convenient method for evaluating the 3-dimensional internal fit of dental crowns. However, no significant difference was found among the 3 alloy groups evaluated for the internal gap width of sectioned crown specimens.