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) ,, 50.55 (25.1) ,, and 62.57 (21.62) mu m, 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. (J Prosthet Dent 2009;102:253-259)