The castability of pure titanium compared with Ni-Cr and Ni-Cr-Be alloys

Abstract

Statement of problem: Titanium is the most biocompatible metal available for dental casting; however, there is great concern about its castability since this aspect of a casting metal/alloy has direct influence on the marginal fit of dental crowns.

Purpose: The purpose of this study was to compare the castability of commercially pure titanium with 2 Ni-Cr base metal alloys.

Material and methods: Castability was evaluated indirectly by determining the sharpness of cast crown margins using the lost-wax technique. Castability was expressed in terms of the deficiency (mum) between an actual casting margin and a potentially perfect margin. Crown margins were recorded in a silicone impression material. The degree of marginal rounding was measured and margin length deficiencies (mum) were calculated. Sixty acrylic resin crown patterns with wax margins were prepared on a stainless steel stylized crown die having a 30-degree beveled finish line. The degree of wax margin rounding was determined in the control group (group W, n=15). The remaining 45 crown patterns were divided into 3 groups (n=15) and cast in commercially pure titanium (Tritan, group Ti), Ni-Cr-Be alloy (Verabond; group VB), and Ni-Cr alloy (Verabond II; group VBII). Margin configurations for both wax patterns and cast specimens were measured and recorded with the same method, using silicone impressions of the margins. After polymerization, the silicone material was sectioned in 8 locations through the margin area so that cross sections of the margins could be observed. Marginal deficiency was determined using microscopic measurements from the silicone sections and calculations. Data were subjected to 1-way ANOVA and Tukey HSD test (alpha=.05).

Results: Statistical analysis showed significant differences among the groups W, Ti, VB, and VBII (P<.001). The Tukey test revealed that Ti (108 +/-26 microm) was not significantly different from VBII (95 +/-35 microm), but was significantly different than Groups VB (22 +/-5 microm) and W (19 +/-6 microm), which were similar.

Conclusions: Within the limitations of this study, the castability of titanium was poor compared to Ni-Cr-Be alloy, but similar to Ni-Cr alloy.