The effect of sprue design on the marginal accuracy of titanium castings

The purpose of this study was to measure the effects of sprue number and position on cast titanium crown margins. Twenty-four complete veneer crown wax patterns were fabricated on a stainless steel die with a 30 degrees bevel finish line. Twelve wax patterns were sprued with one 8-gauge wax sprue and the remaining 12-gauge double sprued. All patterns were invested with a phosphate bonded investment. Castings were made with a titanium casting machine following the manufacturer's instructions and using commercially pure titanium (> 99.5%) ingots. The castings were than carefully cleansed and the margins were examined with indirect impression technique. Data were analysed with an ANOVA and the Student's t-test with confidence level at 95%. The results revealed that the marginal discrepancy for the double sprueing group (32.1 +/- 12.8 microm) has significantly less discrepancy (P < 0.001) than the single sprueing group (49.8 +/- 16.4 microm). There was no statistically significant differences in marginal discrepancy between locations within the sprueing techniques (P > 0.05). An improvement in the degree of casting accuracy of titanium crown was indicated by the double sprue design used in this investigation.