[The effect of mold temperature on the accuracy of titanium castings]

To study the effect of mold temperature on the accuracy of titanium castings invested in the ZrP99 investment.

30 artificial stone dies simulated the post-tooth and their corresponding complete crown wax patterns were made with a truncated cone-shape standard brass model with round sleeves. They were divided randomly into five groups and each group had six samples. Four group wax patterns were invested in ZrP99 investment as test groups and one group was invested in Titavest-CB investment as control. The test group moulds were cast at the mould temperature 600 degrees centigrade, 450 degrees centigrade, 300 degrees centigrade, 150 degrees centigrade, respectively. Measure the distance separating the gingival margin of the crown and the shoulder of the die in the same way as for the wax pattern. The casting accuracy was represented by the discrepancies derived from the space distance measurements made with wax patterns and cast crowns. t test and one-way ANOVA were used for statistical analysis.

Measurement of the casting accuracy indicated that the casting accuracy of the control group was higher than all the test groups. When the mold temperature was lower than 450 degrees centigrade, the accuracy of the castings invested in ZrP99 investment was improved significantly with the mold temperature raised.

To satisfy the requirement of the clinical practice in the point of the casting accuracy, the mold temperature of ZrP99 investment must be chosen higher than 300 degrees centigrade.