Effect of sprue design on the castability and internal porosity in pure titanium castings

Objective: The aim of the study was to evaluate the pure titanium castability and internal porosity with 3 different sprue designs. Method and Materials: The sprue designs selected were the conventional cylindrical, funnel-shaped, and sheet-form sprue formers. To evaluate the castability, the mesh monitor was chosen. Eight mesh patterns (14 3 14 mm) of 49 squares were attached to each type of sprue design. They were invested in titanium investment material and cast in a semiautomatic titanium casting machine. The titanium castings were evaluated by 2 methods. One was the visual observation of the castings for completeness, and the second was the radiographic qualitative analysis for the location of the internal porosities. Results: Data were analyzed with analysis of variance and Student t test for paired comparison among different sprue designs. According to analysis of variance, all sprue designs revealed a statistically significant difference at the 5% level of confidence (P .05, F = 3.50). Mesh patterns attached to funnel-shaped sprue designs showed better percentage castability values. Conclusion: For titanium, casting using a funnel-shaped sprue design displayed better castability values and less internal porosities in the castings. Keywords: dental casting, porosity, sprue design, titanium castability