Investigation of the effect of three sprue designs on the porosity and the completeness of titanium cast removable partial denture frameworks

Statement of problem. Although titanium has been used to cast removable partial denture frameworks, the casting process is arduous and requires specialized equipment.

Purpose. This study evaluated the ability of 3 sprue designs (tree, ball, and circular) to produce complete, void-free castings of removable partial denture frameworks made from commercially pure titanium.

Methods and material. A cast with a Kennedy class III, modification 1, partially edentulous arch was used. The blocked-out cast was modified to facilitate assessment of the completeness of the casting of the clasp arms. Thirty refractory casts were made, and 10 wax patterns for each sprue design were fabricated and invested with ethyl silicate investment. Castings were made with an arc-type automatic casting machine in an argon atmosphere. Castings were examined with radiographic equipment to detect the presence of voids in the castings, and the completeness to each casting was visually verified. Data on porosities were tabulated and statistically analyzed with 1-way ANOVA followed by Student Newman-Keuls test. Chi-square analysis was used to identify statistically significant differences in casting defects among the 3 sprue designs.

Results. No statistically significant differences in the total number of porosities were found between the 3 sprue designs (P=.51). Results of completeness of castings evaluated by using chi-square test revealed a statistically significant deference among the 3 sprue designs (P=.008).

Conclusion. The ball-sprue design produced the most complete castings for the removable partial denture titanium frameworks.

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