Three different sprue designs were investigated visually and radiographically to determine the influence of spruing arrangement on the soundness of RPD castings. The first sprue design was a tree sprue design consisted of four wax formers, 3 mm in diameter each, going directly to four different spots on the major connector. The second sprue design was a circular sprue design. The circular feeder was made from a 3 mm diameter wax. The auxiliary sprues emanating from the circular feeder were six in number, 2 mm in diameter each, and were attached directly to the major connector. The circular feeder was attached to the sprue button by four formers, 3 mm in diameter each. The third sprue design was designated as the bali sprue design. The ball design consisted of four feeders, 3 mm in diameter each, as with the tree design except that a 5 mm ball reservoir was placed on each feeder, 5 mm away from the wax pattern. Five frameworks of the same dental cast were prepared using each sprue design. The results showed that the three sprue designs used in this study are suitabie for producing sound RPD frame castings. When the circular sprue design is used, allowances should be made to assure adequate meshwork thickness.

Saudi Dental Journal 1994;6(2):88-93.