The influence of spruing technique on the development of tension in a cast partial denture framework.

Distortions of cast removable partial denture frameworks result more from the method of sprue connection than from other variables in the investment and mold preparation. A standard test pattern and optical measuring equipment were used to evaluate residual casting stresses. Based on the data obtained from the initial study, modified removable partial framework patterns were made and cast under varying conditions. The use of a dorsal spruing technique and a box-type casting flask resulted in less distortion than use of the conventional vertical sprue attachment and investing in a ring flask. Dorsal spruing and use of a box-type casting flask reduced the deformation of a cast partial denture framework in the area of the palatal bar and retentive elements up to 0.3 mm. Such a tension-free casting method means a better fit of the partial framework on the master cast and intraorally.