Sprue design in removable partial denture casting

Objectives: Correct sprue design is a major factor in the reduction of defects in castings of cobalt-chromium alloy. The purpose of this study was to investigate the sprue arrangements decided by a group of dental technicians, for a series of proposed removable partial denture castings, in order to determine if there was any consistency between them which would suggest the application of criteria in their design. Methods: Information was gathered by postal inquiry with recipients asked to indicate their sprue designs on diagrams of patterns for proposed cobalt-chromium partial denture castings. Results: Replies were received for 260 proposed castings from dental schools, technical colleges and commercial laboratories which gave an overall response rate of 52%. Results displayed a wide range of responses in relation to sprue number and dimension, attachment site and the intended direction of metal flow. Conclusion: It was concluded that the group of technicians studied arbitrarily chose sprue arrangements for the castings proposed rather than following definite design criteria that seek to minimize potential problems during casting procedures.