[Origination of casting porosity on high fused dental alloys by use of Bio-X X-ray unit (MRO-10R) (author's transl)].

Experiments were carried out clarify internal defects in dental casting with high fused dental alloys, as cobalt-chromium alloy or nickel-chromium alloy by use of Bio-X X-ray unit (MRO-10R for dental castings), exploited by KAWAHARA and TSK international corporation. Satisfactory radiographic observations were obtained with the following results; 1. In any of castings, a large amount of porosity was found on X-ray clearly. 2. On the castings in this experiment, porosity, round and bubble like in shape was markedly observed in the location right below the sprue attachment and its neighborhood. But in regions far from sprue, porosity was decreased, it came gradually to be present on the surface of castings. 3. Radiographically some defects were of a clack type and a shrinkage type in castings, although castings seemed to be quite sound in appearance. These types of defects were considered to become a weak point when external force was applied. 4. In regard to the completeness of castings, especially large round shape, clack type and shrinkage porosity can be prevented by a rapid removal of the air or gas from a mold and by improving the casting system to obtain better efficiency.