Basic Researches for Titanium Cast Crown Using Calcia Investments

The interest in the application of titanium and its alloys to dental prostheses is increasing since they possess good mechanical properties. However, fabrication of titanium prostheses, especially the casting procedure, has been very difficult because of its chemical reactivity at high temperatures. In our previous study, we could obtain a sound titanium casting using the calcia mold which is very stable for titanium. In this study, we investigated the calcia investments containing metal titanium powder to improve the casting accuracy. Setting and thermal expansion at 1, 000°C of the calcia investment with 8.8wt% titanium powder was 0.5% and 1.2%, respectively. The marginal opening and cement layer thickness between the die and the titanium cast crowns obtained from the calcia mold fired at 1, 000°C were found to be improved when the content titanium powder was 8.6wt% or 8.8wt%. The contamination of oxygen produced a hardened layer with a thickness of about 250μm under surface of titanium casting; nevertheless, it was possible to finish a glazing surface by the conventional polishing procedures.