Abstract
Recently, as an approach to the easier and more precise casting method, re-recognized was Die Investing Technique, whose chief characteristics is the investmentof the model itself together with the wax-pattern.
The present author examined various impression materials, density of colloidal silica, and casting alloy to obtain information of their influence upon the surface of models and castings, when Die Investing Technique was employed. He further compared the surfaces of castings between Die Investing Technique (Direct Technique) and Die Pattern Technique (Indirect Technique) with a view to ascertain the clinical effect of the former.
The following are the conclusions he reached:
1) The surface roughness of models and castings was closely related in the case when Die Investing Technique was employed.
2) The surface roughness of models are under the stronginfluence of the kind of impression materials: Hydrocolloid impression materials proved to have the surface roughness two or three times as large as Rubber Base impression materials.
3) The surface roughness was not largely dependent on the density of colloidal silica, but it showed a slight decrease when the density was high.
4) The reproducibility rate of the models, evaluated by Fourier analysis, marked highest when Surflex was used as an impression material, and Flexion, Hydro-Colloid, and Algiace came in the order of the rate.
5) The comparison of castings by Cristobalite investment material and by Die investment material proved that the surface roughness and the reproducibility indicated better results in the case of the latter.
6) He concluded that Die Investing Technique may well claim high clinical effectiveness when the surface roughness of castings was considered.
