Clinical studies of impression method. I-1. Effects of seating pressure and holding pressure on master cast.

With regard to the different kinds of impression methods used in the process of making a full denture, various effects are considered to be given on the forms of surfaces of jaw membrane according to the differences in the impression pressure, because of the fact that the jaw membrane, whose impression is to be taken, has pressure displacement nature.Then, the impression pressure was checked of each impression obtained by the five technicians, and the vertical displacement amount thus obtaind of the master cast was measured at each of the different measuring sections and a study was thereby made of the effects given to the master cast by different impression pressures. As a result, the following findings were made:1. The impression pressure is unique to each experiment subject and consequently there are a considerable amount of variations from one subject to another.2. The amount of impression pressure affects the stopper section on the master cast, praticularly the stopper section in the postdam.3. At the portion prossessing a bent or a stopper, the effects of the impression pressure is smaller than on the stopper section.