Fundamental Studies of Impression Method: Part 8. Effects of the Type of Impression Material, Seating Speed and Holding Pressure of Impression Tray on the Morphology of Master Cast of Maxillary Edentulous Ridge

In construction of complete denture, the master cast should represent the contour of oral mucosal surface, with the basal soft tissue taken into account on the basis of anatomical understanding. In this study, I took impressions of a simulation model of the maxillary edentulous ridge, using silicone rubber (SIL), polysulfide rubber (RUB) and alginate (ALG) as impression materials with impression tray having stoppers. The effects of the type of impression material, seating speed and holding pressure of impression tray on the contour of the master cast was investigated in terms of the profiles and displacement, and the following results were obtained. 1. The seating speed, with SIL indicated no effects in the space section and the stopper section. With RUB and ALG, there were no effects in the space section, but were evident effects in the stopper section. 2. The holding pressure, with SIL, RUB and ALG indicated no effects in the space section, evident effects in the stopper section. 3. A comparison of impression materials revealed that the displacement in the space section was largest for SIL: the other two materials showed similar degrees of displacement. In the stopper section, I found the order of SIL, RUB and ALG at the minimum holding pressure, and ALG, RUB and SIL at the maximum holding pressure, according to descending displacement. Thus, SIL was found to be the most appropriate impression material for representing the contour of the mucosal surface of master cast of maxillary edentulous ridge.