Fundamental Studies on Impression Method. Part 10. Effect of the Type of Impression Materials, Seating Speed and Holding Pressure of the Impression Tray on the Morphology of the Master Cast of the Mandibular Edenturous Ridge.

In the case of complete denture, the master cast should represent thecontour of the oral mucosal surface, also taking account of the basal soft tissue with regard to supporting ability. In this study, impressions were taken of a simulation model of the mandibular edentulous ridge, using silicone rubber (SIL), polysulfide rubber (RUB) and alginate (ALG) as impression materials and impression tray with stoppers. The effects of the type of impression material, seating speed and holding pressure of the impression tray on the contour of the master cast were investigated in terms of profiles and displacement. The results were as follows:As described above, of these three factors which influence the form of the working model of the mandibular edentulous ridge, (i.e. the influence of the choice of impression material on the impression pressure, of the tray seating speed and the holding pressure), during impression-taking, the most influential is the holding pressure of the tray. This suggests that full consideration must be given to the supporting ability of the under lying tissues when taking impressions from patients with a mandibular edentulous ridge.