Fundamental studies of impression method part 2. Spacer and vent in impression tray.

An impression in denture prosthodontics is the first step for the construction of full denture.An impression is in clinic so important that the prognosis for denture is depended upon. Therefore, a considerable amount of reaserch has been reported. Especially, the soft tissue as an impression objectives can be displaced under pressure so that the method in edentulous impression making has influence on contour variations of the master cast.According to the impression, it is supposed that the adaptability to denture goes down and the basal soft tissue is injured in function. Basic and clinical studies on the edentulous impression have been considered, however, it seems not to arrive at evidence conclusion.The basic study (Part. 1) was designed for the sake of how to make impression for the functional denture without injury to edentulous patient. As the result of this study, the simulation model supposed edentulous alveolar ridge and three dimensions repositioner were made. Then, three dimensional measurement system to compare simulation model with master cast was reported and published.In this study, the three dimensional measurement system and simulation model as the alveolar ridge are used for impression in denture construction. It is investigated with the three dimensional measurement system that impression tray (spacer, vent), impression material and these combination are influenced on the reproductivity of simulation model.The conclusions are follows1. The cast from the simulation model type G without displaceability, is not influenced by impression tray and impression material.2. The cast from the simulation model type A-3 with constant displaceability, is not influenced by impression material but by the impression tray. The best cast is produced by the impression used the tray (spacer, vent) with alginate impression material.3. The cast from the simulation model type C with difference displaceability in part, is only influenced by impression material. The best cast is produced by the impression tray without spacer and vent using alginate impression material.4. From these conclusions (1-3), when the impression for the denture construction is made of the soft tissue with the poor displaceability, the impression tray and material are not so important. However, for the soft tissue with the rich displaceability, it is necessary that the impression tray is more considerable than material.