Yoshihiko Moriya

Fundamental Studies of Impression Method. Part 7. Reproducibility of Maxillary Edentulous Denture Ridge by Seating Speed and Holding Pressure of Impression Tray.

An impression in denture prosthodontics is the first step for the construction of complete denture. The alveolar mucosa as an impression objectives can be displaced underpressure so that method in edentulous impression taking has influenced on contour variations ofthe master cast.In this study, the impression pressure is devided between the seating speed and holdingpressure of the impression tray, and the three dimensions repositioner and simulation modelsupposed maxillary edentulous alveolar ridge are used for impression in the denture construction.It is investigated with three dimensional measurement of the master cast that the seating speedand holding pressure are influenced on the reproducibility of simulation model.As the result of this study, the following conclusion was obtained.1. The seating speed dose not influence contour variations of the master cast irrespectiveof pressure-displaceability of simulation model.2. The holding pressure influences contour variations of the master cast of the simulationmodel except the simulation model without pressure-displaceability.The pressure-displacement of the stopper portion and the portion close to stopper areinfluenced by holding pressure.Especially, the simulation model with rich pressure-displaceability raise the large amount ofpressure-displacement according to holding pressure.

Fundamental Studies of Impression Method. Part 9. Mandibular Edentulous Simulation Model.

A considerable amount of research on construction of the complete denture has been reported, used the simulation model as the edentulous aleveolar ridge.The simulation model is required the approximation to the edentulous alveolar ridge on its morphology and caracteristic. Especially, the soft tissue as an impression objectives can be displaced under pressure so that the impression method has influenced on contour variations of the master cast. Therefore, pressure-displaceability is an important property.In this study, the authors attempted to development the simulation model as the maxillary edentulous alveolar ridge and examined its efficiency.The simulation model approximates to the maxillary edentulous alveolar ridge on its morphology. The model is presented, approximates to the pressure-displacement at the masticatory mucosa (alveolar ridge, palate) and lining mucosa. In the process of making impression, the model and any impression material is perfectly separated without the damage of the fine surfaces of the contacting parts and it never cause the electric leak during the study on bearing-stress of basal seat under the denture.From the above results, the reliability of the model could be utilized as the maxillary edentulous alveolar ridge in order to study the impression method and the bearing-stress on basal seat under the denture.

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.

Three dimensional changes in full dentures during processing. Part I Displacements of teeth and deformations of surface contoures.

In this study, the authers set-up the origin and coordinate axes outside of the denture and working cast, and measure the displacements of teeth and deformations of surface contoures during process of full denture construction using heat-curing resin (Acron and Lucitone 199).The conclusions are follows:1. Displacements of teeth1) Horizontal directionIn all dentures, the teeth displace toward inside and forward after cured. The displacement of posterior is larger than the anterior.2) Vertical directionIn all dentures, the teeth displace toward occlusal surface. In upper dentures, the displacement of posterior is larger than the anterior, and in lower dentures, its relation is conversely. After removed from the cast, the displacement is larger than before.2. Deformations of polished surface contoures (in upper denture)In all dentures, the polished surface deformes upward after cured. The deformations in center of palate and posterior border are larger than the others. After removed from the cast, particulary in case of Acron, the polished surface deformes upward more than before.