Development of the three-dimensional evaluation method for alveolar ridge and denture of elderly people and its application

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In this study, the three-dimensional coordinate measuring machine Tristation 600 (NIKON) was examined as the three dimensional evaluation method for the alveolar ridge and dentures using the touch probe (the tip is a sphere of the 0.5mm diameter) which is more useful it measures the center of the sphere as control point. The coordinate system was set using the center point in the globe division (the 4mm diameter) given for the 3 places of the palate of the maxilla edentulous model (402U, NISSIN). X-Y reference plane was set as the plane that passed through these three points. X-axis was parallel the straight line through the rear two points. The origin of this coordinate was the center of the circle that passes through these three points. The reference points were given 11 points in mucosal surface of the upper complete denture and 5 points on the artificial tooth (central incisor, primary bicuspid of right and left, second molar of right and left). These points were set as a hemispher … More ical dent of the 2mm diameter. The accuracy of this measuring method was 5.6 μ m on the X-axis, 2.9 μ m on the Y-axis, 4.7 μ m on Z-axis in the mucosal surface. On the occlusal surface, it was 5.6 μ m on the X-axis, 3.7 μ m on the Y-axis, 7.5 μ m on Z-axis. These values of this method were sufficient for the three-dimensional evaluation method. The measuring periods were the time of working cast, wax denture, just after curing, one day after the water storage, and the storage of 1 week.In order to examine the dimensional accuracy of the complete upper denture with various forms of elderly people, the maxilla edentulous ridge models with U-shape, which had high, middle and low alveolar ridge, were made. On these models, the specimens were cured by heat curing method (JIS) and microwave curing method.As a result of this study, the thickness of each part greatly influenced in the deformation after the curing of complete upper dentures in either curing method. Furthermore it was suggested the degree of the absorption of an alveolar ridge was more affective for the distortion of upper complete dentures comparing to the height of the palate. It was clear that in the microwave curing method, the distortion of mucosal surface of dentures after curing was smaller than that in the heat curing method. Furthermore these distortion in the microwave curing method was less influence than that in heat cured method. Less