[Study of three-dimensional changes in the permanent bases of complete dentures after secondary heat treatment]

Points on tissue surfaces of 15 pairs of complete denture have been measured before and after second time processing by using three coordinate measuring machine (contactable style). 49 points on the upper dentures and 55 points on the lowers are selected to be measured. The findings are as follows: (1) Existence of the trend of shape distortion. The difference of the changes between dentures are quite large. In the upper dentures, the palatal areas bend upward while the bilateral flanges rotate inward and downward. In the lower dentures, the lingual parts distort downward and the buccal parts distort upward. (2) The distributing pattern of the dimensional changes. In the upper dentures the changes are obviously in front, central palatal areas and the flanges. In the lower dentures, the rear parts change most. Therefore this dimensional changes are in three different axes. The result shows that it is hardly to compare with that of the studies on discrepancy.