Analysis of residual ridges and ridge relationship by three-dimensional reconstruction method.

The purpose of this study was to develop a diagnostic system with which to determine the adequate area for artificial tooth arrangement on the posterior residual ridge. Edentulous plaster models and occlusion rims were measured by a non-contact type shape measurement system. Three trigonal pyramids and their impressions on the occlusion rims were used as landmarks for the analysis and superimposition of the analysis results for the upper and lower ridges. The data points were obtained at intervals of 0.5 mm in the lateral direction and of 0.25 mm in the anteroposterior direction, and were interpolated by cubic spline curves in the lateral direction. When the ridge contour of the reconstructed image came in contact with the tangent line inclined at 30 degrees to the tentative plane of occlusion at the buccal and lingual sides in the frontal section, the area between their points of contact on both sides was comparatively flat and was regarded as adequate for the artificial posterior tooth arrangement in this study. This diagnostic system seems to be useful in determining the adequate area for the artificial tooth arrangement on the posterior residual ridges of edentulous plaster models and in displaying their horizontal relationship.