Three dimensional shape measurement system for residual ridges.

It is very important for design and construction of complete dentures to evaluate the condition of residual ridges of edentulous patients objectively and precisely. The authors have been developing a shape measurement system for residual ridges. In this study, the outline of the system is described and the accuracy of the system is evaluated. The system consists of a high precision laser displacement meter, a working table and its controller, and a personal computer. The working table, on which a plaster model is placed, can move until the end of the moving range at a speed of 0.7 mm/sec. The height of the plaster model was measured intermittently with a frequency of 7 points/sec. To determine the accuracy of this system, experimental plaster models, which simulated the simplified shape of residual ridge, were measured and analyzed. The measurement error was 2.5%, which seemed to be highly accurate. The accuracy of the measurement decreased with the darkness of the color of the plaster model.