Three-dimensional quantification of color-marked occlusal paths on anatomically oriented casts

Statement of problem. The analysis of occlusal contacts on mounted diagnost ic casts is an important task in prosthetic diagnostics. However, it is sti ll restricted mainly to qualitative aspects because existing measuring tech niques fail to provide 3-dimensional data for more than a few single points in acceptable time. Purpose. The aim of this study was to develop a method for quantifying occl usal contacts and paths by using anatomically oriented diagnostic casts and to design the method to allow fast acquisition of digital 3-dimensional co ordinates. Material and methods. Plaster casts with color-marked contacts were digitiz ed optically with a profilometric system based on the fringe projection tec hnique. Digital camera images taken simultaneously were used to define the contact areas by marking them either manually or automatically with the hel p of image-processing routines. Three-dimensional coordinates were determin ed by finding the corresponding points within the profilometric data set. Results. Color-marked contact areas on diagnostic casts were successfully d igitized with a computer-controlled, automatic setup in approximately 30sec onds. The accuracy of the acquired 3-dimensional data was estimated to be b etter than 60 mum in lateral and 30 mum in height resolution. The data set was visualized and evaluated in a skullrelated coordinate system. Summary. This study verified the use of a new tool to quantify color-marked occlusal contacts on diagnostic casts in terms of spatial coordinates. The resulting digital data may be stored easily and analyzed numerically as we ll as visualized 3-dimensionally with computer graphic equipment. Because t he anatomic orientation of the casts is maintained throughout the measureme nt process, it is possible to compare the data with electronically register ed condyle paths and therefore to investigate, for example, their relation to the corresponding guidance paths of the frontal teeth and the canines in dynamic occlusion.