[Three-dimensional shape measurement of teeth. (6) Measurement of tooth model by tilting method by means of the double sensor laser displacement meter, and the simulation of occlusion].

Abstract

To measure the three-dimensional shape of the undercut portion of a molar model tooth, the tilting method was used. The measuring system was composed of a laser displacement meter with double sensor and a computer controlled tooth model scanning machine (CAMM-3). A model tooth was tilted on the gonio stage with +/- 20 degrees and measured divisionally, and a couple of data were connected by the TILCOMPO program. The undercut portions from the survey line to the tooth neck were measured and drawn by CG. By this tilting method, the whole shape of tooth including the undercut portion could be measured, and these data will be available for the production of the data base for CAD of prosthesis. The marginal line on the crown abutment measured previously was searched. Initially, the difference in the inclination dz/dx between the data before and behind was calculated, and the gingival line was extracted by limiting its value. Then, also by limiting the difference value, the margin located above the gingival line was determined. Thus the marginal line in contact with the inner and outer crown and a significantly important point for the production of crown by the CAD/CAM technique could be determined around the crown abutment. Another elementary attempt to simulate the occlusion by using the data of teeth models measured on the articulator was carried out. The maxillary and mandibular teeth were set on the articulator and the maxillary teeth turned over. The shapes of the 5-7 upper and lower molar were measured. The two data were connected and occluded by the "OCCLUS" program.(ABSTRACT TRUNCATED AT 250 WORDS)