[Three dimensional shape measurement of teeth (Part 2). The accuracy of the three dimensional measurement using a laser displacement meter].

The three dimensional shape measurement system of teeth was improved. The system was assembled by using a high precision laser displacement meter and computer controlled scanning machine (CAMM-3). At the fissure of the occlusal plane, the abnormal data caused by multiple scattering of the reflected beam were observed, but they were dissolved by painting the stone model teeth gray and measured by using a laser displacement meter of MD-40 type with a short measurement length. Another error observed when the reflected beam was shielded by the model tooth itself, was corrected by connecting some data which were measured by rotating the teeth model on the gonio stage. A software program was composed to connect the data. The accuracy of measurement of this system was examined on the slope of a 7 abutment tooth. When the model teeth were measured without tilting, the difference between the true value and the measured value was -240 microns (-2.8%). However, by tilting the model teeth +/- 20 degrees on the gonio stage and connecting a couple of data obtained with two tilting angles by means of the software program, the difference was considerably decreased into + 10 microns and the accuracy was + 0.1%.(ABSTRACT TRUNCATED AT 250 WORDS)