Application of an image-analysis system to prosthodontics--measurements of human facial profiles and upper central incisor teeth.

The profiles of the face and upper central incisor tooth surface are known to be similar. This study evaluated the accuracy of an image-analysis device, which was then used for quantitative analysis of facial and tooth profiles.The device consisted of a CCD TV camera, a shade corrector, a video recorder, an image-analyzer (PIAS Co., Model LA-500) and a microcomputer (NEC Co., Model PC-9801 VX 2).Squares (150mm×150mm and 10mm×10mm) and a metal coin (diameter 20 mm) were used for evaluation of the system's ability. The measurement procedures were as follows : 1) The squares and the coin were measured to obtain values of area and perimeter length, and 2) study models of 6 volunteers, 1 female and 5 males, between the ages of 25 and 30 years, were assessed by measurement of individual face and tooth profiles.The average error rate was less than 5% for the squares and the coin. The average ratio of the long axis of the face to that of the tooth was 1/19, and that of the short axes 1/16.