モアレトポグラフィによる叢生歯列の上顎前歯部唇面観の三次元的検索

抄録

To assess the form of the upper anterior teeth of normal dental arch and crowded dental arch, a three-dimensional study on the frontal view of the gnathostatic model was made by Moire topography. Standard Moire photographs of the upper anterior teeth in 137 students' (adults) gnathostatic models were taken, and the three-dimensional coordinate values of 6 points in each tooth were measured. Of the subjects, 31 students whose over-bite and over-jet relationships appeared to be normal and the crowding scores less than 3 were regarded as the normal group and morphological investigations were made in that group. Using all the subjects, correlations among the three-dimensional coordinate values, the crowding score, and the dento-alveolar discrepancy in the anterior teeth were examined. The subjects were classified into 3 groups according to the crowding score, group A (32 students, crowding score : less than 3), group B (61 students, crowding score : 4∿7), and group C (44 students, crowding score : more than 8), and a comparision was made by the three-dimensional coordinate values of each point. The following results were obtained. 1. In the lateral inclination of the labial surface of the crown in the normal group, the central and lateral incisors showed a slight mesial inclination to the perpendicular position and the canine showed a steep mesial inclination of 80 degree, while in the anteroposterior inclination of the labial surface of the crown, they showed a slight posterior inclination (central incisor : 87.5°, lateral incisor : 87°, and canine : 85°). 2. The position of incisal edge and the anteroposterior inclination of the labial surface of the crown of the lateral incisor and canine were highly correlated with those of the central incisor in normal group. 3. Central incisor and canine tended to locate anteriorly in a crowded dental arch, and lateral incisor tended to locate posteriorly in the group C : however, its degree was slight from the point of the apical base. 4. The deepest point of gingival margine of central incisor and canine tended to locate upward as the degree of crowding increased and this tendency was significant in group C. 5. No correlation was found between inter-canine width and the degree of crowding. However, a significant correlation was found between inter-canine width and the combined width of six anterior teeth in normal group. 6. When viewed in the anteroposterior inclination of the teeth from the superiorinferior position of the most protruded point of the crown, a great difference between groups A and B was found in the central incisor and a steep labial inclination was found in the group B. In the lateral incisor, there was a great difference between groups B and C and a steep lingual inclination was found in the group C. 7. The coordinate value of the Z of each measuring point was highly correlated with U-1 to FH on the standard cephalogram, showing a higher coefficient of correlation than with the index for the degree of crowding.