上顎前歯の彎曲徴について

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Muhlreiter (1928) pointed out the curve symbol as one of the methods to identify the rightness or leftness of the tooth. This is an important element in the plaster sculpture, yet the matters relating to the curve symbol such as the angle to compose the curve symbol, its position or the relationship with the adjacent tooth have not been explained at all so far. In order to obtain effective guides for dental anatomy by the study of this subject, the author have investigated the extracted anterior right maxillary teeth, collecting 23 central incisors, 10 lateral incisors and 12 canines. Their crown lengths were transversally separated into 12 sections of even space, the contour line of each separated section recorded by the contracer, and the angles formed by the curvatures from the labial to the mesial direction and that from the labial to the distal direction were also recorded. The date thus obtained were examined from various view points, and the following conclusions have been reached in due consideration : 1. In the study of the contours by the incisal aspect, the average mesial curvature angle of the central incisor is 123.4°, 5.4° less than the distal curvature angle which averages 123.8°. A significant difference is observed between the mesial curvature angle and the distal one, and the latter is greater. In the case of lateral incisor, the average mesial curvature angle is 136.1°, 3.5° less than 139.6° average of the distal one. The difference is not significantly large enough. In the case of canine, the average mesial curvature angle is 128.2°, while the distal curvature angle averages 147.8°. The value of 19.6° between both shows a significant difference, that is, the distal curvature angle is apparently greater. In short, the curve symbol is most apparent in the canine, followed by the central then lateral incisors, but no apparent difference to mention is seen in the lateral incisor. 2. In the positional study of curve symbol of the central incisor, it is seen to be formed in the area between the 3rd and 9th separating lines, the central 2/3 of the crown length slightly closer toward the tooth cervical side. In the case of the lateral incisor, it is formed in the area between the 4th and 9th separating lines, central half of the crown length. In the case of the canine, it is in the area between the 2nd and 8th separating lines, the central area nearly 2/3 of the crown length in the labial surface slightly closer toward the cervical side. 3. We will be able to research detail subjects about the curve symbol of tooth without cutting off it. Because the contour of a incisal ridge-aspect obtained from composition of 12 separated contours, which written by contracer, of crown length of each tooth.
九州歯科学会の論文
1977-03-31

著者

水城和男
九州歯科大学解剖学教室

上顎前歯の彎曲徴について

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