A STUDY OF TOOTH MOBILITY

Abstract

Two types of apparatus have been available for measuring the tooth mobility : one was devised by Dr. Fuse and the other by Drs. Kimura and Ishibashi, the latter being an application of dial gauge generally used in engineering. The author, for his own purpose, undertook to improve the Fuse's instrument for more accurate and more magnified measurement of tooth mobility and has succeeded in making the one with 52.8-fold magnification of tooth mobility. This was named Fuse-Urakami Tester according to the agreement between two authors. By the trial measurements of tooth mobility using Kimura-Ishibashi tester and Fuse-Urakami tester in parallel, it was noticed that besides four common factors which had been regarded to have influences on the tooth modility, i. e. the length of tooth root, the length of tooth crown, the dimension of tooth root surface within the alveolar bone and the breadth of periodontal membrane, four more factors had to be taken into concideration, i. e. the depth of gingival pocket, the changes in elasticity of fibre of periodontal membrane, the changes of rotating axis of tooth root and the errors due to difference of instrument used for measurement. It was generally accepted that the depth of gingival pocket ranging from 1 to 2 millimeter was physiologically normal. Our experiments, however, have shown that the teeth surrounded by the gingival pocket 1 to 2 millimeter deep were already losing their normal elasticity which is indispensable in the masticatory function. After the preliminary experiments the following items were studied, i. e., variability in the tooth mobility measurements due to such various factors as (1) difference of instrument used, (2) the position of load applied on the individual tooth, (3) magnitude of the load applied, (4) the direction of the force exerted forward and backward, (5) sex difference, (6) right and left half of dental arch, (7) difference between mandibular and maxillar teeth, (8) age difference and lastly, (9) the depth of gingival pocket. The results obtained were summarized as follows. 1) Variability between the instrument devised by Kimura-Ishibashi and that devised by Fuse-Urakami. The tooth mobility by linguo-labial force (by drawing) measured by the Kimura-Ishibashi apparatus was larger than that measured by the Fuse-Urakami apparatus, but by labio-lingual force exserted on the tooth surface (by pushing) the tooth mobility was larger in Fuse-Uragami apparatus than in Kimura-Ishibashi apparatus. Besides this characteristic, it might be generally concluded that the Kimura-Ishibashi apparatus as compared to the Fuse-Uragami apparatus has certain theoretical weakness, though it is more handy in manipulating than is Fuse-Uragami apparatus. 2) The tooth mobility of left upper incisor in a 24 years old male subiect was studied in each case of loading at three different points of the labial surface, i. e., at the incisal margin, at the center of the surface and at the tooth neck. The tooth mobility was largest at the incisal margin, followed by at the center, and was smallest at the tooth neck. 3) The tooth mobility increased as the load applied was increased. 4) When the tooth was loaded in linguo-labial direction (drawn anteriorly), the mobility was larger than when the tooth was pushed in labio-lingual direction (posteriorly). 5) Of the mobilities of anterior teeth, that of lower incisor was the largest, followed by lower lateral incisor and that of lower cuspid was the smallest. There was no sex difference in this respect. 6) There was no remarkable difference in the tooth mobility between anterior teeth of same name on the right and left dental arch in subjects of both sexes, and in the maxilla as in the mandible. 7) Also there was no remarkable difference in the tooth mobility between the same named teeth in the maxilla as well as in the mandible. 8) The tooth mobility of anterior teeth in the female subjects

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