歯の生理的移動についての実験的研究 : 近遠心的移動について

Abstract

Although it is generally known that human teeth must have drifted after eruption toward the mesial direction, little has been reported on the physiologic tooth drift. The purpose of this study is to reseach the influence of the forces presumed to be participating in the physiologic tooth drift over the alveolar bone (cheeks, tongue, antagonists, neighbours and gingival fibers group) histopathologically. Twenty-two adult dogs with permanent dentitions were selected. The upper right 1st, 2nd and lower 3rd molars, and lower right distal root of 1st molars were extracted. A cheek-and-tongue guard for lower 2nd molar was applied with the mesial section of lower 1st molar as the abutment tooth. Four experimental groups with 3 dogs or more per group were investigated at 7-, 30-, 60-, and 90-day intervals after appliance setting. Other 5 dogs were used as the control without extractions and appliance setting for the 90-day period. Uppon completion of the experimental period, the changes occurring in the right and left 2nd molars and in the periodontal tissues were investigated histopathologically and compared with those of controls. The results obtained were as follows : 1. Setting the appliance to eliminate the antagonists, neighbour teeth, soft tissues and cutting the gingival fibers group displaced the teeth on the experimental side and caused changes in the periodontal tissues but did not displace obviously in the non-experimental side. 2. The direction of the tooth drift was mainly distal and elongation on the experimental side. 3. The tooth drift was observed at 7 days histopathologically and the tooth drift due to elimination was observed at 30 days in the fluorescent findings after appliance setting. 4. The peak of alveolar bone changes to adapt to the tooth drift was observed at 30 and 60 days after the appliance setting, and stabilization of the alveolar bone in the new tissue environment was not yet observed at 90 days after appliance setting. The above results histopathologically substantiate that some or all forces presumed to be participating in physiologic tooth drift (the soft tissues, antagonists, neighbour teeth and gingival fibers group) have something to do with the tooth drift as the inhibitory force. The results also prove histopathologically that the forces from these factors are indispensable to the stability of tooth position after orthodontic treatment.