頬と舌が歯と歯周組織に与える影響に関する実験的研究 : 頬, 舌圧の排除による歯の挺出移動について

Abstract

The purpose of this study was to investigate the effect of the cheek and tongue pressures on the vertical position of tooth. The lower 2nd and 3rd premolars of adult dogs are in disocclusion with their antagonists. The cheeks and tongue are presumed to interpose between the upper and lower teeth. In order to investigate the effect of the elimination of the cheek and tongue pressures, a cheek-and-tongue guard was applied with the lower right canine and 1st molar as anchorage. Twenty one adult dogs were employed for this experiment. Six dogs were used as the pre-experimental group. The 4 experimental groups and a control group with three dogs per group were investigated at 7- 30- 60- and 90 day intervals after appliance setting during the experiment. Upon completion of the experiment, the changes occurring in the 2nd and 3rd premolars and in the periodontal tissues were investigated histopathologically and compared with those of controls. The results obtained were as follows : 1. Setting of the appliance to eliminate the cheek and tongue pressures displaced the teeth in the experimental and non-experimental sides and caused changes in the periodontal tissues. 2. The tooth movement was mainly elongation movement with most teeth showing lingual and some buccal inclination on the experimental side. On the non-experimental side, the tooth movement was mainly buccal inclination with an apical quater of the root as the central axis. 3. The tooth movement due to the elimination of the cheek and tongue pressures was observed histologically 7 days after the appliance setting. 4. On the experimental side, the peakof alveolar bone changes to adapt to the tooth movement was observed at 30 days, and stabilization of the alveolar bone in the new tissue environment was not yet observed 90 days after the appliance setting. 5. On the non-experimental side, the peak of alveolar bone changes to adapt to the tooth movement was observed at 30 days, and the alveolar bone was beginning to stabilized in its new position. The above results histopathologically substantiate the clinical opinion that "In the case that a tooth is in disocclusion with its antagonist as in open bite, the interposition of soft tissue is one cause." The results also prove that soft tissue is one of the factors for stabilizing the vertical tooth position. It was confirmed that the cheeks and tongue play very important roles in the vertical stabilization of the tooth.