| Co-Investigator(Kenkyū-buntansha) |
FUJITA Yukihiro Tokyo Medical and Dental University, Faculty of Dentistry, Lecturer, 歯学部, 講師 (50192729)
ISHIDA Tetsuya Tokyo Medical and Dental University, Faculty of Dentistry, Lecturer, 歯学部, 講師 (80211043)
IIDA Junichiro Tokyo Medical and Dental University, Faculty of Dentistry, Associate Professor, 歯学部, 助教授 (90151232)
TAKANO Yoshiro Tokyo Medical and Dental University, Faculty of Dentistry, Professor, 歯学部, 教授 (90126425)
NAKAMURA Yoshio Tokyo Medical and Dental University, Faculty of Dentistry, Professor, 歯学部, 教授 (10010026)
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| Research Abstract |
The purpose of this research is to clarify the dynamic change of periodontal mechanoreceptors before and after orthodontic treatment by means of biomechanical, physiological and immunohistological approaches.
1. Biomechanical approach
We improved occlusal force sensor (the core of the sensor was a pressure sensitive rubber) which was designed to measure the momentarily changing occlusal force of the whole dentition. That is to say, we devised this sensor of small size to measure tooth one by one. And we measured the occlusal force onto each tooth when functioning.
The minute displacement of the maxillary central incisor was measured three dimensionally indirectly with optic fiber sensor. According to different spots where external force Was applied, the pattern of displacement varied, and the phenomenon that center of rotation of the tooth changed could be observed. Also, we measured the displacement of the maxillary first molar when clenching with direct-contact minute displacement devic
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e. It indicated that different contact pattern between the upper and lower first molars resulted in varied tooth displacement pattern.
2. Physiological approach
The main innervation nerves of periodontal mechanoreceptors of rats are A delta fibers. In contrast with incisors, of mixed fast-adapted and slowly-adapted types, only fast-adapted types can be found in molars. Moreover, as for the change in adaptive characteristics of periodontal mechanoreceptors of rats after antagonists were extracted, change of threshold in response to mechanical stimulation could be seen, and the change of proportion of reaction patterns could also be observed. Furthermore, in mice, the nerve transmission substances necessary for mastication changed with growth.
3. Immunohistological approach
2,4,6 and 8 weeks after we set a device onto the lower incisors of mice of 3 weeks old after birth to induce anterior crossbite, and another 2,4,6 and & weeks after the device used for inducing anterior crossbite was removed, we utilized immunohistological method to observe the distribution and morphological change of Ruffini nerve endings by PGP- 9.5. As with anterior crossbite was induced, the Ruffini nerve endings located at the palatal sides of the periodontal membranes of the anterior maxillary incisors degenerated and lessened. However, in the case that anterior crossbite ameliorated after the appliance was removed, Ruffini nerve endings regenerated. Thereby, we confirmed the correspondence between change of occlusion and periodontal mechanoreceptors. Less
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