| Budget Amount *help |
¥3,200,000 (Direct Cost: ¥3,200,000)
Fiscal Year 1998: ¥500,000 (Direct Cost: ¥500,000)
Fiscal Year 1997: ¥2,700,000 (Direct Cost: ¥2,700,000)
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| Research Abstract |
In this study, the following experiments were performed to investigate the mechanism of pain in the initial stage of orthodontic tooth movement and influences of orthodontic tooth movement on the CNS.
First, the change in the distribution of periodontal nerve fibers containing CORP and CGRP-positive neurons in the trigeminal ganglion during experimental tooth movement were observed in the same rat. Simultaneously, the expression of Heat Shock Protein (HSP)-immunoreactivity in the periodontal cells was also immunohistochemically examined to demonstrate the involvement of peridontal stress in alterations of CGRP-immunoreactive (-IR) nerves in PDL.Furthermore, the temporal changes in the distribution of Fos-like-IR neurons in the trigeminal subnucleus caudalis was investigated. The following results were obtained :
1. At 1hour of tooth movement, the number of CGRP-IR neurons in the trigeminal ganglion began to decrease and reached minimum at 3 hours. Then, the number of CGRP-IR neurons persisted to increase inversly until 12 hours. Finally, no significant difference in the number of neurons showing CGRP-immunoreactivity was recognized between control and experimental groups. On the other hand, CGRP-IR nerves in the PDL showed a tendency to increase slightly from 6 hours of tooth movement.
2. Some peridontal fibroblasts began to show HSP 60-immnoreactivity from 1 hour of tooth movement. The number of HSP-60-IR cells continued to increase until 12 hours, and then decreased gradually.
3. The number of Fos-IR neurons in the trigeminal subnucleus caudalis increased significantly from 1 to 4 hours of tooth movement, reaching maximum at 2 hours, and then decreased by degrees.
These findings suggest that orthodontic tooth movement may cause the stress reaction in the PDL, and that the nociceptive stimuli evoked by orthodontic tooth movement may affect the trigeminal ganglion and the trigeminal subnucleus caudalis through the nerves distributed in the PDL.
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