The changed expression of CGRP immuno-positive nerve in the periodontal ligament of rat molar during tooth movement

Sung, Jung Ok; Park, Hyo Sang; Bae, Yong Chul; Sung, Jae Hyun

Abstract

Bone resorptiion was predominate in compression site, bone formation in tension site of periodontal ligament during tooth movement. The biologic response at compressiion site was different from tension site. Thus the CGRP immuno-positive nerve fiber will respond differently to mechanical force according to the area(compression or tension site). The purpose of this study was to investigate this response of CGRP immuno-positive nerve fiber in the periodontal ligament according to the duration of applied force and the area (compression or tension site) during experimental tooth movement. The experimental animals were 7 week old male rat (approximately 200 gm), The orthodontic force was applied mesially to the right maxillary molar using the Ni-Ti coil spring during 12 hours, 1, 3, 7, and 12 days. Immunohistochemical staining using antibody against CGRP was performed after sacrifice. The results were as follows. The CGRP immuno-positive nerve bundle showed reduced immunoreactivity and nerve fibers reduced in density after application of orthodontic force for 12 hours and 1 day. The CGRP immuno-positive nerve fibers showed many thin branches at the apical periodontal ligament after application of force for 3 days as compared with normal. The tension site in the apical periodontal ligament showed more branches than the compression site. In 7 day group, the CGRP irnrnuno-positive nerve fibers increased in terms of the number and had many thin branches in the apical periodontal ligament. The tension site had more branches than the compression site, In 12 day group, the CGRP immuno-positive nerve fibers showed similar distribution to normal control at compression site of apical periodontal ligament, but the fibers at the tension site increased in number. The CGRP immuno-positive nerve fibers showed more increased at tension site than compression site after application of orthodontic force. Therefore it seems to have some relation to the bone remodeling besides the local inflammatory process.