Study on the morphologic change of periodontal mechanoreceoptor after orthodontic force in rat

Objective To observe the morphologic change of the periodontal mechanoreceptor by using the PGP9.5 immunohistochernistry staining method. Methods 30 adult male SD rats were divided into 6 groups randomly, and each group had 5 rats. The mesial tensile force of about 0.49 N was applied on URM1, and the rats ware executed at 3 d, 21d,and 7 d, 14 d, 21 d, 28 d after removal of the force. Then tissue blot containing the molar and its surrounding alveolar bone were harvested, fixed, and sliced, then had PGP9.5 immunohistochemistry staining, observed the change in the morphology, distribution and density of the Ruffini nerve fiber on the pressure side, the percentage of surface area occupied by swollen and hazy contoured mechanoreceptor, and t test were analyzed. Results Compared to the control group, at 3 d and 21 d after orthodontic teeth movement, most of the PGP9. 5-immunoreactive nerve fibers in the rats had swollen and hazy contour(P<0.05). After removal of the force that had been applied for 21 d, swollen and hazy contoured mechanoreceptor started to descend. But after 28 d removal of the orthodontic force, this type of mechanoreceptor had not recovered to the normal level (P < 0.05). Conclusions The orthodontic force leaded the emergency change similar damage of PDL nerve fiber. The change of nerve may be not permanent. Key words: PDL Ruffini nerve fiber;  PGP9.5;  Orthodontic force