Inferior alveolar nerve transection inhibits increase in osteoclast appearance during experimental tooth movement

To evaluate the role of sensory nerve innervation in alveolar bone remodeli ng during experimental tooth movement, we investigated histomorphometricall y the influence of sensory nerve denervation on bone metabolism. Seven days after inferior alveolar nerve (IAN) transection or a sham operation in rat s, orthodontic force was applied to the animals by inserting an elastic mod ule interproximally between the lower first molar acid second molar. Twenty -four hours after the application of the orthodontic force, osteoclast numb er, osteoclast surface, and osteoblast surface were measured on the trabecu lar bone surface in the interradicular septum of the lower second molar. Th e distribution of sensory nerve fibers immunoreactive to antibody against c alcitonin gene-related peptide (CGRP) was also evaluated. In the sham-opera ted rats, CGRP-immunoreactive nerves were observed to he distributed along the blood vessels in the trabecular alveolar bone. Experimental tooth movem ent resulted in a fivefold increase in the number of osteoclasts and in inc reased immunoreactivity of nerves to anti-CGRP in the trabecular bone. Howe ver, IAN transection depleted the immunoreactivity to anti-CGRP and reduced the osteoclast number and osteoclast surface significantly, On the other h and, in the rats that were not subjected to experimental tooth movement, th ere was no significant difference in osteoclast number between sham-operate d and IAN-transected rats. Significant changes were not observed in osteobl ast surfaces associated with experimental tooth movement or nerve transecti on. These findings suggest that sensory nerves play an important role in re gulating bone resorptive activity during experimental tooth movement. (Bone 26:663-669; 2000) (C) 2000 by Elsevier Science Inc. All rights reserved.