Immunohistochemical study of nerve response in the dental pulp of the rat molar during orthodontics movement

The present study was undertaken to reveal the responses of nerve fibers in the dental pulp of rat molars during tooth movement using immunohistochemistry for protein gene product 9.5(PGP 9.5), a general neuronal marker. Experimental tooth movement was done according to Waldo's method(1953). In control, numerous nerve fibers showing PGP 9.5 immunoreactivity assembled in the subodontoblastic region to form a subodontoblastic nerve plexus in the coronal pulp. Furthermore, many nerve fibers entered the predentin and dentin in rat molars. At 1 day after tooth movement, slight inflammation was recognized near the odontoblast layer, where PGP-positive nerve fibers tended to disappear, especially in the mesial pulp. At 2 days, the inflammation still remained, and a number of degenerated nerve fibers occured throughout the coronal pulp, third days, thick and short nerve fibers increased in number more than those at 2 days after tooth movement, and some fibers showed beaded-appearance. At 5 days after tooth movement, PGP 9.5-positive nerves formed a network structure under the repaired odontoblast layer. At 7 days, the distribution and morphology of nerve fibers became identical to those in control sections. It is concluded that the pulpal nerve fibers can be affected by orthodontic force.