Expression of c-Fos Like Protein in the Rat Brain Following the Tooth Movement by Differential Orthodontic Force

Abstract

The purpose of this study was to establish an objective method to evaluate pain, which occurs during the movement of experimental tooth using the presence of c-Fos, intranuclear protein of proto-oncogene c-fos, in central nervous cells due to irritation involving the periphery as a marker.
The distribution of c-Fos-immunoreactive cells which would appear following the proximal movement of the upper left first molar in rats was studied immunohistochemically. Furthermore, the effects of different orthodontic forces (0, 10, 30 and 90g) on the number of immunoreactive cells at Sp 5 C (layer I & II) which is the pain receptor neuron in the area of the jaw and face were studied. The effects of indomethacin on the number of immunoreactive cells that would appear were also studied.
Under the 10 g orthodontic force, immunoreactive cells were observed in Sp5C and the nuclei concerned with descending system for the modulation of pain at LRt, PGi, Arc, DR and CG. No immunoreactive cells were detected in Sp5I and Sp50. When the animals were pretreated with indomethacin, no immunoreactive cells were detected in Sp5C and the nuclei concerned with descending system for the modulation of pain described just above. When the molars were moved proximally, immunoreactive cells in Sp5C were detected in the dorsolateral and lateral areas on the tooth movement side. They were detected only in the dorsolateral area on the contralateral side. Appearance of immunoreactive cells in the above various nuclei is probably because prostaglandin was produced in the periodontal tissues due to orthodontic irritation.
The number of immunoreactive cells in Sp5C increased as orthodontic force increased. These result suggest that this method could become a tool for objective evaluation of pain that occurs during experimental tooth movement.