The aims of this study were to evaluate the effect of inferior alveolar nerve (IAN) axotomy on periodontal (PDL) and pulpal blood flow incident to experimental tooth movement and to investigate whether nerve fiber regeneration coincides with blood now changes. The first right mandibular molar was moved mesially for 3, 7, and 14 days after ipsilateral IAN axotomy in 29 rats. Four rats served as unoperated controls., At the end of each experimental period fluorescent microspheres (FM) were injected into the left ventricle and thereafter counted in serial sections in the PDL and pulp of the right and left first mandibular molars. The number of FM per tissue volume was taken as a measure of blood now. Re-innervation of nerve fibers was mapped immunohistochemically 7, 14, and 21 days after IAN axotomy in 9 rats that had no orthodontic appliance. The statistical analysis showed no significant differences in the number of FM/mm(3) PDL between the denervated and the contralateral side at 3 and 7 days. At 14 days the PDL on the denervated side showed a significant increase in the number of FM/mm(3), coinciding with the initial periodontal nerve fiber re-innervation. In the pulp no significant differences were found between the denervated and the contralateral, innervated side in any experimental period. It can be concluded that IAN axotomy postpones an increase in periodontal blood now until a sensory tissue re-innervation is established, thus indicating that neurogenic mechanisms play an important role in the development of the inflammatory reaction induced by experimental tooth movement.