Effects of dental trauma on pulpal and periodontal nerve morphology

Regeneration and morphological changes in sensory peptidergic nerves in pulp and periodontium were studied after general dental trauma by means of immunohistochemistry. In control teeth also the total nerve supply was demonstrated by using antibody to the general neuronal marker, protein gene product (PGP)9.5. Two experimental rat models were used, i.e. tooth replantation and induced traumatic occlusion. Results from these studies are reviewed here. In the controls, the PGP9.5-immunoreactive(IR) nerve supply in pulp and periodontium was generally denser compared to CGRP-IR and SP-IR nerves. In the replanted teeth, regeneration of CGRP-IR nerves closely followed the pulp cell renewal. Density and distribution of the regenerated nerves showed two different patterns which seemed to depend on the capacity of the renewed pulp to form postoperative dentine. The nerve density never reached the same level as the controls. In teeth not able to form irregular dentine, the pulp was sparsely innervated and the pulp cavity was filled with innervated bone. Nerve responses in CGRP-IR and SP-IR nerves after unilateral induced traumatic occlusion in the first maxillary molar were studied at different observation periods up to 30 days. After 5 days, localized morphological nerve changes were found both in the pulp and periodontium within the total rat molar dentition. With increasing observation periods, the pulpal neural changes progressed and were extended to all pulpal areas compared to the periodontium, where the nerve responses remained localized to cervical and apical tissues throughout the experiment.