Effect of experimental tooth movement on nerve fibres immunoreactive to calcitonin gene-related peptide, protein gene product 9.5, and blood vessel density and distribution in rats.

The effect of experimental tooth movement on nerve fibers immunoreactive to calcitonin gene-related peptide (CGRP) and to protein gene product (PGP) 9.5 were studied, as well as the coincidence of these responses with changes in blood vessel density and distribution in the periodontal ligament (PDL) and pulp of young Wistar rats. The first right maxillary molar was moved mesially by an orthodontic appliance for 3, 7, 14 and 21 days. Sagittal and horizontal serial sections were incubated alternately with antibodies to CGRP, PGP 9.5 and laminin. Nerve and blood vessel density and distribution between the experimental and control sides were compared in the apical and cervical PDL, and in root and coronal pulp. The most pronounced changes occurred in the 7 day group. CGRP and PGP 9.5 immunoreactive nerves in the apical PDL showed increased density, being distributed towards the alveolar bone and frequently found in bone resorption lacunae. Numerous nerve fibres were often present adjacent to hyalinized tissue, but were never found near or within root resorption lacunae. Nerve sprouting was also present both in the root and coronal pulp. Increased nerve and blood vessel density generally coincided with each other. At day 14, periodontal nerves and blood vessels were still disorganized compared with the controls. Tissues near cellular cementum and root resorption lacunae were consistently devoid of nerve fibres. After 21 days, PDL nerve and blood vessel density and distribution were nearly at control level. However, nerve fibres were regularly found inside root resorption areas. In conclusion, experimental tooth movement induces dynamic changes in density and distribution of periodontal and pulpal nerve fibres, indicating their involvement in both early stages of periodontal remodelling and later in the regenerative processes of the PDL, generally occurring in concerted action with modulation of blood vessels.

Trigeminal nerve endings in gingiva, junctional epithelium and periodontal ligament of rat molars as demonstrated by autoradiography.

Tritiated-L-proline was injected into the right Gasserian ganglion of mature rats for incorporation into proteins being carried by rapid axonal transport to nerve endings. The distribution of the nerve endings in molar gingivae and periodontium was subsequently mapped in serial sections by autoradiography. We found that sensory nerve terminals are most prominent in two regions of the free gingiva: (1) In the junctional epithelium there is a rich innervation of the basal epithelial layer with many endings penetrating several cell layers. (2) In the crestal epithelium arborized endings are present, especially on the marginal side of the crest. In the attached gingiva a few terminals are found in the epithelium with more in the lamina propria; the latter appear to be encapsulated. The periodontal ligament is only moderately labeled with silver grains located over nerve bundles, over nerves associated with blood vessels, and over a few apparent endings in the apical region. In the cementum no labeled endings are seen. Labeling of Gasserian cell bodies primarily reveals specific intra-epithelial nerve endings in gingiva crest and junctional epithelium. The absence of major labeling of the periodontal ligament supports the view that many nerves in that region are derived from cell bodies in the mesencephalic nucleus.