The reinnervation of healing extraction sockets in the ferret

The objective of this study was to describe the pattern of healing of pulpal and periodontal nerve fibers following tooth extraction. The mandibular canine teeth were, under general anesthesia, removed from one side of nine young ferrets. One week (two animals), one month (four animals), and three months (three animals) later, again under general anesthesia, the animals were perfused with fixative. The mandibles were decalcified, paraffin-embedded, and serially sectioned. Sample sections were stained with hematoxylin and eosin, the remainder with a silver stain for nerves. Serial reconstructions were made of the innervation in control teeth and in the extraction sockets. A grid sampling technique was used for the estimation of the innervation density in different regions at various levels in the healing socket. One week after extraction, although osteoid material was beginning to fill the socket, the pattern of innervation remained similar to that of controls in being restricted to the former location of the periodontal ligament and being densest in the apical third of the socket. One month after extraction, the innervation consisted of many fine axons or small bundles distributed throughout the healing osteoid tissue though still most dense in the periphery of the socket. The overall innervation density increased between one week and one month post-extraction. At three months, as the margins of the socket were becoming obscured, the innervation consisted largely of one or two organized nerve trunks running from the apical to the coronal aspect in either the central or lateral aspects of the socket. At no time was there evidence of neuroma formation.