Innervation of teeth and periodontium after enzymatic removal of collagenous elements

Abstract

1. 1. The innervation of human and monkey teeth and their periodontium was studied by Pearson's silver gelatin method. The jaws and teeth were fixed in a formol-acetic acid-alcohol mixture, decalcified, dehydrated, and embedded in nitrocellulose in the usual manner. The embedded specimens were sectioned at 25 to 100 micra, and the cut sections were exposed to enzymatic hydrolysis before silver impregnation. 2. 2. The common pulpal nerve arises as a union of the branches of the various dental nerves which enter the apical periodontal membrane of all the surfaces surrounding the tooth. In the coronal portion of the pulp the common pulpal nerve breaks up into cuspal nerves which course toward the cuspal horns. The termination of these nerves is mainly in the odontoblastic layer; however, a few nerves enter the predentine, where they form a loop to return to the odontoblastic layer. 3. 3. The nerve supply to the periodontal membrane arises from the dental and interalveolar nerves, branches of the alveolar nerves. The dental nerve fibers supply the periapical region and pass gingivally to form a united bundle with the perforating branches of the interalveolar nerves. 4. 4. Two types of nerve endings are found in the periodontal membrane. (1) Nonmedullated nerve fibers may unite at their terminals to form an arborization. Fine delicate fibrils arise from this network to end as “free nerve endings” among the stroma cells, cementoblasts, and cementum. (2) Medullated fibers may lose their myelin sheath, and the naked fibrils terminate into an elongated spindlelike structure. 5. 5. Gingival innervation is derived from two sources: (1) fibers arising from the nerves of the periodontal membrane and (2) fibers originating from the labial or palatal nerves. As these fibers pass through the connective tissue, terminal twigs are given off which supply the tunica propria. Intrapapillary and intraepithelial nerve endings are scarce in the epithelial attachment and marginal gingiva. On the other hand, attached gingiva contains both types of nerve endings.