Morphology of neural endings in the human periodontal ligament: an electron microscopic study.

The ultrastructure of sensory nerve endings in the human periodontal ligament from 43 extracted teeth was studied using serial sections. Three types of nerve endings were found: free nerve endings (FNE), Ruffini-like endings and lamellated corpuscles. Free nerve endings stem from unmyelinated or from myelinated nerve fibers. The endings contain neurotubuli, neurofilaments and vesicles. Ruffini-like receptors were mostly found in the apical part of the periodontal ligament. In these Ruffini-like receptors a particularly abundant concentration of mitochondria appears. In some cases desmosome-like junctions are present between neurite and ensheathing cell. Lamellated corpuscles were also found in the periodontal ligament. The lamellae are extremely endocytotic and are in close contact with each other.