Distribution of organized sensory nerve endings in the human periodontal ligament

The purpose of the present study was to clarify the distribution pattern of organized nerve endings in human-periodontal ligament. The materials investigated were obtained from the first premolar teeth. The fresh periodontal ligament of the extracted tooth was stained using the methylene blue vital staining method. Then the whole-mount preparations of the periodontal ligament were observed by light microscope. Three kinds of receptors (encapsulate corpuscles, bush-like endings and free-nerve endings) were located in the ligament. The ratio of total number of encapsulated corpuscles to bush-like endings was one to three. The density of the encapsulated corpuscles ranged from 0.2/mm2 to 1.2/mm2 and the bush-like endings ranged from 1.3/mm2 to 3.2/mm2. The most organized nerve endings were distributed at the middle one third in the ligament. The distribution of bush-like endings, which differed from that of encapsulated corpuscles, might contribute to their response thresholds and static properties.