[Morphological basis of periodontal nerve endings].

The periodontal ligament, a dense collagenous tissue between tooth and alveolar bone, receives a rich sensory nerve supply, and contains two kinds of sensory receptors; nociceptor and mechanoreceptor. The mechanical stimuli for teeth can evoke various oral reflexes, which facilitate mastication via the periodontal mechanoreceptors. In spite of many reports on the periodontal sensory receptors, recent studies have revealed that the Ruffini endings, categorized as low-threshold slowly adapting type II (SA II) stretch receptors, are primary mechanoreceptors in the periodontal ligament. This paper summarized recent findings on the morphological features and developmental aspects of the periodontal Ruffini endings.