Morphological approach to the clucidation of recognition of recognition mechanism of periodontal sensation: Immunohistochemical and electron microscopic study.

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In order to clarify the biological property of periodontal sensory receptors, Ruffini endings in the periodontal ligament of rats were examincd by immunohistochemistry, histochemistry and transmission electron microscopy, whereby it resulted that:1. The periodontal Ruffini endings were ultrastructurally characterized by the expanded axon terminals filled with a large number of mitochondria and covered with a thick Schwann sheath, over which a the multiple layer of amorphous substances was observed. The Schwann sheath covering was discontinuous, so that the finger-like projections of the axoplasm,i.e. axonal spines, were exposed to the surrounding tissues through the slits of the Schwann sheath. Electron microscopic observation of specimens stained with tannic acid revealed that the axonal spines were not in direct contact with the surrounding periodontal collage fibers.2. By immunostaining with antibody to laminin, the amorphous structure around the axon terminals of Ruffini endings was clearly identified as the basal lamina. Since laminin is known to be involved in cell adhesion, the multiple-layered basal lamina would serve as an adhesive structure between the periodontal fibers and the axon terminals of Ruffini endings. This would bring an explanation as to the reason by which periodontal sensation is highly sensitive.3. Histochemical stainings disclosed intense cytochrome oxidase and acid phosphatase activities as well as nonspecific cholinesterase activity in periodontal Ruffini endings.4. The maturation of the periodontal Ruffini endings seemed to require functional stimuli such as tooth cruption and occlusion.5. During experimental tooth movement, the distribution of periodontal nerves drastically changed due to mechanical force.6. In osseointegrated tissues, no formation of recognition mechanism was observed around implant materials.