Periodontal Ligament as a sensory apparaus : A morphological approach to functional property of periodontal nerve terminals

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1. Double staining with non-specific cholinesterase and protein gene product 9.5 (PGP) clearly demonstrated that mechanoreceptors are restricted to the area near root apex while nociceptors are densely distributed throughout the whole length of periodontal ligament.2. In histochemical studies, almost all mitochondria in the axon terminals of Ruffini endings showed intense non-specific cholinesterase. Terminal Scwann cells associated with periodontal Ruffini endings were positive for acid phosphatase.3. The development and maturation process of Ruffini endings were investigated by use of immunohistocheistry and immunocytochemistry for PGP.These processed require the additions of functional stimuli such as tooth eruption and occlusal force.4. The responses of periodontal nerves to experimentally induced occlusal trauma in rat molars were assessed by immunohistochemistry for PGP.By the second day after bite-raising, many Ruffini endings were swollen and their outline were unclear at light … More microscopic level. Under electron microscope, unusual long cytoplasmic projections extended through enlarged slits of Schwann cell covering, and the cavcolac of the Schwann sheaths had decreased in number. Furthermore, from days 2 to 4, thin nerve fibers on the pressure side of the periodontal ligament were oriented irregulary and had a prominet beated appearance. An increase in the beaded nerves occurred in between days 2-4 post elevation, and decreased over the time course. These results suggest celusal trauma induces specific changes in the distribution and shape of nerve terminals in the periodontal ligament.5. For elucidation in the kinds of neuromodulater concerning jaw-reflexes, microinjection with HRP into masseter was done followed by immunocytochemistry for serotonin in cat trigeminal motor nucleus. The HRP-labelled motor neuron formed synapse with serotonin-positive nerve fibers. The results in this study suggest serotonin is one of neuromodulators for control of jaw-movement. Less