The analyses of Extraordinary Excitability or Pain in the Jaw and Neck Muscles due to the Pulpal and/or Periodontal Diseases

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Neck and/or Jaw muscle pain is sometimes observed in patients suffering from pulpal and/or periodontal diseases. It is reasonable to consider that these symptoms were caused by the extraordinary excitability of the muscles. The purpose of this research project was to elucidate the muscle pain mechanisms. In a clinical study, the electromyogram of neck and jaw muscle was analyzed in human subjects, and in a basic study, the neurophysiological mechanisms underlying these symptoms were studied in animal experiments. The conclusions were as follows :1. The electromyograms of the masseter muscle(MM)and the sternocleidomastoid muscle(SCMM)were obtained with surface electrodes on both sides in healthy subjects and temporo-mandibular joint dysfunction(TMJD)patients. (1)The SCMM activity corresponded to the MM one in healthy and TMJD subjects, when they moved the mandibular without food rhythmically. (2)In healthy subjects, the SCMM activity was also corresponded to the MM one in case of mastication. While, in TMJD subjects, the former was rather active during the whole stage. of masticatory movement, and showed no harmony with the latter.2. The cervical inferior alveolar nerve-driven neurons(IANDN)were searched for in cats anesthetized with alpha-chloralose, and their response properties were analyzed in respects to the peripheral inputs. (1)Some of the IANDNS were identified as the spino-thalamic neurons(IAND-STN)using collision test. (2)These neurons seemed to relay the sensory information from the tooth pulp or the periodontal tissue. (3)Onto the non-projection IANDN, neck muscle inputs were converged. It might be occurred that neck muscle sensory inputs'integrated into the trigeminal ones in the cervical spinal cord.These results suggest that extraordinary trigeminal sensory inputs may evoke the abnormal reflex resulting in the neck muscle excitation.