Influences of periodontal and mandibular-joint receptors on reflex sensitivity of human jaw-closing muscles.

Reflex sensitivity from stimulating the chin or the dental arch of the mandible and the influences of periodontal and mandibular joint receptors on jaw muscles were investigated by experiments with and without anaesthesia. The findings showed that periodontal receptors exert an inhibitory influence on motoneural excitability of jaw-closing muscles and facilitate alpha-motoneurones of the digastric muscle and that the silent period following a jaw jerk is partly caused by inhibition of alpha-motoneurones of jaw-closing muscles due to activity of periodontal receptors. The ratio of reflex activity in temporal and masseter muscles appeared to depend on the position of the applied stimulus. The mandibular joint receptors appear to play a major part in distributing active muscle-force over these muscles.