Abstract: The position sense of the mandible is very acute, and sensory information from peripheral nerve terminals is considered to contribute to this oral sensation. The roles of temporomandibular joint and masticatory muscle proprioceptors were evaluated by the psychophysical technique. The subjects were five healthy volunteers with no abnormalities of the temporomandibular joints, masticatory muscles, or occlusion. After a mandibular position defined as the interincisor distance was presented and learned by the subjects, they were asked to reproduce a subjectively equivalent mandibular position, and the differences in the interincisor distance between the presented and reproduced mandibular positions were evaluated.
1. Changes in the subjectively equivalent mandibular position were studied with and without blocking of articular sensory information by anesthetizing the bilateral temporomandibular joints, but no significant difference was observed between with and without anesthesia.
2. When sensory information from muscle spindles was increased by vibrating the bilateral masseter and temporal muscles, errors were observed in the subjectively equivalent mandibular position: the reproduced interincisor distance was significantly reduced.
These findings suggested that sensory signals from the temporomandibular joints do not contribute to the position sense of the mandible and that awareness of jaw position depends on sensory input from muscle spindles of the masticatory muscles.
