Evaluation of stomatognathic functions through analysis of head movement : A new concept

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The coactivation of mastication and neek muscles during functional and rhythmical mandibular movements has been demonstrated. We hypothesized that the head moves rhythmically and coordinately with the mandibule during function. To prove the validity of our hypothesis we examined the existence of periodicity of head movement during tapping. Healthy male adults, mean age 25.5, with normal occlusion and without TMD history were selected as subjects. Using photo-electrical measuring system, we measured tridimensionally both the movement of the head and mandible by tracking upper and lower incisal points respectively during tapping movements.The head moved periodical and rhythmically, as the mandible does. The upper incisal point moved in opposite direction to the mandible. During opening the head moved in a cranial direction ; during closing moved in a caudal direction. The cycle time of head and mandibular movements showed a correlation coefficient of o.94. The average vertical range of movement for the head was1.2(]SY.+-。[)0.6mm, and 16.9(]SY.+-。[)3.0mm for the mandible. The range of head movements were proportional to those of the mandible with a correlation cofficient of 0.74.From these results we conclude that during tapping the head moves in functional coordination with the mandible movement.