The Effect of Basic Mandibular Movement on the Head and Trunk

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The purpose of this study was to investigate the effect of basic mandibular movement on the head and trunk and determine the relationship between the range of mouth opening and the range of head or trunk movement. The head moved backward during mouth-opening and moved forward during mouth-closing, when the subjects were standing. The body moved forward as mouth opened and backward while the mouth closed. The width of mouth opening was significantly correlated with the range of head and trunk movement. During open-close mandibular movements, associated head and trunk movements were observed. When the mouth opened, the head tilted backward, resulting in a shift of balance with the weight of the head over the cervical segments. To compensate for the backward head motion, the body tends to move forward, and vice versa. Also, a wider opening of the mouth was correlated to a larger range of head and trunk movements. These findings suggest that head and trunk movements facilitated smooth movement of the jaws.