A study of process of growth of oral form and oral function by newly developed device

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Mandibular movements are often used as indices of the functioning of the stomatognathic system. The conventional divisions are habitual chewing movement, slide movement and border movement. The mandibular border movement may be restricted by bone, mandibular articulation, the neurotransmission system for muscles, ligaments or other soft tissues of the stomatognathic system. This system is immature in children, so some difference is expected between the movements of children and adults and between each occlusal developmental stage.The ranges of back and forth, right and left and upper and lower movements of mandibular incisal points and the mandibular rotary ranges were measured in six boys and six girls in the deciduous dental arrangement stage, six boys and six girls in the mixed dental arrangement stage, and six boys and six girls in the permanent dental arrangement stage, using the six degrees of freedom for mandibular movement previously developed by the authors. Differences between sexes and between the dental arrangement stages were compared and the following conclusions made :1. In dental arrangement stages for boys, no differences were observed in the back and forth or frontal rotary ranges between the deciduous and mixed arrangement stages. For girls, the ranges of incisal point movements were greater in the mixed than in the deciduous dental arrangement stage and in the permanent than the mixed arrangement stage.