The Relation Ship Between the Changes of Facial Form and the Changes of Lip Pressure of Pre-and Post-Orthodontic Treatment.

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The purpose of this study is to evaluate the relationship among the changes of tooth position, the changes of facial form and lip pressure of pre-and post-orthodontic treatment. The reliability and measurement accuracy of moire topography in three dimensional assessment of the human face were discussed and this method appeared to be suitable to analyze the face. The devices employed in this study were pressure transducers using resistance-strain gauges.The following results were obtained.1. The pre-treatment lip form related to the position of lower incisors in anterior cross bite patients. But in post-treatment the lip form related to the position of the upper incisors. The upper lip pressure of post-treatment showed a tendency of higher labial pressure than the pre-treatment, but lower lip pressure of the post-treatment showed a tendency of lower labial pressure than the pre-treatment.2. The changes of the soft tissues were highly correlated with the changes of hard tissues in surgical orthodontic treatment. In post-treatment Upper lip pressure increased and lower lip pressure decreased than the pressure of pre-treatment.This study demonstrated that the lip pressure was one of the factors of making the dental arch form, and the tooth position or the arch form after orthodontic treatment functinally suitable to the new oral conditions.