[Case of skeletal open bite treated with orthognathic surgery, with special reference to morphological and functional analysis of the tongue].

Malfunction and abnormal posture of the tongue has been thought to be one of etiological factors for skeletal open-bite at length. In this study, an adult female patient with anterior open-bite is reported, who has been treated by means of posterior maxillary osteotomy and has obtained a good occlusion and profile, which is stable throughout the retention period. Electromyography was obtained from the tongue muscles by surface electrodes and the tongue muscle activity during deglutition was measured before and after surgery. The tongue posture was also analyzed on the basis of the roentgen cephalogram with the mandible at the rest position. Larger tongue muscle activities during swallowing was revealed compared to the control subjects. In addition, anteriorly and superiorly positioned tongue was seen in the initial stage. The amplitudes of the tongue muscle had decreased and tongue posture had shifted posteriorly and inferiorly following surgery, which approximated to the those observed in the control subjects. These improvements of the abnormal activity and posture of the tongue and the stability of occlusion after surgery confirmed that posterior maxillary osteotomy is an effective surgical operation for the anterior open-bite patients in terms of prognosis.