[Some characteristics of orthodontic treatment in high mandibular cases]

Maxillary protrusion cases with a high mandibular plane angle have some clinical difficulties. In such cases, each cephalometric plane spreads out with large angles and masticatory muscles are weak. Due to these morphological and functional abnormalities, anchorage loss as well as elongation of anchor teeth is easily caused and retrusion of the mandible is hard to be improved. Maxillary protrusion cases with a high mandibular plane angle were reestimated through a consideration of how natural anchorage is established by occlusal force. The first case showed a high mandibular plane and occlusal plane angles. Cervical head gear and class II elastics were used for a short period of time, which caused elongations of 6/6 and the opening of the mandibular plane angle by 3 degrees. The lateral profile, however, did not worsen since the mandibular ramus had a fair growth. The second case showed no opening of the mandibular plane angle as the result of an unusual extraction of 4/6. There was, however, no skeletal improvement because of an adult case. The third case showed the opening of the mandibular plane angle from the effect of the cervial head gear besides a weak muscular force, although the initial record revealed no high angles in cephalometric data. It may be suggested that cephalometric data are not enough to estimate function of orthodontic cases.