Baba M
Aichi Gakuin Daigaku Shigakkai Shi. 1990 Mar;28(1 Pt 2):499-507.
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.
高下颌平面角的上颌前突病例存在一些临床难点。在这类病例中，每个头影测量平面以较大角度展开，咀嚼肌薄弱。由于这些形态和功能异常，容易导致支抗丧失以及支抗牙伸长，而下颌后缩难以改善。通过考虑咬合力如何建立自然支抗，对高下颌平面角的上颌前突病例进行了重新评估。第一个病例显示下颌平面角和咬合平面角较高。使用了短时间的颈带和II类弹力牵引，导致6/6伸长，下颌平面角张开3度。然而，由于下颌升支有一定生长，侧面轮廓并未恶化。第二个病例因异常拔除4/6，下颌平面角未张开。然而，由于是成人病例，骨骼情况没有改善。第三个病例除了肌力较弱外，由于颈带的作用，下颌平面角张开，尽管初始记录显示头影测量数据中没有高角情况。这可能表明头影测量数据不足以评估正畸病例的功能。
