Schmid W, Mongini F, Felisio A
University of Turin, School of Dentistry, Italy.
Am J Orthod Dentofacial Orthop. 1991 Jul;100(1):19-34. doi: 10.1016/0889-5406(91)70045-X.
The purpose of this article was to assess and quantify the different components that can lead to mandibular asymmetry in a person during or at the end of growth and to investigate the extent to which improvement can be obtained in the different situations. Three boys and 17 girls, 8 to 21 years of age, with facial asymmetry and chin deviation were selected. Posteroanterior cephalometric radiographs were taken in intercuspal position. On each radiograph, three mandibular points (menton, gonion or antegonion, and articular point) were selected to define a mandibular area. A vertical axis of reference was also determined. Computer-aided design was employed to develop two systems (A and B) to assess a symmetry degree of the mandible. With system A, the left mandibular area was rotated around the vertical axis of reference, and the degree of the superimposition between the left and right areas was plotted. With system B, the left area was rotated around an axis that ran through menton and was perpendicular to a line connecting the two articular points of the mandible. Also, in this case, the degree of superimposition between the two areas was plotted. With system A, the degree of superimposition was a function of mandibular position and mandibular symmetry. With system B, it was a function of mandibular symmetry only. Thus through comparative examination of the data, assessment of displacement asymmetry and structural asymmetry was possible. In two patients, only displacement asymmetry was present, whereas 14 patients showed various features of structural asymmetry. The patients were treated with orthopedic splints to keep the mandible in a position of symmetry. Orthodontic treatment followed so that the intercuspal position would finally coincide with the position of symmetry. Computer-aided design analysis was performed again after a mean observation period of 41.1 months. In 11 patients an improvement in symmetry was observed with both systems. The patients in whom no improvement of structural asymmetry was observed showed a relatively high degree of symmetry at the beginning or had a considerably higher age than the mean age of the whole group. The clinical implications of the data are discussed.
本文旨在评估和量化在生长期间或生长结束时可能导致个体下颌不对称的不同组成部分，并研究在不同情况下能够改善的程度。选取了3名男孩和17名女孩，年龄在8至21岁之间，均存在面部不对称和颏部偏斜。在牙尖交错位拍摄后前位头影测量片。在每张X线片上，选取三个下颌点（颏下点、下颌角点或下颌角前切迹点以及关节点）来界定一个下颌区域。还确定了一条垂直参考轴。采用计算机辅助设计开发了两个系统（A和B）来评估下颌骨的对称程度。在系统A中，左侧下颌区域围绕垂直参考轴旋转，并绘制左右区域之间的重叠程度。在系统B中，左侧区域围绕一条穿过颏下点且垂直于连接下颌骨两个关节点的直线的轴旋转。同样，在这种情况下，也绘制两个区域之间的重叠程度。在系统A中，重叠程度是下颌位置和下颌对称性的函数。在系统B中，它仅是下颌对称性的函数。因此，通过对数据的比较检查，可以评估移位不对称和结构不对称。在两名患者中，仅存在移位不对称，而14名患者表现出各种结构不对称特征。对这些患者使用矫形夹板治疗，以使下颌保持在对称位置。随后进行正畸治疗，以使牙尖交错位最终与对称位置重合。在平均观察期41.1个月后再次进行计算机辅助设计分析。在11名患者中，两个系统均观察到对称性有所改善。未观察到结构不对称改善的患者在开始时具有相对较高的对称性，或者年龄比整个组的平均年龄大得多。文中讨论了这些数据的临床意义。
