安氏Ⅰ类错不同垂直骨面型下颌骨形态的比较研究

Morphometric study of the mandible shape of the subjects with Class Ⅰ skeletal pattern in the three verticle facial types

目的用几何形态测量法对不同垂直骨面型下颌骨的形态特征进行比较研究。方法随机选取安氏Ⅰ类错高角、低角和均角儿童的头颅定位侧位片各30张,扫描侧位片后数字化下颌骨的8个标志点,用Procrustes重叠法得出三种下颌骨的平均形状,然后用薄板曲线法和EDMA法比较安氏Ⅰ类错不同垂直骨面型下颌骨的形态特征。结果从低角到高角,下颌骨的形态改变趋势如下:①下颌升支逐渐变短;②下颌角逐渐增大;③颏部逐渐向后向下旋转;④Id-Pg距逐渐增大;⑤Ar点相对于Co点由后向前移位。结论不同垂直骨面型下颌骨的形态存在很大差异。

Objective To investigate the differences of mandible shapes of the subjects with Class I skeletal pattern in the three verticle facial types by geometric morphometrics. Methods The pretreatment lateral cephalograps of 90 skeletal Class I patients （30 hypodivergent, 30 hyperdivergent, 30 normodivergent ）were selected randomly. All cephalographs were scanned, and eight homologous mandibular landmarks were identified and digitized. Average mandibular geometries were generated by means of Procrustes analysis. Thin - plate spline analysis and EDMA was then applied to mandibular configurations to determine local form differences between the three divergent classes. Results With increase of the MP - SN angle, as shown below, the mandblur shape had some changes- gonion angle and the distance of Id -Pg increased, the ramus height reduced, the chin rotated downward and backward, Ar piont relative to Co point moved farward. Conclusion Mandibular shape was different in the three divergent classes.