安氏Ⅱ类患者颅颌面形态的主成分分析

Principal Component Analysis of the Craniofacial Heterogeneity in Subjects with Class Ⅱ Malocclusions

目的:本文应用形态测量学及主成份分析法对安氏Ⅱ类患者的颅颌面形态进行分析。方法:60名安氏Ⅱ类患者的头颅定位侧位片被扫描和数字化后用APS软件进行处理,图像先用最小平方和法进行重叠,然后用主成份分析法对形态差异进行评价。结果:样本总变异的近70%来自于前3个主成份因素,其中第一个主成份因素占到了总形态差异的33.9%,它表达的是颌骨垂直向上的变化;第二个主成份因素约占18.2%,表达了颌骨前后方向的变化;第三个主成份因素约占16.1%,表达了牙槽突的变化。结论:用形态测量学和主成份分析法对头颅侧位片进行群体分析,相对于传统法可以对事物的差异给予更宏观、更全面的分析。

Objective： The purpose of this study was to evaluate the Craniofacial heterogeneity of patients with Class Ⅱ malocclusions by principal components analysis. Methods： A total of 60 cephalograms of patients with Class Ⅱ malocclusions were traced and digitized. Thirteen points were used for the analysis. The tracings were superimposed by the Procrustes method, and shape variability was assessed by principal components. Results： Approximately 70% of the total sample variability was incorporated in the first 3 principal components. The most significant principal component（ PC1 ） ,accounting for 33.9% of shape variability, Was the divergence of skeletal pattern; the second principal component（ PC2 ） , accounting for 18.2% of shape variability, was the anteroposterior mandibulary relationship; the third principal component （PC3）, accounting for 16.1% of shape variability, was the dentoalveolar changes. Conclusion： It is recommended that Procrustes superimposition and principal components analysis should be incorporated into roution cephalometric analysis for more valid and comprehensive shape assessment. This method offers a great advantage over traditional cephalometrics.