不同垂直骨面型正常人切牙区颌骨形态结构的聚类分析

目的　研究正常人上下颌切牙区颌骨的形态结构特征及其与垂直骨面型的关系。方法　运用聚类分析的方法,在X线头颅侧位片上对169例恒牙列初期正常人的切牙区颌骨形态进行聚类,并分析其与垂直骨面型的关系。结果　①正常人上下颌切牙区颌骨形态分为Ⅰ、Ⅱ、Ⅲ、Ⅳ4个聚类分型。上颌切牙区颌骨Ⅰ型宽短;Ⅱ型瘦长;Ⅲ型厚度与Ⅱ型接近,高度与Ⅰ型接近;Ⅳ型与Ⅲ型形态相反,厚度与Ⅰ型接近,高度与Ⅱ型接近。下颌切牙区颌骨Ⅰ型宽短;Ⅱ型瘦长;Ⅲ型形态宽长,厚度接近Ⅰ型,高度接近Ⅱ型;Ⅳ型形态适中。②在上颌,高角面型以Ⅱ型为主,占86·49%;均角面型以Ⅲ型为主,占47·67%;低角面型以Ⅰ、Ⅲ型形态为主,共占82·61%。在下颌,高角面型以Ⅱ型为主,占51·35%;均角面型以Ⅳ型为主,占48·84%;低角面型以Ⅲ、Ⅳ型为主,共占69·57%。结论　对不同的切牙区颌骨聚类分型形态和垂直骨面型,临床移动切牙时应有不同的考虑。

K-mean Cluster Analysis for Incisal Jaw Morphology of Normal Occlusion Subjects among Different Vertical Facial Skeletal Types

OBJECTIVE: To study the incisal jaw morphology of subjects with normal occlusion and to discuss the relationship between different vertical facial skeletal types and different incisal jaw cluster types. METHODS: After studied by radiographic cephalometry, the incisal jaw morphology of 169 subjects with normal occlusion in early permanent dentition were analyzed by K-mean cluster analysis. RESULTS: Morphology of maxillary or mandibular incisal jaws could be divided into four types separately, including division I, division II, division III and division N. In maxilla or in mandible, the incisal jaw morphology of division I was characterized by wideness and shortness. In contrast, division II was characterized by thinness and length. As for division III and division IV, both of two were intermediate types between division I and division II . In maxilla, it was found that division II was the majority (86.49%) in the high-angle subjects, division III was the majority (47.67%) in the average-angle subjects, and division I and III were the majority (82.61%) in the low-angle subjects. In mandible, it was found that division II was the majority (51.35%) in the high-angle subjects, division IV was the majority (48.84%) in the average-angle subjects, and division III and IV were the majority (69.57%) in the low-angle subjects. CONCLUSION: Owing to the obvious characteristics of morphology in each cluster types and in each vertical facial skeletal types, different clinic considerations must be put forward when we want to move the incisor.