利用三维CT重建术研究面型与下颌骨内部结构的关系

The evaluation of relationship between facial types and the mandible innerstructure by using 3-dimentional reconstruction of CT scan

目的探讨面型与下颌骨内部结构的关系。方法选择30名志愿者,年龄在25-28岁,牙齿排列基本正常。拍摄规格头颅侧位片。根据眶耳平面-下颌平面角(FMA)大小将30名志愿者分成3组:短面型组10人,正常组13人,长面型组7人。拍摄下颌CT片,扫描平面与颌面平行,从髁顶点至下颌下缘,每0.5mm扫一层并进行三维重建。分别测量下颌4个区域(中切牙,第二前磨牙,第一、二磨牙区)的颊舌侧皮质骨厚度,牙齿倾斜度及骨倾斜度。并对结果作组间的对比研究及其与面型参数的相关系数分析。结果各个区域的颊侧皮质骨厚度与面型参数均有相关性。第一磨牙的牙倾斜度、骨倾斜度与面型参数有相关性。短面型组的颊侧皮质骨厚度厚于正常组与长曲型组。短面型组的牙齿比正常组与长面型组更向舌侧倾斜。结论面型与下颌骨体的皮质骨厚度及磨牙的颊舌向倾斜度有相关性。在下颌骨体内部结构与面型之间存在着显著的、复杂的联系。

Objective To investigate the relationship between facial types and the characteristic of mandible （cortical bone thickness, tooth and bone inclination） by using the three-dimensional CT scan. Methods Thirty volunteers were collected. All occlusions were Class Ⅰ or Class Ⅱ with minimal dental crowding. For each subject, a lateral radiograph was taken. The 30 volunteers were divided into 3 groups according to FMA-10 were short -face pattern, 13 were normal and 7 were long-face pattern. And CT scan was made. The plane of the CT scan was parallel to the occlusal plane. Cuts of 0.5 mm were taken from the Condylion to the mandibular plane. Three-dimensional reconstruction was performed. The following measurements were made in the regions of incicor;second molar;first and second molars：cortical bone thickness; buccolingual inclination of tooth and bone. Then the study of correlation coefficients was made between parameters of facial type and the characteristic of the mandible, as well as the comparison study among 3 groups. Results The buccal bone thickness of all sections were associated with parameters of facial type. The angle represented by Frankfort horizontal plane to mandibular plane was associated with tooth and bone inclination of the M1 section. The buccal cortical bone was thicker in short-faced individual than in the average and long-faced groups. Teeth in the short-faced group inclined more lingually than in the average and long-faced groups. Conclusion The morphological features that relate to masticatory function and facial types are associated with cortical bone thickness of the mandibular body and the buccolingual inclination of the molars. The results of this study suggest that a significant but complex relationship exists between structures of the mandibular body and facial types.