应用3dMD^?面部三维成像系统研究拔牙矫治对青少年骨性Ⅰ类错畸形面部软组织三维特征的影响，为正畸矫治提供参考。

选取2016—2019年期间于中山大学附属口腔医院正畸科就诊的青少年骨性Ⅰ类患者50例，其中拔牙组25例，非拔牙组25例为对照组，应用3dMD^?收集正畸治疗前后的面部三维图像数据，通过3dMD^? vultus软件测量线距、角度、体积变化，应用SPSS 20.0统计分析软件对各项测量指标的比较采用独立样本t检验。

正畸治疗后，在线距方面，拔牙组、非拔牙组前下面高变化量分别为（0.28 ± 2.28）、（1.85 ± 2.18）mm，差异有统计学意义（t = -2.238，P = 0.031）；拔牙组下颌高、颏高、唇宽变化量分别为（-0.52 ± 2.31）、（-1.14 ± 2.64）、（-1.33 ± 3.62）mm，非拔牙组则分别为（1.64 ± 2.42）、（0.93 ± 2.51）、（1.40 ± 2.16）mm，差异有统计学意义（t_下颌高 = -2.878，P_下颌高 = 0.007；t_颏高 = -2.506，P_颏高 = 0.017；t_唇宽 = -2.942，P_唇宽 = 0.006）。在角度方面，拔牙组、非拔牙组鼻唇角变化量分别为4.91° ± 3.12°、1.50° ± 4.26°，差异有统计学意义（t = 2.692，P = 0.011）；拔牙组、非拔牙组颏唇角变化量分别为-0.24° ± 6.83°、4.82° ± 6.50°，差异有统计学意义（t = -2.373，P = 0.023）；拔牙组、非拔牙组唇角变化量分别为-16.80° ± 12.65°、-1.04° ± 11.24°，差异有统计学意义（t = -4.171，P<0.001）。在体积方面，拔牙组、非拔牙组唇部变化量分别为（-0.66 ± 1.24）、（0.46 ± 1.43）cm³，差异有统计学意义（t = -2.584，P = 0.014）；拔牙组、非拔牙组颏部变化量分别为（-0.16 ± 0.94）、（0.65 ± 0.91）cm³，差异有统计学意义（t = -2.766，P = 0.009）。

（1）拔牙与非拔牙矫治对患者面下1/3水平向无明显影响，但对面下1/3的垂直向影响有差异，非拔牙较拔牙矫治更易导致面部高度的增加；（2）开唇露齿的青少年患者经拔牙矫治可有效改善颏、唇部形态；（3）对于面部消瘦、颧部凸出的患者，应慎重拔牙矫治。

In order to provide reference for orthodontic treatment, the three-dimensional characteristics of facial soft tissue of adolescents with skeletal classⅠ were compared between extraction and non-extraction cases based on 3dMD^? 3D facial imaging system.

A total of 50 adolescent patients with skeletal class Ⅰ treated at the Department of Orthodontics of Hospital of Stomatology of Sun Yat-sen University from 2016 to 2019 were selected, including 25 patients in the extraction group and 25 patients in the non-extraction group as the control group. 3dMD^? was used to collect the 3D facial image data before and after orthodontic treatment, 3dMD^? vultus software was used to measure line distance, angle and volume, and the differences between the two groups were analyzed by SPSS 20.0 software.

After orthodontic treatment, the changes in the distance of lower facial height of extraction group and non-extraction group were (0.28 ± 2.28) and (1.85 ± 2.18) mm respectively (t = -2.238, P = 0.031) ; the changes in mandibular height, chin height and lip width of extraction group were (-0.52 ± 2.31) , (-1.14 ± 2.64) and (-1.33 ± 3.62) mm respectively, and those of non-extraction group were (1.64 ± 2.42) , (0.93 ± 2.51) and (1.40 ± 2.16) mm respectively (t_{mandibular height} = -2.878, P_{mandibular height} = 0.007; t_{chin height} = -2.506, P_{chin height} = 0.017; t_{lip width} = -2.942, P_{lip width} = 0.006) . In terms of angle, the changes in nasolip angle of extraction group and non-extraction group were 4.91° ± 3.12° and 1.50° ± 4.26° respectively (t = 2.692, P = 0.011) ; the changes in chin-lip angle of extraction group and non-extraction group were -0.24° ± 6.83° and 4.82° ± 6.50° respectively (t = -2.373, P = 0.023) ; the changes in lip angle of extraction group and non-extraction group were -16.80° ± 12.65° and -1.05° ± 11.24° respectively (t = -4.171, P<0.001) . In terms of volume, the changes in lip of extraction group and non-extraction group were (-0.66 ± 1.24) and (0.46 ± 1.43) cm³ respectively (t = -2.584, P = 0.014) ; the changes in chin of extraction group and non-extraction group were (-0.16 ± 0.94) and (0.65 ± 0.91) cm³ respectively (t = -2.766, P = 0.009) .

(1) There was no significant difference between extraction and non-extraction in the changes of horizontal direction of 1/3 below the face, but there was difference in the vertical direction of 1/3 below the face. And non-extraction was more likely to lead to the increase in face height than extraction. (2) It can effectively improve the shape of chin and lip in adolescent patients with poor lip seal after extraction correction. (3) The patients with thin face and protruding cheekbones should be treated carefully by extraction.