[Linear correlation between tooth movement and facial profile change in patients with class Ⅱ division 1 malocclusion].

Objective: To investigate the correlation between tooth movement and profile change in patients with class Ⅱ division 1 malocclusion. Methods: Pre- and post-treatment lateral cephalograms of 42 patients [10 males and 32 females, (23.8±6.3) years old, mean treatment time: 1.9 years] with class Ⅱ division 1 malocclusion were collected in Department of Oral & Cranio-Maxillofacial Surgery, Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine from June 2012 to November 2017. The patients were treated with extraction of four first premolars or two maxillary first premolars. Cephalometric analysis was carried out before and after treatment. Thirty parameters were measured. The changes of soft and hard tissue after orthodontic treatment and their correlations were analyzed using bivariate linear regression. Related factors affecting the upper and lower lip, nasolabial angle (NLA) and mentolabial angle (MLA) were analyzed according to the standardized regression coefficient (Beta). Results: Among all the 30 parameters, 18 parameters were statistically different before and after treatment. After treatment, upper central incisor sagittal distance [(63.87±7.14) mm] and upper lip sagittal distance [(77.73±7.60) mm] were significantly decreased (P<0.05). The changes in 14 parameters after treatment showed linear relationship including strong positive correlation between upper lip sagittal retraction and upper central incisor sagittal retraction (r=0.649, P<0.01). There were moderate positive correlations between upper lip and upper central incisor vertical movement (r=0.544, P<0.01). While the sagittal change of gnathion and the Y-axis angle showed moderate negative correlations (r=0.537, P<0.01). The stepwise multiple linear regression showed that the retraction of upper lip process was correlated with the retraction of upper central incisor, the increase of occlusal plane angle and the increase of upper central incisor angle, which was most correlated with the retraction of upper central incisor (Beta=0.79). The downward displacement of upper lip process was correlated with the downward displacement of upper incisor, the decrease of upper central incisor angle, the decrease of the distance between maxillary first molar and palatal plane, and the increase of occlusal plane angle, which was more correlated with the downward displacement of upper incisor and the increase of occlusal plane angle (Beta=0.59). The downward displacement of lower lip process was correlated with the downward displacement of upper incisor and lower incisor, which was more correlated with the upper incisor (Beta=0.36). Conclusions: The relationship among nose, lips and chin was more coordinated. Incisor retraction had significant influence on lip prominence, and the lower lip position was highly related to the movement of upper incisor in sagittal and vertical dimension after orthodontic treatment in patients with class Ⅱ division 1 malocclusion. However, tooth movement had limited impact on the chin position.目的： 通过对Ⅱ类1分类错牙合患者正畸治疗前后的头影测量指标进行相关性分析，探讨影响面部软组织侧貌变化的相关因素。 方法： 选取2012年6月至2017年11月于上海交通大学医学院附属第九人民医院口腔颅颌面科就诊的42例已完成正畸治疗的Ⅱ类1分类错牙合患者［男性10例，女性32例，年龄（23.8±6.3）岁，平均矫治时间1.9年］，拔除4颗第一前磨牙或2颗上颌第一前磨牙后进行正畸治疗纠正磨牙关系，测量矫治前后硬组织及软组织相关头影测量指标30个，包括上下唇突点、颏唇沟点、软硬组织颏前点及颏顶点的矢状向及垂直向距离、鼻唇角及颏唇角等。对矫治前后各指标变化量进行线性回归分析，根据标准化回归系数（Beta）分析影响上下唇、鼻唇角、颏唇角等面部软组织的主要相关因素。 结果： 30个头影测量指标中18个矫治前后差异均有统计学意义（P<0.05），与矫治前相比，矫治后上中切牙点矢状向距离［（63.87±7.14） mm］、上唇突点矢状向距离［（77.73±7.60） mm］显著减小（P<0.05）。14对头影测量指标变化量间存在线性关系，其中上唇突点矢状向变化量与上中切牙点矢状向变化量强正相关（r=0.649，P<0.01），上唇突点垂直向变化量与上中切牙点垂直向变化量中度正相关（r=0.544，P<0.01），软组织颏顶点矢状向变化量与Y轴角变化量中度负相关（r=0.537，P<0.01）。多元逐步后退回归分析显示，上唇突点内收量与上中切牙点内收量、牙合平面角增大量以及上中切牙角增大量均相关，且与上中切牙点内收量相关性最大（Beta=0.79）；上唇突点下移量与上中切牙点下移量、上中切牙角减小量、上颌第一磨牙牙合面中点到腭平面距离减小量以及牙合平面角增大量相关，且与上中切牙点下移量及牙合平面角增大量的相关性最大（Beta均为0.59）；下唇突点下移量与上、下中切牙点下移量相关，且与上中切牙点下移量相关性更大（Beta=0.36）。 结论： Ⅱ类1分类错牙合矫治后鼻唇颏关系得到一定改善，切牙的矢状向变化对唇突度的影响最大，且下唇矢状向与垂直向移动与上中切牙的位置关系更密切，牙齿移动对颏部的影响有限。.