Department of Orthodontics, School of Dentistry, National and Kapodistrian University of Athens, Athens, Greece.
Center for Advanced Dental Education, Department of Orthodontics, Saint Louis University, Saint Louis, USA.
Eur J Orthod. 2019 May 24;41(3):264-272. doi: 10.1093/ejo/cjy056.
To evaluate the hard tissue and facial profile changes in matched extraction and non-extraction Class I patients by the use of geometric morphometrics.
From a parent sample of 542 Class I patients, previously subjected to discriminant analysis, a subsample of 68 borderline cases was obtained, 34 treated with extraction and 34 without extraction of 4 first premolars. Geometric morphometric methods (Procrustes superimposition and Principal Component Analysis) were applied on cephalometric tracings to assess the validity of the discriminant analysis in successfully identifying a morphologically homogeneous group and to evaluate inter- and intra-group skeletal and facial profile shape changes.
No significant pre-treatment shape difference between the two groups was found, thus validating the discriminant analysis. The non-extraction group showed increase in hard tissue facial height (P < 0.001), with slight lower lip retrusion and upper lip protrusion (P = 0.027). The extraction group showed retraction of the hard tissue and facial profile outline (P < 0.001). Permutation tests for post-treatment inter-group differences resulted in P = 0.054 for the soft tissue outline and P = 0.078 for the hard tissue skeletal component.
The evidence indicates that borderline cases treated with four premolar extractions will exhibit lip retrusion compared to non-extraction treatment.
运用几何形态测量学评估拔牙和非拔牙矫治的Ⅰ类患者的硬组织和面部侧貌变化。
从先前经过判别分析的 542 例Ⅰ类患者的原始样本中，选取 68 例临界病例作为亚组，其中 34 例接受了 4 颗第一前磨牙的拔牙矫治，34 例接受了非拔牙矫治。通过几何形态测量法（Procrustes 叠加和主成分分析）对头颅侧位片进行分析，以评估判别分析是否能成功识别形态学同质组，并评估组内和组间骨骼和面部轮廓形状的变化。
两组间治疗前的形状差异无统计学意义，从而验证了判别分析的有效性。非拔牙组的硬组织面高增加（P < 0.001），下唇轻度后缩，上唇前突（P = 0.027）。拔牙组的硬组织和面部轮廓外形出现回缩（P < 0.001）。治疗后组间差异的置换检验显示，软组织轮廓的 P 值为 0.054，硬组织骨骼成分的 P 值为 0.078。
有证据表明，与非拔牙矫治相比，接受四颗前磨牙拔牙矫治的临界病例会出现唇部后缩。
