Private practice, Seoul, Korea.
Latin American Research Center, Asunción, Paraguay; Department of Orthodontics, Seoul Saint Mary's Hospital, Catholic University of Korea, Seoul, Korea.
Am J Orthod Dentofacial Orthop. 2019 Aug;156(2):178-185. doi: 10.1016/j.ajodo.2018.08.024.
This study aimed to identify significant factors affecting the spontaneous angular changes of impacted mandibular third molars as a result of second molar protraction. Temporary skeletal anchorage devices in the missing mandibular first molar (ML-6) or missing deciduous mandibular second molar (ML-E) with missing succedaneous premolar spaces provided traction.
Forty-one mandibular third molars of 34 patients (10 male and 24 female; mean age 18.3 ± 3.7 years) that erupted after second molar protraction were included in this study. They were classified into upright (U) and tilted (T) groups. Linear and angular measurements were performed at the time of treatment initiation (T1) and of ML-6 or ML-E space closure (T2). Regression analyses were used to identify significant factors related to third molar uprighting.
Nolla stage (odds ratio [OR] 4.1), sex (OR 0.003 for male), third molar angulation at T1 (OR 1.1), missing tooth space (OR 0.006), rate of third molar eruption (OR 23.3), and rate of second molar protraction (OR 0.2) significantly affected third molar uprighting. Age, third molar angulation at T1, rate of third molar eruption, and rate of second molar protraction were significant factors for predicting third molar angulation at T2.
Available space for third molar eruption before and after second molar protraction is not associated with uprighting of erupting third molars. Older patients whose third molars are in greater Nolla stage, are in a more upright position at T1, and have a greater eruption rate have a greater chance for third molar uprighting. Alternatively, an increase in second molar protraction rate results in mesial tipping of the third molars.
本研究旨在确定影响下颌阻生第三磨牙在第二磨牙远中移动后自行发生角度变化的显著因素。缺失下颌第一磨牙（ML-6）或缺失下颌乳第二磨牙（ML-E）中临时骨锚定装置（TAS）与缺失的继生前磨牙间隙一起提供牵引力。
本研究纳入了 34 名患者（10 名男性，24 名女性；平均年龄 18.3 ± 3.7 岁）的 41 颗下颌阻生第三磨牙，这些患者在第二磨牙远中移动后萌出。它们被分为垂直（U）和倾斜（T）两组。在治疗开始时（T1）和 ML-6 或 ML-E 间隙关闭时（T2）进行线性和角度测量。回归分析用于确定与第三磨牙直立相关的显著因素。
Nolla 分期（比值比 [OR] 4.1）、性别（男性 OR 0.003）、T1 时第三磨牙角度（OR 1.1）、缺牙间隙（OR 0.006）、第三磨牙萌出率（OR 23.3）和第二磨牙远中移动率（OR 0.2）显著影响第三磨牙直立。年龄、T1 时第三磨牙角度、第三磨牙萌出率和第二磨牙远中移动率是预测 T2 时第三磨牙角度的显著因素。
第二磨牙远中移动前后第三磨牙的萌出空间与第三磨牙直立无关。年龄较大的患者，Nolla 分期较高，T1 时位置更垂直，萌出率更高，第三磨牙直立的机会更大。相反，第二磨牙远中移动率的增加会导致第三磨牙向近中倾斜。
