Department of Maxillofacial Surgery, Faculty of Odonto-Stomatology, University of Medicine and Pharmacy at Ho Chi Minh City, Ho Chi Minh City, Vietnam.
Department of Oral Implantology, Faculty of Odonto-Stomatology, University of Medicine and Pharmacy at Ho Chi Minh City, Ho Chi Minh City, Vietnam.
Int Dent J. 2023 Oct;73(5):692-700. doi: 10.1016/j.identj.2023.01.006. Epub 2023 Mar 2.
The early or delayed surgical removal of an asymptomatic lower third molar (M3) in orthodontic patients remains controversial. This study aimed to determine the changes in the impacted level of M3 such as angulation, vertical position, and eruption space, after orthodontic treatment in 3 groups, namely non-extraction (NE), first premolar (P1) extraction, and second premolar (P2) extraction.
Relevant angles and distances related to 334 M3s from 180 orthodontic patients were assessed pre- and posttreatment. Angle between lower second molar (M2) and M3 (M3-M2) was used for evaluating M3 angulation. For M3 vertical position, distances from occlusal plane to the highest cuspid (Cus-OP) and fissure (Fis-OP) of M3 were used. Distances from the distal surface of M2 to anterior border (J-DM2) and centre (Xi-DM2) of the ramus were used for assessing M3 eruption space. Pre- and posttreatment values of the angle and distance in each group were compared using a paired-sample t test. Measurements of the 3 groups were compared using analysis of variance. Hence, multiple linear regression (MLR) analysis was used to determine significant factors that impacted changes in M3s' related measurements. Independent factors used for MLR analysis included sex, treatment starting age, pretreatment respective angle/distance, and premolar extraction (NE/P1/P2).
M3 angulation, vertical position, and eruption space at posttreatment were significantly different from those at pretreatment in all 3 groups. MLR analysis showed that P2 extraction significantly improved M3 vertical position (P < .05) and eruption space (P < .001). P1 extraction significantly decreased Cus-OP (P = .014) and eruption space (P < .001). Treatment starting age was significant factor that affected Cus-OP (P = .001) and M3 eruption space (P < .001).
After orthodontic treatment, M3 angulation, vertical position, and eruption space changed in favour of the impacted level. These changes in the 3 groups were clearer in order: NE, P1, and P2, respectively.
在正畸患者中，尽早或延迟去除无症状的下颌第三磨牙（M3）仍存在争议。本研究旨在确定 3 组患者（非拔牙组、第一前磨牙拔牙组和第二前磨牙拔牙组）正畸治疗后 M3 阻生水平的变化，包括角度、垂直位置和萌出间隙。
评估了 180 名正畸患者的 334 颗 M3 牙的相关角度和距离。M3 与下颌第二磨牙（M2）之间的角度（M3-M2）用于评估 M3 的倾斜度。M3 垂直位置用 M3 牙合面至最高尖牙（Cus-OP）和颊沟（Fis-OP）的距离来评估。M2 远中面至下颌升支前缘（J-DM2）和中心（Xi-DM2）的距离用于评估 M3 的萌出间隙。采用配对样本 t 检验比较每组治疗前后角度和距离的变化。采用方差分析比较 3 组间的测量值。因此，采用多元线性回归（MLR）分析确定影响 M3 相关测量值变化的显著因素。MLR 分析中使用的独立因素包括性别、治疗起始年龄、治疗前各角度/距离和前磨牙拔牙（非拔牙/P1 拔牙/P2 拔牙）。
3 组患者治疗后 M3 的倾斜度、垂直位置和萌出间隙与治疗前相比均有显著差异。MLR 分析表明，第二前磨牙拔牙显著改善了 M3 的垂直位置（P<.05）和萌出间隙（P<.001）。第一前磨牙拔牙显著降低了 Cus-OP（P=.014）和萌出间隙（P<.001）。治疗起始年龄是影响 Cus-OP（P=.001）和 M3 萌出间隙（P<.001）的显著因素。
正畸治疗后，M3 的倾斜度、垂直位置和萌出间隙向阻生水平方向发生了变化。3 组的变化顺序为：非拔牙组、第一前磨牙拔牙组和第二前磨牙拔牙组。
