State Key Laboratory of Oral Diseases and National Clinical Research Center for Oral Diseases, West China School of Stomatology, Sichuan University, Chengdu, Sichuan, China.
State Key Laboratory of Oral Diseases and National Clinical Research Center for Oral Diseases, Department of Prosthodontics, West China Hospital of Stomatology, Sichuan University, Chengdu, Sichuan, China.
BMC Oral Health. 2020 Nov 11;20(1):321. doi: 10.1186/s12903-020-01314-0.
Based on low-dose radiation Cone-bean computed tomography (CBCT) images, This study aims to establish a space coordinate system, which offers more precise and comparable evaluation on changes of maxillary third molars influenced by orthodontic treatment with premolar extraction in adults. The system suggests promising application prospect in future studies related to CBCT superimposition and evaluation for its feasibility and efficiency.
Forty-nine maxillary third molars from 27 patients (mean age, 20.78 years) were included. CBCT images were obtained before and after orthodontic treatment with premolars extracted (mean treatment duration, 31.47 months). The changes in the position, angulation, and rotation of the third molars were evaluated with a space coordinate system using four landmarks: anterior nasal spine (ANS), posterior nasal spine (PNS), left and right orbitales.
After orthodontic treatment, the third molars moved forward (adjusted mean, 1.44 mm) (p < 0.001) and downward (adjusted mean, 2.87 mm) (p < 0.001) accompanied by outward rotation of the crowns (adjusted mean, 5.38°) (p = 0.001), while changes in angulation were insignificant.
This was the first study to systematically investigate the spatial position change of maxillary third molars in adult patients who received orthodontic treatment with premolar extraction. During the process, maxillary third molars moved downward and forward accompanied by outward rotation of the crowns. Orthodontists should take tooth movement potential into consideration when making extraction plans.
基于低剂量辐射的锥形束 CT（CBCT）图像，本研究旨在建立一个空间坐标系，为成人正畸治疗中拔除前磨牙后上颌第三磨牙的变化提供更精确和可比的评估。该系统具有较高的可行性和效率，在未来涉及 CBCT 叠加和评估的研究中具有广阔的应用前景。
纳入 27 名患者（平均年龄 20.78 岁）的 49 颗上颌第三磨牙。在拔除前磨牙的正畸治疗前后（平均治疗时间 31.47 个月）均获得 CBCT 图像。使用四个标志点（前鼻棘、后鼻棘、左右眶），通过空间坐标系评估第三磨牙位置、角度和旋转的变化。
正畸治疗后，第三磨牙向前移动（校正均值，1.44mm）（p<0.001）和向下移动（校正均值，2.87mm）（p<0.001），同时伴随着冠部的外旋（校正均值，5.38°）（p=0.001），而角度的变化不显著。
这是第一项系统研究成人患者在接受拔除前磨牙的正畸治疗后上颌第三磨牙空间位置变化的研究。在此过程中，上颌第三磨牙向下和向前移动，并伴有冠部的外旋。正畸医生在制定拔牙计划时应考虑牙齿移动的潜力。
