Department of Orthodontics, Stomatology Hospital, Guangxi Medical University, Nanning, Guangxi, China.
Department of Implant Dentistry, Stomatology Hospital, Guangxi Medical University, Nanning, Guangxi, China.
Am J Orthod Dentofacial Orthop. 2021 Sep;160(3):423-429. doi: 10.1016/j.ajodo.2020.08.018. Epub 2021 May 26.
The objective of this research was to study the factors associated with the alveolar bone depth mesial to the mandibular third molars (M8) after the mandibular second (M7) and third molars were protracted into the space of the mandibular first molars (M6), which were newly extracted for orthodontic treatment or extracted more than 1 year before treatment.
This retrospective study included 57 adult patients (mean age 23.40 ± 4.40 years) in whom M6 were newly extracted for orthodontic treatment or extracted more than 1 year before treatment. The alveolar bone depth mesial to M8 was measured on posttreatment panoramic radiographs. The vertical, horizontal, and angular changes of M8 were measured on both pre- and posttreatment panoramic radiographs. Linear correlation and regression analyses were conducted to explore the factors associated with the alveolar bone depth mesial to M8.
The alveolar bone conditions of M6 (R= -0.391, P <0.001) and the vertical movement directions of M8 (R= -0.433, P <0.001) were significant factors associated with the alveolar bone depth mesial to M8 after orthodontic protraction.
Without considering the pretreatment periodontal status of M8, patients with M6 extracted exceeding 1 year before treatment and with M8 extruded after orthodontic protraction may exhibit deeper alveolar bone depth mesial to M8.
本研究旨在探讨下颌第二磨牙（M7）和第三磨牙（M8）被牵引至下颌第一磨牙（M6）间隙后，与 M8 近中牙槽骨深度相关的因素，这些 M6 是为正畸治疗而新拔除的，或在治疗前 1 年以上被拔除的。
这是一项回顾性研究，共纳入 57 名成年患者（平均年龄 23.40 ± 4.40 岁），这些患者的 M6 因正畸治疗而新拔除，或在治疗前 1 年以上被拔除。在治疗后全景片上测量 M8 近中牙槽骨的深度。在治疗前后的全景片上测量 M8 的垂直、水平和角度变化。进行线性相关和回归分析，以探讨与 M8 近中牙槽骨深度相关的因素。
M6 的牙槽骨状况（R= -0.391，P <0.001）和 M8 的垂直移动方向（R= -0.433，P <0.001）是与 M8 近中牙槽骨深度相关的显著因素。
不考虑 M8 的治疗前牙周状况，在治疗前 1 年以上拔除 M6 并进行正畸牵引后，M8 外展的患者可能会出现 M8 近中牙槽骨深度更深。
