Impaction of mandibular third molars after orthodontic treatment by the edgewise method: a retrospective study

Abstract This study aimed to determine the incidence of mandibular third molar (M3) impaction after orthodontic treatment by edgewise appliances, and identify possible determinant factors of M3 impaction. A retrospective cohort study was conducted with 1154 patients. Complete orthodontic records were analyzed pretreatment and posttreatment, considering the following variables: type of Angle malocclusion, treatment with or without extraction of first premolars, overbite, stage of dentition, M3 prior angulation and duration of orthodontic treatment. Impaction was determined after radiographic evidence of total closure of the root apex. The chi-square test and Poisson regression (p

摘要 本研究旨在明确采用方丝弓矫治器（edgewise appliances）实施正畸治疗后，下颌第三磨牙（mandibular third molar, M3）阻生的发生率，并探寻M3阻生的潜在影响因素。本研究纳入1154例患者开展回顾性队列研究，对正畸治疗前后的完整正畸诊疗记录进行分析，所考察的变量包括：安氏错𬌗畸形（Angle malocclusion）类型、是否拔除第一前磨牙（first premolars）矫治、覆𬌗（overbite）程度、牙列阶段（dentition stage）、治疗前M3倾斜角度以及正畸治疗时长。以根尖（root apex）完全闭合的影像学表现作为M3阻生的判定依据。本研究采用卡方检验（chi-square test）与泊松回归（Poisson regression）进行统计学分析（p