The purpose of this study was to identify pretreatment factors associated with the stability of early class III treatment, since most orthodontists start the treatment with their uncertain hypotheses and/or predictions. Subjects consisted of 75 patients with a class III skeletal relationship (ANB < 2° and overjet < 0 mm) who had been consecutively treated with rapid maxillary expansion and facemask and followed until their second phase treatment. The patients were divided into two groups according to whether they showed relapse in follow-up. The stable group maintained their positive overjet (n = 55), and the unstable group experienced relapse with a zero or negative overjet (n = 20). Two general, three dental, and 13 cephalometric pretreatment factors were investigated to determine which factors were associated with stability. Sex, pretreatment age, and anteroposterior functional shift, which were hypothesized as associated factors, were not related to the stability of early class III treatment. Significant differences were detected between the two groups in the horizontal distance between the maxillary and mandibular molars in centric relation. Cephalometric variables, such as the mandibular length (Ar-Me), Wits appraisal, SN to ramus plane angle (SN-Rm), gonial angle, incisor mandibular plane angle (IMPA), and Frankfort plane to mandibular incisor angle (FMIA) showed significant differences between the groups. The horizontal distance was the most influential factor by logistic regression analysis. Hypothesis (related to sex, age, functional shift) were rejected. Several cephalometric factors related to the mandible were associated with stability. The horizontal distance between the maxillary and mandibular molars in centric relation was the best predictor of early class III treatment relapse.

中文翻译：

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早期Ⅲ类治疗与稳定性相关的预处理因素分析

本研究的目的是确定与早期 III 类治疗稳定性相关的治疗前因素，因为大多数正畸医生在开始治疗时都有不确定的假设和/或预测。受试者包括 75 名具有 III 级骨骼关系（ANB < 2° 和覆盖 < 0 mm）的患者，他们连续接受快速上颌扩张和面罩治疗，并随访至第二阶段治疗。根据患者在随访中是否出现复发，将患者分为两组。稳定组保持其正覆盖 (n = 55)，而不稳定组则以零或负覆盖 (n = 20) 复发。研究了两个一般因素、三个牙科因素和 13 个头影测量预处理因素，以确定哪些因素与稳定性相关。性别，治疗前年龄和前后功能转移被假设为相关因素，与早期 III 类治疗的稳定性无关。在正中关系的上颌和下颌磨牙之间的水平距离上检测到两组之间存在显着差异。头颅测量变量，如下颌长度 (Ar-Me)、Wits 评估、SN 到支平面角 (SN-Rm)、角角、下颌切牙平面角 (IMPA) 和法兰克福平面到下颌切牙角 (FMIA) 显示组之间的显着差异。通过逻辑回归分析，水平距离是影响最大的因素。假设（与性别、年龄、功能转变有关）被拒绝。与下颌骨相关的几个头影测量因素与稳定性有关。