Rothe Laura E, Bollen Anne-Marie, Little Robert M, Herring Susan W, Chaison Jeremy B, Chen Curtis S-K, Hollender Lars G
School of Dentistry, University of Washington, Seattle, Wash 98195, USA.
Am J Orthod Dentofacial Orthop. 2006 Oct;130(4):476-84. doi: 10.1016/j.ajodo.2005.03.023.
Dental relapse of the mandibular incisors after orthodontic treatment is a common problem, and few risk factors have been identified. The purpose of this case-control study was to evaluate whether the amount or the structure of mandibular bone affects the potential for postorthodontic mandibular incisor relapse.
The subject sample was selected from the postretention database at the University of Washington. Subjects were chosen based on the availability of lateral cephalograms and mandibular periapical radiographs taken approximately 10 years postretention (T3). The mandibular incisor irregularity index (II) was measured on the T3 casts. Two groups were identified: subjects with the II greater than 6 mm (relapse or case) and those with the II less than 3.5 mm (stable or control). Once the case/control status was determined, the II was measured on models taken at the initial orthodontic examination (T1) and at the end of treatment (T2). Sixty relapse and 263 stable subjects were identified. Mandibular cortical thickness measured on both panoramic and lateral cephalometric radiographs was used to assess the amount of mandibular bone, and fractal analysis was used to analyze the trabecular bone structure around the mandibular incisors on the periapical radiographs. Logistic regression analyses were used to determine the association between dental relapse and significant bone parameters. The models were adjusted for potentially confounding variables (initial II, sex, age, and postretention time).
The relapse subjects had a larger mean II at T1 and a longer postretention time than the stable subjects. The mean cephalometric mandibular cortical thickness was significantly smaller in the relapse group than in the stable group at T1, T2, and T3. There were no statistically significant differences in the trabecular structure of bone, as measured with fractal analyses, between the relapse and stable groups.
These results indicate that patients with thinner mandibular cortices are at increased risk for dental relapse.
正畸治疗后下颌切牙的牙齿复发是一个常见问题，且已确定的风险因素较少。本病例对照研究的目的是评估下颌骨的量或结构是否会影响正畸治疗后下颌切牙复发的可能性。
研究对象样本选自华盛顿大学的保持后数据库。根据大约保持后10年（T3）拍摄的头颅侧位片和下颌根尖片的可获得性选择研究对象。在T3模型上测量下颌切牙不整齐指数（II）。确定了两组：II大于6mm的研究对象（复发组或病例组）和II小于3.5mm的研究对象（稳定组或对照组）。一旦确定病例/对照状态，就在正畸初始检查（T1）和治疗结束时（T2）拍摄的模型上测量II。确定了60例复发研究对象和263例稳定研究对象。在全景片和头颅侧位片上测量的下颌皮质厚度用于评估下颌骨的量，并且使用分形分析来分析根尖片上下颌切牙周围的骨小梁结构。使用逻辑回归分析来确定牙齿复发与显著骨参数之间的关联。模型针对潜在的混杂变量（初始II、性别、年龄和保持后时间）进行了调整。
复发组研究对象在T1时的平均II更大，且保持后时间比稳定组更长。在T1、T2和T3时，复发组的平均头颅侧位下颌皮质厚度显著小于稳定组。复发组和稳定组之间，通过分形分析测量的骨小梁结构没有统计学上的显著差异。
这些结果表明，下颌皮质较薄的患者牙齿复发风险增加。
