Fan Yi, Schneider Paul, Matthews Harold, Roberts Wilbur Eugene, Xu Tianmin, Wei Robert, Claes Peter, Clement John, Kilpatrick Nicky, Penington Anthony
Department of Orthodontics, Peking University School and Hospital of Stomatology, Beijing, 10081, China.
Melbourne Dental School, University of Melbourne, Melbourne, 3053, Australia.
BMC Oral Health. 2020 Apr 16;20(1):117. doi: 10.1186/s12903-020-01108-4.
A functional appliance is commonly used to optimize the development of the facial skeleton in the treatment of Class II malocclusion. Recent three-dimensional(3D) image-based analysis offers numerous advantages in quantitative measurement and visualization in orthodontics. The aim of this study was to localize in 3D the skeletal effect produced by the Herbst appliance on the mandible using the geometric morphometric technique.
Twenty patients treated with a Herbst appliance and subsequent fixed appliances were included. Cone-beam computed tomography (CBCT) images were taken before treatment (T1), 8 weeks after Herbst appliance removal (T2), and after subsequent fixed appliance treatment (T3). Spatially dense morphometric techniques were used to establish the corresponding points of the mandible. The mandibular morphological changes from T1-T2, T2-T3, and T1-T3 were calculated for each patient by superimposing two mandibular models at two time points with robust Procrustes superimposition. These changes were then compared to the morphological changes estimated from normative mandibular growth curves over the same period. The proportion of cases exceeding the growth expression for controls was compared to a normal population using a one tailed binomial test.
Approximately 1.5-2 mm greater condylar changes and 0.5 mm greater changes in the chin occurred from Tl to T2. This effect lasted until the completion of treatment (T1-T3), but there was no obvious skeletal effect during the orthodontic phase (T2-T3). Approximately 40-50% of the patient sample exceeded condylar growth by > 1.5 mm compared to untreated controls (p < .05). However, changes at the chin were not statistically significant.
The principal skeletal effect of Herbst appliance treatment was additional increase in condylar length for about half of the sample. This inconsistency may relate to the degree of mandibular growth suppression associated with a specific malocclusion.
功能性矫治器常用于在Ⅱ类错颌畸形治疗中优化面部骨骼的发育。近期基于三维（3D）图像的分析在正畸学的定量测量和可视化方面具有诸多优势。本研究的目的是使用几何形态测量技术在三维空间中定位Herbst矫治器对下颌骨产生的骨骼效应。
纳入20例接受Herbst矫治器及后续固定矫治器治疗的患者。在治疗前（T1）、Herbst矫治器拆除后8周（T2）以及后续固定矫治器治疗后（T3）拍摄锥形束计算机断层扫描（CBCT）图像。使用空间密集形态测量技术确定下颌骨的对应点。通过使用稳健的普氏叠加法在两个时间点叠加两个下颌模型，计算每位患者从T1-T2、T2-T3和T1-T3的下颌形态变化。然后将这些变化与同期从标准下颌生长曲线估计的形态变化进行比较。使用单尾二项式检验将超过对照组生长表现的病例比例与正常人群进行比较。
从T1到T2，髁突变化大约大1.5-2毫米，下巴变化大约大0.5毫米。这种效应持续到治疗结束（T1-T3），但在正畸阶段（T2-T3）没有明显的骨骼效应。与未治疗的对照组相比，约40-50%的患者样本髁突生长超过1.5毫米（p＜0.05）。然而，下巴的变化无统计学意义。
Herbst矫治器治疗的主要骨骼效应是约一半样本的髁突长度额外增加。这种不一致可能与特定错颌畸形相关的下颌生长抑制程度有关。
