Department of Orthodontics, National Engineering Laboratory for Digital and Material Technology of Stomatology, Beijing Key Laboratory of Digital Stomatology, Peking University School and Hospital of Stomatology, Beijing, China.
Department of Orthodontics, National Engineering Laboratory for Digital and Material Technology of Stomatology, Beijing Key Laboratory of Digital Stomatology, Peking University School and Hospital of Stomatology, Beijing, China.
Am J Orthod Dentofacial Orthop. 2024 Sep;166(3):215-226. doi: 10.1016/j.ajodo.2024.04.012. Epub 2024 Jun 19.
This study evaluated the labial and lingual cortical bone remodeling characteristics of mandibular central incisors after retraction, which remain controversial among orthodontists.
Cortical bone remodeling and central incisor movement of 33 patients (aged 23.64 ± 4.30 years) who underwent mandibular first premolar extraction and incisor retraction at the crestal (S1), midroot (S2), and apical (S3) levels were analyzed using superimposed cone-beam computed tomography images on the basis of voxel-based registration of the mandibular stable region. Multivariate linear regression was used to explore the relationships between labial bone remodeling/tooth movement (BT) ratios and factors such as the ANB angle, mandibular plane angle (Mp-SN), and incisor movement patterns. The patients were divided into 4 groups according to the lingual cortical bone remodeling condition and the relationship between posttreatment incisor roots and the original lingual cortical bone border. At the 3 levels (S1, S2, and S3), the classifications of cortical bone remodeling of the mandibular incisors were calculated; t tests were used to compare the amount of labial and lingual bone remodeling, BT ratios, and lingual bone remodeling/root over the original border (BRo) ratios.
The mean labial BT ratios at all 3 levels were close to 1. Multivariate linear regression indicated that the tooth movement pattern negatively correlated with the BT ratio at the S2 and S3 levels (P <0.05). Lingual bone apposition occurs when the root penetrates the original lingual cortical bone border in most patients. BRo ratios can more accurately reflect the inherent remodeling ability of the lingual cortical bone than BT ratios. The mean lingual BRo ratios were (1) S1 level: mandibular left central incisor (T31), 0.87 ± 0.25 and mandibular right incisor (T41), 0.86 ± 0.25; (2) S2 level: T31, 0.81 ± 0.12 and T41, 0.80 ± 0.22; and (3) S3 level: T31, 0.76 ± 0.20 and T41, 0.83 ± 0.26. There was no significant difference between labial BT ratios and lingual BRo ratios at the S2 and S3 levels.
The amount of labial cortical bone resorption caused by mandibular incisor retraction showed varied relationships with the amount of tooth movement. Bodily retraction may decrease the labial BT ratios at the S2 and S3 levels. Active lingual cortical bone apposition occurred when the roots penetrated the original lingual border and exhibited strong remodeling ability.
本研究评估了下颌中切牙在牵引后的唇侧和舌侧皮质骨改建特征，这在正畸医生中仍存在争议。
对 33 名患者（年龄 23.64±4.30 岁）进行了分析，这些患者接受了下颌第一前磨牙拔除和中切牙牵引，牵引位置在牙槽嵴顶（S1）、根中部（S2）和根尖（S3）。使用基于下颌稳定区域的体素配准的叠加锥形束 CT 图像分析皮质骨改建和中切牙的移动。采用多元线性回归分析唇侧骨改建/牙齿移动（BT）比值与 ANB 角、下颌平面角（Mp-SN）和牙齿移动模式等因素之间的关系。根据舌侧皮质骨改建情况和治疗后切牙牙根与原舌侧皮质骨边界的关系，将患者分为 4 组。在 3 个水平（S1、S2 和 S3）计算下颌切牙皮质骨改建的分类；采用 t 检验比较唇侧和舌侧骨改建量、BT 比值和舌侧骨改建/牙根越过原边界（BRo）比值。
所有 3 个水平的平均唇侧 BT 比值接近 1。多元线性回归分析表明，牙齿移动模式与 S2 和 S3 水平的 BT 比值呈负相关（P<0.05）。在大多数患者中，当牙根穿透原舌侧皮质骨边界时，舌侧会发生骨沉积。BRo 比值比 BT 比值更能准确反映舌侧皮质骨的固有改建能力。平均舌侧 BRo 比值为：（1）S1 水平：下颌左侧中切牙（T31）为 0.87±0.25，下颌右侧中切牙（T41）为 0.86±0.25；（2）S2 水平：T31 为 0.81±0.12，T41 为 0.80±0.22；（3）S3 水平：T31 为 0.76±0.20，T41 为 0.83±0.26。S2 和 S3 水平的唇侧 BT 比值与舌侧 BRo 比值无显著差异。
下颌中切牙牵引引起的唇侧皮质骨吸收量与牙齿移动量呈不同关系。整体内收可能会降低 S2 和 S3 水平的唇侧 BT 比值。当牙根穿透原舌侧边界时，会发生活跃的舌侧皮质骨沉积，表现出较强的改建能力。
