Choy K, Pae E K, Park Y, Kim K H, Burstone C J
Department of Orthodontics, College of Dentistry, Yonsei University, Seoul, Korea.
Am J Orthod Dentofacial Orthop. 2000 Jan;117(1):98-105. doi: 10.1016/s0889-5406(00)70254-x.
To achieve predictable and physiologic orthodontic tooth movement, estimating the axis of rotation of a tooth and the level and location of maximum stress distributed in the periodontal ligament is essential. An extracted upper canine was scanned into a computer 2-dimensionally and divided into 80 nodes along the long axis of the tooth. A mathematical formula was derived, and stress was calculated on each node. The purpose of this study was to reveal the center of resistance, axis of rotation, and an ideal force magnitude associated with various periodontal conditions, such as potential root resorption, alveolar bone loss, and varying anatomic root shape by analyzing the stress distribution in the periodontal ligament. The study demonstrates that the location of center of resistance changes significantly with variation of shape and length of the root embedded in alveolar bone. In contrast, in response to alveolar bone loss, the relative location of the center of resistance to total root length remains constant. Analysis of the stress distribution pattern in our 2-dimensional model reveals that the relationship between location of force and axis of rotation is determined by s(2) (that is) a constant depends on shape and length of a root in alveolar bone. Tapered and short roots that result from alveolar bone loss or apical root resorption are prone to tipping. The optimal orthodontic force may vary depending on the maximum stress in the periodontal ligament.
为实现可预测的生理性正畸牙齿移动，估计牙齿的旋转轴以及牙周膜中最大应力分布的水平和位置至关重要。将一颗拔除的上颌尖牙进行二维扫描并输入计算机，沿牙齿长轴将其划分为80个节点。推导了一个数学公式，并计算每个节点上的应力。本研究的目的是通过分析牙周膜中的应力分布，揭示与各种牙周状况相关的阻力中心、旋转轴以及理想的力大小，这些牙周状况包括潜在的牙根吸收、牙槽骨丧失以及不同的解剖牙根形态。研究表明，阻力中心的位置会随着牙槽骨中牙根形状和长度的变化而显著改变。相比之下，对于牙槽骨丧失，阻力中心相对于牙根总长度的相对位置保持不变。对我们二维模型中应力分布模式的分析表明，力的位置与旋转轴之间的关系由s(2)决定（即）一个常数，该常数取决于牙槽骨中牙根的形状和长度。由牙槽骨丧失或根尖牙根吸收导致的锥形短根易于倾斜。最佳正畸力可能会因牙周膜中的最大应力而有所不同。
