Zhang Qiang, Zhao Zhi-he, Wang Jun, Zhao Mei-ying
Department of Orthodontics, The People's Hospital of Shenzhen, Guangdong Province, Shenzhen 518001, China.
Sichuan Da Xue Xue Bao Yi Xue Ban. 2004 Sep;35(5):680-2.
The aim of this study was to assess the effects of varying retractive force directions on the displacement of and stress distributions in palate.
A three-dimensional finite element model of the nasomaxillary complex was created, consisting of 1638 isoparametric elements and 1827 nodes. An extraoral retractive force of 9.8N was applied to the upper canines in 3 different directions, i.e. parallel, 30 degrees upwards and downwards to the functional occlusal plane. Then we investigated the nature of stress distributions, the directions and amounts of displacement in palate by finite element analysis.
In the midpalatal suture and transpalatal suture, all displacement directed to bone suture and increased gradually when the retractive force direction ranged from +30 degrees to -30 degrees. In the midmost part of palate, correlation between stress distributions and retractive force directions was not significant. Relatively compressive stresses were induced in the front and middle of the midpalatal suture, whereas nearly no stress was induced in the back. In the lateral part of palate, compressive stresses were nearly equal to tensile stresses in the front, while tensile stresses were induced in the middle and back. Meanwhile, there was no significant correlation between stress distributions and force directions.
This study showed that the directions of retractive force had obvious effects on displacement but but little effect on stress distributions.
本研究旨在评估不同牵引力量方向对上颌骨位移及腭部应力分布的影响。
建立一个由1638个等参单元和1827个节点组成的鼻上颌复合体三维有限元模型。在3个不同方向（即与功能咬合平面平行、向上30度和向下30度）对上前牙施加9.8N的口外牵引力。然后通过有限元分析研究腭部应力分布的性质、位移方向和大小。
在腭中缝和跨腭缝处，当牵引力方向从+30度到-30度变化时，所有位移均指向骨缝并逐渐增加。在腭部最中间部分，应力分布与牵引力方向之间的相关性不显著。腭中缝前部和中部产生相对压应力，而后部几乎不产生应力。在腭部外侧，前部压应力几乎等于拉应力，而中部和后部产生拉应力。同时，应力分布与力的方向之间无显著相关性。
本研究表明，牵引力方向对位移有明显影响，但对应力分布影响较小。
