Department of Orthodontics, Faculty of Dentistry, Istanbul University, Istanbul, Turkey.
Am J Orthod Dentofacial Orthop. 2011 Nov;140(5):e233-41. doi: 10.1016/j.ajodo.2011.06.019.
The goal of this study was to evaluate the effects of 3 maxillary posterior intrusion mechanics with mini-implant anchorage by using the finite element method.
Finite element models were generated by assembling the images obtained by computed tomography and a laser surface scanner. For each posterior dental segment, a 300-g force was applied and distributed to the mini-implants in proportion to their calculated root surface areas.
The most balanced intrusion and the most uniform stress distribution were obtained by concurrent force applications from the vestibular and palatinal sides. In the models with transpalatal arches and buccal force application, vestibular tipping movement and overall stress values were prominent. In all models, increased stress values were identified at the apical region of the first premolar roots and at the apical region of the first molar mesial root.
The results of this study suggest that the apical region of the first premolar roots and the apical region of the first molar mesial root should be considered to be prone to resorption during posterior intrusion treatment. Posterior intrusion systems with force application from counterbalancing sites lead to a more uniform stress distribution and balanced intrusion than the mechanics with a transpalatal arch. For a balanced intrusion, root surface areas should be considered when determining the appropriate forces.
本研究旨在通过有限元法评估 3 种使用微型种植体支抗的上颌后牙整体内收力学的效果。
通过将计算机断层扫描和激光扫描获得的图像组合，生成有限元模型。对每个后牙段，施加 300g 的力，并按照其计算的根表面积比例分配到微型种植体上。
通过从颊侧和腭侧同时施加力，可获得最平衡的内收和最均匀的应力分布。在使用腭杆和颊侧施力的模型中，出现了明显的颊倾运动和整体的较大的应力值。在所有模型中，第一前磨牙根尖区和第一磨牙近中颊根根尖区的应力值均增加。
本研究结果表明，在进行后牙整体内收治疗时，应考虑第一前磨牙根尖区和第一磨牙近中颊根根尖区容易发生吸收。与使用腭杆的力学相比，从平衡部位施力的后牙内收系统可导致更均匀的应力分布和更平衡的内收。为了达到平衡的内收，在确定适当的力时应考虑根表面积。
