Sucu Merve, Yilmaz Berza, Ramoğlu Sabri İlhan
Specialist in Orthodontics, Private practice, Istanbul, Turkey.
Department of Orthodontics, Faculty of Dentistry, Bezmialem Vakif University, Istanbul, Turkey.
Turk J Orthod. 2021 Mar 1;34(1):18-25. doi: 10.5152/TurkJOrthod.2021.20006. eCollection 2021.
This study aimed to describe the displacement of anatomical structures and the stress distributions caused by the Hyrax, fan-type, and double-hinged expansion screws via the 3-dimensional (3D) finite element method (FEM).
The 3D FEM was based on the computed tomography data of a 12-year-old patient with a constricted maxilla. The Hyrax model included 1,800,981 tetrahedral elements with 2,758,217 nodes. The fan-type model included 1,787,558 tetrahedral elements with 2,737,358 nodes. The double-hinged model included 1,777,080 tetrahedral elements with 2,722,771 nodes. The von Mises stress distributions after 0.2 mm of expansion and displacement patterns after 5 mm of expansion were evaluated.
The highest stress accumulation was observed in the sutura zygomatico maxillaris area with all 3 appliances. An increase in stress was noted at the pterygomaxillary fissure, the medial and lateral pterygoid process of the sphenoid bone, and the nasal areas. The wedge-shaped skeletal opening was observed with all 3 appliances. In the transverse plane, maximum posterior expansion was achieved with the Hyrax appliance, whereas the maximum anterior expansion was observed with the double-hinged appliance. The maxilla moved inferiorly and anteriorly with all the 3 appliances. The greatest inferior displacement of the maxilla was recorded with the Hyrax appliance, whereas anterior maxillary displacement was the greatest with the double-hinged appliance.
All the appliances showed similar stress distributions. The use of double-hinged screw caused a slight anterior displacement of point A. The fan-type and double-hinged appliances were shown to be more effective on anterior maxillary constriction, whereas the Hyrax appliance might be chosen for resolving maxillary posterior constriction.
本研究旨在通过三维（3D）有限元方法（FEM）描述Hyrax矫治器、扇形矫治器和双铰链扩弓螺钉所引起的解剖结构位移和应力分布。
3D有限元模型基于一名12岁上颌骨狭窄患者的计算机断层扫描数据构建。Hyrax模型包含1,800,981个四面体单元和2,758,217个节点。扇形模型包含1,787,558个四面体单元和2,737,358个节点。双铰链模型包含1,777,080个四面体单元和2,722,771个节点。评估了扩弓0.2 mm后的von Mises应力分布以及扩弓5 mm后的位移模式。
在所有三种矫治器中，颧上颌缝区域观察到最高应力积聚。在翼上颌裂、蝶骨翼突内外侧以及鼻腔区域应力增加。使用所有三种矫治器均观察到楔形骨骼开口。在横向平面上，Hyrax矫治器实现了最大的后部扩弓，而双铰链矫治器观察到最大的前部扩弓。使用所有三种矫治器时上颌均向下和向前移动。Hyrax矫治器记录到上颌最大向下位移，而双铰链矫治器上颌前部位移最大。
所有矫治器均显示出相似的应力分布。双铰链螺钉的使用导致A点轻微向前位移。扇形矫治器和双铰链矫治器对上颌前部缩窄更有效，而Hyrax矫治器可能更适合解决上颌后部缩窄问题。
