Tanaka O M, Araújo E A, Oliver D R, Behrents R G
Graduate Dentistry Program in Orthodontics, School of Health and Biosciences, Pontifícia Universidade Católica do Paraná, Curitiba, Brazil.
Orthodontics, Center for Advanced Dental Education, Saint Louis University, St Louis, MO, USA.
Orthod Craniofac Res. 2015 Nov;18(4):242-50. doi: 10.1111/ocr.12102. Epub 2015 Sep 2.
To analyze the stress distribution on the PDL of the maxillary first molar in a mixed dentition Class III malocclusion, using a Hyrax-type appliance and maxillary protraction.
A Class III malocclusion in the mixed dentition was reconstructed based on CBCT images.
The 3D FEM comprised the maxilla, alveolar bone, right first permanent molar teeth, and PDL and consisted of 1 133 497 nodes and 573 726 elements. Maxillary protraction force was applied to a hook positioned close to the deciduous canines with 600 g and at 15°, 30°, and 45° downward angles to the maxillary occlusal plane.
Analysis was carried out from the top and buccal view of the sagittal plane. The magnitude of the stresses at 15°, 30°, and 45° of protraction angulation resulted in the highest stress magnitude being in the region between the distobuccal and palatal roots, as well as on the distal surface of the mesial root. The vector direction in this area showed traction and mesial movement. With 30° and 45° protraction angulations, the stress was located only between the distobuccal and palatal roots, and the vector direction was more extrusive at 15°.
The suggested orthodontic movement is in the mesial direction with a small amount of extrusion with 15° angulation and greater extrusion with 30° and 45°.
使用Hyrax型矫治器和上颌前牵引，分析混合牙列III类错牙合畸形上颌第一磨牙牙周膜的应力分布。
基于CBCT图像重建混合牙列III类错牙合畸形。
三维有限元模型包括上颌骨、牙槽骨、右侧第一恒磨牙以及牙周膜，由1133497个节点和573726个单元组成。上颌前牵引力以600g的力施加于靠近乳尖牙的挂钩上，与上颌牙合平面呈15°、30°和45°的向下角度。
从矢状面的顶部和颊侧视图进行分析。牵引角度为15°、30°和45°时，应力大小在远中颊根和腭根之间的区域以及近中根的远中表面最高。该区域的矢量方向显示为牵引和近中移动。牵引角度为30°和45°时，应力仅位于远中颊根和腭根之间，15°时矢量方向更向外。
建议的正畸移动方向为近中方向，15°角度时有少量的牙合向移动，30°和45°时有更大的牙合向移动。
