MacGinnis Matt, Chu Howard, Youssef George, Wu Kimberley W, Machado Andre Wilson, Moon Won
Prog Orthod. 2014 Aug 29;15(1):52. doi: 10.1186/s40510-014-0052-y.
Orthodontic palatal expansion appliances have been widely used with satisfactory and, most often, predictable clinical results. Recently, clinicians have successfully utilized micro-implants with palatal expander designs to work as anchors to the palate to achieve more efficient skeletal expansion and to decrease undesired dental effects. The purpose of the study was to use finite element method (FEM) to determine the stress distribution and displacement within the craniofacial complex when simulated conventional and micro-implant-assisted rapid palatal expansion (MARPE) expansion forces are applied to the maxilla. The simulated stress distribution produced within the palate and maxillary buttresses in addition to the displacement and rotation of the maxilla could then be analyzed to determine if micro-implants aid in skeletal expansion.
A three-dimensional (3D) mesh model of the cranium with associated maxillary sutures was developed using computed tomography (CT) images and Mimics modeling software. To compare transverse expansion stresses in rapid palatal expansion (RPE) and MARPE, expansion forces were distributed to differing points on the maxilla and evaluated with ANSYS simulation software.
The stresses distributed from forces applied to the maxillary teeth are distributed mainly along the trajectories of the three maxillary buttresses. In comparison, the MARPE showed tension and compression directed to the palate, while showing less rotation, and tipping of the maxillary complex. In addition, the conventional hyrax displayed a rotation of the maxilla around the teeth as opposed to the midpalatal suture of the MARPE. This data suggests that the MARPE causes the maxilla to bend laterally, while preventing unwanted rotation of the complex.
In conclusion, the MARPE may be beneficial for hyperdivergent patients, or those that have already experienced closure of the midpalatal suture, who require palatal expansion and would worsen from buccal tipping of the teeth or maxillary complex.
正畸腭扩展矫治器已被广泛应用，临床效果令人满意且大多可预测。最近，临床医生成功地将微型种植体与腭扩展器设计相结合，作为腭部的支抗，以实现更有效的骨骼扩展，并减少不必要的牙齿影响。本研究的目的是使用有限元方法（FEM）来确定当模拟的传统和微型种植体辅助快速腭扩展（MARPE）扩展力施加于上颌骨时，颅面部复合体内部的应力分布和位移情况。然后可以分析腭部和上颌支柱内产生的模拟应力分布以及上颌骨的位移和旋转情况，以确定微型种植体是否有助于骨骼扩展。
使用计算机断层扫描（CT）图像和Mimics建模软件建立了带有相关上颌缝的颅骨三维（3D）网格模型。为了比较快速腭扩展（RPE）和MARPE中的横向扩展应力，将扩展力分布在上颌骨的不同点上，并使用ANSYS模拟软件进行评估。
施加于上颌牙齿的力所产生的应力主要沿三个上颌支柱的轨迹分布。相比之下 MARPE 显示出指向腭部的拉力和压力，同时上颌复合体的旋转和倾斜较小。此外，传统的Hyrax矫治器显示上颌骨围绕牙齿旋转，而MARPE则围绕腭中缝旋转。这些数据表明，MARPE使上颌骨向外侧弯曲，同时防止复合体出现不必要的旋转。
总之，MARPE可能对高角型患者或那些已经经历腭中缝闭合、需要腭扩展且牙齿或上颌复合体颊向倾斜会使其病情恶化的患者有益。
