Resident, Department of Orthodontics and Dentofacial Orthopaedics, Army College of Dental Sciences, Secunderabad, India.
Reader, Department of Orthodontics and Dentofacial Orthopaedics, Army College of Dental Sciences, Secunderabad, India.
J World Fed Orthod. 2021 Mar;10(1):29-34. doi: 10.1016/j.ejwf.2020.11.004. Epub 2020 Dec 23.
To evaluate, using the finite element method (FEM), von Mises stress patterns produced both in a mini-implant (MI) and the infra-zygomatic crest region (IZC) at different placement angles and force magnitudes.
FEM modeling of an infra-zygomatic crest MI, of dimensions 2 mm × 12 mm, was designed and placed in the IZC bone. The MI was inserted at 50°, 60°, 70°, 80°, and 90° angulations to the IZC surface. Simulated orthodontic forces of magnitudes 8, 9, 10, 11, and 12 oz were applied to the MI head. Von Mises stress and magnitude both in the MI and surrounding bone were measured.
Von Mises stress in the MI and bone was maximum at 90°. Least stresses were observed at 50° and 60° angulations. As force magnitude increased, von Mises stress increased linearly. Maximum stresses in the MI and bone were observed when loads were 12 oz and minimum stresses were observed at 8 oz.
To achieve optimum primary stability, angles of insertion between 50° and 60° are recommended in the IZC region. Highest von Mises stress values were detected in the MI, followed by cortical and cancellous bone. Also, loading force between 8 and 12 oz exerted stresses below the tolerable threshold of bone and MI. Hence, proper placement of MI in IZC using these findings might provide better biomechanical stability during retraction and may help in preserving the bone-implant interface.
使用有限元法（FEM）评估不同植入角度和力值下微型种植体（MI）和眶下嵴区（IZC）产生的冯·米塞斯（von Mises）应力模式。
设计并放置了尺寸为 2mm×12mm 的眶下嵴 MI，位于 IZC 骨中。MI 以 50°、60°、70°、80°和 90°的角度插入 IZC 表面。向 MI 头部施加 8、9、10、11 和 12 盎司的模拟正畸力。测量 MI 和周围骨中的 von Mises 应力和大小。
MI 和骨中的 von Mises 应力在 90°时最大。在 50°和 60°的角度下观察到最小的应力。随着力值的增加，von Mises 应力呈线性增加。当负荷为 12 盎司时，MI 和骨中的最大应力最大，当负荷为 8 盎司时，最小应力最大。
为了获得最佳的初始稳定性，建议在 IZC 区域插入角度在 50°和 60°之间。MI 中检测到的 von Mises 应力值最高，其次是皮质骨和松质骨。此外，8 至 12 盎司的加载力会在骨和 MI 的可耐受阈值以下产生应力。因此，根据这些发现，在 IZC 中正确放置 MI 可能会在收缩过程中提供更好的生物力学稳定性，并有助于保持骨-植入物界面。
