Balakrishnan Rajkumar, Sengottuvel Nagalakshmi, Altaf Syed Khalid, Bhandari Pawan Kumar, Kumaragurubaran Preethi, Antony Marshal
Department of Orthodontics and Dentofacial Orthopedics, Vivekanandha Dental College for Women, Tiruchengode, IND.
Cureus. 2023 Mar 18;15(3):e36328. doi: 10.7759/cureus.36328. eCollection 2023 Mar.
Three-dimensional finite elemental analysis (FEA) is a contemporary research instrument for the numeric simulation of a real physical system's mechanical process. FEA can be used as a very effective tool to analyze and compare various aspects of rapid palatal expanders and to determine the stress distribution in maxillofacial bones and displacement and the biomechanical effects it has on the circummaxillary sutures. This study evaluates the effects of different modes of rapid palatal expansion on maxillary protraction as a treatment modality in skeletal Class III malocclusion by determining the stress and displacement along the circummaxillary sutures using the FEA.
Initially, a three-dimensional finite element simulation of the maxillofacial skeleton and sutures was obtained by Mimics software (Leuven, Belgium) from the cone-beam computed tomography (Dentsply Sirona, USA) images of a 30-year-old adult with normal occlusion. A geometrical preparation of the three expansion appliances, (A) hybrid MARPE (miniscrew-assisted rapid palatal expander)appliance (Fav anchor, India), (B) tooth-borne HYRAX (hygenic rapid expander) appliance (Welcare orthodontics, Kerela), and (C) bone-borne modified MARPE appliance (Biomaterials, Korea), was transferred to ANSYS WORKBENCH, 2020 R1 software (ANSYS, Inc., USA), and three finite element models with each appliance were prepared. A protraction force of 500g was applied to the occlusal plane that is directed 20 degrees inferiorly. The tensile stress, compressive stress, and the amount of displacement on the circummaxillary sutures were assessed and compared in all the three appliances. Young's modulus (kg/mm) and Poisson's ratio (V) were used to calculate the stress and displacement in sutures adjacent to the maxilla in different aspects.
On analyzing the stress distribution, the tensile stress was found to be maximum in the medial aspect of the frontomaxillary suture of the bone-borne modified MARPE appliance (C), and the minimum tensile stress was found in the lateral aspect of the sphenozygomatic suture in hybrid MARPE (A). Again, the compressive stress distribution was found to be maximum in the medial aspect of the frontomaxillary suture in all three simulations and the minimum compressive stress in the superior aspect of the internasal suture in hybrid MARPE (A) along with the frontonasal suture at its medial aspect for tooth-borne HYRAX (B) and bone-borne modified MARPE (C). Displacement of the maxilla in all the planes was observed to be the largest for the bone-borne modified MARPE (C) appliance. On the contrary, the minimum displacement was found in the tooth-borne HYRAX (B) appliance. Conclusion: The findings reveal that all three modes of rapid palatal expanders produced stress and displacement along the circummaxillary sutures on the application of protraction force with bone-borne modified MARPE being more effective in treating posterior crossbites thereby correcting the skeletal Class III malocclusions successfully.
三维有限元分析（FEA）是一种用于对实际物理系统的力学过程进行数值模拟的当代研究工具。有限元分析可作为一种非常有效的工具，用于分析和比较快速腭扩展器的各个方面，并确定颌面骨中的应力分布、位移以及其对上颌周围缝线的生物力学影响。本研究通过使用有限元分析确定上颌周围缝线处的应力和位移，评估不同模式的快速腭扩展对上颌前牵引作为骨性III类错牙合治疗方式的影响。
最初，通过Mimics软件（比利时鲁汶）从一名30岁正常咬合的成年人的锥形束计算机断层扫描（美国登士柏西诺德）图像中获得颌面骨骼和缝线的三维有限元模拟。将三种扩弓矫治器的几何模型，（A）混合式微型螺钉辅助快速腭扩展器（Fav锚定，印度），（B）牙支持式HYRAX快速扩弓器（Welcare正畸，喀拉拉邦），以及（C）骨支持式改良微型螺钉辅助快速腭扩展器（韩国生物材料），转移到ANSYS WORKBENCH 2020 R1软件（美国ANSYS公司），并制备了每种矫治器的三个有限元模型。在咬合平面上施加500g的前牵引力，方向向下20度。评估并比较了所有三种矫治器上颌周围缝线处的拉应力、压应力和位移量。使用杨氏模量（kg/mm）和泊松比（V）来计算不同方面上颌相邻缝线处的应力和位移。
在分析应力分布时，发现骨支持式改良微型螺钉辅助快速腭扩展器（C）的额上颌缝内侧拉应力最大，而混合式微型螺钉辅助快速腭扩展器（A）的蝶颧缝外侧拉应力最小。同样，在所有三个模拟中，额上颌缝内侧的压应力分布最大，混合式微型螺钉辅助快速腭扩展器（A）的鼻内缝上方以及牙支持式HYRAX（B）和骨支持式改良微型螺钉辅助快速腭扩展器（C）的鼻额缝内侧的压应力最小。观察到骨支持式改良微型螺钉辅助快速腭扩展器（C）矫治器在所有平面上的上颌位移最大。相反，牙支持式HYRAX（B）矫治器的位移最小。结论：研究结果表明，在施加前牵引力时，所有三种快速腭扩展器模式都会在上颌周围缝线处产生应力和位移，骨支持式改良微型螺钉辅助快速腭扩展器在治疗后牙反牙合从而成功矫正骨性III类错牙合方面更有效。
