Santos Leonardo Soriano de Mello, Rossi Ana Cláudia, Freire Alexandre Rodrigues, Matoso Rodrigo Ivo, Caria Paulo Henrique Ferreira, Prado Felippe Bevilacqua
Professor, Brazilian Dental Association, Pará Section, Belém, PA, Brazil.
Professor, Department of Morphology, Anatomy Area, Piracicaba Dental School, State University of Campinas, Piracicaba, SP, Brazil.
J Oral Maxillofac Surg. 2015 Apr;73(4):683-91. doi: 10.1016/j.joms.2014.10.014. Epub 2014 Oct 22.
Maxillofacial trauma resulting from falls in elderly patients is a major social and health care concern. Most of these traumatic events involve mandibular fractures. The aim of this study was to analyze stress distributions from traumatic loads applied on the symphyseal, parasymphyseal, and mandibular body regions in the elderly edentulous mandible using finite-element analysis (FEA).
Computerized tomographic analysis of an edentulous macerated human mandible of a patient approximately 65 years old was performed. The bone structure was converted into a 3-dimensional stereolithographic model, which was used to construct the computer-aided design (CAD) geometry for FEA. The mechanical properties of cortical and cancellous bone were characterized as isotropic and elastic structures, respectively, in the CAD model. The condyles were constrained to prevent free movement in the x-, y-, and z-axes during simulation. This enabled the simulation to include the presence of masticatory muscles during trauma. Three different simulations were performed. Loads of 700 N were applied perpendicular to the surface of the cortical bone in the symphyseal, parasymphyseal, and mandibular body regions. The simulation results were evaluated according to equivalent von Mises stress distributions.
Traumatic load at the symphyseal region generated low stress levels in the mental region and high stress levels in the mandibular neck. Traumatic load at the parasymphyseal region concentrated the resulting stress close to the mental foramen. Traumatic load in the mandibular body generated extensive stress in the mandibular body, angle, and ramus.
FEA enabled precise mapping of the stress distribution in a human elderly edentulous mandible (neck and mandibular angle) in response to 3 different traumatic load conditions. This knowledge can help guide emergency responders as they evaluate patients after a traumatic event.
老年患者跌倒导致的颌面创伤是一个重大的社会和医疗保健问题。这些创伤事件大多涉及下颌骨骨折。本研究的目的是使用有限元分析（FEA）来分析施加于老年无牙下颌骨的正中联合、下颌骨旁正中及下颌体区域的创伤负荷所产生的应力分布。
对一名约65岁患者的无牙浸软人类下颌骨进行计算机断层扫描分析。将骨结构转换为三维立体光刻模型，该模型用于构建FEA的计算机辅助设计（CAD）几何形状。在CAD模型中，皮质骨和松质骨的力学性能分别被表征为各向同性和弹性结构。髁突受到约束，以防止在模拟过程中在x、y和z轴上自由移动。这使得模拟能够包括创伤过程中咀嚼肌的存在。进行了三种不同的模拟。在正中联合、下颌骨旁正中及下颌体区域，垂直于皮质骨表面施加700 N的负荷。根据等效冯·米塞斯应力分布对模拟结果进行评估。
正中联合区域的创伤负荷在颏部产生低应力水平，在下颌颈产生高应力水平。下颌骨旁正中区域的创伤负荷使产生的应力集中在颏孔附近。下颌体的创伤负荷在下颌体、下颌角和下颌支产生广泛应力。
FEA能够精确绘制人类老年无牙下颌骨（颈部和下颌角）在三种不同创伤负荷条件下的应力分布。这些知识有助于指导急救人员在创伤事件后对患者进行评估。
