Wang Russell, Liu Yunfeng, Wang Joanne Helen, Baur Dale Allen
Department of Comprehensive Care, Case Western Reserve University, School of Dental Medicine, 10900 Euclid Ave., Cleveland, OH 44106-4905, USA.
Department of Mechanical Engineering, Key Laboratory of E&M, Zhejiang University of Technology, 18 Tsao Wong Road, Hangzhou, Zhejiang 310014, China.
J Plast Reconstr Aesthet Surg. 2017 Mar;70(3):360-369. doi: 10.1016/j.bjps.2016.10.026. Epub 2016 Nov 11.
The aim of this study was to simulate stress and strain distribution numerically on a normal mandible under physiological occlusal loadings. The results were compared with those of mandibles that had an angle fracture stabilized with different fixation designs under the same loadings. The amount of displacement at two interfragmentary gaps was also studied.
A three-dimensional (3D) virtual mandible was reconstructed with an angle fracture that had a fracture gap of either 0.1 or 1 mm. Three types of plate fixation designs were used: Type I, a miniplate was placed across the fracture line following the Champy technique; Type II, two miniplates were used; and Type III, a reconstruction plate was used on the inferior border of the mandible. Loads of 100 and 500 N were applied to the models. The maximum von Mises stress, strain, and displacement were computed using finite element analysis. The results from the control and experimental groups were analyzed and compared.
The results demonstrated that high stresses and strains were distributed to the condylar and angular areas regardless of the loading position. The ratio of the plate/bone average stress ranged from 215% (Type II design) to 848% (Type I design) irrespective of the interfragmentary gap size. With a 1-mm fracture gap, the ratio of the plate/bone stress ranged from 204% (Type II design) to 1130% (Type I design). All strains were well below critical bone strain thresholds. Displacement on the cross-sectional mapping at fracture interface indicated that uneven movement occurred in x, y, and z directions.
Interfragmentary gaps between 0.1 and 1 mm did not have a substantial effect on the average stress distribution to the fractured bony segments; however, they had a greater effect on the stress distribution to the plates and screws. Type II fixation was the best mechanical design under bite loads. Type I design was the least stable system and had the highest stress distribution and the largest displacement at the fracture site.
本研究的目的是在生理咬合负荷下对正常下颌骨的应力和应变分布进行数值模拟。将结果与在相同负荷下采用不同固定设计稳定角部骨折的下颌骨的结果进行比较。还研究了两个骨折间隙处的位移量。
构建一个带有角部骨折的三维（3D）虚拟下颌骨，骨折间隙为0.1或1毫米。使用三种类型的钢板固定设计：I型，按照尚皮技术在骨折线上放置一块微型钢板；II型，使用两块微型钢板；III型，在下颌骨下缘使用一块重建钢板。对模型施加100和500牛的负荷。使用有限元分析计算最大冯·米塞斯应力、应变和位移。对对照组和实验组的结果进行分析和比较。
结果表明，无论负荷位置如何，高应力和应变均分布于髁突和角部区域。无论骨折间隙大小如何，钢板/骨平均应力之比在215%（II型设计）至848%（I型设计）之间。骨折间隙为1毫米时，钢板/骨应力之比在204%（II型设计）至1130%（I型设计）之间。所有应变均远低于临界骨应变阈值。骨折界面处横截面映射的位移表明，在x、y和z方向均发生不均匀移动。
0.1至1毫米的骨折间隙对骨折骨段的平均应力分布影响不大；然而，它们对钢板和螺钉的应力分布影响较大。II型固定是咬合负荷下最佳的力学设计。I型设计是最不稳定的系统，在骨折部位应力分布最高且位移最大。
