Geramy Allahyar, Mahmoudi Reza, Geranmayeh Ali Reza, Borujeni Elahe Soltanmohamadi, Farhadifard Homa, Darvishpour Hojat
Department of Orthodontics, Tehran University of Medical Sciences, Tehran, Iran.
Department of Metallurgy and Materials Engineering, Faculty of Engineering, University of Tehran, Tehran, Iran.
Int Orthod. 2018 Mar;16(1):42-59. doi: 10.1016/j.ortho.2018.01.011. Epub 2018 Feb 22.
Several methods have been used to analyse different characteristics of orthodontic loops, which are generally divided into two categories: Experimental methods, Analytical and numerical methods such as finite element methods (FEM). The main goal of this study was to compare the results of FEM and experimental methods in determining mechanical characteristics (moment, force and M/F in various ranges of activation and different angular bends) of four common orthodontic loops to find the level of concordance between them.
Experimental method: 60 closing loops were prepared and divided into four groups. Universal testing machine was used for two reasons: tensile tests were performed to check the horizontal force component; compression tests were designed to check the vertical force component. To measure the moment at the two ends of the loops, they were activated by 0.1mm, 0.3mm, 0.7mm, 1mm, 1.25mm and 1.5mm. The vertical component of the force was calculated at the centre of the loops. Each group was divided to three subgroups, depending on the amount of applied angular bend: 0°, 20°, 40°. Finite element method (FEM): three-dimensional model loops were designed by special software. Then, strong meshing software meshed them. Loops were activated in the same range attempted in the experimental method. Then, force, moment and M/F were assessed.
It can be understood from the results of both methods that the values of force and moment increase when the activation range and angular bend increase, and M/F increases when the activation range decreases and angular bend increases. The highest concordance between the two methods was related to M/F, force and moment.
Experimental results and FEM predictions are in good agreement when determining the mechanical characteristics of the loops.
已采用多种方法分析正畸曲的不同特性，这些方法通常分为两类：实验方法、分析和数值方法，如有限元法（FEM）。本研究的主要目的是比较有限元法和实验方法在确定四种常见正畸曲的力学特性（在不同激活范围和不同角度弯曲下的力矩、力和M/F）时的结果，以找出它们之间的一致性水平。
实验方法：制备60个闭合曲并分为四组。使用万能试验机有两个原因：进行拉伸试验以检查水平力分量；设计压缩试验以检查垂直力分量。为测量曲两端的力矩，分别以0.1mm、0.3mm、0.7mm、1mm、1.25mm和1.5mm的幅度激活曲。在曲的中心计算力的垂直分量。根据施加的角度弯曲量，每组再分为三个亚组：0°、20°、40°。有限元法（FEM）：用专用软件设计三维模型曲。然后，用强大的网格划分软件对其进行网格划分。曲的激活幅度与实验方法相同。然后，评估力、力矩和M/F。
从两种方法的结果可以看出，当激活范围和角度弯曲增加时，力和力矩的值增加，当激活范围减小而角度弯曲增加时，M/F增加。两种方法之间的最高一致性与M/F、力和力矩有关。
在确定曲的力学特性时，实验结果与有限元法预测结果吻合良好。
