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.