Allahyar Geramy - Professor Dental Research Center and Orthodontics Department Tehran University of Medical Sciecnes
Tahoora Etezadi - Post graduate Student Orthodontics Department, Tehran University of Medical Sciences

Desirable tooth movements need optimal force systems. Loops are employed to move teeth properly. L-loop is used frequently due to its ease of fabrication. The aim of this study is to assess the expected forces and moments when a definite length of wire is bent to form L-loop. In other words, the effect of loop height and width on the produced force and moment is evaluated by the finite element method (FEM). Materials and methods: Six ۳D finite element models were designed of an L-loop without pre-activation bends keeping the total lengths of wire equal to ۲۴.۳۴+/- ۰.۵ mm. The cross section of wire was ۰.۰۱۶”× ۰.۰۲۲”. The force produced by activation in a ۰.۱ millimeter increment was recorded. Results: In model L۱, the findings start with ۰.۰۸۶ N in ۰.۱ mm of activation and increased to ۰.۸۸ N in ۱mm of loop opening. The pattern of findings was almost the same for other loop designs (L۲ through L۶) with an increase in findings. M/F ratios were almost constant in a loop design along its activation starting with ۳ in L۱ and reaching about ۱.۹-۲ in L۶. Conclusions: Moment to force ratios were almost constant in a loop design along its activation. increasing width and decreasing height with almost the same length of loop wire can increase force and therefor reduce M/F ratio.

Orthodontic loops, L-loop, Force, Moment, finite element method