1 Professor ,Dental Research Center and Orthodontics Department Tehran University of Medical Sciences

2 Post graduate Student Orthodontics Department, Tehran University of Medical Sciences

3 Epidemiologist, School of Dental Medicine, Tehran University of Medical Sciences

4 Research Advisor Dental Research Center, Tehran University of Medical Sciences



Introduction: An appropriate force system is a perquisite of desirable and predictable tooth movements during orthodontic treatment. Complete knowledge about the generated forces and moments by loops is essential to choose the best one for every situation.The aim of this study was to establish a mathematical equation to bring about a relationship between the L-loop height, width, activation and the produced force.
Materials and methods: Six 3D finite element models were designed for L-loop without preactivation bends. Loops were designed with different widths (w) and heights (h). The cross section of wire was 0.016”× 0.022”. The distal end of each model was activated 1 mm in 0.1 mm intervals. The force produced by activation in a 0.1 millimeter increment was recorded.
 Results: Force findings were different according to the loop parameters defined. The produced force varies from 0.106 to 0.228 N for a 0.1 millimeter of activation and increased from 1.07 to 2.27 N in 1.0 mm of activation.
Conclusion: The magnitude of force by L-loop can be estimated through adjustment of vertical part and activation as Increments of activation increased the delivered force while Increasing L-loop height decreased the generated force.