The Role of Loop Height and Design on its Force Characteristics in Alignment of Teeth: A Finite Element Analysis

The aim of this study was to assess the effects of different orthodontic vertical loop height and design on its force characteristics at different amount of loop activation by means of finite element method (FEM) analysis.
Four 3D FEM models were designed of double vertical open loop (DVOL) and double vertical helical open loop (DVHOL) each of them in two heights of 6 mm and 7 mm. The loops were modeled in SolidWorks 2006 and then transferred to ANSYS Workbench. The loops were activated in buccolingual direction for 0.1, 0.3, 0.5, 0.7 and 1 mm simulating an activated multi-loop arch wire to align a posterior tooth which is erupted with buccal or lingual inclination. The force delivered at each amount of activation for the four loop designs were measured and compared.
The results of this study showed that the minimum amount of force was delivered by double vertical helical open loop with the height of 7 mm at the activation of 0.1 mm which was about 1.06E-01 N. The maximum amount of force was 2.2199 N which was delivered by double vertical open loop with height of 6mm at 1 mm activation. At each amount of activation the value of exerted force followed this order: DVOL 6 mm > DVOL 7 mm > DVHOL 6 mm > DVHOL 7 mm.
According to this FEM study, considering its limitations, adding a helix in a double vertical open loop as well as increasing the height of loop can reduce the value of delivered force.