A comparative study of forces in labial and lingual orthodontics using finite element method

Abstract

Background: Orthodontic treatment requires optimum force to achieve desirable tooth movement with minimal damage to the root, periodontal ligament (PDL), and alveolar bone. Hence, quantifying the magnitude and direction of force is very important for orthodontic treatment. Both labial orthodontics (LaO) and lingual orthodontics (LiO) are used for orthodontic tooth movements, which differ considerably in their biomechanics. Although these differences have been explained, force magnitude need to be evaluated. Aims: 1. To evaluate the differences in biomechanics of tipping movement in LaO and LiO using finite element method (FEM). 2. To quantify the reduced amount of force in LiO as compared LaO in tipping. Study Settings: It is a computational tool where three-dimensional (3D) FEM models of upper incisor is simulated in order to map and compare the stress produced by tipping movement performed with lingual and LaO. Materials and Methods: A 3D FEM model of the maxillary right central incisor was made from a geometric model. A 50 g tipping force was applied on a labial side. The principal stress patterns in the PDL for orthodontic tooth movement were recorded. When 50 g of tipping force was applied from a lingual side, higher stress values were observed. The forces on the lingual side were reduced to 45 g, 40 g, 35 g, 34 g, 33.5 g, and 33 g to check the maximum stress pattern on PDL. Results: A 50 g tipping force applied on the labial side will bring about 0.0252 N/mm 2 maximum principal stress. When the same amount of force applied on the lingual side will bring about 0.0375 N/mm 2 maximum principal stress. A 33.6-g force applied on the lingual side will bring about 0.0252 N/mm 2 maximum principal stress which is similar to 50 g of force applied on the lingual side. Conclusion: A palatally directed tipping force of 33.6 g in LiO was sufficient for orthodontic tooth movement. Tipping in LiO required 32.8% less force when compared to LaO.