Torque Control of Upper Incisor in Intrusive Loads and Comparison of the Lingual and Labial Bracket Systems: A Finite Element Analysis

Objective: The aim of present study was to investigate the difference of torque control during intrusion force in incisors with normal, under and over-torque in lingual and labial orthodontic systems through finite element analysis. Material and Methods: 3D models of an upper right central incisor with different torques were designed in Solid Works 2006.The models were transferred to the ANSYS Workbench Version 12.1.An intrusive force of 0.15 N was applied to the bracket slot in different models and the displacements along a path of nodes in the central incisor was assessed. Results: Intrusive force in under-torqued model in Labial system induced labial crown movement but in Lingual system caused lingual movement in the apical and incisal parts. The same forces in normal-torqued central incisor led to a palatal movement in apical and labial displacement of incisal edge in Lingual system and a palatal displacement in apical area and a labial movement in the incisal edge in Labial system. In overtorqued upper central incisor, the labial crown displacement in Labial system is more than Lingual system. Conclusions: Application of the same forces in labial and lingual system in upper central incisor with different inclinations induce different responses. Torque control in Labial orthodontic system was more difficult than Lingual system in each situation.