Computer Methods and Programs in Biomedicine 197 (2020) 105748 Contents lists available at ScienceDirect Computer Methods and Programs in Biomedicine journal homepage: www.elsevier.com/locate/cmpb Finite element analysis of torque induced orthodontic bracket slot deformation in various bracket-archwire contact assembly Pandurangan Harikrishnan a,∗ , Varadaraju Magesh b , Akhil Minu Ajayan c , Devadhas Kingsly JebaSingh b a Craniofacial Orthodontist, Division of Orthodontics, Teeth “N” Jaws Center, Lake Areaa 1st Cross Street, Nungambakkam, Chennai 600034, Tamil Nadu, India b Department of mechanical engineering, SRM Institute of Science and Technology, Kattankulathur, Chengalpattu 603203, Tamil Nadu, India c Department of mechanical Engineering, SRM Institute of Science and Technology, Chengalpattu 603203, Tamil Nadu, India a r t i c l e i n f o Article history: Received 21 March 2020 Accepted 4 September 2020 Available online xxx Keywords: Slot deformation FEA Torque Stainless steel 0.018 inch slot 0.022 inch slot a b s t r a c t Background and Objectives: Orthodontic fixed appliance therapy involves alignment of teeth through the bracket and archwires. The archwire twist (torque) imparts significant forces inside the bracket slot in refining the teeth position at the end of treatment. The objective of this in- silico study was to evaluate the torque induced bracket slot deformation in the commonly used 0.018 inch (") and 0.022" conventional Stainless Steel (SS) brackets with clinically relevant archwires during various angles of twist. Methods: SS maxillary central incisor brackets of 0.018" width × 0.022" depth (0.457 mm × 0.558 mm) and 0.022" width × 0.028" depth (0.558 mm × 0.711 mm) were used. The SS archwires of 0.016" width × 0.022" depth (0.406 mm × 0.558 mm), 0.017" width × 0.025" depth (0.431 mm × 0.635 mm), 0.019" width × 0.025" depth (0.482 mm × 0.635 mm) and 0.021" width × 0.025" depth (0.533 mm × 0.635 mm) were engaged in the respective bracket slots. The assembled bracket-archwire Finite Element (FE) models were constructed. The archwire torque, the top, middle and bottom slot deforma- tions (TSD, MSD, BSD) were obtained for the bracket-archwire combinations for various angles of arch- wire twist using FE Analysis (FEA). Results: The torque, TSD, MSD and BSD for 30 o twist of 0.016" × 0.022" archwire in 0.018" slot were 28.13 Nmm, 35.71 μm, 21.51 μm and 15.67 μm respectively, and for 0.017" × 0.025" archwire were 50.18 Nmm, 54.52 μm, 32.47 μm and 19.11 μm respectively. Similarly for 0.019" × 0.025" archwire in 0.022" slot and 0.021" × 0.025" archwire in 0.022" slot they were 38.82 Nmm, 50.78 μm, 31.47 μm and 16.82 μm, and 60.22 Nmm, 65.22 μm, 36.44 μm and 22.68 μm respectively. Conclusions: The slot deformation was present in both 0.018" and 0.022" brackets which increased as the angle of twist increased. The TSD were higher than the MSD and BSD in all the bracket-archwire combinations. We conclude that there is only elastic deformation of bracket slots upto 30 o angle of twist and clinicians could maintain within this torque limits to avoid plastic deformation leading to improper teeth position. © 2020 Elsevier B.V. All rights reserved. 1. Introduction Orthodontic bracket is an important component of orthodontic fixed appliance therapy which transfers forces to the teeth from the archwire engaged in the bracket slot in aligning the teeth. Torque (couple) in orthodontics is created by the rotation of a rect- ∗ Corresponding author. E-mail addresses: teethnjaws@rediffmail.com (P. Harikrishnan), mageshv@srmist.edu.in (V. Magesh), akhilminu_ajayan@srmuniv.edu.in (A.M. Ajayan), kingslyd@srmist.edu.in (D.K. JebaSingh). angular archwire (along its long axis) inside the bracket slot which helps to move the teeth crown or root to their desirable position to achieve proper alignment and occlusion. The archwires are sub- jected to different magnitudes of twist / torque in the final stages of orthodontic fixed appliance therapy. During torquing, the arch- wire edges contacts the slot walls of the bracket and exerts forces on the teeth. These forces could deform the slot wall which might reduce the torque applied for teeth movement and jeopardize the teeth position. The clinically effective torque depends on various factors like the archwire play, bracket-archwire combination, liga- tion methods etc. Flores et al. showed that the metal brackets were https://doi.org/10.1016/j.cmpb.2020.105748 0169-2607/© 2020 Elsevier B.V. All rights reserved.