Evaluation of Effect of Variable Thickness of Customized Lingual Bracket Base on Torque of Anterior Teeth: A 3-dimensional Finite Element Study
Pravin Shetty, Shrinivas Ashtekar, Rahul Deshpande, Jagadeesh Gajapurada, Anil Biradar, Shital Kolekar
Department of Orthodontics and Dentofacial Orthopedics, Vasantdada Patil Dental College and Hospital, Sangli, India
Purposes: Lingual technique is distinct from labial technique due to changes in lingual tooth morphology and its anatomy and the biomechanical differences involved in the treatment. Our objectives were to evaluate the torque and stress in anterior teeth during en-masse retraction with different thickness of customized lingual bracket base with various torquing angles incorporated in an archwire.
Materials & Methods: Cone beam computed tomography was used to create a three dimensional geometric model of 14 maxillary teeth. This model was then meshed and analysed with finite element method. Customized lingual brackets of 0.018×0.025-inch slot with 2 mm and 4 mm bracket base thickness were bonded on two different FEM models. Enmasse retraction was simulated by applying 150 g of force from canine to molar on both sides using 0.017×0.025 TMA lingual straight wire.
Results: Lingual crown tipping of incisors, distal crown tipping of canine and extrusion of all the anterior teeth was noticed in all the cases. The tipping tendency was less for 2 mm bracket base thickness. The stress concentration was at cervical region of teeth and at crest of alveolar bone.
Conclusion: Increase in twist in an archwire tends to reduce the lingual crown tipping and achieve bodily movement. The bracket slot kept near to the lingual tooth surface with increase in twist in an archwire provides desired tooth movement.
Key words: Finite element analysis, Lingual orthodontics
Korean J Lingual Orthod 2016;5(1):1-9