title: Effect of increasing the vertical intrusive force to obtain torque control in lingual orthodontics: A three-dimensional finite element method study.
abstract: BACKGROUND
  Biomechanical differences between lingual and labial orthodontics (LiO and LaO).
  
  
  OBJECTIVE
  To investigate the effects of intrusive forces in lingual technique during retraction treatment mechanics.
  
  
  METHODS
  Intrusive forces act differently in both techniques because of the different location of force vectors in relation to the center of resistance. Increasing the vertical intrusive force is one of the methods routinely used to prevent the uncontrolled tipping and obtain bodily tooth movement in LaO. However, its effects in lingual technique need to be investigated to derive at an optimal treatment mechanics.
  
  
  METHODS
  Finite element method which has been successfully used to simulate tooth movement and optimize orthodontic mechanics effectively was used in this study. An accurate model of the upper central and lateral incisors with the surrounding structures was developed, and the "ANSYS" version 7.0 software was used for analysis.
  
  
  RESULTS
  Intrusive forces as high as 3.6N was required to obtain translation in LiO that too in an undesirable direction. Efforts to obtain torque control by increasing the intrusive force only would not be successful.
  
  
  CONCLUSIONS
  Forces that produce a translation in LaO tends to produce uncontrolled tipping in lingual technique. To obtain adequate torque control in lingual technique, a combination of the reduction in horizontal retraction forces, increased lingual root torque application, and increase in vertical intrusive forces is desirable.
authors.affiliation: Department of Orthodontics and Dentofacial Orthopaedics, Terna Dental College and Hospital, Mumbai, Maharashtra, India.
authors.forename: Robin N
authors.initials: RN
authors.lastname: Mathew
authors.affiliation: Department of Orthodontics and Dentofacial Orthopaedics, A. B. Shetty Memorial Institute of Dental Sciences, Mangalore, Karnataka, India.
authors.forename: Aneesh
authors.initials: A
authors.lastname: Katyal
authors.affiliation: Department of Orthodontics and Dentofacial Orthopaedics, A. B. Shetty Memorial Institute of Dental Sciences, Mangalore, Karnataka, India.
authors.forename: Ashutosh
authors.initials: A
authors.lastname: Shetty
authors.affiliation: Department of Orthodontics and Dentofacial Orthopaedics, A. B. Shetty Memorial Institute of Dental Sciences, Mangalore, Karnataka, India.
authors.forename: U S
authors.initials: US
authors.lastname: Krishna Nayak
mesh_terms: D001696:Biomechanical Phenomena; D003198:Computer Simulation; D003799:Dental Stress Analysis; D020342:Finite Element Analysis; D006801:Humans; D007180:Incisor / Q000503:physiopathology*; D009967:Orthodontic Appliances; D012984:Software; D013314:Stress, Mechanical; D014087:Tooth Movement Techniques / Q000379:methods*; D019415:Torque