title: 3D FEM comparison of lingual and labial orthodontics in en masse retraction.
abstract: BACKGROUND
  The aim of this study was to compare displacements and stress after en masse retraction of mandibular dentition with lingual and labial orthodontics using three-dimensional (3D) finite element models (FEM).
  
  
  METHODS
  A 3D FEM of each lower tooth was constructed and located as appropriate to Roth's prescription. The 0.018-in. GAC Roth Ovation labial and Ormco 7th Generation lingual brackets were virtually bonded to the lower teeth and threaded with 0.018 × 0.025- and 0.016 × 0.022-in. SS labial (Tru-Arch form, small size) and lingual (mushroom) archwires. En masse retraction was simulated by applying 300 g of distal force from the canine to the second premolar on the 0.016 × 0.022-in. SS labial and lingual archwires. The type of finite element used in the analysis was an eight-noded brick element. The Algor program (Algor Inc., Pittsburgh, PA, USA) was used to calculate the strains and displacements at each nodal point.
  
  
  RESULTS
  Lingual tipping and extrusion of the anterior dentition occurred with both archwires. At the premolars and first molars, intrusion, lingual movements, and lingual tipping were seen with the labial archwire, while intrusion was accompanied by labial movements, mesial tipping, and buccal rotation with lingual mechanics.
  
  
  CONCLUSIONS
  Lingual vs. labial bracket placement influences the pattern of tooth movement, but the stress that occurs around the teeth can be accurately mapped using a 3D FEM model.
authors.affiliation: Department of Orthodontics, University of Ferrara, Via Montebello 31, Ferrara 44100, Italy. lulombardo@tiscali.it.
authors.forename: Luca
authors.initials: L
authors.lastname: Lombardo
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Scuzzo
authors.forename: Angela
authors.initials: A
authors.lastname: Arreghini
authors.forename: Ozge
authors.initials: O
authors.lastname: Gorgun
authors.forename: Yıldız Oztürk
authors.initials: YO
authors.lastname: Ortan
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Siciliani
mesh_terms: D001641:Bicuspid / Q000473:pathology; D001696:Biomechanical Phenomena; D003198:Computer Simulation; D003481:Cuspid / Q000473:pathology; D055119:Elastic Modulus; D020342:Finite Element Analysis; D006801:Humans; D021621:Imaging, Three-Dimensional / Q000379:methods*; D007180:Incisor / Q000473:pathology; D008334:Mandible / Q000473:pathology; D008954:Models, Biological; D008963:Molar / Q000473:pathology; D016910:Orthodontic Brackets; D019516:Orthodontic Space Closure / Q000295:instrumentation / Q000379:methods; D009969:Orthodontic Wires; D013314:Stress, Mechanical; D019228:Tooth Crown / Q000473:pathology; D014087:Tooth Movement Techniques / Q000295:instrumentation / Q000379:methods*; D014092:Tooth Root / Q000473:pathology; D014584:User-Computer Interface