title: Finite element analysis of mandibular molar protraction mechanics using miniscrews.
abstract: OBJECTIVE
  The aim of this study was to determine the most desirable force system to achieve molar protraction from an interdental miniscrew minimizing side-effects. Several iterations of force delivery were simulated through variations in the height of a miniscrew, length of a molar extension arm, and incorporation of a lingual force.
  
  
  METHODS
  A three-dimensional mesh model of the right posterior segment of the mandible was developed from cone beam computed tomography data from a patient missing a first molar. Protraction appliances were constructed using computer-aided design software and integrated with finite element software. After mesh generation, a total of 80 loading conditions were simulated by altering the extension arm length (2-10mm), miniscrew height (0-8mm), and magnitude of protraction force from the lingual side (0-1.5 N). A constant labial force of 1 N was used in all models.
  
  
  RESULTS
  As the length of the extension arm increased, mesial tipping decreased, rotation decreased, and buccolingual inclination remained the same without lingual traction force. Lingual traction reduced rotation but increased tipping. Similar trends were observed in all situations despite of the height of the miniscrew.
  
  
  CONCLUSIONS
  The height of the miniscrew is not as critical in affecting tooth movement during mandibular second molar protraction as the length of the extension arm. The most ideal force system in the model appeared to be the longest extension arm (10mm) with the addition of a lingual force of half or equal magnitude of the labial force.
authors.affiliation: *Division of Orthodontics, Department of Craniofacial Sciences, University of Connecticut Health Center, Farmington, USA, **Division of Orthodontics, Department of Oral Biological Sciences, Niigata University, Japan, nihara@dent.niigata-u.ac.jp.
authors.forename: Jun
authors.initials: J
authors.lastname: Nihara
authors.affiliation: ***Department of Biomedical Engineering, University of Connecticut, School of Engineering, Storrs, USA.
authors.forename: Krystyna
authors.initials: K
authors.lastname: Gielo-Perczak
authors.affiliation: *Division of Orthodontics, Department of Craniofacial Sciences, University of Connecticut Health Center, Farmington, USA.
authors.forename: Lucas
authors.initials: L
authors.lastname: Cardinal
authors.affiliation: **Division of Orthodontics, Department of Oral Biological Sciences, Niigata University, Japan.
authors.forename: Isao
authors.initials: I
authors.lastname: Saito
authors.affiliation: ****Department of Craniofacial Sciences, Alumni Endowed Chair, School of Dental Medicine, University of Connecticut, Farmington, USA.
authors.forename: Ravindra
authors.initials: R
authors.lastname: Nanda
authors.affiliation: *Division of Orthodontics, Department of Craniofacial Sciences, University of Connecticut Health Center, Farmington, USA.
authors.forename: Flavio
authors.initials: F
authors.lastname: Uribe
mesh_terms: D001863:Bone Screws; D017076:Computer-Aided Design; D054893:Cone-Beam Computed Tomography; D020342:Finite Element Analysis; D006801:Humans; D008334:Mandible / Q000000981:diagnostic imaging / Q000502:physiology*; D008963:Molar / Q000502:physiology*; D013314:Stress, Mechanical; D014087:Tooth Movement Techniques / Q000295:instrumentation*