title: Finite element analysis of miniscrew implants used for orthodontic anchorage.
abstract: BACKGROUND
  The miniscrew has been developed and effectively used as orthodontic anchorage, but current studies of its usage are insufficient to provide information about the underlying mechanical mechanisms. The aim of this study was to investigate the roles of bone quality, loading conditions, screw effects, and implanted depth on the biomechanics of an orthodontic miniscrew system by using finite element analysis.
  
  
  METHODS
  A 3-dimensional model with a bone block integrated with a miniscrew was constructed to simulate various cortex thicknesses, cancellous bone densities, force magnitudes and directions, screw diameters and lengths, and implanted depths of miniscrews.
  
  
  RESULTS
  Both stress and displacement increased with decreasing cortex thickness, whereas cancellous bone density played a minor role in the mechanical response. These 2 indexes were linearly proportional to the force magnitude and produced the highest values when the force was perpendicular to the long axis of the miniscrew. A wider screw provided superior mechanical advantages. The exposed length of the miniscrew was the real factor affecting mechanical performance.
  
  
  CONCLUSIONS
  The screw diameter was the dominant factor for minscrew mechanical responses. Both bone stress and screw displacement decreased with increasing screw diameter and cortex thickness, and decreasing exposed length of the screw, force magnitude, and oblique loading direction.
authors.affiliation: Institute of Oral Medicine, College of Medicine, National Cheng Kung University, Tainan, Taiwan, ROC.
authors.forename: Te-Chun
authors.initials: TC
authors.lastname: Liu
authors.forename: Chih-Han
authors.initials: CH
authors.lastname: Chang
authors.forename: Tung-Yiu
authors.initials: TY
authors.lastname: Wong
authors.forename: Jia-Kuang
authors.initials: JK
authors.lastname: Liu
mesh_terms: D001696:Biomechanical Phenomena; D015519:Bone Density / Q000502:physiology; D001863:Bone Screws; D001842:Bone and Bones / Q000033:anatomy & histology / Q000502:physiology; D003198:Computer Simulation; D015921:Dental Implants; D003764:Dental Materials / Q000737:chemistry; D055119:Elastic Modulus; D004868:Equipment Failure; D020342:Finite Element Analysis; D006801:Humans; D021621:Imaging, Three-Dimensional / Q000379:methods; D008954:Models, Biological; D052280:Orthodontic Anchorage Procedures / Q000295:instrumentation*; D016382:Orthodontic Appliance Design; D013314:Stress, Mechanical; D013499:Surface Properties; D014025:Titanium / Q000737:chemistry
chemical_list: D015921:Dental Implants; D003764:Dental Materials; D014025:Titanium