title: [Analysis of stress in periodontal ligament of the maxillary first molar on distal movement by nonlinear finite element method].
abstract: OBJECTIVE
  To analyze the stress distribution in periodontal ligament of maxillary first molar during distal movement with nonlinear finite element analysis, and to compare it with the result of linear finite element analysis, consequently to provide biomechanical evidence for clinical application.
  
  
  METHODS
  The 3-D finite element model including a maxillary first molar, periodontal ligament, alveolar bone, cancellous bone, cortical bone and a buccal tube was built up by using Mimics, Geomagic, ProE and Ansys Workbench. The material of periodontal ligament was set as nonlinear material and linear elastic material, respectively. Loads of different combinations were applied to simulate the clinical situation of distalizing the maxillary first molar.
  
  
  RESULTS
  There were channels of low stress in peak distribution of Von Mises equivalent stress and compressive stress of periodontal ligament in nonlinear finite element model. The peak of Von Mises equivalent stress was lower when it was satisfied that Mt/F minus Mr/F approximately equals 2. The peak of compressive stress was lower when it was satisfied that Mt/F was approximately equal to Mr/F. The relative stress of periodontal ligament was higher and violent in linear finite element model and there were no channels of low stress in peak distribution.
  
  
  CONCLUSIONS
  There are channels in which stress of periodontal ligament is lower. The condition of low stress should be satisfied by applied M/F during the course of distalizing the maxillary first molar.
authors.affiliation: Department of Stomatology, Lianyungang Chinese Medicine Hospital. Lianyungang 222004, Jiangsu Province; China.E-mail:dongjing011@sina.com.
authors.forename: Jing
authors.initials: J
authors.lastname: Dong
authors.forename: Zhe-chen
authors.initials: ZC
authors.lastname: Zhang
authors.forename: Guo-liang
authors.initials: GL
authors.lastname: Zhou
mesh_terms: D020342:Finite Element Analysis; D008437:Maxilla; D008963:Molar; D010513:Periodontal Ligament; D013314:Stress, Mechanical; D014087:Tooth Movement Techniques