title: [Three dimensional finite element analysis of the influence of stress on occlusal surface of the mandibular first molar].
abstract: OBJECTIVE
  Use of three-dimensional finite element to analyze stress distribution and transient displacement of mandibular first molar both at the occlusal surface level, to investigate the biomechanical basis of vertical root fracture occurring in the mesial root.
  
  
  METHODS
  Mimics finite element software was used to build the horizontal and tilt abrasion of the mandibular first permanent molar. Each status was then divided into 4 kinds of wearing degree and 8 models were then established including sliced 1, sliced 2, sliced 3, sliced 4 and miter 5°,miter10°,miter15°,miter20° respectively. 200 N of bite force was loaded on the occlusal surface using MSC. Marc nonlinear finite element analysis software was used to investigate the distribution of stress and transient displacement.
  
  
  RESULTS
  When distal tipping angle of the abrasion plane of mandibular first molar increased from 5° to 15°, the angle between instant displacement contours and tooth long axis become smaller, the mesial root suffered from the biggest stress concentration and thus the possibility of longitudinal root fracture increased.
  
  
  CONCLUSIONS
  When the abrasion plane of mandibular first molar tilted distally, the possibility of the mesial root longitudinal fracture increased.
authors.affiliation: Department of Stomatology, Weifang People's Hospital. Weifang 261041, Shandong Province, China. E-mail:saiwaideguoning@163.com.
authors.forename: Guo-ning
authors.initials: GN
authors.lastname: Gao
authors.affiliation: Department of Stomatology, Weifang People's Hospital. Weifang 261041, Shandong Province, China.
authors.forename: Guo-you
authors.initials: GY
authors.lastname: Wang
authors.affiliation: Department of Stomatology, Weifang People's Hospital. Weifang 261041, Shandong Province, China.
authors.forename: Ji-wu
authors.initials: JW
authors.lastname: Song
authors.affiliation: Department of Stomatology, Weifang People's Hospital. Weifang 261041, Shandong Province, China.
authors.forename: Shou-yi
authors.initials: SY
authors.lastname: Lu
mesh_terms: D001732:Bite Force; D020342:Finite Element Analysis; D006801:Humans; D021621:Imaging, Three-Dimensional; D008334:Mandible; D008963:Molar; D013314:Stress, Mechanical; D014070:Tooth; D014092:Tooth Root