title: [Analysis the effect on the stress of root canal wall of pulpless teeth by different degree of root canal preparation].
abstract: OBJECTIVE
  To analyze the stress variations of wall of root canal of pulpless teeth that resulted from different diameters of root canal.
  
  
  METHODS
  On the basis of the finite-element model of the mandibular first molar that modified by routine, diameter of root canal was modified and enlarged so as to the diameter of root canal was 1/3 and 1/2 of root diameter, then modified models were loaded and the maximal stress of each part of teeth and wall of root canal was calculated.
  
  
  RESULTS
  The results revealed that enlargement of root canal diameter will bring on increase of stress of root canal wall at the orifice and coronal 1/3. The stress difference of lateral loading was greater than that of vertical loading.
  
  
  CONCLUSIONS
  The principle of root canal preparation should be infected material removed and good shape of root canal gained. Over-preparation is unnecessary and harmful.
authors.affiliation: Department of Oral Medicine, Ninth People's Hospital, Shanghai Second Medical University, Shanghai 200011, China. hj1221@online.sh.cn
authors.forename: Jin
authors.initials: J
authors.lastname: Hong
authors.forename: Wen-wei
authors.initials: WW
authors.lastname: Xia
authors.forename: Huan-guo
authors.initials: HG
authors.lastname: Xiong
mesh_terms: D003786:Dental Pulp Cavity / Q000503:physiopathology*; D003799:Dental Stress Analysis; D006801:Humans; D018915:Root Canal Preparation; D019553:Tooth, Nonvital / Q000503:physiopathology*