title: [Study on root fracture and alveolar bone absorption of doweled lower premolars].
abstract: OBJECTIVE
  The aim of this study was to examine root fractures in the doweled lower premolars and their relationship to alveolar bone absorption on the buccal aspect of the abutment teeth.
  
  
  METHODS
  Experiment 1. Fractures in the roots of the abutment teeth and absorption of the surrounding alveolar bone was visualized by Multi-image Micro CT (3DX) in nine lower premolar abutment teeth that had lost both their posts and their. Experiment 2. The stresses in the teeth were analyzed using a three-dimensional finite element model, both models with and without alveolar bone absorption, as determined from Experiment 1. The stress distributions of von Mises equivalent stress and the shear stresses in the XZ, YZ and XY direct ions were examined.
  
  
  RESULTS
  Experiment 1. The absorption of the alveolar bone was observed on the buccal side, and the fractures in the roots were observed in the lingual to buccal direction. Experiment 2. In the case without alveolar bone absorption, the XY shear stress in the root for mesial or distal loads was concentrated near the cervix with a positive stress value, and close to the end of the post with a negative stress value. In the alveolar bone absorption model, the XY shear stress in the root for mesial or distal loads was concentrated close to the end of the post on the lingual side with a positive stress value and on the buccal side with a negative stress value.
  
  
  CONCLUSIONS
  In the case without alveolar bone absorption, on stress concentration was observed at the end of the post. Otherwise, based on the results of the finite element model analysis, for mesial or distal loads, the root fracture in the abutment teeth would be considered to be caused by absorption of the alveolar bone and the buccal aspect.
authors.affiliation: The 2nd Department of Prosthetic Dentistry, Matsumoto Dental University.
authors.forename: Hiroko
authors.initials: H
authors.lastname: Misawa
mesh_terms: D016301:Alveolar Bone Loss / Q000150:complications* / Q000000981:diagnostic imaging / Q000503:physiopathology; D001641:Bicuspid / Q000000981:diagnostic imaging; D001696:Biomechanical Phenomena; D000044:Dental Abutments; D006801:Humans; D021621:Imaging, Three-Dimensional; D008334:Mandible; D008336:Mandibular Diseases / Q000150:complications* / Q000000981:diagnostic imaging / Q000503:physiopathology; D003765:Models, Dental; D011176:Post and Core Technique; D033081:Shear Strength; D013314:Stress, Mechanical; D014057:Tomography, X-Ray Computed; D014082:Tooth Fractures / Q000000981:diagnostic imaging / Q000209:etiology* / Q000503:physiopathology; D014092:Tooth Root / Q000000981:diagnostic imaging / Q000293:injuries* / Q000503:physiopathology