title: [Finite element analysis of the maxillary central incisor with traditional and modified crown lengthening surgery and post-core restoration in management of crown-root fracture].
abstract: OBJECTIVE
  To construct three-dimensional finite element models with modified crown lengthening surgery and post-core restoration in management of various crown-root fracture types, to investigate the intensity and distribution of stressin models mentioned above, and to compare and analyze the indications of traditional and modified crown lengthening surgeries from the mechanic point of view.
  
  
  METHODS
  Nine three-dimensional finite element models with modified crown lengthening surgery and post-core restoration were established and analyzed by micro-CT scanning technique, dental impression scanner, Mimics 10.0, Geomagic studio 9.0 and ANSYS 14.0 software. The von Mises stress of dentin, periodontal ligament, alveolar bone, post and core, as well as the periodontal ligament area and threshold limit value were calculated and compared with the findings of traditional crown lengthening models which had been published earlierby our research group.
  
  
  RESULTS
  The von Mises stress intensity of modified crown lengthening models were: dentin>post>core>alveolar bone>periodontal ligament. The maximum von Mises stress of dentin(44.37-80.58 MPa)distributed in lingual central shoulder. The periodontal ligament area of the modified crown lengthening surgery was reduced by 6% to 28%, under the same crown-root fracture conditions, the periodontal ligament area of modified crown lengthening models was larger than that of the traditional crown lengthening models. In modified crown lengthening surgery models, the von Mises stress of periodontal ligament of B3L1m, B3L2m, B3L3m models exceeded their limit values, however, the von Mises stress of periodontal ligament of the B2L2c, B2L3c, B3L1c, B3L2c, B3L3c models exceeded their limit values in traditional crown lengthening surgery models.
  
  
  CONCLUSIONS
  The modified crown lengthening surgery conserves more periodontal supporting tissues, which facilitates the long-term survival of teeth. The indication of modified crown lengthening surgery is wider than traditional method. The maxillary central incisors with labial fracture at gingival margin level and with palatal fracture at or below the alveolar crest level are not the indication of the crown lengthening surgery.
authors.affiliation: Department of Periodontology, Peking University School and Hospital of Stomatology, Beijing 100081, China.
authors.forename: M
authors.initials: M
authors.lastname: Zhen
authors.affiliation: Department of Periodontology, Peking University School and Hospital of Stomatology, Beijing 100081, China.
authors.forename: Y P
authors.initials: YP
authors.lastname: Wei
authors.affiliation: Department of Periodontology, Peking University School and Hospital of Stomatology, Beijing 100081, China.
authors.forename: W J
authors.initials: WJ
authors.lastname: Hu
authors.affiliation: Department of Mechanics and Engineering Science, College of Engineering, Peking University, Beijing 100871, China.
authors.forename: Q G
authors.initials: QG
authors.lastname: Rong
authors.affiliation: Department of Prosthodontics, Peking University School and Hospital of Stomatology, Beijing 100081, China.
authors.forename: H
authors.initials: H
authors.lastname: Zhang
mesh_terms: D000539:Alveolar Process; D016556:Crown Lengthening / Q000379:methods*; D003442:Crowns; D003799:Dental Stress Analysis; D003804:Dentin; D020342:Finite Element Analysis; D006801:Humans; D007180:Incisor / Q000293:injuries*; D010513:Periodontal Ligament; D011176:Post and Core Technique; D020711:Threshold Limit Values; D019228:Tooth Crown / Q000293:injuries*; D014082:Tooth Fractures / Q000601:surgery*; D014092:Tooth Root / Q000293:injuries*; D055114:X-Ray Microtomography / Q000379:methods