title: [Study of stress distribution in mandibular first premolar restored by composite resin with root screw of different length in different occlusion].
abstract: OBJECTIVE
  To investigate stress distribution in mandibular first premolar restored by composite resin with root screw of different length in different occlusion.
  
  
  METHODS
  An three dimensional finite element model of mandibular first premolar restored by composite resin with root screw was constructed by using spiral CT image reconstruction technique, Mimics, Pro/Engineer, Pro/Mechanica software. Based on this model, stress distribution in dentin, composite resin and root screw was analyzed in the situation of different screw length and different occlusion.
  
  
  RESULTS
  When the occlusion was tripod contact and cusp tip-ovoid fossa contact, the stress of dentin, composite resin and root screw were all much less than their compressive strength. And also in this situation, the stress of bond surface between the composite resin and dentin was less than the bond strength of composite resin. The screw was longer but no more than 8 mm, the dentin stress distributes better.
  
  
  CONCLUSIONS
  In the restoration of large area mandibular first premolar crown defection, tripod contact and cusp tip-ovoid fossa contact with 8 mm root screw is recommended.
authors.affiliation: State Key Laboratory of Oral Diseases, Sichuan University, Chengdu 610041, China.
authors.forename: Liu-jia
authors.initials: LJ
authors.lastname: Wei
authors.forename: Xiao-ke
authors.initials: XK
authors.lastname: Hong
authors.forename: Qian
authors.initials: Q
authors.lastname: Liu
authors.forename: Hao-yang
authors.initials: HY
authors.lastname: Xing
authors.forename: Xiao-qing
authors.initials: XQ
authors.lastname: Li
authors.forename: Min
authors.initials: M
authors.lastname: Zhang
mesh_terms: D001641:Bicuspid; D001863:Bone Screws; D003188:Composite Resins; D003442:Crowns; D003766:Dental Occlusion; D003799:Dental Stress Analysis; D003804:Dentin; D020342:Finite Element Analysis; D006801:Humans; D014092:Tooth Root; D019553:Tooth, Nonvital
chemical_list: D003188:Composite Resins