title: [Effects of different tooth preparations on the fracture behavior of teeth with severe wedge-shaped defect restored with post and core crowns].
abstract: OBJECTIVE
  This study aimed to investigate the effects of different tooth preparations on the fracture strength and pattern of failure of teeth with severe wedge-shaped defect restored with post and core crowns.
  
  
  METHODS
  According to whether the teeth above the wedge-shaped defect was removed (represented by B) or not (represented by A), the ferrule next to the wedge-shaped defect was prepared (represented by D) or not (represented by C), the cast post-and-core was chosen (represented by E) or glass-fiber post and resin core was chosen (represented by F). A total of 64 human mandibular premolar teeth were randomly divided into 8 groups: A1-1 (A + C + E), A1-2 (A + C + F), A2-1 (A + D + E), A2-2 (A + D + F), B1-1 (B + C + E), B1-2 (B + C + F), B2-1 (B + D + E), B2-2 (B + D + F), each group 8 teeth. All the teeth were prepared and restored accordingly and then mounted on an electronic pressure universal testing machine. The maximum fracture strength and the patterns of failure were recorded.
  
  
  RESULTS
  1) The fracture strength of Group A1-1 > that of Group B1-1, Group A1-2 > Group B1-2, Group B2-1 > Group B1-1, and Group B2-1 > Group B2-2 with significant differences (P < 0.05). 2) The patterns of repairable fracture in Group A1-2 and B1-2 were both 37.5%, and that of the other groups were 0. Furthermore, the difference was significant, and Group A1-2 and B1-2 were higher than other groups.
  
  
  CONCLUSIONS
  The maintenance of the overhang above the severe wedge-shaped defect aid in the improvement of the fracture strength of the tooth restored with post and core crown. The ferrule of the wedge-shaped defect is not recommended to be prepared. Furthermore, the glass-fiber post and resin core is favorable for the re-repair of the teeth than the cast post and core.
authors.forename: Dandan
authors.initials: D
authors.lastname: Feng
authors.forename: Dong
authors.initials: D
authors.lastname: Qi
authors.forename: Xuefen
authors.initials: X
authors.lastname: Lin
authors.forename: Tingting
authors.initials: T
authors.lastname: Ding
authors.forename: Ping
authors.initials: P
authors.lastname: Ji
mesh_terms: D001641:Bicuspid; D003442:Crowns; D005898:Glass; D006801:Humans; D007180:Incisor; D011176:Post and Core Technique; D014082:Tooth Fractures; D019246:Tooth Preparation
chemical_list: C009753:fiberglass