title: [An experimental study on fracture resistance of metal-ceramic crowned incisors with different post-core systems].
abstract: OBJECTIVE
  To evaluate fracture resistance of metal-ceramic crown restored incisors with different post-and-core systems.
  
  
  METHODS
  Selected 40 intact maxillary central incisors were endodontically treated and then randomly assigned to four groups of 10 teeth each. Teeth in Group A were prepared to root canal with 10 mm in length, 1.6 mm in diameter and restored with fiber-reinforced posts and composite cores. Same final preparation but root canal with 1.5 mm in diameter was achieved for teeth in the other three groups. Teeth in Group B were restored with prefabricated titanium alloy posts and composite cores and teeth in Group C were restored with cast nickel-chromium post-cores. The posts were luted with a composite resin luting system, and metal-ceramic crowns were restored and cemented with the same luting system for all of the teeth in Group A, B and C. The other 10 teeth were restored with cast nickel-chromium post-cores and metal-ceramic crowns as a control, which were cemented with glass-ionomer cement. All restored teeth were thermo-cycled for 5000 cycles (5 degrees C/55 degrees C) as a fatigue test. The tooth was loaded in a universal testing machine at an angle of 135 degrees to the long-axis at the incisal edge with a cross-head speed of 1.5 mm/min until fracture. Fracture loads (N) and modes (repairable or catastrophic) were recorded. One-way ANOVA and SNK test were used to determine the significance of the failure loads between groups. Chi-square test was conducted for evaluation of the fracture mode.
  
  
  RESULTS
  The fracture loads from Group A, B, C and control group were (534.4 +/- 145.7) N, (499.8 +/- 168.9) N, (412.6 +/- 99.3) N, (337.4 +/- 121.2) N, respectively. A significant difference was existed among four groups (P < 0.05). The fracture loads of Group A and Group B were significantly higher than control group (P < 0.05). The repairable mode of fracture observed from Group A to control group was 80%, 40%, 20% and 30%, Group A had a significantly higher number of repairable fractures than those of the other groups (P < 0.05).
  
  
  CONCLUSIONS
  Within the limitations of this study, fiber-reinforced post has an excellent fracture resistance, and can be recommended as an alternative to cast post-cores, especially for incisor esthetic restoration.
authors.affiliation: Center of Stomatology, The First Affiliated Hospital, College of Medicine, Zhejiang University, Hangzhou 310003, China. guxinhua@mail.hz.zj.cn
authors.forename: Xin-hua
authors.initials: XH
authors.lastname: Gu
authors.forename: Jian-ping
authors.initials: JP
authors.lastname: Huang
authors.forename: Xiao-xiang
authors.initials: XX
authors.lastname: Wang
mesh_terms: D000328:Adult; D003442:Crowns; D003799:Dental Stress Analysis; D006801:Humans; D007180:Incisor; D016876:Metal Ceramic Alloys; D008875:Middle Aged; D011176:Post and Core Technique; D033081:Shear Strength
chemical_list: D016876:Metal Ceramic Alloys