title: [In vitro analysis of the effect of cyclic loading on the fracture resistance of teeth restored with different post and core systems].
abstract: OBJECTIVE
  This study aims to compare the fracture resistance of teeth restored with different post and core systems by cyclic loading test and to predict long-term effects.
  
  
  METHODS
  A total of 15 recently extracted mandibular premolars without crowns were endodontically treated. The teeth were randomly divided into three groups with five teeth in each group. Group A, teeth restored with cast metal post and core. Group B, teeth with fiber post and resin core. Group C, teeth with resin filling. All of the teeth were restored with full-cast metal crowns. The specimens were exposed to 300,000 cyclic loadings in a cyclic loading machine and 1,000 thermal cycles between 5 and 55 °C. All of the samples were loaded in AG-IS mechanical testing machine with a compressive load until fracture occurred. The fracture load and the fracture mode of each tooth were recorded.
  
  
  RESULTS
  The fracture resistance in group B and C were higher than that of the cast metal post and core restoration (P < 0.05). Repairable fractures were observed in group B and C, whereas unrestorable and catastrophic fractures were found in group A.
  
  
  CONCLUSIONS
  Fiber post and resin filling is a good choice to restore endodontically treated teeth.
authors.forename: Li
authors.initials: L
authors.lastname: Ping
authors.forename: Zhu
authors.initials: Z
authors.lastname: Zhimin
mesh_terms: D001641:Bicuspid; D003799:Dental Stress Analysis; D006801:Humans; D011176:Post and Core Technique; D014082:Tooth Fractures; D019553:Tooth, Nonvital