title: Fracture resistance and failure mode of fatigued endodontically treated teeth restored with fiber-reinforced resin posts and metallic posts in vitro.
abstract: BACKGROUND
  Fracture of restored endodontically treated teeth is a common complication. The mechanical properties of post systems may play a role in the incidence of tooth fracture.
  
  
  OBJECTIVE
  The purpose of this study was to evaluate in vitro the fracture resistance and pattern of fracture of endodontically treated teeth restored with three different post systems.
  
  
  METHODS
  Posts used were fiber-reinforced composite resin posts (FRC post), custom cast silver-palladium, and nickel-chromium posts and cores. A 3-point bending test was performed to calculate flexural strengths and elastic moduli of the specimens. Sixty extracted human maxillary canines were endodontically treated and divided into three groups (n = 20). All-ceramic crowns were fabricated and cemented with Variolink II resin cement. Ten specimens of each group were subjected to a constantly increasing load until fracture. The other 10 specimens were fatigued for 106 cycles in a custom-made fatigue machine. Recorded failure loads and modes were statistically compared with one-way anova and Tukey-HSD tests (α = 0.05).
  
  
  RESULTS
  The resistance to fracture of teeth restored with FRC posts, composite resin cores, and Empress II crowns was similar to that of teeth restored with cast posts and cores (P = 0.162). Supracrestal (above root/level of acrylic resin base) oblique fracture was the predominant mode of fracture associated with teeth restored with FRC posts (70%), while vertical root fractures were more common with teeth restored with cast posts and cores.
  
  
  CONCLUSIONS
  Teeth restored with the FRC post system did not exhibit vertical root fractures and were less likely to show root fracture. Sixty to 80% of teeth restored with both types of cast posts and cores showed vertical and subcrestal root fractures.
authors.affiliation: College of Dentistry, University of Dammam, Dammam, Saudi Arabia.
authors.forename: Fahad
authors.initials: F
authors.lastname: A Alharbi
authors.forename: Dan
authors.initials: D
authors.lastname: Nathanson
authors.forename: Steven M
authors.initials: SM
authors.lastname: Morgano
authors.forename: Nadim Z
authors.initials: NZ
authors.lastname: Baba
mesh_terms: D006801:Humans; D066298:In Vitro Techniques; D011176:Post and Core Technique; D012390:Root Canal Therapy
keywords: crown fracture; dental trauma; root fracture