title: Fracture resistance and mode of failure of various types of root filled teeth.
abstract: OBJECTIVE
  To investigate ex vivo the influence of the post system on fracture resistance and failure mode of root filled incisor, canine, premolar and molar teeth.
  
  
  METHODS
  Eighty human teeth were divided into eight groups (n = 10) resulting from the interaction between the two study factors: post system (glass fibre post; cast Ni-Cr alloy post and core) and type of tooth (maxillary incisors, maxillary canines, maxillary premolars and mandibular molars). All roots were prepared with a 2-mm ferrule and restored with metal crown. Fracture resistance (N) was assessed in a mechanical testing device, and the data were analysed by two-way anova (4 × 2) followed by Tukey's test (α = 0.05). The failure mode was evaluated using an optical stereomicroscope and classified according to the location of the failure. Failure mode data were analysed by two-factor anova and Student-Newman-Keuls (SNK) tests (α = 0.05). Correlation between fracture resistance and failure mode was analysed by linear regression.
  
  
  RESULTS
  Glass fibre and cast posts and cores had similar fracture resistance, regardless of the type of tooth. Canines and molars had significantly higher fracture resistance (P < 0.001) than premolars. Incisors teeth had significantly lower fracture resistance (P < 0.001) than premolars. The fracture mode for incisors, premolars and molars was more amenable to restoration when the teeth were restored with glass fibre posts. Fracture resistance had no correlation with fracture mode, regardless of the post system and type of tooth analysed.
  
  
  CONCLUSIONS
  Post system had no significant effect on fracture resistance, regardless of the type of tooth. The mode of fracture was more restorable with glass fibre posts.
authors.affiliation: Department of Operative Dentistry and Dental Materials, School of Dentistry, Federal University of Uberlândia, Uberlândia, Brazil.
authors.forename: C G
authors.initials: CG
authors.lastname: Castro
authors.forename: F R
authors.initials: FR
authors.lastname: Santana
authors.forename: M G
authors.initials: MG
authors.lastname: Roscoe
authors.forename: P C
authors.initials: PC
authors.lastname: Simamoto
authors.forename: P C F
authors.initials: PC
authors.lastname: Santos-Filho
authors.forename: C J
authors.initials: CJ
authors.lastname: Soares
mesh_terms: D000134:Acid Etching, Dental / Q000379:methods; D001641:Bicuspid / Q000503:physiopathology; D001696:Biomechanical Phenomena; D002858:Chromium Alloys / Q000737:chemistry; D003188:Composite Resins / Q000737:chemistry; D003442:Crowns; D003481:Cuspid / Q000503:physiopathology; D003738:Dental Cements / Q000737:chemistry; D003764:Dental Materials / Q000737:chemistry; D003799:Dental Stress Analysis / Q000295:instrumentation; D005898:Glass / Q000737:chemistry; D006801:Humans; D007180:Incisor / Q000503:physiopathology; D008334:Mandible; D008422:Materials Testing; D008437:Maxilla; D008963:Molar / Q000503:physiopathology; D010756:Phosphoric Acids / Q000737:chemistry; D011176:Post and Core Technique; D018915:Root Canal Preparation / Q000379:methods; D013314:Stress, Mechanical; D014082:Tooth Fractures / Q000503:physiopathology*; D019553:Tooth, Nonvital / Q000503:physiopathology*
chemical_list: C554641:Adper single bond 2; D002858:Chromium Alloys; D003188:Composite Resins; D003738:Dental Cements; D003764:Dental Materials; C444701:Filtek Z250; D010756:Phosphoric Acids; C009753:fiberglass; C030242:phosphoric acid