title: [Effect of cone angle on fracture resistance force of root and post-core system].
abstract: OBJECTIVE
  To study the effect of cone angle on fracture resistance force of root and post-core system.
  
  
  METHODS
  Forty-two simulated tooth roots made of polymethacrylate (PMMA) were divided into six groups according to the root canal cone angles of 0 degrees, 3.93 degrees, 5.71 degrees, 7.48 degrees, 11.31 degrees and 14.71 degrees. Cast post and cores were manufactured and cemented with zinc polycarboxylate cement (PC). Casting the post and core to restore every simulated tooth root. Each specimen was embedded in acrylic resin and then fixed in a special jig on the universal load-testing machine. A compressive load was applied at a 90-degree angle to the long axis of the core until fracture, at a crosshead speed of 1 mm/min. The maximum of load was recorded.
  
  
  RESULTS
  The mean values of load in root and post-core system were 0.1225 kN, 0.1498 kN, 0.1600 kN, 0.1893 kN, 0.1078 kN and 0.0945 kN. There were significant differences in the fracture resistance among groups.
  
  
  CONCLUSIONS
  The fracture resistance force of cast post and core increased with the enlargement of post cone angles under certain conditions.
authors.affiliation: Department of Prosthodontics, West China Stomatological Hospital, Sichuan University, Chengdu 610041, China.
authors.forename: Yan-nan
authors.initials: YN
authors.lastname: Ma
authors.forename: Xin-min
authors.initials: XM
authors.lastname: Chen
authors.forename: Li-ya
authors.initials: LY
authors.lastname: Xu
authors.forename: Yan
authors.initials: Y
authors.lastname: Yang
mesh_terms: D003442:Crowns; D019232:Dental Restoration Failure; D003799:Dental Stress Analysis; D006801:Humans; D011176:Post and Core Technique; D014082:Tooth Fractures / Q000517:prevention & control*