title: Static and cyclic loading of fiber-reinforced dental resin.
abstract: OBJECTIVE
  The aim of this study was to evaluate the flexure strength of unidirectional fiber-reinforced resins under static and cyclic loading with and without thermal cycling.
  
  
  METHODS
  The fiber-reinforced resin materials chosen for this project were commercially available endodontic posts and commercially procured bar samples. For all materials, controls for flexure strength were tested in air and in water using three-point loading. Specimens were thermal cycled between 7 and 63 degrees C for 6000 cycles. A staircase approach was used to determine the flexure fatigue limit and scanning microscopy was used to examine the microstructure.
  
  
  RESULTS
  The carbon/graphite fiber-reinforced resin posts and the glass FiberKor posts were significantly stronger than the ceramic (zirconia) and the other glass-reinforced resin materials. Thermal cycling caused a significant lowering (11-24%) of the flexure strength for each resin based post system. The ceramic post system decreased only by 2%. Further, for standard size glass fiber-reinforced resin bars, no significant differences between testing in air and water was observed, but a significant difference between static and cyclic loading was noted.
  
  
  CONCLUSIONS
  The decreases in the strength property due to thermal cycling and the cyclic loading of these materials indicates that their utilization in the oral environment enhances their degradation, and potentially shortens their clinical life.
authors.affiliation: Department of Restorative Dentistry m/c 555, 337A College of Dentistry, University of Illinois at Chicago, 801 South Paulina Street, Chicago, IL 60612-7212, USA. drummond@uic.edu
authors.forename: James L
authors.initials: JL
authors.lastname: Drummond
authors.forename: Mahendra S
authors.initials: MS
authors.lastname: Bapna
mesh_terms: D000388:Air; D017438:Bisphenol A-Glycidyl Methacrylate / Q000737:chemistry; D002244:Carbon / Q000737:chemistry; D000077482:Carbon Fiber; D003188:Composite Resins / Q000737:chemistry*; D003764:Dental Materials / Q000737:chemistry*; D005898:Glass / Q000737:chemistry; D006801:Humans; D008422:Materials Testing; D008689:Methacrylates / Q000737:chemistry; D008855:Microscopy, Electron, Scanning; D018583:Pliability; D011076:Polycarboxylate Cement / Q000737:chemistry; D011176:Post and Core Technique / Q000295:instrumentation; D013314:Stress, Mechanical; D013499:Surface Properties; D013816:Thermodynamics; D014867:Water; D015040:Zirconium / Q000737:chemistry
chemical_list: D000077482:Carbon Fiber; D003188:Composite Resins; D003764:Dental Materials; C113550:FiberKor, sculpture; D008689:Methacrylates; D011076:Polycarboxylate Cement; C009753:fiberglass; D014867:Water; C005506:polycarbonate; D017438:Bisphenol A-Glycidyl Methacrylate; D002244:Carbon; D015040:Zirconium; C028541:zirconium oxide