title: Comparison of fatigue resistance and failure modes between metal-ceramic and all-ceramic crowns by cyclic loading in water.
abstract: OBJECTIVE
  To compare fatigue resistance and fracture mode of metal-ceramic crowns with all-ceramic crowns containing yttria tetragonal zirconia polycrystal (Y-TZP) frameworks under compressive cycling loading in water.
  
  
  METHODS
  Twenty specimens of ivory were randomized and individually prepared to receive anatomically shaped metal-ceramic (n=10) or veneered Y-TZP all-ceramic crowns (n=10). All steps in production were equivalent to clinical situations. Resistance to fatigue fracture was tested under compressive cyclic loading using a universal testing machine, with a loading frequency of 12Hz using a spherical tungsten carbide indenter (6mm diameter) in distilled water. The maximum compressive load was increased as the number of cycles increased (600,000 cycles at 400N, 200,000 cycles at 600 N, 200,000 cycles at 800 N and 200,000 cycles at 1000 N). The specimens were inspected after each loading sequence for initial failures such as infractions. Final failure was considered as any loss of material which automatically ended the test and the number of cycles until final failure was recorded. Fractographic analysis of the fractured specimens was performed with scanning electron microscopy (SEM).
  
  
  RESULTS
  The two types of crowns exhibit similar fatigue resistance (P=0.87) to compressive cycling loading under wet conditions. The failure modes as observed with SEM were similar in the two groups and were found in the veneer ceramic, except that three veneered Y-TZP all-ceramic crowns displayed a complete framework fracture.
  
  
  CONCLUSIONS
  Within the limitation of this study using simulated oral masticatory function, the results revealed that the fatigue resistance was similar for the two crown types.
  
  
  CONCLUSIONS
  In this study metal-ceramic crowns and veneered Y-TZP all-ceramic crowns showed similar fracture resistance to compressive cycling loading in water. The test conditions were simulating clinical conditions. Thus, the result may predict the long-term clinical performance of these types of crowns.
authors.affiliation: Section of Prosthetic Dentistry, Department of Dentistry, Aarhus University, Vennelyst Boulevard 9, Aarhus, Denmark. Electronic address: mhnicolaisen@odont.au.dk.
authors.forename: Maj H
authors.initials: MH
authors.lastname: Nicolaisen
authors.affiliation: Section of Prosthetic Dentistry, Department of Dentistry, Aarhus University, Vennelyst Boulevard 9, Aarhus, Denmark. Electronic address: golnosh.bahrami@odont.au.dk.
authors.forename: Golnosh
authors.initials: G
authors.lastname: Bahrami
authors.affiliation: Department of Oral Biology, School of Dentistry, University of Leeds, Clarendon Way, Leeds LS2 9LU, UK. Electronic address: s.finlay@leeds.ac.uk.
authors.forename: Scott
authors.initials: S
authors.lastname: Finlay
authors.affiliation: Section of Prosthetic Dentistry, Department of Dentistry, Aarhus University, Vennelyst Boulevard 9, Aarhus, Denmark. Electronic address: flemming.isidor@odont.au.dk.
authors.forename: Flemming
authors.initials: F
authors.lastname: Isidor
mesh_terms: D002516:Ceramics / Q000737:chemistry*; D017076:Computer-Aided Design; D003442:Crowns; D003764:Dental Materials / Q000737:chemistry*; D003776:Dental Porcelain / Q000737:chemistry; D019232:Dental Restoration Failure; D003799:Dental Stress Analysis / Q000295:instrumentation; D003801:Dental Veneers; D006047:Gold Alloys / Q000737:chemistry; D006244:Hardness; D006801:Humans; D008422:Materials Testing; D016876:Metal Ceramic Alloys / Q000737:chemistry*; D008855:Microscopy, Electron, Scanning; D011897:Random Allocation; D013314:Stress, Mechanical; D013499:Surface Properties; D017973:Tungsten Compounds / Q000737:chemistry; D014867:Water / Q000737:chemistry; D015019:Yttrium / Q000737:chemistry*; D015040:Zirconium / Q000737:chemistry*
chemical_list: D003764:Dental Materials; D006047:Gold Alloys; D016876:Metal Ceramic Alloys; D017973:Tungsten Compounds; C499362:yttria stabilized tetragonal zirconia; D014867:Water; C002802:tungsten carbide; D003776:Dental Porcelain; D015019:Yttrium; D015040:Zirconium
keywords: CAD–CAM; Cyclic loading; Dental material; Fatigue test; Metal-ceramic; Yttria-stabilized tetragonal zirconia polycrystals ceramic