title: Influence of a tungsten metal conditioner on the adhesion and residual stress of porcelain bonded to cobalt-chromium alloy.
abstract: BACKGROUND
  Cobalt-chromium (CoCr) metal ceramic restorations are known to be more susceptible to cracking and interfacial failures. This is partially related to their high potential for oxidation compared with restorations made with high noble alloys. One approach that may improve their compatibility is the use of bonding agents.
  
  
  OBJECTIVE
  The purpose of this study was to investigate the influence of a tungsten metal conditioner on the adhesion and residual stress of porcelain bonded to a cobalt-chromium alloy.
  
  
  METHODS
  Eighty-one metal-porcelain bilayered specimens were manufactured and tested with a 4-point bend for adhesion and with Vickers indentation for residual stress determination. The strain energy release rate for adhesion energy and indentation residual stress was evaluated for specimens layered with and without tungsten (W) metal conditioner. Subsequent scanning electron microscopy and energy dispersive spectrometry were performed to identify fracture behavior and chemical and phase compositions.
  
  
  RESULTS
  The average strain energy release rate of the specimen group tested without the W metal conditioner was significantly higher (P<.05) (44.70 J/m(2)) than that of the group with the W metal conditioner (28.65 J/m(2)). The average residual stress of the specimen group with (0.1 MPa) and without (1.61 MPa) the W metal conditioner did not differ significantly. Scanning electron microscopy and energy dispersive spectrometry analysis enabled the modes of failure to be determined and indicated the mechanisms by which the W metal conditioner influenced the bond.
  
  
  CONCLUSIONS
  The W metal conditioner used in this study significantly lowered the strain energy release rate of the porcelain-cobalt-chromium interface and did not have a significant influence on the residual stress state of the porcelain.
authors.affiliation: Student, Department of Oral Rehabilitation, Sir John Walsh Research Institute, University of Otago, Dunedin, New Zealand.
authors.forename: Stephanie
authors.initials: S
authors.lastname: Ting
authors.affiliation: Student, Department of Oral Rehabilitation, Sir John Walsh Research Institute, University of Otago, Dunedin, New Zealand. Electronic address: lika6144@gmail.com.
authors.forename: Kai Chun
authors.initials: KC
authors.lastname: Li
authors.affiliation: Senior Lecturer, Department of Oral Rehabilitation, Sir John Walsh Research Institute, University of Otago, Dunedin, New Zealand.
authors.forename: J Neil
authors.initials: JN
authors.lastname: Waddell
authors.affiliation: Professor, Department of Geology, Sir John Walsh Research Institute, University of Otago, Dunedin, New Zealand.
authors.forename: David J
authors.initials: DJ
authors.lastname: Prior
authors.affiliation: Lecturer, Department of Oral Rehabilitation, Sir John Walsh Research Institute, University of Otago, Dunedin, New Zealand.
authors.forename: Ludwig
authors.initials: L
authors.lastname: Jansen van Vuuren
authors.affiliation: Professor, Department of Oral Rehabilitation, Sir John Walsh Research Institute, University of Otago, Dunedin, New Zealand.
authors.forename: Michael V
authors.initials: MV
authors.lastname: Swain
mesh_terms: D000268:Adhesiveness; D000465:Algorithms; D002858:Chromium Alloys / Q000737:chemistry*; D020099:Coated Materials, Biocompatible / Q000737:chemistry*; D001840:Dental Bonding; D003764:Dental Materials / Q000737:chemistry*; D003776:Dental Porcelain / Q000737:chemistry*; D003799:Dental Stress Analysis / Q000295:instrumentation; D055119:Elastic Modulus; D006244:Hardness; D006801:Humans; D008422:Materials Testing; D016876:Metal Ceramic Alloys / Q000737:chemistry; D008855:Microscopy, Electron, Scanning; D018583:Pliability; D013052:Spectrometry, X-Ray Emission; D013314:Stress, Mechanical; D013499:Surface Properties; D014414:Tungsten / Q000737:chemistry*
chemical_list: D002858:Chromium Alloys; D020099:Coated Materials, Biocompatible; D003764:Dental Materials; D016876:Metal Ceramic Alloys; D003776:Dental Porcelain; D014414:Tungsten