title: The effect of zinc levels in a gold-based alloy on porcelain-metal bonding.
abstract: OBJECTIVE
  The purpose of this study was to ascertain whether the amount of Zn in gold alloys contributes to porcelain-metal bonding.
  
  
  METHODS
  Experiments were carried out using a commercial Pd-free gold alloy with a nominal composition of 88.7 wt% Au, 9.49 wt% Pt, 1.5 wt% Zn, 0.1 wt% Mn, 0.2 wt% Rh, and 0.1 wt% Ir, which contains Zn and no other elements (In, Sn, Fe) known to affect porcelain-metal bond strength. To establish the effect of oxidation of the metal surface, porcelain was applied both to preoxidized and to non-preoxidized metal specimens. The bond strength was evaluated by means of the ISO 9693: 1999 crack initiation test. A conventional gold alloy was used as a control. The elemental distributions at the porcelain/alloy interfaces were analyzed in cross section by electron probe microanalysis. Additionally, after the bond strength test, cross-sections of the interfaces of the debonded specimens were microscopically analyzed to characterize the fracture mode.
  
  
  RESULTS
  The Pd-free gold alloy joints showed significantly higher bond strength values than joints made with conventional gold alloy. Preoxidation treatment significantly increases the bond strength, in the preoxidized joints Zn was highly localized at the interface and diffused into the porcelain up to about 10 μm from the interface, and the joint failed by cohesive fracture in the porcelain. In contrast, the non-preoxidized joint showed mainly adhesive fracture at the porcelain/alloy interface.
  
  
  CONCLUSIONS
  The presence of Zn in gold alloys plays a part in establishing chemical bonding thus improving the bond strength between porcelain and alloy.
authors.affiliation: Department of Dental Materials Science, School of Dentistry, Aichi Gakuin University, Nagoya, Japan. masaki@dpc.agu.ac.jp
authors.forename: Masaki
authors.initials: M
authors.lastname: Asakura
authors.forename: Yoshiko
authors.initials: Y
authors.lastname: Kominami
authors.forename: Tatsuhide
authors.initials: T
authors.lastname: Hayashi
authors.forename: Shozo
authors.initials: S
authors.lastname: Tsuruta
authors.forename: Tatsushi
authors.initials: T
authors.lastname: Kawai
mesh_terms: D001840:Dental Bonding; D003776:Dental Porcelain / Q000737:chemistry*; D003799:Dental Stress Analysis; D055119:Elastic Modulus; D004577:Electron Probe Microanalysis; D006046:Gold / Q000032:analysis; D006047:Gold Alloys / Q000032:analysis* / Q000737:chemistry; D006801:Humans; D007495:Iridium / Q000032:analysis; D008345:Manganese / Q000032:analysis; D008422:Materials Testing; D016876:Metal Ceramic Alloys / Q000032:analysis* / Q000737:chemistry; D010084:Oxidation-Reduction; D010100:Oxygen / Q000032:analysis; D010984:Platinum / Q000032:analysis; D018583:Pliability; D012238:Rhodium / Q000032:analysis; D012825:Silicon / Q000032:analysis; D013314:Stress, Mechanical; D013499:Surface Properties; D013816:Thermodynamics; D015032:Zinc / Q000032:analysis* / Q000737:chemistry
chemical_list: D006047:Gold Alloys; D016876:Metal Ceramic Alloys; D003776:Dental Porcelain; D008345:Manganese; D007495:Iridium; D010984:Platinum; D006046:Gold; D012238:Rhodium; D015032:Zinc; D010100:Oxygen; D012825:Silicon