title: Surface analysis of dental amalgams by X-ray photoelectron spectroscopy and X-ray diffraction.
abstract: OBJECTIVE
  It is important to characterize the surface of dental amalgam in order to understand the process of mercury release from amalgam restorations in the oral cavity. The mercury evaporation occurs not only from the newly made restoration but also from the set material.
  
  
  METHODS
  The surfaces of four different types of amalgams, which had been well set, were analyzed with X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) and the relationship between surface compositions and mercury release was studied. Fresh amalgam surfaces as well as aged surfaces, which were stored for 30 days in air, were investigated using XPS and the chemical states of amalgam components and oxygen were studied. The aged surfaces were also characterized with XRD and grazing angle XRD.
  
  
  RESULTS
  With increased oxidation, the surface contents of tin and oxygen were increased in all amalgams. In contrast, the surface contents of copper and mercury were decreased. An increase of zinc or indium content were observed in zinc or indium containing amalgams, respectively. A surface layer enriched with indium and oxygen was clearly detected by XPS but not with grazing angle XRD.
  
  
  CONCLUSIONS
  The thickness of the enriched surface layer is estimated to be in the order of few nanometer, which is approximately equal to the analysis depth of XPS. In addition, the presence of metallic elements, like tin and zinc, that readily form a stable oxide layer at the surface suppress the release of mercury.
authors.affiliation: Department of Dental Materials and Engineering, Graduate School of Dental Medicine, Hokkaido University, 060-8586 Sapporo, Japan. uo@den.hokudai.ac.jp
authors.forename: Motohiro
authors.initials: M
authors.lastname: Uo
authors.forename: Anders
authors.initials: A
authors.lastname: Berglund
authors.forename: Juan
authors.initials: J
authors.lastname: Cardenas
authors.forename: Lars
authors.initials: L
authors.lastname: Pohl
authors.forename: Fumio
authors.initials: F
authors.lastname: Watari
authors.forename: Maud
authors.initials: M
authors.lastname: Bergman
authors.forename: Staffan
authors.initials: S
authors.lastname: Sjöberg
mesh_terms: D003300:Copper / Q000032:analysis; D003723:Dental Amalgam / Q000737:chemistry*; D004577:Electron Probe Microanalysis; D007204:Indium / Q000032:analysis; D008628:Mercury / Q000032:analysis; D010087:Oxides; D013499:Surface Properties; D014001:Tin / Q000032:analysis; D014835:Volatilization; D014961:X-Ray Diffraction; D015032:Zinc / Q000032:analysis
chemical_list: D010087:Oxides; D007204:Indium; D014001:Tin; D003300:Copper; D003723:Dental Amalgam; D008628:Mercury; D015032:Zinc