title: Metallurgical and electrochemical characterization of contemporary silver-based soldering alloys.
abstract: OBJECTIVE
  To investigate the microstructure, hardness, and electrochemical behavior of four contemporary Ag-based soldering alloys used for manufacturing orthodontic appliances.
  
  
  METHODS
  The Ag-based alloys tested were Dentaurum Universal Silver Solder (DEN), Orthodontic Solders (LEO), Ortho Dental Universal Solder (NOB), and Silver Solder (ORT). Five disk-shaped specimens were produced for each alloy, and after metallographic preparation their microstructural features, elemental composition, and hardness were determined by scanning electron microscopy with energy-dispersive X-ray (EDX) microanalysis, X-ray diffraction (XRD) analysis, and Vickers hardness testing. The electrochemical properties were evaluated by anodic potentiodynamic scanning in 0.9% NaCl and Ringer's solutions. Hardness, corrosion current (Icorr), and corrosion potential (Ecorr) were statistically analyzed by one-way analysis of variance and Tukey test (α=.05).
  
  
  RESULTS
  EDX analysis showed that all materials belong to the Ag-Zn-Cu ternary system. Three different mean atomic contrast phases were identified for LEO and ORT and two for DEN and NOB. According to XRD analysis, all materials consisted of Ag-rich and Cu-rich face-centered cubic phases. Hardness testing classified the materials in descending order as follows: DEN, 155±3; NOB, 149±3; ORT, 141±4; and LEO, 136±8. Significant differences were found for Icorr of NOB in Ringer's solution and Ecorr of DEN in 0.9% NaCl solution.
  
  
  CONCLUSIONS
  Ag-based soldering alloys demonstrate great diversity in their elemental composition, phase size and distribution, hardness, and electrochemical properties. These differences may anticipate variations in their clinical performance.
authors.affiliation: a  PhD Graduate Student, Department of Biomaterials, School of Dentistry, National and Kapodistrian University of Athens, Athens, Greece.
authors.forename: Argyro
authors.initials: A
authors.lastname: Ntasi
authors.forename: Youssef
authors.initials: Y
authors.lastname: Al Jabbari
authors.forename: Wolf Dieter
authors.initials: WD
authors.lastname: Mueller
authors.forename: George
authors.initials: G
authors.lastname: Eliades
authors.forename: Spiros
authors.initials: S
authors.lastname: Zinelis
mesh_terms: D003300:Copper / Q000737:chemistry; D003343:Corrosion; D003722:Dental Alloys / Q000737:chemistry*; D012994:Dental Soldering / Q000379:methods*; D004563:Electrochemistry; D004577:Electron Probe Microanalysis; D006244:Hardness; D006801:Humans; D008422:Materials Testing; D008669:Metallurgy; D008855:Microscopy, Electron, Scanning; D009967:Orthodontic Appliances; D011199:Potentiometry; D012834:Silver / Q000737:chemistry*; D013052:Spectrometry, X-Ray Emission; D044366:Transition Temperature; D014961:X-Ray Diffraction; D015032:Zinc / Q000737:chemistry
chemical_list: D003722:Dental Alloys; D012834:Silver; D003300:Copper; D015032:Zinc