title: Retrieval analysis of different orthodontic brackets: the applicability of electron microprobe techniques for determining material heterogeneities and corrosive potential.
abstract: OBJECTIVE
  The objective of this study was to investigate the applicability of micro-analytical methods with high spatial resolution to the characterization of the composition and corrosion behavior of two bracket systems.
  
  
  METHODS
  The surfaces of six nickel-free brackets and six nickel-containing brackets were examined for signs of corrosion and qualitative surface analysis using an electron probe microanalyzer (EPMA), prior to bonding to patient's tooth surfaces and four months after clinical use. The surfaces were characterized qualitatively by secondary electron (SE) images and back scattered electron (BSE) images in both compositional and topographical mode. Qualitative and quantitative wavelength-dispersive analyses were performed for different elements, and by utilizing qualitative analysis the relative concentration of selected elements was mapped two-dimensionally. The absolute concentration of the elements was determined in specially prepared brackets by quantitative analysis using pure element standards for calibration and calculating correction-factors (ZAF).
  
  
  RESULTS
  Clear differences were observed between the different bracket types. The nickel-containing stainless steel brackets consist of two separate pieces joined by a brazing alloy. Compositional analysis revealed two different alloy compositions, and reaction zones on both sides of the brazing alloy. The nickel-free bracket was a single piece with only slight variation in element concentration, but had a significantly rougher surface. After clinical use, no corrosive phenomena were detectable with the methods applied. Traces of intraoral wear at the contact areas between the bracket slot and the arch wire were verified.
  
  
  CONCLUSIONS
  Electron probe microanalysis is a valuable tool for the characterization of element distribution and quantitative analysis for corrosion studies.
authors.affiliation: Dental Clinic 3 - Department of Orthodontics, University Clinic Erlangen, Erlangen, Germany. alexandra.holst@uk-erlangen.de
authors.forename: Alexandra Ioana
authors.initials: AI
authors.lastname: Holst
authors.forename: Stefan
authors.initials: S
authors.lastname: Holst
authors.forename: Ursula
authors.initials: U
authors.lastname: Hirschfelder
authors.forename: Volker Von
authors.initials: VV
authors.lastname: Seckendorff
mesh_terms: D000293:Adolescent; D003343:Corrosion; D003764:Dental Materials / Q000737:chemistry*; D004577:Electron Probe Microanalysis / Q000379:methods*; D006801:Humans; D008422:Materials Testing; D009532:Nickel / Q000737:chemistry*; D016910:Orthodontic Brackets; D015203:Reproducibility of Results; D013193:Stainless Steel / Q000737:chemistry*; D013499:Surface Properties; D013997:Time Factors
chemical_list: D003764:Dental Materials; D013193:Stainless Steel; D009532:Nickel