title: Corrosion behavior of self-ligating and conventional metal brackets.
abstract: OBJECTIVE
  To test the null hypothesis that the aging process in self-ligating brackets is not higher than in conventional brackets.
  
  
  METHODS
  Twenty-five conventional (GN-3M/Unitek; GE-GAC; VE-Aditek) and 25 self-ligating (SCs-3M/Unitek; INs-GAC; ECs-Aditek) metal brackets from three manufacturers (n = 150) were submitted to aging process in 0.9% NaCl solution at a constant temperature of 37 ± 1°C for 21 days. The content of nickel, chromium and iron ions in the solution collected at intervals of 7, 14 and 21 days was quantified by atomic absorption spectrophotometry. After the aging process, the brackets were analyzed by scanning electron microscopy (SEM) under 22X and 1,000X magnifications.
  
  
  RESULTS
  Comparison of metal release in self-ligating and conventional brackets from the same manufacturer proved that the SCs group released more nickel (p < 0.05) than the GN group after 7 and 14 days, but less chromium (p < 0.05) after 14 days and less iron (p < 0.05) at the three experimental time intervals. The INs group released less iron (p < 0.05) than the GE group after 7 days and less nickel, chromium and iron (p < 0.05) after 14 and 21 days. The ECs group released more nickel, chromium and iron (p < 0.05) than the VE group after 14 days, but released less nickel and chromium (p < 0.05) after 7 days and less chromium and iron (p < 0.05) after 21 days. The SEM analysis revealed alterations on surface topography of conventional and self-ligating brackets.
  
  
  CONCLUSIONS
  The aging process in self-ligating brackets was not greater than in conventional brackets from the same manufacturer. The null hypothesis was accepted.
authors.forename: Lúcio Henrique Esmeraldo Gurgel
authors.initials: LH
authors.lastname: Maia
authors.forename: Hibernon
authors.initials: H
authors.lastname: Lopes Filho
authors.forename: Antônio Carlos de Oliveira
authors.initials: AC
authors.lastname: Ruellas
authors.forename: Mônica Tirre de Souza
authors.initials: MT
authors.lastname: Araújo
authors.forename: Delmo Santiago
authors.initials: DS
authors.lastname: Vaitsman
mesh_terms: D002857:Chromium / Q000737:chemistry; D003343:Corrosion; D003722:Dental Alloys / Q000737:chemistry*; D004058:Diffusion; D006801:Humans; D007501:Iron / Q000737:chemistry; D008422:Materials Testing; D008855:Microscopy, Electron, Scanning; D009532:Nickel / Q000737:chemistry; D016382:Orthodontic Appliance Design; D016910:Orthodontic Brackets; D012965:Sodium Chloride / Q000737:chemistry; D013054:Spectrophotometry, Atomic; D013193:Stainless Steel / Q000737:chemistry; D013499:Surface Properties; D013696:Temperature; D013997:Time Factors
chemical_list: D003722:Dental Alloys; C426023:austenitic steel; D002857:Chromium; D013193:Stainless Steel; D012965:Sodium Chloride; D009532:Nickel; D007501:Iron
keywords: Corrosion; Metal; Orthodontic brackets