title: Corrosion resistance of surface modified nickel titanium archwires.
abstract: OBJECTIVE
  To compare the corrosion behavior of commercially available surface modified nickel titanium (NiTi) arch wires with respect to a conventional NiTi and to evaluate its association with surface characteristics.
  
  
  METHODS
  Five types of surface modified arch wires and a conventional NiTi arch wire, all from different manufacturers, were evaluated for their corrosion resistance from breakdown potential in an anodic polarization scan in Ringer's solution. Surface characteristics were determined from scanning electron microscopy, atomic force microscopy, and energy dispersive analysis. One-way analysis of variance and post hoc Duncan's multiple range tests were used to evaluate statistical significance.
  
  
  RESULTS
  Surface modified NiTi wires showed significant improvement in corrosion resistance and reduction in surface roughness values. Breakdown potentials increased in the order of group 6 (conventional; 204 mV) < group 1 (nitride; 333 mV) < group 5 (epoxy resin; 346mV) < group 3 (oxide; 523 mV) < group 2 (gold; 872 mV) < group 4 (Teflon; 1181 mV), but root mean square (RMS) roughness values, which indicated surface roughness, followed a different pattern: group 3 (oxide; 74.12 nm) < group 1 (nitride; 221.651 nm) < group 4 (Teflon; 278.523 nm) < group 2 (gold; 317.894 nm) < group 5 (epoxy resin; 344.236 nm) < group 6 (conventional; 578.555 nm).
  
  
  CONCLUSIONS
  Surface modification of NiTi wires proved to be effective in improving its corrosion resistance and decreasing surface roughness. However, neither factor could maintain a direct, one-to-one relationship. It meant that the type and nature of coating material can effectively influence the anticorrosive features of NiTi wires, compared with its surface roughness values.
authors.affiliation: a  Head of the Department and Classified Specialist in Orthodontics, Department of Dental Research & Implantology, Institute of Nuclear Medicine & Allied Sciences, Defence Research & Development Organization, Delhi, India.
authors.forename: Manu
authors.initials: M
authors.lastname: Krishnan
authors.forename: Saraswathy
authors.initials: S
authors.lastname: Seema
authors.forename: A Vinod
authors.initials: AV
authors.lastname: Kumar
authors.forename: N Parvatha
authors.initials: NP
authors.lastname: Varthini
authors.forename: Kalathil
authors.initials: K
authors.lastname: Sukumaran
authors.forename: Vasant R
authors.initials: VR
authors.lastname: Pawar
authors.forename: Vimal
authors.initials: V
authors.lastname: Arora
mesh_terms: D020099:Coated Materials, Biocompatible / Q000737:chemistry*; D003343:Corrosion; D003722:Dental Alloys / Q000737:chemistry*; D055664:Electrochemical Techniques; D004853:Epoxy Resins / Q000737:chemistry; D006047:Gold Alloys / Q000737:chemistry; D006801:Humans; D021621:Imaging, Three-Dimensional; D007552:Isotonic Solutions / Q000737:chemistry; D008422:Materials Testing; D018625:Microscopy, Atomic Force; D008855:Microscopy, Electron, Scanning; D009532:Nickel / Q000737:chemistry*; D009584:Nitrogen / Q000737:chemistry; D016382:Orthodontic Appliance Design; D009969:Orthodontic Wires; D010087:Oxides / Q000737:chemistry; D011138:Polytetrafluoroethylene / Q000737:chemistry; D000077331:Ringer's Solution; D013052:Spectrometry, X-Ray Emission; D013499:Surface Properties; D014025:Titanium / Q000737:chemistry*
chemical_list: D020099:Coated Materials, Biocompatible; D003722:Dental Alloys; D004853:Epoxy Resins; D006047:Gold Alloys; D007552:Isotonic Solutions; D010087:Oxides; C040654:titanium nickelide; D009532:Nickel; D000077331:Ringer's Solution; D011138:Polytetrafluoroethylene; D014025:Titanium; D009584:Nitrogen