title: Comparisons of nanoindentation, 3-point bending, and tension tests for orthodontic wires.
abstract: BACKGROUND
  The purposes of this study were to obtain information about mechanical properties with the nanoindentation test for representative wire alloys and compare the results with conventional mechanical tests.
  
  
  METHODS
  Archwires having 0.016 × 0.022-in cross sections were obtained of 1 stainless steel, 1 cobalt-chromium-nickel, 1 beta-titanium alloy, and 2 nickel-titanium products. Specimens of as-received wires were subjected to nanoindentation testing along the external surfaces and over polished cross sections to obtain values of hardness and elastic modulus. Other specimens of as-received wires were subjected to Vickers hardness, 3-point bending, and tension tests. All testing was performed at 25°C.
  
  
  RESULTS
  Differences were found in hardness and elastic modulus obtained with the nanoindentation test at the external and cross-sectioned surfaces and with the conventional mechanical-property tests. Mechanical properties obtained with the nanoindentation test generally varied with indentation depth.
  
  
  CONCLUSIONS
  The 3 testing methods did not yield identical values of hardness and elastic modulus, although the order among the 5 wire products was the same. Variations in results for the nanoindentation and conventional mechanical property tests can be attributed to the different material volumes sampled, different work-hardening levels, and an oxide layer on the wire surface.
authors: Division of Orthodontics and Dentofacial Orthopedics, Department of Oral Growth and Development, School of Dentistry, Health Sciences University of Hokkaido, Ishikari-Tobetsu, Japan. iijima@hoku-iryo-u.ac.jp
authors: Masahiro
authors: M
authors: Iijima
authors: Takeshi
authors: T
authors: Muguruma
authors: William A
authors: WA
authors: Brantley
authors: Itaru
authors: I
authors: Mizoguchi
mesh_terms: D002857:Chromium; D002858:Chromium Alloys; D003722:Dental Alloys; D003799:Dental Stress Analysis / Q000379:methods*; D055119:Elastic Modulus; D006244:Hardness; D008422:Materials Testing / Q000379:methods; D009532:Nickel; D009969:Orthodontic Wires; D018583:Pliability; D013193:Stainless Steel; D013718:Tensile Strength; D014025:Titanium
chemical_list: D002858:Chromium Alloys; D003722:Dental Alloys; C023988:beta titanium; D002857:Chromium; C040654:titanium nickelide; D013193:Stainless Steel; D009532:Nickel; D014025:Titanium