Effects of a diamond-like carbon coating on the frictional properties of orthodontic wires

Takeshi Muguruma, Masahiro Iijima, William A. Brantley, Itaru Mizoguchi

Research output: Contribution to journalArticlepeer-review

52 Citations (Scopus)


Objective: To test the hypothesis that a diamond-like carbon coating does not affect the frictional properties of orthodontic wires. Materials and Methods: Two types of wires (nickel-titanium and stainless steel) were used, and diamond-like carbon (DLC) films were deposited on the wires. Three types of brackets, a conventional stainless steel bracket and two self-ligating brackets, were used for measuring static friction. DLC layers were observed by three-dimensional scanning electron microscopy (3D-SEM), and the surface roughness was measured. Hardness and elastic modulus were obtained by nanoindentation testing. Frictional forces and surface roughness were compared by the Kruskal- Wallis and Mann-Whitney U-tests. The hardness and elastic modulus of the wires were compared using Student's t-test. Results: When angulation was increased, the DLC-coated wires showed significantly less frictional force than the as-received wires, except for some wire/bracket combinations. Thin DLC layers were observed on the wire surfaces by SEM. As-received and DLC-coated wires had similar surface morphologies, and the DLC-coating process did not affect the surface roughness. The hardness of the surface layer of the DLC-coated wires was much higher than for the as-received wires. The elastic modulus of the surface layer of the DLC-coated stainless steel wire was less thanthat of the as-received stainless steel wire, whereas similar values were found for the nickeltitanium wires. Conclusions: The hypothesis is rejected. A DLC-coating process does reduce the frictional force.

Original languageEnglish
Pages (from-to)143-150
Number of pages8
JournalAngle Orthodontist
Issue number1
Publication statusPublished - 2011 Jan


  • Diamond-like carbon coating
  • Frictional properties
  • Nanoindentation test
  • Nickel-titanium
  • Orthodontic wire
  • Stainless steel


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