title: First order couples induced by nickel-titanium archwires featuring an electrochemically refined surface during simulated rotation of teeth.
abstract: OBJECTIVE
  The significance of friction inside the bracket-wire-ligature interface remains controversial despite having been investigated for four decades. Numerous approaches have been proposed to reduce friction via any of the elements of the interface, key among them being recently developed bracket modifications and the introduction of surface-modified wires. The present study explored whether archwires treated by a novel electrochemical process of surface refinement influence first-order couples generated inside self-ligating and conventionally ligated brackets during tooth rotation.
  
  
  METHODS
  A surface-refined nickel-titanium archwire (OptoTherm/LoFrix™) was compared ex vivo to a non-refined archwire of the same production lot (OptoTherm™), the nominal dimensions being 0.014×0.025'' in both cases. Three bracket designs were included to assess the role of the ligation mechanism: (1) Carrière SLB™ passive self-ligating brackets, (2) BioQuick® active self-ligating brackets, and (3) Classic Series® conventionally ligated brackets. The brackets were bonded to leveled tooth elements on a resin mandibular arch. To simulate rotation, the lower left first premolar was removed and connected to a biomechanical measuring system. The simulation procedures were performed at 37°C.
  
  
  RESULTS
  The various bracket designs yielded characteristic torque curves mainly reflecting the play of the archwire specimens inside their slots. While the passive self-ligating brackets exhibited 2-3° of play in either direction, both the active self-ligating brackets and the conventional brackets with elastic ligatures did not reveal any play. Torque levels ranged from 8 Nmm inside the conventional brackets to 13 Nmm inside the passive self-ligating brackets. The surface-refined archwires induced significantly (up to 35%) lower torque levels and were slightly reduced in cross-section.
  
  
  CONCLUSIONS
  Electrochemical surface refinement can significantly reduce first order couples induced by archwires. This effect is caused by less friction, but also by the slightly reduced cross-section of these wires.
authors: Private Practice Dr. Jan Roehlike, Franz-Schubert-Str. 2, 51643, Gummersbach, Germany. leif@johannessen.de
authors: Leif
authors: L
authors: Johannessen
authors: Ludger
authors: L
authors: Keilig
authors: Susanne
authors: S
authors: Reimann
authors: Andreas
authors: A
authors: Jäger
authors: Christoph
authors: C
authors: Bourauel
mesh_terms: D003764:Dental Materials / Q000737:chemistry*; D017267:Dental Prosthesis Design; D004595:Electroplating / Q000379:methods*; D019544:Equipment Failure Analysis; D017276:Friction; D006801:Humans; D008422:Materials Testing; D009532:Nickel / Q000737:chemistry*; D016910:Orthodontic Brackets; D009969:Orthodontic Wires; D012399:Rotation; D013499:Surface Properties; D014025:Titanium / Q000737:chemistry*; D014070:Tooth / Q000737:chemistry*; D019415:Torque
chemical_list: D003764:Dental Materials; C040654:titanium nickelide; D009532:Nickel; D014025:Titanium