title: Effects of third-order torque on frictional force of self-ligating brackets.
abstract: OBJECTIVE
  To investigate the effects of third-order torque on frictional properties of self-ligating brackets (SLBs).
  
  
  METHODS
  Three SLBs (two passive and one active) and three archwires (0.016 × 0.022-inch nickel-titanium, and 0.017 × 0.025-inch and 0.019 × 0.025-inch stainless steel) were used. Static friction was measured by drawing archwires though bracket slots with four torque levels (0°, 10°, 20°, 30°), using a mechanical testing machine (n  =  10). A conventional stainless-steel bracket was used for comparison. RESULTS were subjected to Kruskal-Wallis and Mann-Whitney U-tests. Contact between the bracket and wire was studied using a scanning electron microscope.
  
  
  RESULTS
  In most bracket-wire combinations, increasing the torque produced a significant increase in static friction. Most SLB-wire combinations at all torques produced less friction than that from the conventional bracket. Active-type SLB-wire combinations showed higher friction than that from passive-type SLB-wire combinations in most conditions. When increasing the torque, more contact between the wall of a bracket slot and the edge of a wire was observed for all bracket types.
  
  
  CONCLUSIONS
  Increasing torque when using SLBs causes an increase in friction, since contact between the bracket slot wall and the wire edge becomes greater; the design of brackets influences static friction.
authors.affiliation: a  Instructor, Division of Orthodontics and Dentofacial Orthopedics, Department of Oral Growth and Development, School of Dentistry, Health Sciences University of Hokkaido, Hokkaido, Japan.
authors.forename: Takeshi
authors.initials: T
authors.lastname: Muguruma
authors.forename: Masahiro
authors.initials: M
authors.lastname: Iijima
authors.forename: William A
authors.initials: WA
authors.lastname: Brantley
authors.forename: Karamdeep S
authors.initials: KS
authors.lastname: Ahluwalia
authors.forename: Naohisa
authors.initials: N
authors.lastname: Kohda
authors.forename: Itaru
authors.initials: I
authors.lastname: Mizoguchi
mesh_terms: D000497:Alloys / Q000737:chemistry; D003722:Dental Alloys / Q000737:chemistry; D003799:Dental Stress Analysis / Q000295:instrumentation; D017276:Friction; D006801:Humans; D008422:Materials Testing; D008855:Microscopy, Electron, Scanning; D009532:Nickel / Q000737:chemistry; D016382:Orthodontic Appliance Design; D016910:Orthodontic Brackets; D009969:Orthodontic Wires; D013193:Stainless Steel / Q000737:chemistry; D013314:Stress, Mechanical; D013499:Surface Properties; D014025:Titanium / Q000737:chemistry; D019415:Torque
chemical_list: D000497:Alloys; D003722:Dental Alloys; C040654:titanium nickelide; D013193:Stainless Steel; C013616:nitinol; D009532:Nickel; D014025:Titanium
keywords: Archwire; Friction; SEM; Self-ligating brackets
references.citation: Am J Orthod Dentofacial Orthop. 2013 Jan;143(1):10-8, 11-9
references.pmid: 23273355
references.citation: Am J Orthod Dentofacial Orthop. 2003 Oct;124(4):395-402
references.pmid: 14560269
references.citation: Angle Orthod. 2011 Jan;81(1):141-48
references.pmid: 20936967
references.citation: Am J Orthod Dentofacial Orthop. 2003 Jul;124(1):69-73
references.pmid: 12867900
references.citation: Angle Orthod. 2009 May;79(3):551-7
references.pmid: 19413378
references.citation: Dent Mater. 2005 Oct;21(10):938-45
references.pmid: 15923033
references.citation: Eur J Orthod. 2012 Oct;34(5):625-32
references.pmid: 21765175
references.citation: Angle Orthod. 2006 May;76(3):480-5
references.pmid: 16637731
references.citation: Am J Orthod Dentofacial Orthop. 2007 Aug;132(2):216-22
references.pmid: 17693372
references.citation: Am J Orthod Dentofacial Orthop. 2013 Jan;143(1):11-9
references.pmid: 23273356
references.citation: J Orthod. 2003 Sep;30(3):262-73
references.pmid: 14530427
references.citation: Am J Orthod Dentofacial Orthop. 1994 Jul;106(1):76-87
references.pmid: 8017353
references.citation: Am J Orthod Dentofacial Orthop. 1997 Aug;112(2):138-44
references.pmid: 9267224
references.citation: Am J Orthod Dentofacial Orthop. 2002 Sep;122(3):295-305
references.pmid: 12226612
references.citation: Dent Mater. 1992 May;8(3):167-72
references.pmid: 1521704
references.citation: Am J Orthod Dentofacial Orthop. 2009 Apr;135(4):442-7
references.pmid: 19361729
references.citation: Am J Orthod. 1980 Dec;78(6):593-609
references.pmid: 6935961
references.citation: Korean J Orthod. 2012 Aug;42(4):218-24
references.pmid: 23112953