title: Comparison of static friction with self-ligating, modified slot design and conventional brackets.
abstract: OBJECTIVE
  To compare the static frictional forces generated at the bracket/wire interface of stainless steel brackets with different geometries and angulations, combined with orthodontic wires of different diameters.
  
  
  METHODS
  The frictional forces were evaluated with three different types of metal brackets: a passive self-ligating (SmartClipTM, 3M/Unitek, Monrovia, USA), with a modified slot design (Mini Uni TwinTM, 3M/Unitek, Monrovia, USA) and conventional (Kirium, Abzil, São José do Rio Preto, Brazil). The samples were mounted in a testing device with three different angulations and tested with 0.014" and 0.018" stainless steel wires (American Orthodontics, Sheboygan, USA). The static frictional force was measured using a universal testing machine (DL 500, EMIC®, São José dos Pinhais, Brazil) with a crosshead speed of 1 mm/min. Statistical analysis was performed by two-way ANOVA followed by Bonferroni's post hoc test.
  
  
  RESULTS
  There was a significant difference (p<0.05) in static friction when the three types of brackets were tested with the same wire size. The wire diameter influenced friction only when the brackets had a 10º angulation (p<0.05). The angulation influenced friction (p<0.05) when the brackets were associated with a 0.018" wire.
  
  
  CONCLUSIONS
  Brackets with a modified slot design showed intermediate static frictional force values between the conventional and self-ligating brackets tested.
authors.affiliation: Pontifical Catholic University of Minas Gerais, Belo HorizonteMG, Brazil.
authors.forename: Raquel Morais
authors.initials: RM
authors.lastname: Castro
authors.forename: Perrin Smith
authors.initials: PS
authors.lastname: Neto
authors.forename: Martinho Campolina Rebello
authors.initials: MC
authors.lastname: Horta
authors.forename: Matheus Melo
authors.initials: MM
authors.lastname: Pithon
authors.forename: Dauro Douglas
authors.initials: DD
authors.lastname: Oliveira
mesh_terms: D000704:Analysis of Variance; D017276:Friction; D008422:Materials Testing; D016382:Orthodontic Appliance Design / Q000379:methods*; D016910:Orthodontic Brackets; D009969:Orthodontic Wires; D012016:Reference Values; D013193:Stainless Steel / Q000737:chemistry; D013499:Surface Properties
chemical_list: D013193:Stainless Steel
references.citation: Am J Orthod Dentofacial Orthop. 2009 Apr;135(4):442-7
references.pmid: 19361729
references.citation: Am J Orthod Dentofacial Orthop. 1994 Nov;106(5):472-80
references.pmid: 7977187
references.citation: Am J Orthod Dentofacial Orthop. 2003 Oct;124(4):395-402
references.pmid: 14560269
references.citation: Am J Orthod Dentofacial Orthop. 2011 Jan;139(1):37-43
references.pmid: 21195274
references.citation: Eur J Orthod. 2012 Oct;34(5):625-32
references.pmid: 21765175
references.citation: World J Orthod. 2009 Fall;10(3):220-3
references.pmid: 19885424
references.citation: Am J Orthod Dentofacial Orthop. 2003 Apr;123(4):416-22
references.pmid: 12695769
references.citation: J Clin Orthod. 2007 Aug;41(8):451-7
references.pmid: 17921596
references.citation: J Appl Oral Sci. 2011 Jan-Feb;19(1):57-62
references.pmid: 21437471
references.citation: Angle Orthod. 2010 May;80(3):575-84
references.pmid: 20050755
references.citation: Am J Orthod Dentofacial Orthop. 2004 Feb;125(2):17A; author reply 17A
references.pmid: 14989274
references.citation: Am J Orthod Dentofacial Orthop. 2009 Nov;136(5):675-82
references.pmid: 19892284
references.citation: Eur J Orthod. 2008 Dec;30(6):645-53
references.pmid: 18974067
references.citation: Am J Orthod Dentofacial Orthop. 2008 Jan;133(1):87-90
references.pmid: 18174077
references.citation: Angle Orthod. 2010 May;80(3):521-7
references.pmid: 20050747
references.citation: Am J Orthod Dentofacial Orthop. 2001 Oct;120(4):361-70
references.pmid: 11606960
references.citation: J Clin Orthod. 1996 Jun;30(6):325-30
references.pmid: 10356524