title: Frictional resistance of self-ligating versus conventional brackets in different bracket-archwire-angle combinations.
abstract: OBJECTIVE
  To compare the influence of archwire material (NiTi, beta-Ti and stainless steel) and brackets design (self-ligating and conventional) on the frictional force resistance.
  
  
  METHODS
  Two types of brackets (self-ligating brackets - Smartclip, 3M/Unitek - and conventional brackets - Gemini, 3M/Unitek) with three (0, 5, and 10 degrees) slot angulation attached with elastomeric ligatures (TP Orthodontics) were tested. All brackets were tested with archwire 0.019"x0.025" nickel-titanium, beta-titanium, and stainless steel (Unitek/3M). The mechanical testing was performed with a universal testing machine eMIC DL 10000 (eMIC Co, Brazil). The wires were pulled from the bracket slots at a cross-head speed of 3 mm/min until 2 mm displacement.
  
  
  RESULTS
  Self-ligating brackets produced significantly lower friction values compared with those of conventional brackets. Frictional force resistance values were directly proportional to the increase in the bracket/ wire angulation. With regard to conventional brackets, stainless steel wires had the lowest friction force values, followed by nickel-titanium and beta-titanium ones. With regard to self-ligating brackets, the nickel-titanium wires had the lowest friction values, significantly lower than those of other materials.
  
  
  CONCLUSIONS
  even at different angulations, the self-ligating brackets showed significantly lower friction force values than the conventional brackets. Combined with nickel-titanium wires, the self-ligating brackets exhibit much lower friction, possibly due to the contact between nickel-titanium clips and wires of the same material.
authors.affiliation: Department of Orthodontics, Fluminense Federal University, RJ, Brazil.
authors.forename: Maria Regina Guerra
authors.initials: MR
authors.lastname: Monteiro
authors.affiliation: Department of Statistics, Fluminense Federal University, Niterói, RJ, Brazil.
authors.forename: Licinio Esmeraldo da
authors.initials: LE
authors.lastname: Silva
authors.affiliation: Materials Science Department, Military Engineering Institute, Rio de Janeiro, Brazil.
authors.forename: Carlos Nelson
authors.initials: CN
authors.lastname: Elias
authors.affiliation: Department of Orthodontics, Fluminense Federal University, Niterói, RJ, Brazil.
authors.forename: Oswaldo de Vasconcellos
authors.initials: Ode V
authors.lastname: Vilella
mesh_terms: D003722:Dental Alloys / Q000737:chemistry; D017276:Friction; D008422:Materials Testing; D009532:Nickel / Q000737:chemistry*; D016382:Orthodontic Appliance Design; D016910:Orthodontic Brackets; D009969:Orthodontic Wires; D012016:Reference Values; D013193:Stainless Steel / Q000737:chemistry*; D013499:Surface Properties; D014025:Titanium / Q000737:chemistry*
chemical_list: D003722:Dental Alloys; C023988:beta titanium; C040654:titanium nickelide; D013193:Stainless Steel; D009532:Nickel; D014025:Titanium