title: Frictional resistance exerted by different lingual and labial brackets: an in vitro study.
abstract: BACKGROUND
  Although much has been written on the implications of friction generated between orthodontic archwires and labial brackets, information on lingual brackets is still limited. Hence, we set out to investigate the frictional resistance exerted by different lingual and labial brackets, including both conventional and self-ligating designs. The effect of various factors, namely bracket/base width, slot size, inter-bracket distance, and first- (ΘcI) and second-order (ΘcII) critical contact angles were evaluated and compared.
  
  
  METHODS
  A plaster model of a pretreatment oral cavity was replicated to provide 18 (9 upper and 9 lower) identical versions. The anterior segments of each were taken, and the canine and lateral and central incisors were mounted with either lingual (7th Generation, STb, New STb, In-Ovation L, ORJ) or labial (Mini-Mono, Mini Diamond, G&H Ceramic) brackets. Mechanical friction tests were performed on each type of bracket using a universal testing machine. The maximum force necessary to displace NiTi wires of two different diameters (0.012, 0.014) was measured, using both elastic and metal ligatures with conventional brackets.
  
  
  RESULTS
  The frictional force necessary to displace the wires increased as the diameter of the wire increased in all tested brackets (p<0.01). Friction was significantly higher (p<0.001) with elastic ligatures, as compared with metal ones, in all conventional brackets. In the lower lingual group, significantly lower friction was generated at conventional lingual New STb brackets (p<0.01) and ORJ lingual brackets (p<0.05) than at self-ligating In-Ovation L lingual brackets. A significant statistical correlation between (ΘcI) and friction was detected in the lower labial bracket group.
  
  
  CONCLUSIONS
  Friction resistance is influenced not only by the bracket type, type of ligation, and wire diameter but also by geometric differences in the brackets themselves.
authors: Postgraduate School of Orthodontics, University of Ferrara, Ferrara, Italy. lulombardo@tiscali.it.
authors: Luca
authors: L
authors: Lombardo
authors: Weronika
authors: W
authors: Wierusz
authors: Dominique
authors: D
authors: Toscano
authors: Roberto
authors: R
authors: Lapenta
authors: Andrea
authors: A
authors: Kaplan
authors: Giuseppe
authors: G
authors: Siciliani
mesh_terms: D003722:Dental Alloys / Q000737:chemistry; D003799:Dental Stress Analysis / Q000295:instrumentation; D020724:Elastomers / Q000737:chemistry; D017276:Friction; D006801:Humans; D008422:Materials Testing; D055595:Mechanical Phenomena; D003765:Models, Dental; D009532:Nickel / Q000737:chemistry; D016382:Orthodontic Appliance Design; D016910:Orthodontic Brackets / Q000145:classification*; D009969:Orthodontic Wires; D013314:Stress, Mechanical; D013499:Surface Properties; D014025:Titanium / Q000737:chemistry
chemical_list: D003722:Dental Alloys; D020724:Elastomers; C040654:titanium nickelide; D009532:Nickel; D014025:Titanium