title: Evaluation of frictional forces of polycarbonate self-ligating brackets.
abstract: OBJECTIVE
  To evaluate the frictional forces generated by ceramic- (Opal, Ultradent) and glass-fiber-reinforced polycarbonate self-ligating brackets (Oyster, Gestenco) and compare the effectiveness of these ligatureless systems with glass-fiber-reinforced polycarbonate conventional brackets (Blonde, Gestenco). The hypothesis is that there is no difference between frictional forces generated by ceramic- and glass-fiber-reinforced polycarbonate self-ligating and glass-fiber-reinforced polycarbonate conventional brackets.
  
  
  METHODS
  Twelve preadjusted 0.022 3 0.028-inch maxillary canine brackets were tested, divided into three groups: Opal, Oyster, and Blonde. Frictional tests were conducted with the Emic DL 10000 testing machine with a 20 N loadcell for 40 seconds at a 0.5 cm/min speed. Each bracket-wire combination was tested five times. The data generated were analyzed by parametric analysis of variance (one-way ANOVA) and Bonferroni tests.
  
  
  RESULTS
  Analysis of variance indicated significant differences for the three groups (P<.01). The frictional forces of the Oyster glass-fiber-reinforced polycarbonate self-ligating brackets were significantly lower (37.0 ± 8.9 cN) than those of the Opal ceramic-reinforced polycarbonate self-ligating brackets (49.5 ± 10.1 cN), while the Blonde glass-fiber-reinforced conventional bracket frictional forces were 105.8 ± 6.4 cN.
  
  
  CONCLUSIONS
  Oyster glass-fiber-reinforced polycarbonate brackets produced less friction than Opal ceramic-reinforced polycarbonate brackets. The polycarbonate ligatureless system showed significantly lower frictional forces compared to Blonde conventional polycarbonate brackets tied with elastomeric ligatures. The study rejected the initial hypothesis because there are significant differences of frictional forces among the tested systems.
authors.affiliation: Department of Orthodontics, State University of Rio de Janeiro, Rio de Janeiro, Brazil. fernandes.dj@gmail.com
authors.forename: Daniel J
authors.initials: DJ
authors.lastname: Fernandes
authors.forename: José Augusto M
authors.initials: JA
authors.lastname: Miguel
authors.forename: Catia C A
authors.initials: CC
authors.lastname: Quintão
authors.forename: Carlos N
authors.initials: CN
authors.lastname: Elias
mesh_terms: D002516:Ceramics / Q000737:chemistry; D003722:Dental Alloys / Q000737:chemistry; D003799:Dental Stress Analysis / Q000295:instrumentation; D020724:Elastomers / Q000737:chemistry; D017276:Friction; D005898:Glass / Q000737:chemistry; D006801:Humans; D008422:Materials Testing; D016382:Orthodontic Appliance Design; D016910:Orthodontic Brackets; D009969:Orthodontic Wires; D011076:Polycarboxylate Cement / Q000737:chemistry*; D013193:Stainless Steel / Q000737:chemistry; D013314:Stress, Mechanical; D013499:Surface Properties
chemical_list: D003722:Dental Alloys; D020724:Elastomers; D011076:Polycarboxylate Cement; C009753:fiberglass; D013193:Stainless Steel; C005506:polycarbonate