title: Debris and friction of self-ligating and conventional orthodontic brackets after clinical use.
abstract: OBJECTIVE
  To compare the degree of debris and friction of conventional and self-ligating orthodontic brackets before and after clinical use.
  
  
  METHODS
  Two sets of three conventional and self-ligating brackets were bonded from the first molar to the first premolar in eight individuals, for a total of 16 sets per type of brackets. A passive segment of 0.019 × 0.025-inch stainless steel archwire was inserted into each group of brackets. Frictional force and debris level were evaluated as received and after 8 weeks of intraoral exposure. Two-way analysis of variance and Wilcoxon signed-rank test were applied at P < .05.
  
  
  RESULTS
  After the intraoral exposure, there was a significant increase of debris accumulation in both systems of brackets (P < .05). However, the self-ligating brackets showed a higher amount of debris compared with the conventional brackets. The frictional force in conventional brackets was significantly higher when compared with self-ligating brackets before clinical use (P < .001). Clinical exposure for 8 weeks provided a significant increase of friction (P < .001) on both systems. In the self-ligating system, the mean of friction increase was 0.21 N (191%), while 0.52 N (47.2%) was observed for the conventional system.
  
  
  CONCLUSIONS
  Self-ligating and conventional brackets, when exposed to the intraoral environment, showed a significant increase in frictional force during the sliding mechanics. Debris accumulation was higher for the self-ligating system.
authors.affiliation: a  Resident, Department of Orthodontics, Brazilian Association of Dentistry, Belém, Pará, Brazil.
authors.forename: Raíssa Costa
authors.initials: RC
authors.lastname: Araújo
authors.affiliation: b  Graduate student, Department of Orthodontics, School of Dentistry, Federal University of Pará, Belém, Pará, Brazil.
authors.forename: Lívia Monteiro
authors.initials: LM
authors.lastname: Bichara
authors.affiliation: b  Graduate student, Department of Orthodontics, School of Dentistry, Federal University of Pará, Belém, Pará, Brazil.
authors.forename: Adriana Monteiro de
authors.initials: AM
authors.lastname: Araujo
authors.affiliation: c  Associate Professor, Department of Orthodontics, School of Dentistry, Federal University of Pará, Belém, Pará, Brazil.
authors.forename: David
authors.initials: D
authors.lastname: Normando
mesh_terms: D000328:Adult; D003722:Dental Alloys / Q000737:chemistry; D005260:Female; D017276:Friction; D006801:Humans; D008297:Male; D016910:Orthodontic Brackets / Q000145:classification*; D009969:Orthodontic Wires; D013193:Stainless Steel / Q000737:chemistry; D013314:Stress, Mechanical; D013499:Surface Properties; D013997:Time Factors
chemical_list: D003722:Dental Alloys; D013193:Stainless Steel
keywords: Friction; Orthodontic brackets; Self-ligating brackets