title: Effect of bracket bevel design and oral environmental factors on frictional resistance.
abstract: OBJECTIVE
  To investigate the effects of bracket bevel design and oral environmental factors (saliva, temperature) on frictional resistance.
  
  
  METHODS
  Five types of brackets, namely a conventional bracket (Omni-arch), an active self-ligating bracket (Clippy), and three passive self-ligating brackets (Carriere, Damon, and Tenbrook T1) coupled with a 0.014-inch austenitic nickel-titanium archwire were tested. In the experimental model, which used a group of five identical brackets, the center bracket was displaced 3 mm to mimic the binding effects. The friction experiments were performed at three temperatures (20°C, 37°C, 55°C) in a dry or a wet (artificial saliva) state. Finally, the surfaces of the bracket slots were observed using scanning electron microscopy (SEM) before and after the friction tests.
  
  
  RESULTS
  The sliding frictional force was significantly influenced by the bracket slot bevel and saliva whether in the active or passive configuration (P < .05). The frictional force significantly increased as the temperature increased in the active configuration (P < .01). Based on the SEM observations, a correlation was found among the level of frictional force, the bevel angle, and the depth of scratches on bracket bevels.
  
  
  CONCLUSIONS
  Frictional force can be reduced by increasing the bevel angle and by lowering the oral temperature, whereas the presence of saliva increases frictional resistance.
authors.affiliation: a  Attending physician, Department of Stomatology, National Cheng Kung University Hospital, College of Medicine, National Cheng Kung University, Dou-Liou Branch, Yunlin, Taiwan.
authors.forename: Chen-Jung
authors.initials: CJ
authors.lastname: Chang
authors.forename: Tzer-Min
authors.initials: TM
authors.lastname: Lee
authors.forename: Jia-Kuang
authors.initials: JK
authors.lastname: Liu
mesh_terms: D017276:Friction; D008422:Materials Testing / Q000295:instrumentation; D008855:Microscopy, Electron, Scanning; D009532:Nickel; D016382:Orthodontic Appliance Design / Q000379:methods*; D016910:Orthodontic Brackets; D012464:Saliva, Artificial; D013193:Stainless Steel; D013499:Surface Properties; D013696:Temperature; D014025:Titanium
chemical_list: D012464:Saliva, Artificial; C040654:titanium nickelide; D013193:Stainless Steel; D009532:Nickel; D014025:Titanium