title: Frictional property comparisons of conventional and self-ligating lingual brackets according to tooth displacement during initial leveling and alignment: an in vitro mechanical study.
abstract: OBJECTIVE
  We evaluated the effects of tooth displacement on frictional force when conventional ligating lingual brackets (CL-LBs), CL-LBs with a narrow bracket width, and self-ligating lingual brackets (SL-LBs) were used with initial leveling and alignment wires.
  
  
  METHODS
  CL-LBs (7th Generation), CL-LBs with a narrow bracket width (STb), and SL-LBs (In-Ovation L) were tested under three tooth displacement conditions: no displacement (control); a 2-mm palatal displacement (PD) of the maxillary right lateral incisor (MXLI); and a 2-mm gingival displacement (GD) of the maxillary right canine (MXC) (nine groups, n = 7 per group). A stereolithographic typodont system and artificial saliva were used. Static and kinetic frictional forces (SFF and KFF, respectively) were measured while drawing a 0.013-inch copper-nickel-titanium archwire through brackets at 0.5 mm/min for 5 minutes at 36.5℃.
  
  
  RESULTS
  The In-Ovation L exhibited lower SFF under control conditions and lower KFF under all displacement conditions than the 7th Generation and STb (all p < 0.001). No significant difference in SFF existed between the In-Ovation L and STb for a 2-mm GD of the MXC and 2-mm PD of the MXLI. A 2-mm GD of the MXC produced higher SFF and KFF than a 2-mm PD of the MXLI in all brackets (all p < 0.001).
  
  
  CONCLUSIONS
  CL-LBs with narrow bracket widths exhibited higher KFF than SL-LBs under tooth displacement conditions. CL-LBs and ligation methods should be developed to produce SFF and KFF as low as those in SL-LBs during the initial and leveling stage.
authors.affiliation: Department of Orthodontics, School of Dentistry, Seoul National University, Seoul, Korea.
authors.forename: Do-Yoon
authors.initials: DY
authors.lastname: Kim
authors.affiliation: Department of Biomaterials Science, School of Dentistry, Seoul National University, Seoul, Korea.
authors.forename: Bum-Soon
authors.initials: BS
authors.lastname: Lim
authors.affiliation: Department of Orthodontics, School of Dentistry, Seoul National University, Seoul, Korea.; Dental Research Institute, Seoul National University, Seoul, Korea.
authors.forename: Seung-Hak
authors.initials: SH
authors.lastname: Baek
keywords: Frictional force; Initial leveling and alignment; Lingual bracket; Tooth displacement