title: Effect of passive self-ligating bracket placement on the posterior teeth on reduction of frictional force in sliding mechanics.
abstract: OBJECTIVE
  The purpose of this study was to investigate the static (SFF) and kinetic frictional forces (KFF) in sliding mechanics of hybrid bracket systems that involve placing a conventional bracket (CB) or active self-ligating bracket (ASLB) on the maxillary anterior teeth (MXAT) and a passive SLB (PSLB) on the maxillary posterior teeth (MXPT).
  
  
  METHODS
  The samples consisted of two thoroughbred types (group 1, anterior-CB + posterior-CB; group 2, anterior-ASLB + posterior-ASLB) and four hybrid types (group 3, anterior-CB + posterior-PSLB-type 1; group 4, anterior-CB + posterior-PSLB-type 2; group 5, anterior-ASLB + posterior-PSLB-type 1; group 6, anterior-ASLB + posterior-PSLB-type 2) (n = 13 per group). After maxillary dentition alignment and maxillary first premolars removal in the stereolithographically-made typodont system, a 0.019 × 0.025-inch stainless steel wire was drawn through the right quadrant of the maxillary arch at 0.5 mm/min for 5 min. The SFF and KFF were measured with a mechanical testing machine and statistical analyses were performed.
  
  
  RESULTS
  Four different categories of SFF and KFF were observed among all groups (all p < 0.001). Group 1 demonstrated the highest SFF and KFF; groups 4 and 3 were second and third highest, respectively. The fourth category included groups 2, 5, and 6. Placing PSLBs on the MXPT resulted in significant SFF and KFF reductions in cases with CBs on the MXAT, but not in cases with ASLBs on the MXAT.
  
  
  CONCLUSIONS
  These data might aid in the development of a hybrid bracket system that enables low-friction sliding of an archwire through the MXPT.
authors.affiliation: Department of Orthodontics, School of Dentistry, Seoul National University, Seoul, Korea.
authors.forename: Kyu-Ry
authors.initials: KR
authors.lastname: Kim
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; Hybrid bracket system; Self-ligating brackets; Sliding mechanics