title: In vitro evaluation of frictional forces of two ceramic orthodontic brackets versus a stainless steel bracket in combination with two types of archwires.
abstract: OBJECTIVE
  The aim of this study was to compare frictional forces between monocrystalline alumina (MA), polycrystalline alumina (PA), and stainless steel (SS) brackets with two SS wires: Rectangular and round.
  
  
  METHODS
  In this in vitro study, 60 0.022 brackets [20 PA (0° torque, Forestadent, Germany) and 20 MA (0° torque, Ormco, California, USA)] brackets plus 20 SS brackets (0° torque, Foretadent, Germany) and 60 SS archwires (30 rectangular 0.019 ×0.025 archwires and 30 round 0.018 archwires, Ortho Technology, USA) were used in subgroups of 10 from the combination of all brackets and all archwires. A universal testing machine (Instron, Model STM 250, Germany) was used to investigate the static frictional resistance. The angulation between the bracket and wire was 0°, and the wires were pulled through the slots at a crosshead speed of 10 mm/min. Two-way and one-way analyses of variance (ANOVA) and Tukey tests were used to analyze the data.
  
  
  RESULTS
  Mean (SD) static frictional force for each group was as follows: MA + round: 3.47 (0.38); MA + rectangular: 4.05 (0.47); PA + round: 4.14 (0.37); PA + rectangular: 4.45 (0.65); SS + round: 3.28 (0.22); and SS + rectangular: 4.22 (0.61). Significant effects of bracket types (P = 0.001) and archwire types (P = 0.000) on the friction force were detected using ANOVA. Tukey test indicated significant differences between PA brackets with both SS and MA brackets (P < 0.05), but not between SS and MA brackets. The two archwires as well had significantly different effects (Tukey P = 0.000).
  
  
  CONCLUSIONS
  Based on the present in-vitro study, the PA brackets might create higher frictional forces compared to both SS and MA brackets. The rectangular 0.019 ×0.025 archwire might create greater forces than round 0.018 archwire.
authors.affiliation: Dental Material Research Center, School of Dentistry, Babol University of Medical Sciences, Babol, Iran.
authors.forename: Valiollah
authors.initials: V
authors.lastname: Arash
authors.affiliation: Department of Mechanics, Babol University of Noushirvani, Babol, Iran.
authors.forename: Mahmoud
authors.initials: M
authors.lastname: Rabiee
authors.affiliation: Iranian Tissue Bank and Research Center, Tehran University of Medical Sciences, Tehran, Iran ; Department of Dental Anatomy and Morphology, Islamic Azad University, Tehran, Iran.
authors.forename: Vahid
authors.initials: V
authors.lastname: Rakhshan
authors.affiliation: Dental Material Research Center, School of Dentistry, Babol University of Medical Sciences, Babol, Iran.
authors.forename: Sara
authors.initials: S
authors.lastname: Khorasani
authors.affiliation: Department of Orthodontics, School of Dentistry, Mazandaran University of Medical Sciences, Sari, Iran.
authors.forename: Farhad
authors.initials: F
authors.lastname: Sobouti
keywords: Artificial saliva; ceramic bracket; rectangular arch wire; round arch wire; stainless steel bracket; static friction