title: Fluoride influences nickel-titanium orthodontic wires' surface texture and friction resistance.
abstract: OBJECTIVE
  The aim of this study was to investigate the effects exerted by the acidulated fluoride gel on stainless steel and nickel-titanium (Ni-Ti) orthodontic wires.
  
  
  METHODS
  Sixty stainless steel and Ni-Ti orthodontic archwires were distributed into forty archwires used forin vitrostudy and twenty forin situstudy. Fluoride was applied for 1 h in thein vitroexperiment while it was applied for 5 min in thein situexperiment. The friction resistance of all wires with ceramic brackets before/after topical fluoride application was measured using a universal testing machine at 1 min intervals of moving wire. Moreover, surface properties of the tested wires before/after fluoride application and before/after friction test were examined by a scanning electron microscope (SEM). Dunnett'st-test was used to compare frictional resistance of as-received stainless steel wires and Ni-Ti wires to the wires treated by fluoridein vitroandin situ(P< 0.05). Two-way ANOVA was used to compare the effect of fluoride application and type of wire on friction resistancein vitroandin situ(P< 0.05).
  
  
  RESULTS
  Ni-Ti wires recorded significantly high friction resistance after fluoride application when compared to stainless steel wiresin vitro,P< 0.05. Fluoride application did not significantly affect the friction resistance of the tested wiresin situ,P< 0.05. SEM observation revealed deterioration of the surface texture of the Ni-Ti wires after fluoride applicationin vitroandin situ.
  
  
  CONCLUSIONS
  Thein vitrofluoride application caused an increase in friction resistance of Ni-Ti wires when compared to stainless steel wires.In vitroandin situfluoride application caused deterioration in surface properties of Ni-Ti wires.
authors.affiliation: Department of Orthodontics, Faculty of Dentistry, King Abdulaziz University, Jeddah 21381, Saudi Arabia; Alexandria University, Alexandria, Egypt.
authors.forename: Mona Aly
authors.initials: MA
authors.lastname: Abbassy
keywords: Fluoride; friction resistance; orthodontics; prophylaxis; surfaces