title: Load deflection characteristics and force level of nickel titanium initial archwires.
abstract: OBJECTIVE
  To investigate and compare the characteristics of commonly used types of traditional and heat-activated initial archwire by plotting their load/deflection graphs and quantifying three suitable parameters describing the discharge plateau phase.
  
  
  METHODS
  Forty-eight archwires (22 nickel titanium [NiTi] and 26 heat-activated) of cross-sectional diameter ranging from 0.010 to 0.016 inch were obtained from seven different manufacturers. A modified three-point wire-bending test was performed on three analogous samples of each type of archwire at a constant temperature (37.0°C). For each resulting load/deflection curve, the plateau section was isolated, along with the mean value of the average plateau force, the plateau length, and the plateau slope for each type of wire obtained.
  
  
  RESULTS
  Statistically significant differences were found between almost all wires for the three parameters considered. Statistically significant differences were also found between traditional and heat-activated archwires, the latter of which generated longer plateaus and lighter average forces. The increase in average force seen with increasing diameter tended to be rather stable, although some differences were noted between traditional and heat-activated wires.
  
  
  CONCLUSIONS
  Although great variation was seen in the plateau behavior, heat-activated versions appear to generate lighter forces over greater deflection plateaus. On average, the increase in plateau force was roughly 50% when the diameter was increased by 0.002 inch (from 0.012 to 0.014 and from 0.014 to 0.016 inch) and about 150% when the diameter was increased by 0.004 inch (from 0.012 to 0.016), with differences between traditional and heat-activated wires noted in this case.
authors.affiliation: Department of Orthodontics, University of Ferrara, Ferrara, Italy. lulombardo@tiscali.it
authors.forename: Luca
authors.initials: L
authors.lastname: Lombardo
authors.forename: Matteo
authors.initials: M
authors.lastname: Marafioti
authors.forename: Filippo
authors.initials: F
authors.lastname: Stefanoni
authors.forename: Francesco
authors.initials: F
authors.lastname: Mollica
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Siciliani
mesh_terms: D000704:Analysis of Variance; D003722:Dental Alloys; D003799:Dental Stress Analysis; D004548:Elasticity; D006358:Hot Temperature; D008422:Materials Testing; D009532:Nickel; D016382:Orthodontic Appliance Design; D009969:Orthodontic Wires; D014025:Titanium
chemical_list: D003722:Dental Alloys; C040654:titanium nickelide; D009532:Nickel; D014025:Titanium