title: Effect of MRI on the mechanical properties of stainless steel orthodontic wires.
abstract: OBJECTIVE
  To assess whether the forces created by the magnetic resonance imaging (MRI) field cause a deflection of orthodontic stainless steel archwires or a change of their mechanical properties.
  
  
  METHODS
  Sixty stainless steel 0.016-inch archwires were divided into three groups of 20 wires each. The control group was as received from the manufacturer, the MRI 1 group had wires attached to brackets on artificial teeth subjected to MRI (1.5 Tesla), and the MRI 2 group had activated T-loops subjected to MRI (1.5 Tesla). The mechanical properties were compared between the control group and MRI 1 group, whereas in the MRI 2 group, the change in the amount of activation was measured. The data were evaluated by repeated measurement analysis with independent and paired t tests.
  
  
  RESULTS
  Tensile strength did not differ significantly between the control group and the MRI 1 group (P=.64). In the MRI 2 group, the mean distance between the vertical loop legs before and after MRI did not differ significantly (P=.53).
  
  
  CONCLUSIONS
  The magnetic field did not significantly affect the mechanical properties of the tested stainless steel wires, nor did it change the loop activation.
authors.affiliation: Department of Orthodontics, School of Dentistry, Shiraz University of Medical Sciences, Shiraz, Iran. morteza_oshagh@yahoo.com
authors.forename: Morteza
authors.initials: M
authors.lastname: Oshagh
authors.forename: Mohammad Rahim
authors.initials: MR
authors.lastname: Hematian
authors.forename: Shoaleh
authors.initials: S
authors.lastname: Shahidi
authors.forename: Negar
authors.initials: N
authors.lastname: Feizi
authors.forename: Farnaz
authors.initials: F
authors.lastname: Bayani
authors.forename: Lida
authors.initials: L
authors.lastname: Pishbin
mesh_terms: D003722:Dental Alloys / Q000737:chemistry*; D006801:Humans; D008279:Magnetic Resonance Imaging; D008422:Materials Testing; D055595:Mechanical Phenomena; D009969:Orthodontic Wires; D013193:Stainless Steel / Q000737:chemistry*; D013314:Stress, Mechanical; D013499:Surface Properties; D013718:Tensile Strength
chemical_list: D003722:Dental Alloys; D013193:Stainless Steel