title: Force-deflection characteristics of the fatigue-resistant device spring: an in vitro study.
abstract: OBJECTIVE
  The Forsus fatigue-resistant device spring is a 3-piece telescoping compression spring used for Class II correction. The aims of this study were: (1) to measure the mean force delivered at different amounts of deflection; (2) to determine and compare the mean stiffness between loading and unloading; and (3) to determine the resilience of the fatigue-resistant device springs.
  
  
  METHODS
  Twelve fatigue-resistant device springs were tested with a universal testing machine and Winrcon software, with the load cell of 100 N, crosshead speed at 0.5 mm/second. Force-deflection data during loading and unloading were recorded at 2-mm intervals up to 12 mm compression.
  
  
  RESULTS
  (1) The mean force-deflection loading and unloading curves generally were linear, with a small area of hysteresis; (2) the loading mean stiffness (19.4 g/mm) was significantly greater than the unloading mean stiffness (18 g/mm), although this is clinically insignificant; (3) fatigue-resistant device springs exhibited good resiliency. A calibrated table of force-deflection of fatigue-resistant device springs is presented for clinicians to select the appropriate length of the device for the particular orthodontic force needed.
authors: Faculty of Dentistry, Garyounis University, Abdul Monem Riad, Benghazi, Libya.
authors: Moaaz Mohamed
authors: MM
authors: El-Sheikh
authors: Keith
authors: K
authors: Godfrey
authors: Montein
authors: M
authors: Manosudprasit
authors: Nita
authors: N
authors: Viwattanatipa
mesh_terms: D003722:Dental Alloys / Q000737:chemistry; D003799:Dental Stress Analysis / Q000295:instrumentation; D004548:Elasticity; D006801:Humans; D008422:Materials Testing; D016382:Orthodontic Appliance Design; D009967:Orthodontic Appliances; D009969:Orthodontic Wires; D013232:Steel / Q000737:chemistry; D013314:Stress, Mechanical; D014087:Tooth Movement Techniques / Q000295:instrumentation*
chemical_list: D003722:Dental Alloys; D013232:Steel