title: Effects of deflection and archwire dimension on the mechanical performance of two self-ligating orthodontic systems.
abstract: OBJECTIVE
  To analyze the effects of archwire deflection and dimension on the mechanical performance of two self-ligating systems, as passive and active ligation designs.
  
  
  METHODS
  An experimental model was used that was designed to resemble the full dental arch and to allow vertical displacement of a canine element. Two self-ligating systems were investigated: 1) a passive system; and 2) an active system, both in combination with three thermoactive NiTi archwires, with round sections of 0.014-in, 0.016-in and 0.018-in. The full loading-unloading cycles consisted of either 3mm or 6mm maximum deflection, performed at 37 °C. During unloading, the deactivation forces and energy were recorded. The ratio between the deactivation and activation energies was used as representative of the mechanical efficiencies of the systems.
  
  
  RESULTS
  The deactivation force increased in combination with larger archwires and greater deflection. The deactivation energy increased in combination with larger archwires only for the 3-mm deflection cycle, while for the 6-mm deflection cycle, the deactivation energy was not influenced by the archwire dimension, and was not greater than that of the 3-mm deflection cycle. The mechanical efficiency decreased in combination with greater deflection and larger archwires, with a maximum decrease of about 12%. Only minor comparative differences were seen between the systems.
  
  
  CONCLUSIONS
  The deflection degree and archwire dimension have large effects on the mechanical performance of self-ligating systems.
authors.affiliation: School of Dentistry, Department of Biomedicine, University of Trieste, Italy. L.Contardo@fmc.units.it
authors.forename: Luca
authors.initials: L
authors.lastname: Contardo
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Perinetti
authors.forename: Michele
authors.initials: M
authors.lastname: Ceschi
authors.forename: Gabriele
authors.initials: G
authors.lastname: Vidoni
authors.forename: Francesca
authors.initials: F
authors.lastname: Antoniolli
authors.forename: Attilio
authors.initials: A
authors.lastname: Castaldo
authors.forename: Roberto
authors.initials: R
authors.lastname: Di Lenarda
mesh_terms: D001641:Bicuspid / Q000033:anatomy & histology; D001696:Biomechanical Phenomena; D003481:Cuspid / Q000033:anatomy & histology; D003722:Dental Alloys / Q000737:chemistry; D003724:Dental Arch / Q000033:anatomy & histology; D003799:Dental Stress Analysis / Q000295:instrumentation; D006801:Humans; D007180:Incisor / Q000033:anatomy & histology; D008422:Materials Testing; D055595:Mechanical Phenomena; D009532:Nickel / Q000737:chemistry; D016382:Orthodontic Appliance Design; D016910:Orthodontic Brackets; D009969:Orthodontic Wires; D013314:Stress, Mechanical; D013499:Surface Properties; D013696:Temperature; D013816:Thermodynamics; D014025:Titanium / Q000737:chemistry
chemical_list: D003722:Dental Alloys; C040654:titanium nickelide; D009532:Nickel; D014025:Titanium