title: Holographic analysis of the initial canine displacement produced by four different retraction springs.
abstract: OBJECTIVE
  To estimate and compare the magnitude and direction of initial displacement of the canine produced by four different canine retraction springs.
  
  
  METHODS
  A freshly macerated mandible was used as an experimental model. First premolars were extracted, and strap-up was done with a 0.018 inch Roth Preadjusted Edgewise System (3M Unitek, Monrovia, Calif). The canine was subjected to loads of 4 oz, 5 oz, and 6 oz, each applied by four different canine retraction springs, that is, closed coil spring, open coil spring, PG spring, and T-loop retraction spring. The magnitude and direction of the initial displacement of the canine were studied by means of double-exposure interferometry.
  
  
  RESULTS
  The PG spring produced the highest initial displacement for a given force among the force systems used, followed by open coil, closed coil, and T-loop. Maximum tipping was observed with the open coil spring, followed by the PG spring, the closed coil spring, and the T-spring.
  
  
  CONCLUSIONS
  The T-loop may be preferred whenever minimal tipping is performed. The PG spring may be preferred over other springs whenever a higher magnitude of displacement is desired. Closed coil springs may be preferred whenever a reasonable magnitude of displacement is required and reasonable tipping is allowed.
authors.affiliation: Department of Orthodontics, KVG Dental College and Hospital, Sullia, India. ymahesh2000@yahoo.com
authors.forename: Y Mahesh
authors.initials: YM
authors.lastname: Kumar
authors.forename: N S
authors.initials: NS
authors.lastname: Ravindran
authors.forename: M R
authors.initials: MR
authors.lastname: Balasubramaniam
mesh_terms: D001641:Bicuspid / Q000601:surgery; D003481:Cuspid / Q000473:pathology*; D006696:Holography / Q000379:methods*; D006801:Humans; D007368:Interferometry / Q000379:methods; D007834:Lasers; D008027:Light; D008334:Mandible; D016382:Orthodontic Appliance Design; D019516:Orthodontic Space Closure / Q000295:instrumentation / Q000379:methods; D009969:Orthodontic Wires; D013314:Stress, Mechanical; D014081:Tooth Extraction; D014087:Tooth Movement Techniques / Q000295:instrumentation* / Q000379:methods