Kumar Y Mahesh, Ravindran N S, Balasubramaniam M R
Department of Orthodontics, KVG Dental College and Hospital, Sullia, India.
Angle Orthod. 2009 Mar;79(2):368-72. doi: 10.2319/121407-587.1.
To estimate and compare the magnitude and direction of initial displacement of the canine produced by four different canine retraction springs.
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.
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.
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.
