In-vivo force decay of nickel-titanium closed-coil springs.

American journal of orthodontics and dentofacial orthopedics : official publication of the American Association of Orthodontists, its constituent societies, and the American Board of Orthodontics (2014-04-08)
Crystal Cox, Tung Nguyen, Lorne Koroluk, Ching-Chang Ko
ABSTRACT

Nickel-titanium closed-coil springs are purported to deliver constant forces over extended ranges of activation and working times. In-vivo studies supporting this claim are limited. The objective of this study was to evaluate changes in force-decay properties of nickel-titanium closed-coil springs after clinical use. Pseudoelastic force-deflection curves for 30 nickel-titanium coil springs (used intraorally) and 15 matched laboratory control springs (simulated intraoral conditions: artificial saliva, 37°C) were tested before and after retrieval via dynamic mechanical analysis and a testing machine, respectively, to evaluate the amounts of force-loss and hysteresis change after 4, 8, or 12 weeks of working time (n = 10 per group). The effects of the oral environment and clinical use on force properties were evaluated by comparing in-vivo and in-vitro data. The springs studied showed a statistically significant decrease in force (approximately 12%) after 4 weeks of clinical use (P <0.01), with a further significant decrease (approximately 7%) from 4 to 8 weeks (P = 0.03), and force levels appearing to remain steady thereafter. Clinical space closure at an average rate of 0.91 mm per month was still observed despite this decrease in force. In-vivo and in-vitro force-loss data were not statistically different. Nickel-titanium closed-coil springs do not deliver constant forces when used intraorally, but they still allow for space-closure rates of approximately 1 mm per month.

MATERIALS
Product Number
Brand
Product Description

Sigma-Aldrich
Raney®-Nickel, W.R. Grace and Co. Raney® 2800, slurry, in H2O, active catalyst
Sigma-Aldrich
Nickel, nanopowder, <100 nm avg. part. size, ≥99% trace metals basis
Sigma-Aldrich
Nickel, powder, <150 μm, 99.99% trace metals basis
Sigma-Aldrich
Nickel, foil, thickness 0.125 mm, ≥99.9%
Sigma-Aldrich
Raney®-Nickel, W.R. Grace and Co. Raney® 2400, slurry, in H2O, active catalyst
Sigma-Aldrich
Nickel, wire, diam. 0.25 mm, ≥99.9%
Sigma-Aldrich
Nickel, foil, thickness 0.5 mm, 99.98% trace metals basis
Sigma-Aldrich
Nickel, foil, thickness 0.1 mm, 99.98% trace metals basis
Sigma-Aldrich
Nickel, wire, diam. 0.5 mm, ≥99.9% trace metals basis
Sigma-Aldrich
Nickel, wire, diam. 0.5 mm, ≥99.99% trace metals basis
Sigma-Aldrich
Nickel, foil, thickness 0.25 mm, 99.995% trace metals basis
Sigma-Aldrich
Nickel, rod, diam. 6.35 mm, ≥99.99% trace metals basis
Nickel, mesh, 100x250mm, nominal aperture 0.73mm, wire diameter 0.25mm, 26x26 wires/inch, open area 55%, plain weave mesh, 99%
Nickel, wire reel, 20m, diameter 0.025mm, as drawn, 99.98%
Nickel, wire reel, 10m, diameter 0.01mm, as drawn, 99.98%
Nickel, rod, 100mm, diameter 16mm, 99.99+%
Nickel, foil, not light tested, 100x100mm, thickness 0.01mm, 99.95%
Nickel, wire reel, 20m, diameter 0.125mm, hard, 99.98%
Nickel, rod, 100mm, diameter 3.0mm, 99%
Nickel, wire reel, 1m, diameter 1.0mm, hard, 99.98%
Nickel, broken cathode squares, 1000g, max. size 50mm, 99.8%
Nickel, tube, 1000mm, outside diameter 6.5mm, inside diameter 5.5mm, wall thickness 0.5mm, hard, 99.5%
Nickel, foil, 50mm disks, thickness 0.05mm, annealed, 99%
Nickel, wire reel, 20m, diameter 0.5mm, as drawn, 99%
Nickel, foil, 4mm disks, thickness 0.075mm, annealed, 99%
Nickel, foil, 4mm disks, thickness 0.075mm, as rolled, 99.98%
Nickel, foil, 4mm disks, thickness 0.125mm, annealed, 99%
Nickel, foil, 4mm disks, thickness 0.125mm, annealed, 99.98%
Nickel, foil, 4mm disks, thickness 0.125mm, as rolled, 100%
Nickel, foil, 4mm disks, thickness 0.125mm, as rolled, 99.99+%