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Merck

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
Nickel, nanopowder, <100 nm avg. part. size, ≥99% trace metals basis
Sigma-Aldrich
Nickel, rod, diam. 6.35 mm, ≥99.99% trace metals basis
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, powder, <50 μm, 99.7% trace metals basis
Nickel, foil, 2m coil, thickness 0.015mm, 99.9%
Nickel, foil, not light tested, 50x50mm, thickness 0.0025mm, 99.95%
Nickel, foil, 50x50mm, thickness 0.125mm, as rolled, 99.999%
Nickel, rod, 1000mm, diameter 6.35mm, 99%
Nickel, foil, 25x25mm, thickness 0.3mm, annealed, 99%
Nickel, mesh, 30x30mm, nominal aperture 0.04mm, thickness 0.004mm, wire diameter 0.011mm, 500 wires/inch, open area 60%, electro-formed mesh, 99.9%
Nickel, foil, 50x50mm, thickness 0.3mm, as rolled, 99.999%
Nickel, foil, 25x25mm, thickness 2.0mm, annealed, 99%
Nickel, tube, 500mm, outside diameter 1.8mm, inside diameter 1.6mm, wall thickness 0.1mm, hard, 99.5%
Nickel, pellets, 50g, max. size 20mm, 99.99+%
Nickel, foil, 25x25mm, thickness 0.125mm, as rolled, 99.999%
Nickel, foil, 2m coil, thickness 0.025mm, coil width 600mm, as rolled, 99%
Nickel, foil, 50x50mm, thickness 1.0mm, as rolled, 99.999%
Nickel, mesh, 240x240mm, nominal aperture 0.43mm, thickness 0.004mm, wire diameter 0.067mm, 51 wires/inch, open area 75%, electro-formed mesh, 99.9%
Nickel, foil, 50x50mm, thickness 2.0mm, annealed, 99%
Nickel, foil, 150x300mm, thickness 0.25mm, annealed, 99.98%
Nickel, tube, 500mm, outside diameter 1.5mm, inside diameter 1.4mm, wall thickness 0.05mm, hard, 99.5%
Nickel, pellets, 50g, max. size 5mm, 99.99+%
Nickel, microfoil, disks, 25mm, thinness 1.0μm, specific density 895.8μg/cm2, permanent mylar 3.5μm support, 99.99+%
Nickel, foil, 2m coil, thickness 0.02mm, 99.9%
Nickel, wire reel, 10m, diameter 0.125mm, hard, 99.98%
Nickel, foil, 150x300mm, thickness 0.5mm, annealed, 99.98%
Nickel, mesh, 30x30mm, nominal aperture 0.43mm, thickness 0.004mm, wire diameter 0.067mm, 51 wires/inch, open area 75%, electro-formed mesh, 99.9%
Nickel, foil, not light tested, 50x50mm, thickness 0.007mm, 99.95%