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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, not light tested, 25x25mm, thickness 0.001mm, 99.95%
Nickel, foil, not light tested, 25x25mm, thickness 0.0005mm, temporary acrylic support, 99.95%
Nickel, foil, light tested, 100x100mm, thickness 0.007mm, 99.95%
Nickel, foil, not light tested, 100x100mm, thickness 0.002mm, 99.95%
Nickel, foil, 0.5m coil, thickness 1.0mm, annealed, 99%
Nickel, wire reel, 100m, diameter 0.125mm, annealed, 99.98%
Nickel, foil, 0.3m coil, thickness 0.125mm, as rolled, 99.99+%
Nickel, foil, 10mm disks, thickness 0.025mm, as rolled, 99.99+%
Nickel, foil, 0.5m coil, thickness 0.15mm, coil width 12mm, annealed, 99%
Nickel, foil, 2m coil, thickness 0.5mm, annealed, 99.98%
Nickel, wire reel, 10m, diameter 0.125mm, annealed, 99.98%
Nickel, wire reel, 0.2m, diameter 0.5mm, as drawn, 99.99+%
Nickel, foil, 10mm disks, thickness 0.003mm, 99.95%
Nickel, foil, 0.2m coil, thickness 0.004mm, hard, 99%
Nickel, wire reel, 10m, diameter 0.025mm, as drawn, 99.98%
Nickel, foil, 10mm disks, thickness 0.0125mm, 99.9%
Nickel, foil, 0.5m coil, thickness 0.20mm, annealed, 99%
Nickel, foil, 10m coil, thickness 0.05mm, coil width 2mm, annealed, 99%
Nickel, tube, 500mm, outside diameter 8.4mm, inside diameter 8.15mm, wall thickness 0.125mm, hard, 99.5%
Nickel, foil, 10mm disks, thickness 0.0125mm, annealed, 99%
Nickel, foil, 2m coil, thickness 0.075mm, as rolled, 99.98%
Nickel, foil, 150x150mm, thickness 0.15mm, annealed, 99%
Nickel, foil, 8mm disks, thickness 0.025mm, annealed, 99%
Nickel, foil, 8mm disks, thickness 0.05mm, as rolled, 99.98%