In vivo force decay of NiTi closed coil springs

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  • March 22, 2019
Creator
  • Cox, Crystal R.
    • Affiliation: School of Dentistry, Department of Orthodontics
Abstract
  • Nickel-titanium(NiTi) closed coil springs are purported to deliver constant forces over extended activation ranges. In vivo studies supporting this claim are limited. Objectives: Evaluate force decay properties of NiTi coil springs after clinical use. Methods: Force-deflection curves for 30 NiTi coil springs(used intra-orally) and 15 laboratory springs were generated pre- and post-retrieval to evaluate force loss following 4, 8, or 12 weeks of use. In vivo and in vitro data were compared to evaluate effect of the oral environment on force properties. Results: Springs showed force decrease (~12%,p<0.01) following 4 weeks of clinical use, with a further significant decrease (~7%,p=0.03) from 4-8 weeks; force levels remained steady thereafter. Space closed at an average rate of 0.91mm/month. In vivo and in vitro force loss data were not statistically different. Conclusions: NiTi closed coil springs do not deliver constant forces when used intra-orally, but still allow for space closure rates of ~1mm/month.
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  • ... in partial fulfillment of the requirements for the degree of Master of Science in the School of Dentistry (Orthodontics).
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  • Ko, Ching-Chang
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