Crystal Cox1, Tung Nguyen2, Lorne Koroluk3, Ching-Chang Ko4. 1. Private practice, Wilson, NC. 2. Assistant professor, Department of Orthodontics, University of North Carolina, Chapel Hill, NC. 3. Associate professor, Department of Orthodontics, University of North Carolina, Chapel Hill, NC. 4. Professor, Department of Orthodontics, University of North Carolina, Chapel Hill, NC. Electronic address: Ching-Chang_Ko@unc.edu.
Abstract
INTRODUCTION: 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. METHODS: 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. RESULTS: 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. CONCLUSIONS: 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.
INTRODUCTION: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. METHODS: Pseudoelastic force-deflection curves for 30 nickel-titaniumcoil 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. RESULTS: 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. CONCLUSIONS: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.
Authors: Serene A Badran; Juman M Al-Zaben; Lina M Al-Taie; Haya Tbeishi; Mahmoud K Al-Omiri Journal: Angle Orthod Date: 2022-07-01 Impact factor: 2.684
Authors: Haya A Barsoum; Hend S ElSayed; Fouad A El Sharaby; Juan Martin Palomo; Yehya A Mostafa Journal: Angle Orthod Date: 2021-07-01 Impact factor: 2.079