A Study on Creep and Compressive Force of Open-Type Coil Springs

DOI 16 References
  • NAKANISHI Ryouta
    Department of Orthodontics, The Nippon Dental University, School of Dentistry, at Niigata
  • NAGAO Yasuhiro
    Nagao Dental Clinic
  • OGURA Hideo
    Department of Dental Materials Science, The Nippon Dental University, School of Dentistry, at Niigata
  • KOSUGE Naoki
    Department of Orthodontics, The Nippon Dental University, School of Dentistry, at Niigata
  • KAMEDA Akira
    Department of Orthodontics, The Nippon Dental University, School of Dentistry, at Niigata

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  • オープンタイプコイルスプリングのクリープと圧縮力に関する研究

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Abstract

The creep and the compressive force(resistance to compression)of orthodontic open-type coil springs made of stainless steel and Ni-Ti alloy were investigated to explore the time for the replacement of these springs. The coil springs were compressed under loading times(7, 30 and 90 days)and compression rate(20% and 40%)that were chosen to simulate clinical use. After compression, the creep and the compression force(chosen to resistance to compression)of the coil springs were measured. No creep was induced in the Ni-Ti coil springs regardless of the laoding time and compression rate. On the other hand, the stainless steel coil spring showed creep with increases in the loading time and creep after 90 days of 4.2% and 7.6% under 20% and 40% compression, respectively. The compressive force at 20% or 40% compression of the original length did not significantly change for the Ni-Ti coil spring at any loading time, whereas that of the stainless steel coil spring significantly decreased after 90 days. This suggests that the stainless steel coil spring needs to be replaced after 90 days of application, while the Ni-Ti coil spring does not.

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