Korean J Orthod.  2019 Jul;49(4):214-221. 10.4041/kjod.2019.49.4.214.

Effects of reversing the coiling direction on the force-deflection characteristics of nickel-titanium closed-coil springs

Affiliations
  • 1Department of Orthodontics, School of Dentistry, Seoul National University, Seoul, Korea. drwhite@snu.ac.kr
  • 2Department of Mechanical System Engineering, Hansung University, Seoul, Korea.
  • 3Future Convergence Research Division, Korea Institute of Science and Technology, Seoul, Korea.
  • 4Department of Materials Science & Engineering, Chungnam National University, Daejeon, Korea. jhhan@cnu.ac.kr
  • 5Dental Research Institute, Seoul National University, Seoul, Korea.

Abstract


OBJECTIVE
To investigate the effects of reversing the coiling direction of nickeltitanium closed-coil springs (NiTi-CCSs) on the force-deflection characteristics.
METHODS
The samples consisted of two commercially available conventional NiTi-CCS groups and two reverse-wound NiTi-CCS groups (Ormco-Conventional vs. Ormco-Reverse; GAC-Conventional vs. GAC-Reverse; n = 20 per group). The reverse-wound NiTi-CCSs were directly made from the corresponding conventional NiTi-CCSs by reversing the coiling direction. Tensile tests were performed for each group in a temperature-controlled acrylic chamber (37 ± 1℃). After measuring the force level, the range of the deactivation force plateau (DFP) and the amount of mechanical hysteresis (MH), statistical analyses were performed.
RESULTS
The Ormco-Reverse group exhibited a significant shift of the DFP end point toward the origin point (2.3 to 0.6 mm), an increase in the force level (1.2 to 1.3 N) and amount of MH (1.0 to 1.5 N) compared to the Ormco-Conventional group (all p < 0.001), which indicated that force could be constantly maintained until the end of the deactivation curve. In contrast, the GAC-Reverse group exhibited a significant shift of the DFP-end point away from the origin point (0.2 to 3.3 mm), a decrease in the force level (1.1 to 0.9 N) and amount of MH (0.6 to 0.4 N) compared to the GAC-Conventional group (all p < 0.001), which may hinder the maintenance of force until the end of the deactivation curve.
CONCLUSIONS
The two commercially available NiTi-CCS groups exhibited different patterns of change in the force-deflection characteristics when the coiling direction was reversed.

Keyword

Nickel-titanium closed-coil spring; Range of the force plateau; Force-deflection characteristics; Reversing the coiling direction
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