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Published on: July 28, 2020
Load-deflection characteristics of superelastic nickel-titanium wires
Theodosia N Bartzela1, Christiane Senn, Andrea Wichelhaus
1Department of Orthodontics and Oral Biology, University Medical Centre, Nijmegen, The Netherlands. t.bartzela@dent.umcn.nl
Objective:
To determine the mechanical properties of commercially available thermodynamic wires and to classify these wires mathematically into different groups.
Materials And Methods:
The samples examined were 48 nickel-titanium (NiTi) alloy orthodontic wires commercially available from five manufacturers. These samples included 0.016-inch, 0.016- x 0.022-inch, 0.017- x 0.025-inch, and 0.018- x 0.025-inch wires. The superelastic properties of the NiTi wires were evaluated by conducting the three-point bending test under uniform testing conditions. The group classification was made under mathematically restricted parameters, and the final classification was according to their clinical plateau length.
Results:
The orthodontic wires tested are classified as follows: (1) true superelastic wires, which presented a clinical plateau length of >/=0.5 mm; (2) borderline superelastic with a clinical plateau length of <0.5 mm and >0.05 mm; and (3) nonsuperelastic, with a clinical plateau length of =0.05 mm. The results showed that the range of products displays big variations in quantitative and qualitative behavior. A fraction of the tested wires showed weak superelasticity, and others showed no superelasticity. Some of the products showed permanent deformation after the three-point bending test.
Conclusion:
A significant fraction of the tested wires showed no or only weak superelasticity. The practitioner should be informed for the load-deflection characteristics of the NiTi orthodontic wires to choose the proper products for the given treatment needs.
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