Torsional elastic property measurements of selected orthodontic archwires

Brent E. Larson, Robert P. Kusy, John Q. Whitley

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A method for quantifying the torsional elastic properties of orthodontic archwires was investigated using three different alloys: stainless steel [SS], beta titanium [βTi], and nickel titanium [NiTi]. The shear moduli (G) were determined dynamically using a torsion pendulum. Aftera clamping correction was applied, the values of (G equalled 11.0-11.3, 4.3-4.4, and 2.3-3.0 Msi for SS, βTi, and NiTi wires respectively. Using a 10% energy loss criterion in a static test, the torsional yield strengths (τys) were all nearly 100 ksi except for the 0.018″ SS (51 ksi) and rectangular NiTi (13-17 ksi). The latter exhibited some pseudoelastic behaviour which could only be accommodated by the Johnson Elastic Limit (JEL). Having determined G, Tys, and the wire dimensions, the three basic torsional elastic properties (stiffness, strength, range) were calculated for each of the wires. The NiTi wires displayed the greatest range and the least stiffness, whereas SS wires showed the greatest stiffness and the least range. As predicted in earlierwork, the properties of βTi were intermediate.

Original languageEnglish (US)
Pages (from-to)165-179
Number of pages15
JournalClinical Materials
Issue number3
StatePublished - 1987

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