Mechanical Properties of Graded Thermodynamic Nickel Titanium Archwires in Bending and Torsion

Background: Graded thermodynamic nickel titanium (GT-NiTi) wires purportedly deliver differential force levels in different archwire regions. No studies evaluating the force delivery characteristics of such wires currently exist. Objective: To evaluate the mechanical properties of GT-NiTi wires in bending and torsion. Methods: Six samples of 0.016 x 0.022â and 0.017 x 0.025â of GT-NiTi wires were divided into incisor, premolar, and molar sections and each segment was tested in bending and torsion. The characteristics of the unloading superelastic plateau were evaluated and compared with similar segments of non-graded, control NiTi wires. Results: Statistically significant differences in mean force and moment levels were found between the three sections of GT-NiTi wires, but not in control wires. Small but statistically significant differences in length and slope were also found. Conclusion: GT-NiTi wires deliver different forces and moments in different archwire sections. Clinicians can use this knowledge to optimize force delivery for treatment.M.Sc