The aim of this study was to investigate the mechanical properties of superelastic and thermal nickel - titanium (NiTi) archwires for correct selection of orthodontic wires. Seven different NiTi wires of two different sizes (0.014 and 0.016 inches), commonly used during the alignment phase, were tested. A.three-point bending test was carried out to evaluate the load - defl ection characteristics. The archwires were subjected to bending at a constant temperature of 37°C and defl ections of 2 and 4 mm. Analysis of variance showed that thermal NiTi wires exerted signifi cantly lower working forces than superelastic wires of the same size in all experimental tests ( P.< 0.05). Wire size had a signifi cant effect on the forces produced: with an increase in archwire dimension, the released strength increased for both thermal and superelastic wires. Superelastic wires showed, at a defl ection of 2 mm, narrow and steep hysteresis curves in comparison with the corresponding thermal wires, which presented a wide interval between loading and unloading forces. During unloading at 4 mm of defl ection, all wires showed curves with a wider plateau when compared with 2 mm defl ection. Such a difference for the superelastic wires was caused by the martensite stress induced at higher deformation levels. A.comprehensive understanding of mechanical characteristics of orthodontic wires is essential and selection should be undertaken in accordance with the behaviour of the different wires. It is also necessary to take into account the biomechanics used. In low-friction mechanics, thermal NiTi wires are to be preferred to superelastic wires, during the alignment phase due to their lower working forces. In conventional straightwire mechanics, a low force archwire would be unable to overcome the resistance to sliding.

Load-deflection characteristics of superelastic and thermal nickel-titanium wires

MATARESE, Giovanni;Di Bella G;NUCERA, RICCARDO;BORSELLINO, Chiara;CORDASCO, Giancarlo
2013-01-01

Abstract

The aim of this study was to investigate the mechanical properties of superelastic and thermal nickel - titanium (NiTi) archwires for correct selection of orthodontic wires. Seven different NiTi wires of two different sizes (0.014 and 0.016 inches), commonly used during the alignment phase, were tested. A.three-point bending test was carried out to evaluate the load - defl ection characteristics. The archwires were subjected to bending at a constant temperature of 37°C and defl ections of 2 and 4 mm. Analysis of variance showed that thermal NiTi wires exerted signifi cantly lower working forces than superelastic wires of the same size in all experimental tests ( P.< 0.05). Wire size had a signifi cant effect on the forces produced: with an increase in archwire dimension, the released strength increased for both thermal and superelastic wires. Superelastic wires showed, at a defl ection of 2 mm, narrow and steep hysteresis curves in comparison with the corresponding thermal wires, which presented a wide interval between loading and unloading forces. During unloading at 4 mm of defl ection, all wires showed curves with a wider plateau when compared with 2 mm defl ection. Such a difference for the superelastic wires was caused by the martensite stress induced at higher deformation levels. A.comprehensive understanding of mechanical characteristics of orthodontic wires is essential and selection should be undertaken in accordance with the behaviour of the different wires. It is also necessary to take into account the biomechanics used. In low-friction mechanics, thermal NiTi wires are to be preferred to superelastic wires, during the alignment phase due to their lower working forces. In conventional straightwire mechanics, a low force archwire would be unable to overcome the resistance to sliding.
2013
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11570/2666381
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