Superelasticity and Shape Memory Effect in NiTi Orthodontic Wires

Airoldi, G.; Riva, G.; Vanelli, M.

doi:10.1051/jp4/1995581205

Cited by 10 publications

(9 citation statements)

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“…4, where the reversion force vs. temperature is plotted for a fixed deflection of 2 mm, either during TC I (bold line) or TC I1 (thin line). As previously found [5], an hysteresis loop appears between the reversion force values obtained during TC I and those during TC 11. The reversion force related to the stress induced martensite process is clearly involved during the heating step 37-55°C and the non linear behaviour in the range 30-20°C is presumably related to the R-phase.…”

Section: Resultssupporting

confidence: 82%

The Reversion Force of NiTi Orthodontic Wires in the Temperature Domain 5 ÷ 55 °C

1997

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Abstract. The interest in using the pseudoelastic properties of NiTi wires in orthodontic practice arises chiefly from the expectation that they can afford low continuous forces at constant temperature. The reversion force developed by NiTi archwires depends, however, upon temperature since the superelastic force follows a Clausius-Clapeyron like equation. Actually the oral environment temperature is modified as a consequence of hotJcold liquid/solid intake in the temperature range 5"-5S°C, as previously evaluated. In the above-mentioned temperature range first results have already been obtained on the reversion force variation. Attention is focused here on the reversion force as a function of temperature under different fixed constraints. Tensile and 3-point bending tests have been performed on NiTi orthodontic wires, adopted in orthodontic practice, starting at body temperature: loading and partial unloading have been performed in order to fix different constraint conditions corresponding to different states in orthodontic therapy. The variation of the reversion force has been studied as a function of temperature. Evidence has been obtained of the hysteretic behaviour of the reversion force as a function of temperature. The results show that after a temperature loop to high temperature the reversion force is generally changed: the overall shape of the hysteresis cycle appears dominated by the presence of the R-phase at T<37OC and by the stress-induced martensite at P37OC.

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Section: Resultssupporting

confidence: 82%

The Reversion Force of NiTi Orthodontic Wires in the Temperature Domain 5 ÷ 55 °C

1997

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“…Because the recovery is prevented, the wires exert light forces on the teeth for the entire period in which the temperature is above the normal values [21]. SMA wires are also inserted into steel palatal arches (Figure 8(a)); a palatal arch is mounted on superior molars and applies rotating, expanding and torquing forces.…”

Section: Sma Applications In the Orthodontic Fieldmentioning

confidence: 99%

Biomedical Applications of Shape Memory Alloys

Petrini

Migliavacca

2011

Journal of Metallurgy

464

200

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Shape memory alloys, and in particular NiTi alloys, are characterized by two unique behaviors, thermally or mechanically activated: the shape memory effect and pseudo-elastic effect. These behaviors, due to the peculiar crystallographic structure of the alloys, assure the recovery of the original shape even after large deformations and the maintenance of a constant applied force in correspondence of significant displacements. These properties, joined with good corrosion and bending resistance, biological and magnetic resonance compatibility, explain the large diffusion, in the last 20 years, of SMA in the production of biomedical devices, in particular for mini-invasive techniques. In this paper a detailed review of the main applications of NiTi alloys in dental, orthopedics, vascular, neurological, and surgical fields is presented. In particular for each device the main characteristics and the advantages of using SMA are discussed. Moreover, the paper underlines the opportunities and the room for new ideas able to enlarge the range of SMA applications. However, it is fundamental to remember that the complexity of the material and application requires a strict collaboration between clinicians, engineers, physicists and chemists for defining accurately the problem, finding the best solution in terms of device design and accordingly optimizing the NiTi alloy properties.

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“…All the analyzed structures are assumed to be constituted of a specific Ni-Ti wire produced by GAC International Inc.; they have a rectangular cross-section of dimension h = 0.64 mm and b = 0.46 mm. In particular, this specific alloy has been experimentally investigated by Airoldi et al [1] in two different sets of experiments:…”

Section: Tension-compression Testmentioning

confidence: 99%

“…Then, following Reference [1], the behavior of a simply supported beam subjected to a pointwise central force is studied. The beam length is L = 14 mm.…”

Section: Tension-compression Testmentioning

confidence: 99%

Phenomenological 3D and 1D consistent models for shape-memory alloy materials

2009

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The paper deals with the modeling and the development of a numerical procedure for the analysis of shape-memory alloy (SMA) elements in order to predict the main features of SMA devices. A 3D SMA model in the framework of small strain theory is developed starting from the thermo-mechanical model proposed by Souza et al. (Eur J Mech A/Solids 17:789-806, 1998) and modified by Auricchio and Petrini (Int J Numer Methods Eng 55: 2002). The aim of this paper is to propose some more modifications to the original model, to derive its consistent 1D formulation, to clarify the mechanical meaning of the material parameters governing the constitutive model. A robust time integration algorithm is developed in the framework of the finite element method and a new beam finite element is proposed. Some numerical applications and a comparison with experimental data available in literature are carried out in order to assess the ability of the proposed model to describe the SMA behavior.

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Superelasticity and Shape Memory Effect in NiTi Orthodontic Wires

Cited by 10 publications

References 0 publications

The Reversion Force of NiTi Orthodontic Wires in the Temperature Domain 5 ÷ 55 °C

The Reversion Force of NiTi Orthodontic Wires in the Temperature Domain 5 ÷ 55 °C

Biomedical Applications of Shape Memory Alloys

Phenomenological 3D and 1D consistent models for shape-memory alloy materials

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