computational study

Teeth, as one of the most important organs of the body, play an essential role in beauty and one of the best ways to treat its disorder and damage to date is the use of orthodontics. Smart wires are widely used in orthodontics for tidying teeth and for reasons such as superelastic behavior, corrosion resistance, high fatigue life, good compatibility and reversible strain. In this paper, the finite element method was used to investigate the mechanical behavior of smart orthodontic wires according to the standard by applying tensile force and considering their metallurgical properties. The macroscopic model for describing the properties of matter was based on Helmholtz thermodynamic free energy. The results showed that: With a 10°C changes in clinical temperature from 26°C to 36°C, the upper and lower plateau stresses and the strain elastic energy decreased about 10% and 18.28% respectively. Also with 10°C change in clinical temperature from 36°C to 46°C, the upper and lower plateau stresses and the strain elastic energy increased approximately 18% and 47.26% respectively. In conclusion, the smart orthodontic wire due to the lower level of the difference between the upper and lower plateau stresses, less elastic strain energy, hysteresis loop and complete dependent on superelastic behavior and high correlation of experimental and numerical results related to force-strain changes showed better performance. This numerical study can provide a method to study the mechanical behavior of smart orthodontic wires with respect to the effects of metallurgical and mechanical properties for the effectiveness of the length of treatment in the tooth.

Simulation of Nitinol shape memory alloy stents behavior for application in trachea stent implantation has been strategically used for solving trachea stenosis. Predicaments like insufficient radial strength, low twisting ability, inappropriate dynamic behavior and restenosis are expected to be solved by the introduction of new designs. Superelastic shape memory alloy stent is an interesting alternative for minimizing these tight spots. The application of finite element method to predict metallurgical of superelastic shape memory alloy stents for trachea duct dilatation is supported by conventional crimp tests. The present simulation modeled the stent material’s superelasticity based on Auricchio theories (Helmholtz free energy) and Lagoudas (Gibbs free energy).Nitinol shape memory alloy stents with material properties contain Af temperature of 24°C° is shown to have the best mechanical performance for clinical applications. Owing to lower chronic outward force (COF), higher radial resistive force (RRF), and more suitable superelastic behavior. Model calculations showed that a very high change of Af temperature could exert a substantial effect on practical performance of the stent. This FEM model can provide a convenient way for evaluation of biomechanical properties of peripheral stents given to effects of metallurgical properties such as austenite finish temperature.