Observation of Phase Transformation in Shape Memory Alloy NiTi Wire during In Vitro Simulation of Orthodontic Treatment

Abstract

The aim of this study was to simulate the different loadings on NiTi Shape Memory Alloy in the form of wire that occurs in orthodontic praxis. Our main goals were to detect and determine the beginning of the stress-induced transformation from the austenite to martensite phases and to indicate the transformation plateau at different deformations during orthodontic treatment usingin-vitrosimulation. For this reason, we developed two prototype devices forin-situsimulation of orthodontic treatment by which we measured the electrical resistance and hardness. Accompanying these two properties and the microstructure observations of loaded wires by Transmission Electron Microscopy enabled us to detect successfully the stabilized stress-induced martensite due phase transformation. We found out that transformation depends strongly on the type of loading.