For dental orthodontic applications, NiTi wires are used under bending conditions in the oral environment for a long period. The purpose of this study was to investigate the effect of bending stress on the corrosion of NiTi wires using potentiodynamic and potentiostatic tests in artificial saliva. The results indicated that bending stress induces a higher corrosion rate of NiTi wires in passive regions. It is suggested that the passive oxide film of specimens would be damaged under bending conditions. Auger electron spectroscopic analysis showed a lower thickness of passive films on stressed NiTi wires compared with unstressed specimens in the passive region. By scanning electron microscopy, localized corrosion was observed on stressed Sentalloy specimens after a potentiodynamic test at pH 2. In conclusion, this study indicated that bending stress changed the corrosion properties and surface characteristics of NiTi wires in a simulated intra-oral environment.
Clinical implications :
According to the study , it concluded that there is an increase in corrosion of NiTi and a possible toxicity when there is a stress on the wire on different points especially if the PH is low.
Low PH can be detected using specific tests or can be known from patients who have high caries index.
* Liu IH, Lee TM, Chang CY, Liu CK. Effect of load deflection on corrosion behavior of NiTi wire. J Dent Res 86:539-543, 2007.