Orthodontic wires are components of fixed appliances used to perform the necessary tooth movements in the course of the orthodontic treatment. A variety of materials e.g. metals, alloys, polymers and composites are used to produce orthodontic wires. This study examined the mechanical strength and cracks resistance of three different types of wires, i.e. made of: austenitic steel grade AISI 303, NiTi alloy and Tiβ alloy. Corrosion processes are regarded to have a harmful effect on the properties

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... of orthodontic wires, such as their strength, biocompatibility and aesthetic appearance. In this study, we investigated the corrosive behaviour of the wires in the artificial saliva solutions with varied pH simulating the natural oral cavity environment. It was demonstrated that the orthodontic rectangular wires made of austenitic steel grade AISI 303 exhibited the highest tensile strength. The NiTi alloy wires exhibited the best plastic properties of all the examined samples. In the case of electrochemical tests (changes in corrosion potential over a period of 24 h), the wire made of austenitic steel and the NiTi alloy wire reached a stable level of the stationary potential in the acidic environment. For the wires made of Tiβ, the highest stationary potential was observed in the alkaline environment. Additionally, the Tiβ alloy wire revealed the broadest passivation area in the specified potential scope.