Ni-free superelastic titanium alloys for medical and dental applications

Superelasticity refers to a type of elastic response exhibited by certain materials to an applied stress. This property has been shown to be significantly beneficial and sometimes necessary in a wide variety of biomedical and dental applications. The superelastic alloy that is currently in extensive use in the medical and dental industries is the NiTi alloy, known as Nitinol. Recently, there have been a number of discoveries about the health hazards of the Ni ions released from NiTi orthodontic archwires, bone implants, stents, and other types of implants and tools. These concerns have encouraged the research community to investigate designing and developing Ni-free Ti-based superelastic alloy systems with better biocompatibility, similar or superior mechanical properties, and superelasticity. This chapter discusses the basic metallurgical aspects of superelasticity in Ni-Ti and Ni-free alloys, recent developments in the design of Ni-free superelastic titanium alloys, and some of the current medical and dental applications where superelasticity is required.