A superelastic endodontic such (11), is formed by grinding a superelastic wire (8) to form a file preform or blank (12), and rotating a first end of the blank (12) while preventing rotation of a second end of the blank (12), The file blank (12) is maintained in the austenite phase at least until twisted to form a stress induced martensite which is plastically deformed by the twisting. A heat treatment step may be performed prior to twisting, during twisting or after twisting of the preform or blank, (12), The file blank (12) may be heated by electrical heating methods or by the blank in a heated liquid (234).
