Mechanical behavior of M-Wire and conventional NiTi wire used to manufacture rotary endodontic instruments

Evidence for Reduced Fatigue Resistance of Contemporary Rotary Instruments Exposed to Body Temperature

“…However, these tests were all conducted at room temperature, taking care not to generate measurable heat, which is believed to potentially change NiTi properties (15,16).…”

Microstructural and mechanical characterizations of new Ni-Ti endodontic instruments

“…All new instruments showed increased transformation temperatures and were more flexible than the conventional NiTi file. The greater flexibility of these instruments should be attributed to their lower initial apparent elastic modulus, which can be 03005-p. 4 associated with the stress-induced reorientation of the R-phase and/or martensite (present in all instruments analyzed in this study and not only in the "R phase" sample). Although the exact thermomechanical history remains unknown, all the aforementioned data imply that the endodontic instruments are manufactured by cold work followed by heat treatments.…”

“…Each firm named its proprietary thermomechanical process with a specific name like "M-wire", "R phase" and "Controlled Memory (CM) wire" technologies. From manufacturer descriptions, "M-wire" would be produced by applying "specific tensions and heat treatments at various temperatures" [4,5]; "R phase" instruments would be "twisted by a thermal process" during the R-Phase transformation [5,6] and "CM wire" would be a novel NiTi alloy using a special thermomechanical process that controls the memory of the material [5,7]. However, no more information on the real thermomechanical treatments is given.…”

Comparison of the Cyclic Fatigue Resistance of Nickel-Titanium Rotary Instruments Manufactured using Controlled Memory Wire

“…[12] Although using extracted human teeth in cyclic fatigue studies represents clinical conditions well, it is not possible to standardize the anatomical variations of teeth. [13] Thus, the use of extracted teeth in cyclic fatigue studies is not ideal.…”