Effect of heat treatments on Ni-Ti endodontic files

Three brands of rotary nickel-titanium endodontic instruments with some comparable geometric features but with different cross-section (similar tip size and same taper of .04) were selected for this study: MTwo .04(35) (VDW GmbH, Germany), K3 .04(30) (SybronEndo, Mexico) and K3XF .04(30) (SybronEndo, Mexico). K3XF is made from novel R-phase heat-treated metal alloy while all other files were made from traditional Ni-Ti alloy. The instruments were analysed under the following conditions: i) as-received (AR), ii) heat treated at 350 °C, iii) heat treated at 400 °C. The transformation temperatures were determined by differential scanning calorimeter (DSC). Compared to conventionally K3 and MTwo files, R-phase heat treatment K3XF file showed higher transformation temperatures. These results also showed that heat treatments increase the transformation temperatures.