Evaluation of cyclic fatigue resistance of different Ni-Ti files

Aim. The aim of this study was to compare the cyclic fracture resistance of rotating endodontic Ni-Ti instruments (Protaper F2, Flex Master and Reciproc) used in rotation and in reciprocating motion. Methods. The cyclic fracture resistance of rotary Ni-Ti endodontic instruments was tested with a special device aiming at recreating the same conditions for all instruments. The instruments were rotated at constant speed and torque up to fracture, recording the time to fracture in seconds. 10 Flex Master 25/06, 10 Protaper F2, 10 Reciproc used in rotating motion and 10 Reciproc using in reciprocating mode were tested. A statistical analysis was applied to check differences between the groups. Results. When comparing the resistance to cyclic fatigue, Reciproc had a mean of 263 seconds in continuous rotation and 318 seconds in reciprocating motion, Protaper F2 used in continuous rotation had a resistance of 53 seconds while the duration for Flexmaster 25.06 in continuous rotation was 61 seconds. Statistical differences were found among the groups. Conclusions. The resistance to cyclic fatigue is significantly influenced by the type of movement (reciprocating better than rotating). Also the kind of alloy is important (Reciproc-m wire was always more resistant than standard ni-ti even in rotating motion).