Cyclic fatigue and torsional resistance of two new nickel - titanium instruments used in reciprocation motion : Reciproc Versus

The use of reciprocating movement (RM) was claimed to increase the resistance of nickel-titanium (NiTi) file to fatigue in comparison to continuous rotation (CR). Recently two new brands of NiTi file have been marketed for use in a RM mode. The purpose of this study was to compare the cyclic fatigue resistance and torsional resistance of these two files; Reciproc and WaveOne. Cyclic fatigue test with a simultaneous pecking motion was performed with the instrument (n = 10 each) operating in the recommended reciprocation motion until fracture for th Reciproc R25 and WaveOne Primary files. ProTaper F2 was tested in continuous rotation to serve as a control for comparison. The number of cycles to fracture (NCF) was determined by measuring the time to fracture. The length of the fragment was measured and the fracture surface examined using SEM. Torsional strength was measured using a torsiometer after fixing the apical 5 mm of the instrument rigidly. Statistical analysis was performed using one-way ANOVA. The results showed that Reciproc had a higher NCF, and WaveOne had a higher torsional resistance, than the others. Both reciporcating files demonstrated a significantly higher cyclic fatigue and torsional resistances than ProTaper (P < .05). The fractographic analysis showed specific features of cyclic fatigue and torsional resistance for all instruments. The two brands of NiTi file for use with a reciprocation motion seem to have superior mechanical properties.