Surface Wear and Cyclic Fatigue Resistance of Novel NiTi Instruments
Objectives: The aim of this study was to evaluate surface wear and cyclic fatigue resistance of reciprocating (Reciproc Blue, WaveOne Gold) and rotary (XP-endo Shaper, TruNatomy) instrumentation systems, after use in curved canals at body temperature.
Methods: Twenty new NiTi instruments (n=5/each group): Reciproc Blue, WaveOne Gold, XP-endo Shaper (XPS) and TruNatomy Prime (TRN) were used twice for the instrumentation of simulated curved canals (40o) in plastic resin blocks. The instrumentation was performed according to manufacturer's instructions for each system at body temperature using 5 mL of 2.5% NaOCl for each canal. The surface of each instrument was evaluated before instrumentation, and after the first and second use in curved canals by using noncontact 3D optical surface profilometer (Zygo NewView™ 7100). Three roughness parameters were evaluated: the average roughness (Ra), root mean square roughness (Rq), and peak to valley average height (Rz). After two uses, the tested instruments were submitted to cyclic fatigue (CF) test to evaluate the time to failure. The obtained data were analyzed with one-way analysis of variance ANOVA and post-hoc tests (α =0.05).
Results: The TruNatomy instruments showed no significant difference in roughness compared to the reciprocating files, irrespective of the evaluation stage (p=1.0). The XPS instruments showed significantly higher values of roughness compared to the TruNatomy, in every stage, especially after the second use (P < .008). The reciprocating instruments had significantly higher CF resistance compared to rotary instruments (P < .05). Reciproc Blue showed the highest CF resistance, with 188,4 sec time to failure. XPS had the lowest CF resistance (55 sec), with no significant difference compared to TruNatomy (67 sec).
Conclusions: The TruNatomy and reciprocating instruments showed minimal surface wear, after two uses in curved root canals. The Xp-endo Shaper exhibited significantly higher surface wear. Reciprocating instruments exhibited superior cyclic fatigue resistance compared to novel rotary instruments.