Effect of EDTA, NaOCl, and HEDP-based irrigants on the mechanical properties of heat treated NiTi endodontic instruments.

AIMS: This study evaluated the influence of different root canal irrigants, 3% sodium hypochlorite (NaOCl), 17% ethylenediaminetetraacetic acid (EDTA), and a NaOCl-HEDP combination (Dual Rinse), on the mechanical behavior of nickel-titanium (NiTi) endodontic instruments with identical geometry but varying heat treatments. METHOD: A total of 720 One Curve NiTi files (MicroMega, Besançon, France) with three heat treatments (none, C.Wire, S.Wire) were allocated into subgroups exposed to four irrigants (distilled water, NaOCl, NaOCl-HEDP, EDTA) at 21 °C and 35 °C for 1, 5, or 10 min. Mechanical tests were conducted in accordance with ISO 3630-1 to assess bending resistance, maximum torsional resistance, and angular deflection at fracture. Profilometric analysis was performed to identify potential signs of corrosion. RESULTS: No significant differences were found in maximum bending or torsional torque across irrigant groups. However, EDTA exposure resulted in increased angular deflection at fracture, followed by distilled water. NaOCl showed the lowest angular deflection, while NaOCl-HEDP exhibited intermediate behavior. Heat-treated instruments, particularly S.Wire, consistently showed superior mechanical performance across all test conditions.