Characterising 12 NiTi Reciprocating Systems: An Integrative Laboratorial Analysis of Design, Mechanics, Metallurgy, Fluid Dynamics and Finite Element Analysis.

Abstract

Aim: To comprehensively compare 12 nickel-titanium (NiTi) reciprocating single-file systems from eight manufacturers by integrating geometric, mechanical, metallurgical and in silico analyses.

Methodology: A total of 276 NiTi reciprocating instruments, representing 12 types across 8 brands, were selected, including Easy-File Flex Regular 25, EdgeOne Fire Primary, Flash 25.06vt, One Files R25 and Blue R25, One RECI N25, Perfect RC R25 (Blue, Gold and Silver), Reciproc R25 (Blue and M-Wire) and WaveOne Gold Primary. They were evaluated using stereomicroscopy, scanning electron microscopy, 3D optical scanning, energy-dispersive X-ray spectroscopy and differential scanning calorimetry to assess design and metallurgical properties. Mechanical performance was tested via buckling resistance and microhardness. A micro-CT-based premolar model was virtually prepared for each instrument to simulate canal shaping. Computational fluid dynamics (CFD) assessed irrigant penetration, wall shear stress and apical pressure. Finite element analysis (FEA) evaluated stress distribution in prepared roots. Data were analysed using the Shapiro-Wilk test for normality and the Kruskal-Wallis test for group comparisons (p < 0.05).

Results: The systems differed considerably in spiral density, cross-sectional design, size, volume and phase transformation temperatures. Instruments with larger apical cores (One Files and Reciproc M-Wire) and austenitic-phase dominance (Perfect RC Silver and One Files) showed greater buckling strength. Files with martensitic phases (Perfect RC Gold, WaveOne Gold and One Files Blue) or hybrid cross-sections (One RECI and Flash) were more flexible. CFD revealed that conservative shaping (Easy-File Flex, EdgeOne Fire, One RECI, WaveOne Gold) increased wall shear stress but reduced apical irrigant exchange. FEA showed similar stress patterns across all groups, with lower stress in restored roots.

Conclusions: Substantial variation exists among current NiTi reciprocating systems in terms of design, mechanics, fluid dynamics and metallurgy. Instruments with large cores and austenitic-phase structure provide superior buckling resistance. Conservative shaping improves shear stress but limits apical cleaning. Root stress remained consistent across systems. These findings highlight the importance of optimising instrument design and clinical protocols to balance shaping efficacy and irrigant delivery.