Design, Metallurgical Features, and Mechanical Behavior of Five Reciprocating NiTi Endodontic Systems: A Multimethod Analysis.

Introduction: This work aimed to examine the geometrical, metallurgical, and static mechanical properties of five reciprocating NiTi endodontic files with similar cross-sectional geometries. Materials and Methods: Reciproc Blue, ProDesign R, V File, V+ File, and Univy One systems were evaluated using a multimethod approach including geometrical analysis, scanning electron microscopy, energy-dispersive spectroscopy, differential scanning calorimetry, X-ray diffraction, bending resistance, and torsional tests. Results: R-phase was predominant in most instruments, while the Univy One system showed indications of a combined martensitic and R-phase structure. ProDesign R demonstrated superior flexibility, whereas Reciproc Blue and V File exhibited greater torsional resistance. Cross-sectional area was an important factor influencing the mechanical characteristics of the instruments, although metallurgical aspects appeared to influence the behavior of specific systems. Conclusion: Geometry and metallurgical characteristics influenced the observed static mechanical behavior of the evaluated reciprocating instruments. Instruments exhibiting higher proportions of martensite and R-phase demonstrated enhanced flexibility, while bending resistance was also strongly affected by cross-sectional geometry, highlighting the combined influence of material properties and design on mechanical performance. However, the findings should be interpreted within the limitations of static mechanical evaluation, since cyclic fatigue testing was not performed.