NiTi instruments in endodontics: contemporary concepts, principles, and practical guidance.

This review synthesizes current laboratory and clinical evidence on nickel-titanium (NiTi) endodontic instruments and translates it into guidance for clinical practice, addressing inconsistencies in the translation of research findings and a lack of standardization. Evidence on the evolution, metallurgy, heat treatments (e.g., M-Wire, Gold, and Blue), geometric design, mechanical properties, and clinical performance of contemporary NiTi systems were synthesized, with emphasis on shaping outcomes, including canal transportation, volumetric changes, unprepared canal walls, and remaining dentin thickness. Modern NiTi instruments, particularly those with advanced heat treatments, provide superior flexibility and cyclic fatigue resistance compared with conventional alloys, enabling safer and more predictable canal preparation. Continuous rotary systems often achieve better canal centering and less transportation than reciprocating systems; however, both leave a substantial portion of canal walls untouched, highlighting the essential role of chemical debridement. Long-term clinical success depends primarily on biological factors and careful technique rather than on the specific instrument system. Therefore, NiTi instruments represent the standard of care, offering anatomically respectful canal shaping. Clinicians should integrate knowledge of alloy properties, design features, and failure mechanisms with conservative, load-managing techniques to maximize safety and efficiency.