Clinical Surface Alteration of Reciprocating Nickel-Titanium Instruments Following Root Canal Preparation and Sterilization: A Three-Dimensional FE-SEM-Based Analysis.

BACKGROUND: The study aims to evaluate the surface alteration of the reciprocating nickel-titanium (NiTi) instrument after clinical instrumentation. METHODS: This clinical investigation evaluated surface changes of reciprocating NiTi instruments after routine endodontic use and sterilization. Eleven One RECI instruments, each used to prepare a single molar canal in one patient (11 patients, 11 canals, and 11 instruments), were evaluated. Maxillary and mandibular molars requiring primary treatment were instrumented using One RECI files under standardized clinical protocols. Following use-and-steam autoclave sterilization, instruments were analyzed using field-emission scanning electron microscopy (FE-SEM). Paired stereoscopic images obtained at standardized locations were reconstructed into three-dimensional surface models using Mountains software (Digital Surf, Besancon, France). Areal surface roughness parameters, including Sa, Sq, and Sz, were calculated according to ISO 25178. RESULTS: Clinical use resulted in increased Sa and Sq values at the cutting edge of the instruments, indicating measurable surface alteration after routine treatment and sterilization. These findings were consistent with trends previously reported under preclinical conditions. CONCLUSION: Routine clinical use and sterilization can induce detectable surface modifications in reciprocating NiTi instruments. Three-dimensional FE-SEM analysis provides a clinically relevant approach for assessing functional surface evolution under actual treatment conditions.