ANALYSIS OF THE IMPACT OF RECIPROCATING MOTION ON TORSIONAL STRESS RELIEF IN SINGLE-FILE SYSTEMS: A LITERATURE REVIEW

Abstract

Chemo-mechanical preparation using nickel-titanium single-file systems aims to simplify endodontic treatment; however, torsional fracture remains a relevant complication. This integrative review analyzed the impact of reciprocating kinematics on dynamic torque generation, torsional stress, and resistance to torsional fracture in single-file endodontic instruments. A search was conducted in the PubMed database covering the period from 2021 to 2026, combining MeSH terms and text words. Of the selected studies, 12 comprised the main synthesis, and one additional study was used as complementary conceptual support. Data analysis showed that reciprocating kinematics reduces dynamic operative torque and attenuates screw-in peaks in curved canals through the periodic disengagement of cutting blades bound to dentin. However, changing the kinematics alone does not modify the instrument’s ultimate static torsional resistance, which is determined by the metal core mass in the apical third (D3), cross-sectional design, and heat treatment of the alloy. It was concluded that reciprocating motion effectively contributes to the temporary relief of torsional stress and the prevention of mechanical overload in curved canals, although it does not represent universal mechanical superiority over continuous rotation under static binding conditions.