Effect of Periodic Changes in Rotation Speed on Torsional Stress and Screw-in Force by Alternative Rotation Technique

초록

Introduction: This study evaluated the effect of periodic changes in rotation speed on torsional stress and screw-in force using the dedicated alternative rotation technique (ART) motion of the EQ-M (Metabiomed, Cheongju, Korea) endodontic motor. Methods: Two ART modes of the EQ-M motor in 2 alternative techniques (ART30 and ART50) and continuous rotation were compared using ProTaper Next X2 (Dentsply Sirona, Charlotte, NC) files and simulated resin blocks (n 5 12 per group). ART30 and ART50 were operated by continuous rotation of 350 rpm for 360 & DEG; and then rotated at 30% increased speed from the base speed for 180 & DEG; and at 50% increased speed for 180 & DEG;, respectively. Before the test, the simulated resin blocks were pre-enlarged using ProTaper Gold S1 and S2 (Dentsply Sirona) and fixed on a metal stage connected to the force-and torque-measuring unit. During shaping the simulated canal in an automatic up-and-down manner, the parameters of maximum torque, sum of torque, maximum screw-in force, and maximum apical force were measured. The data were statistically analyzed using 1-way analysis of variance and the Tukey post hoc com-parison test at the 95% significance level. Results: The ART30 and ART50 groups showed a lower maximum torque, sum of torques, screw-in force, and apical drive force than the continuous rotation group. There was no significant difference between the ART30 and ART50 groups (P . .05). When the screw-in force increased suddenly, the torque corre-spondently increased. Conclusions: Under the limitations of this study, the ART mode could reduce the torsional stress and apical forces of the screw-in during instrumentation in com-parison with continuous rotation. (J Endod 2023;49:77-82.)

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