Document Type

Article

Publication Date

Summer 5-2-2024

Abstract

Introduction: Nickel–titanium instruments annually undergo improvements to enhance the cyclic fatigue

lifespan, especially with challenging canals. This study examines RACE EVO instrument in an S‑shaped

double‑curvature canal in different angles of insertion 0°, 20°, and 40° to investigate the behavior of the

heat‑treated instruments in challenging canals.

Materials and Methods: A total of 30 instruments were assigned to three groups (Group 0°, Group 20°, and

Group 40°). RACE EVO instruments were tested in artificial canals. The canals had two curvatures: an apical

one which its parameters are 70° angle and 2 mm radius and a coronal one which its parameters are 60°

angle and 5 mm radius. The test was done using a cyclic fatigue apparatus. A statistical study was done by

one‑way analysis of variance groups, and Tukey’s honestly significant difference/Tukey–Kramer with a level

of significance (α) was adjusted to 0.05.

Results: The time until failure was reduced by the increase in the angle of insertion; however, Group 20° and

Group 40° were not significantly different. All the instruments were broken apically. The scanning electron

microscopic analysis showed typical characteristics of cyclic fatigue failure.

Conclusions: Increasing the inclination during the insertion reduced the resistance of the RACE EVO

instruments to cyclic fatigue failure despite the surface heat treatment of the instrument.

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