Combining apical torsional load and cyclic fatigue resistance of NiTi instruments: New approach to determine the effective lifespan of rotary instruments
Australian Endodontic Journal
In the described proof-of-principle experiments, we introduced a novel testing device to investigate how different concurrent torsional loads influence the cyclic fatigue (CF) resistance of a nickel–titanium (NiTi) instrument. The device was designed to test CF resistance of NiTi files with a standardized load on the apical 5 mm; a movable cylinder controlled by a lever provided a uniform real-time load. Thirty-three NiTi instruments 25.04 (F360, Komet, Lemgo, Germany) were rotated until fracture at 30° curvature under three different torsional loads (n = 11 each); Group A: 2.5 Ncm; Group B: 5 Ncm; Group C: 10 Ncm. anova, multiple comparisons Tamhane tests, regression and Kaplan–Meyer analysis were performed to contrast means. Resistance to cyclic fatigue differed significantly among groups (P = 0.0001). Increased torsional loads led to a decrease in time to failure. An inverse correlation (r = −0.721, P = 0.001) was observed between time and torsional load, with higher torsional loads correlated to shorter times to fracture.
Gatto, M. R.,
Peters, O. A.
Combining apical torsional load and cyclic fatigue resistance of NiTi instruments: New approach to determine the effective lifespan of rotary instruments.
Australian Endodontic Journal, ,