Fatigue resistance of rotary instruments manufactured using different nickel–titanium alloys: a comparative study

Abstract

The aim of this study was to investigate whether cyclic fatigue resistance is increased for Controlled Memory (CM) Nickel-Titanium (NiTi) instruments, compared to instruments produced using traditional NiTi and instruments produced using M-Wire alloy. Two groups of NiTi endodontic instruments consisting of identical instrument sizes (constant 0.06 taper and 0.25 tip diameter and constant 0.04 taper and 0.40 tip diameter) were tested: group A compared Hyflex™ CM, Vortex ™ and ProFile ™ size 25 and 0.06 taper and group B compared Hyflex™ CM, Vortex™ and ProFile™ size 40 and 0.04 taper. 10 files from each different subgroup were tested for cyclic fatigue resistance. Mean and standard deviations of the Number of Cycles to Failure (NCF) were calculated for each group and data were statistically analysed (p < 0.05). Hyflex™ CM instruments, size 25 and 0.06 taper, and size 40 and 0.04 taper, showed a significant increase in the mean number of cycles to failure when compared with size 25 and 0.06 taper Vortex™ and ProFile™. No statistically significant difference (p > 0.05) was noted between Vortex™ and ProFile™ in the tested sizes. The new manufacturing process involving memory shape heat treatment produced new NiTi rotary files (Hyflex™ CM) significantly more resistant to fatigue than instruments produced with other proprietary methods of treatment (Vortex™) and with the traditional NiTi grinding process (ProFile™).

Comparison of the Cyclic Fatigue Resistance of 5 Different Rotary Pathfinding Instruments Made of Conventional Nickel-Titanium Wire, M-wire, and Controlled Memory Wire

“…Our results showed that the HyFlex GPF instrument had the highest NCF. This finding might be attributed to the previously stated factors, and the most likely one is the differences in the manufacturing process (control memory wire) used to produce the HyFlex GPF instrument, which is in agreement with previous studies (13,(28)(29)(30). In the present study, all the tested instruments have square cross sections, with the exception of the G-Files.…”

Cyclic Fatigue Resistance of Rotary NiTi Instruments after Simulated Clinical Use in Curved Root Canals

“…Unlike common fatigue tests that impose the flexure in artificial canal shapes (24), cyclic fatigue apparatus test allows a precise control over how a file is loaded during the test. This precise control can help standardizing fatigue performance testing, and predicting the fatigue lifetime of NiTi rotary instruments (23).…”

Comparación in-vitro de la resistencia a la fatiga cíclica entre dos sistemas rotatorios de níquel-titanio para crear el Glidepath: Proglider y Pathfile

“…Se necesita un mínimo de 640 ºC para completar la transformación de martensita a austenita, esto es, para que se produzca la no deseada recristalización (22,27,31,32). De ahí que cualquier proceso de mecanizdo adicional afecte a la temperatura de transición (18,22,25,33).…”

“…Los tipos de fractura de los instrumentos rotatorios de NiTi se clasifican en fatiga cíclica y fatiga torsional (18,19,33,35,36). La fatiga cíclica de un instrumento es aquella que ocurre como consecuencia de la alternancia de ciclos de tensión-compresión, los cuales son generados en el punto de máxima flexión del instrumento cuando rota libremente en el interior de un conducto curvo.…”

“…Esto es, desde las primeras Profile (42,54) en las que el alambre puro de Nitinol SE508 se sometía a templado en frío y después se pasaba por termociclado bajo presión para posteriormente fabricar el instrumento mediante un proceso de fresado (grinding), este proceso se ha usado para fabricar otros sistemas como Protaper, K3, RaCe, GT y Flexmaster entre otras (54). Más adelante, en 2007 nace la aleación M-Wire (Dentsply Tulsa Dental Specialities), resultado de elaborar el alambre de nitinol en bruto bajo una tensión específica y unos tratamientos térmicos a diferentes temperaturas, resultando un material que incluye una parte tanto en fase martensítica como fase R premartensítica manteniendo su estado pseudoelástico (18,33,54). De esta aleación son ejemplos las limas Profile GT Series X, Profile Vortex , Vortex Blue y una de las que nos ocupa en este estudio, la lima ProGlider.…”