Effect of cyclic torsional preloading on cyclic fatigue resistance of ProTaper Next and Mtwo nickel—titanium instruments

  • Eugenio Pedullà | eugeniopedulla@gmail.com Department of Surgery, University of Catania, Catania, Italy.
  • Fabio Lo Savio Department of Industrial Engineering, University of Catania, Catania, Italy.
  • Gianluca Plotino Department of Endodontics, ‘Sapienza’ University of Rome, Rome, Italy.
  • Nicola Maria Grande Department of Endodontics, ‘Sapienza’ University of Rome, Rome, Italy.
  • Silvia Rapisarda Department of Surgery, University of Catania, Catania, Italy.
  • Gianluca Gambarini Department of Endodontics, ‘Sapienza’ University of Rome, Rome, Italy.
  • Guido La Rosa Department of Industrial Engineering, University of Catania, Catania, Italy.

Abstract

Aim: To evaluate the influence of different torsional preloads on cyclic fatigue resistance of endodontic rotary instruments made by conventional nickel—titanium (NiTi) or M-Wire. Methods: Eighty new Mtwo (#25/0.06) (Sweden & Martina, Due Carrare, Padova, Italy) and ProTaper Next X2 (Dentsply Maillefer, Ballaigues, Switzerland) were used. The Torque and distortion angles at failure of new instruments (n = 10) were measured and 0% (n = 10), 25%, 50%, and 75% (n = 20) of the mean ultimate torsional strength as preloading condition were applied according to ISO 3630-1 for each brand. The twenty files tested for every extent of preload were subjected to 25 or 50 torsional cycles (n = 10). After torsional preloading, the number of cycles to failure was evaluated in a simulated canal with 608 angle of curvature and 5 mm of radius of curvature. Data were analyzed using 2-way analysis of variance. Scanning electron microscope (SEM) was performed to evaluate the fracture surface of each fragment. Results: ProTaper Next X2 reduced their cyclic fatigue after 25 or 50 cycles of every torsional preloading (25%, 50%, and 75%) (P < 0.01). Cyclic fatigue of Mtwo was reduced by 50 cycles of every torsional preloading and only after the 75% of preload for 25 cycles (P < 0.01). Conclusions: Torsional preloads reduced the cyclic fatigue resistance of M-wire and conventional (as ProTaper Next and Mtwo) NiTi rotary instruments except for Mtwo with 25% or 50% of torsional preloading.

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Keywords:
Cyclic fatigue resistance, Torsional preload, NiTi fracture, M-wire, Torsional fracture
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How to Cite
Pedullà, E., Lo Savio, F., Plotino, G., Grande, N. M., Rapisarda, S., Gambarini, G., & La Rosa, G. (1). Effect of cyclic torsional preloading on cyclic fatigue resistance of ProTaper Next and Mtwo nickel—titanium instruments. Giornale Italiano Di Endodonzia, 29(1), 3-8. https://doi.org/10.32067/gie.2015.29.01.03