Mechanical Properties and Metallurgical Features of New Green NiTi Reciprocating Instruments

Abstract

To evaluate the properties of two nickel–titanium (NiTi) reciprocating endodontic instruments (commercially known as Procodile and Reziflow), a total of 40 size 25 and 0.06 taper new Procodile and Reziflow instruments (n = 20) were subjected to cyclic fatigue tests (60° angle of curvature, 5-mm radius) at 20 °C and 37 °C and a torsional test based on ISO 3630-1. The fracture surface of each fragment was examined. The morphological, mechanical, chemical, thermal, and phase composition characteristics of the files were investigated by field-emission gun scanning electron microscopy (FEG-SEM) equipped with an energy-dispersive X-ray (EDX) detector, focused ion beam analysis (FIB), micro-Raman spectroscopy, X-ray diffraction (XRD), differential scanning calorimetry (DSC), and Auger electron spectroscopy (AES). Reziflow showed higher cyclic fatigue resistance than Procodile at 37 °C (p < 0.05). The maximum torsional strength of Procodile was lower than that of Reziflow (p < 0.05). No difference was found between their angular rotations to fracture (p > 0.05). SEM, FIB, Micro-Raman, and AES analyses revealed the presence of an Nb/Nb2O5 coating on the Procodile surface. DSC and XRD analysis confirmed that both files consist of an almost austenitic phase structure at 37 °C. The cyclic fatigue resistance of Procodile and Reziflow significantly decreases upon exposure to body temperature.

Effect of body temperature on the cyclic fatigue resistance of the nickel”titanium endodontic instruments: A systematic review and meta-analysis of in vitro studies

“…A total of 21 studies met the criteria for inclusion. [ 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 ]…”

“…The studies revealed differences in the test model type, radius of curvature, angle of curvature, and immersion media. [ 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 ] The distance of the curvature from the tip, the fit of the instrument, angle of insertion, and length of the instrument inserted were not mentioned in all the studies [ Table 1 ].…”

Metallurgical Tests in Endodontics: A Narrative Review

“…Micro-Raman spectroscopy and focused ion beam analysis were methods used to investigate the surface of NiTi instruments to assess the presence of surface layers or coatings. In the endodontic literature, there were only four studies that used micro-Raman spectroscopy and two studies that used FIB analysis in their methodology, and all of these were published by the same research group [ 22 , 26 , 28 , 44 ].…”

“…Auger electron spectroscopy is a through-thickness method that is based on ion bombardment. It is able to evaluate the chemical composition of the alloy in the surface layers, up to a depth of a few micrometers, in contrast to FIB/SEM and micro-Raman analyses [ 26 ].…”

Experimental Study of the Effects of Torsional Loading on Three Types of Nickel-Titanium Endodontic Instruments

“…Numerous studies have approached various aspects regarding the behavior of endodontic instruments, including the influence of lubricants on torsional loads [27], metallurgical features [28], comparison between manual instruments and NiTi files [29], influence of heat sterilization procedures [30] or of surface design [31]. During root canal preparation, endodontic instruments are exposed to torsional and flexural stresses, the former for straight root canals and the latter for curved ones [32].…”