A study on the influence of Ni–Ti M-Wire in the flexural fatigue life of endodontic rotary files by using Finite Element Analysis

Abstract

The aim of this paper is to analyze the cyclic performance of two different Ni-Ti endodontic rotary files made from different alloys under bending using Finite Element Analysis (FEA).When experimentation is not available, this is not a trivial task and most papers on the subject rely on static analysis only. Two Ni-Ti rotary instruments are selected, ProFile GT and a GT Series X (GTX). The latter file is made from M-Wire, which has been thermo-mechanically processed to have larger flexibility, according to its manufacturer. The mechanical response was studied by considering different scenarios in the FEA package, in which the material properties were introduced according to existing literature. The method and results are presented and discussed so that this paper can be used as a guideline for future works.Although not fully reflective of the instrument's behavior in a dynamic rotation intra-canal system, the models used constitute a good approximation when a comparison between two instruments is at stake. It is shown that the GTX file has a lower risk of fatigue fracture during its clinical use when compared to the GT file, especially when the root canal makes the file deform into an extreme geometry. However, if the root canal does not make the file deform more than a certain amount, the GT file is equally good from the point of view of mechanical endurance.

Finite Element Study on Continuous Rotating versus Reciprocating Nickel-Titanium Instruments

“…The results obtained from FEA agree with previous studies by Montalvao et al (22)(23)(24) when they compared mechanical properties of Profile GT (conventional NiTi) and GTX (M-Wire) using FEA and their results showed that GTX is more capable of stress relief than the GT file. Therefore, M-Wire instruments displayed better wear resistance due to higher hardness compared to conventional NiTi instruments.…”

Metallurgical effect on the mechanical behavior of rotary endodontic files using finite element analysis

“…The mechanical properties of the NiTi alloy affected by the phases present; thus, thermomechanical treatments consider a modern technique of developing new endodontic instruments with improved mechanical properties (Santos et al 2016). When bending test was performed, NiTi file model showed the greatest flexural rigidity, and the lowest displacement; this was in full agreement with Montalvão et al (2014). The lowest stress value and the maximum displacement was related to R-phase file model during the bending simulation, which indicates a superior flexibility of this alloy.…”

“…For CM file, model data were extracted from the stress-strain relationships determined by Zhou et al (2012) for the 48 CM-wire tested at room temperature. The material properties for M-wire file model are obtained from the stress-strain relationships found in the literature (Montalvão et al 2014). The parameters used to describe the model of the R-phase file superelastic NiTi were derived from stress-strain curve determined by Santos et al (2016).…”

Enhancement of NiTi superelastic endodontic instruments by TiO2 coating

“…The failure of the instrument can sometimes prevent the correct chemomechanical preparation and impede the complete disinfection of the root canal [4]. Rotary NiTi files can fail by two mechanisms: excessive torque, and flexural fatigue [5][6][7][8]. Torsional overloading can be avoided by limiting the maximum torque applied to the instrument and by controlling the apical force used by the practitioner.…”

“…NiTi endodontic instruments are susceptible to this kind of failure, and it is a common belief that the high concentration of surface defects generated during machining the instrument into its final shape is related to the failure process, with the machining defects acting as crack nucleation sites [10]. With this in mind, some manufacturers have employed thermal treatment [6,7], electrochemical polishing [11] and/or electrical discharge machining (EDM) [12] to generate a smoother surface, aiming at improving the fatigue life of the file. Improvements up to 700% were achieved for some instruments manufactured using the EDM process.…”