Study Examines NiTi File Endurance



Rotary files are essential to endodontic work. But everyday wear and tear can affect their performance, and failures during procedures can be dangerous. Accurate estimates of their endurance and lifespans are vital to their safe operation.

The finite element method (FEM) has been proposed for analyzing stress distribution in NiTi rotary instruments, but it has not been assessed for predicting the number of cycles to failure (NCF). Recently, researchers at Politecnico di Torino and the University of Turin Dental School in Turin, Italy, attempted to predict NCF and the failure location of NiTi rotary instruments by FEM virtual simulation of an experimental nostalgic fatigue test.

The researchers tested ProTaper Next (PTN) X1, X2, and X3 files from DENTSPLY Maillefer (n = 20) to failure using a customized fatigue testing device. Computer-aided design software replicated the device and file geometries. Computer-aided design geometries (geometric model) were imported and discretized (numeric model). The typical material model of an M-Wire alloy was applied. The numeric model of the device and file geometries were exported for finite element analysis (FEA).

Multiaxial random fatigue methodology was used to analyze stress history and predict instrument life. Experimental data from PTN X2 and X3 were used for virtual model tuning through a reverse engineering approach to optimize material mechanical properties. Tuned material parameters were used to predict the average NCF and failure locations of PTN X1 by FEA; t tests were used to compare FEA and experimental findings (P < 0.05).

Experimental NCF and failure locations did not differ from those predicted with FEA (P = 0.098). The researchers concluded that FEA may predict file NCF and failure location. Virtual design, testing, and analysis of file geometries could save considerable time and resources during instrument development, they noted.

The research, “Prediction of Cyclic Fatigue Life of Nickel-Titanium Rotary Files by Virtual Modeling and Finite Elements Analysis,” was published by the Journal of Endodontics. It was written by Alessandro Scattina, MS, PhD; Mario Alovisi, DDS; Davide Salvatore Paolino, MS, PhD; Damiano Pasqualini, DDS; Nicola Scotti, DDS; Giorgio Chiandussi, MS, PhD; and Elio Berutti, MD, DDS.

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