File wear analysis of root canal treatment in simulated root canals – A vibrational and high-speed imagery approach

Abstract

A typical root canal treatment involves − cleaning, shaping, and enlarging the root canals. In RCT, the probability of defects related to file fatigue and failure is high. This study aims to investigate the vibrations generated during root canal preparation of simulated root canals using a triaxial accelerometer. Experiments are conducted systematically until file failure, and each failure time analyzed from the raw data. Denoising of vibration signals was done by SWT (coif3 mother wavelet). Finally, statistical parameters were extracted from the raw data to find correlations between successive file runs for each block used for root canal preparation. The vibrational signals upon denoising reveals that the amplitude of vibration is found to be highest in the curved sections of the canals which ultimately leads to the fatigue failure of the WOG files. The root cause assessment for the WOG file failure dealt with high-speed imaging and FESEM assisted fractography analysis The high-speed imaging in a backlit system revealed an unwinding of WOG files before fatigue failure. This provided evidence to support unwinding of files prior to fracture which typically occurred in the curved section of the acrylic block. Furthermore, discernments into the modes and mechanism of failure are provided via FESEM of the failed file fragments. The fracture morphology reveals a combinational fatigue failure as unwinding, crack initiation and propagation coupled with micro void formation and coalescence due to torsional shear and bending stresses. Overall, this study provides insights into the real-time monitoring and prediction of failure of endodontic files which can aid in devising strategies in preventing accidents during a typical RCT.