Comparative evaluation of bending property and torsional resistance of three nickel–titanium files: A finite element analysis

Aims: We aimed to investigate the effect of instrument length on the torsional resistance and bending property of three nickel–titanium files, namely ProTaper Gold (PTG), ProTaper Next (PTN), and HyFlex CM (HCM) using finite element analysis. Materials and Methods: Three-dimensional models of each aforementioned system were created using the computer-assisted design (CAD) software SolidWorks® 2016 (Dassault Systèmes, SolidWorks Corp., Concord, MA, U. S.). Then, all models were imported to the ANSYS® Workbench 16 (Canonsburg, PA, U. S.) where the simulation was computed. The boundary conditions used to simulate the behavior of the endodontic instruments were in compliance with the ISO 3630 1 specification standards. Results: It was observed that in bending test, HCM model exhibited load of 510.35 MPa with displacement of 6.05 mm, followed by PTG model (465.48 MPa) and 11.21 mm displacement, then PTN file model (440.74 MPa) and 10.30 mm displacement, whereas in torsional test the rigidity curve for HCM file (1.9673 N mm/Radian) lies much below PTG (6.4615 N mm/Radian) which clearly shows that HCM is flexible as compared to PTG and PTN. Conclusion: Considering the high flexibility of the HCM file, it can be effectively used in severely curved root canals and PTG and PTN files in moderately curved root canals. It was also recommended that HCM files should not be kept in canals for a longer time because stresses might reach to ultimate level quickly which can cause fracture.