Finite Element Design Optimization by Doe Technique of the Torsional Stress Behavior for Niti Rotary Endodontic Instruments

Abstract

Nickel-Titanium (NiTi ) rotary endodontic instruments are fundamental in modern dentistry, as the greater mechanical properties and flexibility make the treatment of the root canal faster and more effective. The present study deals with an analysis of the mechanical behaviour of the NiTi endodontic instruments during the application of torsional stresses, through a finite element simulation model. The model simulates the interaction of rotary endodontic instruments within a curved conical canal, focusing on the impact of various geometric parameters. Key factors such as the cross-section, the pitch and the taper have been analysed to discern their influence on the mechanical performance of the instrument. Subsequently, a topological optimization was made to customize the design in order to improve the performance’s instrument under torsional stress. The investigation revealed a significant correlation between the polar moment of inertia of the resistant section and the stifness of the instrument. Through the variation of taper and pitch, individually or in combination, it was possible to identify ranges of parameter values for the definition of more flexible or more rigid behaviour. In particular, it was observed that lower taper increases the flexibility of the instrument, while a higher pitch increases flexibility.