Aplicação do método dos elementos finitos na análise do comportamento mecânico de instrumentos endodônticos de níquel-titânio

Abstract

The mechanical behavior of different nickel-titanium rotary endodontic instruments was evaluated using the finite element method. Mtwo 25/.06, RaCe 25/.06, ProTaper Universal S2 and F1 and Hyex 30/.06 instruments were scanned by computed micro tomography aiming to obtain the tridimensional models of their geometries. The boundary and loading conditions were chosen based on the specification ISO 3630-1, for bending and torsion tests of endodontic instruments. A specific subroutine for superelastic materials was used to describe the behavior of the material. A comparison among the numerical and experimental results was performed for Mtwo, RaCe, ProTaper Universal S2 and F1 instruments. The good agreement between simulation and experiment indicated the accuracy of the numerical models used in this work. Based on the results, ProTaper Universal F1 instrument was the least exible, presenting a maximum stress of 1,185 MPa when bent until 45º. Onthe other hand, ProTaper Universal F1 instrument presented the highest torsional strength. The behavior of the Mtwo instrument under bending presented a strong relationship between the orientation of the cross-section and the direction of the bending load, showing that other geometrical parameters of the cross-section, such as the symmetry, must be considered than just the second moment of inertia. Hyexinstrument's behavior was evaluated using different materials: superelastic nickeltitanium, martensitic nickel-titanium and stainless steel. The results indicated that the instrument made of martensitic nickel-titanium is the most exible and, probably, the most fatigue resistant.