FINITE ELEMENT ANALYSIS OF STRESS DISTRIBUTION ON CANAL WALLS WHILE PREPARATION OF CURVED CANALS

Objective: The aim of this study is to determine stress evaluation of root canal wall during shaping curved canals with ProTaper and HeroShaper systems by using three-dimensional finite element analysis. Methods: The geometries of the ProTaper Universal and HeroShaper Ni-Ti rotary systems' selected files were created using three-dimensional finite element modelsThe three-dimensional FEA model within a curved canal was established by integrating a simulated canal and natural tooth. A micro-focus CT scanner was used to scan the models. After integration and modification a final three-dimensional model with a smooth surface and mostly centered canal was established. The stresses on the instrument during simulated shaping of a root canal were analyzed numerically by using a three-dimensional finite element package, LS-DYNA, taking into account the nonlinear mechanical behavior of the nickel-titanium material. Stress distribution in the instruments and the canal walls was recorded during simulated shaping. Results: With ProTaper file system, stress concentrations were determined towards the outer aspect of the curvature in the apical portion of the canal but in HeroShaper system stress was more concentrated in the middle portion of the canal and were less than ProTaper model. Conclusion: HeroShaper files cut more efficiently and generated less stress on the canal walls than ProTaper files because of their possitive rake angle. It was observed that there was stress concentration towards the outer aspect of the curvature in the apical portion of the canal with the ProTaper file system. This shows us that these files are more feasible for apical transportation.