Three-dimensional dynamic modeling of rotary nickel-titanium endodontic instruments used in root canal preparation

Ni-Ti rotary instruments which are frequently used in root canal shaping, can occasionally break in root canals. These unpredictable fractures in instruments weaken the tooth structure and this situation significantly reduces the success of root canal treatment. By making improvements to the geometric design of instruments, we can make it better the bending, torsion and fatigue resistance to which they are exposed. In this study, the stress, deformation and fatigue life of the file during root canal treatment were modeled with the finite element method. In finite element analyses, solutions were realized under dynamic modeling conditions by taking into account the rotation and translation movement of the instrument. In the study, four different file cross-sections, three different root canal curvature angles and two different pitches were taken into consideration. The results obtained showed that files with convex triangular cross-sections were subjected to less stress and that files with this cross-section had higher fatigue life. In addition, the increase in the angle of curvature in the root canals adversely affects the fatigue life of the insturements. Therefore, it was concluded that the treatment in root canals have high curvature should be carried out much more carefully. In adition, it has been determined that increasing the file pitch increases the maximum stress and accordingly reduces the life of in the instruments.