Stress distribution and axial force under different filing parameters during root canal preparation: An in vitro FEA and experimental study.

Abstract

Inappropriate rotational and feed speed of the rotary nickel-titanium (Ni-Ti) file can cause damage to the root canal wall. Consequently, it is essential to examine the relationships among filing parameters, file stress, and axial force to establish a dependable foundation for the selection of parameters. A 3D reconstruction of the tooth is executed utilizing CBCT images. The reaming rate of root canal filling is established at 30 % to examine the correlation between Root Canal Preparation (RCP) parameters and damage under critical situations. Utilizing the elastic-plastic model and the Johnson-Cook intrinsic model, the explicit dynamics method of ABAQUS software is employed to simulate the contact stress and axial force at varying feed speeds (1-8 mm/s) and rotational speeds (150-800 rpm). A robotic arm-based filing experimental platform is developed to conduct bionic experiments, which examine the variation of axial filing force with different parameters, and these results are compared with simulation outcomes. Increased rotational speed and decreased feed speed of the root canal file can diminish the stress and strain on the root canal. The trends and magnitudes of axial force derived from simulation and experiment at varying speeds are comparable (deviation factor = 0.15 %-25.82 %). A rotational speed higher than 350 rpm and a feed speed lower than 6 mm/s are more conducive to stable and safe filing, and the maximum axial force and the maximum stress exhibit a trend analogous. This study provides a basis for the selection of filing parameters for manual and robot-assisted RCP, thereby improving the safety of clinical preparation.