Numerical investigation of irrigant flow characteristics in curved root canals with computational fluid dynamics method

Abstract

This study aims to provide valuable insight into the irrigation in curved root canals with CFD method. Numerical simulation of the flow originated from a side-vented or an open-ended flat needle located in the prepared root canal with two different insertion depths was performed. The distribution of velocity, wall shear stress, apical pressure, and the detailed flow structures were all evaluated. The results show that both the side port of the side-vented needle and the curved portion of the target root canal tends to make circumferentially non-symmetric wall shear stress distribution and asymmetrical streamlines. However, the impact of the root-canal curvature variation on the flow pattern is apparent only when the open-ended flat needle was selected for irrigation or the needle was inserted into the curved part of the root canal. The insertion depth and the size of the gap between the outer surface of the needle and the root canal internal wall are critical to the apical pressure, except the former is simultaneously crucial for the micro-velocity zone decreasing. Overall, the optimal method for effective irrigation in a curved root canal is the side-vented needle with the same curvature to the root canal, deeper insertion, and reasonable gap size.