Irrigant flow in micro-computed tomography scanned root canals using computational fluid dynamics model

Abstract

The aim of this study was to evaluate the irrigant flow pattern of a hypodermic needle; in Micro-Computed Tomography (MCT) scanned root canals prepared using Reciproc® files at two different levels using a Computational Fluid Dynamics (CFD) model. Two lower incisors prepared with Reciproc® rotary files sized R 25 and 50, underwent MCT scanning to create 3-dimensional root canal models. A computational model of a 30 G hypodermic needle was then positioned at 3 and 5 mm from the apex in each root canal model. Irrigant flow pattern, velocity and mean apical pressure at 1 mm from the apices were evaluated using commercial CFD software, Star CCM+. The irrigant produced a high velocity jet, reaching 5.8 m sec-1, at the needle outlet and created multiple vortices near the canal wall before exiting at the canal orifice. Mean apical pressure and velocity recorded for R 25/3 mm (7.77 kPa/0.235 m sec-1), for R 25/5 mm (4.34 kPa/0.001 m sec-1), for R 50/3 mm (7.89 kPa/0.005 m sec-1) and R 50/5 mm (4.49 kPa/0.0001 m sec-1). Close proximity of the needle to the apex produced higher mean apical pressure; meanwhile, larger apical preparation sizes produced lower velocity of irrigant. It was observed that within the same canal, irrigant flow patterns were similar for both needle levels. Needle positions and apical preparation sizes were found affecting the apical pressure and velocity. The CFD simulations in MCT scanned root canals were clinically significant.