The purpose of this thesis is to present the efficiency of irrigation within the apical part of the root canal of a human tooth, using computational fluid dynamics (CFD). Fluid dynamics is described by partial differential equations which may be transferred into a system of linear equations employing numerical methods to obtain an approximate solution. Endodontics, one of the dentistry branches, is briefly described and the theoretical foundations of fluid dynamics in the root canal of a human tooth are introduced. The apical vapor lock (AVL), which prevents the irrigant from passing to the apical third, is one of the major problems in endodontics. Reynolds Averaged Navier – Stokes equations and 𝑘 − ω SST turbulence model are described. Discretization of general conservation equation is presented. The root canal geometry of a human tooth was acquired using computed tomography. Irrigation needle used for simulating the irrigant flow was bevel open-end positioned at 90% of the working length (WL) of the root canal of a human tooth. Numerical analysis for different, clinically realistic, volume flow rates of the irrigant were performed. Results obtained by numerical simulations, with an emphasis on the root canal's apical third, are presented. Furthermore, control points, in which the pressure was measured and compared with the value of the interstitial tissue pressure, were set. The obtained results estimate the adequate application time of a certain volume of the irrigant into the root canal of a human tooth in order to preserve the periapical tissue and for the purpose of a quality irrigation procedure. The solver employed for all the simulations is ANSYS Fluent 20.