Numerical Investigation of Irrigant Penetration Into Dentinal Microtubules

Abstract

Root canal irrigation is an important procedure in endodontic treatment. After mechanical preparation of root canal, NaOCl, which is the most common antibacterial irrigant, is inserted by special needles. This work helps to remove bacteria and debris and dissolves the organic tissues in the root canal. In the vicinity of the main root canal, there are a large number of microchannels attached to its wall named “dentinal tubules”. The success of irragation depends on the penetration of irrigant in these tubules, which results in killing the bacteria and preventing complexities after root canal therapy. There is rather limited earlier research on modeling of dentinal tubules. Nevertheless, it has been shown that the flow rate, insertion depth and needle types affect the flow pattern in the root canal. The concentration difference between inserted irrigant and the liquid filling the tubules is the main driving force for penetration. Diffusion of irrigant, however, is a time dependent process and should be analyzed as an unsteady problem. In prior studies, the geometry was considered as cylinders with a constant diameter of 2.5μm and the effect of tapering was neglected. In reality the diameter varies from about 2.5μm near the pulp to about 1.5μm at the distance of 1 mm from the pulp. In the present study, a more detailed and exact model of dentinal tubules geometry was considered. The computational fluid dynamics (CFD) is used for the modeling of flow and diffusion of irrigant as a function of time. The unsteady and 3D continuity and Navier-Stokes equations as well as a scalar transport equation are solved and the flow field and the concentration of antibacterial irrigant were evaluated. The simulation results were compared to the earlier works. It was shown that the use of the correct detailed geometry of tubules led to noticeable differences compared to those found for the idealized model.