Endodontics Irrigation: A Computational Fluid Dynamics Approach

Root canal system cleaning and disinfection is one of the most important steps to achieve endodontic treatment success. Mechanical preparation besides cleaning allows root canal irrigation to reach deeper and inaccessible areas to this mechanical preparation in the root canal system. Using chemical active substances, root canal irrigation tries to provide a chemical action along the root canal system but also a mechanical action where it removes the debris along it through the flow it creates. The effectiveness of this is quite related to the anatomy of the root canal system, the more complex it is the more difficult is to obtain this cleaning and disinfection. Mesial roots of lower molars are one of the examples where this kind of complex anatomy can be present in a high percentage, namely with the presence of isthmuses that aren't most of the time mechanically prepared and are trusted to be disinfected and cleaned only by root canal irrigation. Side vented needles are used mainly for safety reasons, to avoid irrigant extrusion through the foramen, however, due to their lateral exit tip, they can be more prone to deliver the irrigant in complex anatomic areas of the root canal system, such as lateral canals or isthmuses compared to flat ended needles. The aim of this study was to evaluate the flow created with a 30G side vented and a 30G flat-ended needle in a Vertucci type II canal with the presence of an isthmus using computational fluid dynamics. Two domains were used and compared in terms of flow pattern. In both root canal was obtained from a mesial root of a mandibular molar, scanned by computed tomography (CT) providing a three-dimensional object that was exported to the computer-assisted design (CAD) software. A CAD model of a 30G side-vented irrigation needle and a 30G flat-ended needle were created, placed 3mm from the apical foramen and subtracted to the root canal providing two different domains for the two different needles but the same anatomy. The flow pattern obtained shows that flat ended needles provide a more favorable result in terms of what is expected from the mechanical objectives of irrigation.