Irrigation of the root canal with antibacterial solutions is indispensable during root canal treatment in order to remove biofilm, tissue remnants and dentin debris from the root canal. Nonetheless, still 50% of the root canal treatments fail as a consequence of poor cleaning. Ultrasonic activation of the irrigant has been shown to dramatically increase cleaning efficiency. A full understanding of the fluid dynamical action of the activated fluid is crucial for the improvement of treatment success. Previous experimental approaches have failed to provide complete insight into this procedure, due to the difficult temporal and spatial scales of the flow and the geometrical complexity of the root canal. The objective of this proposal is to employ Computational Fluid Dynamics simulation in order to study the ultrasonic activation of the irrigant in the root canal. A combined Endodontology - Fluid Dynamics approach is proposed. The researcher has introduced the use of Computational Fluid Dynamics to the field of Endodontology and has been recently awarded a Doctorate Degree. He will move from his home institution (Dept. Endodontology, Thessaloniki, Greece) to a world leading group in Fluid Dynamics, biomedical and micro-fluidics applications (Physics of Fluids Group, Enschede, The Netherlands). The researcher will acquire additional experience with numerical simulation of flows inside micro-channels as well as experimental high-speed imaging techniques, which will be used for the validation of the computer model. Following successful completion of this fellowship, he will become able to lead his own scientific group on biomedical engineering in the future.