The evaluation of the effects of irrigation needle with different diameter on irrigant flow in the root canal by using computational fluids dynamics

The purpose of the root canal treatment is to eliminate the inflamed pulp tissue in the root canal, inflammatory products and microorganisms and then filling the root canal with a bio-compatible material. One of the most important factors affecting the success of the root canal treatment is an effective cleaning of the root canal. Cleaning the root canal is performed mechanically and chemically. Mechanical cleaning of the root canal is not enough alone because of the root canal complex configuration. Irrigation is the process of root canal physico-chemical cleaning with a variety of chemical solutions. Irrigation efficiency depends on the of the solution used contact ever in point of the root canal. In this study, human upper permanent central incisor without decay and restoration was used which were extracted for different reasons. After access cavity preparation root canal preparation was performed with Reciprocal system. Microcomputed tomography (Micro-CT) of the tooth root canal was obtained. Threedimensional modeling of the micro-CT image was made. Open ended beveled needle was used. Optical microscope and scanning electron microscope image (Scanning Electron Microscope SEM) of the needle which will be used in irrigation were taken. The outer and inner diameter sizes of needles were determined. Needles modeling were made by using these measurements on software. Needles were located 1 mm and 3 mm away from the root apex in a virtual environment. Distilled water was used as an irrigating solution. Computational fluid Dynamics (CFD) commercial software ANSYS Fluent .v14 was used to analyze the flow pattern of the irrigating fluid in the root canal. Flow pattern of the irrigating fluid was evaluated depending on the size and insertion depth of the needle. Results: For both needle sizes, the maximum speed in occurred in the central part of the needle lumen. The apical pressure at the apex was observed significant differences between the two needle sizes. For both needle sizes, the needle move away from the apex apical pressure decrease occurred. The shear stress occurring on the wall of the opening of the needle lower than the shear stress occurring in the wall on the opposite side. The maximum shear stress decreased as needles moved away from the root apex. Conclusions: Needle insertion depth has a significant impact on the irrigant dynamics in root canal irrigation. Needle size used significantly affect the irrigant flow in the root canal. Computational fluid dynamics is an important tool for studying the behavior of irrigation.