Background:The viscous environment caused by the rotation of Nickel-titanium (Ni-Ti) instruments in a static solution inside the root canal during mechanical preparation may increase the difficulty of endodontic debridement and the risk of instrument fatigue fracture. Therefore, this study aimed to investigate the effect of continuous flushing during up-and-down motion of instruments using a three-dimensional computational fluid dynamics (CFD) numerical model.
Results:After30s simulation,water entering the canal formed an "efficient replacement area" in upper part of the canal and transported to the apical part of the canal.Increasing the velocity and amplitude of the motion of the instrument caused less time of flushing water to reach the apical area; and the replacement of the original solution was primarily improved by increasing the amplitude.
Conclusions:Continuous flushing during up-and-down movement of the instrument significantly helped to rapidly replace the original solution with water at the coronal and middle part of the canal and dilutedthe viscosity of the original solution to some extend in the whole canal.It is therefore beneficial to add continuous water flushing to the instruments used in the preparation process.Furthermore, the amplitude of the movement in file’s up-and-down motion should be appropriately increased to improve its irrigation effect in clinical practice.