Abstract: Abstract：　Objective　 This study was designed to compare the clearning efficiency between shock wave enhanced emission photoacoustic streaming (SWEEPS) and Passive Ultrasonic Irrigation（PUI）Methods　250 single premolar from freshly extracted human were collected, the smear layers were removed. After sterilization, the model of E.faecalis infection was established in vitro. Samples were randomly divided into 6 groups(n=40) respectively, SWEEPS-Er:YAG laser with 3% NaOCl, SWEEPS-Er:YAG laser with 0.9% normal saline, PUI with 3% NaOCl , PUI with 0.9% normal saline as the experimental group, 3% NaOCl group and 0.9% normal saline group were the control groups. After irrigation, the bacterial clearing effectiveness were qualitatively observed through a scanning electron microscope, and the rate of bacterial reduction was quantitatively determined by the plate bacterial counting method, and all data were statistically analyzed by a Mann-Whitney U test. Results　 The amount of E.faecalis was significantly decreased in SWEEPS+NaOCl group, SWEEPS+NS group, PUI+NaOCl group, PUI+NS group and 3% NaOCl group (P < 0.05). The difference between the each two groups was statistically significant (P < 0.05). The efficiency of bacterial reduction was SWEEPS+NaOCl group > SWEEPS+NS group > PUI+NaOCl group > PUI+NS group > NaOCl group > NS group. Conclusions　 The clearning efficiency of SWEEPS-Er:YAG irrigation was significantly better than that of Passive Ultrasonic Irrigation.

Key words: SWEEPS-Er:YAG laser, Passive Ultrasonic Irrigation, root canal Irrigation, Enterococcus faecalis biofilm