Group1:2%Sodium hypochlorite ultrasonic irrigation+17%EDTA Group2:2%Sodium hypochlorite ultrasonic irrigation+17%EDTA+PDT Group3:1%Sodium hypochlorite ultrasonic irrigation+17%EDTA+PDT Microbiological measurement. Filled with sterile PBS, the root canals were sampled immediately before and after the disinfection procedures.