Abstract: Objective To compare the ability of singlevisit RCT and 2visit RCT to remove bacteria in infected root canal. Methods There were 100 patients with chronic periapical periodontitis who were randomly divided into singlevisit group and 2visit group. Bacteria culture was taken before and after the root canal preparation(or after disinfection). The change of colony number before and after the preparation of two groups was compared. The sample after preparation(or after disinfection) was taken, DNA was extracted from bacteria, PCR was amplified, and the sequence was detected to identify bacterial species. Results Comparing the amount of bacteria of singlevisit group(after preparation)with 2visit group(after disinfection), the difference was not statistically significant. There was no significant difference between the two groups in Streptococcus oralis, Lactobacillus acidophilus, Enterococcus faecalis, Actinomyces naeslundii, Peptostreptococcus anaerobius, and Prevotella intermedia (P>0.05). However, the detection rates of the Fusobacterium nucleatum and Porphyromonas gingivalis in 2visit groups were higher than those in singlevisit group, and the difference was statistically significant (P<0.05). Conclusion 2visit RCT cannot reduce the number and species of bacteria significantly. There is no significant difference between two methods.

Key words: single-visit RCT, 2-visit RCT, bacteria