Different Means Of Disinfection Against Enterococcus Faecalis In Root Canals In Vitro

Objective: The purpose of this in-vitro study was to compare the disinfection effect against biofilms of Enterococcus faecalis in root canals when 3%Na Cl O irrigation, PDT or the combination of 3%Na Cl O irrigation and PDT was used; and to investigate the disinfection characteristic of 3%Na Cl O irrigation and PDT in different parts of the root canal.Methods: Thirty-two human single-canal mandibular premolar teeth were selected to build models of root canals infected by Enterococcus faecalis.The tooth specimens were randomly and averagely divided into 4 groups and treated as bellow, Group A: blank control, Group B: treated with 3%Na Cl O irrigation, Group C: treated with PDT, Group D: treated with the combination of 3%Na Cl O irrigation and PDT. Then the tooth specimens were split longitudinally into buccal and lingual halves, and low speed burs were used to collect dentine shavings 2mm, 6mm and 10 mm away from the apical termination of each half. These dentine shavings were mixed with tryptic soy broth and incubated for six hours to enrich the number of surviving bacteria. The bacterial suspensions were later serial diluted and plated on tryptic soy agar plates to enumerate the CFUs after forty-eight hours incubation at 37 ? in anaerobic conditions. The intergroup and intragroup statistical significances of CFUs were analysed using SAS9.13.Results: As with all parts of the root canal in aggregate, the CFUs of the group treated with 3%Na Cl O irrigation or PDT were significantly lower than those of the blank control group(p<0.05); the CFUs of the group treated with the combination of 3%Na Cl O irrigation and PDT were significantly lower than those of the group treated with 3%Na Cl O irrigation or PDT(p<0.05); there was no significant difference in CFUs between the group treated with 3%Na Cl O irrigation and the group treated with PDT(p>0.05). But as with the cervical part of the root canal, the CFUs of the group treated with 3%Na Cl O irrigation were significantly lower than those of the group treated with PDT(p<0.05). In the group treated with PDT, the CFUs in the cervical and middle part of the root canal were significantly higher than those in the apical part of the root canal(p<0.05).Conclusion: PDT was as effective as 3%Na Cl O irrigation in inactivating biofilms of Enterococcus faecalis, but was less effective than 3%Na Cl O irrigation in the cervical part of the root canal. PDT was less effective against biofilms of Enterococcus faecalis in the cervical and middle part of the root canal than those in the apical part. The combination of 3%Na Cl O irrigation and PDT showed the best disinfection effect against biofilms of Enterococcus faecalis in root canals.