Efficacy Of Er:YAG Laser Against Enterococcus Faecalis Within Infected Lateral Canals Simulated In Vitro

Objectives:The model of enterococcus faecalis infection was established by artificial lateral canals,and the sterilization effect of Er:YAG laser on enterococcus faecalis in the lateral root canal was discussed,which provided certain reference basis for clinical use of Er:YAG laser for root canal sterilizationMethods:1.Sixty-six freshly extracted single permanent teeth from the maxillofacial surgery clinic of tianjin stomatological hospital were collected,and the inclusion criteria were as follows:1.Anterior teeth or lower premolars;2.Complete root development,no apical absorption and no calcification of root canal;3.Complete teeth,no pulp treatment,no filling body or prosthesis;4.The tooth root bending is10°or less(Schneider,s method),the root grew up in is equal to 12 mm.Ultrasonic instruments and periodontal cutters were used to remove the periodontal membrane and the carborundum disc crown behind the calculus.Root canal preparation was conducted routinely,and 8#K file(the tip diameter of the file was 0.08mm)was used to prepare the lateral root canal at 3,6 and 9mm from the root tip on both sides of the buccal tongue of the root.2.Recover the enterococcus faecalis strains under the condition of normal temperature,inoculate it on blood Agar plating and culture it in 37℃constant temperature incubator for 24 h.Select 2-3 enterococcus faecalis colonies by oese and inoculating and culturing them in BHI liquid medium in 37℃constant temperature for 24 h.Adjust the bacteria liquid concentration to 1 x10~8cfu/ml.Establish an isolated enterococcus infection model which is uesd to simulate the lateral root canal.3.Divide the experimental teeth randomly into 4 groups,with 15 teeth in each group.Group A:giving treatment of adding Er:YAG laser+5.25%NaCLO+normal saline;Group B:giving treatment of adding 5.25%NaCLO+normal saline;Group C:giving treatment of normal saline.The treatment time of each group is 120s.Group D:giving non-treatment as control group.After treatment,put all the group teeth immediately in the dentin debris of each simulated lateral branch for 24h bacterial culture and observe the growth of colonies.Results:According to the analysis of the colony count results of enterococcus faecalis,the difference of bacterial concentration between different groups was statistically significant,the clearance rate of enterococcus faecalis in the lateral root canal of group A was significantly higher than that of group B and C,with statistically significant difference(P<0.05).For the bacteria in the lateral canals at different locations,Er:YAG laser showed good sterilization effect for the bacteria,with no statistical difference(P>0.05).Conclusion:Er:YAG laser has a good killing effect on enterococcus faecalis at the lateral root canal,which can be used as an effective tool for root canal disinfection in clinical diagnosis and treatment.