Comparative Study On Bactericidal Effect Of Two Different Kinds Of Laser On The Root Canal Of Enterococcus Faecalis Infection

Objective:In this experiment,two different lasers combined with different root canal irrigators were applied to the root canal model of Enterococcus faecalis infection in vitro.The effects of different combinations of disinfection methods on the Enterococcus faecium in different depths of the root canal were compared,aiming to provide experimental evidence for clinical work.Methods:A total of 70 intact maxillary anterior teeth extracted from Department of Stomatology of Shanxi Dayi Hospital from October 2015 to October 2017 were selected as study objects to prepare a model of enterococcus faecalis infection.Ten samples were taken before and after bacterial inoculation for SEM examination and microbial culture,to ensure the successful establishment of a sterile root model and an Enterococcus faecalis infection root model.The remaining 60 infected tooth root models were randomly divided into 6 groups of 10 samples（5 as the test group and 5 as the control group）.The remaining60 infective root models of Enterococcus faecalis were randomly divided into 6 groups of10（5 as experimental samples and 5 as control samples within the group）.The experiments were grouped as follows:Group A:Er:YAG laser+5.25%NaClO,Group B:Nd:YAG laser+5.25%NaClO,Group C:5.25%NaClO,Group D:Er:YAG laser+0.9%sodium chloride,E Group:Nd:YAG laser+0.9%sodium chloride,Group F:0.9%sodium chloride,laser parameters:Er:YAG laser（wavelength 2940nm,mode SSP,energy 20mJ,frequency15Hz,power 0.3W）;Nd:YAG laser（wavelength 1064nm,mode MSP,frequency 15Hz,power 1.5W）.They were respectively used to infect the root model of Enterococcus faecalis,and the bactericidal effects of different combinations of the methods of disinfection on Enterococcus faecalis at different dentinal tubules were recorded and compared.Results:1.Experimental results show:Group A（Er:YAG laser+5.25%NaCl O）,Group B（Nd:YAG laser+5.25%NaClO）,Group C（5.25%NaClO）,Group D（Er:YAG laser+0.9%Sodium chloride）and E group（Nd:YAG laser+0.9%sodium chloride）were superior to group F（0.9%sodium chloride）in the removal rate of Enterococcus faecalis and smear layer at different depths of the root canal wall in infected root models,the difference was significant;the depth of dentinal tubules increased continuously in six groups of different experimental methods,and the clearance rate of Enterococcus faecalis decreased gradually,and the clearance rate of bacteria in different depths of dentin tubules in group A was significantly higher than other five groups,the difference was significant;2.When different experimental methods were applied to the surface of the root canal wall L₀（0μm）and the dentinal tubule depth L₁₀₀（100²00μm）,the clearance rates of the Enterococcus faecalis in the A and B groups were all 100%and 99.97%in group Cand D,the average elimination rate of Enterococcus faecalis in the A^D group was higher than99.9%;the clearance rates of the Enterococcus faecalis in group E and F was weakened,being 70.77%and 70.73%,and the F group has the lowest clearance rate;3.When the depth was dentinal tubule L₃₀₀（300-400μm）,the clearance rate of Enterococcus faecalis in group A was 99.79%,98.32%in group B,and 96.64%in group C.The clearance rate was higher in the D^F group,which was 82.34%、80.34%and 43.16%,respectively;4.When the A and B groups acted on dentinal tubules L₅₀₀（500-600μm）,the clearance rate of Enterococcus faecalis could reach over 98%.The bactericidal effect was better than that of the bactericidal effect of different root canal irrigants used alone and different laser compatibility with NS,namely group C^F,they were 90.26%,78.06%,72.09%and 20.43%respectively,and the clearance rate of Enterococcus faecalis in group F was the lowest.Conclusion:1.Er:YAG laser,Nd:YAG laser,respectively,with 5.25%NaClO or 5.25%NaClO were used alone can effectively remove the root tube wall surface and the depth of 100²00μm、300⁴00μm、500⁶00μm,home in dentin tubule Enterococcus faecalis and its biological membrane,the clearance rate of Enterococcus faecalis at different depths of dentin tubules by Er∶YAG laser+5.25%NaClO was higher than that of other experimental groups;2.5.25%NaClO can effectively remove the Enterococcus faecalis from the surface of the root canal wall and the superficial layer of dentin.When the depth is 500⁶00μm,the clearance rate of Enterococcus faecalis was significantly decreased in the NaClO group.3.0.9%,Sodium Chloride Solution could not completely remove the bacteria and smear layer on the surface of the root canal.The Enterococcus faecalis clearance diminished as the depth of the dentinal tubules deepens.Combined use of Er:YAG laser and Nd:YAG laser can effectively increase the elimination rate of Enterococcus faecalis,but the clearance rate is weak.4.The bacterial clearance rate of Er:YAG+0.9%sodium chloride group at different depths of dentinal tubules was higher than that in Nd:YAG+0.9%sodium chloride group.