Bactericidal Effect Of PIPS-Er:YAG Laser On Enterococcus Faecalis In Curved Root Canals- An In Vitro Study

Objective: To study the effect of the Er:YAG laser on the elimination of Enterococcus faecalis in curved root canals,to evaluate whether Er:YAG laser is a simple and effective disinfection method,aiming to provide a better strategy to choose irrigating methods for curved root canals in clinical work.Methods: According to the inclusion and exclusion criteria,62 moderately curved molars(10-20 °)and 62 severe curved molars(25-40 °)were selected,and a total of 124 extracted human molars were recorded as A and B groups.All teeth were routinely pulp-open,and composite resin was used to seal non-study the root canal orifice and the apical foramina.The curved root canal were enlarged with K-file to size 20,were shaped with TFA(Dentsply)to an apical size # 25,taper 06,Then all teeth were autoclaved at 121?,1.5 MPa,for 15 min.The standard strain of Enterococcus faecalis(ATCC-29212)was inoculated into the curved root canal and cultured for 4 weeks to establish the curved root canal model of Enterococcus faecalis infection.Then eight samples were randomly selected from group A and group B,for bacteria base line on the surface of the root canal wall of group A and B.The remaining 100 samples were randomly divided into 5 groups(A1/A2/A3/A4/A5;B1/B2/B3/B4/B5;n=10)and treated as fallows:A1/B1:PIPS-Er:YAG laser+5.25%NaCIO;A2/B2:Passive Ultrasonic Irrigation+5.25%NaCIO;A3/B3: PIPS-Er:YAG laser +NS;A4/B4:Two-hole root canal washer +5.25%NaCIO;A5/B5:Two-hole root canal washer +NS.After the treatment,two samples were randomly selected from each subgroup for scanning electron microscope observation,and the remaining 8 were used to detect the number of bacteria on the surface of the root canal wall.Finally,the bacteria on the surface of root canal wall were collected and counted.The antimicrobial rate of each group was calculated by reference to the baseline samples.The data were statistically analyzed with SPSS23 software package to compare the bactericidal effect of each group.Results: The clearance rate of group A was higher than that of group B(p < 0.05);With the exception of 1 and 2(p(29)0.05),there was a significant difference between the other groups in comparison with each other,(p < 0.05).Scanning electron microscopy(SEM)revealed that the effect of root canal cleaning in group 1 and 2 was better than that in group 3;4 and 5.Conclusion: Er:YAG laser itself has no strong germicidal effect on Enterococcus faecalis,but it can significantly enhance the bactericidal effect of NaCIO on Enterococcus faecalis,and for moderate and severe curved root canals,Passive Ultrasonic Irrigation and PIPS-Er:YAG laser have the same effect on Enterococcus faecalis.