Inhibition Of Enterococcus Faecalis By ZnO Quantum Dots Root Canal Sealer And Evaluation Of Its Physical And Chemical Properties

Nanometer zinc oxide quantum dots(ZnO QDs)have been widely used in various fields in recent years due to their excellent disinfection performance and low cytotoxicity.At present,the fillers commonly used in root canal therapy,trioxy mineral polymer(MTA),have good sealing performance but poor bacteriostasis.To reduce the risk of infection during root canal therapy,the use of MTA mixed with materials with good antibacterial properties is currently a common way to improve MTA.Enterococcus faecalis is the most common infectious pathogenic bacteria in root canal therapy.It has the ability to produce biofilm and is resistant to most antibiotics.It is easy to cause oral infection and difficult to remove.In order to explore the antibacterial and anti-biofilm effects of ZnO QDs on Enterococcus faecalis,explore the physicochemical properties and antibacterial effects of the new mixed apical sealer with ZnO QDs,and evaluate the clinical application effects of MTA and ZnO QDs mixed sealer,the following three tests were carried out:Test 1 Inhibitory effect of ZnO QDs on Enterococcus faecalis in vitroIn order to explore the effect of ZnO QDs on the growth of Enterococcus faecalis,the growth curve of Enterococcus faecalis was measured in this experiment.The effect of ZnO QDs on the formation of Enterococcus faecalis biofilm was investigated by crystal violet staining,Gram staining,MTT and scanning electron microscopy.The results of in vitro bacteriostatic tests on Enterococcus faecalis showed that ZnO QDs inhibited the growth of Enterococcus faecalis in a concentrate-dependent manner.When the concentration of ZnO QDs was greater than 0.25 mg/m L,it could significantly inhibit the formation of biofilm.The results of electron microscopy showed that the number of bacteria on the tooth surface coated with ZnO QDs in the dentin test group and the enamel test group was56.5-88.8% less than that in the positive control group,and the degree of bacterial aggregation was more dispersed.Test 2 Effect of ZnO QDs on expression levels of E.faecalis biofilm formation related genesBased on the results of in vitro bacteriostatic tests,ZnO QDs of 2.0 mg/m L(high concentration)and 0.25 mg/m L(low concentration)were applied to Enterococcus faecalis biofilm,and real-time fluorescence quantitative polymerase chain reaction(q PCR)was used to measure the genes related to the formation of Enterococcus faecalis biofilm(ebp A/B/C,epa A/B/E/G/Q/R)to further explore the effect of ZnO QDs on genes related to Enterococcus faecalis biofilm formation.Fluorescence quantitative results showed that ZnO QDs significantly inhibited the expression of ebp A/C and epa A/B/E/G/R,and the inhibition effect of high concentration ZnO QDs was better than that of low concentration.Test 3 Physicochemical properties and operational evaluation of novel apical sealerZnO QDs with different concentrations were mixed with MTA,and the changes of curing time,fluidity,dissolution rate and X-ray resistance were measured to evaluate the physical properties of the mixed sealer.Through different operators using beagle dogs to carry out root tip filling operation and score the use effect of mixed preparation,the actual operation effect of mixed preparation was evaluated.The experimental results of physical properties evaluation show that ZnO QDs has no significant effect on the curing time of MTA,adding ZnO QDs can reduce the dissolution rate and fluidity of MTA material,and increase the X-ray radiation resistance and bacteriostatic rate of MTA material.When the concentration of ZnO QDs is 1.0 mg/m L,the mixed material has the best bacteriostatic effect on Enterococcus faecalis.The results of apical filling were good and did not have significant difference among different experimental personnel.Conclusion:(1)ZnO QDs at a concentration above 0.25 mg/m L can inhibit the expression of genes related to the formation of Enterococcus faecalis biofilm,and has antibacterial and antibiofilm effects.(2)The addition of ZnO QDs at a concentration of less than 2.0 mg/m L has no significant effect on the curing time of MTA,while reducing the fluidity and dissolution rate of the mixed materials,and increasing the X-ray radiation resistance and bacteriostatic performance of the mixed materials,which is a potential improved pet root canal sealer scheme.