Antibacterial Efficacy Of PDT On Enterococcus Facalis Within Infected Simulated Lateral Canals

Objectives:The purpose of this study was to assess the antibacterial effect of photodynamic therapy on Enterococcus faecalis within infected simulated lateral canals by means of establishing an in vivo root cannal model infected by E.f. On that basis,it was designed to study antibacterial effects of photodynamic therapy with different energy density and choose the best energy parameter, prospecting to provid the theoretical and experimental basis on HMME-PDT’s clinical practice for root canal disinfection.Methods:1.Enterococcus faecalis(ATCC29212) was recovered at room temperature and then anaerobic cultured in the electro-heating standing-temperature cultivator at37℃for24h. It was inoculated into TPY liquid enrichment medium and enriched for48h,prepared for a concentration of1.5x109CFU/ml and set aside.2.Experimental teeth were prepared chemomechanically,standardized simulated lateral canals were created at3mm from the apical foramen(AF) with K-file sizel5. After preparation,the specimens were infected with Enterococcus faecalis for21d.3.The study for observing the antibacterial effect of photodynamic therapy:the specimens were grouped into three groups,each group contain20teeth:one group was irrigated with physiological saline.The other group was irrigated with5.25%NaClO.For PDT,they were incubated with HMME at concentration of40μg/ml for5min, followed by exposure to light at532nm for120s with the energy power for60mW.Microbial samples(the dentin chips from simulated lateral canals) were taken before and after the treatments. The survival fractions in each simulated lateral canal was calculated by counting CFUs.4.The study for choosing the best energy power parameter:the specimens were randomly divided into eight groups.Group A was irrigated with physiological saline.Group B was irrigated with5.25%NaClO.For other groups, they were incubated with HMME at concentration of40μg/ml for5min, followed by exposure to light at532nm for120s with different powers in a spiral pattern.The survival fractions in each simulated lateral canal was calculated by CFUs.Assess the antibacterial effects of photodynamic therapy on Enterococcus faecalis within infected simulated lateral canals in vivo with different energy.density and choose the best energy parameter for the experimental studyResults:1.The results of the study for observing the antibacterial effect of photodynamic therapy:The HMME-PDT-treated group and NaClO-treated group both resulted in a significant reduction in the number of E.faecalis in simulated lateral canals compared with the negative controls(P<0.05);The HMME-PDT-treated teeth (89.59%)yielded significantly different results relative to the positive control(76.93%)(P<0.05)2.The results of the study for choosing the best energy power parameter:The HMME-PDT-treated groups resulted in a significant reduction in the number of E.faecalis in simulated lateral canals compared with the negative controls(P<0.05);They had a better bactericidal effect than NaClO-irrigated group except group C;The difference of antibacterial effects between the F、G、H groups was insignificant(P>0.05).We can choose80mW as the best energy parameter for the experimental study.Conclusion:1.HMME-PDT with40μg/ml HMME incubated for5min, followed by exposure to light at532nm for120s with a power of60mW had significant inhibitive efficacy on Enterococcus faecalis within infected simulated lateral canals.The sterilizing rate can reach89.59%.It will provide a new effective method for the root canal disinfection.2.HMME-PDT had significant inhibitive efficacy on Enterococcus faecalis within infected simulated lateral canals and the efficacy was power-depended.It can pay the role of the best with the power of80mW.