The Disinfection Effectiveness Of Photodynamic Therapy Combined With EDTA On Infected Root Cancals In Vitro

Objectives:Root canal disinfection is a critical step in root canal therapy, the root canal disinfection has not yet reached the extent of the ideal, so it is necessary to find a more effective and thorough root canal disinfection method. Photodynamic therapy (PDT) is a new therapy to produce strong oxidizing singlet oxygen to kill pathogenic microorganism, in which light, oxygen and photo-sensitizer participate. It has strong antibacterial effect, wide antimicrobial spectrum, quick, safety and won’t produce resistance, etc. EDTA (ethylene diamine tetraacetic acid disodium) has strong permeability and can go to defile grubbing tube layer as root canal irrigant.This study was to investigate the disinfection effectiveness of PDT combined with EDTA on Enterococcus faecalis biofilms within infected root canals in vitro, prospecting to provide an alternative method to have a thorough root canal disinfection in clinical.Methods:1. Revive E. faecalis (ATCC29212) and naerobic culture48h, adjust the concentration of bacterial suspension into1×109CFU/mL.2. After the bacterial suspension was dealt with17%EDTA, combine different irradiation time of532nm semiconductor and various concentrations of HMME to deal with the bacterial suspension to select the best effect of PDT parameters.3. Collect premolars pulling for orthodontic and use crown down to prepare root canals, then put E. faecalis into root canals for21days to establish infected root canal model.4.The infected premolar teeth were divided into5groups. Group A to C included teeth treated by PDT only,17%EDTA only, and PDT combined with EDTA (The parameters of PDT are same as Group A).Group D served as the positive control group with teeth treated with5.25%NaClO. Group E served as the negative control group treated with0.9%normal saline (NS). The disinfection of the E.faecalis biofilm was evaluated by colony-forming unit(CFU) counting.5. After experimental treatment, each root canal was refilled with BHI for7days to observe the growth of bacteria. 6. The morphology of root canals after experiment were examined by SEM, which further verify the disinfection effectiveness of PDT combined with EDTA.Results:1. The best effect of photodynamic therapy parameter on E. faecalis after treated with17%EDTA are selected:the concentrations of HMME is40μg/ml, and the time of532nm semiconductor is90s in continuous irradiation with power density0.14W/cm2.2. The results of killing effect of PDT combined with EDTA on E. faecalis shows that:The sterilizing rate of PDT combined with EDTA group reach up to100%, which is highly overtop other four groups (P<0.05).3. The reply experiment shows that the number of infected root canals in PDT combined with EDTA group was only4, the percentage of infected root canals respectively is26.67%, which was significantly less than the other4groups(P <0.05).4. The SEM showed that in PDT combined with EDTA group:there was no smear layer or bacteria in inner wall of root canals, all the dentinal tubules were patent; dentin tubules are unobstructed, no defile bolt blocked.Conclusion:1. PDT combined with EDTA can be effective in root cancal disinfection, the best effect of photodynamic therapy parameter on E. faecalis after treated with17%EDTA are selected:the concentrations of HMME is40μg/ml, and the time of532nm semiconductor is90s in continuous irradiation with power density0.14W/cm2.2. PDT combined with EDTA can be effective in root canal disinfection and which has a good long-term results, not only in killing E. faecalis, but also in wiping off smear layer, which can provide an alternative method to have a thorough root canal disinfection in clinical.