| The purpose of root canal therapy(RCT) was to eliminate microorganism and necrotic tissue from infected root canals and to promote tissue repair and regeneration. However, RCT could reduce but does not necessarily eliminate all microbes, and viable bacteria often remain in the dentinal tubules and lateral canals to which often result in the failure of treatment. Therefore, the use of sealer with antibacterial activity is considered bene?cial in the effort to not only seal the coronal and apex of the root canal but also to further reduce the number of remaining microorganisms or even eradicate the infection completely.So it is important to select sealers having potent antibacterial activity in clinical treatment. With the development of dental materials, many new sealers were widespread application in root canal filling, such as Gutta Flow, i Root SP, etc., which possess good biocompatibility, sealing ability and easy maneuverability. But how their antibacterial properties are? Compared with traditional sealers, what are the advantages of theirantibacterial properties? These questions are worthy for our discussion. Currently, there are many methods to evaluate the antibacterial effect of sealer, such as ADT, DCT, infected root canal models, etc., which have advantages and disadvantages. Whether the conclusion of different methods is the same about the antibacterial effect? This is also worthy for comparative study.Therefore, this study chooses two methods of DCT and infected root canals model in vitro to evaluate the antibacterial effect of sealers ZOE, AH-Plus, Gutta Flow, i Root SP and Vitapex towards clinic-derived Enterococcus faecalis, and to measure the flow ability and p H value, which is aimed at not only providing the basis for clinical treatment, but also the more proper design of experimental methods. The study was divided into the following four parts:Experiment One: Isolation and identification of Enterococcus faecalis from clinical cases.Select 20 cases of patients in our department who need root canal re-treatment. Firstly, use Streptococcus Faecalis Medium(SF Medium) and bile esculin medium to culture clinically isolated strains preliminarily by observing the color change. Secondly, the positive specimens use BBL CRYSTAL identification system of bacteria biochemical reactions. Finally utilize PCR amplification and DNA purification recycling technologies to identify 16 Sr RNA sequences of the bacteria and to compare the standard gene libraries.The results showed that in 20 clinical collected cases, there were six cases successfully isolated E.f and the detection rate was 30%. This experiment showed 16 Sr RNA and PCR amplification techniques were important methods for the clinical detection and identification of E.f, which is significantly greater than the accuracy of the traditional microbial culture.Experiment Two: Evaluate antibacterial ability of different root canal sealers by DCTThe ZOE, AH-Plus, Gutta Flow, i Root SP and Vitapex five sealers were evenly mixed into the bottom of the tube, and the positive control group was the Vaseline. Bacteria insuspension were exposed to the materials for 60 minutes by using sealers that were freshly(20min) mixed or set for 1, 3, 7and 14 days. The suspensions were diluted in 10-fold step and 50μl of each dilution was spread onto agar for bacteria cultivation under the same condition. The numbers of bacteria were counted and analyzed by one-way ANOVA.The results showed that: bacteria could be eradicated completely by biological ceramic sealer i Root SP and AH-Plus sealers in freshly mixed group(20min). The antibacterial ability of i Root SP could maintain 7d(P<0.05), and ZOE, AH-Plus and Vitapex sealers in freshly mixed group(20min) had strong antibacterial properties(P <0.05), but the antibacterial effect was disappeared after 3 days(P>0.05), while Gutta Flow sealer had no antibacterial effect against clinical isolation of E.f(P> 0.05).Experiment Three: Evaluate antibacterial ability of different root canal sealers by root canal model infected with E.f.Single rooted human teeth infected with E.f for 3 weeks were randomly divided into 5 groups(ZOE, AH-Plus, Gutta Flow, i Root SP and Vitapex), and a positive and a negative control groups. The corresponding samples were taken after1 d, 3d, 7d, and 14 d respectively, which were drilled by using a round bur. Then, the collected filling material and dentin was diluted stepwise for culture and the numbers of bacteria were counted and analyzed by one-way ANOVA.The results showed that: Gutta Flow sealer still had no antibacterial effect against E.f(P>0.05), while the rest of sealers with antibacterial ability coud be maintained until the 14d(P<0.05), which was longer than the results of DCT in Experiment Two. The antibacterial effect of ZOE, AH-Plus and Vitapex three sealers were unchanged after 3d(P> 0.05), while i Root SP sealer possessed the strongest antimicrobial effect at the 14 d than other time points(P<0.05), which indicated that its antibacterial properties had not diminished as the extension of time. Accordingly to the preliminary results, we can conclude that the method evaluating the antibacterial effect of sealer should be based on the various compositions and physical and chemical properties of sealers.Experiment Four: Measure the flow ability and p H value of different root canalsealers.The mixed five sealers were placed on the center of a glass plate. Three minutes later, a second glass plate weighing 20 g and a 100 g weight were placed centrally on top of the sealer. After 10 minutes from the start of mixing, the load was removed, and the diameters of the sample disks were measured.An equal amount of each sealer was applied to cover the bottom surface of the wells of 24-well plates and kept in 100% humidity at 37℃. Twenty minutes and 1, 3, 7, 14 days after mixing, 3m L of sterile water was added to each well. The p H values were measured by using a p H meter.The results showed that: flow ability from strong to weak order for i Root SP> Gutta Flow>ZOE>AH-Plus>Vitapex; p H value at 14 d in descending order for i Root SP> VItapex>AH-Plus>Gutta Flow>ZOE. The results showed that the antimicrobial activity and p H value had a certain correlation, while the antimicrobial activity and flow ability had no obvious relationship.To sum up, the long-term antibacterial activity of root canal sealer is closely related with the antibacterial ingredients. At the same time, other physical and chemical properties of the sealer can also affect the antibacterial effect. |
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