| Background:Factors that may contribute to a persistent periradicular infection after root canal treatment include intraradicular infection, extraradicular infection, foreign body reaction, and cysts containing cholesterol crystals. It is generally believed that the major cause of failure is the survival of microorganisms in the apical portion of the root-filled tooth. Unlike primary endodontic infections, which are polymicrobial in nature and dominated by gram-negative anaerobic rods, the microorganisms involved in secondary infections are composed of one or a few bacterial species. Enterococcus faecalis is a microorganism commonly detected in asymptomatic, persistent endodontic infections, even though it belongs to the normal flora of human. It is commonly found in a high percentage of root canal failures and it is able to survive in the root canal as a single organism or as a major component of the flora. This finding can be explained by various survival and virulence factors possessed by Enterococcus faecalis. Enterococcus faecalis is a persistent organism that, despite making up a small proportion of flora in untreated canals, plays a major role in the etiology of persistent periradicular lesions after root canal treatment. Elimination of E. faecalis from the root canal with mechanical preparation, irrigating solutions and root-canal-filling materials remains a challenge. The intent of this article is to studies that 3 endodontic irrigations and root canal sealers that are effective in eliminating E. faecalis from the root canal system in vitro.Objective:(1)To set up the model of Enterococcus faecalis within root canals in vitro.(2)To evaluate the antibacterial activity of 3 endodontic irrigations (5.25% Sodium hypochlorite, 2% Chlorhexidine and 17% EDTA) on Enterococcus faecalis (E. faecalis) within root canals in vitro.(3)To evaluate the antibacterial activity of 3 root canal sealers (Acroseal, AH plus and Cortisomol) on Enterococcus faecalis (E. faecalis) within root canals in vitro.(4)To evaluate the antibacterial activity of 3 root canal sealers (Acroseal, AH plus, Cortisomol) on Enterococcus faecalis (E. faecalis) within root canals in vitro with time changes.(5)To evaluate the antibacterial activity of 3 endodontic irrigations (5.25% Sodium hypochlorite, 2% Chlorhexidine, 17% EDTA) and 3 root canal sealers Acroseal, AH plus, Cortisomol) on Enterococcus faecalis (E. faecalis) within root canals in vitro. And variance of CFU of the groups with time changes.Methods:1. The root canals of 100 extracted teeth were rule sterilizing, removal dental pulp and instrumented to apical size 40 by K steel file. The selected root canals were irrigating by 17%EDTA and 0.5% sodium hypochlorite and distilled water. The apicals were sealed with resin obturator. The specimens were sterilized in the autoclave for 20 min at 121℃. 2 root canals of the teeth were cultivated for detecting the effect of sterilization. The each root canal was inoculated with 100μl of bacteria fluid that was density of 1.0×108CFU/ml in 30min. The samples were cultivated on BHIA with CO2 for 21d at 37℃. Every other day, BHIA was renewed till the day 21. Till the day 21, we randomly extracted 2 samples and carried out the biochemistry characterization assay by API 20 strep kit.2. The 96 roots with E. faecalis were randomly divided into 4 groups, which underwent different endodontic irrigation: Group 1: 5.25% sodium hypochlorite, Group 2: 2% chlorhexidine, Group 3: 17% EDTA, Group 4: 0.9%Nacl as negative control. Every group has 24 teeth. Microbiological samples were collected from root canals before irrigate and after irrigate. Then count the colony forming units (CFU). Compute and use one-way ANOVA to contrast variance of colony forming units (CFU) among the groups.3. From the 4 irrigation groups, we randomly extracted 6 teeth to constitute the new filling groups, 24 teeth constituted one group. The 4 groups which were filled different root canal sealers: Group 1: Acroseal (calcium hydroxide as the root canal sealant), Group 2: AH Plus, Group 3: Cortisomol, Group 4: calcium carbonate as negative control. Apical foramens were filled by composite resin obturator. Samples were released into BHI influid medium and cultivate in CO2 thermostat at 37℃. 1 week later, root canal for every sample was drilled for 1 mm diameter hole into root canal and fragments for dentin were put into the sterile water of Eppendorf tubes filled. Then the groups were continued to be cultivated. 3 and 5 weeks later, samples were extracted just like 1 week later. The Eppendorf tubes and agitated for 1min. Then count the colony forming units (CFU). In Compute and use Repeated Measures ANOVA to contrast variance of colony forming units (CFU) among the groups.Results:1. By means of sorts of bacteriology characterization approaches, the infection of root canal by Enterococcus faecalis could be sure and results showed that there were no living contaminants. The infection model could be successfully established.2. The numbers of Enterococcus faecalis in root canal with 3 groups of endodontic irrigation(5.25% sodium hypochlorite, 2% chlorhexidine and 17% EDTA) were effectively reduced (F=103.060, P=0.000). 5.25% sodium hypochlorite, 2% chlorhexidine and 17% EDTA were not statistically significant (P>0.05). But, 5.25% sodium hypochlorite, 2% chlorhexidine and 17% EDTA were statistically more effective than 0.9% Nac1 (P<0.001).3. In Test of Between-Subjects Effects, main effect of factor of endodontic irrigations (F=360.922, P=0.000), main effect of factor of root canal sealers (F=96A24, P=0.000), main effect of factor of endodontic irrigations and root canal sealers (F=4.580, P=0.000) have statistical significance. In Tests of Within-Subjects Effects, main effect of factor of measure time (F=286.016, P=0.000), crossover effect of factor of endodontic irrigations and measure time (F=6.044, P=0.000), crossover effect of factor of root canal sealers (F=21.290, P=0.000), crossover effect of factor of endodontic irrigations and root canal sealers (F=2.338, P=0.009) have statistical significance.Conclusion:1. The model for root canal in vitro invaded by Enterococcus faecalis can be established successfully.2. 5.25% sodium hypochlorite, 2% chlorhexidine and 17% EDTA were effective for root canal irrigation. However, 3 endodontic irrigations can not completely clean up E. faecalis within root canal system.3. AH plus and Cortisomol are effective in eliminating E. faecalis from the root canal system in vitro. The antibacterial activity for AH plus is slightly powerful than Cortisomol, while the antibacterial effect of Acroseal is comparatively weak. However, 3 root canal sealers could not kill Enterococcus faecalis completely.4. 3 endodontic irrigations (5.25% sodium hypochlorite, 2% chlorhexidine and 17% EDTA), and 3 root canal sealers (Acroseal, AH plus and Cortisomol) were applied jointly, among them, the combination for 5.25% sodium hypochlorite and AH plus had the best antibacterial effect.5. Enterococcus faecalis grew as time went by in filled root canal. In the group of Acroseal, the numbers of Enterococcus faecalis increased after 3 weeks, while Enterococcus faecalis increased after 5 weeks in the other two groups, and the extent is smaller than the group of Acroseal. |
