| A large number of studies have shown that bacteria is one of the important pathogenic factors of periapical periodontitis. The bacterial biofilm consists of bacterial colony on solid surface with extracellular products (such as polysaccharide and protein). Bacterial biofilm can be combined with organics and inorganics forming stable contains complex physical and chemical process and biological community interaction.From the view of bacteriology, the bacterial biofilm give to the bacterium a stable environment, play a part in defenders, make the bacterium not easy to be damaged, thus tremendously ameliorating the viability of the bacteria resistance. At present most studies of oral biofilm are root canal biofilm and plaque biofilm. And because of it is to have a rough time to sample periapical tissue, so the mechanism of it is still unclear to the formation to periapical periodontitis and the extraradicular biomembrane from the infected root canal.Plakunov found when external stimuli interference, mature and stable biofilm will liberate dissociative germ, on account of the superinfection and formation of new biofilm in various parts. In the bacterium of endodontics, the detection rate of E.f has dramaticlly dissimilitude between before and after treatment, a wide variety of researches have make clear that E.f is the predominant one in refractory periapical periodontitis and PED.In this study, the E.f infected root canal was built by the root canal-apical complex in vitro model without considering the condition of the body’s immune system. The goal for us is to investigate the influence of preparation to the formation of apical paradentitis with Enterococcus faecalis infected pulp, thus consequently to direct the treatment on clinic.Purpose:The purpose of our investigation is to investigate the periapical circumstance of the root canals that were infected from Enterococcus faecalis when in different root canal preparation factors, so as to have a preliminary discussion on the formation mechanism of periapical periodontitis.Materials and Methods1. Inject the BHI agar medium to penicillin vial, make it just reach the four millimeter to apical. Fix the stopper and vial tightly with laboratory film (Parafilm, BEMIS, USA). At the interface between root-rubber stopper coated two layers of nail polish.20 premolars were selected which were extracted because of orthodontic to produce 20 models.10 were picked up as the test groups randomly which were inoculated with E.f (ATCC 29212). At 21d after modeling, employing 16SrRNA general primer and E.f 16SrDNA pertinent primers to inspect the bacteria in root canal as well as apical tissue. If periapical bacteria detected, indicating the preparation of the patterns were not successful, then re-production model; Periapical if not detected bacteria, and the root canal only detected E.f then the modeling success. The specimens were graded alcohol dehydration, respectively tooth neck, middle third and apical third of the root tissue sections were thickness of 7 μm. Sections were stained Brown & Brenn under an optical microscope observation post from low magnification to hi^h magnification, recording observations and photography.2. Produce 320 patterns. Divide them into 2 packets which were picked up randomly. Group A is control group of 70 teeth another is test group of 250 teeth. The test packet will be inoculated with E.f. And then put them all in incubator for 21d. After 21 days, select 10 control models and 10 test models randomly. Detect them by 16SrRNA bacterial universal primer PCR. Then the test groups were classified into 4 groups of 60 teeth each. B is the group which was only open pulp without preparing; C is the group which was prepared with the 2/3 work length; D is just fit the work length; E is the work length plus lmm. Then put the 5 groups into the three gas incubator. They were detected by PCR on the day 1,7,21,35,49 and 63. During every two days, infuse fresh sterile liquid BHI culture medium with sterilized needles into dental cavity. Observe the apical with SEM.Results1. Observation of Brown and Brenn-modified Gram Staining:In the test group, there was stained dentin. It shows that E.f have invaded in different degrees in dentin tubule. Among them, the staining shows that the blue-stained of the crown third is denser than the apical third. In the control group, the root canal was clean full view, canal surface have no attachment and colored particles.2. Observation of DGGE Assay:Model, and then inoculate with E.f. After 21 days, both the control group and the test group didn’t amplify the universal 16SrDNA fragment. It means that the model established successfully.1 day after interference, Except the Group-E, all of the rest groups didn’t amplify the E.f 16SrDNA.7 days after interference, the Group-D also amplified the E.f 16SrDNA. But Group-B and C didn’t amplify it.3. Observation of Bacterial Culture by SSSPM:Make a bacterial culture to the Group D and Group E by SSSPM, the results showed that are living bacteria and no miscellaneous bacteria.4. Survey Extraradicular Biofilm by SEM:In the packet D, the cementum surface was covered with E.f biofilm on the 7d. In the group E, the cementum surface was covered with E.f biofilm on the 1d. In the control group, the cementum surface was covered without areas of bacteria.Conclusions1. In this model, the histology Brown & brenn stain confirmed that E.f could infect the root canal, form biofilm individually and invade deeply into the dentinal tubules.2. For the infected root canal in E.f, when the apical third of root canals were disturbed, bacteria will leakage out the root apical. These results provide a new treatment for the clinic. |
PDF Full Text Request