The hypothesis that Enterococcus faecalis resists common intracanal medications by forming biofilms was tested. E. faecalis colonization of 46 extracted, medicated roots was observed with scanning electron microscopy (SEM) and scanning confocal laser microscopy. SEM detected colonization of root canals medicated with calcium hydroxide points and the positive control within 2 days. SEM detected biofilms in canals medicated with calcium hydroxide paste in an average of 77 days. Scanning confocal laser microscopy analysis of two calcium hydroxide paste medicated roots showed viable colonies forming in a root canal infected for 86 days, whereas in a canal infected for 160 days, a mushroom-shape typical of a biofilm was observed.Analysis by sodium dodecyl sulfate polyacrylamide gel electrophoresis showed no differences between the protein profiles of bacteria in freefloating (planktonic) and inoculum cultures. Analysis of biofilm bacteria was inconclusive.These observations support potential E. faecalis biofilm formation in vivo in medicated root canals.The most common reasons for failures in conservative root canal therapy are related to problems in instrumentation. However, occasionally, bacteria resistant to conservative therapy may also be involved (1). "Bacteria-associated endodontic failures together with pulp-periapical infections refractory to conventional treatment represent the unresolved bacteriological problems in endodontics" (2). Numerous studies have shown that persistent endodontic infections are often caused by Enterococcus faecalis (1, 3).Virulence factors of E. faecalis, such as hemolysin, gelatinase, and enterococcal aggregation substance (EAS) play an important role in the bacterium's pathogenesis (4). However, the mechanism through which E. faecalis persists in the root canal is not well understood. E. faecalis seems to be highly resistant to the medications used during treatment and is one of the few organisms that has been shown to resist the antibacterial effect of calcium hydroxide (5, 6). There is little research to explain why E. faecalis is resistant to root canal therapy. It is easily destroyed when grown in vitro, but it becomes resistant when present in the environment of the root canal system (7). Therefore, E. faecalis must undergo some type of change while in the root canal system, possibly activating some virulence factor that makes it more resistant. Alternatively, it may form a biofilm.Biofilms, also known as plaque, are complex communities of bacteria embedded in a polysaccharide matrix (8). Suspended, i.e. planktonic, bacteria that are either leaving or joining the biofilm surround the biofilm. The growth conditions vary between biofilm and planktonic environments. For this reason, proteins expressed by biofilm bacteria may differ from those expressed by their planktonic counter parts, and both the biofilm bacteria and the planktonic bacteria may differ from bacteria maintained in the laboratory.The purpose of this study was to test the hypothesis that E. faecalis forms a biofi...

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Enterococcus faecalis is a pathogen that persists in medicated root canals. Here, we tested the hypothesis that the E. faecalis proteases, serine protease and gelatinase, and the collagen-binding protein (Ace) contribute to adhesion to the root canal. Scanning electron microscopy was used to examine dentin binding by four E. faecalis strains: OG1RF, the wild type, and three mutant derivatives of OG1RF, TX5128, TX5243 and TX5256 deficient in serine protease and gelatinase, serine protease, and Ace, respectively. For each strain, 20 root halves were exposed to 3 x 10(9) to 5 x 10(9) cells/ml for 6 h, and 50 fields per root half were examined for adherent bacteria. Statistical analysis revealed that adherence of OG1RF was significantly greater than the mutant strains (P < 0.001), while significant differences were not detected between the protease mutants. The data indicate that serine protease and Ace aid E. faecalis binding to dentin, while the role of gelatinase is uncertain.

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Introduction The purpose of this study was to compare digital periapical and cone beam computed tomography (CBCT) images to determine the number of canals in the mesiobuccal root (MB) of maxillary molars and to compare these counts to micro CT (μCT), which was also used to determine canal configuration. Methods Digital periapical (RVG 6100), CBCT (9000 3D) and μCT images (the reference standard) were obtained of 18 hemi-maxillas. With periapical and CBCT images, 2 endodontists independently counted the number of canals in each molar and repeated counts 2 weeks later. Teeth were extracted, scanned with μCT, and 2 additional endodontists, by consensus, determined the number and configuration of canals. The Friedman test was used to test for differences. Results In mesiobuccal roots, 2 canals were present in 100% (13/13) of maxillary first and 57% (8/14) second molars, and 69% (9/13) and 100% (8/8) of these exited as two or more foramina. There was no difference in canal counts for original and repeat reads by the two observers with periapicals (P = 0.06) and with CBCT (P = 0.88) and no difference when CBCT counts were compared with μCT counts (P = 0.52); however, when periapical counts were compared with μCT counts there was a significant difference (P = 0.04). Conclusions For cadaver maxillary molars, μCT canal counts were significantly different from digital periapical radiograph counts but not different from Carestream 9000 3D CBCT counts.