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Periodontitis is an inflammatory disease of the oral cavity initiated by a microbial biofilm (or 'dental plaque'). Subgingival biofilms in periodontal pockets are not easily analyzed without the loss of structural integrity. These subgingival plaques are structured communities of microorganisms with great phylogenetic diversity embedded in a self-produced extracellular polymeric matrix. For almost three decades, knowledge of the structure of plaque located below the gingival margin has been limited to landmark studies from the 1970s that were unaware of the breadth of microbial diversity we appreciate now. Only recently has technical progress - combining histology, confocal scanning fluorescent microscopy and fluorescent in situ hybridization to localize the most abundant species from different phyla and species associated with periodontitis - provided new insights into the architecture of subgingival biofilms. This review focuses on the structure and composition of subgingival biofilms and discusses current knowledge on the nature of the extracellular matrix. We describe further structural aspects of 'subgingival' biofilms produced in vitro that are gaining considerable interest as we search for models to investigate biofilm development, resistance to antibiotics, extracellular polymeric matrix composition and function, and reciprocal host-cell-to-biofilm interactions., (Copyright © 2012 S. Karger AG, Basel.)

The intraperitoneal immunization of Balb/c mice with subgingival plaque from advanced periodontal pockets or with certain strains of Actinobacillus actinomycetemcomitans, Fusobacterium nucleatum, Actinomyces israelii, Streptococcus mitis, or Streptococcus oralis yielded frequently indistinguishable IgM monoclonal antibodies which were reactive with antigens from a variety of oral bacteria. This study aimed to characterize the specificity of such monoclonal antibodies and the diversity of oral bacteria expressing this target antigen or epitope. Using a competitive enzyme-linked immunosorbent assay to study a variety of competitor substances for their capacity to bind to the monoclonal antibodies, we identified phosphorylcholine as the recognized epitope. The concentration of positive bacteria with extraordinarily bright cell wall fluorescence in indirect immunofluorescence assays varied between 0.1% and 15% in subgingival and from 10 to 40% in supragingival plaque samples. Labeled bacteria belonged to different morphotypes, including cocci, rods, and filaments. Of 75 species tested in vitro, 14 gram-positive and four gram-negative species were found to harbor positive strains. Haemophilus aphrophilus, Streptococcus mitis, Actinomyces georgiae, Actinomyces gerencseriae, Actinomyces israelii, and Actinomyces odontolyticus were human oral species of which all tested strains were capable of binding the cross-reactive monoclonal antibodies. In contrast, Actinomyces naeslundii was consistently negative. These data provide evidence for a much more common expression of phosphorylcholine by oral bacteria than hitherto believed but do not indicate an obvious association of phosphorylcholine expression with oral health or inflammatory periodontal diseases.

The aim of this study was to examine the distribution of typical periodontitis-associated microorganisms in refugees arriving from non-industrialized countries, and to relate the presence of these organisms to the periodontal condition of the subjects. Thirty males between 35-44 years of age were surveyed. Dental plaque, calculus, gingivitis, loss of attachment, and probing depths were recorded for all surfaces. A total of 90 microbiological samples were taken with paper points from mesial sites of teeth 16, 36 and 41. Microbiological test sites were grouped by probing depths and loss of attachment. Only 16.8% of all surfaces had probing depths > 3 mm, although 90.7% of surfaces had loss of attachment > 1 mm. Twenty-one sites with obvious periodontal destruction (PD > 3 mm, LA > 2 mm) showed the greatest recovery of Porphyromonas gingivalis (66.7%). However, 51 sites with minimal periodontal disease (PD < or = 3 mm, LA < 2 mm) and with no gingival recession also showed a relatively high detection frequency of P. gingivalis (34.1%). Twenty-four of these samples came from 12 patients with no pockets > 5 mm and with less than 10% of all sites yielding pockets > 3 mm. The detection frequencies of Prevotella intermedia (91.6%), Bacteroides forsythus (25.0%), Wolinella spp. (33.3%) and Actinobacillus actinomycetemcomitans (50.0%) were similar in these sites compared with periodontitis sites. Morphologically distinct isolates, from 19 individuals positive for A. actinomycetemcomitans, were serotyped by indirect immunofluorescence.(ABSTRACT TRUNCATED AT 250 WORDS)

Fifty-one fluorescence-positive black-pigmented Bacteroides strains obtained from 51 patients with deep periodontal pockets (greater than 6 mm) were identified and characterized. Fifty of these strains were presumptively identified as Bacteroides intermedius according to the indole reaction. This was confirmed by further biochemical characterization. The 50 strains from diseased sites were then compared with 16 B. intermedius strains isolated from periodontally healthy individuals with no signs of destructive periodontal disease. Tests for antimicrobial susceptibility showed similar patterns for all 50 pocket-derived strains, except for one beta-lactamase-positive strain that was resistant to penicillin G and ampicillin. Forty-seven strains were tested for binding of three monoclonal antibodies defining three distinct serogroups of B. intermedius. Thirty-one strains belonged to serogroup I, three to serogroup II and thirteen to serogroup III. In comparison to the strains from the shallow periodontal pockets, serogroup I was significantly overrepresented in the patient group with periodontal disease. We conclude that saccharolytic black-pigmented Bacteroides species from deep periodontal pockets constituted, with very rare exceptions, a biochemically homogeneous but antigenically heterogeneous group of B. intermedius and that serogroup I is predominantly found in deep periodontal lesions.

The prevalence of Bacteroides forsythus and Bacteroides gingivalis in subgingival plaque of patients on short recall was analyzed in relation to the probing depth of the test sites. The subjects had excellent oral hygiene and therefore were unlikely to suffer from active periodontal destruction. Sixty-four subgingival plaque samples, taken from gingival or periodontal pockets with probing depths ranging from 1 to 8 mm, were quantitatively assessed for the presence of the two species using species-specific monoclonal antibodies in conjunction with a very sensitive indirect immunofluorescence technique. Both organisms were encountered in probes from sites as shallow as 2 mm, but the percentage of positive samples clearly rose in relation to the probing depth of the test sites. Overall, B. forsythus was found to colonize lesions earlier, that is at smaller probing depths, than B. gingivalis. Interestingly, whenever a sample was found to be positive for B. gingivalis it was also positive for B. forsythus. The numbers of B. forsythus and B. gingivalis and the total bacterial cell number found in the pockets were significantly correlated to the probing depth. However, with advancing probing depth the increase of the total cell numbers of the two Bacteroides species was considerably more pronounced than the increase of the total subgingival plaque cell number. The recall interval neither affected the frequency of sites positive for B. forsythus or B. gingivalis nor influenced significantly the proportions of the two species in subgingival plaque.(ABSTRACT TRUNCATED AT 250 WORDS)