It has been recognized for some time that bacterial species exist in complexes in subgingival plaque. The purpose of the present investigation was to attempt to define such communities using data from large numbers of plaque samples and different clustering and ordination techniques. Subgingival plaque samples were taken from the mesial aspect of each tooth in 185 subjects (mean age 51 +/- 16 years) with (n = 160) or without (n = 25) periodontitis. The presence and levels of 40 subgingival taxa were determined in 13,261 plaque samples using whole genomic DNA probes and checkerboard DNA-DNA hybridization. Clinical assessments were made at 6 sites per tooth at each visit. Similarities between pairs of species were computed using phi coefficients and species clustered using an averaged unweighted linkage sort. Community ordination was performed using principal components analysis and correspondence analysis. 5 major complexes were consistently observed using any of the analytical methods. One complex consisted of the tightly related group: Bacteroides forsythus, Porphyromonas gingivalis and Treponema denticola. The 2nd complex consisted of a tightly related core group including members of the Fusobacterium nucleatum/periodonticum subspecies, Prevotella intermedia, Prevotella nigrescens and Peptostreptococcus micros. Species associated with this group included: Eubacterium nodatum, Campylobacter rectus, Campylobacter showae, Streptococcus constellatus and Campylobacter gracilis. The 3rd complex consisted of Streptococcus sanguis, S. oralis, S. mitis, S. gordonii and S. intermedius. The 4th complex was comprised of 3 Capnocytophaga species, Campylobacter concisus, Eikenella corrodens and Actinobacillus actinomycetemcomitans serotype a. The 5th complex consisted of Veillonella parvula and Actinomyces odontolyticus. A. actinomycetemcomitans serotype b, Selenomonas noxia and Actinomyces naeslundii genospecies 2 (A. viscosus) were outliers with little relation to each other and the 5 major complexes. The 1st complex related strikingly to clinical measures of periodontal disease particularly pocket depth and bleeding on probing.

Microbial complexes in subgingival plaque

Microbial etiological agents of destructive periodontal diseases

There have been many advances in the past decade in our knowledge of the microflora associated with periodontal diseases, the potential of specific periodontal bacterial species to destroy periodontal tissues, and the host responses to bacterial infections of the periodontium. It is the purpose of this and an accompanying paper, to present important features of the host-parasite interaction in human periodontal disease. The present communication emphasizes characteristics of periodontopathic bacteria which may enable them initially to colonize the host, to survive in the periodontal pocket, and possibly to invade the gingival tissue despite potentially effective host defense systems, and to destroy the collagenous periodontal ligament, the alveolar bone, and other tissue components surrounding the tooth. It seems reasonable to assume that a bacterial species must possess factors applicable to most if not all of the above aspects of the infectious process of periodontal disease in order to produce periodontitis.

Black-pigmented Bacteroides species, Capnocytophaga species, and Actinobacillus actinomycetemcomitans in human periodontal disease: virulence factors in colonization, survival, and tissue destruction.

A 16S rRNA-based polymerase chain reaction (PCR) detection method was used to determine the prevalence of Actinobacillus actinomycetemcomitans, Bacteroides forsythus, Campylobacter rectus, Eikenella corrodens, Porphyromonas gingivalis, Prevotella intermedia. Prevotella nigrescens and Treponema denticola in subgingival specimens of 50 advanced periodontitis, 50 adult gingivitis and 50 pediatric gingivitis subjects. The optimal PCR conditions were determined for each study species. Agarose gel electrophoresis of PCR products from each study species revealed a single band of the predicted size. Restriction enzyme digestion of amplicons confirmed the specificity of the amplification. PCR detection limits were in the range of 25-100 cells. No cross-reactivity with other oral micro-organisms or nonspecific amplification was observed. The prevalence by PCR in advanced periodontitis, adult gingivitis and pediatric gingivitis subjects was 30%, 14% and 14% for A. actinomycetemcomitans, 86%, 18% and 8% for B. forsythus, 74%, 52% and 78% for C. rectus, 80%, 70% and 66% for E. corrodens, 70%, 10% and 14% for P. gingivalis, 58%, 12% and 18% for P. intermedia, 52%, 20% and 22% for P. nigrescens, and 54%, 16% and 16% for T. denticola, respectively. The prevalence was higher in the advanced periodontitis group than in both adult gingivitis and pediatric gingivitis for A. actinomycetemcomitans, B. forsythus, P. gingivalis, P. intermedia, P. nigrescens and T. denticola at P < 0.01, and for E. corrodens at P < 0.05. The prevalence of C. rectus was significantly higher in the advanced periodontitis group than in the adult gingivitis group at P < 0.01. Matching results between PCR and culture occurred in 28% (B. forsythus) to 71% (A. actinomycetemcomitans) of the samples; the major discrepancy occurred in the PCR-positive/culture-negative category. Matching results between PCR and DNA probe methods were found in 84% of the subjects (B. forsythus) and 70% (P. gingivalis). Odds ratio analysis revealed statistically significant positive associations between 17 of the 28 possible combinations (P < 0.01). This study demonstrated the utility of a 16S rRNA-based PCR detection method for identifying important subgingival microorganisms. The results indicated a strong association between the study species and periodontitis. Several previously unreported symbiotic relationships were found between the 8 species tested.

Polymerase chain reaction detection of 8 putative periodontal pathogens in subgingival plaque of gingivitis and advanced periodontitis lesions

Apical periodontitis is a sequel to endodontic infection and manifests itself as the host defense response to microbial challenge emanating from the root canal system. It is viewed as a dynamic encounter between microbial factors and host defenses at the interface between infected radicular pulp and periodontal ligament that results in local inflammation, resorption of hard tissues, destruction of other periapical tissues, and eventual formation of various histopathological categories of apical periodontitis, commonly referred to as periapical lesions. The treatment of apical periodontitis, as a disease of root canal infection, consists of eradicating microbes or substantially reducing the microbial load from the root canal and preventing re-infection by orthograde root filling. The treatment has a remarkably high degree of success. Nevertheless, endodontic treatment can fail. Most failures occur when treatment procedures, mostly of a technical nature, have not reached a satisfactory standard for the control and elimination of infection. Even when the highest standards and the most careful procedures are followed, failures still occur. This is because there are root canal regions that cannot be cleaned and obturated with existing equipments, materials, and techniques, and thus, infection can persist. In very rare cases, there are also factors located within the inflamed periapical tissue that can interfere with post-treatment healing of the lesion. The data on the biological causes of endodontic failures are recent and scattered in various journals. This communication is meant to provide a comprehensive overview of the etio-pathogenesis of apical periodontitis and the causes of failed endodontic treatments that can be visualized in radiographs as asymptomatic post-treatment periapical radiolucencies.

Pathogenesis of Apical Periodontitis and the Causes of Endodontic Failures

The habit of chewing fresh leaves and twigs of khat (Catha edulis) for their stimulating amphetamine-like effects is highly prevalent in East Africa and southwest on the Arabic peninsula. There is an extensive literature on khat providing information about its history, botany, production, geographical distribution, chemistry and pharmacology, and exploring the social, economic, medical, psychological and oral aspects related to its use. Some of this literature dates as early as the 11th century; however, most of it appeared after the first scientific description of khat by Peter Forskal in 1775. This review provides a panorama of khat and the various aspects of its use. A non-technical description of the plant chemistry and pharmacology is included. The medical, psychological and oral aspects are emphasized, and the current knowledge about the microbiological effects of khat is also presented.

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Khat (Catha edulis)—an updated review

It is generally accepted that oral hygiene maintenance through regular removal of dental plaque and food deposits is an essential factor in the prevention of dental caries and periodontal disease. Methods for oral hygiene vary from country to country and from culture to culture. Despite the widespread use of toothbrushes and toothpastes, natural methods of tooth cleaning using chewing sticks selected and prepared from the twigs, stems or roots from a variety of plant species have been practised for thousands of years in Asia, Africa, the Middle East and the Americas. Selected clinical studies have shown that chewing sticks, when properly used, can be as efficient as toothbrushes in removing dental plaque due to the combined effect of mechanical cleaning and enhanced salivation. It has also been suggested that antimicrobial substances that naturally protect plants against various invading microorganisms or other parasites may leach out into the oral cavity, and that these compounds may benefit the users by protection against cariogenic and periodontopathic bacteria. Some clinical epidemiological studies are in support of this, and many laboratory investigations have suggested the presence of heterogeneous antimicrobial components extractable using different chemical procedures. A few recent studies have identified some of the active antimicrobial compounds. Today, chewing sticks are still used in many developing countries because of religion and or tradition, and because of their availability, low cost and simplicity. The World Health Organization also encourages their use. The Year 2000 Consensus Report on Oral Hygiene states that chewing sticks may have a role to play in the promotion of oral hygiene, and that evaluation of their effectiveness warrants further research.

Chewing sticks: Timeless natural toothbrushes for oral cleansing

Objective: To identify and quantify some potential antimicrobial anionic components in Salvadora persica root and stem aqueous extracts.

Methods: Extraction of powdered root and stem samples was performed by soaking the powder in sterile deionised distilled water for 24 h at 4o C. Each 100mg of the freeze-dried extract was reconstituted with 10 ml deionised distilled water and filtered through a 0.45 (m cellulose acetate filter. The anionic components of the filtered extracts were identified and quantified by capillary electrophoresis.

Results: The root and stem extracts contained chloride, sulphate, thiocyanate and nitrate in the following concentrations (w/w %) in stem and root extracts, respectively: 6.84% and 4.64%, 20.1% and 19.85%, 0.38 and 0.28%, and 0.05% and 0.05%. Only the differences in chloride were statistically significant (p< 0.05).

Conclusion: S. persica contains potential antimicrobial anionic components and that capillary electrophoresis is a convenient method for their identification and quantification.

Identification and quantification of some potentially antimicrobial anionic components in miswak extract.

Bacterial cultivation studies have shown that dental plaque is a reservoir for respiratory pathogens in intensive care unit patients and in elderly who are debilitated, hospitalized or in a nursing home, placing them at risk of bacterial pneumonia. No information is available, however, concerning dental plaque as a reservoir of putative respiratory pathogens in hospitalized patients with chronic lung diseases. Supragingival plaque colonization of 34 hospitalized chronic lung-diseased Romanian citizens, excluding those with tuberculosis and less than 20 teeth, was therefore assessed by checkerboard DNA–DNA hybridization using a selected panel of whole genomic DNA probes produced from eight respiratory pathogens and eight oral pathogens. Thirty-one lung-healthy dental outpatients served as reference population. Respiratory pathogens were detected in plaque from 29 of the 34 (85.3%) hospitalized patients and 12 of the 31 (38.7%) reference population subjects. Staphylococcus aureus, Pseudomonas aeruginosa, Acinetobacter baumannii, and Enterobacter cloacae occurred significantly (p<0.05) more frequent among the hospitalized patients. Hospitalized chronic lung-diseased patients harbored in their supragingival plaque samples bacteria known to cause nosocomial pneumonia significantly (p<0.001) more frequent than lung-healthy dental outpatients. Our results indicate that dental plaque in patients with chronic lung diseases often serves as a reservoir of bacteria known to cause nosocomial pneumonia in susceptible individuals.

Respiratory pathogens in dental plaque of hospitalized patients with chronic lung diseases

Objectives: To assess dentistry-based utilization of the 11 antibiotics prescribed by dentists in Norway and its relative contribution to national outpatient consumption and to determine the relationship between numbers of prescriptions and the consumption of these antibiotics. Methods: Data on national antibiotic prescriptions by dentists in 2004 and 2005 were used. Consumption of the antibiotics was expressed using WHO defined daily doses (DDDs), DDDs per 1000 inhabitants per day (DIDs) and numbers of prescriptions per 1000 inhabitants (PIDs). Results: Analysis of 268 834 prescriptions issued by 4765 dentists showed that the dentists’ prescriptions contributed 8% of the total national consumption of the 11 antibiotics and 13.5%, 2.8% and 1.2% of the national b-lactam penicillins, macrolides and lincosamides and tetracyclines utilization, respectively. The dentists’ contributions to the national phenoxymethylpenicillin, spiramycin and metronidazole consumptions were considerably higher (� 13.2%) than for the other prescribed antibiotics (� 8.6%). There was a strong positive correlation between numbers of DDDs and numbers of prescriptions and between DIDs and numbers of PIDs. Conclusions: Reliance of Norwegian dentists on phenoxymethylpenicillin as their first choice suggests a low prevalence of antibiotic resistance among oral bacteria in Norway. Norwegian dentists prefer to prescribe narrow-spectrum antibiotics; their prescribing is conservative and relatively low compared with that of physicians.

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Nils Skaug

Papers

Khat (Catha edulis)—an updated review

Chewing sticks: Timeless natural toothbrushes for oral cleansing

Identification and quantification of some potentially antimicrobial anionic components in miswak extract.

Respiratory pathogens in dental plaque of hospitalized patients with chronic lung diseases

Incidence of antibiotic prescribing in dental practice in Norway and its contribution to national consumption.