These findings suggest that detectable dental bacteraemias induced by periodontal procedures are at a lower level than previously reported.

A relatively wide range of bacteria have been isolated from root canals using standard culture techniques. However, only 50% of the bacteria in the oral cavity are cultivable (S. S. Socransky et al., Arch. Oral Biol. 8:278-280, 1963); hence, bacterial diversity in endodontic infections is underestimated. This study used a PCR-based 16S rRNA gene assay, followed by cloning and sequencing of 16S rRNA amplicons from a small subset of samples to assess the diversity of bacteria present in infected root canals. A total of 41 clinical samples from 15 de novo and 26 refractory cases of endodontic infections were assessed. Of these samples, 44% were positive by culture and 68% were positive by PCR. Eight samples were selected for further analysis. Of these, the two de novo cases yielded sequences related to those of the genera Enterococcus, Lactobacillus, Propionibacterium, and Streptococcus and two clones were related to previously uncultivated bacteria, while the sinus-associated, de novo case yielded sequences related to those of the genera Lactobacillus, Pantoea, Prevotella, and Selenomonas. The five refractory cases produced clones which were related to the genera Capnocytophaga, Cytophaga, Dialister, Eubacterium, Fusobacterium, Gemella, Mogibacterium, Peptostreptococcus, Prevotella, Propionibacterium, Selenomonas, Solobacterium, Streptococcus, and Veillonella and two clones representing previously uncultivated bacteria. The phylogenetic positions of several clones associated with the Clostridiaceae and Sporomusa subgroups of the Firmicutes grouping are also shown. This study demonstrates that molecular techniques can detect the presence of bacteria in endodontic infections when culture techniques yield a negative result and can be used to identify a wider range of endodontic-infection-related bacteria including the presence of previously unidentified or unculturable bacteria.

Current data indicate that smokers with periodontal disease have a suppressed inflammatory response, a significantly less favourable clinical outcome and seem to have an altered host antibody response to antigenic challenge than non-smokers. In contrast, the subgingival microflora of smokers appears similar to that of non-smokers.

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A number of bacterial species are involved in the aetiology of periodontitis and include Actinobacillus actinomycetemcomitans, Porphyromonas gingivalis, Prevotella intermedia, Bacteroides forsythus and Treponema denticola. Several studies have shown differences in the microflora between the various forms of periodontal disease. It is recognised that smoking is a risk factor for periodontal disease, but there are conflicting reports on whether or not smoking has an effect on the periodontal microflora. We utilised the polymerase chain reaction to determine the presence of A. actinomycetemcomitans, P. gingivalis, P. intermedia, B. forsythus and T. denticola in subgingival plaque samples in 33 adult periodontitis (AP) patients and 24 generalized early-onset periodontitis (GEOP) patients prior to treatment. When GEOP and AP patients were compared there were significant differences in the number of positive patients and sites for both A. actinomycetemcomitans and B. forsythus (p=0.0023 and 0.00001, respectively). No statistically significant differences in the prevalence of these organisms were found between smoker and non-smoker groups. These results confirm that AP and GEOP sites harbour varied microflora, but show that B. forsythus and A. actinomycetemcomitans were detected to a significantly greater extent in this group of GEOP than in the AP patients investigated. Our findings do not support the hypothesis that smokers have significant differences in the prevalence of periodontal pathogens from non-smokers.

SRP was effective in reducing clinical parameters in both groups. The inferior improvement in PD following therapy for smokers may reflect the systemic effects of smoking on the host response and the healing process. The lesser reduction in microflora and greater post-therapy prevalence of organisms may reflect the deeper pockets seen in smokers and poorer clearance of the organisms. These detrimental consequences for smokers appear consistent in both aggressive and CP.

In this study, the major periodontal pathogens Actinobacillus actinomycetemcomitans and Porphyromonas gingivalis were detected in subgingival plaque samples from patients with periodontal disease by polymerase chain reaction (PCR) and conventional culture methods. 170 plaque samples from 43 patients were analysed; A. actinomycetemcomitans and P. gingivalis were each detected in 40 (24%) of samples by PCR, whereas conventional culture methods detected A. actinomycetemcomitans and P. gingivalis in 25 (15%) and 18 (11%) of samples, respectively. The proportion of patients carrying A. actinomycetemcomitans in at least 1 sampled periodontal site was 17/43 (40%) by PCR and 13/43 (30%) by culture; for P. gingivalis this was 12/43 (28%) by PCR and 9/43 (21%) by culture. Only 5 samples, from 3 patients, harboured both A. actinomycetemcomitans and P. gingivalis. It is concluded that PCR is more accurate than conventional culture methods for identification of these periodontal pathogens in subgingival plaque samples and has a higher frequency of detection.