Methanogenic archaea in subgingival sites: a review.

Archaea are non-bacterial prokaryotes associated with oral microbiota in humans, but their roles in oral pathologies remain controversial. Several studies reported the molecular detection of methanogenic archaea from periodontitis, but the significance of this association has not been confirmed yet. An electronic search was therefore conducted in MEDLINE-Pubmed to identify all papers published in English connecting archaea and periodontal infections. Data analysis of the selected studies showed that five genera of methanogenic archaea have been detected in the subgingival microbiota, Methanobrevibacter oralis being the most frequently detected species in 41% of periodontitis patients and 55% of periodontal pockets compared to 6% of healthy subjects and 5% of periodontally-healthy sites (p < 10(-5) , Chi-squared test). Based on the five determination-criteria proposed by Socransky (association with disease, elimination of the organism, host response, animal pathogenicity and mechanisms of pathogenicity), M. oralis is a periodontal pathogen. The methanogenic archaea load correlating with periodontitis severity further supports the pathogenic role of methanogenic archaea in periodontitis. Therefore, detection and quantification of M. oralis in periodontal pockets could help the laboratory diagnosis and follow-up of periodontitis. Determining the origin, diversity and pathogenesis of archaea in periodontal infections warrants further investigations.

Microbial sampling process can change results of microbiological analysis in periodontitis diagnosis. A minireview.

This minireview aims to verify the supposition that the microbial sampling process can change results of microbiological analysis in periodontitis diagnosis. The literature search via Pubmed yielded 52 appropriate articles for analysis. Of which 38% (20/52) described that the sampling sites were isolated from saliva, whereas 62% (32/52) did not. Also, 29% (15/52) declared that the microbial sampling was performed before probing pocket depth (PPD), whereas 71% (37/52) did not. Comparison of the results of microbiological analysis in these studies showed that the bacteria most frequently detected in periodontal pockets was variable. Therefore, a sampling process that includes both the microbial sample being taken before PPD and saliva isolation of the sampling sites is needed to ensure the accuracy of microbiological analysis in periodontitis diagnosis.

Heat degradation of eukaryotic and bacterial DNA: an experimental model for paleomicrobiology.

BACKGROUND: Theoretical models suggest that DNA degradation would sharply limit the PCR-based detection of both eukaryotic and prokaryotic DNA within ancient specimens. However, the relative extent of decay of eukaryote and prokaryote DNA over time is a matter of debate. In this study, the murine macrophage cell line J774, alone or infected with Mycobacterium smegmatis bacteria, were killed after exposure to 90°C dry heat for intervals ranging from 1 to 48 h in order to compare eukaryotic cells, extracellular bacteria and intracellular bacteria. The sizes of the resulting mycobacterial rpoB and murine rpb2 homologous gene fragments were then determined by real-time PCR and fluorescent probing. FINDINGS: The cycle threshold (Ct) values of PCR-amplified DNA fragments from J774 cells and the M. smegmatis negative controls (without heat exposure) varied from 26-33 for the J774 rpb2 gene fragments and from 24-29 for M. smegmatis rpoB fragments. After 90°C dry heat incubation for up to 48 h, the Ct values of test samples increased relative to those of the controls for each amplicon size. For each dry heat exposure time, the Ct values of the 146-149-bp fragments were lower than those of 746-747-bp fragments. During the 4- to 24-h dry heat incubation, the non-infected J774 cell DNA was degraded into 597-bp rpb2 fragments. After 48 h, however, only 450-bp rpb2 fragments of both non-infected and infected J774 cells could be amplified. In contrast, the 746-bp rpoB fragments of M. smegmatis DNA could be amplified after the 48-h dry heat exposure in all experiments. Infected and non-infected J774 cell DNA was degraded more rapidly than M. smegmatis DNA after dry heat exposure (ANOVA test, p < 0.05). CONCLUSION: In this study, mycobacterial DNA was more resistant to dry-heat stress than eukaryotic DNA. Therefore, the detection of large, experimental, ancient mycobacterial DNA fragments is a suitable approach for paleomicrobiological studies.

Gingival recession associated with predisposing factors in young vietnamese: a pilot study.

AIMS: Several studies have shown a large diversity in the prevalence, extent and severity of gingival recession as well as controversial conclusions of its associated factors. Therefore, the aim of this pilot study was to evaluate gingival recession with predisposing factors in young Vietnamese. METHODS: A cross-sectional study using clinical examination was performed in 120 dental students. Oral hygiene status, tooth malposition and fraenal attachment were recorded. The width of keratinised gingiva was measured after mucosa staining with Lugol's iodine solution. Measurements of gingival recession were performed on labial tooth surfaces. Chisquare test, t-test and Pearsonâs correlation were used for data analysis. RESULTS: The prevalence of gingival recession was 72.5% of the studied population. The extent of affected teeth was 11.1% of the examined teeth. The proportion of root-surface exposure was statistically higher (P<0.05) in the maxilla (12.5%) than in the mandible (9.6%). Premolars and right canines were the teeth most frequently and most seriously associated with gingival recession, respectively. There was a strong negative correlation between narrow width of keratinised gingiva and gingival recession (P<0.001). The recession was statistically associated with tooth malposition (P<0.001) but it was not related to high fraenal attachment and gender. CONCLUSIONS: A high prevalence of gingival recession was found in Vietnamese dental students. Gingival recession was associated with narrow width of keratinised gingiva, tooth malposition and maxillary teeth. Further studies performed in larger populations with more extended age groups are needed to confirm these findings.

Peri-implantitis: from diagnosis to therapeutics.

Peri-implantitis is an infection of the tissue around an implant, resulting in the loss of supporting bone. Risk factors for peri-implantitis consist of a history of periodontitis, dental plaque, poor oral hygiene, smoking, alcohol consumption and diabetes. A clinical diagnosis indicates inflammatory signs including bleeding on probing with or without suppuration and a peri-implant pocket depth ≥5 mm. A radiograph shows images of marginal bone loss ≥2 mm. A differential diagnosis of peri-implant mucositis, occlusal overload, retrograde peri-implantitis and inflammatory implant periapical lesions suggests the appropriate treatment in each case. The non-surgical treatment of peri-implantitis, including a mechanical treatment alone or combined with antiseptics or antibiotics can improve clinical parameters in the short term but residual defects may still persist. Surgical treatment such as guided bone regeneration results in a gain of clinical attachment level and bone reconstruction in the long term. The limited effect of laser-assisted therapy needs to be further evaluated. The concept of prevention based on early detection and regular maintenance plays a principal role in reducing the occurrence of peri-implantitis.

Evidence of a louse-borne outbreak involving typhus in Douai, 1710-1712 during the war of Spanish succession.

BACKGROUND: The new field of paleomicrobiology allows past outbreaks to be identified by testing dental pulp of human remains with PCR. METHODS: We identified a mass grave in Douai, France dating from the early XVIII(th) century. This city was besieged during the European war of Spanish succession. We tested dental pulp from 1192 teeth (including 40 from Douai) by quantitative PCR (qPCR) for R. prowazekii and B. quintana. We also used ultra-sensitive suicide PCR to detect R. prowazekii and genotyped positive samples. RESULTS AND DISCUSSION: In the Douai remains, we identified one case of B. quintana infection (by qPCR) and R. prowazekii (by suicide PCR) in 6/21 individuals (29%). The R. prowazekii was genotype B, a genotype previously found in a Spanish isolate obtained in the first part of the XX(th) century. CONCLUSION: Louse-borne outbreaks were raging during the XVIII(th) century; our results support the hypothesis that typhus was imported into Europe by Spanish soldiers from America.