Darkground microscopy of subgingival plaque from the top to the bottom of the periodontal pocket

Porphyromonas gingivalis Outer Membrane Vesicles Mediate Coaggregation and Piggybacking of Treponema denticola and Lachnoanaerobaculum saburreum

Porphyromonas gingivalis sheds outer membrane vesicles that contain several virulence factors, including adhesins. In this study, we investigated the ability of P. gingivalis outer membrane vesicles to mediate the coaggregation and piggybacking of Treponema denticola and Lachnoanaerobaculum saburreum. Marked coaggregation between T. denticola and L. saburreum occurred in the presence of P. gingivalis outer membrane vesicles. Sucrose was an effective chemoattractant for the motile species T. denticola. The addition of outer membrane vesicles to a mixture of T. denticola and L. saburreum significantly increased the number of nonmotile bacteria that migrated into a sucrose-filled capillary tube immersed in the bacterial mixture. Under optimal conditions, the number of nonmotile L. saburreum in the capillary tube increased approximately 5-fold, whereas no increase occurred when boiled vesicles were used. This study showed that P. gingivalis outer membrane vesicles mediate coaggregation between T. denticola and L. saburreum and that nonmotile bacteria can be translocated by piggybacking on spirochetes.

Biofilms: survival mechanisms of clinically relevant microorganisms

Though biofilms were first described by Antonie van Leeuwenhoek, the theory describing the biofilm process was not developed until 1978. We now understand that biofilms are universal, occurring in aquatic and industrial water systems as well as a large number of environments and medical devices relevant for public health. Using tools such as the scanning electron microscope and, more recently, the confocal laser scanning microscope, biofilm researchers now understand that biofilms are not unstructured, homogeneous deposits of cells and accumulated slime, but complex communities of surface-associated cells enclosed in a polymer matrix containing open water channels. Further studies have shown that the biofilm phenotype can be described in terms of the genes expressed by biofilm-associated cells. Microorganisms growing in a biofilm are highly resistant to antimicrobial agents by one or more mechanisms. Biofilm-associated microorganisms have been shown to be associated with several human diseases, such as native valve endocarditis and cystic fibrosis, and to colonize a wide variety of medical devices. Though epidemiologic evidence points to biofilms as a source of several infectious diseases, the exact mechanisms by which biofilm-associated microorganisms elicit disease are poorly understood. Detachment of cells or cell aggregates, production of endotoxin, increased resistance to the host immune system, and provision of a niche for the generation of resistant organisms are all biofilm processes which could initiate the disease process. Effective strategies to prevent or control biofilms on medical devices must take into consideration the unique and tenacious nature of biofilms. Current intervention strategies are designed to prevent initial device colonization, minimize microbial cell attachment to the device, penetrate the biofilm matrix and kill the associated cells, or remove the device from the patient. In the future, treatments may be based on inhibition of genes involved in cell attachment and biofilm formation.

Clinical usefulness of microbiological diagnostic tools in the management of periodontal disease

Periodontal diseases comprises a group of chronic inflammatory conditions affecting tooth supporting structures. It has been known for a long time that pathogenic oral bacteria colonizing the tooth surface are associated with the initiation of the disease process. However, to date, a dozen or so bacterial species have been implicated in the pathogenesis of periodontal disease and no one species by itself is synonymous with disease onset. This multibacterial etiology renders the diagnosis of active periodontal disease based on microbiological data difficult. Numerous studies have attempted to relate the usefulness of microbiological diagnostic aids such as microscopy, bacterial culture, immunological and enzymatic assays. Furthermore, recent technical advances have resulted in the use of nucleic acid probes and amplification techniques for the identification of genetic material belonging to potential periodontal pathogens. Despite the availability of a large number of microbiological testing protocols, identification of the microbial etiological agents remains hampered by the complexity of the microbial challenge during periodontal disease. This review discusses the clinical usefulness of these tests in detection and management of periodontal disease.

Dark field microscopy of the subgingival microflora in insulin-dependent diabetics

The subgingival microflora was assessed by means of dark field microscopy in 106 pockets of 47 subjects with long-term insulin-dependent diabetes mellitus (IDD). The microbiota of 55 healthy sulci (probing depth < 4 mm) and 51 periodontally diseased (probing depth > or = 4 and 6 mm) pockets were analyzed. The mean duration of the IDD of the diabetic subjects was 23.7 years (range from 10 to 41 years). The diabetic patients, aged 30-65 years, were under medical treatment at the III Department of Medicine, University of Helsinki Central Hospital, and at 2 clinics of the Helsinki Health Centre. Based upon their long-term medical records, 26 subjects were assessed to have poorly controlled insulin-dependent diabetes mellitus (PIDD) and 21 had controlled insulin-dependent diabetes (CIDD). The PIDD subjects exhibited higher mean blood glucose levels (12.9 +/- 4.6 mmol/l, mean +/- S.D.) than the CIDD subjects (7.9 +/- 3.6 mmol/l) (p < 0.001, t-test). The mean glycosylated hemoglobin HBA1 (HBA1c) levels were 11.2 +/- 4.6% (10.3 +/- 1.2%) and 8.8 +/- 1.8% (7.7 +/- 1.4%) for PIDD and CIDD subjects, respectively. These differences were statistically significant (p < 0.01 and p < 0.001, t-test). For each individual, site-specific recordings were made for plaque index and bleeding index scores, probing depth, loss of attachment and radiographic loss of alveolar bone. Dark field microscopy analysis of the presence of spirochetes, motile rods, cocci, non-motile rods, filaments and fusiforms was performed in the total of 106 pockets. According to the results of the dark field microscopy, the % of spirochetes and motile rods in the periodontally diseased pockets was significantly higher in the PIDD than in the CIDD subjects (9.2 +/- 13.4% and 10.8 +/- 14.3% versus 4.0 +/- 5.2% and 3.1 +/- 3.2%, p < 0.01 and p < 0.001, chi 2-test, respectively). Moreover, the PIDD subjects had lower mean %s of coccoid cells in periodontally diseased sites than the CIDD subjects (52.1 +/- 20.8% versus 60.7 +/- 9.0%, p < 0.001, chi 2-test).

The effect of partial denture connectors on gingival health

The effect on the gingiva of a variety of relationships of a removable partial denture connector to the gingival margin was investigated in 10 subjects. Acrylic resin baseplates were designed incorporating a variety of relationships of the connector to the gingival margin. The appliances were worn for a 12 hour period daily, for 21 days. At baseline and at days 7, 21 and 49, plaque index, gingival index and probing pocket depth measurements were recorded, and subgingival plaque samples were examined using darkfield microscopy. No increase in plaque accumulation was detected in any area at any time interval. There was a significant increase in gingival index at day 21 in areas where the appliance covered the gingival margin. Small increases in probing pocket depth were recorded at day 21, there being no difference between any of the test areas. Baseline values were re-established by day 49. No significant differences were detected in the percentage of motile organisms or spirochaetes counted in the subgingival plaque samples collected from any area. It was concluded that deterioration in gingival health occurred rapidly following the insertion of a removable appliance, and that coverage of the gingival margin, irrespective of the degree of gingival relief, had a detrimental effect.