Introduction to microbial aspects of periodontal biofilm communities, development and treatment

Energy dose parameters affect antimicrobial photodynamic therapy-mediated eradication of periopathogenic biofilm and planktonic cultures

OBJECTIVE

This study evaluated the in vitro efficacy of a commercially available aPDT system in eradication of the periopathogens Porphyromonas gingivalis, Fusobacterium nucleatum, and Aggregatibacter actinomycetemcomitans in both planktonic and biofilm cultures.

BACKGROUND DATA

Antimicrobial photodynamic therapy (aPDT) is an effective antibacterial approach in vitro; however, few data are available regarding effective light-energy parameters.

MATERIALS AND METHODS

Planktonic and biofilm cultures of periopathogens were exposed to a methylene blue-based formulation and irradiated with a 670-nm nonthermal diode laser. Energy doses were varied from 2.3 to 9.4 J/cm(2) through adjustments in illumination time and a constant power density. Controls consisted of no treatment, light only, and photosensitizer only. Temperature changes were recorded in experimental samples before and after illumination.

RESULTS

aPDT with an energy dose of 9.4 J/cm(2) was effective in eradicating P. gingivalis, F. nucleatum, and A. actinomycetemcomitans in biofilm and planktonic form. Reductions from control in planktonic cultures at this energy dose were 6.8 +/- 0.7, 5.2 +/- 0.6, and 1.9 +/- 0.6 log(10), respectively, whereas biofilm reductions were 4.5 +/- 1.2, 3.4 +/- 1.1, and 4.9 +/- 1.4 log(10). Decreasing the treatment time produced an energy dose-dependent killing effect in both models. Changes in sample temperature did not exceed 3 degrees C under these exposure parameters.

CONCLUSION

This study demonstrated that three important periopathogens are susceptible to aPDT-mediated killing, regardless of whether they are present in planktonic or biofilm form. Furthermore, a clear energy dose-dependence exists with this treatment that should to be taken into account when determining optimal treatment times in clinical application.

Occurrence of Aggregatibacter actinomycetemcomitans in Brazilians with chronic periodontitis

Studies have suggested that A. actinomycetemcomitans is involved in the aetiology of aggressive periodontitis as well as in chronic periodontitis. This study was aimed at elucidating the occurrence of A. actinomycetemcomitans in a Brazilian population with chronic periodontitis. A total of 555 (mean age 33.04 +/- 12.45) individuals, living in two large areas of the São Paulo State, namely "Baixada Santista" and "Vale do Paraíba", and diagnosed with mild [180 (mean age 29.59 +/- 10.94)], moderate [241 (mean age 31.18 +/- 11.45)] or severe [134 (mean age 33.04 +/- 12.45)] chronic periodontitis were enrolled in this survey. Clinical exams including measurements of Probing Depth, Clinical Attachment Loss, Plaque and Gingival indices and subgingival microbiological assessments were performed at all population. The genomic DNA of A. actinomycetemcomitans was identified by Polymerase Chain Reaction from periodontal pocket samples. The occurrence of A. actinomycetemcomitans among chronic periodontitis subjects as well as its association with age and gender were statistically analysed using the Chi-square and Odds Ratio tests. The significance of differences was established at 5% (p < 0.05). A. actinomycetemcomitans was detected in 102 (18.37%) individuals: 29 (16.11%) mild; 42 (17.42%) moderate; and 31 (23.13%) severe chronic periodontitis with no statistical difference among groups. A higher occurrence of the searched bacterium was found both in the youngest group (p < 0.05) as well as in the female group (p < 0.05). This study elucidated that A. actinomycetemcomitans harbored subgingival pockets of our target group of chronic periodontitis subjects and that this bacterium seems to be inversely related to age, but related to the female gender.

Inflammation and genetic risk indicators for early periodontitis in adults

BACKGROUND

This report is a further analysis of a study designed to determine clinical and microbial risk indicators for progressing periodontitis.

METHODS

One hundred ninety subjects who were periodontally healthy or had early signs of periodontitis (age range: 20 to 40 years) were monitored clinically at 6-month intervals followed by supragingival cleaning. At each visit, gingival crevicular fluid (GCF) and blood were collected for determination of interleukin (IL)-1β content (in GCF) and IL-1 genotype (in blood). Interproximal sites with a >1.5-mm increase in clinical attachment over 18 months were considered disease active. Characteristics were compared between active and inactive subjects.

RESULTS

IL-1β levels in GCF increased with the severity of disease and correlated well with clinical signs of incipient disease. However, the IL-1 genotype did not show any significant associations with disease or the extent of disease.

CONCLUSION

Indicators of inflammation may be important clinical determinants of future periodontal disease progression, but the IL-1 genotype was not a risk indictor for early (slight) periodontitis as defined in this subject population.

Systemic endotoxin levels in chronic indolent periodontal infections

BACKGROUND AND OBJECTIVE

Periodontal disease has been linked with an increased risk of various systemic diseases. A plausible biologic explanation for this link includes the opportunity for oral pathogens to translocate to the circulation as a result of breakdown in integrity of the oral epithelium. This study refined a methodology used to detect endotoxin activity in the serum of subjects with indolent periodontal infections.

MATERIAL AND METHODS

The QCL Kinetic Chromogenic Assay (Cambrex) is a kinetic measure of endotoxin activity. Sera from 211 pregnant women with periodontitis enrolled in the Obstetrics and Periodontal Therapy Trial were used to develop the assay further and to evaluate the detection of endotoxin activity that might accompany a low-level bacteremia in chronic periodontitis.

RESULTS

We optimized the system to increase the sensitivity and reproducibility of the assay. The refined system was able to detect endotoxin activity in serum at > 0.0125 EU/mL. At baseline (13-16 wk of gestation), 35.5% of the women were positive for endotoxin activity (1.62 +/- 2.21; range: 0.38-15 EU/mL).

CONCLUSION

This report describes a sensitive measure of endotoxin activity in serum. The procedure allowed us to document levels of this microbial virulence factor in serum of individuals with indolent infections such as periodontal disease.

Evaluating clinical periodontal measures as surrogates for bacterial exposure: the Oral Infections and Vascular Disease Epidemiology Study (INVEST)

Background

Epidemiologic studies of periodontal infection as a risk factor for cardiovascular disease often use clinical periodontal measures as a surrogate for the underlying bacterial exposure of interest. There are currently no methodological studies evaluating which clinical periodontal measures best reflect the levels of subgingival bacterial colonization in population-based settings. We investigated the characteristics of clinical periodontal definitions that were most representative of exposure to bacterial species that are believed to be either markers, or themselves etiologic, of periodontal disease.

Methods

706 men and women aged ≥ 55 years, residing in northern Manhattan were enrolled. Using DNA-DNA checkerboard hybridization in subgingival biofilms, standardized values for Aggregatibacter actinomycetemcomitans, Porphyromonas gingivalis, Treponema denticola and Tannerella forsythia were averaged within mouth and summed to define "bacterial burden". Correlations of bacterial burden with clinical periodontal constructs defined by the severity and extent of attachment loss (AL), pocket depth (PD) and bleeding on probing (BOP) were assessed.

Results

Clinical periodontal constructs demonstrating the highest correlations with bacterial burden were: i) percent of sites with BOP (r = 0.62); ii) percent of sites with PD ≥ 3 mm (r = 0.61); and iii) number of sites with BOP (r = 0.59). Increasing PD or AL severity thresholds consistently attenuated correlations, i.e., the correlation of bacterial burden with the percent of sites with PD ≥ 8 mm was only r = 0.16.

Conclusions

Clinical exposure definitions of periodontal disease should incorporate relatively shallow pockets to best reflect whole mouth exposure to bacterial burden.

Lasers and the treatment of chronic periodontitis

For many intraoral soft-tissue surgical procedures the laser has become a desirable and dependable alternative to traditional scalpel surgery. However, the use of dental lasers in periodontal therapy is controversial. This article presents the current peer-reviewed evidence on the use of dental lasers for the treatment of chronic periodontitis.

Immunoglobulin G (IgG) class, but Not IgA or IgM, antibodies to peptides of the Porphyromonas gingivalis chaperone HtpG predict health in subjects with periodontitis by a fluorescence enzyme-linked immunosorbent assay

Chaperones are molecules found in all cells and are critical in stabilization of synthesized proteins, in repair/removal of defective proteins, and as immunodominant antigens in innate and adaptive immunity. Subjects with gingivitis colonized by the oral pathogen Porphyromonas gingivalis previously demonstrated levels of anti-human chaperone Hsp90 that were highest in individuals with the best oral health. We hypothesized that similar antibodies to pathogen chaperones might be protective in periodontitis. This study examined the relationship between antibodies to P. gingivalis HtpG and clinical statuses of healthy and periodontitis-susceptible subjects. We measured the humoral responses (immunoglobulin G [IgG], IgA, and IgM) to peptides of a unique insert (P18) found in Bacteroidaceae HtpG by using a high-throughput, quantitative fluorescence enzyme-linked immunosorbent assay. Indeed, higher levels of IgG class anti-P. gingivalis HtpG P18 peptide (P < 0.05) and P18alpha, consisting of the N-terminal 16 amino acids of P18 (P < 0.05), were associated with better oral health; these results were opposite of those found with anti-P. gingivalis whole-cell antibodies and levels of the bacterium in the subgingival biofilm. When we examined the same sera for IgA and IgM class antibodies, we found no significant relationship to subject clinical status. The relationship between anti-P18 levels and clinical populations and individual subjects was found to be improved when we normalized the anti-P18alpha values to those for anti-P18gamma (the central 16 amino acids of P18). That same ratio correlated with the improvement in tissue attachment gain after treatment (P < 0.05). We suggest that anti-P. gingivalis HtpG P18alpha antibodies are protective in periodontal disease and may have prognostic value for guidance of individual patient treatment.

TNF-alpha and antibodies to periodontal bacteria discriminate between Alzheimer's disease patients and normal subjects

The associations of inflammation/immune responses with clinical presentations of Alzheimer's disease (AD) remain unclear. We hypothesized that TNF-alpha and elevated antibodies to periodontal bacteria would be greater in AD compared to normal controls (NL) and their combination would aid clinical diagnosis of AD. Plasma TNF-alpha and antibodies against periodontal bacteria were elevated in AD patients compared with NL and independently associated with AD. The number of positive IgG to periodontal bacteria incremented the TNF-alpha classification of clinical AD and NL. This study shows that TNF-alpha and elevated numbers of antibodies against periodontal bacteria associate with AD and contribute to the AD diagnosis.

The history of dentistry and medicine relationship: could the mouth finally return to the body?

The relationship between dentistry and medicine has been acknowledged throughout the history of humanity. This relationship was documented in ancient medicine accounts, and has survived until the present day, accompanied by the evolution of molecular technologies. Although we have had very important researchers' contributions in this interdisciplinary area, mainly after the 18th century, the knowledge on oral infections is still ignored by or unknown to the majority of clinical dentists and physicians. These circumstances could be changed through a broader divulgation of this complex relationship, both in the dentistry and in the medicine areas, which in turn would have a significant impact in systemic health worldwide. This movement has already started, as was observed in a World Health Assembly resolution which called for oral health to be integrated into chronic disease prevention programs in 2007. This was a significant indicator of changing perceptions of oral health over the past several decades. This brief review reports the evolution through time of the knowledge on the association between dental infections and systemic diseases, as well as the paths which we could take to consolidate this historical trend.

Antimicrobial therapy in periodontitis: the use of systemic antimicrobials against the subgingival biofilm

OBJECTIVES

The aim was to answer three relevant questions: can systemic antimicrobials be efficacious if the biofilm is not disrupted? Can the type of debridement of the subgingival biofilm impact upon the clinical outcomes of the adjunctive antimicrobial therapy? Is the efficacy of the adjunctive systemic antimicrobial therapy dependent on the quality of the debridement of the subgingival biofilm and the sequence debridement-antibiotic usage?

MATERIAL AND METHODS

Relevant papers were searched, critically analysed and their data were extracted.

RESULTS

For the first question, studies assessing susceptibility of bacteria in biofilms, and clinical studies evaluating systemic antimicrobials as monotherapy, were reviewed. For the second question, clinical studies comparing systemic antimicrobials as adjuncts to non-surgical debridement or to periodontal surgery and clinical trials using systemic antibiotics with periodontal surgery were evaluated. For the third question, a previous systematic review was updated.

CONCLUSION

If systemic antimicrobials are indicated in periodontal therapy, they should be adjunctive to mechanical debridement. There is not enough evidence to support their use with periodontal surgery. Indirect evidence suggests that antibiotic intake should start on the day of debridement completion, debridement should be completed within a short time (preferably <1 week) and with an adequate quality, to optimize the results.

Inhibition of Experimental Periodontitis by a Topical Boron-based Antimicrobial

AN0128 is a boron-containing compound with antibacterial and anti-inflammatory properties. To test its potential effectiveness in treating periodontal disease, we induced experimental periodontitis in the rat by placing ligatures and assessed the impact of AN0128 and positive and negative controls by micro-CT and histologic measurements. The formation of an inflammatory infiltrate was measured in hematoxylin-and-eosin-stained sections. Daily application of AN0128 (1%) compared with controls reduced bone loss by 38 to 44% (P < 0.05), while vehicle alone had no effect (P > 0.05). The reduction in bone loss with AN0128 was similar to that achieved with a NSAID, ketorolac, and Total toothpaste containing triclosan. AN0128 also reduced the level of gingival inflammation 42% compared with the ligature only (P < 0.05), whereas vehicle alone had no effect (P > 0.05). The results indicate that AN0128 significantly reduces the formation of an inflammatory infiltrate and reduces bone loss, measured histologically and by micro-CT.

Adapting to changes in molecular biosciences and technologies

Dental education, like any other educational programme in a research-intensive university environment, must be research led or at least research informed. In this context, as the research and knowledge base of dentistry lies in the biological and physical sciences, dental education must be led by advances in research in both these areas. There is no doubt that biotechnology and nanotechnology have, over the past 25 years, led research in both these areas. It is therefore logical to assume that this has also impacted on dental education. The aim of this paper is twofold; on one hand to examine the effects of biotechnology and nanotechnology and their implications for dental education and on the other to make recommendations for future developments in dental education led by research in biotechnology and nanotechnology. It is now generally accepted that dental education should be socially and culturally relevant and directed to the community it serves. In other words, there can be no universal approach and each dental school or indeed curriculum must apply the outcomes in their own social, cultural and community settings.

Uncultivated Tannerella BU045 and BU063 are slim segmented filamentous rods of high prevalence but low abundance in inflammatory disease-associated dental plaques

Uncultivated clones BU045 and BU063 and Tannerella forsythia, a 'consensus periodontal pathogen', are the closest known relatives within the genus Tannerella. They have been described to inhabit different ecological niches of the human oral cavity. In this study, fluorescent in situ hybridization (FISH) and immunofluorescence were combined to investigate the prevalence and abundance of BU045 and BU063 in comparison to T. forsythia in plaques from gingivitis, necrotizing ulcerative gingivitis (NUG) and chronic periodontitis. Phylotype-specific FISH probes identified BU045 and BU063 as elongated thin rods with a segmented structure. Two structurally similar and previously unknown, rare phylotypes (127+ and 997+) were also identified due to partial 16S rRNA sequence identity with T. forsythia. In gingivitis, NUG and periodontitis patients, BU045, BU063, 127+, 997+ and T. forsythia were detected with prevalences of 50/83/71/14 and 81%, 100/100/86/17 and 53%, and 100/100/12/0 and 100%, respectively. Supragingivally, colonization density of all five organisms was generally low, rarely exceeding 0.1% of the total biota. In periodontal pocket samples, however, cell numbers of T. forsythia, but not of the uncultivable phylotypes, were greatly elevated. Our data demonstrate that Tannerella phylotypes BU045, BU063, 127+ and 997+ consist of long slim rods with segments, which, with respect to FISH stainability, often behaved as independent units. The phylotypes are frequent but low-level colonizers of various periodontal disease-associated plaques. Their apparent inability to proliferate to high density seems to exclude any relevance for the pathogenesis of periodontal diseases.

Clinical changes following four different periodontal therapies for the treatment of chronic periodontitis: 1-year results

OBJECTIVE

To compare clinical changes occurring in chronic periodontitis subjects receiving SRP alone or with systemically administered azithromycin, metronidazole or a sub-antimicrobial dose of doxycycline.

MATERIAL AND METHODS

92 chronic periodontitis subjects were randomly assigned to receive SRP alone (N=23) or combined with 500 mg azithromycin per day for 3 days (N=25), 250 mg metronidazole tid for 14 days (N=24) or 20 mg doxycycline bid for 3 months (N=20). Gingival redness, bleeding on probing, suppuration, pocket depth and attachment level were measured at baseline and 3, 6 and 12 months post therapy. The significance of changes in clinical parameters within groups over time was sought using the Friedman test and among groups using ANCOVA or the Kruskal Wallis test.

RESULTS

All groups showed clinical improvements at 12 months, with subjects receiving adjunctive agents showing a somewhat better response. Sites with initial pocket depth > 6 mm showed significantly greater pocket depth reduction and greater attachment gain in subjects receiving metronidazole or azithromycin than subjects in the other groups. Some subjects showed attachment loss at 12 months in each group ranging from 15% to 39% of subjects in the SDD and SRP only groups respectively.

CONCLUSION

This study, demonstrated that periodontal therapy provides clinical benefits and that antibiotics provide a clinical benefit over SRP alone, particularly at initially deeper periodontal pockets.

The proteomic profile of Fusobacterium nucleatum is regulated by growth pH

Fusobacterium nucleatum is a saccharolytic Gram-negative anaerobic organism believed to play an important role in the microbial succession associated with the development of periodontal disease. Its genome contains niche-specific genes shared with the other inhabitants of dental plaque, which may help to explain its ability to survive and grow in the changing environmental conditions experienced in the gingival sulcus during the transition from health to disease. The pH of the gingival sulcus increases during the development of periodontitis and this is thought to occur by the metabolism of nutrients supplied by gingival crevicular fluid. In comparison with other plaque inhabitants, F. nucleatum has the greatest ability to neutralize acidic environments. The differential expression of soluble cytoplasmic proteins induced by acidic (pH 6.4) or basic (pH 7.4 and 7.8) conditions, during long-term anaerobic growth in a chemostat, was identified by two-dimensional gel electrophoresis and image analysis software. Twenty-two proteins, found to have altered expression in response to external pH, were identified by tryptic digestion and mass spectrometry. Eight differentially expressed proteins associated with increased energy (ATP) production via the 2-oxoglutarate and Embden-Meyerhof pathways appeared to be directed towards either cellular biosynthesis or the maintenance of internal homeostasis. Overall, these results represent the first proteomic investigation of F. nucleatum and the identification of gene products which may be important in the organism's persistence during the transition from health to disease in vivo.