Oral microbiota in subjects with a weak or strong response in experimental gingivitis

Cytokine profiles and the dynamic of gingivitis development in humans

AIM

To investigate the relationship between cytokine profiles and "fast" and "slow" patterns of gingival inflammation development.

MATERIALS AND METHODS

Forty-two adults participated in an experimental gingivitis study, comprising a 2-week hygiene phase (clinical examination and professional cleaning); a 3-week induction phase (absence of oral hygiene); and a 2-week resolution phase (re-establishment of oral hygiene). Plaque and gingival inflammation scores were assessed. Interferon-gamma (IFN-γ), interleukin (IL)-1β, IL-2, IL-4, IL-6, IL-8, IL-10, IL-12p70, IL-13, and tumour necrosis factor-alpha (TNF-α) from gingival crevicular fluid were collected and measured by multiplex ELISA. Group-based-trajectory-modelling (GBTM) was used to model cytokine profiles over the induction phase. The effect of gingival inflammation on cytokine levels over time was estimated with mixed-effects modelling.

RESULTS

GBTM analysis revealed two cytokine profiles, "non-organized response" (IL-4, IL-6, IL-8, IL-12, and IL-13) and "organized response" (IL-2, IL-10, and TNF-α). Among the "slow" responders, neither cytokine profile was associated with gingivitis. In contrast, a "fast" response was associated with a higher "non-organized response" factor (coef. 0.14) and a lower "organized response" factor (coef. -0.03).

CONCLUSION

A "fast" gingivitis development was associated with a higher "non-organized response" and a lower "organized response", which may elucidate the role of individual variability in gingivitis susceptibility.

Plaque-induced gingivitis: Case definition and diagnostic considerations

OBJECTIVE

Clinical gingival inflammation is a well-defined site-specific condition for which several measurement systems have been proposed and validated, and epidemiological studies consistently indicate its high prevalence globally. However, it is clear that defining and grading a gingival inflammatory condition at a site level (i.e. a "gingivitis site") is completely different from defining and grading a "gingivitis case" (GC) (i.e. a patient affected by gingivitis), and that a "gingivitis site" does not necessarily mean a "GC". The purpose of the present review is to summarize the evidence on clinical, biochemical, microbiologic, genetic markers as well as symptoms associated with plaque-induced gingivitis and to propose a set of criteria to define GC.

IMPORTANCE

A universally accepted case definition for gingivitis would provide the necessary information to enable oral health professionals to assess the effectiveness of their prevention strategies and treatment regimens; help set priorities for therapeutic actions/programs by health care providers; and undertake surveillance.

FINDINGS

Based on available methods to assess gingival inflammation, GC could be simply, objectively and accurately identified and graded using bleeding on probing score (BOP%) CONCLUSIONS: A patient with intact periodontium would be diagnosed as a GC according to a BOP score ≥ 10%, further classified as localized (BOP score ≥ 10% and ≤30%) or generalized (BOP score > 30%). The proposed classification may also apply to patients with a reduced periodontium, where a GC would characterize a patient with attachment loss and BOP score ≥ 10%, but without BOP in any site probing ≥4 mm in depth.

Comparison of red autofluorescing plaque and disclosed plaque-a cross-sectional study

Objectives

The aim of this cross-sectional study was to assess the correlation between dental plaque scores determined by the measurement of red autofluorescence or by visualization with a two-tone solution. Clinical photographs were used for this study.

Materials and methods

Overnight plaque from the anterior teeth of 48 participants was assessed for red fluorescence on photographs (taken with a QLF-camera) using a modified Quigley & Hein (mQH) index. A two-tone disclosing solution was applied. Total disclosed plaque was clinically assessed using the mQH index. In addition, total and blue disclosed plaque was scored on clinical photographs using the mQH index.

Results

A strong correlation was observed between the total disclosed plaque scored on photographs and the clinical scores (r = 0.70 at site level; r = 0.88 at subject level). The correlation between red fluorescent plaque and total plaque, as assessed on the photographs, was moderate to strong and significant (r = 0.50 at the site level; r = 0.70 at the subject level), with the total plaque scores consistently higher than the red fluorescent plaque scores. The correlation between red fluorescent plaque and blue disclosed plaque was weak to moderate and significant (r = 0.30 at the site level; r = 0.50 at the subject level).

Conclusions

Plaque, as scored on white-light photographs, corresponds well with clinically assessed plaque. A weak to moderate correlation between red fluorescing plaque and total disclosed plaque or blue disclosed plaque was found.

Clinical relevance

What at present is considered to be matured dental plaque, which appears blue following the application of a two-tone disclosing solution, is not in agreement with red fluorescent dental plaque assessment.

In vitro assessment of shiitake mushroom (Lentinula edodes) extract for its antigingivitis activity

Gingivitis is a preventable disease characterised by inflammation of the gums due to the buildup of a microbial biofilm at the gingival margin. It is implicated as a precursor to periodontitis, a much more serious problem which includes associated bone loss. Unfortunately, due to poor oral hygiene among the general population, gingivitis is prevalent and results in high treatment costs. Consequently, the option of treating gingivitis using functional foods, which promote oral health, is an attractive one. Medicinal mushrooms, including shiitake, have long been known for their immune system boosting as well as antimicrobial effects; however, they have not been employed in the treatment of oral disease. In the current study, the effectiveness of shiitake mushroom extract was compared to that of the active component in the leading gingivitis mouthwash, containing chlorhexidine, in an artificial mouth model (constant depth film fermenter). The total bacterial numbers as well as numbers of eight key taxa in the oral community were investigated over time using multiplex qPCR. The results indicated that shiitake mushroom extract lowered the numbers of some pathogenic taxa without affecting the taxa associated with health, unlike chlorhexidine which has a limited effect on all taxa.

Gingival tissue transcriptomes in experimental gingivitis

AIMS

We investigated the sequential gene expression in the gingiva during the induction and resolution of experimental gingivitis.

MATERIAL AND METHODS

Twenty periodontally and systemically healthy non-smoking volunteers participated in a 3-week experimental gingivitis protocol, followed by debridement and 2-week regular plaque control. We recorded clinical indices and harvested gingival tissue samples from four interproximal palatal sites in half of the participants at baseline, Day 7, Day 14 and Day 21 (the "induction phase"), and at Day 21, Day 25, Day 30 and Day 35 in the other half (the "resolution phase"). RNA was extracted, amplified, reversed transcribed, amplified, labelled and hybridized using Affymetrix Human Genome U133Plus2.0 microarrays. Paired t-tests compared gene expression changes between consecutive time points. Gene ontology analyses summarized the expression patterns into biologically relevant categories.

RESULTS

The median gingival index was 0 at baseline, 2 at Day 21 and 1 at Day 35. Differential gene regulation peaked during the third week of induction and the first 4 days of resolution. Leucocyte transmigration, cell adhesion and antigen processing/presentation were the top differentially regulated pathways.

CONCLUSIONS

Transcriptomic studies enhance our understanding of the pathobiology of the reversible inflammatory gingival lesion and provide a detailed account of the dynamic tissue responses during the induction and resolution of experimental gingivitis.

Interleukin-1 beta levels in gingival crevicular fluid and serum under naturally occurring and experimentally induced gingivitis

AIMS

To evaluate the interleukin-1 beta (IL-1 beta) levels in gingival crevicular fluid (GCF) and serum in either naturally occurring (N-O) or experimentally induced (E-I) plaque-associated gingivitis.

MATERIAL AND METHODS

Thirty-seven periodontally healthy subjects were evaluated in real life conditions (N-O gingivitis) as well as after 21 days of experimental gingivitis trial (E-I gingivitis). During the experimental gingivitis trial, in one maxillary quadrant (test quadrant), gingival inflammation was induced by oral hygiene abstention, while in the contralateral (control) quadrant, oral hygiene was routinely continued. IL-1 beta concentrations in N-O and E-I gingivitis were investigated for IL-1B(+3954) and IL-1B(-511) gene polymorphisms.

RESULTS

(i) GCF IL-1 beta concentrations in E-I gingivitis were significantly higher compared with N-O gingivitis; (ii) an intra-individual correlation between GCF concentrations of IL-1 beta detected in N-O and E-I gingivitis was observed in control quadrants, but not in test quadrants; (iii) IL-1 beta concentration in GCF was associated with IL-1B(+3954) genotype only at test quadrants; (iv) IL-1 beta was detectable in serum only at low levels in a limited number of subjects, without difference between gingivitis conditions.

CONCLUSIONS

Aspects of the bacterial challenge to the gingival tissues, such as the amount of plaque deposits and plaque accumulation rate, appear to affect the IL-1 beta levels in GCF in subjects with a specific IL-1B genotype.

Effect of triclosan/copolymer-containing toothpaste on the association between plaque and gingival bleeding: a randomized controlled clinical trial

AIM

To study longitudinal associations between plaque and gingival bleeding and multilevel variance/covariance structures after introducing triclosan-containing toothpaste.

MATERIAL AND METHODS

A 10-week, randomized, two-arm, double-masked, controlled clinical trial was conducted in 34 healthy, non-smoking females with plaque-induced gingivitis. Clinical periodontal examinations were repeated every other week. At week 4, test toothpaste containing 0.24% sodium monofluorophosphate, 0.3% triclosan, and 2% polyvinyl-methyl ether maleic acid; or control toothpaste containing 0.76% sodium monofluorophosphate and 0.1% sodium fluoride, were randomly distributed.

RESULTS

Multivariate multilevel models indicated that, after introducing experimental toothpastes, subject random error was reduced from 0.6 to below 0.2. The odds ratio (OR) of bleeding on probing (BOP) was about 30% less in the test than in the control group (p<0.01). At the end of the experiment, ORs for BOP and plaque index scores 1-3 (reference 0) were 2.1-2.4 in the control group, but 1.1-1.9 in the test group (p<0.05). No effects on plaque levels and calculus were observed.

CONCLUSIONS

Multivariate multilevel modelling allows the study of fixed and random effects of experimental toothpastes on gingival inflammation in small sample. Triclosan appears to attenuate the causal association between supragingival plaque and gingival bleeding in gingivitis.

Modeling shifts in microbial populations associated with health or disease

Stable microbial communities associated with health can be disrupted by altered environmental conditions. Periodontal diseases are associated with changes in the resident oral microflora. For example, as gingivitis develops, a key change in the microbial composition of dental plaque is the ascendancy of Actinomyces spp. and gram-negative rods at the expense of Streptococcus spp. We describe the use of an in vitro model to replicate this population shift, first with a dual-species model (Actinomyces naeslundii and Streptococcus sobrinus) and then using a microcosm model of dental plaque. The population shift was induced by environmental changes associated with gingivitis, first by the addition of artificial gingival crevicular fluid and then by a switch to a microaerophilic atmosphere. In addition to the observed population shifts, confocal laser scanning microscopy also revealed structural changes and differences in the distribution of viable and nonviable bacteria associated with the change in environmental conditions. This model provides an appropriate system for the further understanding of microbial population shifts associated with gingivitis and for the testing of, for example, antimicrobial agents.

Time as a factor in the identification of subjects with different susceptibility to plaque-induced gingivitis

OBJECTIVES

The purpose of this study was to assess whether identification of subjects with different susceptibility to plaque-induced gingival inflammation is dependent on the length of time of de novo plaque accumulation.

METHODS

Retrospective analysis of data obtained from a recently reported randomized split-mouth localized experimental gingivitis trial involving 96 healthy non-smokers. Gingival and plaque index, gingival crevicular fluid volume (GCF), angulated bleeding score, and the derived parameter cumulative plaque exposure (CPE) were recorded at days 0, 7, 14, and 21. The primary outcome variable to express severity of inflammation was GCF and each subject was a statistical unit. Based on subject distribution of GCF-day 21 residuals after standardization for CPE-day 21, two sub-populations (upper and lower distribution quartiles) were selected. They were, respectively, defined as "high responders" (HR) (n=24) and "low responders" (LR) (n=24) and characterized by significantly different severity of gingivitis to similar amounts of plaque deposits. The same analysis was repeated at days 7 and 14. Prevalence of HR and LR was compared between days using the chi(2) [ML] test.

RESULTS

For both day 7 and day 14, the quartile distribution of LR and HR was statistically significant (p=0.02). Fifty percent of LR and 71% of HR presented a consistent level of susceptibility to plaque-induced gingival inflammation even after only 7 and/or 14 days of plaque accumulation.

CONCLUSIONS

These findings support the concept that the subject-based susceptibility to plaque-induced gingival inflammation is an individual trait, only partly related to the length of time of exposure to plaque.

The salivary microbiota as a diagnostic indicator of oral cancer: a descriptive, non-randomized study of cancer-free and oral squamous cell carcinoma subjects

Background

The purpose of the present investigation was to determine if the salivary counts of 40 common oral bacteria in subjects with an oral squamous cell carcinoma (OSCC) lesion would differ from those found in cancer-free (OSCC-free) controls.

Methods

Unstimulated saliva samples were collected from 229 OSCC-free and 45 OSCC subjects and evaluated for their content of 40 common oral bacteria using checkerboard DNA-DNA hybridization. DNA counts per ml saliva were determined for each species, averaged across subjects in the 2 subject groups, and significance of differences between groups determined using the Mann-Whitney test and adjusted for multiple comparisons. Diagnostic sensitivity and specificity in detection of OSCC by levels of salivary organisms were computed and comparisons made separately between a non-matched group of 45 OSCC subjects and 229 controls and a group of 45 OSCC subjects and 45 controls matched by age, gender and smoking history.

Results

Counts of 3 of the 40 species tested, Capnocytophaga gingivalis, Prevotella melaninogenica and Streptococcus mitis, were elevated in the saliva of individuals with OSCC (p < 0.001). When tested as diagnostic markers the 3 species were found to predict 80% of cancer cases (sensitivity) while excluding 83% of controls (specificity) in the non-matched group. Diagnostic sensitivity and specificity in the matched group were 80% and 82% respectively.

Conclusion

High salivary counts of C. gingivalis, P. melaninogenica and S. mitis may be diagnostic indicators of OSCC.

Reducing variability and choosing ideal subjects for experimental gingivitis studies

INTRODUCTION

This study was undertaken to test the hypothesis that male, non-smokers, aged 25-50 years, with a proven track record of developing gingivitis would provide suitable subjects for experimental gingivitis studies because the inter-subject variation would be greatly reduced.

MATERIALS AND METHODS

Subjects were required to be men aged between 25 and 50 years, in good general health with at least four sound teeth in one posterior quadrant of the mandible. Subjects who were smokers, taking antibiotics, anti-inflammatory drugs or had any other medical, surgical or social condition making participation in the study inadvisable, were excluded. Subjects had previously participated in a 21-day experimental gingivitis study. Subjects with the most gingivitis at the end of the previous study were invited to participate first, moving down the list until the required number of subjects had been achieved. Subjects were randomly assigned to one of three toothpastes: Crest Gum Care, Mentadent P or a placebo (UK Signal). Subjects were asked to brush their teeth twice daily for 1 min., with the tooth-shield in place and containing 1 ml of their assigned toothpaste.

RESULTS

Thirty-five subjects completed the study using the placebo, 36 used Mentadent P and 39 completed the study using Crest Gum Care. Both toothpastes containing active gum health ingredients (Triclosan and Zinc Citrate in Mentadent P and Stannous Fluoride in Crest Gum Care) resulted in statistically significant reductions in gingival bleeding and inflammation. Although a directional reduction, there was no statistically significant reduction in plaque scores. No significant differences between the two active groups were established.

CONCLUSION

The factors that were controlled or measured and analyzed in these studies were: gender, smoking status, age and chronic gingivitis level. The results add support to the hypothesis that male subjects show less variation, however there is limited evidence linking the female menstrual cycles to variations in gingivitis status. Further research in this area is required before definitive conclusions can be made. Selecting a subject population in order to decrease variation must be undertaken with caution. A subject population selected for particular attributes can be extremely valuable when assessing the anti-gingivitis potential of new agents, but this population would be as biased if used for large efficacy clinical trials. The data obtained will not necessarily be able to be generalized, that is, applicable to the whole population. However there is sufficient evidence to justify balancing for (or excluding) smokers from subject populations in experimental gingivitis studies.

Experimental gingivitis in cigarette smokers: a clinical and microbiological study

OBJECTIVE

To assess clinical and microbiological changes during experimental gingivitis in cigarette smokers and non-smokers.

MATERIAL AND METHODS

Eleven current smokers (>/=5 years) and 11 (never-) non-smokers periodontally healthy or with gingivitis (PPD</=4 mm) were included. According to the original model (Löe et al. 1965), an experimental 3-week plaque accumulation period resulting in experimental gingivitis and a subsequent 2-week period of optimal plaque control were performed. Subgingival plaque samples were collected at days 0, 21 and 35 from one site per quadrant, pooled and analysed using checkerboard DNA-DNA hybridization.

RESULTS

Smokers {mean age: 24.7+/-2.2 [standard deviation (SD)] years, range 21-28 years} had a mean lifetime cigarette exposure of 6.4+/-2.8 (SD) pack-years, while non-smokers presented with a mean age of 23.1+/-2.2 (SD) years (range 21-29 years). Between days 0, 21 and 35, no statistically significant differences in mean Plaque and mean Gingival Index scores were observed between smokers and non-smokers. In both smokers and non-smokers, mean total DNA probe counts did not significantly differ nor increase between days 0 and 21. Also, between days 21 and 35 they did not significantly differ nor decrease. This was also true for the various proportions of bacterial complexes.

CONCLUSION

Both current smokers and (never-) non-smokers reacted to experimental plaque accumulation with gingival inflammation. Periodontal and microbiological parameters assessed in current cigarette smokers did not significantly differ from those in non-smokers during an identical period of experimental plaque accumulation. Hence, the early host response to the bacterial challenge appears to be of similar magnitude and timing in both groups.

Modulation of clinical expression of plaque-induced gingivitis. I. Background review and rationale

OBJECTIVES

The purpose of this article is to provide the necessary background and rationale for the accompanying studies, which are ultimately aimed at identifying genetic and environmental factors determining gingivitis susceptibility.

MATERIALS AND METHODS

The literature on factors reported to modify the clinical expression of gingivitis, i.e., factors that determine individual variability in gingival inflammatory response to plaque, is presented.

RESULTS

Clinical evidence suggests that the gingival inflammatory response to plaque accumulation may differ substantially among individuals. However, most of the available studies are of small scale and not purposely designed to address the issue. Systemic factors implicated in modulation of the clinical expression of gingivitis include metabolic, genetic, environmental and other factors. The significance of such factors in designing and conducting a large-scale experimental gingivitis trial and means to account for them are discussed.

CONCLUSION

Although several factors have been implicated, genetic or environmental factors underlying differences in gingivitis expression are not fully elucidated. The accompanying studies aim to identify and characterize, among participants in a specifically designed large-scale experimental gingivitis trial, subjects that differ significantly in their gingival inflammatory response to plaque. This is the first step in an effort to determine genetic or environmental factors underlying such differences.

Effects of periodontitis and smoking on the microbiota of oral mucous membranes and saliva in systemically healthy subjects

BACKGROUND/AIM

To examine the differences in the proportions of 40 bacterial species in samples from eight oral soft-tissue surfaces and saliva in systemically healthy adult subjects with and without periodontitis and in smokers and nonsmokers.

METHODS

Saliva and microbial samples were taken from eight oral soft-tissue surfaces in 229 systemically healthy subjects stratified by periodontal and smoking status. Subjects included 84 periodontally healthy and 145 periodontitis individuals. Of these, there were 182 nonsmokers and 47 smokers. Soft-tissue samples were taken using a "buccal brush" and saliva was taken by expectoration. All samples were individually evaluated for their content of 40 bacterial species using checkerboard DNA-DNA hybridization. The percentage of total DNA probe count was determined for each species at each sample location and averaged across subjects. The significance of differences among the proportions of the 40 test species at different sample locations was sought in these populations using the Kruskall-Wallis test and adjusted for multiple comparisons.

RESULTS

When stratified for periodontal status or smoking status, microbial profiles at most sites did not differ significantly. Generally, periodontal pathogens were found at higher levels on the soft tissues of periodontitis subjects than in periodontally healthy subjects, and at higher levels in smokers than nonsmokers. Few significant differences were found, although trends in the populations were noted.

CONCLUSIONS

Small differences in the proportions of bacterial species were observed on soft tissues and in saliva comparing periodontally healthy and periodontitis subjects. Somewhat greater differences between smokers and nonsmokers were found; however, these were not statistically significant.

Longitudinal association between plaque and gingival bleeding in smokers and non-smokers

BACKGROUND/AIMS

Whereas accumulation of dentogingival plaque inevitably leads to inflammatory reactions in the adjacent gingival tissue, there is limited information with regard to factors influencing naturally occurring fluctuation between gingival health and disease. The major aims of the present study were to investigate site-specific associations between plaque and gingivitis as well as transition dynamics of naturally occurring gingivitis in smoking and non-smoking young adults.

METHODS

65 systemically healthy young adults, 19 to 30 years old, participated. 33 volunteers smoked at least 20 cigarettes per day, whereas 32 subjects were non-smokers. Clinical periodontal conditions were assessed four times within a time period of 6 months. An ecological approach in data analysis as well as site-specific analyses considering the correlated structure of data were performed.

RESULTS

At the outset and after 6 months, smokers had significantly more supragingival plaque than non-smokers. At the final examination, bleeding upon probing as well as calculus were more prevalent in smokers. A site-by-site analysis revealed that smokers tended to have a weaker association between supragingival plaque and bleeding on probing than non-smokers (median Mantel-Haenszel's common odds ratio 1.91 vs. 2.89, p=0.07). Multiple logistic regression analyses adjusted for periodontal probing depth, plaque and calculus identified smoking status to significantly increase the risk for the first transition of non-bleeding to bleeding upon probing by 86% (p<0.01). In contrast, recovery of bleeding sites was positively influenced by female gender, but not smoking.

CONCLUSIONS

In multivariate analyses adjusted for probing depth, plaque and calculus, smokers appeared to be at higher risk for the transition from non-bleeding to bleeding on probing. Weaker associations between plaque and naturally occurring gingivitis in smokers may have important consequences for preventive strategies for gingivitis.

Gingival crevicular fluid inflammatory mediators and bacteriology of gingivitis in nonhuman primates related to susceptibility to periodontitis

The hypothesis to be tested was that the microbiota and resulting local host inflammatory response characteristics in oral conditions of high levels of chronic gingival inflammation increases susceptibility to progressing periodontitis. This study used cynomolgus monkeys, Macaca fascicularis (nonhuman primates), with high and low levels of long-standing gingival inflammation to define the profiles of gingival crevicular fluid mediators, cytokines and immunoglobulins; describe the subgingival microbiota; and evaluate their susceptibility to ligature-induced periodontitis. Sixteen nonhuman primates were stratified into two groups (HI, LO) based upon Bleeding Index as a measure of the natural level of inflammation (HI = 1.26 +/- 0.45; LO = 0.22 +/- 0.16). The host mediator levels, subgingival microbiota, and clinical characteristics of the LO and HI groups were compared after 30 days of oral hygiene, during a 30 day experimental gingivitis (7, 14, and 30 days), and during periodontitis (30, 60, and 90 days). The results demonstrated that nonhuman primates with high levels of long-standing gingival inflammation when compared to those nonhuman primates with low inflammation show: 1) different inflammatory mediator profiles in gingival crevicular fluid (particularly for immunoglobulin A (IgA) and IgG levels), 2) a different quantitative and qualitative subgingival microbiota; and 3) a similar progression of periodontitis. Thus, while variations in host inflammatory responses to local factors exist in the nonhuman primates, an extensive subgingival challenge (such as ligation) may negate these individual differences.

Oral microbiota in smokers and non-smokers in natural and experimentally-induced gingivitis

The present study primarily aimed at investigating the oral microbiota in smokers and non-smokers with established gingivitis and monitoring its composition during experimental gingivitis. Secondly, it aimed at examining whether the composition of the microbiota is associated with different levels of gingival inflammation during this experimental gingivitis trial. For this purpose, 25 non-dental university students with gingivitis were recruited. 11 subjects were smokers and 14 were non-smokers. After achieving gingival health, they entered a 14-day experimental gingivitis trial. Plaque and bleeding were assessed before entering into the study (intake), at day 0, day 5 and at day 14 of the experiment. Microbiological samples from mucosal sites and dental plaque (taken at intake, day 0, and day 14) were analysed for the presence of Actinomyces species, Actinobacillus actinomycetemcomitans, Bacteroides forsythus, Campylobacter rectus, Fusobacterium nucleatum, Peptostreptococcus micros, Porphyromonas gingivalis, Prevotella intermedia and Streptococcus species. At day 14 of the experimental period, the level of plaque formation was not different between smokers and non-smokers, but bleeding scores were lower in smokers than in non-smokers (15% and 30% respectively, p=0.01). The change from natural gingivitis to a state of gingival health and a subsequent change from gingival health to experimentally induced gingivitis was accompanied by quantitative alterations in the cultivable microbiota in both groups. Changes were most prominent in the transition from gingival health to experimental gingivitis and were found in dental plaque for Actinomyces species, C. rectus, F. nucleatum, and P. intermedia. Within the group of non-smokers, a distinction was made between subjects with a 'weak' or 'strong' inflammatory response. No relationship with a single bacterial species could be established which would likely explain the differences in levels of inflammation. It is concluded that differences in response to experimental gingivitis are not caused by major differences in the composition of the oral microbiota.

Gram-positive anaerobic cocci

Gram-positive anaerobic cocci (GPAC) are a heterogeneous group of organisms defined by their morphological appearance and their inability to grow in the presence of oxygen; most clinical isolates are identified to species in the genus Peptostreptococcus. GPAC are part of the normal flora of all mucocutaneous surfaces and are often isolated from infections such as deep organ abscesses, obstetric and gynecological sepsis, and intraoral infections. They have been little studied for several reasons, which include an inadequate classification, difficulties with laboratory identification, and the mixed nature of the infections from which they are usually isolated. Nucleic acid studies indicate that the classification is in need of radical revision at the genus level. Several species of Peptostreptococcus have recently been described, but others still await formal recognition. Identification has been based on carbohydrate fermentation tests, but most GPAC are asaccharolytic and use the products of protein degradation for their metabolism; the introduction of commercially available preformed enzyme kits affords a physiologically more appropriate method of identification, which is simple and relatively rapid and can be used in routine diagnostic laboratories. Recent reports have documented the isolation in pure culture of several species, notably Peptostreptococcus magnus, from serious infections. Studies of P. magnus have elucidated several virulence factors which correlate with the site of infection, and reveal some similarities to Staphylococcus aureus. P. micros is a strongly proteolytic species; it is increasingly recognized as an important pathogen in intraoral infections, particularly periodontitis, and mixed anaerobic deep-organ abscesses. Comparison of antibiotic susceptibility patterns reveals major differences between species. Penicillins are the antibiotics of choice, although some strains of P. anaerobius show broad-spectrum beta-lactam resistance.

Prevalence and distribution of six capsular serotypes of Porphyromonas gingivalis in periodontitis patients

Previous reports have described six serotypes based on K antigens in Porphyromonas gingivalis strains. The purpose of the present study was to investigate the prevalence and distribution of these serotypes in 185 patients with P. gingivalis-associated periodontitis. Polyclonal rabbit antisera, raised against each of the different type strains, were used in double-immunodiffusion and immunoelectrophoresis assays. In addition, a subset of 76 strains was investigated for the presence of capsular structures by means of the India ink and Bruce White staining techniques. These strains were also tested for auto-aggregation in phosphate-buffered saline (PBS). All six K serotypes were present in the study sample. In total, 84 (45.4%) patients were colonized with a K-typeable P. gingivalis strain with a predominance of types K5 (12%) and K6 (23.2%). A correlation was found between arbitrary age categories and the prevalence of currently known K serotypes, which were found in 60% of patients aged 12 to 30 years, in 49% of patients aged 31 to 50, and in 25% of patients aged 51 to 70 years. In the subset of 76 P. gingivalis strains, 32 (42.1%) were K-typeable. Fifty-three strains (69.7%) showed microscopic evidence of encapsulation, suggesting the existence of K serotypes other than K1 to K6. Twenty-one strains (27.6%) auto-aggregated in PBS and were not K-typeable, nor did they show any evidence of encapsulation. It was concluded that the majority of clinical P. gingivalis isolates is encapsulated and that encapsulation is associated with the presence of a K antigen. Auto-aggregation seems to be associated with the absence of a capsular structure and, consequently, the absence of a K antigen.

The design and implementation of trials of host modulation agents

Over the last two decades it has become more evident that although oral microorganisms are essential agents of periodontal pathogenesis, interpatient variability in the host response is a major determinant of the expression of periodontal disease extent and severity. Data from animal models and human studies have identified many of the components of the host inflammatory response which serve as critical mediators of clinical inflammation, attachment loss, and bone resorption. Studies suggest that certain pharmacologic agents, which act at a molecular level to block specific inflammatory mediators, appear to attenuate disease progression. These promising findings herald a new era in periodontal medicine. Anti-infective therapies may soon be supplemented with anti-inflammatory pharmacological agents. However, there are many unanswered issues regarding formulation design, clinical application, potential indication claims, and clinical study design. Furthermore, current considerations of fundamental mechanisms of pathogenesis, as well as new data from epidemiologic studies emphasizing the multifactorial nature of disease, are changing the underlying assumptions which have served to guide our design of anti-infective drug trials over the last two decades. There are new questions regarding appropriate outcome measurements which are to be reconsidered. For example, the measurement of a change in periodontal disease status, either during progression or in response to therapy, is fundamentally unidimensional and may be only mildly informative when one considers that the disease is multifactorial by nature. Using an example from intensive care medicine, pathophysiologic studies of septic shock have demonstrated that the microbial dose and the host inflammatory mediator response are far better predictors of patient morbidity and mortality than any combination of clinical signs associated with clinical shock. Clinical trials of anti-cytokine and anti-inflammatory drugs to treat shock are now designed and conducted taking strategic advantage of this knowledge by including measurements of microbial dose and host response. It appears prudent that the design and implementation of clinical trials of host modulation agents also benefit from our current insights into pathogenesis and not represent a template-driven adaptation of historical, anti-infective clinical trial protocols.