Plaque Microflora Research Articles

Effect of an Antibacterial Varnish on Mutans Streptococci in Plaque from Enamel Adjacent to Orthodontic Appliances

The effect of an antibacterial varnish (Cervitec) on the levels of mutans streptococci in plaque adjacent to bonded orthodontic brackets was evaluated in 18 children using a split-mouth technique with a placebo varnish control. The test varnish contained 1% chlorhexidine and 1% thymol as active ingredients. Both varnishes were applied on four occasions during a 3-month period, and plaque was subsequently collected between 1 week and 6 months after the onset of treatment. All teeth involved in the study were carefully examined and clinically assessed for enamel demineralization prior to onset of the fixed appliances and immediately after debonding. The results showed a more frequent growth of mutans streptococci in the dental plaque collected from placebo-treated quadrants as compared with the test quadrants on all sampling occasions. The proportion of mutans streptococci within the plaque microflora was significantly (p < 0.05-0.01) lower on the test sides than on the opposite sides at the 1-week and 1-month examinations. The incidence of incipient enamel lesions around the brackets and along the gingival margin was generally low, and no differences were found between the test and placebo varnish treated quandrants at the time of debonding. The results suggest that mutans streptococci in plaque from orthodontic patients can be suppressed effectively by topical applications of an antibacterial varnish.

Fluoride Concentration, Mutans Streptococci and Lactobacilli in Plaque from Old Glass lonomer Fillings

Previous studies have found that the fluoride concentration of plaque growing on or adjacent to glass ionomer cement (GIC) is increased and the proportion of mutans streptococci in plaque is reduced. So far, there are only a few studies of the long-term effect of glass ionomer fillings on plaque in vivo. The aim of this study was to determine whether old GIC fillings have effects on plaque fluoride and microflora and whether this effect can be increased by topical application of fluoride on GIC fillings in vivo. The participants were 27 adults with at least 3 GIC fillings about 3 years old. Plaque was collected from sites adjacent to the GIC fillings and from the contralateral teeth, after which a 1.2% fluoride gel was applied to all teeth. Three days later, plaque was collected from the same sites as before. Stimulated saliva was also collected at both appointments. The results show that none of the patients had elevated levels of fluoride in their saliva either before or 3 days after the fluoride treatment. The fluoride concentration was 0.51 microgram/mg protein in plaque on GICs and 0.35 microgram/mg protein in plaque on contralateral teeth (p = 0.028). After the fluoride treatment, the respective fluoride concentrations were 0.59 microgram/mg and 0.75 microgram/mg (p = 0.849). No significant differences in the proportion of mutans streptococci and lactobacilli in plaque from GIC and contralateral teeth were found. The results suggest that the fluoride concentration of plaque growing on old GIC fillings is slightly increased. In this study, however, this had no significant effect on the cariogenic microflora.(ABSTRACT TRUNCATED AT 250 WORDS)

Microbial ecology of dental plaque and its significance in health and disease.

Dental plaque forms naturally on teeth and is of benefit to the host by helping to prevent colonization by exogenous species. The bacterial composition of plaque remains relatively stable despite regular exposure to minor environmental perturbations. This stability (microbial homeostasis) is due in part to a dynamic balance of both synergistic and antagonistic microbial interactions. However, homeostasis can break down, leading to shifts in the balance of the microflora, thereby predisposing sites to disease. For example, the frequent exposure of plaque to low pH leads to inhibition of acid-sensitive species and the selection of organisms with an aciduric physiology, such as mutans streptococci and lactobacilli. Similarly, plaque accumulation around the gingival margin leads to an inflammatory host response and an increased flow of gingival crevicular fluid. The subgingival microflora shifts from being mainly Gram-positive to being comprised of increased levels of obligately anaerobic, asaccharolytic Gram-negative organisms. It is proposed that disease can be prevented or treated not only by targeting the putative pathogens but also by interfering with the processes that drive the breakdown in homeostasis. Thus, the rate of acid production following sugar intake could be reduced by fluoride, alternative sweeteners, and low concentrations of antimicrobial agents, while oxygenating or redox agents could raise the Eh of periodontal pockets and prevent the growth and metabolism of obligately anaerobic species. These views have been incorporated into a modified hypothesis (the "ecological plaque hypothesis") to explain the relationship between the plaque microflora and the host in health and disease, and to identify new strategies for disease prevention.

The effects of a 0.3% triclosan‐containing dentifrice on the microbial composition of supragingival plaque

144 subjects completed a 6-month, double-blind study which examined the effects of a 0.3% triclosan/2% copolymer/0.243% sodium fluoride dentifrice on the microflora of supragingival dental plaque. The subjects were randomly assigned to use, in an oral hygiene program, either the triclosan/copolymer/fluoride test dentifrice or a control dentifrice. The latter had the same formulation as the test dentifrice except it did not contain triclosan. Supragingival plaque was collected from the buccal and lingual surfaces of 4 teeth at baseline, 3 months, and 6 months, and microbiologically examined by darkfield microscopy, gram stain morphology, immunofluorescence, and selective and non-selective media. Antimicrobial susceptibilities were determined by agar dilution and whole plaque susceptibility methodologies on plaque samples from 136 subjects at each of the above sample periods and at 6-week intervals for an additional 6 months post-therapy. Both dentifrices resulted in highly statistically significant reductions in the total cultivable flora obtained at both the 3 and 6-month samples relative to baseline as well as at 6 months relative to the 3-month sample. The relative decrease in total anaerobic counts and in strict anaerobes, while not statistically significant, was more pronounced at both the 3- and 6-month sample periods in subjects receiving the triclosan dentifrice than for the controls. Neither dentifrice resulted in detrimental shifts in the microbial composition of the normal flora nor led to the emergence of periodontal or opportunistic pathogens.(ABSTRACT TRUNCATED AT 250 WORDS)

Development of a Risk Profile for Periodontal Disease: Microbial and Host Response Factors.

Advances in our understanding of the relationship between the microbial challenge and the host response in periodontal disease have led to the search for pathogenesisbased risk indicators or risk factors for disease progression. This evaluation is based on analysis of non-invasive or minimally invasive samples that allow measurement of the subgingival plaque microflora or the host response in gingival crevicular fluid (GCF), serum, or saliva. Studies conducted by us have indicated that in GCF, persistently elevated levels of β-glucuronidase (βG, a marker for primary granule release from polymorphonuclear leukocytes) are associated with clinical attachment loss in patients with periodontitis. This finding has been confirmed in a multicenter trial. We have also observed that a statistically significant positive correlation exists between βG in GCF and measures of the subgingival microbial challenge, but the correlation was less than 0.5, suggesting variations in the host response to the challenge. Furthermore, βG levels in GCF were inversely correlated with the IgG serum antibody titer to a panel of periodontal pathogens, suggesting the essentially protective function of the systemic humoral response in periodontal disease. Data in the literature support this concept. In addition, recent studies of the relationship of antibody isotypes in GCF to progression of clinical attachment loss have suggested that IgA in GCF has a protective function. This may relate to the lack of complement activation by IgA. Alternately, the development of IgA antigen-specific responses are T-cell dependent, and reductions in local levels of IgA may indicate a decrease in T-helper cell function. These data have allowed development of strategies for identifying individual risk profiles for patients with periodontal disease based on the host response to the microbial challenge. With identification of these risk indicators/risk factors for active periodontal disease, the next challenge is to provide clinicians with access to the tests and analyses that are required for this approach to periodontal diagnosis. Improved patient management should result from the incorporation of these tests into clinical practice. J Periodontol 1994;65:511-520.

年齢と義歯装着に伴う口腔内常在菌叢の変動について

The effects of age and denture-wearing on the composition of the oral microflora in molar plaque and whole saliva were investigated in 40 healthy subjects, 10 of them wore partial dentures.The 30 healthy subjects were divided into three age groups: 20-29 years (group A), 40-51 years (group B) and over 70 years (group C).The denture-wearing subjects were divided into two age groups: 40-52 years (group B′) and over 70 years (group C′).The total viable counts and the number of predominant organisms were similar in all age groups and denture-wearing groups. Whereas some minor groups of aerobes in the oral microflora, i.e., lactobacilli and staphylococci, significantly increased detection frequency (p <0.05) of groups C and C'. The detection frequency (p<0.05) of Candida and lactobacilli in saliva were significantly higher in denture wearers.However, the number of detected organisms was small.The findings of this study indicated that no major changes occur in the oral microflora according to age and denture-wearing.

Caries associated microflora in plaque from orthodontic appliances retained with glass lonomer cement: Anders Hallgren, Anette Oliveby, and Svante Twetman Scand J Dent Res 1992:100(3):140–3

Caries associated microflora in plaque from orthodontic appliances retained with glass lonomer cement: Anders Hallgren, Anette Oliveby, and Svante Twetman Scand J Dent Res 1992:100(3):140–3

Caries associated microflora in plaque from orthodontic appliances retained with glass ionomer cement.

The caries associated microflora in dental plaque adjacent to orthodontic brackets retained with a glass ionomer cement (GIC) and a resin based composite was investigated using the split-mouth technique. 3, 8, and 28 days after the onset of the appliances, 48-h-old plaque was sampled. An increasing prevalence of mutans streptococci and lactobacilli in plaque from both retaining materials was found. A tendency to colonize more frequently around the composite retained brackets was noticed for both types of bacteria. The proportion of mutans streptococci in relation to the total viable count was significantly higher in plaque samples from composite retained brackets compared to GIC retained 1 month after onset of treatment. The results suggest that a less caries inducing microflora may develop when GIC is used as luting agent in orthodontic dentistry.

Comparison of plaque microflora between Chinese and Caucasian population groups

This investigation was designed to compare the predominant plaque micro-organisms from a Chinese group of patients exhibiting periodontitis with an age-, sex- and periodontal disease-matched Caucasian group of patients. In addition to race, the 2 population groups differed with respect to diet and oral hygiene habits, or effectiveness at removing plaque. Clinical measurements were determined along with an evaluation for micro-organisms in supragingival and subgingival plaque. Although the Chinese and Caucasian population groups were similar with respect to composition of micro-organisms in subgingival plaque, notable differences were observed in supragingival plaque. The Chinese group had higher mean proportions of spirochetes, motile rods. Fusobacterium spp. and dark-pigmented Bacteroides species, while the Caucasian group had higher mean proportions of cocci, total Actinomyces spp., A. viscosus and total Streptococcus spp. in supragingival plaque. The microbial differences observed in supragingival plaque may be explained at least in part, if not totally, by the higher plaque index scores of the Chinese versus Caucasian population groups.

Detection of high-risk groups and individuals for periodontal diseases: laboratory markers based on the microbiological analysis of subgingival plaque

Abstract Periodontal microbiology is reviewed with regard to the potential of certain characteristics to serve as markers of high risk groups or individuals for periodontal diseases. The generally accepted associations between particular organisms and the various periodontal diseases are discussed. The usefulness of various clinical study designs is reviewed. The ecology of the subgingival plaque microflora is discussed and a number of suggestions for future research are made. We have concluded that there is no monospecific aetiology to any of the various periodontal conditions. Nevertheless, we give particular attention to the role of the black-pigmented bacteroides based upon our belief that they, and Bacteroides gingivalis in particular, are fundamental to our understanding of the biology of periodontal diseases in humans and other animals. Consequently, the contribution of its various virulence factors and their potential as markers of disease susceptibility and activity is addressed.

Synergistic degradation of bovine serum albumin by mutans streptococci and other dental plaque bacteria

Mutans streptococci ( Streptococcus mutans and Streptococcus sobrinus) exhibited low levels of proteolytic activity against the model protein substrate, FITC-labelled bovine serum albumin, when incubated alone. Inclusion of other members of the dental plaque microflora in the assay usually resulted in marked increases in the degree of proteolysis and a high level of synergy. Interactions between mutans streptococci and either Streptococcus oralis or Fusobacterium nucleatum gave rise to the greatest degree of synergistic proteolytic degradation.

Mutans streptococci and lactobacilli in breast-fed children with rampant caries.

This study aimed to investigate the prevalence of selected components of the oral microflora in breast-fed children who developed rampant caries (resembling nursing caries) under hitherto unexplained circumstances. Dental plaque and saliva samples were collected from breast-fed children, aged between 1 and 2.5 years, with and without rampant caries. Mutans streptococci and lactobacilli were isolated from dental plaque of all children with rampant caries and from most caries-free children. None of the colonies of mutans streptococci resembled those of Streptococcus sobrinus. The mean counts of the mutans streptococci and lactobacilli were 100-fold higher in plaque samples from children with rampant caries as compared with caries-free children. No difference could be found between the numbers of mutans streptococci in plaque overlaying cavities and that from adjacent sound enamel. In contrast, the counts of lactobacilli in plaque were approximately 100-fold higher from cavities than from sound surfaces. The levels of mutans streptococci in saliva were directly related to the presence of rampant caries. The results show that caries-free and caries-active breast-fed children, aged 1 to 2.5 years, harbour mutans streptococci and lactobacilli on their teeth. Rampant caries in these children can occur in the absence of nursing bottles or any other feeding abuse during weaning and in the presence of an aciduric plaque microflora, as has been reported for children with nursing bottle caries.

Synergistic degradation of bovine serum albumin by mutans streptococci and other dental plaque bacteria

Mutans streptococci (Streptococcus mutans and Streptococcus sobrinus) exhibited low levels of proteolytic activity against the model protein substrate, FITC-labelled bovine serum albumin, when incubated alone. Inclusion of other members of the dental plaque microflora in the assay usually resulted in marked increases in the degree of proteolysis and a high level of synergy. Interactions between mutans streptococci and either Streptococcus oralis or Fusobacterium nucleatum gave rise to the greatest degree of synergistic proteolytic degradation.

Age-related microbiological changes in the salivary and plaque microflora of healthy adults

The effect of age on quantitative or qualitative differences in selected bacteria of dental significance and on the carriage of opportunistic pathogens and transient oral species was determined in 79 healthy, non-denture wearing individuals divided into four age groups: 20-39 years (group A), 40-59 years (group B), 60-79 years (group C) and greater than or equal to 80 years (group D). Samples of dental plaque and whole saliva were cultured on appropriate selective and non-selective bacteriological media. The total numbers of viable bacteria in saliva, and the prevalence of mutans streptococci in plaque and saliva were similar in all age groups. Similarly, there was no correlation between the numbers of spirochaetes in plaque and age. In contrast, statistically significantly higher mean proportions (p = 0.004), mean log10 viable counts (p = 0.001) and isolation frequencies (p less than 0.01) of lactobacilli were found in the saliva of those aged greater than or equal to 70 years compared to subjects in group A. The isolation frequency (p less than 0.05) and proportions (p = 0.056) of staphylococci in saliva were also higher in those aged greater than or equal to 70 years. Yeasts were isolated most often and in higher numbers from saliva in those aged greater than or equal to 80 years and the proportion of yeasts was higher after 60 years of age, but these differences were not significant in comparison with results from individuals in group A.(ABSTRACT TRUNCATED AT 250 WORDS)

The Cultivable Microflora of Denture Plaque from Patients with Denture-induced Stomatitis.

Saliva and denture plaque samples were taken from a group of 20 patients with complete dentures who were suffering from denture-induced stomatitis. The samples were cultured and the proportions of a number of microbial groups were determined. The microflora of plaque taken from the fitting surface of the denture was dominated by streptococci, with gram-negative obligate anaerobes forming a smaller proportion although they were consistently present. Candida albicans was isolated from only 60 per cent of the samples and black-pigmented Bacteroides spp. and Staphylococcus aureus were detectable in only 10 per cent and 15 per cent of the samples respectively. The microflora of the saliva samples were similarly dominated by streptococci with gram-negative anaerobes being consistently present. Blackpigmented Bacteroides spp. were isolated from only 15 per cent of the samples, but, in contrast to the plaque specimens, S. aureus was isolated from the saliva of 70 per cent of the patients. C. albicans was cultured from 75 per cent of the saliva samples. The results of this study have demonstrated that the microflora of denture plaque and saliva from patients with denture-induced stomatitis is dominated by bacteria. C. albicans was not consistently isolated and, when present, comprised only a small proportion of the cultivable flora. Keywords: Denture plaque; Denture-induced stomatitis; Microbiology.

Comparison of the Plaque Microflora from Natural and Appliance-Borne Enamel Surfaces

Human enamel sections and slabs, mounted on a mandibular removable appliance, were worn by 5 adult subjects for a 1-week period. Plaque was allowed to accumulate on the in situ test sites and on the adjacent natural dentition. At the end of the experimental period, the plaque microflora associated with (1) the enamel sections, (2) the enamel slabs, and (3) the acrylic base of the appliance test site was compared with that obtained from lingual and interproximal areas of the lower molar teeth. In addition, the acid anion and pH profiles of plaque obtained from both the exogenous and natural tooth surfaces were also determined. Although some quantitative differences were found between the proportions of isolates obtained from the different enamel surfaces, qualitatively the microflora was very similar, and no significant differences were found in the plaque lactate/acetate ratios or pH measurements following a sucrose mouthrinse. Thus, human tooth specimens mounted on the intra-oral device produced a plaque ecosystem similar to that present on the adjacent natural dentition, suggesting that the model is suitable for studies on early plaque development and the microbiology of enamel demineralization.

The Cultivable Microflora of Denture Plaque from Patients with Denture-induced Stomatitis

The Cultivable Microflora of Denture Plaque from Patients with Denture-induced Stomatitis

AnIn SituMicrobiological Study of the Early Colonisation of Human Enamel Surfaces

An appliance model was used in this study to determine the predominant cultivable microflora involved in early dental plaque formation on human enamel surfaces. Twelve enamel slabs were mounted on either side of an intraoral appliance, and the device was worn for periods of 48 h under (1) 'normal' conditions, and (2) with extraoral sucrose applications, nine times daily. Plaque samples were removed from the surface of different slabs at various time-periods, and the bacterial composition determined, with the 4036 isolates being expressed both as percentage and absolute counts. Streptococcus species dominated the plaque microflora at all sampling times, with S. oralis and S. sanguis predominating. A significant increase in total bacterial counts per mm 2 enamel occurred from 2 to 48 h, and although sucrose had little effect on the percentage counts of organisms, most genera and species were present in significantly higher numbers per mm 2 enamel in sites exposed to sucrose. This study demonstrates the importance of expressing results as absolute as well as proportional counts. Furthermore the appliance appears to offer some advantages over previously used models since (1) the use of multiple slabs allows longitudinal studies to be performed and (2) two experimental conditions can be investigated simultaneously, one on each side of the mouth. Keywords: Intraoral appliance; Enamel slabs; Dental plaque.

An Intra-oral Appliance Study of the Plaque Microflora Associated with Early Enamel Demineralization

An intra-oral appliance model was used to investigate the composition of the plaque microflora associated with early enamel demineralization. Enamel sections, with exposed windows, were mounted on lower removable appliances, and the devices were worn by volunteers for three-week periods under three experimental conditions. These were: (1) "normal" plaque conditions, (2) extra-oral sucrose applications nine times daily, and (3) inoculation of each volunteer's own mutans streptococci onto the test sites and sucrose applications as described for (2). After 21 days, the plaque overlying each window was removed, and the bacterial composition was determined. Changes in mineral content of the associated enamel were measured by microradiography and microdensitometry, and the total mineral loss (delta z) that had occurred at each site was calculated. The 144 sites studied were divided into four demineralization groups by delta z value, with an increase in mineral loss from group 1 to group 4. A progressive and significant increase in the isolation frequency of mutans streptococci occurred from delta z group 1 to group 4 sites. These organisms were isolated from the plaque of every location with enamel mineral loss of over 1000 delta z units, but were not detected in 27% of the group 3 sites. Lactobacilli comprised 2% to 3% of the total cultivable microflora in groups 1-3 sites, but were found in significantly higher proportions (18%) at those enamel sites experiencing the most extensive mineral loss (group 4). No significant relationship was found between demineralization and the levels of Actinomyces species or Veillonella.(ABSTRACT TRUNCATED AT 250 WORDS)

Plaque Fluid as a Bacterial Milieu

Studies of the extracellular, free concentrations of substrates, growth factors, inhibitors, and end-products of metabolism to which the intact plaque microflora is exposed in situ can assist in the understanding of factors controlling plaque pathogenicity. Information is becoming increasingly available from analysis of fluid separated by centrifugation of plaques collected at various intervals after an intra-oral pulse of dietary or experimental substrate, or different procedures or treatments having cariostatic potential. Such analytical results give more information than those obtained by analysis of aqueous or other extracts, because they yield values of substrate concentration representing those occurring at the bacterial cell surface. The largest body of information concerns extracellular levels of acid end-products of sugar catabolism in relation to food quality or sequence, and of amino acids and other products of nitrogen metabolism, in relation to studies of the detailed metabolic events of the Stephan curve, and of the demineralizing effect of the plaque environment. Areas where little information is available and which merit further study include plaque clearance of salivary and other components with anti-caries activity (e.g., antibodies, enzymes, fluorides, cations, other antimicrobials, etc.), and substrate concentrations to determine gradients for diffusion into and out of plaque.