Adhesion of actinomyces isolates to experimental pellicles

Inhibitory effect of Lonicera japonica flos on Streptococcus mutans biofilm and mechanism exploration through metabolomic and transcriptomic analyses

Introduction

Streptococcus mutans was the primary pathogenic organism responsible for dental caries. Lonicera japonica flos (LJF) is a traditional herb in Asia and Europe and consumed as a tea beverage for thousands of years.

Methods

The inhibitory effect and mechanism of LJF on biofilm formation by S. mutans was investigated. The active extracts of LJF were validated for their inhibitory activity by examining changes in surface properties such as adherence, hydrophobicity, auto-aggregation abilities, and exopolysaccharides (EPS) production, including water-soluble glucan and water-insoluble glucan.

Results and discussion

LJF primarily inhibited biofilm formation through the reduction of EPS production, resulting in alterations in cell surface characteristics and growth retardation in biofilm formation cycles. Integrated transcriptomic and untargeted metabolomics analyses revealed that EPS production was modulated through two-component systems (TCS), quorum sensing (QS), and phosphotransferase system (PTS) pathways under LJF stress conditions. The sensing histidine kinase VicK was identified as an important target protein, as LJF caused its dysregulated expression and blocked the sensing of autoinducer II (AI-2). This led to the inhibition of response regulator transcriptional factors, down-regulated glycosyltransferase (Gtf) activity, and decreased production of water-insoluble glucans (WIG) and water-soluble glucans (WSG). This is the first exploration of the inhibitory effect and mechanism of LJF on S. mutans, providing a theoretical basis for the application of LJF in functional food, oral health care, and related areas.

Co-operative effect of exogenous dextranase and sodium fluoride on multispecies biofilms

Background/purpose

The co-operative effect of exogenous dextranase (Dex) and sodium fluoride (NaF) on Streptococcus mutans monospecies biofilms is impressive. Here we investigated the effects of the combination on a mature cariogenic multispecies biofilm and analyzed the potential mechanism.

Materials and methods

A multispecies biofilm of S. mutans, Lactobacillus acidophilus, and Actinomyces viscosus was established in vitro. Dex and NaF were added separately or together. The effects of the agents on the biomass were measured. The exopolysaccharide production was determined with the scintillation counting method. The viability and morphology were evaluated using colony forming unit and confocal laser scanning microscopy, respectively.

Results

In general, biofilms treated with Dex and a little concentration of NaF exhibited a lower biomass, exopolysaccharide production, and viability compared with the control group (P < 0.05). Confocal laser scanning microscopy using a vital fluorescence technique showed the combination treated biofilms appeared to be loose relatively and single cells could be observed. Furthermore, the thickness and viability were also lower than either of the separate agent groups (P < 0.05).

Conclusion

Overall, these findings reveal that a combination of 1 U/mL Dex and 80 μg/mL NaF is a promising candidate for disrupting complex cariogenic multispecies biofilms. This feature may be in that Dex loses the structure of biofilms, thereby facilitating NaF penetration and enhancing its antibacterial effects.

In vitro binding interactions of oral bacteria with immobilized fructosyltransferase

AIMS

The objective of the present study was to explore the role of immobilized fructosyltransferase (FTF) in adhesion process.

METHODS AND RESULTS

We investigated real-time biospecific interactions between several types of oral bacteria and recombinant FTF immobilized on a biosensor chip, using surface plasmon resonance technology. Streptococcus mutans, Streptococcus sobrinus and Actinomyces viscosus demonstrated significant binding to FTF. Actinomyces viscosus had a greater binding to FTF, with 373 Resonance Units (RU), than the other tested bacteria. The binding level to FTF of Strep. sobrinus was 320 RU, whereas Strep. mutans and Streptococcus salivarious show binding of 296 and 245 RU, respectively. The binding sensograms displayed different profiles for the tested bacteria at various cell density, suggesting a different affinity to immobilized FTF.

CONCLUSIONS

The results from this study suggest that FTF may influence bacterial adherence and colonization of the dental biofilm.

SIGNIFICANCE AND IMPACT OF THE STUDY

The biomolecular interaction analysis enables real-time monitoring of the interaction between adhesions of intact bacteria and their ligands, which might be crucial in the initial phase of biofilm development in vivo.

Surface plasmon resonance for real-time evaluation of immobilized fructosyltransferase activity

The extracellular enzyme fructosyltransferase (FTF) is considered to be a significant virulence factor in the dental biofilm. We have developed a method using surface plasmon resonance to detect the activity of immobilized FTF in situ. This real time technique provides a sensitive direct assay for characterizing functional properties of immobilized enzymes such as FTF.

Influence of dental biofilm on release of mercury from amalgam exposed to carbamide peroxide

Tooth bleaching is a popular procedure in modern aesthetic dentistry. Bleaching agents may affect amalgam restorations by altering the release of mercury. The aim of this study was to explore the effect of biofilm-coated amalgam restorations on the release of mercury in the presence of carbamide peroxide. Samples of SDI and Valliant amalgams were submerged for either 14 days or 7 months in buffered KCl after which they were coated with saliva, bacteria, and polysaccharides. The samples were exposed to 10% carbamide peroxide (CP) for 24 h. The amount of mercury released was examined for 120 h. Results showed that most of mercury release occurred within the first 24 h, after which the release rate decreased sharply. After 120 h the release of mercury from the tested samples was minimal and similar to the control group. The presence of biofilm coating on the amalgam samples did not induce the release of mercury but tended to reduce mercury release into the surrounding environment. CP induces the release of mercury from amalgam samples. However, the presence of biofilm did not prevent large amounts of mercury release from amalgam coated with biofilms and exposed to CP. This study indicates that dental biofilm may retard the release of mercury from amalgam restorations.

A high molecular mass cranberry constituent reduces mutans streptococci level in saliva and inhibits in vitro adhesion to hydroxyapatite

Previous investigations showed that a high molecular mass, non-dialyzable material (NDM) from cranberries inhibits the adhesion of a number of bacterial species and prevents the co-aggregation of many oral bacterial pairs. In the present study we determined the effect of mouthwash supplemented with NDM on oral hygiene. Following 6 weeks of daily usage of cranberry-containing mouthwash by an experimental group (n = 29), we found that salivary mutans streptococci count as well as the total bacterial count were reduced significantly (ANOVA, P < 0.01) compared with those of the control (n = 30) using placebo mouthwash. No change in the plaque and gingival indices was observed. In vitro, the cranberry constituent inhibited the adhesion of Streptococcus sobrinus to saliva-coated hydroxyapatite. The data suggest that the ability to reduce mutans streptococci counts in vivo is due to the anti-adhesion activity of the cranberry constituent.

Regulation of fructosyltransferase activity by carbohydrates, in solution and immobilized on hydroxyapatite surfaces

We tested the effect of several carbohydrates on the activity of cell-free fructosyltransferases (FTF) in solution and immobilized onto hydroxyapatite (HA) and found an inhibitory dose-dependent effect of glucose on FTF activity, both on the surface and in solution. Glucose at 160 mM inhibits FTF activity by 75% both on HA and in solution. Fructose at 160 mM inhibited FTF activity by 25% in solution and by 15% on HA. Levan inhibited FTF activity by 30% in solution, while dextrans and inulin had a limited effect on FTF activity. Circular dichroism and infrared analysis demonstrated no major changes in the chemical structure of fructans synthesized by cell-free FTF on HA and in solution, in the presence or absence of glucose. However, as verified by size-exclusion chromatography, glucose inhibited the synthesis of high molecular-weight fructans. The results indicate that glucose, a byproduct of the FTF enzymatic reaction, is the main carbohydrate affecting FTF activity. Selective inhibition of high molecular-weight fructan production by glucose, may indicate that two mechanisms are involved in the synthesis of fructans, both in solution and on the surface.

Early formation of Streptococcus sobrinus biofilm on various dental restorative materials

OBJECTIVES

To examine the formation of dental biofilm by Streptococcus sobrinus on different types of restorative materials, using a model consisting of host and bacterial constituents.

METHODS

The adsorption pattern of saliva to the restorative material was determined by means of gel electrophoresis coupled with computerized densitometry techniques. The amount of salivary proteins adsorbed onto the surfaces was measured using the Bradford method. Sucrose-dependent bacterial adhesion to the saliva-coated restorative material was tested by radioactive-labelled Streptococcus sobrinus, and viable counts of these bacteria in the biofilm was determined using bacterial culture techniques.

RESULTS

Different adsorption patterns by salivary proteins to restorative materials were recorded. Durafil and acrylic dental materials demonstrated the most affinity to salivary proteins. A surface dependent adhesion profile was recorded, showing a high affinity of albumin and amylase to Acrylic and Durafil materials. Bacterial accumulation was the highest with Fuji LC and Fuji GC, which also demonstrated the highest bacterial viability.

CONCLUSIONS

Our study demonstrates the specificity of biofilm formation on different brands of dental restorative materials. Formation of a variety of dental biofilms has a significant impact on the progression of dental diseases in the oral cavity.

Antibacterial effect of parabens against planktonic and biofilm Streptococcus sobrinus

Tooth decay is an infectious disease caused by bacteria immobilized on the tooth surfaces. Eradication of these bacteria, for example Streptococcus sobrinus (S. sobrinus), from the oral cavity is essential in the prevention and treatment of tooth decay. We have tested the antimicrobial effect of several paraben derivatives such as methyl (MP), ethyl (EP), propyl (PP) and butyl (BP) against immobilized and planktonic S. sobrinus. The antibacterial effect was as follows: MP>EP>PP=BP on immobilized bacteria and MP>EP=PP>BP on planktonic bacteria. An antibacterial synergistic effect was found between several combinations of parabens on immobilized and planktonic S. sobrinus. Our results indicate that parabens are potential antibacterial agents against immobilized or planktonic bacteria found in the oral cavity.

The role of fructans on dental biofilm formation by Streptococcus sobrinus, Streptococcus mutans, Streptococcus gordonii and Actinomyces viscosus

Dental plaque biofilm plays a pivotal role in the progression of dental diseases. Polysaccharides are of great importance in the ecology of the dental biofilm. We studied the effect of fructans, glucans and a mixture of both fructans and glucans, synthesized in situ by immobilized fructosyltransferase or glucosyltransferase, on the adhesion of Streptococcus sobrinus, Streptococcus mutans, Streptococcus gordonii and Actinomyces viscosus to hydroxyapatite beads coated with human saliva (sHA). The adhesion of A. viscosus to sHA was found to be fructan-dependent. Adhesion of both S. sobrinus and S. mutans was found to be mediated mainly by glucans, while the adhesion of S. gordonii was found to be both glucan- and fructan-dependent. Treatment with fructanase prior to A. viscosus adhesion resulted in a significant reduction in adhesion to sHA, while adhesion of S. sobrinus, S. mutans and S. gordonii was slightly influenced by fructanase treatment. Treatment with fructanase after adhesion of S. gordonii to sHA resulted in a significant reduction in their adhesion to sHA. Our results show that fructans may play a role in the adhesion and colonization of several cariogenic bacteria to sHA, thus contributing to the formation of dental plaque biofilm.

The interactions of human neutrophils with the constituents of an experimental dental biofilm

Despite the antibacterial properties of neutrophils, their ability to prevent colonization of the dental biofilm by pathogenic bacteria is limited. The present study examined the ability of human neutrophils to attach to an experimental dental biofilm and tested their antibacterial functions following adhesion. Neutrophil adhesion was greatest to hydroxyapatite (HA) in the absence of biofilm. Among the biofilms, glucosyltransferase or fructosyltransferase adsorbed onto saliva-coated HA showed the highest adhesion of cells. The adhesion of neutrophils was directly related to their initial concentration in the solution and to the duration of incubation. Plasma was found to reduce neutrophil attachment significantly, while stimulation of the cells had no effect. Stimulation of attached neutrophils induced superoxide secretion with levels significantly lower than that secreted by suspended cells. The presence of neutrophils on the biofilm reduced the number and the viability of Streptococcus mutans attached to the beads. The present findings suggest that neutrophils are able to attach to dental biofilms and that the attached neutrophils retained their antibacterial activity.

The effect of extracellular polysaccharides from Streptococcus mutans on the bactericidal activity of human neutrophils

Extracellular polysaccharides (PS) synthesized by oral bacteria constitute one of their major virulence factors. The PS, synthesized from sucrose, facilitate adhesion and colonization by bacteria to tooth surfaces. The study was designed to test the effect of in situ production of extracellular PS by Streptococcus mutans on the bactericidal activity of human neutrophils. These effects were tested on bacteria pre-exposed to sucrose (PS-positive Strep. mutans) and compared to bacteria not exposed to sucrose (PS-negative Strep. mutans). The interactions between neutrophils and Strep. mutans were tested in suspension and on bacteria in an experimental model of dental plaque. Viability of Strep. mutans was measured by [3H]-thymidine incorporation into the bacteria. Degranulation of neutrophils was evaluated by the release of lysozyme, and the production of reactive oxygen products was measured by chemiluminescence. When neutrophils were incubated with suspended bacteria, the viability of PS-negative Strep. mutans was 20% of that of bacteria not incubated with neutrophils (control), while the viability of PS-positive Strep. mutans was 40% of the control. In the experimental dental-plaque model, 50% of the PS-negative Strep. mutans were killed by neutrophils while the viability of PS-positive Strep. mutans was not different than of the control. Degranulation of neutrophils was not affected by the presence of extracellular PS of Strep. mutans. Artificial stimulation of neutrophils with phorbol myristate acetate also did not enhance the bactericidal effect of neutrophils on PS-positive Strep. mutans. However, PS-positive Strep. mutans elicited oxygen-reactive products from neutrophils, 2-fold less than with PS-negative Strep. mutans. The results indicate that in situ production of bacterial extracellular polysaccharides might be a major virulence factor of Strep. mutans, enabling PS-positive Strep. mutans in the dental-plaque biofilm to evade killing by human neutrophils.

Action of agents on glucosyltransferases from Streptococcus mutans in solution and adsorbed to experimental pellicle

Glucosyltransferase (Gtf) activity mediates sucrose-dependent adherence of mutans streptococci to the tooth surface, is essential for the cariogenicity of these micro-organisms, and contributes significantly to the exopolysaccharide component of the dental-plaque matrix. Clearly, agents that inhibit Gtfs could have therapeutic benefit. Here the effects of agents that inhibit Gtfs in solution and adsorbed to a surface were explored. Various classes of chemical reagents were tested for their ability to inhibit the enzymes responsible for insoluble-glucan synthesis (GtfB), insoluble/soluble glucan synthesis (GtfC), and soluble-glucan (GtfD) from Streptococcus mutans. Standard inhibition assays were done with Gtf enzyme in solution or with Gtf adsorbed to parotid saliva-coated hydroxylapatite (surface phase). Reagents tested included the metallic cations Li+, Zn2+, Cu2+, Fe2+ and Fe3+; the oxidizing compounds hypochlorite, Rose Bengal, perborate, and sodium-meta-periodate; and a panel of sugars and sugar analogues including sorbitol, xylitol, 1',4',6' trideoxy-trichloro-galactosucrose (TGS), and 1-deoxynojirimycin (dNJ). In solution, Gtf activity was inhibited significantly, at the highest concentrations tested: by the metal ions Zn2+, Cu2+, Fe2+ and Fe3+ (approx. 40-80% inhibition); by Rose Bengal and hypochlorite (approx. 80-90% inhibition); and by TGS and dNJ (approx. 50-80%). However, surface-adsorbed Gtfs displayed increased resistance to inhibition by the same metal cations and oxidizing compounds that inhibited them in solution. In contrast, both TGS and dNJ possessed similar inhibition profiles for both surface-bound Gtf and enzyme in solution. These data indicate that the nature of the inhibitor is important, and also whether the Gtf enzyme is in solution or adsorbed to saliva-coated hydroxylapatite.

Effect of salivary biofilm on the adherence of oral bacteria to bleached and non-bleached restorative material

OBJECTIVE

The objective of this work was to examine the effect of in vitro salivary biofilm on the adherence of oral bacteria to bleached and non-bleached restorative material (Charisma).

METHODS

Charisma samples, prepared in silicon models, were treated with either 10% carbamide peroxide (CP) or 10% hydrogen peroxide (HP). After incubation with the bleaching agent for a period of one, two or three days, the samples were coated with freshly collected human saliva. The adsorption pattern of the saliva to the restorative material was determined using gel electrophoresis coupled with computerized densitometry techniques. The amount of salivary proteins adsorbed onto the treated surfaces was measured using the Bradford method. Sucrose-dependent bacterial adhesion to the salivary-coated Charisma was tested using radio-labeled Streptococcus mutans, Streptococcus sobrinus and Actinomyces viscosus. Adhesion of each bacterium to surfaces pretreated with the bleaching agents was compared with saliva coated bleached surfaces.

RESULTS

The profile of salivary proteins adsorption followed a similar pattern in Charisma samples pretreated with either CP or HP or untreated samples. However, the total amount of salivary proteins adsorbed onto the samples decreased after bleaching with CP or HP. Salivary biofilm, coating the surface of the restorative material, significantly decreased sucrose-dependent adhesion of Streptococcus sobrinus and Streptococcus mutans to the bleached and non-bleached surfaces, compared to non-coated specimens (p < 0.05). Saliva had a minor effect on adhesion of Actinomyces viscosus.

SIGNIFICANCE

Our study demonstrates the importance of salivary biofilm in controlling adhesion of oral bacteria to restorative material pretreated with bleaching agents or untreated.

Bacterial adherence to bleached surfaces of composite resin in vitro

OBJECTIVE

The effect of bleaching agents on bacterial adherence to polished surfaces of composite resin restorations was assessed in vitro.

STUDY DESIGN

Samples of light-curing composite resins were treated with either 10% carbamide peroxide or 10% hydrogen peroxide for 1, 3, or 7 days. Bacterial adherence of Streptococcus mutans, Streptococcus sobrinus, and Actinomyces viscosus to the treated resin samples was analyzed and compared with adherence to nonbleached controls.

RESULTS

A 10% solution of carbamide peroxide caused a significant increase in surface adherence of Streptococcus mutans and Streptococcus sobrinus after 3 days (P < .01). A 10% solution of hydrogen peroxide caused a significant increase in surface adherence of Streptococcus mutans and Streptococcus sobrinus after 3 and 7 days (P < .01). A decrease in adherence of Actinomyces viscosus was found after treatment with 10% hydrogen peroxide for 7 days (P < .05).

CONCLUSIONS

It appears that bleaching agents may affect adherence of certain cariogenic microorganisms to the outer surfaces of composite resin restorations.

Detachment of linking film bacteria from enamel surfaces by oral rinses and penetration of sodium lauryl sulphate through an artificial oral biofilm

The biofilm mode of growth protects plaque micro-organisms against environmental attacks, such as from antimicrobials or detergents. Dental plaque is linked to enamel through the adhesion of initial colonizers. Once this link is disrupted, the entire plaque mass adhering to it detaches. Experiments in a parallel-plate flow chamber demonstrated that bacteria adhering to saliva-coated enamel could not be stimulated to detach by perfusion of the flow chamber with two traditional mouthrinses (Corsodyl and Scope), whereas perfusion with a prebrushing rinse (Plax) or its detergent components stimulated detachment from saliva-coated enamel of a wide variety of bacterial strains. Following perfusion of the flow chamber with the mouthrinses, little additional detachment of adhering bacteria by the passage of a liquid-air interface occurred. After perfusion with the prebrushing rinse, however, significant numbers of still-adhering bacteria could be stimulated to detach by passage of a liquid-air interface, indicating that Plax had weakened their adhesive bond. The ability of Plax or its detergent components to detach plaque bacteria is not always obvious from in vivo experiments, and reports on its clinical efficacy are inconsistent. Likely, antimicrobials or detergents are unable to penetrate the plaque and reach the linking film bacteria, as demonstrated here by Fourier transform infrared spectroscopy.

Antibacterial effect of chlorhexidine on bacteria adsorbed onto experimental dental plaque

The most common method used to examine the antibacterial effect of antiplaque agents is the minimal inhibitory concentration (MIC) method, which is tested on bacteria in suspensions. Examining the antibacterial effect on bacteria adsorbed onto dental surfaces models is not as popular, although it is clear that such models reflect the conditions in the oral cavity far more accurately than the conventional MIC method. The antibacterial effect of chlorhexidine (CHX) on bacteria adsorbed onto experimental dental plaque model was investigated. Hydroxyapatite beads were coated with human saliva. Next, cell-free fructosyltransferase (FTF) and glucosyltransferase (GTF) were adsorbed onto the beads, and sucrose was added to allow the synthesis of polysaccharide by the surface-bound enzymes. Following adsorption of Streptococcus sobrinus to the experimental dental plaque (EDP), the EDP was exposed to CHX at concentrations between 0.008 to 0.0002% at pH values of 5.5, 6.5, and 7.5. After 150 min incubation, growth of the adsorbed bacteria was measured by their incorporation of 3H-uridine or 3H-thymidine. Comparison of bacterial growth on the EDP with that in suspension showed that the surface-bound bacteria were less sensitive to CHX than were the bacteria in suspension. At all tested CHX concentrations, the antibacterial effect was independent of pH. In addition, under our experimental conditions, the use of 3H-uridine as an indicator of bacterial viability proved to be more sensitive than 3H-thymidine. The antibacterial effect of an agent in a model closely mimicking the tooth surface should generate results that are more relevant to the in vivo conditions than are conventional methods, thus bearing significant information concerning clinical applications of CHX.

Kinetic properties of glucosyltransferase adsorbed onto saliva-coated hydroxyapatite

Results from previous studies have shown that several properties of glucosyltransferase (GTF) adsorbed onto saliva-coated hydroxyapatite beads differ from those of GTF in solution. For example: thermostability, pH-activity dependency, sensitivity to inhibitors. The aim of this study was to compare the kinetics of the adsorbed GTF with its kinetic properties in solution. Hydroxyapatite beads were coated with human parotid saliva (sHA). Following washes, cell-free GTF enzyme from Streptococcus sobrinus 6715 (S. sobrinus 6715) or Streptococcus mutans GS-5 (S. mutans GS-5) was adsorbed onto sHA. The GTF-coated sHA were then incubated with radiolabeled sucrose for intervals of 5-360 minutes and the amount of glucans synthesized in situ by the adsorbed GTF was determined and compared with that produced in solution. The adsorbed GTF (from S. sobrinus 6715) exhibited a sharp increase in glucan production within the first 5 minutes of incubation while surface-bound GTF of S. mutans GS-5 displayed an initial burst of activity within the first 15 minutes of incubation. During the next 6 hours (duration of experiment) the amount of glucan on the beads did not increase with either enzyme. In contrast, the kinetic profile of the two GTFs in solution demonstrated a linear increase in the amount of glucans formed, with no initial burst effect. The results indicate that the rapid formation of glucans by GTF adsorbed onto sHA could have implications for colonization by oral microorganisms on tooth surfaces. The accelerated synthesis of glucan on tooth surfaces may affect the microbiology of the dental plaque, and might also influence the movement of substances, such as acids and antiplaque agents, across the acquired pellicle and dental plaque.

Interactions of streptococcal glucosyltransferases with alpha-amylase and starch on the surface of saliva-coated hydroxyapatite

The salivary pellicle consists of various proteins and glycoproteins which may interact with one another. Experiments were performed to elucidate the interactions of streptococcal glucosyltransferase (Gtf) enzymes with human salivary alpha-amylase in solution and on the surface of saliva-coated hydroxyapatite (SHA) beads. The Gtf enzymes -B, -C and -D, when immobilized on to SHA beads, reduced the activity of adsorbed amylase; GtfD showed the highest inhibition of salivary amylase activity. The presence of glucan produced by immobilized GtfD did not further reduce amylase activity. The amount of amylase adsorbed on to hydroxyapatite beads was reduced when salivary amylase was added simultaneously with any of the Gtf enzymes, suggesting that amylase and Gtfs may compete with each other for binding sites on hydroxyapatite. Starch hydrolysates produced by SHA-surface-bound salivary amylase were tested for their effect on glucan production from sucrose by Gtf enzymes in solution and on SHA beads; glucan production by SHA-immobilized GtfB was stimulated in the presence of starch hydrolysates. Glucan synthesized by SHA-immobilized GtfB in the presence of starch hydrolysates was less susceptible to hydrolysis by the fungal enzyme mutanase than was glucan made by SHA-immobilized GtfB in the absence of starch hydrolysates. Glucan production by GtfB associated with streptococci immobilized on to SHA was also enhanced in the presence of starch hydrolysates. The adhesion of oral micro-organisms to SHA coated with glucan made in the presence and absence of starch hydrolysates was investigated, and some bacteria displayed higher adhesion activities for the glucan made in the presence of the hydrolysates. Therefore, the interaction of amylase and Gtf enzymes on a SHA surface may modulate the formation of glucan and the adherence of oral micro-organisms.

Adsorption of human salivary proteins to titanium powder. I. Adsorption of human salivary albumin

Titanium (Ti) is among the most widely used implant materials in dentistry today. The success of Ti implants is associated with their interactions with the surrounding tissues and biological fluids. In the present study, the adsorption of salivary proteins to Ti and the effect of calcium (Ca) on this process were investigated. Untreated and Ca-treated Ti powders were suspended in human clarified whole saliva. After incubation, the supernatant fluid was collected for protein analysis. The powders were then washed and resuspended in EDTA to desorb proteins from Ti surfaces. Sodium dodecylsulphate polyacrylamide gel electrophoresis and Bradford protein assay were conducted to determine the concentration and type of proteins that adsorbed onto Ti surfaces. The presence of Ca ions enhanced the adsorption of salivary proteins to Ti. A 66 kDa protein, identified by immunoblotting as albumin, was found as the main adsorbed salivary protein. Adsorption of albumin to Ti pretreated with Ca was significantly greater than to native Ti. The Ca-dependent adsorption process was reversed by EDTA. The data suggest that salivary albumin is one of the main constituents of a salivary biofilm formed on Ti dental implants and its adsorption to Ti surfaces is Ca-dependent. The presence of albumin on Ti dental implants may affect plaque accumulation on the implants and the biocompatibility of Ti implants.

Mechanisms of dental plaque formation

Much effort has been placed on elucidating the diverse mechanisms of microbial adhesion to tooth surfaces. Both specific and non-specific types of adhesion have been envisaged. Pioneer colonizers represent a selected part of the oral microflora, and it has been assumed that specific adhesin-receptor interactions between the microbial surface and the pellicle account for this specificity. Whereas microbial adhesion to tooth surfaces is a general prerequisite for initiation of plaque formation, microbial multiplication is probably the dominant feature in the build-up of dental plaque. Local environmental factors which influence the establishment and composition of the ultimate plaque community are therefore of greater importance than initial adhesion per se. The highly individual and site-related characteristics of the plaque flora illustrate the selective power of the environment. Environmental conditions are not uniform. Thus, each site represents its own conditions are not uniform. Thus, each site represents its own distinct ecosystem, and the microbial composition at the site depends on the outcome of a variety of host-microbial and microbial-microbial interactions. The relative in vivo significance of these interactions is difficult to assess.

Characteristics of accumulation of oral gram-positive bacteria on mucin-conditioned glass surfaces in a model system

Strains of Streptococcus, Actinomyces and Lactobacillus were grown on glass surfaces in semi-defined medium (pH 7.0) with mucin, at a dilution rate of D = 0.1 h-1, in a modified chemostat. The accumulation of cells followed four phases. In phase 1 (0-1 h), cells did not divide on the surfaces and adhesion accounted for rapid accumulation. Phase 2 (1-4 h) comprised adhesion and cell division, and accumulation slowed, cell number doubling times (Cdt) Streptococcus, 2.7 h to 8.6 h, Actinomyces, 2.3 h to 7.5 h and Lactobacillus, 3.6 h to 3.8 h. Cell division on surfaces accounted for accumulation in phase 3 (4 h to 12 h): Cdt Streptococcus, 1.7 h to 5.2 h, Actinomyces, 2.4 h to 7.5 h and Lactobacillus, 2.2 h to 7.2 h. The biofilm stabilized in Phase 4, Cdt 18.5 h to 90.2 h. The numbers (10(6) colony-forming units per cm2) of cells in stable biofilms were Streptococcus, 4.02 to 5.12, Actinomyces, 12.5 and 34.0 and Lactobacillus, 2.77. Accumulation increased (Cdt 0.9 h-2.7 h) when cells were exposed to glucose excess or high dilution rates and phase 2 of accumulation did not occur.