Microbiological studies on early dento-gingival plaque on teeth and Mylar strips in humans

Bacterial adhesion and surface properties of computer-aided design-computer-aided manufacturing restorative materials

PURPOSE

This study aimed to evaluate the surface properties and bacterial adhesion of computer-aided design-computer-aided manufacturing (CAD-CAM) restorative materials.

METHODS

Four CAD-CAM resin-based blocks (Vita Enamic, Shofu block HC, Cerasmart [CS] and Lava Ultimate [LU]) and a leucite-reinforced glass ceramic block (IPS Empress CAD) were used in the present study. Specimens prepared with dimensions of 10 × 10 × 1 mm were polished. Surface characteristics were assessed with hydrophobicity and surface free energy (SFE) analysis. Surface roughness was measured using a profilometer, and elemental and topographic evaluations were performed with SEM-EDX analysis. After being kept in artificial saliva for 1 h, Streptococcus mutans (S. mutans) and Streptococcus mitis (S. mitis) were incubated separately in 5% CO2 atmosphere at 37°C for 24 h. The adhered bacteria were counted as ×108 CFU/mL.

RESULTS

Surface roughness, contact angle and SFE measurement values were found to be in the range of 0.144-0.264 Ra, 28.362°-70.074° and 39.65-63.62 mN/m, respectively. The highest adhered amount of S. mutans was found in CS and the lowest in LU, while there was no significant difference between the amounts of adhered S. mitis.

CONCLUSION

Despite differences in the surface properties of the materials used for the study, the materials exhibited identical properties with respect to bacterial adhesion.

Microbial Diversity in the Early In Vivo-Formed Dental Biofilm

Although the mature dental biofilm composition is well studied, there is very little information on the earliest phase of in vivo tooth colonization. Progress in dental biofilm collection methodologies and techniques of large-scale microbial identification have made new studies in this field of oral biology feasible. The aim of this study was to characterize the temporal changes and diversity of the cultivable and noncultivable microbes in the early dental biofilm. Samples of early dental biofilm were collected from 11 healthy subjects at 0, 2, 4, and 6 h after removal of plaque and pellicle from tooth surfaces. With the semiquantitative Human Oral Microbiome Identification Microarray (HOMIM) technique, which is based on 16S rRNA sequence hybridizations, plaque samples were analyzed with the currently available 407 HOMIM microbial probes. This led to the identification of at least 92 species, with streptococci being the most abundant bacteria across all time points in all subjects. High-frequency detection was also made with Haemophilus parainfluenzae, Gemella haemolysans, Slackia exigua, and Rothia species. Abundance changes over time were noted for Streptococcus anginosus and Streptococcus intermedius (P = 0.02), Streptococcus mitis bv. 2 (P = 0.0002), Streptococcus oralis (P = 0.0002), Streptococcus cluster I (P = 0.003), G. haemolysans (P = 0.0005), and Stenotrophomonas maltophilia (P = 0.02). Among the currently uncultivable microbiota, eight phylotypes were detected in the early stages of biofilm formation, one belonging to the candidate bacterial division TM7, which has attracted attention due to its potential association with periodontal disease.

In vivo study of the initial bacterial adhesion on different implant materials

OBJECTIVE

Biofilm formation on implant materials plays a major role in the aetiology of periimplantitis. The aim of this study was to examine in vivo the initial bacterial adhesion on six different implant materials.

METHODS

The implant materials Ti-m, TiUnite®, ZiUnite®, ATZ-m, ATZ-s, TZP-A-m were tested using bovine enamel slabs as controls. All materials, fixed on splint systems, were examined after 30 min and 120 min of oral exposure. DAPI staining was used for quantitative analysis of the initially adherent microorganisms. Initial adherent microorganisms were visualised by fluorescence In situ-hybridisation (FISH) and quantified by confocal laser scanning microscopy (CLSM). The targets of the oligonucleotide probes were Eubacteria, Veillonella spp., Fusobacterium nucleatum, Actinomyces naeslundii and Streptococcus spp.

RESULTS

DAPI analysis showed that increasing the time of oral exposure resulted in an increasing amount of initial adherent bacteria. The highest level of colonisation was on ZiUnite®, with the lowest occurring on the bovine enamel, followed by Ti-m. This early colonisation correlated significantly with the surface roughnesses of the materials. FISH and CLSM showed no significant differences relating to total bacterial composition. However, Streptococcus spp. was shown to be the main colonisers on each of the investigated materials.

CONCLUSION

it could be shown that within an oral exposure time of 30 min and 120 min, despite the salivary acquired pellicle initial biofilm formation is mainly influenced directly or indirect by the material surface topography. Highly polished surfaces should minimise the risk of biofilm formation, plaque accumulation and possibly periimplantitis.

pH landscapes in a novel five-species model of early dental biofilm

BACKGROUND

Despite continued preventive efforts, dental caries remains the most common disease of man. Organic acids produced by microorganisms in dental plaque play a crucial role for the development of carious lesions. During early stages of the pathogenetic process, repeated pH drops induce changes in microbial composition and favour the establishment of an increasingly acidogenic and aciduric microflora. The complex structure of dental biofilms, allowing for a multitude of different ecological environments in close proximity, remains largely unexplored. In this study, we designed a laboratory biofilm model that mimics the bacterial community present during early acidogenic stages of the caries process. We then performed a time-resolved microscopic analysis of the extracellular pH landscape at the interface between bacterial biofilm and underlying substrate.

METHODOLOGY/PRINCIPAL FINDINGS

Strains of Streptococcus oralis, Streptococcus sanguinis, Streptococcus mitis, Streptococcus downei and Actinomyces naeslundii were employed in the model. Biofilms were grown in flow channels that allowed for direct microscopic analysis of the biofilms in situ. The architecture and composition of the biofilms were analysed using fluorescence in situ hybridization and confocal laser scanning microscopy. Both biofilm structure and composition were highly reproducible and showed similarity to in-vivo-grown dental plaque. We employed the pH-sensitive ratiometric probe C-SNARF-4 to perform real-time microscopic analyses of the biofilm pH in response to salivary solutions containing glucose. Anaerobic glycolysis in the model biofilms created a mildly acidic environment. Decrease in pH in different areas of the biofilms varied, and distinct extracellular pH-microenvironments were conserved over several hours.

CONCLUSIONS/SIGNIFICANCE

The designed biofilm model represents a promising tool to determine the effect of potential therapeutic agents on biofilm growth, composition and extracellular pH. Ratiometric pH analysis using C-SNARF-4 gives detailed insight into the pH landscape of living biofilms and contributes to our general understanding of metabolic processes in in-vivo-grown bacterial biofilms.

Polyethyleneimine nanoparticles incorporated into resin composite cause cell death and trigger biofilm stress in vivo

Incorporation of cross-linked quaternary ammonium polyethylenimine (QPEI) nanoparticles in dental resin composite has a long-lasting and wide antimicrobial effect with no measured impact on biocompatibility in vitro. We hypothesized that QPEI nanoparticles incorporated into a resin composite have a potent antibacterial effect in vivo and that this stress condition triggers a suicide module in the bacterial biofilm. Ten volunteers wore a removable acrylic appliance, in which two control resin composite specimens and two resin composite specimens incorporating 1% wt/wt QPEI nanoparticles were inserted to allow the buildup of intraoral biofilms. After 4 h, the specimens were removed and tested for bacterial vitality and biofilm thickness, using confocal laser scanning microscopy. The vitality rate in specimens incorporating QPEI was reduced by > 50% (p < 0.00001), whereas biofilm thickness was increased (p < 0.05). The ability of the biofilm supernatant to restore bacterial death was tested in vitro. The in vitro tests showed a 70% decrease in viable bacteria (p < 0.05). Biofilm morphological differences were also observed in the scanning electron microscope micrographs of the resin composite versus the resin composite incorporating QPEI. These results strongly suggest that QPEI nanoparticles incorporated at a low concentration in resin composite exert a significant in vivo antibiofilm activity and exhibit a potent broad spectrum antibacterial activity against salivary bacteria.

Oral immunization with Porphyromonas gingivalis outer membrane protein and CpGoligodeoxynucleotides elicits T helper 1 and 2 cytokines for enhanced protective immunity

The aim of this study was to evaluate the efficacy of an oral vaccine containing the 40-kDa outer membrane protein of Porphyromonas gingivalis (40K OMP) and synthetic oligodeoxynucleotides containing unmethylated CpG dinucleotides (CpG ODN) to control oral infection by P. gingivalis. [run on]40K-OMP40K-OMP40K-OMPOral immunization with 40K-OMP plus CpG ODN induced significant 40K-OMP-specific serum IgG, IgA and saliva IgA antibody responses. The 40K-OMP-specific CD4(+) T cells induced by oral 40K-OMP plus CpG ODN produced both Th1 (IFN-gamma) and Th2 (IL-4) cytokines. Furthermore, increased frequencies of CD11c(+)B220(+) DCs and CD11c(+)CD11b(+) DCs with up-regulated expression of CD80, CD86, CD40 and MHC II molecules were noted in spleen, Peyer's patches and cervical lymph nodes. Immunized mice were then infected orally with P. gingivalis to determine whether the immune responses induced by oral 40K-OMP plus CpG ODN were capable of suppressing bone resorption caused by P. gingivalis infection. Mice given 40K-OMP plus CpG ODN showed significantly reduced bone loss associated with oral infection by P. gingivalis.Thus, oral administration of 40K-OMP together with CpG ODN induces Th1- and Th2-type cells, which provide help for protective immunity against P. gingivalis infection. This may be an important tool for prevention of chronic periodontitis.

The Bass technique using a specially designed toothbrush

BACKGROUND

Reducing the plaque index (PI) is still the main objective in the prevention of gingivitis and periodontitis.

AIM

This experiment evaluated the efficiency of a new manual toothbrush shape from two perspectives: allowing the maximum exploitation of the bristle surface in all directions of the dental arches and simplifying the Bass technique handling and movements in domestic oral care.

PATIENTS AND METHOD

The distinct shape was obtained by distancing the bristle surface from the surface of the toothbrush handle in the direction of the bristles, maintaining the two surfaces on parallel planes. This modification facilitates brushing with the Bass technique, since rotation of the new toothbrush handle on its axis allows the bristle surface to cover a greater area. Sixteen patients between the ages of 23 and 49 years with at least 28 dental elements were divided randomly into two groups. On the first day, they underwent professional plaque removal and were provided with pairs of toothbrushes to test. They were evaluated 30 days later using the Full Mouth Plaque Score determined by two dental hygienists who were unaware of the instructions given concerning the method, quadrants and toothbrushes used for the experiment.

RESULTS

The results showed that the modifications to the manual toothbrushes produced greater PI control compared with the traditionally shaped toothbrushes.

CONCLUSION

Although oral hygiene testing at home usually provides subjective information, in this experiment, the data provided a positive, objective result.

Nasal vaccination with the 40-kilodalton outer membrane protein of Porphyromonas gingivalis and a nontoxic chimeric enterotoxin adjuvant induces long-term protective immunity with reduced levels of immunoglobulin E antibodies

In this study, we demonstrated that the 40-kDa outer membrane protein of Porphyromonas gingivalis (40-kDa OMP) nasally administered with a nontoxic chimeric adjuvant that combines the A subunit of mutant cholera toxin E112K with the pentameric B subunit of heat-labile enterotoxin from enterotoxigenic Escherichia coli (mCTA/LTB) elicited a long-term protective immune response. Immunization with the 40-kDa OMP and mCTA/LTB induced high levels of 40-kDa-OMP-specific immunoglobulin G (IgG) and IgA antibodies (Abs) in sera and elicited a significant IgA anti-40-kDa OMP Ab response in saliva. These Ab responses were maintained for at least 1 year after the immunization. Although using adjuvant mCTA/LTB gave Ab responses in the saliva comparable to those obtained using native cholera toxin (nCT) as the adjuvant, the levels of total IgE and 40-kDa-OMP-specific IgE Abs as well as interleukin-4 levels induced by the immunization with mCTA/LTB were lower than those induced by the immunization with nCT. Importantly, IgG Abs generated by nasal immunization with the 40-kDa OMP plus mCTA/LTB inhibited the coaggregation and hemagglutinin activities of P. gingivalis. Furthermore, the mice given nasal 40-kDa OMP plus mCTA/LTB showed a significant reduction of alveolar bone loss caused by oral infection with P. gingivalis even 1 year after the immunization compared to the loss in unimmunized mice. Because mCTA/LTB is nontoxic, nasally administered 40-kDa OMP together with mCTA/LTB should be an effective and safe mucosal vaccine against P. gingivalis infection in humans and may be an important tool for the prevention of chronic periodontitis.

Egg yolk-derived immunoglobulin (IgY) against Porphyromonas gingivalis 40-kDa outer membrane protein inhibits coaggregation activity

The anaerobic bacterium Porphyromonas gingivalis, a major pathogen in periodontitis, aggregates with a number of oral bacteria to form dental plaque, which is important for its colonization. We previously cloned the gene coding the 40-kDa outer membrane protein (OMP) of P. gingivalis 381 and produced large amounts of the recombinant (r) protein. Affinity-purified rabbit antiserum against r40-kDa OMP effectively inhibited the coaggregation activity of P. gingivalis to oral bacteria, thus 40-kDa OMP was thought to be an important coaggregation factor of P. gingivalis. Further, since it is conserved among many P. gingivalis strains, this coaggregation factor may be an effective target for passive immunotherapy against P. gingivalis infection. Recently, passive immunization approaches using a specific antibody produced from hen egg yolk (IgY) have been developed for oral infectious diseases, and shown to be convenient and economic. In the present study, we immunized hens intramuscularly with r40-kDa OMP and obtained highly purified IgY from the egg yolks. The purified IgY specifically recognized r40-kDa OMP and also reacted with a functional coaggregation-associated domain peptide of 40-kDa OMP. Our results demonstrated that a ratio of purified IgY as low as 2.5 microg/150 microl significantly inhibited the coaggregation of P. gingivalis with Streptococcus gordonii, which was verified by a visual coaggregation assay and radioactivity-based quantitative micro-coaggregation assay. We concluded anti-r40-kDa OMP IgY may be useful for passive immunization against periodontal diseases caused by P. gingivalis infection.

Early plaque formation on fibre-reinforced composites in vivo

In the present study, two different fibre-reinforced composites (FRCs) (glass and polyethylene FRC), dental ceramic and restorative composite were compared with respect to early plaque formation in vivo. Disc-shaped specimens were randomly distributed among the upper first and second molars of 14 healthy adult volunteers. Plaque samples were collected 24 h after the attachment of the specimens. Mutans streptococci (MS), non-mutans streptococci and total facultative bacteria were cultured. The plaque recovered from polyethylene FRC harboured significantly more MS than the plaque of ceramic, restorative composite and glass FRC. For the counts of non-mutans streptococci and total facultative bacteria, polyethylene FRC showed the highest counts, and ceramic showed a trend towards lower counts. The amount of plaque accumulation showed an association to the earlier reported surface roughness values of the studied materials. It was concluded that in the oral environment, polyethylene FRC promotes plaque accumulation and adhesion of MS more than glass FRC, restorative composite and dental ceramic. Glass FRC resembles restorative composite with respect to plaque accumulation and the adherence of MS.

Transcutaneous immunization with a 40-kDa outer membrane protein of Porphyromonas gingivalis induces specific antibodies which inhibit coaggregation by P. gingivalis

This study seeks to assess the potential of a 40-kDa outer membrane protein of Porphyromonas gingivalis (40k-OMP) as a transcutaneous vaccine against chronic periodontitis. Transcutaneous immunization (TCI) of mice with 40k-OMP alone elicited 40k-OMP-specific IgG antibody (Ab) responses in both serum and saliva. When administered with cholera toxin (CT) as adjuvant, TCI with 40k-OMP not only elevated IgG Abs as noted above, but also induced IgA responses in serum but not in saliva. Salivary IgG from mice given 40k-OMP alone or 40k-OMP plus CT showed higher binding levels to the 40k-OMP than did that of non-immunized mice. Ab-forming cell (AFC) analysis revealed high numbers of 40k-OMP-specific IgG AFCs in the spleen but low numbers in the salivary glands of mice given 40k-OMP alone or 40k-OMP plus CT. Since 40k-OMP-specific IgG inhibited the coaggregation of P. gingivalis vesicles and S. gordonii, TCI with 40k-OMP may be a useful tool in the quest to prevent P. gingivalis infection.

The influence of biosurfactants released by S. mitis BMS on the adhesion of pioneer strains and cariogenic bacteria

The influence of Streptococcus mitis BMS biosurfactants on the adhesion of eight pioneer and four cariogenic oral bacterial strains was, for a first screening, examined in a microtiter plate assay. The adhesion to pellicle-coated wells of three cariogenic strains was inhibited >70% by the biosurfactants, while only one pioneer strain showed >70% reduction. The reduction for the other strains did not exceed 50%. Subsequently, adhesion of Streptococcus mutans ATCC 25175 and Streptococcus sobrinus HG 1025, both cariogenic strains, and Actinomyces naeslundii T14V-J1 and Streptococcus oralis J22, two pioneer strains, to biosurfactants-coated enamel with and without a salivary pellicle was studied in a parallel plate flow chamber. A biosurfactants coating to enamel with or without a pellicle caused a reduction in the number of adhering cariogenic organisms, although no such reduction was observed for the pioneer strains. Consequently, it is concluded that S. mitis BMS biosurfactants may play a protective role against adhesion of cariogenic bacteria.

Prevalence of Helicobacter pylori detected by polymerase chain reaction in the oral cavity of periodontitis patients

Helicobacter pylori is an important gastrointestinal pathogen associated with gastritis, peptic ulcers, and an increased risk of gastric carcinoma. The oral cavity has been indicated as a possible H. pylori reservoir, and may therefore be involved in the reinfection of the stomach which sometimes follows treatment of H. pylori infection. The objective of the present study was to evaluate the prevalence of H. pylori as detected by polymerase chain reaction (PCR) in the oral cavity of periodontitis patients testing positive for this bacterium in the stomach. Thirty adult patients with alterations of the superior digestive tract, testing urease positive after endoscopy and biopsy, were selected. A full-mouth periodontal examination was performed in every patient and the subjects were allocated to two groups: gingivitis (15 patients) and chronic periodontitis (15 patients). Plaque and saliva samples collected from each patient were stored in 0.5 ml of TE buffer. DNA was extracted from the samples by the boiling method and was evaluated for the presence of H. pylori using the PCR method. JW 22/23 primers were used. The DNA of ATCC H. pylori 43629 (positive control) and water (negative control) were used for controlling the reactions. Of the 30 evaluated patients, 13 (43.3%) harbored H. pylori in the mouth. The bacterium was not found on the dorsum of the tongue of any patient, but was found in saliva in three patients (10%), in the supragingival plaque in six patients (20%), and in the subgingival plaque in eight patients (26.6%). The presence of H. pylori was similar in the gingivitis and chronic periodontitis groups. In conclusion, a high percentage of patients harbored H. pylori in their mouth. The bacterium was detected in saliva, supragingival and subgingival plaque, suggesting that these sites may be considered reservoirs for H. pylori in urease-positive patients.

Specific antibodies induced by nasally administered 40-kDa outer membrane protein of Porphyromonas gingivalis inhibits coaggregation activity of P. gingivalis

In this study, we have assessed the efficacy of the 40-kDa outer membrane protein (40k-OMP) of Porphyromonas gingivalis as a nasal vaccine for the prevention of adult periodontitis. Mice nasally immunized with 40k-OMP and cholera toxin as mucosal adjuvant displayed significant levels of 40k-OMP-specific serum IgG1, IgG2b and IgA as well as mucosal IgA antibodies (Abs) in saliva and nasal secretions. Ab-forming cell (AFC) analysis confirmed the antibody titers by detecting high numbers of 40k-OMP-specific AFCs in spleen, salivary glands and nasal passages. Because 40k-OMP-specific IgG inhibited coaggregation of P. gingivalis vesicles and S. gordonii, it may be an important tool for the prevention of adult periodontitis.

Molecular and genetic analyses of Actinomyces spp

Members of the genus Actinomyces are predominant primary colonizers of the oral cavity and play an important role in initiating plaque development. These bacteria have evolved unique mechanisms that favor colonization and persistence in this micro-environment. The expression of cell-surface fimbriae is correlated with the ability of these bacteria to adhere to specific receptors on the tooth and mucosal surfaces, and to interact with other plaque bacteria. The elaboration of sialidase is thought to enhance fimbriae-mediated adherence by unmasking the fimbrial receptors on mammalian cells. The presence of certain cell-associated or extracellular enzymes, including those involved in sucrose or urea metabolism, may provide the means for these bacteria to thrive under conditions when other growth nutrients are not available. Moreover, these enzyme activities may influence the distribution of other plaque bacteria and promote selection for Actinomyces spp. in certain ecological niches. The recent development of a genetic transfer system for Actinomyces spp. has allowed for studies the results of which demonstrate the existence of multiple genes involved in fimbriae synthesis and function, and facilitated the construction of allelic replacement mutants at each gene locus. Analyses of these mutants have revealed a direct correlation between the synthesis of assembled fimbriae and the observed adherence properties. Further genetic analysis of the various enzyme activities detected from strains of Actinomyces should allow for an assessment of the role of these components in microbial ecology, and their contribution to the overall success of Actinomyces spp. as a primary colonizer and a key player in oral health and disease.

Inhibition of Streptococcus mutans NS adhesion to glass with and without a salivary conditioning film by biosurfactant- releasing Streptococcus mitis strains

The release of biosurfactants by adhering microorganisms as a defense mechanism against other colonizing strains on the same substratum surface has been described previously for probiotic bacteria in the urogenital tract, the intestines, and the oropharynx but not for microorganisms in the oral cavity. Two Streptococcus mitis strains (BA and BMS) released maximal amounts of biosurfactants when they were grown in the presence of sucrose and were harvested in the early stationary phase. The S. mitis biosurfactants reduced the surface tensions of aqueous solutions to about 30 to 40 mJ m(-2). Biochemical and physicochemical analyses revealed that the biosurfactants released were glycolipids. An acid-precipitated fraction was extremely surfactive and was identified as a rhamnolipidlike compound. In a parallel-plate flow chamber, the number of Streptococcus mutans NS cells adhering to glass with and without a salivary conditioning film in the presence of biosurfactant-releasing S. mitis BA and BMS (surface coverage, 1 to 4%) was significantly reduced compared with the number of S. mutans NS cells adhering to glass in the absence of S. mitis. S. mutans NS adhesion in the presence of non-biosurfactant-releasing S. mitis BA and BMS was not reduced at all. In addition, preadsorption of isolated S. mitis biosurfactants to glass drastically reduced the adhesion of S. mutans NS cells and the strength of their bonds to glass, as shown by the increased percentage of S. mutans NS cells detached by the passage of air bubbles through the flow chamber. Preadsorption of the acid-precipitated fraction inhibited S. mutans adhesion up to 80% in a dose-responsive manner. These observations indicate that S. mitis plays a protective role in the oral cavity and protects against colonization of saliva-coated surfaces by cariogenic S. mutans.

The effect of herbal extracts in an experimental mouthrinse on established plaque and gingivitis

The purpose of the present study was to establish in vitro the inhibiting effect of a herbal extract mixture on a selected number of micro-organisms and to test in vivo the effect of a mouthwash containing 6.3 mg/ml herbal extract mixture on plaque and gingivitis as compared to a minus active control mouthrinse. The herbal extract was a mixture of: Juniperus communis (juniper), Urtica dioca (nettle), Achillaea millefolium (yarrow); 1:1:1. In the study, in-vitro, the effect of pure herbal extract mixture on acid production of Streptococcus mutans was tested and the minimum inhibitory concentrations (MIC) of the following micro-organisms were tested: Streptococcus mutans, Streptococcus mitis, Actynomyces viscosus, Actynomyces naeslundii, Actinobacillus actinomycetemcomitans, Prevotella intermedia, Campylobacter rectus, Fusobacterium nucleatum, Veillonella parvula. The MIC-values for A. viscosus and P. gingivalis were 100 mg/ml. The MIC-values for A. naeslundii and A. actinomycetemcomitans were considerably lower (10 mg/ml). S. mitis was the most susceptible of the tested organisms to the extract with a MIC value of 1 mg/ml. S. mutans, C. rectus, V. parvula, and F. nucleatum were not influenced by the extracts. No inhibitory effect of the 6.3 mg/ml herbal extract mixture was observed on the acid production of S. mutans. For the study in-vivo, 45 volunteers were selected on the basis of having moderate gingival inflammation. As efficacy parameters the plaque index, modified gingival index and angulated bleeding index were assessed. The subjects were randomly divided among 3 experimental groups (2x test and 1 'minus active' control). The participants were requested to rinse with 10 ml of mouthwash twice a day for a period of three months. After 6 weeks and 3 months, the same clinical indices as at baseline were recorded. The results show no difference between the two test groups and the control group. In conclusion, the results of the present study have shown that the mixture of the 3 herbal extracts, Juniperus communis, Urtica dioca and Achillaea millefolium when used in a mouthrinse has no effect on plaque growth and gingival health.

Restoration of the partially edentulous mouth--a comparison of overdentures, removable partial dentures, fixed partial dentures and implant treatment

OBJECTIVES

Loss of posterior teeth may result in the loss of neuromuscular stability of the mandible, reduced masticatory efficiency, loss of vertical dimension of occlusion and poor aesthetics. Prosthetic rehabilitation should aim at restoring the vertical dimension and increasing the occlusal contact area in the premolar/molar region. Overdentures are particularly indicated in patients with a severe loss of periodontal attachment, uncertain periodontal prognosis and complicated functional or aesthetic conditions. Removable partial dentures are particularly indicated in Kennedy Class I cases when there is need for a simple and economic solution. Placement of a removable partial denture with occlusal overlays is a simple way to restore occlusal face height. Cross-arch cantilevered fixed partial dentures are primarily indicated for stabilization of periodontally weakened abutments. Short unilateral or bilateral bridges are a solution in patients who refuse removable appliances and who cannot afford more extensive rehabilitation with fixed prosthodontics. Rehabilitation with a fixed partial denture supported by means of osseointegrated implants is the optimal solution in Kennedy Class II cases provided that the bone conditions are appropriate. For any prosthetic treatment, a definite recall system should be established depending on the patient's degree of cooperation, caries susceptibility, periodontal status and the rate of residual ridge resorption. This is essential in order to obtain a satisfactory prognosis. In a patient with poor oral hygiene, the best solution, with regard to the prognosis of the remaining teeth, is to abstain from any prosthetic treatment.

METHODS

This manuscript reviews the current literature to identify treatment options for the Kennedy Class I and II partially edentulous patient.

Carbohydrate depletion of immunoglobulin A1 by oral species of gram-positive rods

Bacterial deglycosylation of immunoglobulin Al (IgA1), the dominant isotype of antibody in the oral cavity, probably provides both nutrition as well as protection to the oral bacterial community. Representative strains of oral gram-positive rods were tested for their ability to remove carbohydrates from IgA1. Detection of sialic acids was performed by means of high-performance liquid chromatography (HPLC) separation (Aminex HPX-87H) and ultraviolet light absorption at 190 nm, and neutral carbohydrates were measured by HPLC separation (Capcell Pak C-18 SG 120) and ultraviolet light absorption at 245 nm after derivatization. Four strains of Actinomyces naeslundii, two strains of Corynebacterium matruchotii and one of two strains of Actinomyces odontolyticus partially or totally removed sialic acid, while two strains of Propionibacterium propionicus and the other strain of A. odontolyticus did not. Complete correlation was observed between sialic acid removal, neuraminidase activity measured with fluorogenic substrate and with one exception, altered immunoelectrophoretic mobility of IgA1. Only limited removal of other carbohydrates was observed with poor correlation to exoglycosidase activities measured with chromogenic substrates. Desialylation increases the susceptibility of glycoproteins, including IgA1, to proteolysis. Therefore, the desialylation of IgA1 by oral gram-positive rods may facilitate the proteolytic activities of other oral bacteria, and the concerted action may positively influence the survival of the bacteria in the oral community.

Site-related streptococcal attachment to buccocervical tooth surfaces. A correlative micromorphologic and microbiologic study

Scanning electron (SEM) microscopy of epoxy replicas made from dental impressions has shown that in buccal gingival recession the root surfaces are devoid of cementum, leaving the dentin exposed. In this study replication techniques were applied to correlate the micromorphology of the buccocervical region with early streptococcal attachment. The subjects were 27 healthy young adults. The buccocervical surfaces of all the premolars were meticulously cleaned. The subjects fasted for 2 h before impression-taking. Replicas were made from impressions in hydrophilic A-silicone, and streptococcal attachment was visualized by light microscopy of mitis-salivarius agar replicas incubated anaerobically for 48 h. The surface micromorphology was documented by SEM of corresponding epoxy replicas. Colonization only 2 h after cleaning was very sparse. Sites with healthy or inflamed gingivae had markedly different colonization patterns in the sulcular region. In 4 subjects with a total of 12 sites where gingival recession, undetected clinically, was disclosed by SEM, representative colonies were retrieved and identified microbiologically to species level. Two healthy sites per subject were also sampled. Streptococcus mutans and S. sobrinus were identified from eight sites with exposed root dentin. S. oralis predominated on the enamel surfaces. The method offers a valuable complement to in situ and in vitro microbiologic studies of exposed dentin and a novel technique for sampling clinical isolates of streptococci.

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.

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)

Effects of denture-wearing habits on periodontal health of abutment teeth in patients with overdentures

The effect of denture-wearing habits was studied in 31 overdenture wearers (17 day-and-night wearers, 14 day wearers) during a period of 5 years with controlled oral hygiene. Prior to prosthetic treatment, intensive instruction and motivation in oral hygiene were carried out and the patients were recalled 2-4 x yearly during the study period. Before treatment, mean plaque index (PlI) and gingival index (GI) were 1.5 and 1.6, respectively, in both groups of patients. During the study period, mean PlI and GI were 0.3-0.6 and 0.6-0.8, respectively, in the group of day wearers and 0.5-1.0 and 1.0-1.2, respectively, in the group of day-and-night wearers. With regard to the GI, this difference was statistically significant. Furthermore, during the study period, 20% of the abutment tooth surfaces showed attachment loss (1-4 mm) in the group of day-and-night wearers against 8% of the tooth surfaces in the group of day wearers. This difference was statistically significant. During the 5 years, 40 carious lesions developed in the group of day-and-night wearers against 3 in the group of day wearers. The results of this study have shown that day-and-night wearing of dentures is a major periodontitis and caries risk factor in complete overdenture wearers with controlled oral hygiene.

Comparison of the distribution of Actinomyces in dental plaque on inserted enamel and natural tooth surfaces in periodontal health and disease

The distribution of Actinomyces naeslundii, Actinomyces viscosus and Actinomyces odontolyticus in healthy and diseased adult populations was studied in 3 different ways. First, supragingival plaque formation at 2 through 72 h was examined in 12 periodontally healthy adults using a removable pre-measured surface of enamel bonded to molars and premolars. Second, a cross-sectional examination of the composition of both supragingival and subgingival plaque of unknown age was conducted in 205 adults exhibiting periodontal health to moderate disease. Third, the effects of oral hygiene instruction and root planing on the subgingival microflora of a subset of 19 subjects with moderate periodontitis were examined. The evaluation of 12 adults revealed that the predominant species in early plaque formation (2, 4 and 8 h) was A. odontolyticus. A. viscosus and A. naeslundii were present in developing plaques in almost all subjects in 2-h plaque, but absent in half the subjects when 4-, 8- or 24-h plaque was examined. These two species significantly increased in numbers per mm2 enamel surface area in 48- and 72-h plaques. A. odontolyticus was not related to clinical signs of periodontal disease in 205 adults, and its subgingival proportions in plaque did not change following periodontal treatment of 19 individuals. A. naeslundii was found in significantly higher numbers in supragingival than subgingival plaques in the 205 adults examined. The mean proportion of A. naeslundii significantly decreased as the magnitude of probing depth and attachment loss increased. The proportions of A. naeslundii and A. viscosus were found to be significantly increased in subgingival plaques following periodontal treatment.

Distribution and isolation frequency of eight streptococcal species in saliva from predentate and dentate children and adults

The isolation frequency and distribution of eight recently defined streptococcal species have been investigated in the saliva of adults and that of both predentate and dentate children. The effects of frequency of sugar intake and tooth presence on the distribution of streptococcal species were also analyzed. Saliva samples were collected from 121 subjects divided into three study groups: (a) 56 predentate children (predentate group), (b) 37 dentate children (dentate group), and (c) 28 adults (adult group). Up to 17 biochemical and enzymatic tests were used to categorize streptococcal isolates into S. mitis, S. oralis, S. salivarius, S. anginosus, S. sanguis, S. vestibularis, S. mutans, and S. gordonii. The mean total and streptococcal salivary colony-forming units (CFU) were lowest in the predentate group and highest in the adult group. Streptococci were found in all the study subjects, and there was no obvious relationship between the total or streptococcal CFU and the number of teeth or the frequency of sugar intake. There was a wide variation in the isolation frequency of streptococcal species in the three study groups. S. mitis, S. oralis, and S. salivarius were the most frequent species isolated, and together they comprised 83% of the total streptococcal isolates. In contrast to studies using older classifications, S. sanguis was a minor species in the saliva though found more often in adults than in children (p < 0.04). S. anginosus was a minor species found in about 10% of adults and children. S. gordonii was detected rarely and only in dentate subjects. S. mutans was detected only in dentate subjects, significantly greater in adults (57.1%) than in children (5.4%, p < 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Conservation of an Actinomyces viscosus T14V type 1 fimbrial subunit homolog among divergent groups of Actinomyces spp

The type 1 fimbrial subunit gene of the human Actinomyces viscosus T14V was used as a DNA probe in Southern analyses to detect related DNA sequences in 16 of 30 strains of Actinomyces spp. under conditions of high stringency. The organisms with homology to the DNA probe included two human and six nonhuman A. viscosus, three human and three nonhuman A. naeslundii, and two A. bovis isolates. Homologous DNA sequences were not detected in strains of A. odontolyticus and A. israelii examined in this study. Northern (RNA) blot analysis revealed expression of a transcript from each of the A. viscosus and A. naeslundii strains and from one A. bovis strain that was comparable in size to that detected from A. viscosus T14V. Cell surface fimbriae were observed on a majority of the strains that expressed the transcript. Various degrees of cross-immunoreactivities between these strains and antibodies specific for type 1 fimbriae of A. viscosus T14V were also observed by colony immunoassay. Thus, the data clearly demonstrate the existence in, and expression by, divergent Actinomyces groups of genomic sequences that are closely related to the type 1 fimbriae of A. viscosus T14V.

Ecology of viridans streptococci in the oral cavity and pharynx

Recently published taxonomic studies of viridans streptococci have resulted in several changes in the nomenclature and definition of oral streptococcal species. With this background, the ecology of streptococci in the oropharyngeal cavities was reinvestigated. The results based on the examination of 1426 streptococcal isolates confirmed and extended earlier findings. Apart from mature supragingival plaque, which contained a mixture of all orally encountered streptococci, each site showed a characteristic streptococcal flora. Initial dental plaque formation is primarily associated with Streptococcus sanguis, Streptococcus mitis biovar 1 and Streptococcus oralis. Our investigation showed that S. sanguis and S. mitis biovar 1 were the most prominent streptococci, also on buccal mucosa. In contrast, S. oralis was almost exclusively found in initial dental plaque. Streptococcus gordonii, formerly part of S. sanguis, was found in small numbers on the oropharyngeal mucosa and in mature supragingival plaque. The dorsum of the tongue was dominated by S. mitis biovar 2 and Streptococcus salivarius, the latter of which was predominant also on the pharyngeal mucosa. Streptococcus anginosus was by far the most predominant streptococcus in subgingival plaque. Immunoglobulin A1 (IgA1) protease-producing streptococci were primarily isolated from initial dental plaque and from the buccal mucosa. This lends further support to the concept of IgA1 proteases being important for the ability of streptococci to evade the local immune defence during their initial colonization of certain oral surfaces.

Adherence of Porphyromonas (Bacteroides) gingivalis to Streptococcus sanguis in vitro

Intergeneric bacterial adherence is responsible for the complexity of the microbiota in human dental plaque and is believed to enable some extraneous bacteria to initially colonize the human oral cavity. Some current evidence indicates that Streptococcus sanguis, an early colonizer of teeth, enhances subsequent colonization by Porphyromonas (Bacteroides) gingivalis, a bacterium associated with advanced adult periodontitis. In this study, selected strains of P. gingivalis and S. sanguis were tested for their adherence activities in vitro. A differential filtration assay was devised in which one member of the test pair was radiolabeled. Heterogeneous aggregates that formed in mixed suspensions were collected on polycarbonate filters (8-microns pore size) and were washed free of individual bacteria and small homologous clumps. P. gingivalis 381, W50, JKG7, and 33277 adhered to S. sanguis G9B, M5, Challis 6, and 38. P. gingivalis A7A1-28 did not adhere well to S. sanguis under these conditions. More precise measurements of intergeneric adherence were obtained with an alternative assay with radiolabeled P. gingivalis and an artificial dental plaque composed of S. sanguis coupled to cyanogen bromide-activated agarose beads. CNBr-agarose was selected as the supporting matrix for the plaque because it was uniformly and permanently coated with S. sanguis and because P. gingivalis had negligible adherence activity for streptococcus-free beads. P. gingivalis W50 grown to the early stationary phase adhered to S. sanguis-coated beads in higher numbers than either midlogarithmic- or late-stationary-phase cells. Intergeneric adherence was not inhibited or reversed by the presence of lactose or other monosaccharides or disaccharides. Pretreatment of either bacterium with trypsin or proteinase K reduced subsequent adherence by 86 to 100%. Neuraminidase treatment of P. gingivalis caused 98% reduction of adherence, whereas similar treatment of S. sanguis caused only a 2% loss. Preincubation of P. gingivalis at 60 degrees C for 30 min decreased subsequent adherence to S. sanguis-coated beads by 94%. Adherence was reduced by 96% when bacteria were assayed while suspended in human whole saliva or when pretreated with saliva and subsequently assayed in buffer. The concentration of whole human saliva required to inhibit 50% adherence in this assay was 23 micrograms per ml (1:200 dilution). Suspension of the bacteria in normal rabbit serum resulted in 94% inhibition of adherence. These data indicate that saliva and serum may be important host defense factors for controlling Porphyromonas-Streptococcus adherence.

Molecular aspects of immunoglobulin A1 degradation by oral streptococci

Using a panel of 143 strains classified according to a novel taxonomic system for oral viridans-type streptococci, we reexamined the ability of oral streptococci to attack human immunoglobulin A1 (IgA1) molecules with IgA1 protease or glycosidases. IgA1 protease production was an exclusive property of all strains belonging to Streptococcus sanguis and Streptococcus oralis (previously S. mitior) and of some strains of Streptococcus mitis biovar 1. These are all dominant initiators of dental plaque formation. Degradation of the carbohydrate moiety of IgA1 molecules accompanied IgA1 protease activity in S. oralis and protease-producing strains of S. mitis biovar 1. Neuraminidase and beta-galactosidase were identified as extracellular enzymes in organisms of these taxa. By examination with enzyme-neutralizing antisera, four distinct IgA1 proteases were detected in S. sanguis biovars 1 to 3, S. sanguis biovar 4, S. oralis, and strains of S. mitis, respectively. The cleavage of IgA1 molecules by streptococcal IgA proteases was found to be influenced by their state of glycosylation. Treatment of IgA1 with bacterial (including streptococcal) neuraminidase increased susceptibility to protease, suggesting a cooperative activity of streptococcal IgA1 protease and neuraminidase. In contrast, a decrease in susceptibility was observed after extensive deglycosylation of the hinge region with endo-alpha-N acetylgalactosaminidase. The effector functions of IgA antibodies depend on the carbohydrate-containing Fc portion. Hence, the observation that oral streptococci may cleave not only the alpha 1 chains but also the carbohydrate moiety of IgA1 molecules suggests that the ability to evade secretory immune mechanisms may contribute to the successful establishment of these bacteria in the oral cavity.

Utilization of mucin by oral Streptococcus species

The ability of oral Streptococcus strains to utilize oligosaccharide chains in mucin as a source of carbohydrate was studied in batch cultures. Pig gastric mucin, as a substitute of human salivary mucin, was added to chemically defined medium containing no other carbohydrates. Strains of S. mitior attained the highest cell density, while mutans streptococci: S. mutans, S. sobrinus, S. rattus, grew very little in the medium with mucin. S. mitis, S. sanguis, and S. milleri in decreasing order, showed intermediate growth. Mucin breakdown as measured by sugar analyses indicated that oligosaccharide chains were only partially degraded. Every strain produced one or more exoglycosidases potentially involved in hydrolysis of oligosaccharide. The enzyme activities occurred mainly associated with the cells, and very little activity was found in the culture fluids. The relationships between glycosidase activities and growth, or mucin degradation were not always clear.

An in vitro method to study the adherence of bacteria to saliva-treated tooth enamel sections

An in vitro bacterial adherence assay which employed human tooth enamel sections precoated with saliva and an epifluorescent staining technique with acridine orange was developed. The assay was used to study the adherence properties of fresh and type strains of the following oral bacterial species: Bacteroides gingivalis, Bacteroides intermedius, Capnocytophaga species, Haemophilus aphrophilus, Actinobacillus actinomycetemcomitans, Peptostreptococcus species, Veillonella species, Actinomyces israelii, Streptococcus salivarius and Streptococcus sanguis. Approximately half of the bacteria tested adhered well to enamel, including the fresh isolates of B. gingivalis, B. intermedius, Veillonella species and S. sanguis. Adherence did not correlate in all cases with the known distribution of these species in vivo. Three-quarters of the fresh strains adhered better than the type strains of the same species. The assay method is an alternative to the widely used hydroxyapatite bead assay.

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.