In vitro streptococcal adherence on prosthetic and implant materials. Interactions with physicochemical surface properties

The aim of this study was to evaluate streptococcal adherence to eight currently used prosthetic and implant materials, and enamel samples, after a salivary coating and to investigate the influence of substrata surface free energy (SFE) and its polar and non-polar components, as well as bacterial surface characteristics, on bacterial adherence. Our results indicate a moderate hydrophobic character of saliva-coated surfaces and a pronounced basic character of the polar component of SFE values, except for one substrata. The lowest colonization was observed with enamel samples and the lowest values of adherent bacteria on the different substrata were observed with the hydrophilic bacterial strain. Both the nature of the substrata and the nature of the bacterial strains could have an effect on the extent of bacterial adhesion. When the interrelationship between the number of adherent bacteria and the surface properties of bacteria and substrata were analysed, bacterial adherence correlated with the non-polar component of substrata SFE (r = 0.8, P = 0.02) and with the adhesion to the solvents (r = 0.8, P < 0.0001). These results are consistent with the thermodynamic theory and underline the importance of acid-base characteristics of the cell surface when one is studying bacterial adherence on dental casting alloys and implant materials.

Restriction endonuclease analysis of Staphylococcus epidermidis DNA may be a useful epidemiological marker

We compared the epidemiological markers of 13 Staphylococcus epidermidis strains isolated from an adult inpatient during a febrile episode and 23 S. epidermidis strains isolated during a presumptive outbreak of nosocomial infection in a neonatal ward. The total DNA restriction endonuclease analysis (REA) was processed along with the following conventional markers: biotyping, serotyping, phage typing, antibiotic susceptibility profiles, and plasmid profiles. The REA method was reproducible, giving stable results both in vitro and in vivo. For the hospitalized adult patient, the conventional markers of the 13 strains were concordant and the restriction profiles were identical. Five restriction groups were demonstrated during the course of the outbreak. Within two of the groups, the identities of all of the markers were used to verify whether all of the isolates belonged to the same cell clone. In a third group, combined analysis of the conventional markers and REA had to be used to demonstrate isolate similarity. On the other hand, in another group, none of the markers were similar; interpretation was not easy. An epidemiological study of S. epidermidis infections in hospitals must take into account all of the epidemiological markers: biotypes, serotypes, phage types, antibiograms, plasmid profiles, and REA.

Effect of hydrophobicity on in vitro streptococcal adhesion to dental alloys

Non-specific interactions such as electrostatic interactions, and surface free energy are of importance in bacterial adhesion to dental surfaces as they determine whether or not bacteria are attracted to the surface. The relationship between adherence of Streptococcus mitis, S. mutans, S. oralis and S. sanguinis on precious and non-precious dental alloys, and the bacterial and alloy surface hydrophobicities (a measure of the surface free energy) was studied. The number of adhering bacteria was determined by fluorescence microscopy counts. The hydrophobicity of the bacteria and alloy surfaces were evaluated by adhesion to hexadecane and water contact angles, respectively. Our results showed that (i) the surfaces of the tested alloys were hydrophobic, (ii) S. sanguinis, S. mutans and S. oralis were hydrophobic, and (iii) S. mitis was hydrophilic. S. oralis, the more hydrophobic strain, demonstrated the highest adherence on the tested materials, whereas S. mitis adhered least on the hydrophobic surfaces. For the tested alloys, bacterial adherence was highest for the high gold content alloy, and lowest for the non-precious alloy. Our results showed that for the tested bacterial strains, there was a significant correlation between bacterial adhesion and substratum hydrophobicity: hydrophobic metal surfaces favor adhesion of hydrophobic bacteria.

Antimicrobial activity of amalgams, alloys and their elements and phases

OBJECTIVES

This in vitro study aimed to evaluate the antibacterial effect of amalgams, alloys, elements and phases against two cariogenic bacteria, Actinomyces viscosus and Streptococcus mutans.

METHODS

Test materials comprised: (i) commercial amalgams comprising Amalcap (Vivadent), Cavex Avalloy LC and DP (Cavex), Cupromuc (Merz), Fluoralloy and Synalloy (Dentoria); (ii) Ag-Cu alloy; (iii) gamma, gamma 1, gamma 2 and Cu6Sn5 phases; (iv) pure metal samples and chloride solutions of copper, mercury, tin and zinc; and (v) aqueous sodium fluoride. Bacterial suspensions of each of the two bacteria were grown in the presence of the test materials for 24 h. Antimicrobial effectiveness was assessed by measuring reduction in optical density at 640 nm using a visible spectrophotometer.

RESULTS

Cupromuc/Fluoralloy, non gamma 2 amalgams and Amalcap displayed high, moderate and no antibacterial activity, respectively. Antibacterial effectiveness was not related to copper content. Whereas mercury, copper, Ag-Cu alloy, fluoride and zinc showed antibacterial activity (Hg > Cu > F > Zn), tin, gamma phases and Cu6Sn5 showed no such activity.

SIGNIFICANCE

Although the fluoride and copper solutions were most effective at 50 micrograms ml-1 concentration, their antibacterial action was still significant, albeit reduced, at 10 micrograms ml-1 concentration. This was not the case for mercury chloride which was just as effective at both concentrations. Our results show that although mercury and copper contribute significantly to the antibacterial properties of amalgams, a high copper content does not necessarily relate to high antibacterial effectiveness. These elements could be useful in conferring antibacterial properties to amalgam although their effects on host cells must be investigated.

Interactions between non-immune host cells and the immune system during periodontal disease: role of the gingival keratinocyte

Periodontal disease and inflammatory dermatoses, such as psoriasis, are characterized by the accumulation of dense inflammatory infiltrates immediately beneath the epithelial cell layer of the gingiva and skin, respectively. Dermatologists are increasingly aware that the epidermal keratinocyte probably contributes to inflammatory disease progression by secreting a number of pro-inflammatory cytokines and expressing various adhesion molecules. In psoriatic lesions, it is now believed that epidermal keratinocytes may also act as antigen-presenting cells and participate directly in the superantigenic activation of T-cell clones, some of which may initiate, contribute to, or maintain the disease process. Although the role of the host response in periodontal disease has been extensively studied over the years, very little is known about the contribution of the gingival keratinocyte to the inflammatory response. The available published information is discussed in this review, and we suggest that, like its epidermal counterpart, the gingival keratinocyte may participate actively in the pathogenesis of periodontal disease.

An investigation into the use of restriction endonuclease analysis for the study of transmission of Actinomyces

DNA fingerprints of 28 reference strains of Actinomyces, comprising representatives of different species and serotypes, and 19 isolates recovered from 16 periodontal patients was performed. The aim was to determine the potential of the method for detecting strain differences in terms of discriminatory power and to evaluate its usefulness in the typing of Actinomyces strains for eco-epidemiological studies. Among the 17 restriction endonucleases tested, Bst EII, Pvu II and Sma I proved to be the most suitable for the genus Actinomyces restriction digest analysis. Visual comparisons of Bst EII, Pvu II and Sma I digest patterns of chromosomal DNA revealed clear differences within species but also within serotypes of Actinomyces that are otherwise identical. The method offers the qualities for use as an epidemiological tool for identifying sources and tracing routes of transmission of Actinomyces: stability, reproducibility, ease of preparation and interpretation and enough sensitivity for detection of differences between morphologically and serologically similar strains of Actinomyces.

Automatic enumeration of adherent streptococci or actinomyces on dental alloy by fluorescence image analysis

The aim of the present study was to develop an automated image analysis method to quantify adherence of Streptococcus sanguinis or Actinomyces viscosus on surfaces of a currently used dental alloy. Counting such bacterial strains was difficult because of their arrangement, thus S. sanguinis being a coccus arranged in chains or pairs, and A. viscosus a long complexly arranged polymorph rod. Direct counting of fluorescently stained adherent bacteria was done visually and with image analysis methods. To differentiate these two morphotypes, two programs were developed: (i) for streptococci, thresholding and selection of the object maxima, and (ii) for actinomyces, two step thresholding and processing of the characteristic points of the object skeletons. The triplicate enumerations for each bacterial strain were not significantly different (p > 0.005) and correlations between visual counting and automated counting were significant (r = 0.91 for S. sanguinis and r = 0.99 for A. viscosus, p <00.0001). These rapid and reproducible methods, allowed us to count either cocci or rods, adherent on an inert substratum, in high density conditions.

Rapid isolation of DNA from Actinomyces

DNA could not be quickly extracted from members of the genus Actinomyces by the usual methods of lysis. Treatment of 7 different actinomyces cells with lysozyme and achromopeptidase, both 5 mg/g wet cells, for 2 h, followed by SDS (0.2%), proteinase K (5 mg/g wet cells) and EDTA (lmM) for 1 h, lysed the cells. The yield obtained in one day was 337 micrograms per 200 mg of bacterial cells. The treatment was also found to work effectively on strains belonging to Veillonella, Staphylococcus, Fusobacterium and Bifidobacterium genera.

Intra-familial distribution of Fusobacterium nucleatum strains in healthy families with optimal plaque control

Fusobacterium nucleatum, a Gram-negative anaerobic rod associated with periodontal disease, is also found in healthy individuals and is considered part of the indigenous oral microflora. Although intra-familial transmission of periodontal pathogens has been documented, there are no data relating transmission of F. nucleatum. This study investigated the distribution of F. nucleatum strains in 4 strictly healthy families. 32 F. nucleatum strains were isolated from 19 individuals (8 parents and 11 children aged 1-13 years). DNA was extracted and digested with the restriction endonucleases EcoRI, TaqI and HindIII. The digests were separated by electrophoresis through 0.8% agarose gels at 40 V overnight, in TBE buffer containing 1 microg/ml ethidium bromide, and photographed. The DNA was transferred to nylon filters by Southern blotting and hybridized with a digoxigenin labelled E. coli rRNA probe (Kit Dig DNA Labelling mixture - Boehringer). Probed DNA was visualized colorimetrically (CSPD Luminescent Detection Kit Boehringer) and photographed (Amersham). We found that 10/11 children shared identical ribotypes with at least one of their respective parents. Some of the children also harbored a unique additional ribotype. On the basis of indistinguishable restriction endonuclease and ribotype patterns these results support the hypothesis that intra-familial transmission of F. nucleatum is possible.

Antibacterial properties of five dental amalgams: an in vitro study

The antibacterial activity of five commercially available amalgams (Cupromuc, Dispersalloy, Fluoralloy, Predalloy, and Synalloy) against two bacterial species frequently isolated from dental plaque and caries (Actinomyces viscosus and Streptococcus mutans) was studied by use of a modification of the method of Orstavik (1985). All amalgams displayed some antibacterial properties. This antibacterial activity was amalgam- and bacteria-dependent. Cupromuc and Fluoralloy were the most active, and the non-gamma 2 amalgams showed intermediate activity. Combined with mechanical and biological properties, these differences should be taken into account when one is choosing an amalgam for clinical use.

Clinical usefulness of microbiological diagnostic tools in the management of periodontal disease

Periodontal diseases comprises a group of chronic inflammatory conditions affecting tooth supporting structures. It has been known for a long time that pathogenic oral bacteria colonizing the tooth surface are associated with the initiation of the disease process. However, to date, a dozen or so bacterial species have been implicated in the pathogenesis of periodontal disease and no one species by itself is synonymous with disease onset. This multibacterial etiology renders the diagnosis of active periodontal disease based on microbiological data difficult. Numerous studies have attempted to relate the usefulness of microbiological diagnostic aids such as microscopy, bacterial culture, immunological and enzymatic assays. Furthermore, recent technical advances have resulted in the use of nucleic acid probes and amplification techniques for the identification of genetic material belonging to potential periodontal pathogens. Despite the availability of a large number of microbiological testing protocols, identification of the microbial etiological agents remains hampered by the complexity of the microbial challenge during periodontal disease. This review discusses the clinical usefulness of these tests in detection and management of periodontal disease.

Clonal analysis by ribotyping of Fusobacterium nucleatum isolates obtained from healthy young adults with optimal plaque control

Fusobacterium nucleatum is a Gram-negative anaerobic rod implicated in the pathogenesis of periodontal disease. However, this organism has also been frequently identified in high numbers in healthy adults. These observations suggest that the species may comprise different clonal types, some of which may participate in disease. The purpose of the present investigation was to use restriction endonuclease analysis (REA) and ribotyping to characterize F. nucleatum clonal types isolated from healthy young adults with optimal plaque control and investigate the stability of some of these clonal types. A group comprising 11 dental students and 11 dental outpatients with optimal plaque control was sampled. Clonal stability was investigated by sampling the dental student group at baseline and at 16 months. One hundred and thirty-two clinical isolates of F. nucleatum were successfully recovered from 15/22 individuals. For the positive subjects, 29 different clonal types were identified by REA and ribotyping, each subject and site being colonized by 1-4 clonal types. For the dental students, 9 and 15 different clonal types were identified at baseline and 16 months, respectively. None of the students harboured identical clonal types at both sampling times. Our results show that ribotyping is a useful technique for monitoring the distributions of F. nucleatum clonal types and indicate that healthy individuals with optimal plaque control can be colonized by more than one F. nucleatum clonal type and that these clonal types appear to be unstable.

rRNA gene restriction patterns as possible taxonomic tools for the genus actinomyces

Species delineation in the genus Actinomyces remains unclear, particularly regarding the two taxa, A. naeslundii and A. viscosus. The ribotyping patterns of 64 strains of Actinomyces, representing 8 species and comprising different serotypes, were studied as possible taxonomic tools, using an acetyl-aminofluorene (AAF)-labelled E. coli 16S + 23S rRNA probe. Similarities between patterns were assessed using Jaccard's coefficient and clustering achieved using the unweighted pair-group method with average linkage (UPGMA) on a Macintosh II (Apple, Cupertino, USA) computer. The dendrogram obtained from the ribotypes gave results which were in reasonable agreement with many previous reports: A. bovis, A. gerensceriae, A. israelii, A. meyerii, A. odontolyticus and A. pyogenes were found to be distinct species but the two taxa A. naeslundii and A. viscosus remained unclear. Further investigations, using a larger number of A. naeslundii and A. viscosus strains and other endonucleases, need to be carried out to provide more information concerning the relatedness of these two taxa. Nevertheless, these preliminary results suggested that the Actinomyces chromosome contains multiple rRNA operons which may be used as an epidemiological and taxonomical tool.

In vitro evaluation of the antibacterial effects of intracanal micro plasma system treatment

Forty freshly extracted single-rooted teeth were prepared to a size 25 master apical file, autoclaved, and inoculated with a known quantity of Actinomyces naeslundii. The teeth were divided into four groups (n = 10), including an untreated control group. The three treatment groups were exposed to Micro Plasma System (MPS), 0.5% NaOCl and 0.5% NaOCl + MPS respectively. The content of each root canal was absorbed by sterile paper points, diluted in 2 ml Schaedler Broth Medium, and incubated on blood agar. The number of CFU was determined. Data analysis, using an analysis of variance and Scheffe's test at the 1% level (Statview II software), indicated a significant reduction in CFU count for the three treatment groups compared to the control group. For the three treatment groups, no significant intergroup differences were observed.

Molecular typing of Actinomyces pyogenes isolates

The molecular characterization of 28 clinical Actinomyces pyogenes strains was attempted. SDS-PAGE protein profiles did not allow to distinguish isolates. Restriction endonuclease analysis of total DNA gave the finest differentiation between strains but the profiles were difficult to read. Ribotypes after DNA digestion by Bst EII or Sma I have a high discriminatory power and are more helpful epidemiological markers. No relationship could be demonstrated between molecular types and clinical sources.

[The measurement of the tooth-restoration material gap: the value of SEM]

The purpose of this article was to describe a method of measuring the interface between cavity walls and restorative materials and to evaluate it by comparing the interface of amalgam, composite restorations and cavity walls. With the different restorative materials the interface could be measured. Its value was dependent of the type of restoration. This methodology is available for all restorative biomaterials. It could be of interest in clinical evaluation of restorative materials.

[Secretary IgA and the oral cavity: general review]

The authors present a synthesis of the knowledge concerning the nature and origin of secretory IGA as well as its main components (J chain and secretory component) in the oral cavity. This IgA is the main mediator of humoral immunity and is the most frequently identified immunoglobulin in saliva. Its role in the protection of mucosae as well as in the anti-caries immunity is presented.

[Initial colonization of composite resins by Streptococcus mutans: the influence of polishing]

The purpose of the present investigation was to compare the in vitro initial colonization of Streptococcus mutans on three composite materials (HERCULITE, FILLISPAD and SILIFILL) regarding the polishing procedure (SOFT-LEX, 3M). Surface roughness and bacterial deposit were analyzed by SEM and the deposit was estimated using a modified method of SKJORLAND. Results indicated that surface roughness was reduced by the polishing procedure, but this roughness was more important at the periphery of restorations. Bacterial deposit was strongly reduced on the polished materials but bacteria not adhered in the same number on the composites with a comparable surface roughness: the accumulation of bacteria was less important on FILLISPAD materials. It is concluded that the initial colonization of resin composites was not only dependent of surface roughness.