Ervin I. Weiss

Surface antimicrobial activity and biocompatibility of incorporated polyethylenimine nanoparticles

The antimicrobial effect and biocompatibility of insoluble cross-linked quaternary ammonium polyethylenimine (PEI) nanoparticles incorporated at 1 or 2%w/w in a resin composite were assayed. The antimicrobial effect against Staphylococcus aureus, Staphylococcus epidermidis, Enterococcus faecalis, Pseudomonas aeruginosa and Escherichia coli was tested using the direct contact test (DCT), agar diffusion test (ADT) and scanning electron microscopy (SEM). Biocompatibility was tested by assessing macrophage viability, and TNFalpha secretion. Samples incorporating 2%w/w nanoparticles inhibited the growth of all bacterial strains tested. Reducing the amount of the added nanoparticles to 1%w/w resulted in complete inhibition of S. aureus and E. faecalis, and decreased growth of S. epidermidis, P. aeruginosa and E. coli (p<0.0001). The DCT results were confirmed by SEM. However, ADT showed no inhibition halo in all test bacteria, indicating the antimicrobial nanoparticles are not diffusing into the agar milieu. Biocompatibility tests revealed macrophage viability, and TNFalpha secretion was not altered by the presence of the nanoparticles in the resin. Incorporation of PEI nanoparticles in a resin composite had a long lasing antimicrobial effect against a wide range of bacteria with no measured effect on biocompatibility.

Inhibition of Helicobacter pylori adhesion to human gastric mucus by a high-molecular-weight constituent of cranberry juice

Abstract A high–molecular–weight constituent of cranberry juice has been found to inhibit the sialyllactose specific adhesion of Helicobacter pylori strains to immobilized human mucus, erythrocytes, and cultured gastric epithelial cells. Different isolates of H. pylori differ in thenaffinity to the cranberry juice constituent. Cranberry juice may also inhibit adhesion of bacteria to the stomach in vivo, and may prove useful for the prevention of stomach ulcer that is caused by H. pylori.

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.

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.

Potential Oral Health Benefits of Cranberry

In the past decade, cranberry extracts have been attracting ever-growing attention by dental researchers. The potential benefits of cranberry components in reducing oral diseases, including dental caries and periodontitis, are discussed in this review. A non-dialysable cranberry fraction enriched in high molecular weight polyphenols has very promising properties with respect to cariogenic and periodontopathogenic bacteria, as well as to the host inflammatory response and enzymes that degrade the extracellular matrix. Cranberry components are potential anti-caries agents since they inhibit acid production, attachment, and biofilm formation by Streptococcus mutans. Glucan-binding proteins, extracellular enzymes, carbohydrate production, and bacterial hydrophobicity, are all affected by cranberry components. Regarding periodontal diseases, the same cranberry fraction inhibits host inflammatory responses, production, and activity of enzymes that cause the destruction of the extracellular matrix, biofilm formation, and adherence of Porphyromonas gingivalis, and proteolytic activities and coaggregation of periodontopathogens. The above-listed effects suggest that cranberry components, especially those with high molecular weight, could serve as bioactive molecules for the prevention and/or treatment of oral diseases.

Cell-surface hydrophobicity of adherent oral bacteria

Adherent bacteria were released from the surfaces of four freshly extracted teeth by mild sonic oscillation, and screened for cell-surface hydrophobicity on the basis of their ability to adhere to hexadecane. Of the 103 tooth isolates examined, 82 adhered to the test hydrocarbon. Hydrophobic bacteria could similarly be isolated from the stainless steel dental matrix bands following brief incubation in the mouth of a volunteer; 30 of 52 isolates examined adhered to hexadecane. Among those strains which adhered to hexadecane, streptococci were the most frequent type isolated. Various other morphological types were also observed, including cocci, bacilli, coryneforms, and filamentous bacteria. The high overall proportion of hydrophobic bacteria found in this study (72%) suggests that cell-surface hydrophobicity may play a role in adherence of certain oral species to the tooth surface.

Phototoxic Effect of Visible Light on Porphyromonas gingivalis and Fusobacterium nucleatum: An In Vitro Study¶,†

Abstract The antibacterial effect of visible light irradiation combined with photosensitizers has been reported. The objective of this was to test the effect of visible light irradiation without photosensitizers on the viability of oral microorganisms. Strains of Porphyromonas gingivalis, Fusobacterium nucleatum, Streptococcus mutans and Streptococcus faecalis in suspension or grown on agar were exposed to visible light at wavelengths of 400–500 nm. These wavelengths are used to photopolymerize composite resins widely used for dental restoration. Three photocuring light sources, quartz–tungsten–halogen lamp, light-emitting diode and plasma-arc, at power densities between 260 and 1300 mW/cm2 were used for up to 3 min. Bacterial samples were also exposed to a near-infrared diode laser (wavelength, 830 nm), using identical irradiation parameters for comparison. The results show that blue light sources exert a phototoxic effect on P. gingivalis and F. nucleatum. The minimal inhibitory dose for P. gingivalis and F. nucleatum was 16–62 J/cm2, a value significantly lower than that for S. mutans and S. faecalis (159–212 J/cm2). Near-infrared diode laser irradiation did not affect any of the bacteria tested. Our results suggest that visible light sources without exogenous photosensitizers have a phototoxic effect mainly on Gram-negative periodontal pathogens.

Surface Characterization and Biocompatibility of Restorative Resin Containing Nanoparticles

Composite resins that are used to restore hard tissues have several drawbacks including the accumulation of biofilm on teeth and restorations. Recently, quaternary ammonium poly(ethylene imine) (QA-PEI) nanoparticles were developed for additional antibacterial activity of restorative composite resins. QA-PEI nanoparticles were synthesized from cross-linked poly(ethylene imine) that was N-alkylated with octyl halide, followed by quaternary methylation with methyl iodide. QA-PEI particles that were embedded in restorative composite resin at 1% w/w resulted in the complete growth inhibition of Streptococcus mutans. Moreover, the antibacterial activity was retained for at least 3 months. The active substances on the surface of the restorative composite resin that were incorporated with QA-PEI particles were detected by X-ray photoelectron spectroscopy (XPS) and confocal microscopy measurements. The in vitro cytotoxicity tests showed a similar effect on the viability of the cell line that was tested with composites including modified and unmodified dental composite resins. In vivo toxicity studies, which were assessed on Wistar rats by the implantation of modified composite specimens, revealed no inflammation response 1 week after the implantation of restorative composite resin that was embedded with up to 2% w/w QA-PEI.

Mechanism of visible light phototoxicity on Porphyromonas gingivalis and Fusobacterium nucleatum.

Abstract Phototoxicity of visible light laser on the porphyrin-producing bacteria, Porphyromonas gingivalis, in the absence of photosensitizers and under aerobic conditions was shown in previous studies. Recently, we found that the noncoherent visible light sources at wavelengths of 400–500 nm, commonly used in restorative dentistry, induced a phototoxic effect on P. gingivalis, as well as on Fusobacterium nucleatum, and to a lesser extent on the Streptococci sp. To elucidate the mechanism of this phototoxic effect, P. gingivalis and F. nucleatum were exposed to light (1) under aerobic and anaerobic environments and (2) in the presence of scavengers of reactive oxygen species (ROS). Phototoxic effect was not observed when the bacteria were exposed to light under anaerobic conditions. Dimethyl thiourea, a hydroxyl radical scavenger, was effective in reducing phototoxicity (P ≤ 0.05). Other scavengers, such as catalase, superoxide dismutase and ascorbic acid, were less effective when applied separately. These results support the assumption that the phototoxic effect of blue light on the periopathogenic bacteria is oxygen dependent and that hydroxyl radicals play an important role in this process.

Antibacterial Efficacy of a New Chlorhexidine Slow Release Device to Disinfect Dentinal Tubules

Dentinal tubules of 27 cylindrical bovine root specimens were infected with Enterococcus faecalis. In nine specimens, 5% chlorhexidine was placed in a slow-release device (Activ Point) for 7 days, in another nine irrigation with 10 ml of 0.2% chlorhexidine was used, and the remaining nine served as positive control. Powder dentin samples obtained from within the canal lumina using ISO 025 to 033 burs were examined for the presence of vital bacteria by inoculating brain-heart infusion plates and counting colony forming units. Results were analyzed using analysis of variance and covariance with repeated measures. Heavy bacterial infection was observed at the layer close to the lumen in the control specimens, decreasing rapidly from layer to layer up to the deepest layer tested (400-500 microm), which contained several hundred colony forming units. Viable bacteria in each layer of dentin were significantly reduced with chlorhexidine irrigation solution (p < 0.01) and were completely eliminated with the chlorhexidine slow-release device (p < 0.01).