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Surface modifications in the nanoscale regime have shown promising potential in the combat against bacterial adhesion and colonization of surfaces. However, detailed knowledge of how the bacteria-substrate interactions occur is still limited. Herein we have used a gradient in nanostructure density on a surface, realized by immobilizing 40 nm sized silicon dioxide nanoparticles with increasing distance on a glass surface, to systematically study the initial attachment of Staphylococcus epidermidis with or without the presence of human fibrinogen. By using a parallel plate laminar flow chamber, we found a near-linear positive correlation between the adhesion of S. epidermidis with increasing nanoparticle density on unmodified (hydrophilic) nanogradients as well as on gradients where polyethylene glycol was immobilized on the surface in-between nanoparticles. However, if the nanostructured gradient was precoated with human fibrinogen the opposite relationship was observed, although the adsorbed amount of fibrinogen was found to be higher on nanostructured than on smooth surfaces. Our results highlight that even minute changes of the nanotopography on a surface can have profound impact on initial attachment of S. epidermidis to biomaterial surfaces and that the presence of nanostructures strongly hampered the cell's ability to bind to adsorbed fibrinogen, possibly due to changes in the orientation or secondary structure of the fibrinogen molecule upon adsorption.

Surface modifications in the nanoscale regime have shown promising potential in the combat against bacterial adhesion and colonization of surfaces. However, detailed knowledge of how the bacteria-substrate interactions occur is still limited. Herein we have used a gradient in nanostructure density on a surface, realized by immobilizing 40 nm sized silicon dioxide nanoparticles with increasing distance on a glass surface, to systematically study the initial attachment of

Objectives Assess the antibacterial, physical and chemical properties of AH Plus, BioRoot RCS and Pulp Canal Sealer (PCS) in contact with 2% chlorhexidine digluconate (CHX) used as final irrigant prior to root canal obturation. Methods The antimicrobial properties were investigated by direct contact tests for planktonic and biofilm growth of E. faecalis, S. mutans, S.epidermidis and S.aureus in vitro. The setting time, wettability, microhardness and surface roughness were also assessed. The sealers were studied in no contact, 1-minute (short-term) and continuous contact (long-term) with CHX. Chemical characterization of sealers was performed by scanning electron microscopy, X-ray diffraction analysis and Fourier-transform infrared spectroscopy after CHX or saline used as the last irrigant in an ex vivo tooth model and in endo training blocks. Results CHX increased the antibacterial activity of all the sealers investigated against planktonic bacteria and biofilms with PCS exerting the highest antimicrobial activity with and without the presence of CHX. The setting of AH Plus and BioRoot RCS was retarded, while for PCS accelerated in the presence of CHX. AH Plus and PCS were more hydrophilic after contact with CHX, whilst BioRoot RCS was hydrophobic in a time-dependent manner. The microhardness of sealers was compromised and the surface roughness increased after CHX exposure for AH Plus and BioRoot RCS, and decreased for PCS. CHX did not affect the sealers’ chemistry, but PCS that exhibited two extra phases. Significance CHX improved the antibacterial efficacy of endodontic sealers but further evidence is needed to confirm its suitability as a final irrigant prior to root canal obturation.

Introduction The aim of this study was to investigate the antibacterial activity of 4 endodontic sealers against bacteria planktonic grown or in biofilms commonly detected from persistent and secondary endodontic infections. Methods The antibacterial activity of the sealers AH Plus, TotalFill BC sealer, RoekoSeal, and Guttaflow 2 was investigated for planktonic grown and 24-hour-old biofilms of Enterococcus faecalis, Staphylococcus epidermidis, Staphylococcus aureus, and Streptococcus mutans. Results AH Plus had high antibacterial activity toward all species investigated, both planktonic and in biofilms. However, the antibacterial activity was lost after 24 hours. TotalFill BC sealer showed marked antibacterial effect on planktonic bacteria up to 7 days after setting. TotalFill BC sealer had lower antibacterial activity against biofilms of S. aureus and E. faecalis compared with AH Plus when direct contact between the sealer and biofilm was investigated and for all species investigated when a membrane was used to separate the biofilm and sealer. Guttaflow 2 and RoekoSeal had no antibacterial activity against planktonic bacteria or bacteria in biofilms. Conclusions Bacteria in biofilms showed higher susceptibility for AH Plus compared with TotalFill BC sealer during the first 24 hours after setting. Investigating the antibacterial activity of endodontic sealers and materials against bacteria in biofilms is highly important to evaluate the materials' ability to eradicate bacteria from the infected root canal.

Natural deep eutectic solvents (NADES) are a newly discovered group of eutectics which has shown promise as a solvent in antimicrobial photodynamic therapy (aPDT). The purpose of this study was to investigate preparations of an anionic porphyrin, meso-tetra-(4-carboxyphenyl)-porphine (TCPP), solubilised in NADES, with regard to their physicochemical and antibacterial properties. The NADES CS (pH ∼ 0), ChX (pH ∼ 4) and MFG (pH ∼ 1) solubilised TCPP with absorption maximum ∼443 nm and emission maximum ∼678 nm, indicating formation of the TCPP dication. Dilution of TCPP-NADES > 1:1 (water) reduced the physical stability of the preparations. The photostability half-lives of TCPP in methanol, MFG, and CS were ∼9 h, 6.9 h and 3.2 h, respectively. Nanomolar concentrations of TCPP solubilised in diluted MFG combined with ⩽27 J/cm2 blue light increased Gram-positive and Gram-negative bacterial phototoxicity, >99.98% and 96% bacterial reduction, respectively, compared to TCPP in PBS/ethanol under equivalent treatment conditions. TCPP solubilised in diluted CS was toxic to bacteria both in the absence (36–72% reduction) and presence of light. TCPP in CS, and in the CS component citric acid, induced a TCPP-concentration dependent increase in Gram-negative phototoxicity relative to controls, which was most pronounced for TCPP-CS. The mechanism behind the increased toxicity is unknown.

Background Leakage of unpolymerized methacrylate monomers after placement of methacrylate-containing polymeric dental materials leads to human exposure. Based on studies using murine macrophages and LPS from Escherichia coli (E. coli), dental monomers like 2-hydroxyethyl methacrylate (HEMA) are known to inhibit lipopolysaccharide (LPS) induced cytokine release. The aim of this study was to establish a model system with relevance for human oral monomer exposure using exposure to live gram-positive bacteria, and to confirm the HEMA-induced effects on cytokine release in this model. Methods The human THP-1 monocyte cell line was differentiated to macrophages using phorbol 12-myristate 13-acetate (PMA), before exposure to 0.5–2 mM HEMA and live Staphylococcus aureus (S. aureus) in various multiplicity of infections (MOI). Cytokine release and cytotoxicity were determined after (i) 2–24 h pre-exposure to HEMA followed by 2–4 h S. aureus exposure and (ii) 2–4 h simultaneous exposure. The 24 h pre-exposure regime was also tested in primary human airway macrophages and for phagocytosis of S. aureus in THP-1 macrophages. Results HEMA attenuated the cytokine release more strongly in the pre-exposure than combined exposure regime, with a maximal reduction of 95% in the S. aureus-induced cytokine release. A MOI of 0.1 (corresponding to a bacteria-macrophage ratio of 1:10) was determined to be optimal in the THP-1 macrophages as it induced sufficient cytokine release and negligible cytotoxicity. Attenuated release of S. aureus-induced interleukin (IL)-1β after HEMA exposure was confirmed in primary airway macrophages, while HEMA increased the phagocytosis of S. aureus in THP-1 cells. Conclusion The model was successfully established and attenuated bacteria-induced cytokine release after HEMA exposure confirmed.

The lifespan of a resin-based restoration is limited, with the main reason for failure being secondary caries. Biofilm formation at the tooth-material interface is a necessary etiological agent for caries development. Dental materials with antimicrobial properties may reduce formation of biofilm and thus increase the longevity of restorations. This study aimed to investigate the effect of methacrylated chitosan (CH-MA), incorporated into the polymeric network of an experimental dental composite and adhesive, on biofilm growth of Streptococcus mutans and to assess the mechanical properties of the modified materials. The methacrylation of low-molecular-weight chitosan was achieved and biofilm studies confirmed the antibacterial effect of the modified polymer in solution. Methacrylated chitosan was incorporated into an experimental composite and adhesive, and the modified materials reduced the formation of S. mutans biofilm. The incorporation of CH-MA did not alter the bond strength of the adhesives. However, the amount of CH-MA in composite that is required to elicit an antibacterial response challenges the mechanical properties of the material. The hardness and flexural strength of the composite decreased with increasing amounts of CH-MA. However, flexural strength values still met the requirement in the ISO standard.

Streptococcus mitis is a colonizer of the oral cavity and the nasopharynx, and is closely related to Streptococcus pneumoniae. Both species occur in encapsulated and unencapsulated forms, but in S. mitis the role of the capsule in host interactions is mostly unknown. Therefore, the aim of this study was to examine how capsule expression in S. mitis can modulate interactions with the host with relevance for colonization. The S. mitis type strain, as well as two mutants of the type strain, an isogenic capsule deletion mutant, and a capsule switch mutant expressing the serotype 4 capsule of S. pneumoniae TIGR4, were used. Wild-type and capsule deletion strains of S. pneumoniae TIGR4 were included for comparison. We found that capsule production in S. mitis reduced adhesion to oral and lung epithelial cells. Further, exposure of oral epithelial cells to encapsulated S. mitis resulted in higher interleukin-6 and CXCL-8 transcription levels relative to the unencapsulated mutant. Capsule expression in S. mitis increased the sensitivity to human neutrophil peptide 1-3 but reduced the sensitivity to human β-defensin-3 and cathelicidin. This was in contrast with S. pneumoniae in which capsule expression has been generally associated with increased sensitivity to human antimicrobial peptides (AMPs). Collectively, these findings indicate that capsule expression in S. mitis is important in modulating interactions with epithelial cells, and is associated with increased or reduced susceptibility to AMPs depending on the nature of the AMP.

Natural deep eutectic solvents (NADES) are a third class of liquids, separate from water and lipids. Some NADES, especially those containing organic acids, have been suggested to possess antimicrobial properties. Such properties may be advantageous when NADES are used as solvents in e.g. antimicrobial photodynamic therapy. However, to control the toxicity of acid-containing NADES, they must retain their specific qualities upon dilution. Hence, the aims of this study were to investigate the effect of dilution on the acid-containing NADES network, their antimicrobial activity on different planktonic microorganisms, and their influence on phototoxicity when used as solvents for a photosensitiser. Four bacteria and one fungus were exposed to the NADES, CS (citric acid:sucrose) and MFG (malic acid:fructose:glucose) (molar ratios 1:1 and 1:1:1, respectively), at ≤1:200 dilution. Additionally, the antimicrobial properties of the NADES were studied in Escherichia coli in terms of pH and chelating effects. In investigations of phototoxicity, the microorganisms were exposed to the photosensitiser meso-tetra(p-hydroxyphenyl)porphine (THPP; 1nM) dissolved in diluted NADES combined with blue light (27J/cm2). The eutectic network appeared to remain upon dilution ≤1:200. CS (1:200) was less toxic than an equal concentration of citric acid in the Gram-negative bacteria Klebsiella pneumoniae and E. coli (p

This study aimed to investigate dentists' exposure to curing light and to obtain information about the dentists' knowledge on practical use and technical features of their curing lights as well as their safety awareness.A pre-coded questionnaire was sent electronically to all dentists (n=1313) in the Public Dental Service (PDS) in Norway in 2015.The Response rate was 55.8%. The dentists spent on average 57.5% of their working days placing restorations, ranging from 1 to 30 (mean 7.7, SD 3.6) restorations per day. The average length of light curing one normal layer of composite was 27s. The longest individual mean curing time per day was about 100 times higher than that of the lowest. The mean curing time for lamps of the lower reported irradiances was similar to the time representing exceedance of international guidelines for limit values for blue light to the eyes. Almost one-third of the dentists used inadequate eye protection against blue light. The odds of using adequate eye protection were significantly higher among young dentists (p0.01). The majority of the respondents (78.3%) were unaware of the irradiance value of their curing lights, thus rendering the curing time uncertain. More dentists in this group did not perform regular maintenance of their curing lights compared with all respondents (17.1% vs. 3.3%, p0.01).This study revealed considerable variations among Norwegian dentists in the Public Dental Service with respect to performance of light curing of restorations, safety awareness and technical knowledge of the curing light.The questionnaire study identifies specific knowledge gaps among Norwegian dentists with regard to curing lights and use of personal protection. Today's dependence on technology in dentistry necessitates that the operator possesses knowledge of essential technical specifications and safe use of devices and instruments routinely used in dental treatment.

Objectives This study aimed to investigate dentists’ treatment choices concerning “repair or replacement” of defective restorations. Methods A pre-coded questionnaire was sent electronically to all dentists (n = 1313) in the Public Dental Service (PDS) in Norway. Part one: The dentists were asked about age and gender, whether they performed direct restorative therapy/amount of time spent on fillings made per day due to: Primary caries, Repair of restorations or Replacement of restoration/what kind of bonding agents used and pre-treatment of the residual restoration. Part two: The dentists were asked to consider the best treatment for three patient cases with tooth/restoration fractures. Results Response rate was 55.8%, (69.6% females, 30.4% males). Respondent age varied from 25 to 77 years (mean 41.8, SD 12.4). Part one: The dentists spent on average 57.5% of the working day placing restorations, making from 1 to 30 (mean 7.7, SD 3.6) restorations per day. Reasons for treatment were; Primary caries 55.7% (SD 19.1%), repair of restorations 26.7% (SD 14.8%), replacement of fillings 18.2% (SD 11.2%). Two-step etch and rinse (ER), 3-step ER and Self-etch (SE) were used by 48.7%, 24.6% and 26.7% of the respondents, respectively. A silanising agent was used by 7.4%. Part two: Treatment choices: Repair with RC: 89.6% in case one, 86.9% in case two and 54.1% in case three. Young dentists suggested invasive treatment more often than old dentists (>38 years). Conclusions Operative dentistry claims 57.5% of PDS dentists' working day. In addition to primary caries, repair and replacement of restorations accounted for 27% and 18% of the reasons for placing restorations. Clinical significance The idea of “minimal intervention dentistry” seems to have great influence among dentists in PDS (Norway), as they seek to preserve dental hard tissue as much as possible by choosing repair before replacement. No gender differences were observed, but older dentists seem to favour repair compared with the younger dentists.

Aim. The aim of this study was to investigate the antibacterial and antibiofilm properties of low viscosity chitosan onS. epidermidisgrowth and biofilm formation.Methods and Results. The antibacterial and antibiofilm properties were investigated, during both planktonic growth and biofilm formation. This was performed using different concentrations in media and by coating on polystyrene surfaces. In addition, the bactericidal effect was investigated using a modified direct contact test. The results showed that low viscosity chitosan in media had both a bacteriostatic and bactericidal effect on planktonic growth and biofilm formation ofS. epidermidisin a concentration dependent manner. Polystyrene discs coated with chitosan reduced both early biofilm formation (6 h) and late biofilm formation (18 h), as confirmed by scanning electron microscopy. The modified direct contact test showed a bactericidal effect.Conclusion. This study demonstrated that low viscosity chitosan has a bacteriostatic and bactericidal activity againstS. epidermidisand that the activity is dependent on the amount of chitosan added. In addition, low viscosity chitosan reduced biofilm formation both when added to media and when coated on polystyrene surfaces.Significance and Impact of Study. Low viscosity chitosan could be a contribution to new treatment approaches of biofilm-related infections ofS. epidermidis.

The competence-stimulating peptide (CSP) and the sigX -inducing peptide (XIP) are known to induce Streptococcus mutans competence for genetic transformation. For both pheromones, direct identification of the native peptides has not been accomplished. The fact that extracellular XIP activity was recently observed in a chemically defined medium devoid of peptides, as mentioned in an accompanying paper ( K. Desai, L. Mashburn-Warren, M. J. Federle, and D. A. Morrison, J. Bacteriol. 194 :3774–3780, 2012 ), provided ideal conditions for native XIP identification. To search for the XIP identity, culture supernatants were filtered to select for peptides of less than 3 kDa, followed by C 18 extraction. One peptide, not detected in the supernatant of a comS deletion mutant, was identified by tandem mass spectrometry (MS/MS) fragmentation as identical to the ComS C-terminal sequence GLDWWSL. ComS processing did not require Eep, a peptidase involved in processing or import of bacterial small hydrophobic peptides, since eep deletion had no inhibitory effect on XIP production or on synthetic XIP response. We investigated whether extracellular CSP was also produced. A reporter assay for CSP activity detection, as well as MS analysis of supernatants, revealed that CSP was not present at detectable levels. In addition, a mutant with deletion of the CSP-encoding gene comC produced endogenous XIP levels similar to those of a nondeletion mutant. The results indicate that XIP pheromone production is a natural phenomenon that may occur in the absence of natural CSP pheromone activity and that the heptapeptide GLDWWSL is an extracellular processed form of ComS, possibly the active XIP pheromone. This is the first report of direct identification of a ComR/ComS pheromone.

Summary The polysaccharide capsule of Streptococcus pneumoniae is a hallmark for virulence in humans. In its close relative Streptococcus mitis, a common human commensal, analysis of the sequenced genomes of six strains revealed the presence of a putative capsule locus in four of them. We constructed an isogenic S. mitis mutant from the type strain that lacked the 19 open reading frames in the capsule locus (Δcps mutant), using a deletion strategy similar to previous capsule functional studies in S. pneumoniae. Transmission electron microscopy and atomic force microscopy revealed a capsule-like structure in the S. mitis type strain that was absent or reduced in the Δcps mutant. Since S. mitis are predominant oral colonizers of tooth surfaces, we addressed the relevance of the capsule locus for the S. mitis overall surface properties, autoaggregation and biofilm formation. The capsule deletion resulted in a mutant with approximately two-fold increase in hydrophobicity. Binding to the Stains-all cationic dye was reduced by 40%, suggesting a reduction in the overall negative surface charge of the mutant. The mutant exhibited also increased autoaggregation in coaggregation buffer, and up to six-fold increase in biofilm levels. The results suggested that the capsule locus is associated with production of a capsule-like structure in S. mitis and indicated that the S. mitis capsule-like structure may confer surface attributes similar to those associated with the capsule in S. pneumoniae.

The polysaccharide capsule surrounding Streptococcus pneumoniae is essential for virulence. Recently, Streptococcus mitis , a human commensal and a close relative of S. pneumoniae , was also shown to have a capsule. In this study, the S. mitis type strain switched capsule by acquisition of the serotype 4 capsule locus of S. pneumoniae TIGR4, following induction of competence for natural transformation. Comparison of the wild type with the capsule-switching mutant and with a capsule deletion mutant showed that the capsule protected S. mitis against phagocytosis by RAW 264.7 macrophages. This effect was enhanced in the S. mitis strain expressing the S. pneumoniae capsule, which showed, in addition, increased resistance against early clearance in a mouse model of lung infection. Expression of both capsules also favored survival in human blood, and the effect was again more pronounced for the capsule-switching mutant. S. mitis survival in horse blood or in a mouse model of bacteremia was not significantly different between the wild type and the mutant strains. In all models, S. pneumoniae TIGR4 showed higher rates of survival than the S. mitis type strain or the capsule-switching mutant, except in the lung model, in which significant differences between S. pneumoniae TIGR4 and the capsule-switching mutant were not observed. Thus, we identified conditions that showed a protective function for the capsule in S. mitis . Under such conditions, S. mitis resistance to clearance could be enhanced by capsule switching to serotype 4, but it was enhanced to levels lower than those for the virulent strain S. pneumoniae TIGR4.