Developing biocompatible silver nanoparticles using epigallocatechin gallate for dental use

Developing a novel antibacterial copper tetraamine fluoride

OBJECTIVE

To develop a novel and biocompatible copper tetraamine fluoride (CTF) with antibacterial and nondiscolouring properties.

METHOD

This study used copper fluoride and ammonia solution to develop CTF solution. The CTF was characterized by X-ray photoelectron spectroscopy (XPS). Cytotoxicity was evaluated by stem cells from human exfoliated deciduous teeth (SHED) and human gingival fibroblasts (HGF-1). The fluoride concentration was determined using ion-selective electrode. The alkalinity was measured by a pH electrode. The human dentine blocks were treated with CTF and then incubated with Streptococcus mutans to evaluate the antimicrobial and discolouring effects. The silver diamine fluoride (SDF) was employed as the positive control, and water was the negative control. The colony-forming units (CFUs) and confocal laser scanning microscopy (CLSM) were used to examine the kinetics and viability of the biofilm. The discolouring property on dentine was assessed by spectrophotometry. One-way analysis of variance with the Bonferroni post hoc test was performed to assess and compare the data.

RESULTS

XPS confirmed synthesis of CTF solution. The half-maximal inhibitory concentration of CTF on SHED and HGF-1 was 195±16 ppm and 137±11 ppm. The fluoride concentration was 121,000±5,000 ppm. The pH value was 9. Log10 CFU of the CTF, SDF and water group were 5.0 ± 0.2, 4.9 ± 0.1 and 7.4 ± 0.1 (p < 0.001, CTF, SDFWater). Spectrophotometry showed that the ΔE of the CTF, SDF and water group were 5 ± 2, 6 ± 3 and 45±2 (p < 0.001, CTF, Water

CONCLUSION

This study developed an alkaline 58% CTF solution, which is biocompatible, antibacterial and non-discolouring.

CLINICAL SIGNIFICANCE

If CTF is successfully translated into clinical care, CTF can be a simple and affordable anti-caries agent for clinicians to prevent dental caries.

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Key Words

• Antibacterial
• Caries
• Copper
• Dentine
• Fluoride

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MESH Headings

• Humans
• Anti-Bacterial Agents/pharmacology
• Streptococcus mutans/drug effects
• Fibroblasts/drug effects
• Tooth, Deciduous/drug effects
• Hydrogen-Ion Concentration
• Biofilms/drug effects
• Quaternary Ammonium Compounds/pharmacology
• Quaternary Ammonium Compounds/chemistry
• Copper/pharmacology
• Copper/chemistry
• Gingiva/drug effects
• Gingiva/cytology
• Dentin/drug effects
• Photoelectron Spectroscopy
• Stem Cells/drug effects
• Silver Compounds/pharmacology
• Microscopy, Confocal
• Biocompatible Materials/pharmacology
• Fluorides, Topical/pharmacology
• Fluorides/pharmacology
• Ion-Selective Electrodes
• Cariostatic Agents/pharmacology
• Cariostatic Agents/chemistry
• Materials Testing
• Microbial Sensitivity Tests
• Cell Survival/drug effects

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Affiliation(s)

Veena Wenqing Xu Faculty of Dentistry, University of Hong Kong, Hong Kong, China
Iris Xiaoxue Yin Faculty of Dentistry, University of Hong Kong, Hong Kong, China
John Yun Niu Faculty of Dentistry, University of Hong Kong, Hong Kong, China
Ollie Yiru Yu Faculty of Dentistry, University of Hong Kong, Hong Kong, China
Mohammed Zahedul Islam Nizami Faculty of Dentistry, University of Hong Kong, Hong Kong, China; Department of Mineralized Tissue Biology and Bioengineering, The Forsyth Institute, Cambridge, MA, USA.
Chun Hung Chu Faculty of Dentistry, University of Hong Kong, Hong Kong, China.

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The anti-caries effects of copper tetraamine fluoride on enamel: An in vitro study

OBJECTIVE

To investigate the antibacterial, remineralising, and discolouring effects of copper tetraamine fluoride (CTF) on artificial enamel caries.

METHOD

Human enamel blocks with artificial caries were treated with CTF, silver diamine fluoride (SDF, positive control) and water (negative control) before being challenged with Streptococcus mutans. The morphology, viability, and growth kinetics of biofilm were evaluated using scanning electron microscopy (SEM), confocal laser scanning microscopy (CLSM), and colony-forming unit (CFU) counting. The lesion depths, mineral loss, micro-hardness, and crystal characteristics were assessed using micro-computed tomography, Knoop Hardness Tester, and X-ray diffraction (XRD), respectively. The discolouring property was assessed by spectrophotometry.

RESULTS

SEM showed that bacteria completely covered the enamel surface treated with water, but not the enamel surface treated with CTF and SDF. CLSM showed dead-to-live ratio of biofilm treated with CTF, SDF and water were 0.8 ± 0.1, 0.9 ± 0.2 and 0.5 ± 0.1 (p < 0.001, CTF, SDF>Water). Log10 CFU values of biofilm treated with CTF, SDF and water were 7.7 ± 0.2, 7.7 ± 0.1 and 8.1 ± 0.1 (p < 0.001, CTF, SDFWater). XRD revealed well-crystallised hydroxyapatite in enamel treated with CTF and SDF, but not water. Spectrophotometry showed ΔE values of the CTF, SDF and water groups were 5 ± 3, 54 ± 6 and 6 ± 2 (p < 0.001, CTF, water

CONCLUSION

CTF inhibited Streptococcus mutans biofilm and remineralised artificial enamel caries without discolouration.

CLINICAL SIGNIFICANCE

If CTF is successfully translated into clinical use, it can be a simple agent for clinicians to arrest enamel caries.

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Key Words

• Antibacterial
• Caries
• Enamel
• Fluoride
• Remineralization

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MESH Headings Collapse

Grants Collapse

Affiliation(s)

Veena Wenqing Xu Faculty of Dentistry, University of Hong Kong, Hong Kong, China
Iris Xiaoxue Yin Faculty of Dentistry, University of Hong Kong, Hong Kong, China
John Yun Niu Faculty of Dentistry, University of Hong Kong, Hong Kong, China
Ollie Yiru Yu Faculty of Dentistry, University of Hong Kong, Hong Kong, China
Mohammed Zahedul Islam Nizami Faculty of Dentistry, University of Hong Kong, Hong Kong, China; Department of Mineralized Tissue Biology and Bioengineering, The ADA Forsyth Institute, Cambridge, MA, USA.
Chun Hung Chu Faculty of Dentistry, University of Hong Kong, Hong Kong, China.

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Synthesis and Application of Silver Nanoparticles for Caries Management: A Review

Silver nanoparticles have unique physical, chemical, and biological properties that make them attractive for medical applications. They have gained attention in dentistry for their potential use in caries management. This study reviews the different synthesis methods of silver nanoparticles and the application of them for caries management. Silver nanoparticles are tiny silver and are typically less than 100 nanometres in size. They have a high surface area-to-volume ratio, making them highly reactive and allowing them to interact with bacteria and other materials at the molecular level. Silver nanoparticles have low toxicity and biocompatibility. Researchers have employed various methods to synthesise silver nanoparticles, including chemical, physical, and biological methods. By controlling the process, silver nanoparticles have defined sizes, shapes, and surface properties for wide use. Silver nanoparticles exhibit strong antibacterial properties, capable of inhibiting a broad range of bacteria, including antibiotic-resistant strains. They inhibit the growth of cariogenic bacteria, such as Streptococcus mutans. They can disrupt bacterial cell membranes, interfere with enzyme activity, and inhibit bacterial replication. Silver nanoparticles can inhibit biofilm formation, reducing the risk of caries development. Additionally, nano silver fluoride prevents dental caries by promoting tooth remineralisation. They can interact with the tooth structure and enhance the deposition of hydroxyapatite, aiding in repairing early-stage carious lesions. Silver nanoparticles can also be incorporated into dental restorative materials such as composite resins and glass ionomer cements. The incorporation can enhance the material's antibacterial properties, reducing the risk of secondary caries and improving the longevity of the restoration.

Harnessing the power of Neobacillus niacini AUMC-B524 for silver oxide nanoparticle synthesis: optimization, characterization, and bioactivity exploration

BACKGROUND

Biotechnology provides a cost-effective way to produce nanomaterials such as silver oxide nanoparticles (Ag2ONPs), which have emerged as versatile entities with diverse applications. This study investigated the ability of endophytic bacteria to biosynthesize Ag2ONPs.

RESULTS

A novel endophytic bacterial strain, Neobacillus niacini AUMC-B524, was isolated from Lycium shawii Roem. & Schult leaves and used to synthesize Ag2ONPS extracellularly. Plackett-Burman design and response surface approach was carried out to optimize the biosynthesis of Ag2ONPs (Bio-Ag2ONPs). Comprehensive characterization techniques, including UV-vis spectral analysis, Fourier transform infrared spectroscopy, transmission electron microscopy, X-ray diffraction, dynamic light scattering analysis, Raman microscopy, and energy dispersive X-ray analysis, confirmed the precise composition of the Ag2ONPS. Bio-Ag2ONPs were effective against multidrug-resistant wound pathogens, with minimum inhibitory concentrations (1-25 µg mL-1). Notably, Bio-Ag2ONPs demonstrated no cytotoxic effects on human skin fibroblasts (HSF) in vitro, while effectively suppressing the proliferation of human epidermoid skin carcinoma (A-431) cells, inducing apoptosis and modulating the key apoptotic genes including Bcl-2 associated X protein (Bax), B-cell lymphoma 2 (Bcl-2), Caspase-3 (Cas-3), and guardian of the genome (P53).

CONCLUSIONS

These findings highlight the therapeutic potential of Bio-Ag2ONPs synthesized by endophytic N. niacini AUMC-B524, underscoring their antibacterial efficacy, anticancer activity, and biocompatibility, paving the way for novel therapeutic strategies.

Preparation and Characterization of Oxide Nanotubes on Titanium Surface for Use in Controlled Drug Release Systems

Preventing or treating infections at implantation sites where the risk of bacterial contamination is high requires the development of intelligent drug delivery systems. The objective of this work was to develop a production method and characterization of fourth-generation oxide nanotubes on titanium grade 4 surface as a potential drug carrier. This study focused on the anodizing process; physico-chemical characterization using FE-SEM, EDS, and FTIR; in vitro corrosion resistance in an artificial saliva solution; and determining the drug release kinetics of gentamicin sulfate using UV-VIS. The anodizing process was optimized to produce fourth-generation oxide nanotubes in a fluoride-free electrolyte, ensuring rapid growth and lack of order. Results showed that the length of the oxide nanotubes was inversely proportional to the anodizing voltage, with longer nanotubes formed at lower voltages. The nanotubes were shown to have a honeycomb structure with silver particles co-deposited on the surface for antibacterial properties and were capable of carrying and releasing the antibiotic gentamicin sulfate in a controlled manner, following Fick's first law of diffusion. The corrosion resistance study demonstrates that the oxide nanotubes enhance the corrosion resistance of the titanium surface. The oxide nanotubes show promise in enhancing osseointegration and reducing post-implantation complications.

Evaluating antimicrobial activity and cytotoxicity of silver nanoparticles incorporated into reinforced zinc oxide eugenol: an in vitro study

PURPOSE

This study aimed to evaluate the antibacterial and cytotoxic effects of reinforced zinc oxide-eugenol (rZOE) incorporated with different concentrations of silver nanoparticles (AgNPs).

METHODS

The pastes of rZOE alone or mixed with AgNPs at concentrations of 1%, 2%, and 5% of weight were prepared. In vitro antimicrobial activity of prepared materials against Streptococcus (S.) mutans and Lactobacillus (L.) acidophilus were evaluated after 2, 4, and 6 h of contact times using direct contact test (DCT) and also following 24 h incubation by well-diffusion test (WDT). The cytotoxicity of the tested materials on human dental pulp stem cells was also determined by MTT assay.

RESULTS

The DCT demonstrated that the time-dependent reductions of the colony numbers of both bacteria by three different concentrations of AgNPs incorporated into rZOE were equal but steeper than the rZOE alone (P < 0.05). The increases in growth inhibition zones of S. mutans and L. acidophilus were associated with the increasing concentration of AgNPs mixed with rZOE in the WDT; however, statistical analysis did not show any significant differences (P = 0.092). The MTT assay revealed a significantly lower percentage of cell viability after 1 day of culture only with the rZOE + AgNP5% in comparison to the rZOE alone (P = 0.011) and the control medium (P = 0.001).

CONCLUSION

Since the antimicrobial activities of three different concentrations of AgNPs incorporated into rZOE were equal and AgNPs had lower toxicity at lower concentrations, using AgNPs at 1% concentration is suggested to be mixed with rZOE.

Green synthesis of chitosan- and fluoride-functionalized silver nanoparticles using Camellia sinensis: Characterization and dental applications

The development of new biocompatible and eco-friendly materials is essential for the future of dental practice, especially for the management of dental caries. In this study, a novel and simple method was applied for the green synthesis of silver nanoparticles (AgNPs) from the aqueous extract of Camellia sinensis (WT) and functionalized with chitosan (CHS) and NaF. The effects of WT_AgNPs application on demineralized dentin were evaluated for potential dental applications. The WT_AgNPs showed molecular groups related to organic compounds, potentially acting as reducing and capping agents. All AgNPs presented spherical shapes with crystal sizes of approximately 20 nm. Forty human molars were assigned to control: sound (SD) and demineralised dentine (DD), and experimental groups: WT_AgNPs, WT_AgNPs_NaF, and WT_AgNPs_CHS. Then, the NPs were applied to DD to evaluate the chemical, crystallographic, and microstructural characteristics of treated-dentine. In addition, a three-point bending test was employed to assess mechanical response. The application of WT_AgNPs indicated a higher mineralisation degree and crystallites sizes of hydroxyapatite than the DD group. SEM images showed that WT_AgNPs presented different degrees of aggregation and distribution patterns. The dentine flexural strength was significantly increased in all WT_AgNPs. The application of WT_AgNPs demonstrated remineralising and strengthening potential on demineralised dentine.

The effect of silver nanoparticles in addition to sodium fluoride on remineralization of artificial root dentin caries

BACKGROUND

Silver nanoparticle was developed to overcome the drawback of silver diamine fluoride. However, evidence is limited, especially in root caries. The aim of this study was to evaluate the remineralization effect of silver nanoparticles on root caries.

MATERIALS AND METHODS

Fifty-five root human dentin slices size 5 × 5 mm2 from patients aged over 60 years old were immersed in demineralized solution to create artificial caries. Specimens were allocated into five groups according to the remineralizing agents: silver diamine fluoride (SDF), silver nanoparticles solution (AgNPs), silver nanoparticle solution followed by sodium fluoride varnish (AgNPs+NaF), sodium fluoride varnish (NaF), and tap water. After 8 days of pH-cycling challenge, the microhardness test, lesion depth evaluation, dentin surface morphology, and elemental analysis were performed. Data was analysed using F-test One-way ANOVA followed by Tukey's post hoc test and paired T-test.

RESULTS

All test groups demonstrated a significantly higher microhardness value and lower lesion depth compared with the control group. AgNPs+NaF and NaF-treated groups showed lower efficacy than SDF. Crystal precipitation was presented in all groups composed of silver.

CONCLUSION

Addition of fluoride varnish did not benefit for silver nanoparticles in preventing further demineralization. SDF provides the highest effectiveness in elderly root carious dentin.

Pure Epigallocatechin-3-gallate-Assisted Green Synthesis of Highly Stable Titanium Dioxide Nanoparticles

Nanoparticles (NPs) are conventionally produced by using physical and chemical methods that are no longer in alignment with current society's demand for a low environmental impact. Accordingly, green synthesis approaches are considered a potential alternative due to the plant extracts that substitute some of the hazardous reagents. The general mechanism is based on the reducing power of natural products that allows the formation of NPs from a precursor solution. In this context, our study proposes a simple, innovative, and reproducible green approach for the synthesis of titanium dioxide (TiO2 NPs) that uses, for the first time, the major component of green tea (Camellia sinensis)-epigallocatechin-3-gallate (EGCG), a non-toxic, dietary, accessible, and bioactive molecule. The influence of EGCG on the formation of TiO2 NPs was analyzed by comparing the physicochemical characteristics of green synthesized NPs with the chemically obtained ones. The synthesis of bare TiO2 NPs was performed by hydrolysis of titanium isopropoxide in distilled water, and green TiO2 NPs were obtained in the same conditions, but in the presence of a 1 mM EGCG aqueous solution. The formation of TiO2 NPs was confirmed by UV-VIS and FTIR spectroscopy. SEM micrographs showed spherical particles with relatively low diameters. Our findings also revealed that green synthesized NPs were more stable in colloids than the chemically synthesized ones. However, the phytocompound negatively influenced the formation of a crystalline structure in the green synthesized TiO2 NPs. Furthermore, the synthesis of EGCG-TiO2 NPs could become a versatile choice for applications extending beyond photocatalysis, including promising prospects in the biomedical field.

Bactericidal Activity of Silver Nanoparticles on Oral Biofilms Related to Patients with and without Periodontal Disease

BACKGROUND AND OBJECTIVES

Periodontal disease (PD) is a multifactorial oral disease regularly caused by bacterial biofilms. Silver nanoparticles (AgNP) have offered good antimicrobial activity; moreover, there is no available scientific information related to their antimicrobial effects in biofilms from patients with PD. This study reports the bactericidal activity of AgNP against oral biofilms related to PD.

MATERIALS AND METHODS

AgNP of two average particle sizes were prepared and characterized. Sixty biofilms were collected from patients with (30 subjects) and without PD (30 subjects). Minimal inhibitory concentrations of AgNP were calculated and the distribution of bacterial species was defined by polymerase chain reaction.

RESULTS

Well-dispersed sizes of AgNP were obtained (5.4 ± 1.3 and 17.5 ± 3.4 nm) with an adequate electrical stability (-38.2 ± 5.8 and -32.6 ± 5.4 mV, respectively). AgNP showed antimicrobial activities for all oral samples; however, the smaller AgNP had significantly the most increased bactericidal effects (71.7 ± 39.1 µg/mL). The most resistant bacteria were found in biofilms from PD subjects (p < 0.05). P. gingivalis, T. denticola, and T. forsythia were present in all PD biofilms (100%).

CONCLUSIONS

The AgNP showed efficient bactericidal properties as an alternative therapy for the control or progression of PD.

Biogenic Synthesis of Multifunctional Silver Oxide Nanoparticles (Ag2ONPs) Using Parieteria alsinaefolia Delile Aqueous Extract and Assessment of Their Diverse Biological Applications

Green nanotechnology has made the synthesis of nanoparticles a possible approach. Nanotechnology has a significant impact on several scientific domains and has diverse applications in different commercial areas. The current study aimed to develop a novel and green approach for the biosynthesis of silver oxide nanoparticles (Ag₂ONPs) utilizing Parieteria alsinaefolia leaves extract as a reducing, stabilizing and capping agent. The change in color of the reaction mixture from light brown to reddish black determines the synthesis of Ag₂ONPs. Further, different techniques were used to confirm the synthesis of Ag₂ONPs, including UV-Visible spectroscopy, Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscope (SEM), Energy-dispersive X-ray spectroscopy (EDX), zeta potential and dynamic light scattering (DLS) analyses. The Scherrer equation determined a mean crystallite size of ~22.23 nm for Ag₂ONPs. Additionally, different in vitro biological activities have been investigated and determined significant therapeutic potentials. Radical scavenging DPPH assay (79.4%), reducing power assay (62.68 ± 1.77%) and total antioxidant capacity (87.5 ± 4.8%) were evaluated to assess the antioxidative potential of Ag₂ONPs. The disc diffusion method was adopted to evaluate the antibacterial and antifungal potentials of Ag₂ONPs using different concentrations (125-1000 μg/mL). Moreover, the brine shrimp cytotoxicity assay was investigated and the LC₅₀ value was calculated as 2.21 μg/mL. The biocompatibility assay using red blood cells (<200 μg/mL) confirmed the biosafe and biocompatible nature of Ag₂ONPs. Alpha-amylase inhibition assay was performed and reported 66% inhibition. In conclusion, currently synthesized Ag₂ONPs have exhibited strong biological potential and proved as an attractive eco-friendly candidate. In the future, this preliminary research work will be a helpful source and will open new avenues in diverse fields, including the pharmaceutical, biomedical and pharmacological sectors.

Antibacterial effect and impact on caries activity of nanosilver fluoride and silver diamine fluoride in dentin caries of primary teeth: a randomized controlled clinical trial

BACKGROUND

The use of silver diamine fluoride (SDF) in caries treatment in children has increased despite the disadvantage of causing tooth discoloration. Nanosilver fluoride (NSF) is a possible alternative. This study aimed to assess the antibacterial effect of NSF and SDF and their impact on the activity of dentin caries in primary teeth.

METHODS

Synthesis and characterization of the physical and biological properties of NSF were conducted. Fifty children aged 4-6 years with dentin caries (active caries corresponding to ICDAS code 5) in deciduous teeth were randomly assigned to treatment by NSF or SDF. Baseline assessment of Streptococcus mutans (S. mutans) and lactobacilli counts as CFU/mL in caries lesions was done, followed by the application of the agents. After one month, microbiological samples were recollected, and lesion activity was reassessed. Groups were compared using Mann-Whitney and Chi-Square tests, while intragroup comparisons were done using Wilcoxon and McNemar tests. Multilevel logistic regression analysis was used to assess the effect of different variables on the outcomes.

RESULTS

There were 130 teeth in 50 children; mean ± SD age = 4.75 ± 0.76 years, 63% were posterior teeth. At the one-month follow-up appointment, both groups showed a significant decrease from baseline bacterial counts. There was a significant difference in the reduction of S. mutans between NSF and SDF (21.3% and 10.5%, respectively, p = 0.002), while not in lactobacilli (13.9% and 6.0%, respectively, p = 0.094). In both groups, there was a significant reduction in the number of active caries from baseline (p < 0.0001) with no significant difference between groups (percentage inactive = 64.4% and 63.4%, p = 0.903). Multilevel regression revealed non-significant differences in S. mutans and lactobacilli counts (AOR 1.281, p = 0.737 and 1.888, p = 0.341, respectively), and in the number of inactive lesions (AOR 1.355, p = 0.731) between groups.

CONCLUSION

The short-term antibacterial efficacy of NSF was similar to that of SDF. In both groups there was a significant reduction of S. mutans and lactobacilli counts in active dentin caries, and two-thirds of the lesions became inactive with no differences between the two interventions. Further research is needed to investigate the long-term efficacy of NSF and its suitability for clinical use in caries management.

TRIAL REGISTRATION

This trial was prospectively registered on the clinicaltrials.gov registry with ID: NCT05221749 on 03/02/2022.

The potency of herbal extracts and its green synthesized nanoparticle formulation as antibacterial agents against Streptococcus mutans associated biofilms

This study aims to determine the effects of the extracts of Streblus asper, Cymbopogon citratus, Syzygium aromaticum and its formulation of green synthesized silver nanoparticle (AgNPs) on Streptococcus mutans growth and biofilm formation. The ethanolic extracts of S. asper, C. citratus, S. aromaticum, and a mix of the three herbs demonstrated antibacterial activity against S. mutans isolates by reducing bacterial biofilm formation and decreasing bacterial cell surface hydrophobicity. The formulated AgNPs from the ethanolic extracts could enhance the antibacterial activities of the plant extracts. Molecular docking found the best interaction between luteolin isolated from C. citratus and glucosyltransferase protein (GtfB), assuming the promising anti-biofilm activity. The scanning electron microscopy revealed morphological changes in the biofilm structure and a significant decrease in the biofilm area of the AgNPs treated. The study suggested that the extracts and its application could be used as natural alternative agents with multi-action against S. mutans infections.

Effects of the green tea catechin epigallocatechin-3-gallate on Streptococcus mutans planktonic cultures and biofilms: systematic literature review of in vitro studies

This study aimed at performing a systematic review of the literature on the effects of epigallocatechin-3-gallate (EGCG) on Streptococcus mutans planktonic cultures and biofilms. The selected references demonstrated that EGCG suppresses S. mutans acid production by inhibiting the activity of enzymes such as lactate dehydrogenase and FIF0-ATPase. Regarding virulence factors, one study reported a reduction in soluble and insoluble polysaccharide synthesis, another demonstrated that EGCG inhibited GTase activity, and another showed effects of EGCG on the expression of gtf B, C, and D. The effects of EGCG on S. mutans biofilms were reported only by 2 of the selected studies. Moreover, high variability in effective concentrations and microbial assessment methods were observed. The literature suggests that EGCG has effects against S. mutans planktonic cells viability and virulence factors. However, the literature lacks studies with appropriate biofilm models to evaluate the precise effectiveness of EGCG against S. mutans biofilms.

Silver nanoparticles associated with a polyphosphate and fluoride enhance the prevention of enamel demineralization and impact on dual-biofilm adhesion

OBJECTIVES

The aim of this study were to produce a multifunctional nanocomposite combining silver nanoaparticles (Ag), sodium trimetaphosphate (TMP) and fluoride (F), to investigate its effect on dental enamel demineralization and on biofilms of Streptococcus mutans and Candida albicans.

METHODS

Bovine enamel blocks were submitted to five pH cycles and treated 2x/day with 100ppm F, 225ppm F, 100ppm F+0.2%TMP or 100ppm F+0.2%TMP+10% Ag (100F/TMP/Ag). Next, surface hardness loss (%SH), integrated loss of subsurface hardness (ΔKHN), enamel fluoride (F) and calcium (Ca) concentration were determined. Biofilms from single and dual species of S. mutans and C. albicans were treated with 100F/TMP/Ag, Ag or chlorhexidine gluconate for 24h. The antibiofilm effect was evaluated by colony-forming unit counting and Scanning Electron Microscopy.

RESULTS

The nanocomposite reduced 43.0% of %SH and was similar with samples treated with 225F, 100F/TMP and 100/TMP/Ag. The attribute of F and/or TMP in reducing ΔKHN in 5-20 μm was not affected by the addiction of Ag (110F = 225F = 100F/TMP = 100F/TMP/Ag > Negative Control). Further, 100F/TMP/Ag strongly reduced viable cells of S. mutans in dual biofilms (∼5 log₁₀cm²) and structurally affected the biofilms.

CONCLUSION

The 100F/TMP/F promoted a protective effect against enamel demineralization and was able to significantly inhibit the growth of biofilms of S. mutans and C. albicans.

CLINICAL SIGNIFICANCE

The focus on prevention and non-invasive dental treatment is the most effective and least costly way to improve the population's oral health conditions. We present a nanocomposite for a multiple approach in prevention of caries.

Multidrug-Resistant Bacterial Pathogens and Public Health: The Antimicrobial Effect of Cyanobacterial-Biosynthesized Silver Nanoparticles

Background: Cyanobacteria are considered as green nano-factories. Manipulation of the size of biogenic silver nanoparticles is needed to produce particles that suit the different applications such as the use as antibacterial agents. The present study attempts to manipulate the size of biosynthesized silver nanoparticles produced by cyanobacteria and to test the different-sized nanoparticles against pathogenic clinical bacteria. Methods: Cyanothece-like. coccoid unicellular cyanobacterium was tested for its ability to biosynthesize nanosilver particles of different sizes. A stock solution of silver nitrate was prepared from which three different concentrations were added to cyanobacterial culture. UV-visible spectroscopy and FTIR were conducted to characterize the silver nanoparticles produced in the cell free filtrate. Dynamic Light Scattering (DLS) was performed to determine the size of the nanoparticles produced at each concentration. The antimicrobial bioassays were conducted on broad host methicillin-resistant Staphylococcus aureus (MRSA), and Streptococcus sp., was conducted to detect the nanoparticle size that was most efficient as an antimicrobial agent. Results. The UV-Visible spectra showed excellent congruence of the plasmon peak characteristic of nanosilver at 450 nm for all three different concentrations, varying peak heights were recorded according to the concentration used. The FTIR of the three solutions revealed the absence of characteristic functional groups in the solution. All three concentrations showed spectra at 1636 and 2050–2290 nm indicating uniformity of composition. Moreover, DLS analysis revealed that the silver nanoparticles produced with lowest concentration of precursor AgNO₃ had smallest size followed by those resulting from the higher precursor concentration. The nanoparticles resulting from highest concentration of precursor AgNO₃ were the biggest in size and tending to agglomerate when their size was above 100 nm. The three types of differently-sized silver nanoparticles were used against two bacterial pathogenic strains with broad host range; MRSA-(Methicillin-resistant Staphylococcus aureus) and Streptococcus sp. The three types of nanoparticles showed antimicrobial effects with the smallest nanoparticles being the most efficient in inhibiting bacterial growth. Discussion: Nanosilver particles biosynthesized by Cyanothece-like cyanobacterium can serve as antibacterial agent against pathogens including multi-drug resistant strains. The most appropriate nanoparticle size for efficient antimicrobial activity had to be identified. Hence, size-manipulation experiment was conducted to find the most effective size of nanosilver particles. This size manipulation was achieved by controlling the amount of starting precursor. Excessive precursor material resulted in the agglomeration of the silver nanoparticles to a size greater than 100 nm. Thereby decreasing their ability to penetrate into the inner vicinity of microbial cells and consequently decreasing their antibacterial potency. Conclusion: Antibacterial nanosilver particles can be biosynthesized and their size manipulated by green synthesis. The use of biogenic nanosilver particles as small as possible is recommended to obtain effective antibacterial agents.

The Application of Small Molecules to the Control of Typical Species Associated With Oral Infectious Diseases

Oral microbial dysbiosis is the major causative factor for common oral infectious diseases including dental caries and periodontal diseases. Interventions that can lessen the microbial virulence and reconstitute microbial ecology have drawn increasing attention in the development of novel therapeutics for oral diseases. Antimicrobial small molecules are a series of natural or synthetic bioactive compounds that have shown inhibitory effect on oral microbiota associated with oral infectious diseases. Novel small molecules, which can either selectively inhibit keystone microbes that drive dysbiosis of oral microbiota or inhibit the key virulence of the microbial community without necessarily killing the microbes, are promising for the ecological management of oral diseases. Here we discussed the research progress in the development of antimicrobial small molecules and delivery systems, with a particular focus on their antimicrobial activity against typical species associated with oral infectious diseases and the underlying mechanisms.

Synergistic effects of silver nanoparticles and cisplatin in combating inflammation and hyperplasia of airway stents

Anti-inflammatory and antihyperplasia activities are essential requirements for the successful use of airway stents. In this work, silver nanoparticles (AgNPs) and cisplatin (DDP) were combined in a synergistic modification strategy to improve the surface function of airway stents. Using polycaprolactone (PCL) as a drug carrier, a dual-functional PCL-AgNPs-DDP fiber film-coated airway stent was fabricated by electrospinning. The physicochemical and biological properties of the obtained fiber films were examined. The ATR-FTIR, XPS, SEM-EDS and TEM results suggested that AgNPs and DDP could be successfully immobilized onto the airway stent surface. The drug release and surface degradation results revealed that AgNPs and DDP can undergo sustained release from films for 30 d, and the weight loss was approximately 50% after 35 d. In addition, the dual-functional fiber film suppressed human embryonic lung fibroblast growth and exhibited excellent antibacterial activity against Staphylococcus aureus, Pseudomonas aeruginosa and Candida albicans. Furthermore, the effectiveness of the dual-functional fiber film-coated airway stent was evaluated by application to the trachea of New Zealand rabbits. The in vivo results indicated that PCL-AgNPs-DDP fiber film-coated airway stent can significantly inhibit granulation tissue formation and collagen deposition, reduced the expression of IL-8, TNF-α, IL-1α, PCNA, α-SMA and CD68, and ultimately achieved anti-inflammatory and antihyperplasia effects. Hence, this study provides a dual-functional surface-coated airway stent to address the clinical complications associated with respiratory tract inflammation and granulation tissue hyperplasia, thus inhibiting tracheal stenosis.

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This study provides a dual-functional PCL-AgNPs-DDP nanofiber film-coated airway stent.

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The airway stent processes antibacterial activity and suppress CCC-HPF-1 growth.

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The stent inhibits tracheal stenosis by antiinflammatory and antihyperplasia treatment.

Solar radiation-induced synthesis of bacterial cellulose/silver nanoparticles (BC/AgNPs) composite using BC as reducing and capping agent

In the present work, a simple, novel, and ecofriendly method for synthesis of silver nanoparticles (AgNPs) and BC/AgNP composite using bacterial cellulose (BC) nanofibers soaked in AgNO₃ solution under induction action of solar radiation. The photochemical reduction of silver Ag + ions into silver nanoparticles (Ag^o) was confirmed using UV visible spectra; the surface plasmon resonance of synthesized AgNPs was localized around 425 nm. The mean diameter of AgNPs obtained by DLS analysis was 52.0 nm with a zeta potential value of - 9.98 mV. TEM images showed a spherical shape of AgNPs. The formation of BC/AgNP composite was confirmed by FESEM, EDX, FTIR, and XRD analysis. FESEM images for BC showed the 3D structures of BC nanofibers and the deposited AgNPs in the BC crystalline nanofibers. XRD measurements revealed the high crystallinity of BC and BC/AgNP composite with crystal sizes of 5.13 and 5.6 nm, respectively. BC/AgNP composite and AgNPs exhibited strong antibacterial activity against both Gram-positive and Gram-negative bacteria. The present work introduces a facile green approach for BC/AgNP composite synthesis and its utility as potential food packaging and wound dressings, as well as sunlight indicator application.

Efficacy of the dual-action GA-KR12 peptide for remineralising initial enamel caries: an in vitro study

OBJECTIVE

To investigate the antibiofilm and remineralising effects of the dual-action peptide GA-KR12 on artificial enamel caries.

MATERIALS AND METHODS

Enamel blocks with artificial caries were treated with sterilised deionised water as control or GA-KR12. The blocks underwent biochemical cycling with Streptococcus mutans for 3 weeks. The architecture, viability, and growth kinetics of the biofilm were determined, respectively, by scanning electron microscopy (SEM), confocal laser scanning microscopy, and quantitative (culture colony-forming units, CFUs). The mineral loss, calcium-to-phosphorus ratio, surface morphology, and crystal characteristics of the enamel surface were determined, respectively, using micro-computed tomography, energy dispersive spectroscopy, SEM, and X-ray diffraction (XRD).

RESULTS

SEM showed confluent growth of S. mutans in the control group but not in the GA-KR12-treated group. The dead-to-live ratios of the control and GA-KR12-treated groups were 0.42 ± 0.05 and 0.81 ± 0.08, respectively (p < 0.001). The log CFUs of the control and GA-KR12-treated groups were 8.15 ± 0.32 and 6.70 ± 0.49, respectively (p < 0.001). The mineral losses of the control and GA-KR12-treated groups were 1.39 ± 0.09 gcm^-3 and 1.19 ± 0.05 gcm^-3, respectively (p < 0.001). The calcium-to-phosphorus molar ratios of the control and GA-KR12-treated groups were 1.47 ± 0.03 and 1.57 ± 0.02, respectively (p < 0.001). A uniformly remineralised prismatic pattern on enamel blocks was observed in the GA-KR12-treated but not in the control group. The hydroxyapatite in the GA-KR12-treated group was better crystallised than that in the control group.

CONCLUSION

The dual-action peptide GA-KR12 inhibited the growth of S. mutans biofilm and promoted the remineralisation of enamel caries.

CLINICAL RELEVANCE

GA-KR12 potentially is applicable for managing enamel caries.

Antibacterial and Antifungal Properties of Silver Nanoparticles-Effect of a Surface-Stabilizing Agent

The biocidal properties of silver nanoparticles (AgNPs) prepared with the use of biologically active compounds seem to be especially significant for biological and medical application. Therefore, the aim of this research was to determine and compare the antibacterial and fungicidal properties of fifteen types of AgNPs. The main hypothesis was that the biological activity of AgNPs characterized by comparable size distributions, shapes, and ion release profiles is dependent on the properties of stabilizing agent molecules adsorbed on their surfaces. Escherichia coli and Staphylococcus aureus were selected as models of two types of bacterial cells. Candida albicans was selected for the research as a representative type of eukaryotic microorganism. The conducted studies reveal that larger AgNPs can be more biocidal than smaller ones. It was found that positively charged arginine-stabilized AgNPs (ARGSBAgNPs) were the most biocidal among all studied nanoparticles. The strongest fungicidal properties were detected for negatively charged EGCGAgNPs obtained using (-)-epigallocatechin gallate (EGCG). It was concluded that, by applying a specific stabilizing agent, one can tune the selectivity of AgNP toxicity towards desired pathogens. It was established that E. coli was more sensitive to AgNP exposure than S. aureus regardless of AgNP size and surface properties.

Silver Nanoparticles Biosynthesis, Characterization, Antimicrobial Activities, Applications, Cytotoxicity and Safety Issues: An Updated Review

Rapid advances in nanotechnology have led to its emergence as a tool for the development of green synthesized noble metal nanoparticles, especially silver nanoparticles (AgNPs), for applications in diverse fields such as human health, the environment and industry. The importance of AgNPs is because of their unique physicochemical and antimicrobial properties, with a myriad of activities that are applicable in various fields, including the pharmaceutical industry. Countries with high biodiversity require the collection and transformation of information about biological assets into processes, associations, methods and tools that must be combined with the sustainable utilization of biological diversity. Therefore, this review paper discusses the applicable studies of the biosynthesis of AgNPs and their antimicrobial activities towards microorganisms in different areas viz. medicine and agriculture. The confirmed antiviral properties of AgNPs promote their applicability for SARS-CoV-2 treatment, based on assimilating the virus’ activities with those of similar viruses via in vivo studies. In this review, an insight into the cytotoxicity and safety issues of AgNPs, along with their future prospects, is also provided.

Remineralising dentine caries using an artificial antimicrobial peptide: An in vitro study

OBJECTIVE

To investigate the antibacterial and remineralising effects of a novel dual-action antimicrobial peptide, GA-KR12, on artificial dentine caries.

METHODS

Human dentine blocks with artificial carious lesions were allocated to two groups - Group 1: dentine blocks treated with the novel antimicrobial peptide GA-KR12 twice daily; Group 2: dentine blocks received water as the negative control. Two groups underwent Streptococcus mutan biofilm-remineralisation cycles at 37 °C for 7 days. The morphology, viability and growth kinetics of the S. mutans biofilm were evaluated by scanning electron microscopy (SEM), confocal laser scanning microscopy (CLSM) and colony-forming unit (CFU) counting, respectively. The dentine blocks' lesion depths and mineral loss, changes in chemical structure, dentine surface morphology and crystal characteristics were determined using micro-computed tomography, Fourier transform infrared (FTIR), SEM and X-ray diffraction (XRD), respectively.

RESULTS

The surface of the dentine blocks in Group 1 was partially covered by S. mutans with damaged cell structure. Group 2 showed affluent growth of S. mutans covering the dentine surface when compared to Group 1. The dead-to-live ratio of Group 1 and Group 2 were 0.78 ± 0.01 and 0.47 ± 0.08, respectively (p < 0.001). The Log CFUs of Group 1 and Group 2 were 7.14 ± 0.30 and 8.24 ± 0.20, respectively (p < 0.001). The lesion depths of Group 1 and Group 2 were 109 ± 1 µm and 135 ± 3 µm, respectively (p < 0.001). The mineral loss of Group 1 and Group 2 were 0.59 ± 0.08 gHApcm^-3 and 0.81 ± 0.07 gHApcm^-3, respectively (p < 0.001). FTIR showed the amide I-to-hydrogen phosphate (HPO₄^2-) ratios of Group 1 and Group 2 were 0.25 ± 0.05 and 0.39 ± 0.05 (p < 0.001), respectively. SEM images showed Group 1 had less exposed dentine collagen fibres than Group 2. The XRD revealed that the hydroxyapatite in Group 1 was well crystalised.

CONCLUSION

This study demonstrated that the novel antimicrobial peptide GA-KR12 inhibited the growth of S. mutans biofilm and enhanced the remineralisation of artificial dentine caries.

A novel dual-action antimicrobial peptide for caries management

OBJECTIVES

To develop a novel dual-action peptide with antimicrobial and mineralising properties.

METHODS

A novel peptide, namely GA-KR12, was synthesised through grafting gallic acid to KR12. The secondary structure of GA-KR12 was evaluated by circular dichroism spectroscopy. The stability was evaluated by high-performance liquid chromatography. The cytotoxicity was evaluated by a mitochondrial dehydrogenase activity assay. The antimicrobial properties against common cariogenic species were evaluated by minimum inhibitory concentration (MIC) and minimum bactericidal/fungicidal concentration (MBC/MFC). The morphology of cariogenic species was analysed by transmission electron microscope (TEM). To assess the mineralising effect of GA-KR12 on enamel, the lesion depths, mineral loss, surface morphology, calcium-to-phosphorus ratio and crystal characteristics were determined using micro-computed tomography, scanning electron microscopy (SEM) and energy dispersive spectroscopy X-ray diffraction, respectively.

RESULTS

GA-KR12 did not exhibit cytotoxicity against HGF. Around 82% of the GA-KR12 remained in human saliva at 37°C for 1 h. The MIC and MBC/MFC against the tested species were 10-320 μM and 20-1,280 μM, respectively. GA-KR12 induced remarkable morphological defects in the tested species. The enamel treated with GA-KR12 had smaller lesion depths (p < 0.001), less mineral loss (p < 0.001) and higher calcium-to-phosphorus molar ratios (p < 0.001) than those in the enamel treated with water. SEM showed a well-organised prism pattern in enamel treated with GA-KR12. X-ray diffraction revealed that the hydroxyapatite on the enamel treated with GA-KR12 was better crystalised.

CONCLUSIONS

This study developed a biocompatible and stable peptide which inhibited the growth of cariogenic species and mineralised the enamel caries.

CLINICAL SIGNIFICANCE

The novel dual-action peptide, GA-KR12, is potential applicable in the management of caries.

Cytotoxic and genotoxic effects in human gingival fibroblast and ions release of endodontic sealers incorporated with nanostructured silver vanadate

The cytotoxic and genotoxic effects of commercial endodontic sealers (AH Plus, Sealer 26 and Endomethasone N) incorporated with nanostructured silver vanadate decorated with silver nanoparticles (AgVO₃ - at concentrations 2.5, 5, and 10%) on human gingival fibroblast (HGF), and the silver (Ag⁺ ) and vanadium (V⁴⁺ /V⁵⁺ ) ions release were evaluated. Cytotoxicity, cell death, and genotoxicity tests were carried out with extract samples of 24-hr and 7-days. The release of Ag⁺ and V⁴⁺ /V⁵⁺ was evaluated. Cytotoxicity in HGF was caused by AH Plus (AP) with 5 and 10% of AgVO₃ (83.84 and 67.49% cell viability, respectively) with 24-hr extract (p < 0.05), as well as all concentrations of AP with 7-days extract (p < 0.05 -AP 0% = 73.17%; AP 2.5% = 75.07%; AP 5% = 70.62%; AP 10% = 68.46% cell viability). The commercial sealers Sealer 26 (S26) and Endomethasone N (EN) were cytotoxic (p < 0.05 - S26 0% = 34.81%; EN 0% = 20.99% cell viability with 7-days extract). AP 10% with 7-days extract induced 32% apoptotic cells in HGF (p < 0.05). Genotoxic effect was not observed. The AP groups released more Ag⁺ , while S26 and EN released more V⁴⁺ /V⁵⁺ in 24 hr. The Ag⁺ can be cytotoxic. In conclusion, the cytotoxicity caused to HGF can be attributed by the commercial sealers and enhanced by incorporation of AgVO₃ , was not observed genotoxic effect, and apoptosis was induced only by AH Plus 10% 7-days extract. Ag⁺ can influence cell viability.

Application of Selected Nanomaterials and Ozone in Modern Clinical Dentistry

This review is an attempt to summarize current research on ozone, titanium dioxide (TiO₂), silver (Ag), copper oxide CuO and platinum (Pt) nanoparticles (NPs). These agents can be used in various fields of dentistry such as conservative dentistry, endodontic, prosthetic or dental surgery. Nanotechnology and ozone can facilitate the dentist’s work by providing antimicrobial properties to dental materials or ensuring a decontaminated work area. However, the high potential of these agents for use in medicine should be confirmed in further research due to possible side effects, especially in long duration of observation so that the best way to apply them can be obtained.

All That Glitters Is Not Silver-A New Look at Microbiological and Medical Applications of Silver Nanoparticles

Silver and its nanoparticles (AgNPs) have different faces, providing different applications. In recent years, the number of positive nanosilver applications has increased substantially. It has been proven that AgNPs inhibit the growth and survival of bacteria, including human and animal pathogens, as well as fungi, protozoa and arthropods. Silver nanoparticles are known from their antiviral and anti-cancer properties; however, they are also very popular in medical and pharmaceutical nanoengineering as carriers for precise delivery of therapeutic compounds, in the diagnostics of different diseases and in optics and chemistry, where they act as sensors, conductors and substrates for various syntheses. The activity of AgNPs has not been fully discovered; therefore, we need interdisciplinary research to fulfil this knowledge. New forms of products with silver will certainly find application in the future treatment of many complicated and difficult to treat diseases. There is still a lack of appropriate and precise legal condition regarding the circulation of nanomaterials and the rules governing their safety use. The relatively low toxicity, relative biocompatibility and selectivity of nanoparticle interaction combined with the unusual biological properties allow their use in animal production as well as in bioengineering and medicine. Despite a quite big knowledge on this topic, there is still a need to organize the data on AgNPs in relation to specific microorganisms such as bacteria, viruses or fungi. We decided to put this knowledge together and try to show positive and negative effects on prokaryotic and eukaryotic cells.

Tackling Multidrug Resistance in Streptococci - From Novel Biotherapeutic Strategies to Nanomedicines

The pyogenic streptococci group includes pathogenic species for humans and other animals and has been associated with enduring morbidity and high mortality. The main reason for the treatment failure of streptococcal infections is the increased resistance to antibiotics. In recent years, infectious diseases caused by pyogenic streptococci resistant to multiple antibiotics have been raising with a significant impact to public health and veterinary industry. The rise of antibiotic-resistant streptococci has been associated to diverse mechanisms, such as efflux pumps and modifications of the antimicrobial target. Among streptococci, antibiotic resistance emerges from previously sensitive populations as result of horizontal gene transfer or chromosomal point mutations due to excessive use of antimicrobials. Streptococci strains are also recognized as biofilm producers. The increased resistance of biofilms to antibiotics among streptococci promote persistent infection, which comprise circa 80% of microbial infections in humans. Therefore, to overcome drug resistance, new strategies, including new antibacterial and antibiofilm agents, have been studied. Interestingly, the use of systems based on nanoparticles have been applied to tackle infection and reduce the emergence of drug resistance. Herein, we present a synopsis of mechanisms associated to drug resistance in (pyogenic) streptococci and discuss some innovative strategies as alternative to conventional antibiotics, such as bacteriocins, bacteriophage, and phage lysins, and metal nanoparticles. We shall provide focused discussion on the advantages and limitations of agents considering application, efficacy and safety in the context of impact to the host and evolution of bacterial resistance.

New Bactericide Orthodonthic Archwire: NiTi with Silver Nanoparticles

A potential new bactericide treatment for NiTi orthodontic archwires based in the electrodeposition of silver nanoparticles on the surface was studied. Twenty-five archwires were treated by electrodeposition, obtaining nanoparticles of silver embedded on the archwire surface. These were evaluated in order to investigate the possible changes on the superelastic characteristics (critical temperatures and stresses), the nickel ion release, and the bacteria culture behavior. The chemical composition was analyzed by Energy Dispersive X-Ray Spectroscopy-microanalysis; the singular temperatures of the martensitic transformation were obtained by a flow calorimeter. Induced martensitic transformation stresses were obtained by mechanical testing apparatus. Nickel ion release was analyzed by inductively coupled plasma-mass spectrometry (ICP-MS) equipment using artificial saliva solution at 37 °C. Bacterial tests were studied with the most used oral bacterial strains: Streptococcus sanguinis and Lactobacillus salivarius. NiTi samples were immersed in bacterial suspensions for 2 h at 37 °C. Adhered bacteria were separated and seeded on agar plates: Tood-Hewitt (TH) and Man-Rogosa-Sharpe (MRS) for S. sanguinis and for L.salivarius, respectively. These were then incubated at 37 °C for 1 day and the colonies were analyzed. The results showed that the transformation temperatures and the critical stresses have not statistically significant differences. Likewise, nickel ion release at different immersion times in saliva at 37 °C does not present changes between the original and treated with silver nanoparticles archwires. Bacteria culture results showed that the reduction of the bacteria due to the presence to the nanoparticles of silver is higher than 90%. Consequently, the new treatment with nanoparticles of silver could be a good candidate as bactericidic orthodontic archwire.

Use of Silver Nanomaterials for Caries Prevention: A Concise Review

Objective

The aim of this concise review is to summarize the use of silver nanomaterials for caries prevention.

Methods

Two researchers independently performed a literature search of publications in English using Embase, Medline, PubMed, and Scopus databases. The keywords used were (silver nanoparticles OR AgNPs OR nano silver OR nano-silver) AND (caries OR tooth decay OR remineralisation OR remineralization). They screened the title and abstract to identify potentially eligible publications. They then retrieved the full texts of the identified publications to select original research reporting silver nanomaterials for caries prevention.

Results

The search identified 376 publications, and 66 articles were included in this study. The silver nanomaterials studied were categorized as resin with silver nanoparticles (n=31), silver nanoparticles (n=21), glass ionomer cement with silver nanoparticles (n=7), and nano silver fluoride (n=7). Most (59/66, 89%) studies investigated the antibacterial properties, and they all found that silver nanomaterials inhibited the adhesion and growth of cariogenic bacteria, mainly Streptococcus mutans. Although silver nanomaterials were used as anti-caries agents, only 11 (11/66, 17%) studies reported the effects of nanomaterials on the mineral content of teeth. Eight of them are laboratory studies, and they found that silver nanomaterials prevented the demineralization of enamel and dentin under an acid or cariogenic biofilm challenge. The remaining three are clinical trials that reported that silver nanomaterials prevented and arrested caries in children.

Conclusion

Silver nanoparticles have been used alone or with resin, glass ionomer, or fluoride for caries prevention. Silver nanomaterials inhibit the adhesion and growth of cariogenic bacteria. They also impede the demineralization of enamel and dentin.

Synthesis and Characterization of Fluoridated Silver Nanoparticles and Their Potential as a Non-Staining Anti-Caries Agent

Objectives

The first objective of this study was to prepare sodium fluoride (NaF) solution with various concentrations of polyethylene glycol-coated silver nanoparticles (PEG-AgNPs). The second objective was to study the antibacterial activity against Streptococcus mutans and the tooth-staining effect of the solution.

Methods

PEG-AgNPs were prepared via the one-step chemical reduction of silver acetate with thiolated polyethylene glycol. The PEG-AgNPs were characterized with ultraviolet-visible spectrometry and transmission electron microscopy. The half maximal inhibitory concentration (IC50) for the PEG-AgNPs against Streptococcus mutans and human gingival fibroblasts (HGF-1) were determined. The staining effect on dentin and enamel for the 2.5% NaF solutions with PEG-AgNPs at 12,800, 6400, 1600, and 400 ppm was investigated using digital spectrophotometry. The IC50 of the fluoridated silver nanoparticles against Streptococcus mutans were measured.

Results

The PEG-AgNPs have an average diameter of 2.56±0.43 nm and showed excellent stability at high ionic strength (2.5% NaF) for 18 months. The IC50 of PEG-AgNPs against Streptococcus mutans was found to be 21.16±1.08 ppm silver, which was half of IC50 against HGF-1 cells (42.36±1.12 ppm), providing a working range to kill bacteria with no harm to human cells. The formulations with different concentrations of PEG-AgNPs showed no significant staining of teeth. Combining PEG-AgNPs with NaF significantly expanded the therapeutic window against Streptococcus mutans by reducing its IC50.

Conclusion

A biocompatible solution of NaF with PEG-AgNPs was developed. Because it has antibacterial activity against Streptococcus mutans and no tooth-staining effect, it can be used as an anti-caries agent.

Remineralising Dentine Caries Using Sodium Fluoride with Silver Nanoparticles: An In Vitro Study

Objective

To investigate the remineralizing and staining effects of sodium fluoride (NaF) solution with polyethylene glycol-coated silver nanoparticles (PEG-AgNPs) on artificial dentine caries.

Materials and Methods

Demineralized human dentine blocks were allocated to three groups. The blocks in group 1 underwent a topical application of a 12% silver diamine fluoride (SDF, 14,150 ppm fluoride) solution. The blocks in group 2 received a topical application of a 2.5% NaF (11,310 ppm fluoride) with PEG-AgNPs (400 ppm silver). The blocks in group 3 received deionized water. All blocks were subjected to pH cycling for 8 days. The surface morphology and cross-sectional features were investigated using scanning electron microscopy (SEM). The color parameters, crystal characteristics, lesion depth, and collagen degradation of the blocks were assessed using digital spectrophotometry, X-ray diffraction (XRD), micro-computed tomography, and spectrophotometry with a hydroxyproline assay, respectively.

Results

The SEM showed that dentine collagen was exposed in group 3 but not in groups 1 and 2. The mean lesion depths in groups 1 to 3 were 118±7 µm, 121±14 µm, and 339±20 µm, respectively (groups1,2<3; p<0.001). The data indicated that fluoridated PEG-AgNPs introduced no significant color effect on dentine, but SDF caused distinct discoloration. The XRD indicated that silver chloride was formed in group 1, and fluorapatite was detected in groups 1 and 2. The concentration of hydroxyproline liberated from collagen was significantly less in groups 1 and 2 than in group 3.

Conclusion

The use of NaF solution with PEG-AgNPs can remineralize artificial dentine caries and inhibit collagen degradation without causing significant tooth staining.

The Antibacterial Mechanism of Silver Nanoparticles and Its Application in Dentistry

Nanotechnology has recently emerged as a rapidly growing field with numerous biomedical science applications. At the same time, silver has been adopted as an antimicrobial material and disinfectant that is relatively free of adverse effects. Silver nanoparticles possess a broad spectrum of antibacterial, antifungal and antiviral properties. Silver nanoparticles have the ability to penetrate bacterial cell walls, changing the structure of cell membranes and even resulting in cell death. Their efficacy is due not only to their nanoscale size but also to their large ratio of surface area to volume. They can increase the permeability of cell membranes, produce reactive oxygen species, and interrupt replication of deoxyribonucleic acid by releasing silver ions. Researchers have studied silver nanoparticles as antimicrobial agents in dentistry. For instance, silver nanoparticles can be incorporated into acrylic resins for fabrication of removable dentures in prosthetic treatment, composite resin in restorative treatment, irrigating solution and obturation material in endodontic treatment, adhesive materials in orthodontic treatment, membrane for guided tissue regeneration in periodontal treatment, and titanium coating in dental implant treatment. Although not all authorities have acknowledged the safety of silver nanoparticles, no systemic toxicity of ingested silver nanoparticles has been reported. A broad concern is their potential hazard if they are released into the environment. However, the interaction of nanoparticles with toxic materials and organic compounds can either increase or reduce their toxicity. This paper provides an overview of the antibacterial use of silver nanoparticles in dentistry, highlighting their antibacterial mechanism, potential applications and safety in clinical treatment.

Cytotoxicity and release ions of endodontic sealers incorporated with a silver and vanadium base nanomaterial

The modification of endodontic sealers with nanoparticles to confer antimicrobial activity allow greater effect, with interaction at a molecular level. The nanostructured silver vanadate decorated with silver nanoparticles (AgVO₃) is a nanomaterial unprecedented in dentistry for this application. This study incorporated the AgVO₃ into three endodontic sealers of different compositions and evaluate the cytotoxicity and release of compounds. The groups of commercially available AH Plus, Sealer 26, and Endomethasone N and groups of the same sealers with incorporated AgVO₃ (at concentrations 2.5, 5, 10%) were prepared, and extracts of the specimens were obtained for 24 h. The cell viability (cytotoxicity) of human gingival fibroblasts (HGF) was assessed after 24 h, 7 and 14 days. Silver (Ag⁺) and vanadium (V⁴⁺/V⁵⁺) ion release was quantified after 24 h by ICP-MS. Data were analyzed by Kruskal-Wallis and Dunn's post-hoc (α = 0.05). The cell viability was inversely proportional to treatment time. The Sealer 26 and Endomethasone N groups were cytotoxic for HGF cells, regardless of the incorporation of the AgVO₃ (p > 0.05), and the incorporation reduced cell viability of AH Plus (p < 0.05). The release of ions was proportional to the concentration of AgVO₃. AH Plus released more Ag⁺ ions, and Sealer 26 and Endomethasone N releases more V⁴⁺/V⁵⁺ ions. In conclusion, it was not possible to confirm the influence of AgVO₃ on HGF cell viability to Sealer 26 and Endomethasone N, however, nanomaterial influenced cell-viability to AH Plus, so the commercial sealers can be cytotoxic in synergy with the nanomaterial. The release of Ag⁺ and V⁴⁺/V⁵⁺ was proportional to the AgVO₃ incorporated.