Synthesis, Electronic, and Antibacterial Properties of 3,7-Di(hetero)aryl-substituted Phenothiazinyl N-Propyl Trimethylammonium Salts.

In this study, a library of 3,7-di(hetero)aryl-substituted 10-(3-trimethylammoniumpropyl)10H-phenothiazine salts is prepared. These title compounds and their precursors are reversible redox systems with tunable potentials. The Hammett correlation gives a very good correlation of the first oxidation potentials with σp parameters. Furthermore, the title compounds and their precursors are blue to green-blue emissive. Screening of the salts reveals for some derivatives a distinct inhibition of several pathogenic bacterial strains (Mycobacterium tuberculosis, Staphylococcus aureus, Escherichia coli, Aconetobacter baumannii, and Klebsiella pneumoniae) in the lower micromolar range.

Advances in the Synthesis of Biologically Active Quaternary Ammonium Compounds.

This review provides a comprehensive overview of recent advancements in the design and synthesis of biologically active quaternary ammonium compounds (QACs). The covered scope extends beyond commonly reviewed antimicrobial derivatives to include synthetic agents with antifungal, anticancer, and antiviral properties. Additionally, this review highlights examples of quaternary ammonium compounds exhibiting activity against protozoa and herbicidal effects, as well as analgesic and anesthetic derivatives. The article also embraces the quaternary-ammonium-containing cholinesterase inhibitors and muscle relaxants. QACs, marked by their inherent permanent charge, also find widespread usage across diverse domains such as fabric softeners, hair conditioners, detergents, and disinfectants. The effectiveness of QACs hinges greatly on finding the right equilibrium between hydrophilicity and lipophilicity. The ideal length of the alkyl chain varies according to the unique structure of each QAC and its biological settings. It is expected that this review will provide comprehensive data for medicinal and industrial chemists to design and develop novel QAC-based products.

PDADMAC/Alginate-Coated Gold Nanorod For Eradication of Staphylococcus Aureus Biofilms.

Introduction: Over 75% of clinical microbiological infections are caused by bacterial biofilms that grow on wounds or implantable medical devices. This work describes the development of a new poly(diallyldimethylammonium chloride) (PDADMAC)/alginate-coated gold nanorod (GNR/Alg/PDADMAC) that effectively disintegrates the biofilms of Staphylococcus aureus (S. aureus), a prominent pathogen responsible for hospital-acquired infections. Methods: GNR was synthesised via seed-mediated growth method, and the resulting nanoparticles were coated first with Alg and then PDADMAC. FTIR, zeta potential, transmission electron microscopy, and UV-Vis spectrophotometry analysis were performed to characterise the nanoparticles. The efficacy and speed of the non-coated GNR and GNR/Alg/PDADMAC in disintegrating S. aureus-preformed biofilms, as well as their in vitro biocompatibility (L929 murine fibroblast) were then studied. Results: The synthesised GNR/Alg/PDADMAC (mean length: 55.71 ± 1.15 nm, mean width: 23.70 ± 1.13 nm, aspect ratio: 2.35) was biocompatible and potent in eradicating preformed biofilms of methicillin-resistant (MRSA) and methicillin-susceptible S. aureus (MSSA) when compared to triclosan, an antiseptic used for disinfecting S. aureus colonisation on abiotic surfaces in the hospital. The minimum biofilm eradication concentrations of GNR/Alg/PDADMAC (MBEC50 for MRSA biofilm = 0.029 nM; MBEC50 for MSSA biofilm = 0.032 nM) were significantly lower than those of triclosan (MBEC50 for MRSA biofilm = 10,784 nM; MBEC50 for MRSA biofilm 5967 nM). Moreover, GNR/Alg/PDADMAC was effective in eradicating 50% of MRSA and MSSA biofilms within 17 min when used at a low concentration (0.15 nM), similar to triclosan at a much higher concentration (50 µM). Disintegration of MRSA and MSSA biofilms was confirmed by field emission scanning electron microscopy and confocal laser scanning microscopy. Conclusion: These findings support the potential application of GNR/Alg/PDADMAC as an alternative agent to conventional antiseptics and antibiotics for the eradication of medically important MRSA and MSSA biofilms.

Quaternary Ammonium Assisted Synthesis of Melanin-like Poly(l-DOPA) Nanoparticles with a Boosted Photothermal Effect.

Poly(levodopa) nanoparticles (P(l-DOPA) NPs) are another kind of melanin mimetic besides well-established polydopamine nanoparticles (PDA NPs). Due to the presence of carboxyl groups, the oxidative polymerization of l-DOPA to obtain particles was not as efficient as that of dopamine. Several established methods toward P(l-DOPA) NP fabrication do not combine convenience, morphological regularity, size controllability, low cost, and adaptability to metal-free application scenarios. In this work, P(l-DOPA) NPs were successfully prepared in hot water with the assistant of organic quaternary ammonium, due to the extra physical cross-linking mediated by cations. The employed physical interactions could also be affected by quaternary ammonium structure (i.e., number of cation heads, length of alkyl chain) to achieve different polymerization acceleration effects. The obtained P(l-DOPA) NPs retained superior photothermal properties and outperformed PDA-based melanin materials. Furthermore, P(l-DOPA) NPs were used in photothermal tumor therapy and showed better efficacy. This study offers new insights into the synthesis of melanin-like materials, as well as new understanding of the interaction between quaternary ammonium and bioinspired polyphenolic materials.

Synergistic antibacterial effect and mechanism between Cu2O nanoparticles and quaternary ammonium salt in moisture-curable acrylic coatings.

Combining with various antibacterial mechanisms is the preferred strategy to fabricate coatings with effective antibacterial performance. Herein, Cu2O nanoparticles and dimethyloctadecyl [3-(trimethoxysilyl) propyl] ammonium chloride, a kind of quaternary ammonium salt (QAS), were simultaneously incorporated into a moisture-curable acrylic resin in order to achieve both contact-killing and release-killing abilities for antibacterial coatings. The surface morphology, surface composition and basic properties of the coatings were thoroughly characterized. The antibacterial performance of the coatings was determined by in-vitro bacteriostatic test. Under the constant total mass fraction of antibacterial agents, both Cu2O and QAS content possessed the highest value on the coating surface at Cu2O/QAS mass ratio of 1:1, and correspondingly, the coatings reached sterilizing rate above 99 % against both E. coli and S. loihica, indicating the existence of synergistic effect between Cu2O and QAS. The synergistic antibacterial mechanism of the coatings involved two aspects. Firstly, the combination of contact-killing and release-killing biocides resulted in high bactericidal and antibiofilm activity against different bacteria. Further, the grafting of QAS molecules on the surface of Cu2O particles brought about the spontaneous migration of nanoparticles to the coating surface. The interaction between Cu2O and QAS also inhibited the phase separation of QAS and prolonged the release of Cu2+ at the same time. The coatings, therefore, exhibited stable antibacterial performance at varied service conditions.

Regulating molecular brush structure on cotton textiles for efficient antibacterial properties.

The molecular brush structures have been developed on cotton textiles for long-term and efficient broad-spectrum antimicrobial performances through the cooperation of alkyl-chain and quaternary ammonium sites. Results show that efficient antibacterial performances can be achieved by the regulation of the alkyl chain length and quaternary ammonium sites. The antibacterial efficiency of the optimized molecular brush structure of [3-(N,N-Dimethylamino)propyl]trimethoxysilane with cetyl modification on cotton textiles (CT-DM-16) can reach more than 99 % against both E. coli and S. aureus. Alkyl-chain grafting displayed significantly improvement in the antibacterial activity against S. aureus with (N,N-Diethyl-3-aminopropyl)trimethoxysilane modification on cotton textiles (CT-DE) based materials. The positive N sites and alkyl chains played important roles in the antibacterial process. Proteomic analysis reveals that the contributions of cytoskeleton and membrane-enclosed lumen in differentially expressed proteins have been increased for the S. aureus antibacterial process, confirming the promoted puncture capacity with alkyl-chain grafting. Theoretical calculations indicate that the positive charge of N sites can be enhanced through alkyl-chain grafting, and the possible distortion of the brush structure in application can further increase the positive charge of N sites. Uncovering the regulation mechanism is considered to be important guidance to develop novel and practical antibacterial materials.

Polyvinyl alcohol/chitosan quaternary ammonium salt composite hydrogel with directional macroporous structure for photothermal synergistic antibacterial and wound healing promotion.

After skin tissue trauma, wound infections caused by bacteria posed a great threat to skin repair. However, resistance to antibiotics, the current treatment of choice for bacterial infections, greatly affected the efficiency of anti-infection and wound healing. Therefore, there has been a critical need for the development of novel antimicrobial materials and advanced therapeutic methods to aid in skin repair. In this paper, rGO-PDA@ZIF-8 nanofillers were prepared by coating graphene oxide (GO) with dopamine (DA), followed by in situ growth of zeolite imidazolate framework-8 (ZIF-8). Using polyvinyl alcohol (PVA) and chitosan quaternary ammonium salt (CS) as matrix materials, along with polyethylene glycol (PEG) as a pore-forming agent, and rGO-PDA@ZIF-8 as an antimicrobial nano-filler, we successfully prepared rGO-PDA@ZIF-8/PVA/CS composite hydrogels with a directional macroporous structure using bidirectional freezing method and phase separation technique. This hydrogel exhibited excellent mechanical properties, good solubility and water retention capabilities. In addition, the hydrogel demonstrated excellent biocompatibility. Most notably, it not only exhibited excellent bactericidal effect against E. coli and S. aureus (99.1 % and 99.0 %, respectively) under the synergistic effect of intrinsic antibacterial activity and photothermal antibacterial, but also exhibited the ability to promote wound healing, making it a promising candidate for wound healing applications.

Formation mechanism of a novel core-shell with tetradecyl dimethyl benzyl ammonium-modified montmorillonite interlayer nanofibrous membrane and its antimicrobial properties.

A novel core-shell with a tetradecyl dimethyl benzyl ammonium chloride-modified montmorillonite (TDMBA/MMT) interlayer silk fibroin (SF)/poly(lactic acid) (PLLA) nanofibrous membrane was fabricated using a simple conventional electrospinning method. Scanning electron microscopy and pore size analyses revealed that this core-shell with TDMBA/MMT interlayer maintained its nanofibrous morphology and larger pore structure more successfully than SF/PLLA nanofibrous membranes after treatment with 75% ethanol vapor. Transmission electron microscopy and energy-dispersive X-ray spectroscopy analyses testified that the SF/PLLA-TDMBA/MMT nanofibers exhibited a core-shell with an interlayer structure, with SF/PLLA in the core-shell layer and TDMBA/MMT in the interlayer. The formation of a core-shell with interlayer nanofibers was primarily attributed to the uniform dispersion of TDMBA/MMT nanosheets in a solution owing to its exfoliation using hexafluoroisopropanol and then preparing a stable spinning solution similar to an emulsion. Compared to SF/PLLA nanofibrous membranes, the core-shell structure with TDMBA/MMT interlayers of SF/PLLA nanofibrous membranes exhibited enhanced hydrophilicity, thermal stability, mechanical properties as well as improved and long-lasting antimicrobial performance against Escherichia coli and Staphylococcus aureus without cytotoxicity.

Preparation of biguanidine quaternary ammonium salts grafted chitosan with enhanced antibacterial and antibiofilm activities.

N-(4-N'-pyridine-benzylcarbonyl chloride) chitosan (CBPyC), N-p-biguanidine benzoyl chitosan (CSBG), and N-(p-biguanidine -1-pyridine-4-benzylcarbonyl chloride) chitosan (CSQPG) were synthesized. The structures of prepared chitosan derivatives were characterized using nuclear magnetic resonance spectroscopy (NMR) and ultraviolet-visible (UV-vis) spectroscopy, and the degree of substitution was determined through elemental analysis (EA) and evaluated on the basis of the integral values in 1H NMR. The antibacterial activities of chitosan derivatives against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) were investigated in vitro using antibacterial rate, minimal inhibitory concentration and minimum bacterial concentration assays. The antibiofilm activity was also assessed using the crystal violet assay. CSQPC exhibited higher antibacterial and antibiofilm activities against E. coli and S. aureus compared to CBPyC and CSBG. The antibacterial rate of CSQPG against E. coli and S. aureus at a concentration of 0.5 mg/mL was 43.3% and 100%, respectively. The biofilm inhibition rate of CSQPG at 0.5 MIC against E. coli and S. aureus was 56.5% and 69.1%, respectively. At a concentration of 2.5 mg/mL, the biofilm removal rates of E. coli and S. aureus were 72.9% and 90.1%, respectively. The antibacterial and antibiofilm activities of CSQPG were better than CSBG and CBPyC, and the combination of guanidine and quaternary ammonium further improved the positive charge density of chitosan and enhanced its antibacterial activity.

Effect of silver diamine fluoride and nano silver fluoride on oral health-related quality of life of children with early childhood caries: A randomized clinical trial.

OBJECTIVES: Untreated caries in primary teeth is one of the most prevalent health problems in children worldwide. Silver diamine fluoride (SDF) non-invasively arrests caries but causes staining unlike Nano Silver Fluoride (NSF) which causes no stains. This study compared the effect of NSF and 38 % SDF on the oral health related quality of life (OHRQoL) of preschool children after 6 months. METHODS: Children were included if they were younger than 4 years, with at least one active lesion, ICDAS score ≥3, attending nurseries in a rural area in Alexandria, Egypt. They were randomly assigned to receive NSF once at baseline, or SDF at baseline and after 6 months. The Arabic version of the Early Childhood Oral Health Impact Scale (A-ECOHIS) was used to assess the OHRQoL. The groups were compared using chi-square test and the effect of the intervention on OHRQoL was assessed using multiple linear regression. RESULTS: 360 children were included, mean (SD) age = 42.3 (8.2) months. After 6 months, NSF had significantly lower A-ECOHIS scores than SDF in bivariate analysis (p< 0.05) and in regression analysis (B= -5.02, p = 0.001) after adjusting for confounders. There were significant reductions in the A-ECOHIS total and domains' scores in both study groups, except for the social interaction domain in the SDF group. CONCLUSION: After 6-month, both agents significantly improved children's OHRQoL although NSF had a significantly better impact on OHRQoL than SDF. CLINICAL SIGNIFICANCE: Patient-reported outcomes support the inclusion of the two agents among the options for ECC management with better effect on quality of life after NSF. TRIAL REGISTRATION: The trial was registered in the clinicaltrials.gov registry (#NCT05255913).

Clinical evidence for silver diamine fluoride to reduce dentine hypersensitivity: A systematic review.

OBJECTIVE: To assess the clinical evidence for silver diamine fluoride (SDF) to reduce dentine hypersensitivity in adults. METHODS: Two independent researchers searched the English literature in five databases (Scopus, PubMed, Web of Science, EMBASE and the Cochrane Library) up to 15th July 2023 for clinical trials investigating the desensitising effect of professionally applied SDF to manage dentine hypersensitivity in adults aged 18 or above at any follow-up period. The primary outcome was the change in dentine hypersensitivity between baseline and follow-up visits after SDF application regarding any validated pain outcome measures. The Cochrane guidelines were used for the risk of bias assessment. RESULTS: Three hundred and thirty-one studies were identified, and four of them were finally included. Three of the included studies were rated as having a 'low risk' of bias. The SDF solution reduced dentine hypersensitivity in adults. The percentage reduction in dentine hypersensitivity ranged from 23 % to 56 % after a single application of SDF solution. Moreover, the SDF solution was more effective than potassium nitrate, potassium oxalate and glutaraldehyde plus hydroxyethyl methacrylate in reducing dentine hypersensitivity. Meta-analysis indicated a more significant reduction in visual analogue scales (1-10) by 1.35 (95 % CI:0.9-1.8; p<0.00001) after receiving the SDF application than controls. CONCLUSION: The included clinical trials showed that SDF solution reduced dentine hypersensitivity in adults. However, clinical trials are few, and their protocol varied from one another. Further well-designed clinical trials should be conducted to provide more evidence on its use to manage dentine hypersensitivity. CLINICAL SIGNIFICANCE: SDF is cleared as desensitizing agents by the US Food and Drug Administration to manage dentine hypersensitivity, which induces pain, limits food choice, and impacts the quality of life. Evidence from this systematic review informs clinicians and provides researchers insight for future research on SDF use for dentine hypersensitivity. THE INTERNATIONAL PROSPECTIVE REGISTER OF SYSTEMATIC REVIEWS (PROSPERO) REGISTRATION NUMBER: CRD42023462613.

Quaternary ammonium salts for water treatment with balanced rate of sterilization and degradation.

The growing number of infections caused by drug-resistant bacteria which arise from the overuse of antibiotics has severely affected the normal operation of human society. The high antibacterial activity of QAS makes it promising as an alternative to antibiotics, but it suffers from secondary pollution due to its non-degradation. Here we have synthesized a class of gemini quaternary ammonium salts (GQAS) with different carbon chain lengths containing ester groups by using facile methylation reaction. Quaternary ammonium groups contribute to insert negatively charged bacterial membranes, resulting in membrane damage and bacteria death. Compared with conventional single-chain QAS, except for the more efficient antibacterial efficiency attribute to the presence of the second carbon chain, GQAS with alterable antibacterial properties can minimize the possibility of bacterial resistance and reduce the accumulation of GQAS in the environment through the introduction of degradable ester groups. GQAS is completely superior to the commercial bactericide benzalkonium chloride (BAC) in both antibacterial activity and degrade performance, which can be used as a more environmentally friendly bactericide.

Hyperbranched Polymer Induced Antibacterial Tree-Like Nanofibrous Membrane for High Effective Air Filtration.

The air filtration materials with high efficiency, low resistance, and extra antibacterial property are crucial for personal health protection. Herein, a tree-like polyvinylidene fluoride (PVDF) nanofibrous membrane with hierarchical structure (trunk fiber of 447 nm, branched fiber of 24.7 nm) and high filtration capacity is demonstrated. Specifically, 2-hydroxypropyl trimethyl ammonium chloride terminated hyperbranched polymer (HBP-HTC) with near-spherical three-dimensional molecular structure and adjustable terminal positive groups is synthesized as an additive for PVDF electrospinning to enhance the jet splitting and promote the formation of branched ultrafine nanofibers, achieving a coverage rate of branched nanofibers over 90% that is superior than small molecular quaternary ammonium salts. The branched nanofibers network enhances mechanical properties and filtration efficiency (99.995% for 0.26 µm sodium chloride particles) of the PVDF/HBP-HTC membrane, which demonstrates reduced pressure drop (122.4 Pa) and a quality factor up to 0.083 Pa-1 on a 40 µm-thick sample. More importantly, the numerous quaternary ammonium salt groups of HBP-HTC deliver excellent antibacterial properties to the PVDF membranes. Bacterial inhibitive rate of 99.9% against both S. aureus and E. coli is demonstrated in a membrane with 3.0 wt% HBP-HTC. This work provides a new strategy for development of high-efficiency and antibacterial protection products.

Protocol for aqueous synthesis of bioactive quaternary ammonium betaine derivatives under blue LED.

Quaternary ammonium compounds exhibit diverse applications as antibiotics, as surfactants, in paper industries, in sewage treatment, and in aquaculture. Here, we present a protocol for synthesizing a library of bioactive quaternary ammonium betaine derivatives under blue LED in water. We describe steps for preparing diazo compounds, synthesizing glycine betaine derivatives, and isolating pure final compounds via precipitation from an aqueous reaction mixture. This protocol promotes a sustainable approach by using water as the reaction medium and room temperature reactions. For complete details on the use and execution of this protocol, please refer to Rath et al. (2023).1.

Polypropylene-Rendered Antiviral by Three-Dimensionally Surface-Grafted Poly(N-benzyl-4-vinylpyridinium bromide).

To inhibit viral infection, it is necessary for the surface of polypropylene (PP), a polymer of significant industrial relevance, to possess biocidal properties. However, due to its low surface energy, PP weakly interacts with other organic molecules. The biocidal effects of quaternary ammonium compounds (QACs) have inspired the development of nonwoven PP fibers with surface-bound quaternary ammonium (QA). Despite this advancement, there is limited knowledge regarding the durability of these coatings against scratching and abrasion. It is hypothesized that the durability could be improved if the thickness of the coating layer were controlled and increased. We herein functionalized PP with three-dimensionally surface-grafted poly(N-benzyl-4-vinylpyridinium bromide) (PBVP) by a simple and rapid method involving graft polymerization and benzylation and examined the influence of different factors on the antiviral effect of the resulting plastic by using a plaque assay. The thickness of the PBVP coating, surface roughness, and amount of QACs, which jointly determine biocidal activity, could be controlled by adjusting the duration and intensity of the ultraviolet irradiation used for grafting. The best-performing sample reduced the viral infection titer of an enveloped model virus (bacteriophage ϕ6) by approximately 5 orders of magnitude after 60 min of contact and retained its antiviral activity after surface polishing-simulated scratching and abrasion, which indicated the localization of QACs across the coating interior. Our method may expand the scope of application to resin plates as well as fibers of PP. Given that the developed approach is not limited to PP and may be applied to other low-surface-energy olefinic polymers such as polyethylene and polybutene, our work paves the way for the fabrication of a wide range of biocidal surfaces for use in diverse environments, helping to prevent viral infection.

A novel chitosan antioxidant bearing sulfhydryl group: Synthesis, characterization and activity assessment.

To improve the antioxidant activity, sulfhydryl groups (-SH) were introduced into chitosan. Acylated chitosan derivatives, chitosan cationic salt derivatives, hydroxypropyl trimethylammonium chloride chitosan quaternary ammonium salt (HACC) derivatives and N,N,N-trimethyl chitosan iodine (TMC) derivatives were obtained. The chitosan derivatives were characterized by FTIR and 1H NMR to confirm the successful synthesis. Ellman's reagent was used to determine that the compound contained free sulfhydryl groups. The water solubility and thermal stability of chitosan and derivatives were evaluated. The antioxidant activities of the derivatives were verified, including DPPH radical scavenging activity, superoxide anion radical scavenging activity and reducing power activity. The novel chitosan derivatives showed excellent antioxidant activities. Toxicity assay used L929 cells proved that the derivatives had no significant toxic. The results showed that the chitosan derivatives bearing sulfhydryl groups described in this paper has a certain antioxidant effect, which provides a practical approach for further study of chitosan.

Improvement of the Antioxidant and Antitumor Activities of Benzimidazole-Chitosan Quaternary Ammonium Salt on Drug Delivery Nanogels.

The present study focused on the design and preparation of acid-responsive benzimidazole-chitosan quaternary ammonium salt (BIMIXHAC) nanogels for a controlled, slow-release of Doxorubicin HCl (DOX.HCl). The BIMIXHAC was crosslinked with sodium tripolyphosphate (TPP) using the ion crosslinking method. The method resulted in nanogels with low polydispersity index, small particle size, and positive zeta potential values, indicating the good stability of the nanogels. Compared to hydroxypropyl trimethyl ammonium chloride chitosan-Doxorubicin HCl-sodium tripolyphosphate (HACC-D-TPP) nanogel, the benzimidazole-chitosan quaternary ammonium salt-Doxorubicin HCl-sodium tripolyphosphate (BIMIXHAC-D-TPP) nanogel show higher drug encapsulation efficiency and loading capacity (BIMIXHAC-D-TPP 93.17 ± 0.27% and 31.17 ± 0.09%), with acid-responsive release profiles and accelerated release in vitro. The hydroxypropyl trimethyl ammonium chloride chitosan-sodium tripolyphosphate (HACC-TPP), and benzimidazole-chitosan quaternary ammonium salt-sodium tripolyphosphate (BIMIXHAC-TPP) nanogels demonstrated favorable antioxidant capability. The assay of cell viability, measured by the MTT assay, revealed that nanogels led to a significant reduction in the cell viability of two cancer cells: the human lung adenocarcinoma epithelial cell line (A549) and the human breast cancer cell line (MCF-7). Furthermore, the BIMIXHAC-D-TPP nanogel was 2.96 times less toxic than DOX.HCl to the mouse fibroblast cell line (L929). It was indicated that the BIMIXHAC-based nanogel with enhanced antioxidant and antitumor activities and acidic-responsive release could serve as a potential nanocarrier.

Resistance to Chlorhexidine and Benzalkonium Chloride in E. Coli ST131, A. Baumannii, and P. Aeruginosa Isolates.

BACKGROUND: The goal was to assess the antimicrobial efficacy of two commonly used biocides, chlorhexidine, and benzalkonium chloride, against MDR isolates of Pseudomonas aeruginosa, Acinetobacter baumannii, and Escherichia coli ST131, as well as the prevalence of resistance genes. METHODS: MIC of chlorhexidine and benzalkonium chloride and their effects on both the planktonic phase and biofilm were determined. Finally, the presence of genes responsible for resistance to quaternary ammonium compounds was investigated by PCR. RESULTS: No significant relationship was observed between the presence of resistance genes and different concentrations of quaternary ammonium compounds (benzalkonium chloride). There was no association between biofilm formation and the presence of resistance genes. CONCLUSIONS: Chlorhexidine digluconate and benzalkonium chloride at appropriate concentrations could prevent biofilm formation.

Silver Diamine Fluoride Staining With Potassium Iodide: A Prospective Cohort Study.

BACKGROUND: Staining after silver diamine fluoride (SDF) treatment limits treatment acceptability but is also used as a clinical indicator of lesion stability. Potassium iodide (KI) has been postulated to modify SDF staining. Understanding the natural history and resultant shade of SDF/KI-treated lesions will inform clinical decision-making. This study describes the change in colour of carious lesions in primary teeth treated with SDF and KI. METHODS: One hundred carious lesions in primary teeth were treated with SDF + KI (Riva Star, SDI) and followed up over 6 months. Lesion shade was determined using standardised intraoral photography and broadly categorised into 4 shades: yellow, light brown, dark brown, and black. Lesions were digitally isolated, and colour was evaluated using CIELAB (L*: lightness, a*/b*: hue) and perceptible colour change (ΔE). RESULTS: One hundred valid observations were analysed on 129 lesions included in the study. Lesions were excluded if subsequently restored (n = 15), teeth exfoliated (n = 2), exhibited pulpal exposure (n = 1), or failed to attend at follow-up visits (n = 11). At baseline, the shade of carious lesions was yellow (n = 22), light brown (n = 19), dark brown (n = 29), or black (n = 30). The changes in shade between baseline and 6 months were clinically perceptible to the human eye, with the mean ΔE being 12.2 (SD = 6.9). Neither tooth type, lesion severity, nor baseline shade was statistically associated with the degree of perceptible change at 6 months. CONCLUSIONS: Carious lesions exhibited clinically significant changes in colour after application of SDF + KI, primarily attributed to differences in L* of lesions over the 6 months.

Silver Compounds for Caries Management.

Silver metal and compounds have antibacterial properties, although their action's mechanisms are not fully understood. Scientists generally consider that silver disrupts the bacterial cell wall. It causes a structural change in the bacterial cell membrane and cytoplasm. It also stops deoxyribonucleic acid replication, resulting in inactivating enzymatic activity and cell death. The antimicrobial effect of silver-containing compounds relies on the release of bioactive silver ions. Hence, silver metal and compounds have been used in medicine to prevent infection for hundreds of years. Silver metal and compounds are also used as antibacterial agents in dentistry. Studies have shown that silver compounds are effective in the management of dental caries. Fluoride-containing silver compounds have been found in experiments to be beneficial at remineralising dental cavities. Silver diamine fluoride (SDF) can assist in preventing and arresting tooth cavities. The World Health Organization included SDF in its Model List of Essential Medicine for both adults and children in 2021. Clinicians also use SDF to manage dentine hypersensitivity as well as to inhibit growth of periodontal pathogens. However, traditional silver compounds cause tooth discolouration because of the silver-staining effect. These side effects of their applications depend on the amount applied and the frequency of application. Researchers are developing nanosilver fluoride and silver nanoparticles to overcome the staining. This review gives an overview of the antibacterial mechanism of silver compounds, namely silver nitrate, silver fluoride, SDF, silver nanoparticles, and nano silver fluoride for caries management. The outlook for the future development of silver compounds will be discussed.