Antibacterial effect and bond strength of a modified dental adhesive containing the peptide nisin

Addition of nisin to high-viscosity glass-ionomer cement: a comparative in vitro study on antibacterial and physical properties

PURPOSE

Nisin is a lantibiotic effective against Gram-positive microorganisms such as Streptococcus mutans. The study aimed to determine the effect of the addition of nisin to high-viscosity glass-ionomer cement (HVGIC) on its antibacterial activity, setting time, surface microhardness, and compressive strength.

METHODS

1 and 3% w/w nisin were added to HVGIC before mixing. Unmodified HVGIC was the control. Agar disc diffusion, direct contact test, and scanning electron microscopy (SEM) analysis were used to evaluate antibacterial activity against S. mutans. Setting time, surface microhardness, and compressive strength were measured using Gilmore needle apparatus, digital microhardness tester, and universal testing machine, respectively. Statistical analysis included Student's t test, one-way ANOVA with Tamhane's post hoc test, and repeated-measures ANOVA.

RESULTS

As evidenced by the agar disc diffusion (p < 0.001), direct contact tests (p = 0.025), and SEM analysis of the S. mutans cell count and cell surface area (p = 0.049 and 0.003), 3% nisin had the strongest antibacterial activity. There was a dose-dependent increase in setting time (p = 0.005) and surface microhardness (p = 0.006), with no significant difference in compressive strength compared to control.

CONCLUSION

The addition of 3% nisin to HVGIC enhances the antibacterial action against S. mutans and surface microhardness without adversely affecting setting time and compressive strength.

Antibacterial Activity of the Vancomycin and Cefotaxime-Incorporated Total Etch Adhesive System - An In Vitro Study

Background

Marginal failure at the resin dentin interface promotes biofilm formation, which further leads to secondary caries and hypersensitivity. This likelihood also increases if residual bacteria are present following cavity preparation. In order to achieve a proper biological seal without jeopardizing bonding, efforts were made to functionalize the adhesive system with antibacterial activity. Aim and objectives: To appraise the antibacterial activity of a total-etch adhesive system against S. mutans with and without incorporation of antibiotics Vancomycin and Cefotaxime.

Materials and Method

A commercially available 5th-generation total-etch bonding agent (Te-Econorm) was used. S. mutans broth had been standardized and streaked over Muller-Hinton agar culture medium and round wells about 6 mm in diameter were made in the centre of the agar plates. Each experimental group comprised 10 samples, which include: Group 1 - 30µg Cefotaxime, Group 2- 30µg Cefotaxime + Bonding agent, Group 3- 30µg Vancomycin, Group 4- 30µg Vancomycin + Bonding agent, Group 5- Bonding agent, and Group 6- No material. Inoculated culture plates were examined for the zone of inhibition after incubation at 37° C for 24 hours.

Results

There was a significant difference in the mean diameter of zone of inhibition (p=0.000), with the maximum exhibited by Group 4, followed by Group 3 and Group 2. The least zone of inhibition was exhibited by Groups 1 and 5. The negative control showed no zone of inhibition.

Conclusion

The combination of Vancomycin and bonding agent had superior antibacterial activity against S. mutans in comparison to cefotaxime and bonding agent.

Antimicrobial Peptides Targeting Streptococcus mutans: Current Research on Design, Screening and Efficacy

Antimicrobial peptides (AMPs) are small-molecule peptides that play a vital role in the nonspecific immune defense system of organisms. They mainly kill microorganisms by physically destroying the cell membrane and causing the leakage of contents. AMPs have attracted much attention as potential alternatives to antibiotics due to their low susceptibility to resistance. Streptococcus mutans (S. mutans) is one of the main causative agents of human dental caries. The design, screening, and efficacy evaluation of AMPs targeting S. mutans offer new possibilities for the prevention and treatment of oral diseases, especially dental caries, in the future. This article reviews AMPs from different sources that have inhibitory effects on S. mutans, discusses the mechanism of action of AMPs against S. mutans biofilms, and focuses on the research progress of screening methods, design modification, and biological activity evaluation of AMPs. We hope to provide insights and reference value for the development of new biologics.

Peptides in Dentistry: A Scoping Review

Currently, it remains unclear which specific peptides could be appropriate for applications in different fields of dentistry. The aim of this scoping review was to scan the contemporary scientific papers related to the types, uses and applications of peptides in dentistry at the moment. Literature database searches were performed in the following databases: PubMed/MEDLINE, Scopus, Web of Science, Embase, and Scielo. A total of 133 articles involving the use of peptides in dentistry-related applications were included. The studies involved experimental designs in animals, microorganisms, or cells; clinical trials were also identified within this review. Most of the applications of peptides included caries management, implant osseointegration, guided tissue regeneration, vital pulp therapy, antimicrobial activity, enamel remineralization, periodontal therapy, the surface modification of tooth implants, and the modification of other restorative materials such as dental adhesives and denture base resins. The in vitro and in vivo studies included in this review suggested that peptides may have beneficial effects for treating early carious lesions, promoting cell adhesion, enhancing the adhesion strength of dental implants, and in tissue engineering as healthy promotors of the periodontium and antimicrobial agents. The lack of clinical trials should be highlighted, leaving a wide space available for the investigation of peptides in dentistry.

Engineering peptide-polymer hybrids for targeted repair and protection of cervical lesions

By 2060, nearly 100 million people in the U.S. will be over age 65 years. One-third of these older adults will have root caries, and nearly 80% will have dental erosion. These conditions can cause pain and loss of tooth structure that interfere with eating, speaking, sleeping, and quality of life. Current treatments for root caries and dental erosion have produced unreliable results. For example, the glass-ionomer-cement or composite-resin restorations used to treat these lesions have annual failure rates of 44% and 17%, respectively. These limitations and the pressing need to treat these conditions in the aging population are driving a focus on microinvasive strategies, such as sealants and varnishes. Sealants can inhibit caries on coronal surfaces, but they are ineffective for root caries. For healthy, functionally independent elders, chlorhexidine varnish applied every 3 months inhibits root caries, but this bitter-tasting varnish stains the teeth. Fluoride gel inhibits root caries, but requires prescriptions and daily use, which may not be feasible for some older patients. Silver diamine fluoride can both arrest and inhibit root caries but stains the treated tooth surface black. The limitations of current approaches and high prevalence of root caries and dental erosion in the aging population create an urgent need for microinvasive therapies that can: (a) remineralize damaged dentin; (b) inhibit bacterial activity; and (c) provide durable protection for the root surface. Since cavitated and non-cavitated root lesions are difficult to distinguish, optimal approaches will treat both. This review will explore the multi-factorial elements that contribute to root surface lesions and discuss a multi-pronged strategy to both repair and protect root surfaces. The strategy integrates engineered peptides, novel polymer chemistry, multi-scale structure/property characterization and predictive modeling to develop a durable, microinvasive treatment for root surface lesions.

Investigation of drug resistance of caries-related streptococci to antimicrobial peptide GH12

Dental caries is associated with caries-related streptococci and antimicrobial agents have been widely used for caries control, but troubled by antibiotic resistance. This study aimed to investigate the intrinsic and acquired resistance of caries-related streptococci to antimicrobial peptide GH12, which was proven promising for caries control, and preliminarily explore the phenotypic changes and whole genome of stable acquired resistant strains. In this study, susceptibility assays and resistance assays were performed, followed by stability assays of resistance, to evaluate the intrinsic resistance and the potential resistance of caries-related streptococci. Then, the phenotypic changes of the stable acquired resistant strain were explored. The whole genome of the resistant strain was sequenced and analyzed by second-generation and third-generation high-throughput sequencing technologies. Streptococcus gordonii and Streptococcus sanguinis were intrinsically resistant to GH12 compared to cariogenic Streptococcus mutans. Acquired GH12 resistance in one S. sanguinis and four S. mutans clinical strains was transient but stable in one S. mutans strain (COCC33-14). However, acquired resistance to daptomycin (DAP) and chlorhexidine in all strains was stable. Furthermore, the COCC33-14 showed cross-resistance to DAP and delayed growth rates and a lower population. However, no drug-resistant gene mutation was detected in this strain, but 6 new and 5 missing genes were found. Among them, annotation of one new gene (gene 1782|COCC33-14R) is related to the integral component of the membrane, and one missing gene rpsN is associated with the metabolism and growth of bacteria. The results indicate that stable resistant mutants of caries-related streptococci could hardly be selected by exposure to consecutive sublethal GH12, but the risk still existed. Resistance in COCC33-14R is mainly related to changes in the cell envelope.

Development of an Antibacterial Dentin Adhesive

Nisin is a peptide that possesses potent antibacterial properties. This study evaluated the antibacterial activity of a nisin-doped adhesive against Streptococcus mutans, as well as its degree of conversion and microtensile bond strength (μTBS) to dentin. Nisin was added to the adhesive Adper Single Bond 2 (3M ESPE), resulting in four groups: Control Group (Single Bond 2); Group 1% (1 wt% nisin-incorporated), Group 3% (3 wt% nisin-incorporated) and Group 5% (5 wt% nisin-incorporated). Antibacterial activity against S. mutans was evaluated using colony-forming unit counts (CFU). The degree of conversion was tested using FTIR. Forty human teeth were restored for μTBS evaluation. Data were statistically analyzed with ANOVA and Tukey tests at α = 0.05. The nisin-doped adhesives, for all concentrations, exhibited a significant inhibition of the growth of S. mutans (p < 0.05); Incorporation of 5% and 3% nisin decreased the degree of conversion of the adhesive (p < 0.05). The μTBS (in MPa): Control Group—38.3 ± 2.3A, Group 1%—35.6 ± 2.1A, Group 3%—27.1 ± 1.6B and Group 5%—22.3 ± 1.0C. Nisin-doped adhesives exerted a bactericidal effect on S. mutans. The μTBS and degree of conversion of adhesive were not affected after incorporation of 1% nisin.

Remineralization of human dentin type I collagen fibrils induced by carboxylated polyamidoamine dendrimer/amorphous calcium phosphate nanocomposite: an in vitro study

Intrafibrillar mineralization of type I collagen fibrils is of great significance in dental remineralization, which is the key of caries prevention and treatment. Herein, two substances that have the remineralization ability, carboxylated polyamidoamine dendrimer (PAMAM-COOH) and nano-sized amorphous calcium phosphate (n-ACP) were combined to synthesize a novel nanomaterial, carboxylated polyamidoamine dendrimer/amorphous calcium phosphate nanocomposite (PAMAM-COOH/ACP). This article aims to evaluate the remineralization effect of PAMAM-COOH/ACP of dentin type I collagen fibrils in vitro. Fluorescence labeling technique was innovatively used to observe and evaluate the remineralization effect. PAMAM-COOH/ACP showed superior remineralization ability of human dentin type I collagen fibrils, especially the intrafibrillar remineralization. Therefore, the novel nanomaterial PAMAM-COOH/ACP is promising to prevent and treat various diseases caused by dentin demineralization and to improve various dental materials.

Microbial approaches for the assessment of toothpaste efficacy against oral species: A method comparison

Antibacterial properties of toothpastes enable chemical plaque control in limited‐access tooth regions that are mechanically not sufficiently reached by toothbrushes. Therefore, this study aimed to compare different microbial methods to assess antimicrobial toothpaste properties and evaluate different toothpastes in terms of their antibacterial efficacy against different oral microorganisms in an in vitro setting. Six toothpaste suspensions with varying antibacterial supplements were applied to a multispecies biofilm model (Actinomyces oris, Candida albicans, Fusobacterium nucleatum, Streptococcus oralis, and Streptococcus mutans) as well as to each microorganism. A culture method was used to assess the anti‐biofilm effects and two different agar diffusion assays were performed for testing the antimicrobial effect on each microorganism. The measurements of the culture and diffusion analyses were statistically normalized and compared and toothpastes were ranked according to their antimicrobial efficacy. The results of both agar diffusion assays showed a high correlation across all tested species (Spearman correlation coefficients ρ_s > 0.95). The results of the multispecies biofilm model, however, substantially differed in its assessment of antibacterial properties (ρ_s ranging from 0.22 to 0.87) compared to the results of both diffusion assays. Toothpastes with amine fluoride (with and without stannous fluoride), and toothpastes with triclosan resulted in the highest antimicrobial efficacy. Activated carbon supplements in toothpastes were comparable in their antimicrobial action to the negative control NaCl. The appropriate selection of a broad range of oral microorganisms seems crucial when testing the chemical impact of toothpaste and toothpaste supplements.

Physical/Mechanical and Antibacterial Properties of Orthodontic Adhesives Containing Calcium Phosphate and Nisin

Enamel demineralization around orthodontic adhesive is a common esthetic concern during orthodontic treatment. The aim of this study was to prepare orthodontic adhesives containing monocalcium phosphate monohydrate (MCPM) and nisin to enable mineralizing and antibacterial actions. The physicomechanical properties and the inhibition of S. mutans growth of the adhesives with added MCPM (5, 10 wt %) and nisin (5, 10 wt %) were examined. Transbond XT (Trans) was used as the commercial comparison. The adhesive containing a low level of MCPM showed significantly higher monomer conversion (42–62%) than Trans (38%) (p < 0.05). Materials with additives showed lower monomer conversion (p < 0.05), biaxial flexural strength (p < 0.05), and shear bond strength to enamel than those of a control. Additives increased water sorption and solubility of the experimental materials. The addition of MCPM encouraged Ca and P ion release, and the precipitation of calcium phosphate at the bonding interface. The growth of S. mutans in all the groups was comparable (p > 0.05). In conclusion, experimental orthodontic adhesives with additives showed comparable conversion but lesser mechanical properties than the commercial material. The materials showed no antibacterial action, but exhibited ion release and calcium phosphate precipitation. These properties may promote remineralization of the demineralized enamel.

Recent Advances in the Development of Antimicrobial and Antifouling Biocompatible Materials for Dental Applications

The risk of secondary bacterial infections resulting from dental procedures has driven the design of antimicrobial and antifouling dental materials to curb pathogenic microbial growth, biofilm formation and subsequent oral and dental diseases. Studies have investigated approaches based primarily on contact-killing or release-killing materials. These materials are designed for addition into dental resins, adhesives and fillings or as immobilized coatings on tooth surfaces, titanium implants and dental prosthetics. This review discusses the recent developments in the different classes of biomaterials for antimicrobial and antifouling dental applications: polymeric drug-releasing materials, polymeric and metallic nanoparticles, polymeric biocides and antimicrobial peptides. With modifications to improve cytotoxicity and mechanical properties, contact-killing and anti-adhesion materials show potential for incorporation into dental materials for long-term clinical use as opposed to short-lived antimicrobial release-based coatings. However, extended durations of biocompatibility testing, and adjustment of essential biomaterial features to enhance material longevity in the oral cavity require further investigations to confirm suitability and safety of these materials in the clinical setting. The continuous exposure of dental restorative and regenerative materials to pathogenic microbes necessitates the implementation of antimicrobial and antifouling materials to either replace antibiotics or improve its rational use, especially in the day and age of the ever-increasing problem of antimicrobial resistance.

The Bond Strength and Antibacterial Activity of the Universal Dentin Bonding System: A Systematic Review and Meta-Analysis

Streptococcus mutans (S. mutans) is a group of viridans mostly located in oral flora among the wide and biodiverse biofilm. It plays a significant role not only in caries formation but also triggering intracerebral haemorrhage. The durable and stable bond interface, besides bacteria elimination, is one of the crucial factors influencing the resin composite restoration performance. This study aimed to evaluate universal adhesives (UAs) with regard to in vitro bond strength to dentin, and the inhibition of the S. mutans growth and compare them with UAs modified with antimicrobial agents through a systematic review and meta-analysis. Two reviewers performed a literature search up to April 2021 in 5 electronic databases: PubMed MedLine, Scielo, ISI Web of Science, Scopus, and EMBASE. Only in vitro studies reporting the effect of modifying UAs with antimicrobial agents on the bond strength to dentin and/or on the inhibition of the S. mutans were included. Analyses were carried out using Review Manager Software version 5.3.5 (The Nordic Cochrane Centre, The Cochrane Collaboration, Copenhagen, Denmark). The methodological quality of each in vitro study was evaluated following the parameters of a previous systematic review. A total of 1716 potentially relevant publications were recognized. After reviewing the title and abstract, 16 studies remained in the systematic review. From these, a total of 3 studies were included in the meta-analysis. Since data from the studies included in the antimicrobial outcome included zero values, they could not be meta-analysed. Including 0 values in the analysis will lead to several biases in the analysis, so these data were discarded. The antibacterial effect against S. mutans of UAs modified with antimicrobial agents was higher than the non-modified adhesive systems. Within the limitations of the present study, the bond strength of UAs to dentin could be improved by using antimicrobial agents. The UAs modified with antibacterial agents showed a decrease in the viability of S. mutans biofilm, among the adhesives tested. However, there are not enough valid data on antibacterial properties of modified UAs; therefore, more well-designed research on these materials is needed.

Bioinspired multifunctional adhesive system for next generation bio-additively designed dental restorations

Resin-based composite has overtaken dental amalgam as the most popular material for the repair of lost or damaged tooth structure. In spite of the popularity, the average composite lifetime is about half that of amalgam restorations. The leading cause of composite-restoration failure is decay at the margin where the adhesive is applied. The adhesive is intended to seal the composite/tooth interface, but the adhesive seal to dentin is fragile and readily degraded by acids, enzymes and other oral fluids. The inherent weakness of this material system is attributable to several factors including the lack of antimicrobial properties, remineralization capabilities and durable mechanical performance - elements that are central to the integrity of the adhesive/dentin (a/d) interfacial seal. Our approach to this problem offers a transition from a hybrid to a biohybrid structure. Discrete peptides are tethered to polymers to provide multi-bio-functional adhesive formulations that simultaneously achieve antimicrobial and remineralization properties. The bio-additive materials design combines several functional properties with the goal of providing an adhesive that will serve as a durable barrier to recurrent decay at the composite/tooth interface. This article provides an overview of our multi-faceted approach which uses peptides tethered to polymers and new polymer chemistries to achieve the next generation adhesive system - an adhesive that provides antimicrobial properties, repair of defective dentin and enhanced mechanical performance.

Antimicrobial peptides for the prevention and treatment of dental caries: A concise review

The objective of this study was to perform a comprehensive review of the use of antimicrobial peptides for the prevention and treatment of dental caries. The study included publications in the English language that addressed the use of antimicrobial peptides in the prevention and treatment of caries. These publications were also searchable on PubMed, Web of Science, Embase, Scopus, the Collection of Anti-Microbial Peptides and the Antimicrobial Peptide Database. A total of 3,436 publications were identified, and 67 publications were included. Eight publications reported seven natural human antimicrobial peptides as bactericidal to Streptococcus mutans. Fifty-nine publications reported 43 synthetic antimicrobial peptides developed to mimic natural antimicrobial peptides, fusing peptides with functional sequences and implementing new designs. The 43 synthetic antimicrobial peptides were effective against Streptococcus mutans, and nine peptides specifically targeted Streptococcus mutans. Ten antimicrobial peptides had an affinity for hydroxyapatite to prevent bacterial adhesion. Six antimicrobial peptides were also antifungal. Four antimicrobial peptides promoted remineralisation or prevented the demineralisation of teeth by binding calcium to hydroxyapatite. In conclusion, this study identified 67 works in the literature that reported seven natural and 43 synthetic antimicrobial peptides for the prevention and treatment of caries. Most of the antimicrobial peptides were bactericidal, and some prevented bacterial adhesion. A few antimicrobial peptides displayed remineralising properties with hydroxyapatite.

Bibliometric Analysis of Literature Published on Antibacterial Dental Adhesive from 1996-2020

This study aimed to investigate the current state of research on antibacterial dental adhesives. The interest in this field can be drawn from an increasing number of scholarly works in this area. However, there is still a lack of quantitative measurement of this topic. The main aim of this study was to consolidate the research published on the antibacterial adhesive from 1996 to 2020 in Web of Science indexed journals. The bibliometric method, a quantitative study of investigating publishing trends and patterns, was used for this study. The result has shown that a gradual increase in research was found, whereby a substantial increase was observed from 2013. A total of 248 documents were published in 84 journals with total citations of 5107. The highly cited articles were published mainly in Q1 category journals. Most of the published articles were from the USA, China, and other developed countries; however, some developing countries contributed as well. The authorship pattern showed an interdisciplinary and collaborative approach among researchers. The thematic evaluation of keywords along with a three-factor analysis showed that 'antibacterial adhesives' and 'quaternary ammonium' have been used commonly. This bibliometric analysis can provide direction not only to researchers but also to funding organizations and policymakers.

Monomer conversion, biaxial flexural strength, apatite forming ability of experimental dual-cured and self-adhesive dental composites containing calcium phosphate and nisin

The aim was to develop dual-cured, self-adhesive composites containing monocalcium phosphate monohydrate (MCPM, 8 or 4 wt%) and nisin (6 or 3 wt%) with added adhesive monomer. The effect of additives on monomer conversion (MC), biaxial flexural strength (BFS), dentin shear bond strength (SBS), and surface apatite formation were examined. All experimental composites showed light-activated MC (70-75%) higher than the commercial self-adhesive composite (Vertise Flow; VF, 65%). The additives reduced BFS of the composites from 217 to 133 MPa. SBS of the experimental composites (2-6 MPa) was lower than that of VF (12 MPa). Rising MCPM level enabled apatite-like crystals precipitated on the surface of composites after immersion in simulated body fluid for 4 weeks. The additives showed negligible effect on MC and SBS. Rising level of additives reduced strength of the composites but the values were still higher than that required by the standard.

Harnessing biomolecules for bioinspired dental biomaterials

Dental clinicians have relied for centuries on traditional dental materials (polymers, ceramics, metals, and composites) to restore oral health and function to patients. Clinical outcomes for many crucial dental therapies remain poor despite many decades of intense research on these materials. Recent attention has been paid to biomolecules as a chassis for engineered preventive, restorative, and regenerative approaches in dentistry. Indeed, biomolecules represent a uniquely versatile and precise tool to enable the design and development of bioinspired multifunctional dental materials to spur advancements in dentistry. In this review, we survey the range of biomolecules that have been used across dental biomaterials. Our particular focus is on the key biological activity imparted by each biomolecule toward prevention of dental and oral diseases as well as restoration of oral health. Additional emphasis is placed on the structure-function relationships between biomolecules and their biological activity, the unique challenges of each clinical condition, limitations of conventional therapies, and the advantages of each class of biomolecule for said challenge. Biomaterials for bone regeneration are not reviewed as numerous existing reviews on the topic have been recently published. We conclude our narrative review with an outlook on the future of biomolecules in dental biomaterials and potential avenues of innovation for biomaterial-based patient oral care.

Emerging Contact-Killing Antibacterial Strategies for Developing Anti-Biofilm Dental Polymeric Restorative Materials

Polymeric materials are the first choice for restoring tooth cavities, bonding tooth-colored fillings, sealing root canal systems, and many other dental restorative applications. However, polymeric materials are highly susceptible to bacterial attachment and colonization, leading to dental diseases. Many approaches have been investigated to minimize the formation of biofilms over polymeric restorative materials and at the tooth/material interfaces. Among them, contact-killing compounds have shown promising results to inhibit dental biofilms. Contact-killing compounds can be immobilized within the polymer structure, delivering a long-lasting effect with no leaching or release, thus providing advantages compared to release-based materials. This review discusses cutting-edge research on the development of contact-killing compounds in dental restorative materials to target oral pathogens. Contact-killing compounds in resin composite restorations, dental adhesives, root canal sealers, denture-based materials, and crown cements have all demonstrated promising antibacterial properties. Contact-killing restorative materials have been found to effectively inhibit the growth and activities of several oral pathogens related to dental caries, periodontal diseases, endodontic, and fungal infections. Further laboratory optimization and clinical trials using translational models are needed to confirm the clinical applicability of this new generation of contact-killing dental restorative materials.

Comparative Evaluation of the Inhibitory Potential of Synthetic N-Heterocycles, Cu/Fe3O4@SiO2 Nanocomposites and Some Natural Products against Non-Resistant and Antibiotic-Resistant Acinetobacter baumannii

Background: Acinetobacter baumannii is a common infectious agent in hospitals. New antimicrobial agents are identified and prepared to combat these bacterial pathogens. In this context, the blocking potentials of a series of synthesized N-heterocyclic compounds, Cu/Fe3O4@SiO2 nanocomposites, glycine, poly-L-lysine, nisin and hydroalcoholic extracts of Trachyspermum ammi, Curcuma longa and green tea catechins were evaluated against non-resistant and multidrug-resistant strains of A. baumannii. Methods: Solutions of heterocyclic derivatives and hydroalcoholic extracts of Trachyspermum ammi, Curcuma longa and green tea catechins were prepared at initial concentration of 10240 μg ml-1 in 10% DMSO. Other compounds were dissolved in water at the same concentrations. Their in vitro inhibitory activity was assessed by determination of IZD, MIC and MBC values. Results: Glycine, poly-L-lysine, nisin, Curcuma longa and green tea catechins extracts, and thiazoles 3a, 3d and 3f were ineffective at their initial concentrations. Heterocyclic derivatives 7a-f, 3c, 3e and 3h, Cu/Fe3O4@SiO2 nanocomposites and Trachyspermum ammi extract could block the growth of bacterial strains with IZDs (7.40-15.51 mm), MICs (32-1024 µg ml-1) and MBCs (128-2048 µg ml-1). Conclusion: Among synthetic chemicals and natural products, the best antimicrobial effects were recorded with (E)-2-(5-acetyl-4-methylthiazol-2-yl)-2-(thiazolidin-2-ylidene)acetonitrile (7b) and the extract of Trachyspermum ammi. It is imperative that their toxic and histopathologic effects were assessed in future researches. It is predicted that the essential oil of Trachyspermum ammi will improve its antibacterial activities.

Improving mechanical and antibacterial properties of PMMA via polyblend electrospinning with silk fibroin and polyethyleneimine towards dental applications

Poly(methylmethacrylate) (PMMA) is a widely used material in dental applications, particularly as denture resins. Due to thermally unstable and wet oral cavity, the implanted PMMA based resins occasionally deform and grow bacterial biofilms at the interface between oral cavity and the biomaterial. Several strategies attempted earlier to improve the bacterial resistance and mechanical performance of PMMA. Poly(ethyleneimine) (PEI) is a hyperbranched cationic polymer shown earlier to improve antibacterial activity of resins but do not improve mechanical properties of the resins alone, while silk fibroin (SF) is a natural biopolymer with unique material properties. In this study, we combined SF and PEI towards development of antibacterial and mechanically superior PMMA based materials towards overcoming its drawbacks. Using polyblend electrospinning to combine SF, PEI and PMMA, we successfully developed intrinsically antibacterial and mechanically reinforced nanofiber mats. We propose that the resulting nanofiber mats have the potential to be incorporated into PMMA based denture resin materials to overcome the problems of patients and improve their quality of life.

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Polyblend electrospinning PMMA with SF and PEI leads to striking decrease in fiber diameter.

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PMMA+SF+PEI fibers have superior mechanical properties compared to PMMA fibers.

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PMMA+SF+PEI fibers intrinsically showed antibacterial activity against a pathogenic bacteria with in oral microflora.

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PMMA+SF+PEI fibers could potentially be used in PMMA based denture materials.

Antimicrobial Peptide-Polymer Conjugates for Dentistry

Bacterial adhesion and growth at the composite/adhesive/tooth interface remain the primary cause of dental composite restoration failure. Early colonizers, including Streptococcus mutans, play a critical role in the formation of dental caries by creating an environment that reduces the adhesive's integrity. Subsequently, other bacterial species, biofilm formation, and lactic acid from S. mutans demineralize the adjoining tooth. Because of their broad spectrum of antibacterial activity and low risk for antibiotic resistance, antimicrobial peptides (AMPs) have received significant attention to prevent bacterial biofilms. Harnessing the potential of AMPs is still very limited in dentistry-a few studies have explored peptide-enabled antimicrobial adhesive copolymer systems using mainly nonspecific adsorption. In the current investigation, to avoid limitations from nonspecific adsorption and to prevent potential peptide leakage out of the resin, we conjugated an AMP with a commonly used monomer for dental adhesive formulation. To tailor the flexibility between the peptide and the resin material, we designed two different spacer domains. The spacer-integrated antimicrobial peptides were conjugated to methacrylate (MA), and the resulting MA-AMP monomers were next copolymerized into dental adhesives as AMP-polymer conjugates. The resulting bioactivity of the polymethacrylate-based AMP conjugated matrix activity was investigated. The antimicrobial peptide conjugated to the resin matrix demonstrated significant antimicrobial activity against S. mutans. Secondary structure analyses of conjugated peptides were applied to understand the activity differential. When mechanical properties of the adhesive system were investigated with respect to AMP and cross-linking concentration, resulting AMP-polymer conjugates maintained higher compressive moduli compared to hydrogel analogues including polyHEMA. Overall, our result provides a robust approach to develop a fine-tuned bioenabled peptide adhesive system with improved mechanical properties and antimicrobial activity. The results of this study represent a critical step toward the development of peptide-conjugated dentin adhesives for treatment of secondary caries and the enhanced durability of dental composite restorations.

A universal adhesive incorporating antimicrobial peptide nisin: effects on Streptococcus mutans and saliva-derived multispecies biofilms

For purpose of enhancing the antibacterial activity of a universal adhesive, the antimicrobial peptide nisin was incorporated into Single Bond Universal and its antibacterial effect on Streptococcus mutans monospecific biofilms and saliva-derived multispecies biofilms was studied. Nisin was incorporated into Single Bond Universal and the antibacterial activity was examined by confocal laser scanning microscopy (CLSM), reverse transcription-quantitative polymerase chain reaction (qRT-PCR), phenol-sulfuric acid method and lactate dehydrogenase enzymatic method. The bonding properties were tested by microtensile bond strength (μTBS) and degree of conversion (DC). Data were analyzed by one-way analysis of variance (ANOVA) and least significant difference multiple comparison tests (P < 0.05). The Single Bond Universal incorporated with 3% (w/v) nisin could significantly inhibit the growth of the S. mutans monospecific biofilms (P< 0.01) and decrease the expression of genes related to extracellular polysaccharide (EPS) synthesis (gtfB, gtfC, gtfD and spaP) and acidogenicity (ldh) (P < 0.05). 3% (w/v) nisin-incorporated Single Bond Universal could also inhibit the growth of saliva-derived multispecies biofilms and decrease the excretion of EPS and lactic acid ( P< 0.05). μTBS and DC of 3% (w/v) nisin-incorporated Single Bond Universal did not deteriorate obviously (P > 0.05). In conclusion, 3% (w/v) nisin-incorporated Single Bond Universal substantially inhibited the growth of both S. mutans monospecific and saliva-derived multispecies biofilms without compromising the bonding properties.

Polymeric and inorganic nanoscopical antimicrobial fillers in dentistry

Failure of dental treatments is mainly due to the biofilm accumulated on the dental materials. Many investigations have been conducted on the advancements of antimicrobial dental materials. Polymeric and inorganic nanoscopical agents are capable of inhibiting microorganism proliferation. Applying them as fillers in dental materials can achieve enhanced microbicidal ability. The present review provides a broad overview on the state-of-the-art research in the field of antimicrobial fillers which have been adopted for incorporation into dental materials over the last 5 years. The antibacterial agents and applications are described, with the aim of providing information for future investigations. STATEMENT OF SIGNIFICANCE: Microbial infection is the primary cause of dental treatment failure. The present review provides an overview on the state-of-art in the field of antimicrobial nanoscopical or polymeric fillers that have been applied in dental materials. Trends in the biotechnological development of these antimicrobial fillers over the last 5 years are reviewed to provide a backdrop for further advancement in this field of research.

Peptide Mediated Antimicrobial Dental Adhesive System

The most common cause for dental composite failures is secondary caries due to invasive bacterial colonization of the adhesive/dentin (a/d) interface. Innate material weakness often lead to an insufficient seal between the adhesive and dentin. Consequently, bacterial by-products invade the porous a/d interface leading to material degradation and dental caries. Current approaches to achieve antibacterial properties in these materials continue to raise concerns regarding hypersensitivity and antibiotic resistance. Herein, we have developed a multi-faceted, bio-functionalized approach to overcome the vulnerability of such interfaces. An antimicrobial adhesive formulation was designed using a combination of antimicrobial peptide and a ε-polylysine resin system. Effector molecules boasting innate immunity are brought together with a biopolymer offering a two-fold biomimetic design approach. The selection of ε-polylysine was inspired due to its non-toxic nature and common use as food preservative. Biomolecular characterization and functional activity of our engineered dental adhesive formulation were assessed and the combinatorial formulation demonstrated significant antimicrobial activity against Streptococcus mutans. Our antimicrobial peptide-hydrophilic adhesive hybrid system design offers advanced, biofunctional properties at the critical a/d interface.