Novel dental adhesive containing antibacterial agents and calcium phosphate nanoparticles

Remineralization of Dentin with Cerium Oxide and Its Potential Use for Root Canal Disinfection

Objective

This study was to investigate a novel antibacterial biomimetic mineralization strategy for exploring its potential application for root canal disinfection when stabilized cerium oxide was used.

Material and Methods

A biomimetic mineralization solution (BMS) consisting of cerium nitrate and dextran was prepared. Single-layer collagen fibrils, collagen membranes, demineralized dentin, and root canal system were treated with the BMS for mineralization. The mineralized samples underwent comprehensive characterization using various techniques, including transmission electron microscopy (TEM), high-resolution TEM (HRTEM), Fourier transform infrared spectroscopy (FTIR), scanning transmission electron microscopy (STEM), selected-area electron diffraction (SAED), energy-dispersive X-ray spectroscopy (EDX), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and micro-CT. Additionally, the antimicrobial properties of the BMS and the remineralized dentin were also analyzed with broth microdilution method, live/dead staining, and SEM.

Results

Cerium ions in the BMS underwent a transformation into cerium oxide nanoparticles, which were deposited in the inter- and intra-fibrillar collagen spaces through a meticulous bottom-up process. XPS analysis disclosed the presence of both Ce (III) and Ce (IV) of the generated cerium oxides. A comprehensive examination utilizing SEM and micro-CT identified the presence of cerium oxide nanoparticles deposited within the dentinal tubules and lateral canals of the root canal system. The BMS and remineralized dentin exhibited substantial antibacterial efficacy against E. faecalis, as substantiated by assessments involving the broth dilution method and live/dead staining technique. The SEM findings revealed the cell morphological changes of deceased E. faecalis.

Conclusion

This study successfully demonstrated antibacterial biomimetic mineralization as well as sealing dentinal tubules and lateral branches of root canals using cerium nitrate and dextran. This novel biomimetic mineralization could be used as an alternative strategy for root canal disinfection.

Current antibacterial agents in dental bonding systems: a comprehensive overview

Dental caries is mainly caused by oral biofilm acid, and the most common dental restoration treatment is composite dental restorations. The main cause of failure is secondary caries adjacent to the restoration. Long-term survival of dental materials is improved by the presence of antibacterial agents, which selectively inhibit bacterial growth or survival. Chemical, natural and biomaterials have been studied for their antimicrobial activities and antibacterial bonding agents have been improved. Their usage has been increased to inhibit the growth of invading and residual bacteria in the oral cavity, as biofilm accumulation increases the risk of treatment failure. In this article, the success and applications of antibacterial agents are discussed in dental bonding systems.

Silver Nanoparticles Alone or in Combination with Calcium Hydroxide Modulate the Viability, Attachment, Migration, and Osteogenic Differentiation of Human Mesenchymal Stem Cells

This study aimed to evaluate the effect of silver nanoparticles (AgNPs) alone or in combination with calcium hydroxide (Ca(OH)2) on the proliferation, viability, attachment, migration, and osteogenic differentiation of human mesenchymal stem cells (hMSCs). Different concentrations of AgNPs alone or mixed with Ca(OH)2 were prepared. Cell proliferation was measured using AlamarBlue, and hMSCs attachment to dentin disks was evaluated using scanning electron microscopy. Live-dead imaging was performed to assess apoptosis. Wound healing ability was determined using the scratch-migration assay. To evaluate osteogenic differentiation, the expression of Runt-related transcription factor (RUNX2), Transforming growth factor beta-1 (TGF-β1), Alkaline Phosphatase (ALP), and Osteocalcin (OCN) were measured using real-time reverse transcriptase polymerase chain reaction. ALP staining and activity were also performed as indicators of osteogenic differentiation. AgNPs alone seemed to favor cell attachment. Lower concentrations of AgNPs enhanced cell proliferation. AgNP groups showed markedly less apoptosis. None of the medicaments had adverse effects on wound closure. The expression of TGF-β1 was significantly upregulated in all groups, and OCN was highly expressed in the AgNP groups. AgNPs 0.06% showed the most enhanced ALP gene expression levels, activity, and marked cytochemical staining. In conclusion, AgNPs positively affect hMSCs, making them a potential biomaterial for various clinical applications.

Ceramic Nanomaterials in Caries Prevention: A Narrative Review

Ceramic nanomaterials are nanoscale inorganic metalloid solids that can be synthesised by heating at high temperatures followed by rapid cooling. Since the first nanoceramics were developed in the 1980s, ceramic nanomaterials have rapidly become one of the core nanomaterials for research because of their versatility in application and use in technology. Researchers are developing ceramic nanomaterials for dental use because ceramic nanoparticles are more stable and cheaper in production than metallic nanoparticles. Ceramic nanomaterials can be used to prevent dental caries because some of them have mineralising properties to promote the remineralisation of tooth tissue. Ceramic minerals facilitate the remineralisation process and maintain an equilibrium in pH levels to maintain tooth integrity. In addition, ceramic nanomaterials have antibacterial properties to inhibit the growth of cariogenic biofilm. Researchers have developed antimicrobial nanoparticles, conjugated ceramic minerals with antibacterial and mineralising properties, to prevent the formation and progression of caries. Common ceramic nanomaterials developed for caries prevention include calcium-based (including hydroxyapatite-based), bioactive glass-based, and silica-based nanoparticles. Calcium-based ceramic nanomaterials can substitute for the lost hydroxyapatite by depositing calcium ions. Bioactive glass-based nanoparticles contain surface-reactive glass that can form apatite crystals resembling bone and tooth tissue and exhibit chemical bonding to the bone and tooth tissue. Silica-based nanoparticles contain silica for collagen infiltration and enhancing heterogeneous mineralisation of the dentin collagen matrix. In summary, ceramic nanomaterials can be used for caries prevention because of their antibacterial and mineralising properties. This study gives an overview of ceramic nanomaterials for the prevention of dental caries.

Effect of Bioactive and Antimicrobial Nanoparticles on Properties and Applicability of Dental Adhesives

The aim of the study was to examine the applicability of bioactive and antibacterial nanoparticles to an experimental adhesive. The adhesive (60 wt% BisGMA, 15 wt% TEGDMA, 25 wt% HEMA) was mixed with combinations of 5 wt% methacryl-functionalized polyhedral oligomeric silsesquioxane (MA-POSS) and one kind of bioactive/antibacterial nanoparticles: 1 wt% core-shell silica-silver nanoparticle (SiO₂@Ag), 1 wt% bioactive glass with bismuth (BAG-Bi) or 1 wt% calcium phosphate (CAP). Pure adhesive served as control. The physicochemical (degree of conversion (DC), linear shrinkage (LS), shear and complex viscosity, water sorption (WS), sol fraction (SF)), biological (antimicrobial effect) and bioactive (mineral precipitation) properties were investigated. DC and LS remained unchanged. The combination of BAG-Bi/MA-POSS resulted in a significantly increased WS and SF compared to control. In addition, the combination of CAP/MA-POSS slightly increased the shear viscosity of the adhesive. The addition of the nanoparticles did not influence the antimicrobial effects compared to the pure adhesive. Improved mineral inducing capacity could be detected in all nanoparticle combinations. The combination of bioactive and/or antibacterial nanoparticles showed improved mineral inducing capacity, but no antibacterial properties. The material properties were not or only slightly affected.

Novel antibacterial low-shrinkage-stress resin-based cement

OBJECTIVE

A low-shrinkage-stress resin-based cement with antibacterial properties could be beneficial to create a cement with lower stress at the tooth-restoration interface, which could help to enhance the longevity of the fixed dental restoration by reducing microleakage and recurrent caries. To date, there has been no report on the development of a low-shrinkage-stress and bio-interactive cement. Therefore, the objectives of this study were to develop a novel low-shrinkage-stress resin-based cement containing dimethylaminohexadecyl methacrylate (DMAHDM) and investigate the mechanical and antibacterial properties for the first time.

METHODS

The monomers urethane dimethacrylate (UDMA) and triethylene glycol divinylbenzyl ether (TEG-DVBE) were combined and denoted as UV resin. Three cements were fabricated: (1) UV+ 0%DMAHDM (experimental control); (2) UV+ 3%DMAHDM, (3) UV+ %5DMAHDM. RelyX Ultimate cement was used as commercial control. Mechanical properties and Streptococcus mutans (S. mutans) biofilms growth on cement were evaluated.

RESULTS

The novel bio-interactive cement demonstrated excellent antibacterial and mechanical properties. Compared to commercial and experimental controls, adding DMAHDM into the UV cement significantly reduced colony forming unit (CFU) counts by approximately 7 orders of magnitude, metabolic activities from 0.29 ± 0.03 A₅₄₀/cm² to 0.01 ± 0.01 A₅₄₀/cm², and lactic acid production from 22.3 ± 0.74 mmol/L to 1.2 ± 0.27 mmol/L (n = 6) (p < 0.05). The low-shrinkage-stress cement demonstrated a high degree of conversion of around 70 %, while reducing the shrinkage stress by approximately 60%, compared to a commercial control (p < 0.05).

CONCLUSIONS

The new antibacterial low-shrinkage-stress resin-based cement provides strong antibacterial action and maintains excellent mechanical properties with reduced polymerization shrinkage stress.

CLINICAL SIGNIFICANCE

A low-shrinkage-stress resin-based cement containing DMAHDM was developed with potent antibacterial effects and promising mechanical properties. This cement may potentially enhance the longevity of fixed dental restoration such as a dental crown, inlay, onlay, and veneers through its excellent mechanical properties, low shrinkage stress, and strong antibacterial properties.

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.

Dual-functional adhesive containing amorphous calcium phosphate nanoparticles and dimethylaminohexadecyl methacrylate promoted enamel remineralization in a biofilm-challenged environment

OBJECTIVE

The cariogenic biofilm on enamel, restoration, and bonding interface is closely related to dental caries and composite restoration failure. Enamel remineralization at adhesive interface is conducive to protecting bonding interface and inhibiting secondary caries. This study intended to assess the remineralization efficiency of adhesive with dimethylaminohexadecyl methacrylate (DMAHDM) and nanoparticles of amorphous calcium phosphate (NACP) on initial caries lesion of biofilm-coated enamel.

METHODS

Artificial initial carious lesion was created via 72-hour immersion in demineralization solution and cariogenic biofilm was formed after 24-hour culture of Streptococcus mutans (S. mutans). Specimens were then divided into 4 groups: enamel control, enamel treated with NACP, DMAHDM and NACP+DMAHDM respectively. Samples next underwent 7-day cycling, 4 h in BHIS (brain heart infusion broth containing 1 % sucrose) and 20 h in AS (artificial saliva) per day. The pH of BHIS was tested daily. So did the concentration of calcium and phosphate in BHIS and AS. Live/dead staining, colony-forming unit (CFU) count, and lactic acid production of biofilms were measured 7 days later. The enamel remineralization efficiency was evaluated by microhardness testing and transverse microradiography (TMR) quantitatively.

RESULTS

Enamel of NACP+DMAHDM group demonstrated excellent remineralization effectiveness. And the NACP+DMAHDM adhesive released a great number of Ca²⁺ and PO₄^3- ions, increased pH to 5.81 via acid neutralization, decreased production of lactic acid, and reduced CFU count of S. mutans (P < 0.05).

SIGNIFICANCE

The NACP+DMAHDM adhesive would be applicable to preventing secondary caries, strengthening enamel-adhesive interface, and extending the lifespan of composite restoration.

Antimicrobial Properties of Silver-Modified Denture Base Resins

The surface quality of denture base resins allows for easy colonization by microorganisms including Candida albicans and Staphylococcus aureus, which cause major diseases of the oral cavity such as denture stomatitis. The widespread use of silver nanoparticles (AgNPs) in various fields of medicine has led to research of their possible application in dentistry, mostly in the prevention of bacterial adhesion, proliferation, and biofilm formation. The aim of the study was to synthesize cold and heat-curing denture base resins modified with AgNPs and AgCl, and evaluate the potential of the modified resins to reduce the growth of C. albicans and S.aureus. The produced material was characterized by Fourier transform infrared spectroscopy (FTIR). The antimicrobial potential of the modified material was demonstrated by the disc-diffusion method, microdilution method, and a modified microdilution method (i.e., disk-diffusion method in broth with viable counting). Spectroscopy confirmed the incorporation of biocidal materials into the structure of the denture base resins. The AgCl and AgNPs modified resins showed an antimicrobial effect. The significance of the study is in the potential therapeutic effects of the modified materials for prevention and threating staphylococci and candida in elderly patients, who are in most cases denture wearers and have a greater susceptibility to develop opportunistic infections. Modified denture base resins can significantly reduce the presence of infection at the point of contact between the denture and the mucous membrane of the prosthetic restoration. Biological tests of modified denture base resins will follow.

A Bibliometric Analysis of Electrospun Nanofibers for Dentistry

Electrospun nanofibers have been widely used in dentistry due to their excellent properties, such as high surface area and high porosity, this bibliometric study aimed to review the application fields, research status, and development trends of electrospun nanofibers in different fields of dentistry in recent years. All of the data were obtained from the Web of Science from 2004 to 2021. Origin, Microsoft Excel, VOSviewer, and Carrot² were used to process, analyze, and evaluate the publication year, countries/region, affiliations, authors, citations, keywords, and journal data. After being refined by the year of publication, document types and research fields, a total of 378 publications were included in this study, and an increasing number of publications was evident. Through linear regression calculations, it is predicted that the number of published articles in 2022 will be 66. The most published journal about electrospun dental materials is Materials Science & Engineering C-Materials for Biological Applications, among the six core journals identified, the percent of journals with Journal Citation Reports (JCR) Q1 was 60%. A total of 17.60% of the publications originated from China, and the most productive institution was the University of Sheffield. Among all the 1949 authors, the most productive author was Marco C. Bottino. Most electrospun dental nanofibers are used in periodontal regeneration, and Polycaprolactone (PCL) is the most frequently used material in all studies. With the global upsurge in research on electrospun dental materials, bone regeneration, tissue regeneration, and cell differentiation and proliferation will still be the research hotspots of electrospun dental materials in recent years. Extensive collaboration and citations among authors, institutions and countries will also reach a new level.

Preparation of a Novel Nanocomposite and Its Antibacterial Effectiveness against Enterococcus faecalis-An In Vitro Evaluation

The interest in the use of green-mediated synthesis of nanoparticles (NPs) is shown to have increased due to their biocompatibility and reduction of overall production costs. The current study aimed to evaluate a novel nanocomposite (NC) prepared by using a combination of zinc oxide, silver and chitosan with lemon extract as a cross-linking agent and assessed its antimicrobial effectiveness against Enterococcus faecalis (E. faecalis). The NPs and NC were prepared individually using a modification of previously established methods. Ananalys is of the physiochemical properties of the NC was conducted using ultraviolet-visible spectroscopy (UV-Vis) (Shimadzu Corporation, Kyoto, Japan). and transmission electron microscopy (TEM) imaging(HR-TEM; JEOL Ltd., Akishima-shi, Japan. The microbial reduction with this novel NC was evaluated by measuring the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) using a tube assay analytic technique. A time-kill assay analysis was conducted to evaluate the kinetic potential against E. faecalis at different time intervals. The novel NC showed a homogenous nanoparticle size under TEM imaging and under UV-Vis established an absorption range of 350−420 nm making it similar to its individual counterparts. The MIC and MIB were measured at 62.5 ± 20 mg/L (p < 0.05) and 250 ± 72 mg/L (p < 0.05), respectively. A time-kill assay analysis for the NC showed 5 h was required to eradicate E. faecalis. Based on the achieved results, it was seen that the novel NC using a combination of silver, zinc oxide and chitosan showed improved antimicrobial action against E. faecalis compared with its individual components under laboratory conditions. A complete eradication of 108 log units of E. faecalis at 250 mg/L occurred after a total of 5 h. These preliminary results establish the use of lemon extract-mediated silver, zinc and chitosan-based NC had an antibacterial effectiveness against E. faecalis similar to the individual counterparts used for its production under laboratory conditions.

Study on the role of nano antibacterial materials in orthodontics (a review)

Nanoparticles (NPs) are insoluble particles with a diameter of fewer than 100 nanometers. Two main methods have been utilized in orthodontic therapy to avoid microbial adherence or enamel demineralization. Certain NPs are included in orthodontic adhesives or acrylic resins (fluorohydroxyapatite, fluorapatite, hydroxyapatite, SiO2, TiO2, silver, nanofillers), and NPs (i.e., a thin layer of nitrogen-doped TiO2 on the bracket surfaces) are coated on the surfaces of orthodontic equipment. Although using NPs in orthodontics may open up modern facilities, prior research looked at antibacterial or physical characteristics for a limited period of time, ranging from one day to several weeks, and the limits of in vitro studies must be understood. The long-term effectiveness of nanotechnology-based orthodontic materials has not yet been conclusively confirmed and needs further study, as well as potential safety concerns (toxic effects) associated with NP size.

Novel calcium phosphate ion-rechargeable and antibacterial adhesive to inhibit dental caries

OBJECTIVES

This study aimed to develop an antibacterial and calcium (Ca) and phosphate (P) rechargeable adhesive and investigate the effects of dimethylaminododecyl methacrylate (DMAHDM) and nanoparticles of amorphous calcium phosphate (NACP) on dentin bonding, biofilm response, and repeated Ca and P ion recharge and re-release capability for the first time.

MATERIALS AND METHODS

Pyromellitic glycerol dimethacrylate (PMGDM), ethoxylated bisphenol A dimethacrylate (EBPADMA), 2-hydroxyethyl methacrylate (HEMA), and bisphenol A glycidyl dimethacrylate (BisGMA) formed the adhesive (PEHB). Three groups were tested: (1) Scotchbond (SBMP, 3 M) control, (2) PEHB + 30% NACP, and (3) PEHB + 30% NACP + 5% DMAHDM. Specimens were tested for dentin shear bond strength, and Ca and P ion release, recharge, and re-release. Biofilm lactic acid production and colony-forming units (CFU) on resins were analyzed.

RESULTS

The four groups had similar dentin shear bond strengths (p > 0.1). Adhesive with DMAHDM showed significant decrease in metabolic activity, lactic acid production, and biofilm CFU (p < 0.05). The adhesives containing NACP released high levels of Ca and P ions initially and after being recharged.

CONCLUSION

This study developed the first Ca and P ion-rechargeable and antibacterial adhesive, achieving strong antibacterial activity and Ca and P ion recharge and re-release for long-term remineralization.

CLINICAL RELEVANCE

Considering the restoration-tooth bonded interface being the weak link and recurrent caries at the margins being the primary reason for restoration failures, this novel calcium phosphate-rechargeable and antibacterial adhesive is promising for a wide range of tooth-restoration applications to inhibit caries.

Magnetic motion of superparamagnetic iron oxide nanoparticles- loaded dental adhesives: physicochemical/biological properties, and dentin bonding performance studied through the tooth pulpal pressure model

The limited durability of dentin bonding harshly shortens the lifespan of resin composites restorations. The controlled, dynamic movement of materials through non-contacting forces provides exciting opportunities in adhesive dentistry. We, herein, describe comprehensive investigations of a new dental adhesive with superparamagnetic iron oxide nanoparticles (SPIONs) sensitive to magnetic fields for bonding optimization. This contribution outlines a roadmap of (1) designing and tuning of an adhesive formulation containing SPIONs to enhance penetrability into etched dentin guided by magnetic-field; (2) employing a clinically relevant model of simulated hydrostatic pulpal pressure on the microtensile bond to dentin; and (3) investigating a potential antibacterial effect of the formulated adhesives, and their biocompatibility. SPION-concentration-dependency chemical and mechanical behavior was shown via the degree of conversion, ultimate tensile strength, and micro shear bond strength to dentin. The effects of SPIONs carried on a dental adhesive on the bonding strength to dentin are studied in depth by combining experiments with in vitro simulated model. The results show that under the guided magnetic field, 0.07 wt.% of SPIONs-doped adhesive increased the bond strength that surpasses the reduction caused by hydrostatic pulpal pressure. Using a magnetic guide workflow during the bonding procedures, SPIONs-doped adhesives improved dentin's adhesion without changing adhesives' physicochemical properties. This outcome addresses the key challenge of poor resin infiltration of dentin's conventional total etching during the bonding procedure. The real-time magnetic motion of dental adhesives may open new paths to enhance resin-based restorations' longevity. STATEMENT OF SIGNIFICANCE: In this study, dental adhesives containing superparamagnetic iron oxide nanoparticles (SPIONs) were developed to enhance penetrability into dentin guided by a magnetic field. The adhesives were screened for physical, chemical, antibacterial properties, and cytotoxicity. For the first time, simulated pulpal pressure was used concurrently with the magnetic field to simulate a clinical setting. This approach showed that it is feasible to overcome pulpal pressure jeopardization on bond strength when SPIONs and a magnetic field are applied. The magnetic-responsive adhesives had great potential to improve bond strength, opening new paths to enhance resin-based restorations' longevity without affecting adhesives' biological properties. The use of magnetic-responsive particles and magnetically assisted motion is a promising strategy to improve the sealing ability of dental adhesives.

Nanostructures as Targeted Therapeutics for Combating Oral Bacterial Diseases

Pathogenic oral biofilms are now recognized as a key virulence factor in many microorganisms that cause the heavy burden of oral infectious diseases. Recently, new investigations in the nanotechnology field have propelled the development of novel biomaterials and approaches to control bacterial biofilms, either independently or in combination with other substances such as drugs, bioactive molecules, and photosensitizers used in antimicrobial photodynamic therapy (aPDT) to target different cells. Moreover, nanoparticles (NPs) showed some interesting capacity to reverse microbial dysbiosis, which is a major problem in oral biofilm formation. This review provides a perspective on oral bacterial biofilms targeted with NP-mediated treatment approaches. The first section aims to investigate the effect of NPs targeting oral bacterial biofilms. The second part of this review focuses on the application of NPs in aPDT and drug delivery systems.

Antimicrobial properties of dental cements modified with zein-coated magnesium oxide nanoparticles

The aim of this study was to test the antimicrobial properties of dental cements modified with magnesium oxide (MgO) nanoparticles. Zein-modified MgO nanoparticles (zMgO) in concentrations (0.0, 0.3, 0.5, and 1.0%) were mixed with dental cements (Fuji II, Rely X Temp E, Ionoglass Cem, Es Temp NE, and System P link). Eight discs were fabricated from each zMgO-cement pair for a total of 32 specimens for each cement. Characterization of the dental cements incorporating zMgO was done by X-ray Diffraction (XRD) and Field Emission Scanning Electron Microscopy (FESEM). The antimicrobial properties of the mixtures were tested using direct contact and agar diffusion assays against Streptococcus mutans, Staphylococcus aureus, Enterococcus faecalis, and Candida albicans. Data was analyzed using two-way analysis of variance and LSD post hoc test at 0.05 significance level. XRD spectra showed sharp peaks of zMgO indicating its high crystalline nature, while the amorphous dental cements with zMgO had broad peaks. FESEM analysis showed a uniform distribution of the zMgO nanoparticles in the cement. There were significant inhibition zone values associated with all concentrations of zMgO-cement mixtures tested compared to controls (p < 0.001) with a dose-response recorded only with Fuji II. Optical density values were significantly lower in zMgO groups compared to controls for all microorganisms. The effect was most prominent with Rely X against C. albicans and S. aureus. Dental cements containing zMgO showed significant antimicrobial properties that were dependent on the specific initial cement substrate.

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Antimicrobial nanoparticles (NPs) are widely used in dental materials to improve their biological properties.

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Magnesium Oxide (MgO) NPs are novel antimicrobial agents.

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Incorporation of MgO NPs in dental cements aids in minimizing bacterial colonization at the restoration margin.

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Zein polymer facilitates the dispersion of MgO NPs and avoid its agglomeration.

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Zein polymer effectively enhances the performance of MgO NPs.

Remineralization effectiveness of adhesive containing amorphous calcium phosphate nanoparticles on artificial initial enamel caries in a biofilm-challenged environment

OBJECTIVES

Dental caries is closely associated with acid-producing bacteria, and Streptococcus mutans is one of the primary etiological agents. Bacterial accumulation and dental demineralization lead to destruction of bonding interface, thus limiting the longevity of composite. The present study investigated remineralization effectiveness of adhesive containing nanoparticles of amorphous calcium phosphate (NACP) in a stimulated oral biofilm environment.

METHODS

The enamel blocks were immersed in demineralization solution for 72 h to imitate artificial initial carious lesion and then subjected to a Streptococcus mutans biofilm for 24 h. All the samples then underwent 4-h demineralization in brain heart infusion broth with sucrose (BHIS) and 20-h remineralization in artificial saliva (AS) for 7 days. The daily pH of BHIS after 4-h incubation, lactic acid production, colony-forming unit (CFU) count, and content of calcium (Ca) and phosphate (P) in biofilm were evaluated. Meanwhile, the remineralization effectiveness of enamel was analyzed by X-ray diffraction (XRD), surface microhardness testing, transverse microradiography (TMR) and scanning electron microscopy (SEM).

RESULTS

The NACP adhesive released abundant Ca and P, achieved acid neutralization, reduced lactic acid production, and lowered CFU count (P < 0.05). Enamel treated with NACP adhesive demonstrated the best remineralization effectiveness with remineralization value of 52.29 ± 4.79% according to TMR. Better microhardness recovery of cross sections and ample mineral deposits were also observed in NACP group.

CONCLUSIONS

The NACP adhesive exhibited good performance in remineralizing initial enamel lesion with cariogenic biofilm.

SIGNIFICANCE

The NACP adhesive is promising to be applied for the protection of bonding interface, prevention of secondary caries, and longevity prolonging of the restoration.

The Benefits of Smart Nanoparticles in Dental Applications

Dentistry, as a branch of medicine, has undergone continuous evolution over time. The scientific world has focused its attention on the development of new methods and materials with improved properties that meet the needs of patients. For this purpose, the replacement of so-called "passive" dental materials that do not interact with the oral environment with "smart/intelligent" materials that have the capability to change their shape, color, or size in response to an externally stimulus, such as the temperature, pH, light, moisture, stress, electric or magnetic fields, and chemical compounds, has received much attention in recent years. A strong trend in dental applications is to apply nanotechnology and smart nanomaterials such as nanoclays, nanofibers, nanocomposites, nanobubbles, nanocapsules, solid-lipid nanoparticles, nanospheres, metallic nanoparticles, nanotubes, and nanocrystals. Among the nanomaterials, the smart nanoparticles present several advantages compared to other materials, creating the possibility to use them in various dental applications, including preventive dentistry, endodontics, restoration, and periodontal diseases. This review is focused on the recent developments and dental applications (drug delivery systems and restoration materials) of smart nanoparticles.

Review of nano-technology applications in resin-based restorative materials

OBJECTIVE

Nanotechnology has progressed significantly and particles as small as 3 nm are being employed in resin-based restorative materials to improve clinical performance. The goal of this review is to report the progress of nanotechnology in Restorative Dentistry by reviewing the advantages, limitations, and applications of resin-based restorative materials with nanoparticles.

MATERIALS AND METHODS

A literature review was conducted using PubMed/Medline, Scopus and Embase databases. In vitro, in vivo and in situ research studies published in English between 1999 and 2020, and which focused on the analysis of resin-based restorative materials containing nanoparticles were included.

RESULTS

A total of 140 studies were included in this review. Studies reported the effect of incorporating different types of nanoparticles on adhesive systems or resin composites. Mechanical, physical, and anti-bacterial properties were described. The clinical performance of resin-based restorative materials with nanoparticles was also reported.

CONCLUSIONS

The high surface area of nanoparticles exponentially increases the bioactivity of materials using bioactive nanofillers. However, the tendency of nanoparticles to agglomerate, the chemical instability of the developed materials and the decline of rheological properties when high ratios of nanoparticles are employed are some of the obstacles to overcome in the near future.

CLINICAL SIGNIFICANCE

In spite of the recent advancements of nanotechnology in resin-based restorative materials, some challenges need to be overcome before new nano-based restorative materials are considered permanent solutions to clinical problems.

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.

Rechargeable adhesive with calcium phosphate nanoparticles inhibited long-term dentin demineralization in a biofilm-challenged environment

OBJECTIVES

This study aims to investigate the long-term demineralization-inhibition capability of a rechargeable adhesive with nanoparticles of amorphous calcium phosphate (NACP) on dentin in a biofilm-challenged environment.

METHODS

The NACP adhesive was immersed in a pH 4 solution to exhaust calcium (Ca) and phosphate (P) ions and then recharged with Ca and P ions. Dentin samples were demineralized underStreptococcus mutans biofilms for 24 h and randomly divided into two groups: (1) dentin control, (2) dentin with recharged NACP adhesives. Each day, all the samples were immersed in brain heart infusion broth with 1% sucrose (BHIS) for 4 h, and then in artificial saliva (AS) for 20 h. This cycle was repeated for 10 days. The pH of BHIS, the Ca and P ions content of the BHIS and AS were measured daily. After 10 days, the lactic acid production and colony-forming units of the biofilms were tested. The changes of remineralization/demineralization were also analyzed.

RESULTS

Dentin in the control group showed further demineralization. The recharged NACP adhesive neutralized acids, increasing the pH to above 5, and released large amounts of Ca and P ions each day. The recharged NACP adhesive decreased the production of lactic acid (P < 0.05), inhibited dentin demineralization and sustained the dentin hardness in the biofilm-challenged environment, showing an excellent long-term demineralization-inhibition capability.

CONCLUSIONS

The NACP adhesive could continuously inhibit dentin demineralization in a biofilm-challenged environment by recharging with Ca and P ions.

SIGNIFICANCE

The rechargeable NACP adhesive could provide long-term dentin bond protection.

Novel Crown Cement Containing Antibacterial Monomer and Calcium Phosphate Nanoparticles

Oral biofilm accumulation at the tooth–restoration interface often leads to recurrent dental caries and restoration failure. The objectives of this study were to: (1) develop a novel bioactive crown cement containing dimethylaminohexadecyl methacrylate (DMAHDM) and nano-sized amorphous calcium phosphate (NACP), and (2) investigate the mechanical properties, anti-biofilm activity, and calcium (Ca²⁺) and phosphate (PO₄³⁻) ion release of the crown cement for the first time. The cement matrix consisted of pyromellitic glycerol dimethacrylate and ethoxylated bisphenol-A dimethacrylate monomers and was denoted PEHB resin matrix. The following cements were tested: (1) RelyX luting cement (commercial control); (2) 55% PEHB + 45% glass fillers (experimental control); (3) 55% PEHB + 20% glass + 25% NACP + 0% DMAHDM; (4) 52% PEHB + 20% glass + 25% NACP + 3% DMAHDM; (5) 51% PEHB + 20% glass + 25% NACP + 4% DMAHDM; (6) 50% PEHB + 20% glass + 25% NACP + 5% DMAHDM. Mechanical properties and ion release were measured. Streptococcusmutans (S. mutans) biofilms were grown on cements, and colony-forming units (CFUs) and other biofilm properties were measured. The novel bioactive cement demonstrated strong antibacterial properties and high levels of Ca²⁺ and PO₄³⁻ ion release to remineralize tooth lesions. Adding NACP and DMAHDM into the cement did not adversely affect the mechanical properties and dentin bonding strength. In conclusion, the novel NACP + DMAHDM crown cement has excellent potential for restoration cementation to inhibit caries by suppressing oral biofilm growth and increasing remineralization via Ca²⁺ and PO₄³⁻ ions. The NACP + DMAHDM composition may have wide applicability to other biomaterials to promote hard-tissue formation and combat bacterial infection.

Effects of a biomimetic analog-based experimental bonding system on caries-affected and sound dentin

This study compared the ultrastructure, chemical composition, and proteases activity (PA) of sound (SD) and caries-affected dentin (CAD) in the dentin hybrid layer after using an experimental bonding system containing pyromellitic dianhydride glycerol methacrylate and biomimetic analogs. The bonding system used a three step and a total-etch procedure. Polyacrylic acid (5%) and sodium trimetaphosphate (5%) were added to the primer and monocalcium phosphate monohydrate (9%), beta-tricalcium phosphate (10.5%), and calcium hydroxide (0.5%) were added to the adhesive. Transmission electron microscopy (TEM) was used to evaluate the resultant structure, particularly the adhesive-dentin and the demineralized-SD interfaces. The chemical composition was evaluated through energy-dispersive X-ray spectroscopy (EDS) and selected area electron diffraction (SAED). The PA was measured with the Coomassie Blue-G250 coloring test, and the PA data were analyzed by ANOVA. EDS identified the presence of isolated calcium phosphate nanoparticles in the demineralized region; however, the SAED analysis did not show any evidences of hydroxyapatite (HA) neoformation in SD and CAD. The biomimetic analog-based adhesive system inhibited the activities of dentin proteases immediately after treatment. Additionally, the proteolytic activity on the affected dentin resembled that of the SD. In conclusion, no HA formed in the demineralized SD and CAD although there were calcium and phosphate deposits. The experimental adhesive system inhibited dentin proteases. The present study uses a new approach to investigate the hybrid layer behavior in dentin. The experimental adhesive system was synthesized and used on sound and affected-caries dentin as the substrate to reproduce real clinical conditions.

Nano-calcium phosphate and dimethylaminohexadecyl methacrylate adhesive for dentin remineralization in a biofilm-challenged environment

OBJECTIVE

Dentin remineralization at the bonded interface would protect it from external risk factors, therefore, would enhance the longevity of restoration and combat secondary caries. Dental biofilm, as one of the critical biological factors in caries formation, should not be neglected in the assessment of caries preventive agents. In this work, the remineralization effectiveness of demineralized human dentin in a multi-species dental biofilm environment via an adhesive containing nanoparticles of amorphous calcium phosphate (NACP) and dimethylaminohexadecyl methacrylate (DMAHDM) was investigated.

METHODS

Dentin demineralization was promoted by subjecting samples to a three-species acidic biofilm containing Streptococcus mutans, Streptococcus sanguinis, Streptococcus gordonii for 24h. Samples were divided into a control group, a DMAHDM adhesive group, an NACP group, and an NACP+DMAHDM adhesive group. A bonded model containing a control-bonded group, a DMAHDM-bonded group, an NACP-bonded group, and an NACP+DMAHDM-bonded group was also included in this study. All samples were subjected to a remineralization protocol consisting of 4-h exposure per 24-h period in brain heart infusion broth plus 1% sucrose (BHIS) followed by immersion in artificial saliva for the remaining period. The pH of BHIS after 4-h immersion was measured every other day. After 14 days, the biofilm was assessed for colony-forming unit (CFU) count, lactic acid production, live/dead staining, and calcium and phosphate content. The mineral changes in the demineralized dentin samples were analyzed by transverse microradiography.

RESULTS

The in vitro experiment results showed that the NACP+DMAHDM adhesive effectively achieved acid neutralization, decreased biofilm colony-forming unit (CFU) count, decreased biofilm lactic acid production, and increased biofilm calcium and phosphate content. The NACP+DMAHDM adhesive group had higher remineralization value than the NACP or DMAHDM alone adhesive group.

SIGNIFICANCE

The NACP+DMAHDM adhesive was effective in remineralizing dentin lesion in a biofilm model. It is promising to use NACP+DMAHDM adhesive to protect bonded interface, inhibit secondary caries, and prolong the longevity of restoration.

Comparison of antibacterial effects of orthodontic composites containing different nanoparticles on Streptococcus mutans at different times

Introduction:

Plaque accumulation can cause white spot lesions. Adding nanoparticles to composites can be effective in reducing the number and function of microorganisms.

Objective:

The aim of this study was to evaluate the antibacterial effects of orthodontic composites containing different nanoparticles on Streptococcus mutans at different times.

Methods:

Hydroxyapatite, titanium oxides, zinc oxide, copper oxide and silver oxide nanoparticles were prepared at 0.5% and 1% weight concentrations. Accordingly, ten study groups and one control group were obtained. Then, 26 composite discs were prepared from each group. Strain of Streptococcus mutans was cultured, and colonies of Streptococcus mutans were counted. Further bacterial culture was swapped onto enriched Mueller-Hinton agar. The composites were placed on the culture medium, and after incubation the diameter of growth inhibition was measured. To investigate the long-term effect of nanoparticles, the colonies were counted at days 3, 15 and 30.

Results:

The results showed that 1% copper oxide and 1% silver oxide significantly reduced the number of bacteria (p< 0.05), but there was no significant difference between the other groups and control group (p> 0.05). At day three, there was a significant difference between control group and 0.5% silver oxide, 1% silver oxide and 1% copper oxide groups (p< 0.05). However, colonies had grown in all groups at day 30 but showed no significant difference with control group (p> 0.05).

Conclusion:

Addition of 1% copper oxide and 1% silver oxide has short-term antibacterial effects, so the clinical use of these nanoparticles cannot be justified.

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.

Application of Antibiotics/Antimicrobial Agents on Dental Caries

Dental caries is the most common oral disease. The bacteriological aetiology of dental caries promotes the use of antibiotics or antimicrobial agents to prevent this type of oral infectious disease. Antibiotics have been developed for more than 80 years since Fleming discovered penicillin in 1928, and systemic antibiotics have been used to treat dental caries for a long time. However, new types of antimicrobial agents have been developed to fight against dental caries. The purpose of this review is to focus on the application of systemic antibiotics and other antimicrobial agents with respect to their clinical use to date, including the history of their development, and their side effects, uses, structure types, and molecular mechanisms to promote a better understanding of the importance of microbial interactions in dental plaque and combinational treatments.

Antibacterial Properties of Nanoparticles in Dental Restorative Materials. A Systematic Review and Meta-Analysis

Background and Objectives: Nanotechnology has become a significant area of research focused mainly on increasing the antibacterial and mechanical properties of dental materials. The aim of the present systematic review and meta-analysis was to examine and quantitatively analyze the current evidence for the addition of different nanoparticles into dental restorative materials, to determine whether their incorporation increases the antibacterial/antimicrobial properties of the materials. Materials and Methods: A literature search was performed in the Pubmed, Scopus, and Embase databases, up to December 2018, following PRISMA (Preferred Reporting Items for Systematic Review and Meta-Analysis) guidelines for systematic reviews and meta-analyses. Results: A total of 624 papers were identified in the initial search. After screening the texts and applying inclusion criteria, only 11 of these were selected for quantitative analysis. The incorporation of nanoparticles led to a significant increase (p-value <0.01) in the antibacterial capacity of all the dental materials synthesized in comparison with control materials. Conclusions: The incorporation of nanoparticles into dental restorative materials was a favorable option; the antibacterial activity of nanoparticle-modified dental materials was significantly higher compared with the original unmodified materials, TiO₂ nanoparticles providing the greatest benefits. However, the high heterogeneity among the articles reviewed points to the need for further research and the application of standardized research protocols.

Cutting-edge filler technologies to release bio-active components for restorative and preventive dentistry

Advancements in materials used for restorative and preventive treatment is being directed toward "bio-active" functionality. Incorporation of filler particles that release active components is a popular method to create bio-active materials, and many approaches are available to develop fillers with the ability to release components that provide "bio-protective" or "bio-promoting" properties; e.g. metal/calcium phosphate nanoparticles, multiple ion-releasing glass fillers, and non-biodegradable polymer particles. In this review paper, recent developments in cutting-edge filler technologies to release bio-active components are addressed and summarized according to their usefulness and functions, including control of bacterial infection, tooth strengthening, and promotion of tissue regeneration.

Multifunctional antibacterial dental sealants suppress biofilms derived from children at high risk of caries

Dental sealant containing antibacterial and bioactive agents decreased biofilm formation due to the saliva of children at low and high risk of caries.

Antibacterial, physical and mechanical properties of bonding agent containing synthesized Zinc Dimethacrylate

Background

The aim of this study includes synthesis of zinc dimethacrylate ionomer (ZDMA) by a new method, incorporate it into resin bonding and evaluate its antibacterial, physical and mechanical properties.

Material and Methods

Resin adhesives containing 0 to 5% wt of ZDMA was produced and the following tests were accomplished: A: Antibacterial test: 1.Direct contact test. 2.Material aging; in both of them the bacterial colony counting were performed. B: Physical test: 1.Degree of conversion (D.C). 2.Evaluating the amount of released Zinc ion release in aqueous medium. C: Mechanical test: 1.Compressive strength test. 2.Shear bond test (enamel and dentine separately). The obtained results were statistically analyzed using One Way ANOVA and LSD post hoc test (α=0.05).

Results

The anti-bacterial test revealed that all the ZDMA containing groups significantly reduced the amount of Streptococcus Mutans bacteria. Moreover, the D.C in all ZDMA groups was enhanced. Furthermore, ion release analysis revealed noticeable stability of Zn2+ in samples, as in the 5wt.% group it was even after nine cycle of 24h wash. On the other hand, the compressive strength was significantly reduced just in the 5% ZDMA group while the other groups were superior comparing to the control. In addition, there was no significant difference among the enamel shear bond strength of the groups. However, about the dentine shear bond strength, only the 5% ZDMA group was significantly higher than the control.

Conclusions

Low percentages of ZDMA in adhesive could impart anti-bacterial efficacy without challenging its mechanical and physical properties.

Key words:Dental Resin Bonding, Zinc, Streptococcus mutans, Degree of conversion, Compressive strength.

Dentin remineralization via adhesive containing amorphous calcium phosphate nanoparticles in a biofilm-challenged environment

OBJECTIVES

The remineralization of dentin at a bonded interface would help to strengthen the bonded interface and inhibit secondary caries, and would prolong the longevity of restoration. The aim of this study was to investigate the remineralization of demineralized human dentin in a dental biofilm environment via an adhesive containing nanoparticles of amorphous calcium phosphate (NACP).

METHODS

Dentin demineralization was promoted by subjecting samples to a Streptococcus mutans acidic biofilm for 24 h. Samples were divided into a control group, a commercial fluoride-releasing adhesive group, and an NACP adhesive group. All samples were subjected to a remineralization protocol consisting of 4-h exposure per 24-h period in brain heart infusion broth plus 1% sucrose (BHIS) followed by immersion in artificial saliva for the remaining period. The pH of BHIS after 4-h immersion was measured every other day. After 10 days, the biofilm was assessed for colony-forming unit (CFU) count, lactic acid production, live/dead staining, and calcium and phosphate content. The mineral changes in the demineralized dentin samples were analyzed by transverse microradiography, hardness measurement, X-ray diffraction characterization, and scanning electron microscopy.

RESULTS

The NACP adhesive achieved acid neutralization, decreased biofilm CFU count, decreased biofilm lactic acid production, and increased biofilm calcium and phosphate content (P < 0.05). The NACP adhesive group had higher remineralization value than the commercial fluoride-releasing adhesive group (P < 0.05).

CONCLUSIONS

The NACP adhesive was effective in remineralizing dentin lesions in a biofilm model. Its ability to protect bond interface, inhibit secondary caries, and prolong the longevity of restoration is promising.

CLINICAL SIGNIFICANCE

Using NACP-containing adhesives could be recommended because of the protective ability of its hybrid layer even under a biofilm-challenged environment.

A Novel Dental Sealant Containing Dimethylaminohexadecyl Methacrylate Suppresses the Cariogenic Pathogenicity of Streptococcus mutans Biofilms

Cariogenic oral biofilms are strongly linked to dental caries around dental sealants. Quaternary ammonium monomers copolymerized with dental resin systems have been increasingly explored for modulation of biofilm growth. Here, we investigated the effect of dimethylaminohexadecyl methacrylate (DMAHDM) on the cariogenic pathogenicity of Streptococcus mutans (S. mutans) biofilms. DMAHDM at 5 mass% was incorporated into a parental formulation containing 20 mass% nanoparticles of amorphous calcium phosphate (NACP). S. mutans biofilms were grown on the formulations, and biofilm inhibition and virulence properties were assessed. The tolerances to acid stress and hydrogen peroxide stress were also evaluated. Our findings suggest that incorporating 5% DMAHDM into 20% NACP-containing sealants (1) imparts a detrimental biological effect on S. mutans by reducing colony-forming unit counts, metabolic activity and exopolysaccharide synthesis; and (2) reduces overall acid production and tolerance to oxygen stress, two major virulence factors of this microorganism. These results provide a perspective on the value of integrating bioactive restorative materials with traditional caries management approaches in clinical practice. Contact-killing strategies via dental materials aiming to prevent or at least reduce high numbers of cariogenic bacteria may be a promising approach to decrease caries in patients at high risk.

Novel endodontic sealer with dual strategies of dimethylaminohexadecyl methacrylate and nanoparticles of silver to inhibit root canal biofilms

OBJECTIVE

Endodontic treatment failures and recontamination remain a major challenge. The objectives of this study were to: (1) develop a new root canal sealer with potent and long-lasting antibiofilm effects using dimethylaminohexadecyl methacrylate (DMAHDM) and nanoparticles of silver (NAg); (2) determine the effects of incorporating DMAHDM and NAg each alone versus in combination on biofilm-inhibition efficacy; and (3) determine the effects on sealer paste flow, film thickness and sealing ability, compared to a commercial control sealer.

METHODS

Dual-cure endodontic sealers were formulated using DMAHDM mass fractions of 0%, 2.5% and 5%, and NAg mass fractions of 0.05%, 0.1% and 0.15%. The sealing ability of the sealers was measured using linear dye penetration method. Colony-forming units (CFU), live/dead assay, and polysaccharide production of biofilms grown on sealers were determined.

RESULTS

The sealer with 5% DMAHDM and 0.15% NAg yielded a flow of (22.18 ± 0.58) which was within the range of ISO recommendations and not statistically different from AH Plus control (23.3 ± 0.84) (p > 0.05). Incorporating DMAHDM and NAg did not negatively affect the film thickness and sealing properties (p > 0.05). The sealer with 5% DMAHDM and 0.15% NAg greatly reduced polysaccharide production by the biofilms, and decreased the biofilm CFU by nearly 6 orders of magnitude, compared to AH Plus and experimental controls (p < 0.05).

SIGNIFICANCE

A therapeutic root canal sealer was developed using 5% DMAHDM with biofilm-inhibition through contact-mediated mechanisms, plus 0.15% of NAg to release silver ions into the complex and difficult-to-reach root canal environment. The novel root canal sealer exerted potent antibiofilm effects and reduced biofilm CFU by 6 orders of magnitude without compromising sealer flow, film thickness and sealing ability. This method provided a promising approach to inhibit endodontic biofilms and prevent recurrent endodontic infections.

Dental remineralization via poly(amido amine) and restorative materials containing calcium phosphate nanoparticles

Tooth decay is prevalent, and secondary caries causes restoration failures, both of which are related to demineralization. There is an urgent need to develop new therapeutic materials with remineralization functions. This article represents the first review on the cutting edge research of poly(amido amine) (PAMAM) in combination with nanoparticles of amorphous calcium phosphate (NACP). PAMAM was excellent nucleation template, and could absorb calcium (Ca) and phosphate (P) ions via its functional groups to activate remineralization. NACP composite and adhesive showed acid-neutralization and Ca and P ion release capabilities. PAMAM+NACP together showed synergistic effects and produced triple benefits: excellent nucleation templates, superior acid-neutralization, and ions release. Therefore, the PAMAM+NACP strategy possessed much greater remineralization capacity than using PAMAM or NACP alone. PAMAM+NACP achieved dentin remineralization even in an acidic solution without any initial Ca and P ions. Besides, the long-term remineralization capability of PAMAM+NACP was established. After prolonged fluid challenge, the immersed PAMAM with the recharged NACP still induced effective dentin mineral regeneration. Furthermore, the hardness of pre-demineralized dentin was increased back to that of healthy dentin, indicating a complete remineralization. Therefore, the novel PAMAM+NACP approach is promising to provide long-term therapeutic effects including tooth remineralization, hardness increase, and caries-inhibition capabilities.

Poly(amido amine) and rechargeable adhesive containing calcium phosphate nanoparticles for long-term dentin remineralization

OBJECTIVES

The objective of the present study was to investigate long-term dentin remineralization via the combination of poly(amido amine) (PAMAM) with a novel rechargeable adhesive containing nanoparticles of amorphous calcium phosphate (NACP).

METHODS

The NACP adhesive was immersed in lactic acid at pH 4 to exhaust its calcium (Ca) and phosphate (P) ion release, and then recharged with Ca and P ions. Dentin samples were pre-demineralized with 37% phosphoric acid, and then divided into four groups: (1) dentin control, (2) dentin treated with PAMAM, (3) dentin with recharged NACP adhesive, (4) dentin with PAMAM + recharged NACP adhesive. In group (2) and (4), the PAMAM-coated dentin was immersed in phosphate-buffered saline with vigorous shaking for 77 days to accelerate any detachment of the PAMAM macromolecules from the demineralized dentin. Samples were treated with a cyclic remineralization/demineralization regimen for 21 days.

RESULTS

After 77 days of fluid flow challenge, the immersed PAMAM still retained its nucleation template function. The recharged NACP adhesive possessed sustained ion re-release and acid-neutralization capability, both of which did not decrease with repeated recharge and re-release cycles. The immersed PAMAM with the recharged NACP adhesive achieved long-term dentin remineralization, and restored dentin hardness to that of healthy dentin.

CONCLUSIONS

The PAMAM + NACP adhesive completely remineralizes pre-demineralized dentin even after long-term fluid challenges and provides long-term remineralization to protect tooth structures.

CLINICAL SIGNIFICANCE

The novel PAMAM + NACP adhesive provides long-term bond protection and caries inhibition to increase the longevity of resin-based restorations.

Novel bioactive root canal sealer with antibiofilm and remineralization properties

OBJECTIVES

(1) To develop a novel bioactive root canal sealer with antibiofilm and remineralization properties using dimethylaminohexadecyl methacrylate (DMAHDM) and nanoparticles of amorphous calcium phosphate (NACP); (2) investigate the effects on E. faecalis biofilm inhibition, sealer flow and sealing ability, compared with an epoxy-resin-based sealer AH Plus; and (3) investigate the calcium (Ca) and phosphate (P) ion release from the sealers.

METHODS

A series of dual-cure endodontic sealers were formulated with DMAHDM and NACP at 5% and 20% by mass, respectively. Flow properties and sealing ability of the sealers were measured. Colony-forming units (CFU), live/dead assay, and polysaccharide production of biofilms on sealers were determined. Ca and P ion releases from the sealers were measured.

RESULTS

The new sealer containing 20% NACP and 5% DMAHDM yielded a paste flow of (28.99 ± 0.69) mm, within the range of ISO recommendations. The sealing properties of the sealer with 5% DMAHDM and 20% NACP were similar to a commercial control (p > 0.05). The sealer with DMAHDM decreased E. faecalis biofilm CFU by more than 4 orders of magnitude, compared to AH plus and experimental controls. The sealer with 20% NACP and 5% DMAHDM had relatively high levels of Ca and P ion release necessary for remineralization.

CONCLUSIONS

A new bioactive endodontic sealer was developed with strong antibiofilm activity against E. faecalis biofilms and high levels of Ca and P ion release for remineralization, without compromising the paste flow and sealing properties.

CLINICAL SIGNIFICANCE

The bioactive antibacterial and remineralizing root canal sealer is promising to inhibit E. faecalis biofilms to prevent endodontic treatment failure and secondary endodontic infections, while releasing high levels of Ca and P ions that could remineralize and strengthen the tooth structures and potentially prevent future root fractures and teeth extractions.

Synthesis and characterization of silver nanoparticle-loaded amorphous calcium phosphate microspheres for dental applications

The goals of this work were (1) to synthesize composite nanostructures comprised of amorphous calcium phosphate (ACP) loaded with silver nanoparticles using a spray pyrolysis method and (2) to demonstrate their potential for use in dental adhesives. Release of silver ions from these nanostructures could provide antibacterial activity, while release of calcium and phosphate ions could promote tooth remineralization. Precursor solutions were prepared with varying silver concentrations corresponding to 5, 10, and 15 mol% of the calcium content, then sprayed into a furnace (550 °C) as droplets with a mean diameter near 2 μm. In this process, each droplet is converted into a single solid microsphere via rapid heating. The synthesized particles were collected using a polymeric filter installed at the end of the reaction zone. Different quantities (2, 5, and 10 wt%) of the nanocomposite material were mixed with a commercially available dental adhesive (Single Bond, 3M ESPE) which was then polymerized into discs for incubation in a solution simulating cariogenic conditions. Release of silver, calcium and phosphorus ions into the solution was measured for 1 month. The nanostructures of ∼10 nm silver nanoparticles embedded into 100 nm to 2 μm ACP particles demonstrated good dispersion in the adhesive resin blend, which in application would shield surrounding tissues from direct contact with silver. The composite nanoparticles provided a quick initial release of ions after which the concentration of calcium, phosphorous, and silver in the incubation solution remained constant or increased slightly. The dispersibility and ion release of the new nanostructures may offer potential for use in dental materials to achieve anti-bacterial and remineralization effects.

In vitro antibacterial activity of self-etch bio-active dental adhesives after artificial aging

Purpose:

The aims to evaluate the antibacterial effect of different bioactive component containing dental adhesives before and after artificial aging.

Materials and methods:

Two bio-active adhesives; Clearfil Protect Bond and FL Bond II, two non-bioactive adhesives, Clearfil SE Bond and Clearfil S3 Bond were used for this study. Antibacterial activities of the fresh and aged samples against Streptococcus mutans were investigated with Direct Contact Test. Data were analyzed with Kruskal Wallis and Mann Whitney U multiple comparison tests.

Results:

For fresh samples FL Bond II and Clearfil Protect Bond exhibit similar antibacterial effect but Clearfil Protect Bond showed significantly higher antibacterial effect after aging the samples (p<0.05).

Conclusion:

The incorporation of bio-active antibacterial components into adhesive systems may be considered as a fundamental component in inhibiting residual Streptococcus mutans when considering the antibacterial effect of fresh samples of bio-active adhesives.

Toward dental caries: Exploring nanoparticle-based platforms and calcium phosphate compounds for dental restorative materials

Millions of people worldwide suffer from a toothache due to tooth cavity, and often permanent tooth loss. Dental caries, also known as tooth decay, is a biofilm-dependent infectious disease that damages teeth by minerals loss and presents a high incidence of clinical restorative polymeric fillings (tooth colored fillings). Until now, restorative polymeric fillings present no bioactivity. The complexity of oral biofilms contributes to the difficulty in developing effective novel dental materials. Nanotechnology has been explored in the development of bioactive dental materials to reduce or modulate the activities of caries-related bacteria. Nano-structured platforms based on calcium phosphate and metallic particles have advanced to impart an anti-caries potential to restorative materials. The bioactivity of these platforms induces prevention of mineral loss of the hard tooth structure and antibacterial activities against caries-related pathogens. It has been suggested that this bioactivity could minimize the incidence of caries around restorations (CARS) and increase the longevity of such filling materials. The last few years witnessed growing numbers of studies on the preparation evaluations of these novel materials. Herein, the caries disease process and the role of pathogenic caries-related biofilm, the increasing incidence of CARS, and the recent efforts employed for incorporation of bioactive nanoparticles in restorative polymer materials as useful strategies for prevention and management of caries-related-bacteria are discussed. We highlight the status of the most advanced and widely explored interaction of nanoparticle-based platforms and calcium phosphate compounds with an eye toward translating the potential of these approaches to the dental clinical reality.

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Current progress and future applications of functional nanoparticles and remineralizing compounds incorporated in dental direct restorative materials.

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Overview of the antibacterial and remineralizing mechanisms presenting direct and indirect implications on the tooth mineral loss.

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These investigations, although in the initial phase of evidence are necessary and their results are encouraging and open the doors to future clinical studies that will allow the therapeutic value of nanotechnology-based restorative materials to be established.

Human In Situ Study of the effect of Bis(2-Methacryloyloxyethyl) Dimethylammonium Bromide Immobilized in Dental Composite on Controlling Mature Cariogenic Biofilm

Cariogenic oral biofilms cause recurrent dental caries around composite restorations, resulting in unprosperous oral health and expensive restorative treatment. Quaternary ammonium monomers that can be copolymerized with dental resin systems have been explored for the modulation of dental plaque biofilm growth over dental composite surfaces. Here, for the first time, we investigated the effect of bis(2-methacryloyloxyethyl) dimethylammonium bromide (QADM) on human overlying mature oral biofilms grown intra-orally in human participants for 7⁻14 days. Seventeen volunteers wore palatal devices containing composite specimens containing 10% by mass of QADM or a control composite without QADM. After 7 and 14 days, the adherent biofilms were collected to determine bacterial counts via colony-forming unit (CFU) counts. Biofilm viability, chronological changes, and percentage coverage were also determined through live/dead staining. QADM composites caused a significant inhibition of Streptococcus mutans biofilm formation for up to seven days. No difference in the CFU values were found for the 14-day period. Our findings suggest that: (1) QADM composites were successful in inhibiting 1⁻3-day biofilms in the oral environment in vivo; (2) QADM significantly reduced the portion of the S. mutans group; and (3) stronger antibiofilm activity is required for the control of mature long-term cariogenic biofilms. Contact-killing strategies using dental materials aimed at preventing or at least reducing high numbers of cariogenic bacteria seem to be a promising approach in patients at high risk of the recurrence of dental caries around composites.

Tuning Nano-Amorphous Calcium Phosphate Content in Novel Rechargeable Antibacterial Dental Sealant

Dental sealants with antibacterial and remineralizing properties are promising for caries prevention among children and adolescents. The application of nanotechnology and polymer development have enabled nanoparticles of amorphous calcium phosphate (NACP) and dimethylaminohexadecyl methacrylate (DMAHDM) to emerge as anti-caries strategies via resin-based dental materials. Our objectives in this study were to (1) incorporate different mass fractions of NACP into a parental rechargeable and antibacterial sealant; (2) investigate the effects on mechanical performance, and (3) assess how the variations in NACP concentration would affect the calcium (Ca) and phosphate (PO₄) ion release and re-chargeability over time. NACP were synthesized using a spray-drying technique and incorporated at mass fractions of 0, 10, 20 and 30%. Flexural strength, flexural modulus, and flowability were assessed for mechanical and physical performance. Ca and PO₄ ion release were measured over 70 days, and three ion recharging cycles were performed for re-chargeability. The impact of the loading percentage of NACP upon the sealant’s performance was evaluated, and the optimized formulation was eventually selected. The experimental sealant at 20% NACP had flexural strength and flexural modulus of 79.5 ± 8.4 MPa and 4.2 ± 0.4 GPa, respectively, while the flexural strength and flexural modulus of a commercial sealant control were 70.7 ± 5.5 MPa (p > 0.05) and 3.3 ± 0.5 GPa (p < 0.05), respectively. A significant reduction in flow was observed in the experimental sealant at 30% NACP (p < 0.05). Increasing the NACP mass fraction increased the ion release. The sealant formulation with NACP at 20% displayed desirable mechanical performance and ideal flow and handling properties, and also showed high levels of long-term Ca and PO₄ ion release and excellent recharge capabilities. The findings provide fundamental data for the development of a new generation of antibacterial and rechargeable Ca and PO₄ dental sealants to promote remineralization and inhibit caries.

Protein-repelling adhesive resin containing calcium phosphate nanoparticles with repeated ion-recharge and re-releases

OBJECTIVES

The objectives were to develop a calcium (Ca) and phosphate (P) ion-rechargeable and protein-repellent adhesive containing nanoparticles of amorphous calcium phosphate (NACP) and 2-methacryloyloxyethyl phosphorylcholine (MPC), and investigate the MPC effects on ion recharge and re-releases for the first time.

METHODS

Pyromellitic glycerol dimethacrylate and ethoxylated bisphenol-A dimethacrylate were used to fabricate adhesive PEHB. Six adhesives were tested: (1) Scotchbond (SBMP); (2) PEHB, (3) PEHB + 20%NACP; (4) PEHB + 30%NACP; (5) PEHB + 20%NACP+3%MPC; (6) PEHB + 30%NACP+3%MPC. Dentin shear bond strength, Ca/P ion release, recharge and re-release, and protein adsorption were measured. A microcosm biofilm model was tested for lactic-acid production and colony-forming units (CFU).

RESULTS

Adding NACP + MPC did not negatively affect dentin bond strength (p > 0.1). With increasing the number of recharge/re-release cycles, the Ca/P ion re-release reached similarly higher levels (p > 0.1), indicating long-term remineralization capability. One recharge enabled the adhesives to have continued re-releases for 21 days. Incorporation of 3% MPC yielded 10-fold decrease in protein adsorption, and 1-2 log decrease in biofilm CFU.

CONCLUSIONS

The new rechargeable adhesive with MPC + 30%NACP greatly reduced protein adsorption, biofilm growth and lactic acid. Incorporation of MPC did not compromise the excellent Ca/P ion release, rechargeability, and dentin bond strength.

CLINICAL SIGNIFICANCE

Novel bioactive adhesive containing MPC + NACP is promising to repel proteins and bacteria, and inhibit secondary caries at the restoration margins. The method of NACP + MPC to combine CaP-recharge and protein-repellency is applicable to the development of a new generation of materials including composites and cements to suppress oral biofilms and plaque formation and protect tooth structures.