Formulation of pH-sensitive chlorhexidine-loaded/mesoporous silica nanoparticles modified experimental dentin adhesive

Physicochemical and biological properties of dental materials and formulations with silica nanoparticles: A narrative review

OBJECTIVE

Silica nanoparticles (SNPs) have been extensively studied and used in different dental applications to promote improved physicochemical properties, high substance loading efficiency, in addition to sustained delivery of substances for therapeutic or preventive purposes. Therefore, this study aimed to review the SNPs applications in nanomaterials and nanoformulations in dentistry, discussing their effect on physicochemical properties, biocompatibility and ability to nanocarry bioactive substances.

DATA RESOURCES

Literature searches were conducted on PubMed, Web of Science, and Scopus databases to identify studies examining the physicochemical and biological properties of dental materials and formulations containing SNPs. Data extraction was performed by one reviewer and verified by another STUDY SELECTION: A total of 50 were reviewed. In vitro studies reveal that SNPs improved the general properties of dental materials and formulations, such as microhardness, fracture toughness, flexural strength, elastic modulus and surface roughness, in addition to acting as efficient nanocarriers of substances, such as antimicrobial, osteogenic and remineralizing substances, and showed biocompatibility CONCLUSIONS: SNPs are biocompatible, improve properties of dental materials and serve as effective carriers for bioactive substances CLINICAL SIGNIFICANCE: Overall, SNPs are a promising drug delivery system that can improve dental materials biological and physicochemical and aesthetic properties, increasing their longevity and clinical performance. However, more studies are needed to elucidate SNPs short- and long-term effects in the oral cavity, mainly on in vivo and clinical studies, to prove their effectiveness and safety.

Formulation of arginine-loaded mesoporous silica nanoparticles (Arg@MSNs) modified orthodontic adhesive

OBJECTIVES

The objective of this study was to synthesize arginine loaded mesoporous silica nanoparticles (Arg@MSNs), develop a novel orthodontic adhesive using Arg@MSNs as modifiers, and investigate the adhesive performance, antibacterial activity, and biocompatibility.

METHODS

Arg@MSNs were synthesized by immobilizing arginine into MSNs and characterized using transmission electron microscope (TEM), dynamic light scattering (DLS), and Fourier Transform Infrared Spectrometer (FT-IR). Arg@MSNs were incorporated into Transbond XT adhesive with different mass fraction to form functional adhesives. The degree of conversion (DC), arginine release behavior, adhesive performance, antibacterial activity against Streptococcus mutans biofilm, and cytotoxicity were comprehensively evaluated.

RESULTS

TEM, DLS, and FT-IR characterizations confirmed the successful preparation of Arg@MSNs. The incorporation of Arg@MSNs did not significantly affect DC and exhibited clinically acceptable bonding strength. Compared to the commercial control, the Arg@MSNs modified adhesives greatly suppressed the metabolic activity and polysaccharide production while increased the biofilm pH values. The cell counting kit (CCK)-8 test indicated no cytotoxicity.

CONCLUSIONS

The novel orthodontic adhesive containing Arg@MSNs exhibited significantly enhanced antibacterial activities and inhibitory effects on acid production compared to the commercial adhesive without compromising their bonding strength or biocompatibility.

CLINICAL SIGNIFICANCE

The novel orthodontic adhesive containing Arg@MSNs exhibits potential clinical benefits in preventing demineralization of enamel surfaces around or beneath orthodontic brackets due to its enhanced antibacterial activities and acid-producing inhibitory effects.

Recent updates and feasibility of nanodrugs in the prevention and eradication of dental biofilm and its associated pathogens-A review

OBJECTIVES

Dental biofilm is one of the most prevalent diseases in humans, which is mediated by multiple microorganisms. Globally, half of the human population suffers from dental biofilm and its associated diseases. In recent trends, nano-formulated drugs are highly attractive in the treatment of dental biofilms. However, the impact of different types of nanodrugs on the dental biofilm and its associated pathogens have not been published till date. Thus, this review focuses on the recent updates, feasibility, mechanisms, limitations, and regulations of nanodrugs applications in the prevention and eradication of dental biofilm.

STUDY SELECTION, DATA AND SOURCES

A systematic search was conducted in PubMed/Google Scholar/Scopus over the past five years covering the major keywords "nanodrugs, metallic nanoparticles, metal oxide nanoparticles, natural polymers, synthetic polymers, biomaterials, dental biofilm, antibiofilm mechanism, dental pathogens", are reviewed in this study. Nearly, 100 scientific articles are selected in this relevant topic published between 2019 and 2023. Data from the selected studies dealing with nanodrugs used for biofilm treatment was qualitatively analyzed.

CONCLUSIONS

The nanodrugs such as silver nanoparticles, gold nanoparticles, selenium nanoparticles, zinc oxide nanoparticles, copper oxide nanoparticles, titanium oxide nanoparticles, hydroxyapatite nanoparticles and these inorganic nanoparticles incorporated polymer-based nanocomposites, organic/inorganic nanoparticles mediated antimicrobial photodynamic therapy exhibits an excellent antibacterial and antibiofilm activity towards dental pathogens. Finally, this review highlights that bioinspired nanodrugs will be very useful to control the dental biofilm and its associated diseases.

CLINICAL SIGNIFICANCE

Microbial influence on the oral environment is unavoidable; therefore, curing such dental biofilms and pathogens is essential for the impactful reflection of applying biocompatible treatments. In this direction, the current review explains the demand for the nanodrug in inhibiting biofilms for the effective exploration of employing treatments.

A glycol chitosan derivative with extrafibrillar demineralization potential for self-etch dentin bonding

OBJECTIVES

Extrafibrillar demineralization is an etching technique that removes only minerals from around the collagen fibrils for resin infiltration. The intrafibrillar minerals are left intact to avoid their replacement by water that is hard for adhesive resin monomers to displace. The present work reported the synthesis of a water-soluble methacryloyloxy glycol chitosan-EDTA conjugate (GCE-MA) and evaluated its potential as an extrafibrillar demineralization agent for self-etch dentin bonding.

METHODS

Glycol chitosan-EDTA was functionalized with a methacryloyloxy functionality. Conjugation was confirmed using Fourier transform-infrared spectroscopy. The GCE-MA was used to prepare experimental self-etch primers. Extrafibrillar demineralization of the primers was evaluated with scaning electron microscopy and transmission electron microscopy. The feasibility of this new self-etch bonding approach was evaluated using microtensile bond strength testing and inhibition of dentin gelatinolytic activity. The antibacterial activity and cytotoxicity of GCE-MA were also analyzed.

RESULTS

Conjugation of EDTA and the methacryloyloxy functionality to glycol chitosan was successful. The functionalized conjugate was capable of extrafibrillar demineralization of mineralized collagen fibrils. Tensile bond strength of the experimental self-etch primer to dentin was comparable to that of phosphoric acid-etched dentin and the commercial self-etch primer Clearfil SE Bond 2. The GCE-MA also inhibited soluble rhMMP-9. In-situ zymography detected minimal fluorescence in hybrid layers conditioned with the experimental primer. The GCE-MA was noncytotoxic and possessed antibacterial activities against planktonic bacteria.

SIGNIFICANCE

Synthesis of GCE-MA brought into fruition a self-etch conditioner that selectively demineralizes the extrafibrillar mineral component of dentin. A self-etch primer prepared with GCE-MA achieved bond strengths comparable to commercial reference adhesive systems.

Silica nanoparticles containing nano-silver and chlorhexidine respond to pH to suppress biofilm acids and modulate biofilms toward a non-cariogenic composition

OBJECTIVES

Dental caries is caused by acids from biofilms. pH-sensitive nanoparticle carriers could achieve improved targeted effectiveness. The objectives of this study were to develop novel mesoporous silica nanoparticles carrying nanosilver and chlorhexidine (nMS-nAg-Chx), and investigate the inhibition of biofilms as well as the modulation of biofilm to suppress acidogenic and promote benign species for the first time.

METHODS

nMS-nAg was synthesized via a modified sol-gel method. Carboxylate group functionalized nMS-nAg (COOH-nMS-nAg) was prepared and Chx was added via electrostatic interaction. Minimal inhibitory concentration (MIC), inhibition zone, and growth curves were evaluated. Streptococcus mutans (S. mutans), Streptococcus gordonii (S. gordonii), and Streptococcus sanguinis (S. sanguinis) formed multispecies biofilms. Metabolic activity, biofilm lactic acid, exopolysaccharides (EPS), and TaqMan real-time polymerase chain reaction (RT-PCR) were tested. Biofilm structures and biomass were observed by scanning electron microscopy (SEM) and live/dead bacteria staining.

RESULTS

nMS-nAg-Chx possessed pH-responsive properties, where Chx release increased at lower pH. nMS-nAg-Chx showed good biocompatibility. nMS-nAg-Chx exhibited a strong antibacterial function, reducing biofilm metabolic activity and lactic acid as compared to control (p < 0.05, n = 6). Moreso, biofilm biomass was dramatically suppressed in nMS-nAg-Chx groups. In control group, there was an increasing trend of S. mutans proportion in the multispecies biofilm, with S. mutans reaching 89.1% at 72 h. In sharp contrast, in nMS-nAg-Chx group of 25 μg/mL, the ratio of S. mutans dropped to 43.7% and the proportion of S. gordonii and S. sanguinis increased from 19.8% and 10.9 to 69.8% and 56.3%, correspondingly.

CONCLUSION

pH-sensitive nMS-nAg-Chx had potent antibacterial effects and modulated biofilm toward a non-cariogenic tendency, decreasing the cariogenic species nearly halved and increasing the benign species approximately twofold. nMS-nAg-Chx is promising for applications in mouth rinse and endodontic irrigants, and as fillers in resins to prevent caries.

Multifunctional mesoporous silica nanoparticles for biomedical applications

Mesoporous silica nanoparticles (MSNs) are recognized as a prime example of nanotechnology applied in the biomedical field, due to their easily tunable structure and composition, diverse surface functionalization properties, and excellent biocompatibility. Over the past two decades, researchers have developed a wide variety of MSNs-based nanoplatforms through careful design and controlled preparation techniques, demonstrating their adaptability to various biomedical application scenarios. With the continuous breakthroughs of MSNs in the fields of biosensing, disease diagnosis and treatment, tissue engineering, etc., MSNs are gradually moving from basic research to clinical trials. In this review, we provide a detailed summary of MSNs in the biomedical field, beginning with a comprehensive overview of their development history. We then discuss the types of MSNs-based nanostructured architectures, as well as the classification of MSNs-based nanocomposites according to the elements existed in various inorganic functional components. Subsequently, we summarize the primary purposes of surface-functionalized modifications of MSNs. In the following, we discuss the biomedical applications of MSNs, and highlight the MSNs-based targeted therapeutic modalities currently developed. Given the importance of clinical translation, we also summarize the progress of MSNs in clinical trials. Finally, we take a perspective on the future direction and remaining challenges of MSNs in the biomedical field.

Antibacterial and physical properties of resin cements containing MgO nanoparticles

Cariogenic bacteria and dental plaque biofilm at prosthesis margins are considered a primary risk factor for failed restorations. Resin cement containing antibacterial agents can be beneficial in controlling bacteria and biofilm. This work aimed to evaluate the impact of incorporating magnesium oxide nanoparticles (MgONPs) as an antibacterial filler into dual-cure resin cement on bacteriostatic activity and physical properties, including mechanical, bonding, and physicochemical properties, as well as performance when subjected to a 5000-times thermocycling regimen. Experimental resin cements containing MgONPs of different mass fractions (0, 2.5%, 5%, 7.5% and 10%) were developed. Results suggested that the inclusion of MgONPs markedly improved the materials' bacteriostatic effect against Streptococcus mutans without compromising the physical properties when its addition reached 7.5 wt%. The mechanical properties of the specimens did not significantly decline after undergoing aging treatment, except for the flexural properties. In addition, the cements displayed good bonding performance and the material itself was not prone to cohesive fracture in the failure mode analysis. Furthermore, MgONPs possibly have played a role in decelerating material aging during thermocycling and enhancing bonding fastness in the early stage of cementation, which requires further investigation. Overall, developing MgONPs-doped resin cements can be a promising strategy to improve the material's performance in inhibiting cariogenic bacteria at restoration margins, in order to achieve a reduction in biofilm-associated secondary caries and a prolonged restoration lifespan.

Evaluation of drug release, monomer conversion and surface properties of resin composites containing chlorhexidine-loaded mesoporous and nonporous hydroxyapatite nanocarriers

The aim of this study was to evaluate drug release, degree of conversion (DC), and surface properties of resin composites containing chlorhexidine (CHX)-loaded mesoporous (mHAP) and nonporous hydroxyapatite (HAP) nanocarrier. CHX loaded mHAP and HAP, or CHX without nanocarrier was added into the resin composite in 1% and 5% concentrations. After characterization of experimental materials with XRD, EDX, FT-IR, and SEM, the CHX release on the 1st, 7th, 30th, and 120th days were evaluated by UV-vis spectroscopy. DC, surface roughness, and surface hardness of the samples were also evaluated. The data was statistically analyzed. While mHAP groups released significantly higher CHX on the 30th day (p < .05), there was no statistically significant difference between the HAP and mHAP groups on the 120th day (p > .05). DCs of all groups were similar (p > .05). While mHAP and HAP groups containing 5% CHX showed significantly higher roughness than the other groups (p < .05), no statistically significant difference was observed between the other groups (p > .05). The 1% and 5% CHX groups without nanocarrier showed significantly lower surface hardness (p < .05). However, no statistically significant difference was observed between the other groups in terms of surface hardness (p > .05). A controlled CHX release was achieved by mHAP and HAP nanocarriers for 120 days. The nanocarrier addition up to 5% did not negatively affect the DC and the surface hardness which is one of the surface properties of the resin composites. Although the addition of 5% nanocarrier to the resin composite increased the surface roughness, while adding 1% of these nanocarriers did not change.

Overview of Antimicrobial Biodegradable Polyester-Based Formulations

As the clinical complications induced by microbial infections are known to have life-threatening side effects, conventional anti-infective therapy is necessary, but not sufficient to overcome these issues. Some of their limitations are connected to drug-related inefficiency or resistance and pathogen-related adaptive modifications. Therefore, there is an urgent need for advanced antimicrobials and antimicrobial devices. A challenging, yet successful route has been the development of new biostatic or biocide agents and biomaterials by considering the indisputable advantages of biopolymers. Polymers are attractive materials due to their physical and chemical properties, such as compositional and structural versatility, tunable reactivity, solubility and degradability, and mechanical and chemical tunability, together with their intrinsic biocompatibility and bioactivity, thus enabling the fabrication of effective pharmacologically active antimicrobial formulations. Besides representing protective or potentiating carriers for conventional drugs, biopolymers possess an impressive ability for conjugation or functionalization. These aspects are key for avoiding malicious side effects or providing targeted and triggered drug delivery (specific and selective cellular targeting), and generally to define their pharmacological efficacy. Moreover, biopolymers can be processed in different forms (particles, fibers, films, membranes, or scaffolds), which prove excellent candidates for modern anti-infective applications. This review contains an overview of antimicrobial polyester-based formulations, centered around the effect of the dimensionality over the properties of the material and the effect of the production route or post-processing actions.

Calcium Phosphate Delivery Systems for Regeneration and Biomineralization of Mineralized Tissues of the Craniofacial Complex

Calcium phosphate (CaP)-based materials have been extensively used for mineralized tissues in the craniofacial complex. Owing to their excellent biocompatibility, biodegradability, and inherent osteoconductive nature, their use as delivery systems for drugs and bioactive factors has several advantages. Of the three mineralized tissues in the craniofacial complex (bone, dentin, and enamel), only bone and dentin have some regenerative properties that can diminish due to disease and severe injuries. Therefore, targeting these regenerative tissues with CaP delivery systems carrying relevant drugs, morphogenic factors, and ions is imperative to improve tissue health in the mineralized tissue engineering field. In this review, the use of CaP-based microparticles, nanoparticles, and polymer-induced liquid precursor (PILPs) amorphous CaP nanodroplets for delivery to craniofacial bone and dentin are discussed. The use of these various form factors to obtain either a high local concentration of cargo at the macroscale and/or to deliver cargos precisely to nanoscale structures is also described. Finally, perspectives on the field using these CaP materials and next steps for the future delivery to the craniofacial complex are presented.

The application of mesoporous silica nanoparticles as a drug delivery vehicle in oral disease treatment

Mesoporous silica nanoparticles (MSNs) hold promise as safer and more effective medication delivery vehicles for treating oral disorders. As the drug's delivery system, MSNs adapt to effectively combine with a variety of medications to get over systemic toxicity and low solubility issues. MSNs, which operate as a common nanoplatform for the co-delivery of several compounds, increase therapy effectiveness and show promise in the fight against antibiotic resistance. MSNs offer a noninvasive and biocompatible platform for delivery that produces long-acting release by responding to minute stimuli in the cellular environmen. MSN-based drug delivery systems for the treatment of periodontitis, cancer, dentin hypersensitivity, and dental cavities have recently been developed as a result of recent unparalleled advancements. The applications of MSNs to be embellished by oral therapeutic agents in stomatology are discussed in this paper.

Mechanical and antibacterial efficacy of photo-sonodynamic therapy via methylene blue-loaded nanoparticles over dental implants for treating peri-implantitis

AIM

This study aimed to evaluate the mechanical (i.e., flexural modulus [FM], flexural strength [FS], and surface roughness [R_a]) and antibacterial efficacy of photo-sonodynamic therapy via methylene blue-loaded poly(D,L-lactide-co-glycolide) nanoparticles (MB-loaded PLGA NPs) over dental implants for potential treatment of peri-implantitis.

METHODS

PLGA NPs were synthesized via a solvent displacement method. After the synthesis and confirmation of MB-loaded PLGA NPs via physical (Scanning Electron Microscope [SEM]) and chemical characterization (Fourier transform infrared spectroscopy [FTIR]), the mature dental biofilm of Porphyromonas gingivalis was produced over the surfaces of dental implants. Then, the bacterial viability assessment of the following five study groups was performed: group-I (diode laser treatment); group-II (PDT/MB-loaded PLGA NPs treatment; group-III (ultrasound treatment); group-IV (ultrasound/PLGA NPs-MB treatment); and group-V: control group included the samples without any treatment. Finally, the FS, FM, and R_a of the samples was assessed.

RESULTS

Under the SEM, the NPs were spherical homogeneous particles having round morphology ranging approximately 100 nm in size without aggregation. The FTIR spectra of PLGA NPs and MB-loaded PLGA NPs demonstrated absorption peaks at approximately 1000 cm^-1 to 1200 cm^-1 and around 1500 cm^-1 to 1750 cm^-1. The greatest level of P. gingivalis killing was exhibited by ultrasound/MB-loaded PLGA-NPs-treated samples. The FS was statistically significantly greater for control group samples than any other group (i.e., 100.28 MPa; p<0.05). The FM and R_a ranged between 3.31 and 3.58 GPa and between 0.18 and 0.20 µm without any statistically significant difference between the control and experimental groups (p>0.05), respectively.

CONCLUSION

Within the limitations of this study, the application of photo-sonodynamic therapy via MB-loaded PLGA NPs demonstrated the greatest antibacterial activity against P. gingivalis without deteriorating the surfaces and compromising the mechanical properties of dental implants.

Current Strategies to Control Recurrent and Residual Caries with Resin Composite Restorations: Operator- and Material-Related Factors

This review addresses the rationale of recurrent and/or residual caries associated with resin composite restorations alongside current strategies and evidence-based recommendations to arrest residual caries and restrain recurrent caries. The PubMed and MEDLINE databases were searched for composite-associated recurrent/residual caries focusing on predisposing factors related to materials and operator’s skills; patient-related factors were out of scope. Recurrent caries and fractures are the main reasons for the failure of resin composites. Recurrent and residual caries are evaluated differently with no exact distinguishment, especially for wall lesions. Recurrent caries correlates to patient factors, the operator’s skills of cavity preparation, and material selection and insertion. Material-related factors are significant. Strong evidence validates the minimally invasive management of deep caries, with concerns regarding residual infected dentin. Promising technologies promote resin composites with antibacterial and remineralizing potentials. Insertion techniques influence adaptation, marginal seal, and proximal contact tightness. A reliable diagnostic method for recurrent or residual caries is urgently required. Ongoing endeavors cannot eliminate recurrent caries or precisely validate residual caries. The operator’s responsibility to precisely diagnose original caries and remaining tooth structure, consider oral environmental conditions, accurately prepare cavities, and select and apply restorative materials are integral aspects. Recurrent caries around composites requires a triad of attention where the operator’s skills are cornerstones.

Advanced Drug Delivery Platforms for the Treatment of Oral Pathogens

The oral cavity is a complex ecosystem accommodating various microorganisms (e.g., bacteria and fungi). Various factors, such as diet change and poor oral hygiene, can change the composition of oral microbiota, resulting in the dysbiosis of the oral micro-environment and the emergence of pathogenic microorganisms, and consequently, oral infectious diseases. Systemic administration is frequently used for drug delivery in the treatment of diseases and is associated with the problems, such as drug resistance and dysbiosis. To overcome these challenges, oral drug delivery systems (DDS) have received considerable attention. In this literature review, the related articles are identified, and their findings, in terms of current therapeutic challenges and the applications of DDSs, especially nanoscopic DDSs, for the treatment of oral infectious diseases are highlighted. DDSs are also discussed in terms of structures and therapeutic agents (e.g., antibiotics, antifungals, antiviral, and ions) that they deliver. In addition, strategies (e.g., theranostics, hydrogel, microparticle, strips/fibers, and pH-sensitive nanoparticles), which can improve the treatment outcome of these diseases, are highlighted.

Optically traceable PLGA-silica nanoparticles for cell-triggered doxorubicin delivery

Fluorescent silica nanoparticles with a polymer shell of poly (D, L-lactide-co-glycolide) (PLGA) can provide traceable cell-triggered delivery of the anticancer drug doxorubicin (DOX), protecting the cargo while in transit and releasing it only intracellularly. PLGA with 50:50 lactide:glycolide ratio was grown by surface-initiated ring-opening polymerization (ROP) from silica nanoparticles of ca. 50 nm diameter, doped with a perylenediimide (PDI) fluorescent dye anchored to the silica structure. After loading DOX, release from the core-shell particles was evaluated in solution at physiological pH (7.4), and in human breast cancer cells (MCF-7) after internalization. The hybrid silica-PLGA nanoparticles can accommodate a large cargo of DOX, and the release in solution (PBS) due to PLGA hydrolysis is negligible for at least 72 h. However, once internalized in MCF-7 cells, the nanoparticles release the DOX cargo by degradation of the PLGA. Accumulation of DOX in the nucleus causes cell apoptosis, with the drug-loaded nanoparticles found to be as potent as free DOX. Our fluorescently traceable hybrid silica-PLGA nanoparticles with cell-triggered cargo release offer excellent prospects for the controlled delivery of anticancer drugs, protecting the cargo while in transit and efficiently releasing the drug once inside the cell.

Matrix Metalloproteinases in Dental and Periodontal Tissues and Their Current Inhibitors: Developmental, Degradational and Pathological Aspects

Objectives: This review article aims to describe some of the roles of Matrix metalloproteinases (MMPs) in enamel, dentine, dental caries, hybrid layer degradation, pulp and periodontal tissues, throwing light on their current inhibitors. The article addresses the potential of MMPs to serve as biomarkers with diagnostic and therapeutic value. Design: The sections of this review discuss MMPs’ involvement in developmental, remodeling, degradational and turnover aspects of dental and periodontal tissues as well as their signals in the pathogenesis, progress of different lesions and wound healing of these tissues. The literature was searched for original research articles, review articles and theses. The literature search was conducted in PubMed and MEDLINE for articles published in the last 20 years. Results: 119 published papers, two textbooks and two doctoral theses were selected for preparing the current review. Conclusions: MMPs are significant proteases, of evident contribution in dental and periapical tissue development, health and disease processes, with promising potential for use as diagnostic and prognostic disease biomarkers. Continuing understanding of their role in pathogenesis and progress of different dental, periapical and periodontal lesions, as well as in dentine-pulp wound healing could be a keystone to future diagnostic and therapeutic regimens.

PLGA-Based Nanoplatforms in Drug Delivery for Inhibition and Destruction of Microbial Biofilm

The biofilm community of microorganisms has been identified as the dominant mode of microbial growth in nature and a common characteristic of different microorganisms such as Pseudomonas aeruginosa, Staphylococcus aureus, and Staphylococcus epidermidis. The biofilm structure helps in the protection from environmental threats including host immune system and antimicrobial agents. Thus, the biofilm community has led to a higher prevalence of multidrug-resistant (MDR) strains in recent years. In this regard, the use of a new class of antibiotics, natural compounds, and anti-biofilm enzymes has been considered for the destruction of the microbial biofilm. However, different drawbacks such as low penetration, high susceptibility to degradation, instability, and poor solubility in aqueous solutions limit the use of anti-biofilm agents (ABAs) in a clinical setting. As such, recent studies have been using poly lactic-co-glycolic acid (PLGA)-based nanoplatforms (PLGA NPFs) for delivery of ABAs that have reported promising results. These particles, due to proper drug loading and release kinetics, could suppress microbial attachment, colonization, and biofilm formation for a long time. Additionally, PLGA NPFs, because of the high drug-loading efficiencies, hydrophilic surface, negative charge, and electrostatic interaction, lead to effective penetration of antibiotics to the deeper layer of the biofilm, thereby eliminating the microbial biofilm. Thus, PLGA NPFs could be considered as a potential candidate for coating catheters and other medical material surfaces for inhibition and destruction of the microbial biofilm. However, the exact interaction of PLGA NPFs and the microbial biofilm should be evaluated in animal studies. Additionally, a future goal will be to develop PLGA formulations as systems that can be used for the treatment of the MDR microbial biofilm, since the exact interactions of PLGA NPFs and these biofilm structures are not elucidated. In the present review article, we have discussed various aspects of PLGA usage for inhibition and destruction of the microbial biofilm along with different methods and procedures that have been used for improving PLGA NPF efficacy against the microbial biofilm.

Preparation and application of pH-responsive drug delivery systems

Microenvironment-responsive drug delivery systems (DDSs) can achieve targeted drug delivery, reduce drug side effects and improve drug efficacies. Among them, pH-responsive DDSs have gained popularity since the pH in the diseased tissues such as cancer, bacterial infection and inflammation differs from a physiological pH of 7.4 and this difference could be harnessed for DDSs to release encapsulated drugs specifically to these diseased tissues. A variety of synthetic approaches have been developed to prepare pH-sensitive DDSs, including introduction of a variety of pH-sensitive chemical bonds or protonated/deprotonated chemical groups. A myriad of nano DDSs have been explored to be pH-responsive, including liposomes, micelles, hydrogels, dendritic macromolecules and organic-inorganic hybrid nanoparticles, and micron level microspheres. The prodrugs from drug-loaded pH-sensitive nano DDSs have been applied in research on anticancer therapy and diagnosis of cancer, inflammation, antibacterial infection, and neurological diseases. We have systematically summarized synthesis strategies of pH-stimulating DDSs, illustrated commonly used and recently developed nanocarriers for these DDSs and covered their potential in different biomedical applications, which may spark new ideas for the development and application of pH-sensitive nano DDSs.

A multi-functional dentine bonding system combining a phosphate monomer with eugenyl methacrylate

OBJECTIVE

The tooth-resin composite interface is frequently associated with failure because of microbial contamination, hydrolytic and collagenolytic degradation. Thus, designing a dentine bonding system (DBS) with an intrinsically antimicrobial polymerisable monomer is of significance especially if it can be used with self-etching primers enabling resistance to degradation of the interface.

METHODS

Experimental adhesives were developed incorporating eugenyl methacrylate (EgMA) at concentrations of 0,10 or 20 wt%, designated as EgMA0, EgMA10 and EgMA20, respectively, for use as a two-step self-etch DBS with the functional monomer bis[2-(methacryloyloxy) ethyl] phosphate (BMEP) in the primer. The curing, thermal and wettability properties of the adhesives were determined, and hybrid layer formation was characterised by confocal laser scanning microscopy, microtensile bond strengths (µTBS) and nanoleakage by back-scattered SEM. In situ zymography was used to assess MMP inhibitory activity of the BMEP-EgMA DBS.

RESULTS

EgMA in the adhesives lowered the polymerisation exotherm and resulted in higher Tg, without negatively affecting degree of conversion. Water sorption and solubility were significantly lower with higher concentrations of EgMA in the adhesive. The formation of a distinct hybrid layer was evident from confocal images with the different adhesives, whilst EgMA20 yielded the highest µTBS post water storage challenges and lowest nanoleakage after 6 months. The experimental DBS exhibited minimal to no MMP activity at 3 months.

SIGNIFICANCE

The hydrophobic nature of EgMA and high cross-link density exerts considerable benefits in lowering water uptake and polymerisation exotherm. The application of EgMA, adhesives in conjunction with BMEP in a multi-functional self-etching DBS can resist MMP activity, hence, enhance longevity of the dentine-resin composite interface.

Formulation of nano-graphene doped with nano silver modified dentin bonding agents with enhanced interfacial stability and antibiofilm properties

OBJECTIVE

The aim of this study was to synthesize and characterize reduced nano graphene oxide (RGO) and graphene nanoplatelets (GNPs) doped with silver nanoparticles (nAg) and to prepare an experimental dentin adhesive modified with RGO/nAg and GNP/nAg nanofillers for studying various biological and mechanical properties after bonding to tooth dentin.

METHODS

Nanoparticles were characterized for their morphology and chemical structure using electron microscopy and infrared spectroscopy. Experimental dentin adhesive was modified using two weight percentage (0.25% and 0.5%) of RGO/nAg and GNP/nAg to study its degree of conversion (DC), antimicrobial potential, and cytotoxicity. The effect and significance of these modified bonding agents on resin-dentin bonded interface were investigated by evaluating interfacial nanoleakage, micropermeability, nanodynamic mechanical analysis, micro-tensile bond strength (µTBS), and four-point bending strength (BS), RESULTS: Both 0.25% and 0.5% GNP/nAg graphene-modified adhesives showed comparable DC values to the commercial and experimental adhesive (range: 42-46%). The bacterial viability of the groups 0.25% and 0.5% GNP-Ag remained very low under 25% compared to RGO/nAg groups with low cytotoxicity profiles (cell viability>85%). Resin-bonded dentin interface created with GNP/nAg showed homogenous, well-defined hybrid layer and regularly formed long resin tags devoid of any microporosity as evidenced by SEM and confocal microscopy. The lowest nanoleakage and highest bending strength and µTBS was recorded for 0.25% GNP/nAg after 12 months of ageing. A significantly increased nanoelasticity was seen for all experimental groups except for control groups.

SIGNIFICANCE

The addition of 0.25% GNP/nAg showed optimized anti-biofilm properties without affecting the standard adhesion characteristics.

Silanization of nanographene platelets improves interaction with the dentin bonding resin matrix and enhances interfacial bond integrity to dentin

This study synthesized and characterized graphene nanoplatelets silanized with 3-(trimethoxysilyl)propyl methacrylate (MPS-GNP) for morphological and chemical characteristics. In addition, we modified a dentin bonding agent using different concentrations of MPS-GNP to study its interaction within the resin matrix of the adhesive, degree of conversion (DC), biological, and mechanical properties after bonding to tooth. Both 0.25% and 0.5% MPS-GNP-modified bonding agents showed comparable DC values to the unmodified control adhesive (range: 41%-43%). However, a statistically significant reduction in the DC was found when 0.25% and 0.5% non-silanized GNP was doped with the adhesive (<38%) (p < 0.05). On day 30, the bacterial viability of 0.5% GNP and MPS-GNP groups remained very low under 22% with the highest dead cell count (p < 0.05). GNP incorporated within the resin matrix of the dentin bonding agent showed clear evidence of several interfacial gap formations and non-union between the GNP surface and resin matrix, while the MPS-GNP modified dentin bonding agent showed MPS-GNP with no gap formation with complete union between the graphene surface and resin matrix. The decrease in the μTBS was least pronounced for 0.25% and 0.5% MPS-GNP groups. After 12 months of ageing, the groups 0.25% and 0.5% MPS-GNP also showed the highest BS as compared to the rest of the groups. Statistically significant reduction was seen in nanohardness at the hybrid layer and adhesive layer for GNP groups after 4 months of storage. The addition of up to 0.5% MPS-GNP showed optimized DC, antibiofilm activity, and micro-tensile bond strength without affecting the standard adhesion characteristics as compared to GNP alone.

Effect of post-curing light exposure time on the physico-mechanical properties and cytotoxicity of 3D-printed denture base material

OBJECTIVE

This study investigated the effect of post curing light exposure time on the physico-mechanical properties and cytotoxicity of a 3D-printed PMMA-based denture material in comparison to a conventional heat-cured alternative as a control.

METHODS

3D-printed specimens were fabricated followed by post-curing for 0, 5, 10 or 20 min at 200 W and light wavelength range of 390-540 nm. Heat-cured specimens were fabricated using a standard protocol. Specimens were placed in artificial saliva at 37 ℃ for 48 h (immediate groups) and 6 months (aged group), then evaluated flexural strength/modulus, fracture toughness, microhardness, and degree of conversion. Water sorption and solubility was assessed after 28 days. Flexural strength, flexural modulus, and fracture toughness were tested through three-point bending tests, while the surface hardness was tested using Vickers's test. Fractured specimens were viewed by scanning electron microscope (SEM). Cytotoxicity in term of cell viability was evaluated using human oral fibroblasts.

RESULTS

Flexural strength/modulus, fracture toughness and surface hardness significantly improved with the increase in light curing time up to 20 min. The same pattern of improvement was found with degree of conversion, water sorption, solubility, and cell viability. There was no significant difference (p < 0.01) between heat-cured material and 3D specimens post-cured for 20 min in term of flexural strength/modulus, surface hardness, and degree of conversion at the two-storage time points.

SIGNIFICANCE

Generally, the physico-mechanical properties of the 3D-printed denture base material improve as post curing time increases up to 20 min which exhibited comparable performance as the conventional heat-cured control.

Ultrastructural and physicochemical characterization of pH receptive chlorhexidine-loaded poly-L-glycolic acid-modified orthodontic adhesive

This study aims to evaluate the feasibility of chlorhexidine (CHX)-loaded poly-L-glycolic acid (PLGA) nanoparticles as a modifier of a commercial orthodontic adhesive via the assessment of physicochemical, biological, and mechanical properties at tooth-bracket interface. CHX-loaded PLGA nanoparticles were synthesized using double emulsion-solvent evaporation method and characterized using transmission electron microscopy and Raman analysis. CHX-loaded PLGA nanoparticles in Transbond XT orthodontic adhesive were prepared using two different concentrations of the CHX (25 and 50%) and characterized for degree of conversion (DC), antimicrobial, and cytotoxicity testing. Bonded specimens were tested for shear bond strength (SBS) and adhesive remnant index (ARI) at tooth-bracket interface. The synthesized PLGA nanoparticles averaged between 60 and 80 nm in size. After loading CHX inside PLGA nanoparticles, the morphology of the PLGA nanoparticles was considerably changed. Orthodontic bracket bonded with 25% CHX-loaded PLGA-modified adhesive demonstrated DC scores similar to control group. Both 25 and 50% CHX-loaded PLGA-modified adhesive specimens showed higher antibacterial activity against S. mutans compared to control group. The least mean SBS values were exhibited by 50% CHX-loaded PLGA-modified adhesive samples, while a statistically significant difference was observed in the mean ARI values among all study groups at all-time points (p = .018). This study indicates that the addition of CHX-loaded PLGA nanoparticles in Transbond XT achieved stable bonds with enhanced antimicrobial and mechanical properties.

Nanoparticle incorporated dentin bonding agent to caries effected dentin treated by photodynamic therapy, laser or chlorhexidine

PURPOSE

This study aims to evaluate the microtensile bond strength (µTBS) and failure modes of graphene nanoplatelets doped with hydroxyapatite (GNP-HA) modified self-etch dentin bonding agent (DBA) to caries effected dentin (CAD) after various conventional and laser disinfection protocols.

MATERIALS AND METHODS

Graphene nanoplatelets and HA nanoparticles were doped and incorporated in DBA. Fifty carious human molar teeth were used for the experiment. CAD specimens were divided into five groups (n=10/group) into CAD undergoing no disinfection treatment (Group-CAD), 2% chlorhexidine disinfection (Group-CHX), 6% NaOCl disinfection (Group-NaOCl), methylene blue assisted PDT (Group-MB-PDT), and Er,Cr:YSGG laser application (Group-Er,Cr:YSGG). Following the respective disinfection techniques, the GNP-HA modified adhesive was applied to all treated CAD surface. Subsequently µTBS and failure modes were analyzed.

RESULTS

Representative scanning electron microscope images (SEM images) of the synthesized GNP-HA indicated flakes of graphene with varying size lengthwise (>500 nm) with 1-2 nm width. The doped HA showed round and spherical morphology conjugated over the surface of the GNP measuring 40 -100 nm in diameter. CAD group that underwent no treatment represented the highest µTBS (29.43 MPa). Within the tested specimens, MB-PDT (22.37 MPa) and Er,Cr:YSGG (21.85 MPa) showed the highest µTBS values than CHX (15.69 MPa) and NaOCl (11.46 MPa). However, there was no significant difference between MB-PDT and Er,Cr:YSGG (p>0.05) and a significant difference existed between CHX and NaOCl (p<0.05). Equal distribution of cohesive and adhesive failures was noted for CAD, CHX and NaOCl treated specimens. A majority of adhesive failures existed in the MB-PDT groups. While admixed and adhesive failures were higher in Er,Cr:YSGG treated samples.

CONCLUSIONS

The outcome of this study suggests that CAD restored by GNP-HA modified self-etch adhesive showed highest bond strength after MB-PDT and Er,Cr:YSGG protocols with low amount of adhesive failure.

Mechanical and antimicrobial effects of riboflavin-mediated photosensitization of in vitro C. albicans formed on polymethyl methacrylate resin

PURPOSE

This study assessed the potential of riboflavin-mediated photodynamic therapy (RF-PDT) against Candida albicans (C. albicans) and compared the effects of RF-PDT with other therapeutic modalities in terms of mechanical and surface characteristics of acrylic denture base material.

MATERIALS AND METHODS

Molds (10 × 10 × 2 mm) of acrylic resin specimens were prepared and underwent artificial ageing. C. albicans were grown aerobically over the specimens and divided into four groups (n = 10/group); Group-I: no decontamination; Group-II: nystatin suspension; Group-III: riboflavin 0.1% in darkness, Group-IV: blue LED light only, and Group-V: riboflavin 0.1% for 10 minutes (pre-irradiation time) and photoactivated by the blue LED light (light dose). Fungal viability was assessed using MTT assay and characterized using scanning electron microscopy and confocal laser microscopy (CLSM). Treated specimens were subjected to surface roughness (R_a), flexural strength (FS), and flexural modulus (FM).

RESULTS

Group-I showed the highest C. albicans viability followed by Group-III. Nystatin group (Group-II) showed ∼50% of the viability while RF-PDT showed the least C. albicans viability among the four groups (p<0.05). On SEM, specimens treated with Group-IV and V showed almost clear and free from C. albicans that was evidenced on CLSM. Post-treated specimens and storage after 72 h revealed that FS was significantly higher for RF-PDT group as compared to any other group (>105.82 MPa) (p<0.05). The FM and Ra showed statistically no significant difference between the groups (p>0.05).

CONCLUSION

RF-PDT showed the highest anti-fungal capacity against C. albicans over acrylic denture surface without any surface deterioration.

Effect of ultrasonic scaling with adjunctive photodynamic therapy on the treatment of gingival inflammation among diabetic patients undergoing fixed orthodontic treatment

BACKGROUND

The aim of the present clinical trial was to evaluate the effect of methylene blue-mediated antimicrobial photodynamic therapy (aPDT) on the gingival and immunological parameters in diabetic adolescent patients undergoing fixed orthodontic treatment.

METHODS

The selected 40 participants were randomized equally into two groups; Group I (ultrasonic scaling + oral hygiene instructions) and Group II (ultrasonic scaling/oral hygiene instructions + aPDT). Serum HbA1c levels was assessed for all the participants at chairside. Plaque index (Pi), and bleeding on probing (BOP) were analyzed. Moreover, the assessment of crevicular fluid matrix metalloproteinase 8 (MMP-8) and macrophage inflammatory protein 1 alpha (MIP-1α) was performed using enzyme-linked immunosorbent assay technique. All measurements were recorded at baseline, 6 weeks, and 12 weeks follow-up periods, respectively. Intergroup comparisons for p-value were computed using Mann-Whitney test and Wilcoxon singed ranks test to compute p-value for intra-group comparisons. Stepwise logistic regression analysis was used to identify explanatory variables for reduction in plaque scores and bleeding on probing, after controlling for the effects of other covariates. Odds ratios and 95% confidence intervals were used to assess the direction and strength for associations. Significance level was set at 5% for all analyses.

RESULTS

All 40 individuals completed the clinical trial. There was a statistically significant reduction in Pi and BOP in both Group I and Group II from baseline to 12 weeks of follow up (P<0.05). However, there was slight reduction in the plaque scores in Group-II as compared to Group-I at 12 weeks visit (P<0.05). There was also a statistically significant difference for BOP when Group-I was compared with Group-II on 12 weeks follow up assessment (P<0.05). HbA1c assessment indicated no statistically significant difference either within or between groups at any time point (P>0.05). Both MMP-8 and MIP-1α reported a significant decrease for both Groups I and II at 6 weeks and 12 weeks follow-up periods in comparison to baseline (P<0.05). Inter-group comparison indicated a statistically significant difference noted at both 6 weeks follow up that was maintained at 12 weeks follow up (P<0.05). The logistic regression analysis revealed that even after controlling the mean BMI as a predictor, the change of biomarker levels along with the improvement in plaque scores and bleeding on probing was not significant (p> 0.05).

CONCLUSION

aPDT significantly improved bleeding on probing and proinflammatory biomarkers among diabetic adolescent patients undergoing fixed orthodontic therapy.

Impact of riboflavin mediated photodynamic disinfection around fixed orthodontic system infected with oral bacteria

PURPOSE

The aim of this laboratory study was to investigate the amount of bacterial destruction through riboflavin mediated photodynamic therapy (PDT) around fixed orthodontic devices by using the two strains of bacteria Streptococcus mutans and Streptococcus sanguinis.

MATERIALS AND METHODS

A total of 80 metallic brackets were divided into four groups consisting of 20 brackets each. Group-I: riboflavin + LED irradiation; Group-II: riboflavin alone; Group-III: immersion in 0.2 % chlorhexidine gluconate solution and Group-IV: not submitted to any treatment. All metallic brackets were immersed in the standard bacterial solutions and incubated at 48 h. All samples were subjected to MTT assay for microbial cell viability testing after treatment. After 24 h of incubation, biofilms adhered on the mesh of metallic brackets after treatment were assessed by confocal laser microscopy. The total CFU/mL was estimated, and the results were log-transformed (log₁₀) and analyzed using one-way analysis of variance and Tukey-Kramer test. P-value was set to <0.05 that indicated statistical significance.

RESULTS

The samples from group-IV showed the highest amount of relative biofilm viability compared to any other group while group-I (PDT) showed the least viability of the two bacterial strains studied (p < 0.05). Group-I showed no significant difference when compared with group-III (chlorhexidine) (p > 0.05). The biofilms on the samples from group-II and group-IV were largely viable indicating thick green staining across the mesh of the brackets. Among the group-III samples, there were predominantly dead cells as compared to the live cell staining. A considerable amount of red staining was observed with noticeable less green staining in group-I samples.

CONCLUSION

This laboratory investigation revealed that riboflavin mediated PDT significantly reduced the amounts of S. mutans and S. sanguinis around the orthodontic brackets.