Antibacterial effect of bactericide immobilized in resin matrix

Exploring the Effect of Cetylpyridinium Chloride Addition on the Antibacterial Activity and Surface Hardness of Resin-Based Dental Composites

The aim of this study was to evaluate the effect of cetylpyridinium chloride (CPC) addition on the antibacterial and surface hardness characteristics of two commercial resin-based dental composites (RBDCs). A total of two hundred and seventy (n = 270) specimens from Filtek Z250 Universal and Filtek Z350 XT flowable RBDCs were fabricated with the addition of CPC at 2 %wt and 4 %wt concentrations to assess their antibacterial activity using the agar diffusion test and direct contact inhibition test, and their surface hardness using the Vickers microhardness test after 1 day, 30 days, and 90 days of aging. A surface morphology analysis of the specimens was performed using a scanning electron microscope (SEM). The RBDCs that contained 2 %wt and 4 %wt CPC demonstrated significant antibacterial activity against Streptococcus mutans up to 90 days, with the highest activity observed for the 4 %wt concentration. Nevertheless, there was a reduction in antibacterial effectiveness over time. Moreover, compared to the control (0 %wt) and 2 %wt CPC groups, the universal RBDCs containing 4 %wt CPC exhibited a notable decrease in surface hardness, while all groups showed a decline in hardness over time. In conclusion, the satisfactory combination of the antibacterial effect and surface hardness property of RBDCs was revealed with the addition of a 2 %wt CPC concentration.

Multifunctional Dental Adhesives Formulated with Silane-Coated Magnetic Fe3O4@m-SiO2 Core-Shell Particles to Counteract Adhesive Interfacial Breakdown

The process of bonding to dentin is complex and dynamic, greatly impacting the longevity of dental restorations. The tooth/dental material interface is degraded by bacterial acids, matrix metalloproteinases (MMPs), and hydrolysis. As a result, bonded dental restorations face reduced longevity due to adhesive interfacial breakdown, leading to leakage, tooth pain, recurrent caries, and costly restoration replacements. To address this issue, we synthesized and characterized a multifunctional magnetic platform, CHX@SiQuac@Fe3O4@m-SiO2, to provide several beneficial functions. The platform comprises Fe3O4 microparticles and chlorhexidine (CHX) encapsulated within mesoporous silica, which was silanized by an antibacterial quaternary ammonium silane (SiQuac). This platform simultaneously targets bacterial inhibition, stability of the hybrid layer, and enhanced filler infiltration by magnetic motion. Comprehensive experiments include X-ray diffraction, FT-IR, VSM, EDS, N2 adsorption-desorption (BET), transmission electron microscopy, scanning electron microscopy, thermogravimetric analysis, and UV-vis spectroscopy. Then, CHX@SiQuac@Fe3O4@m-SiO2 was incorporated into an experimental adhesive resin for dental bonding restorations, followed by immediate and long-term antibacterial assessment, cytotoxicity evaluation, and mechanical and bonding performance. The results confirmed the multifunctional nature of CHX@SiQuac@Fe3O4@m-SiO2. This work outlined a roadmap for (1) designing and tuning an adhesive formulation containing the new platform CHX@SiQuac@Fe3O4@m-SiO2; (2) assessing microtensile bond strength to dentin using a clinically relevant model of simulated hydrostatic pulpal pressure; and (3) investigating the antibacterial outcome performance of the particles when embedded into the formulated adhesives over time. The results showed that at 4 wt % of CHX@SiQuac@Fe3O4@m-SiO2-doped adhesive under the guided magnetic field, the bond strength increased by 28%. CHX@SiQuac@Fe3O4@m-SiO2 enhanced dentin adhesion in the magnetic guide bonding process without altering adhesive properties or causing cytotoxicity. This finding presents a promising method for strengthening the tooth/dental material interface's stability and extending the bonded restorations' lifespan.

Novel antimicrobial and self-healing dental resin to combat secondary caries and restoration fracture

OBJECTIVE

Dental resin composites have been the most popular materials for repairing tooth decay in recent years. However, secondary caries and bulk fracture are the major hurdles that affect the lifetime of dental resin composites. This current study synthesized a novel antimicrobial and self-healing dental resin containing nanoparticle-modified self-healing microcapsules to combat secondary caries and restoration fracture.

METHODS

Multifunctional dental resins containing 0-20% nanoparticle-modified self-healing microcapsules were prepared. The water contact angle, antimicrobial properties, mechanical properties, cell toxicity, and self-healing capability of the dental resins were tested.

RESULTS

A novel multifunctional dental resin was synthesized. When the microcapsule mass fraction was 10%, the resin presented a strong bacteriostasis rate (80.3%) and excellent self-healing efficiency (66.1%), while the hydrophilicity, mechanical properties, and cell toxicity were not affected.

SIGNIFICANCE

The novel antimicrobial self-healing dental resin is a promising candidate for use in clinical practice, which provides a simple and highly efficient strategy to combat secondary caries and restoration fracture. This novel dental resin also gives the inspiration to prolong the service life of dental restorations.

Novel Remineralizing and Antibiofilm Low-Shrinkage-Stress Nanocomposites to Inhibit Salivary Biofilms and Protect Tooth Structures

Recurrent caries remain a persistent concern, often linked to microleakage and a lack of bioactivity in contemporary dental composites. Our study aims to address this issue by developing a low-shrinkage-stress nanocomposite with antibiofilm and remineralization capabilities, thus countering the progression of recurrent caries. In the present study, we formulated low-shrinkage-stress nanocomposites by combining triethylene glycol divinylbenzyl ether and urethane dimethacrylate, incorporating dimethylaminododecyl methacrylate (DMADDM), along with nanoparticles of calcium fluoride (nCaF2) and nanoparticles of amorphous calcium phosphate (NACP). The biofilm viability, biofilm metabolic activity, lactic acid production, and ion release were evaluated. The novel formulations containing 3% DMADDM exhibited a potent antibiofilm activity, exhibiting a 4-log reduction in the human salivary biofilm CFUs compared to controls (p < 0.001). Additionally, significant reductions were observed in biofilm biomass and lactic acid (p < 0.05). By integrating both 10% NACP and 10% nCaF2 into one formulation, efficient ion release was achieved, yielding concentrations of 3.02 ± 0.21 mmol/L for Ca, 0.5 ± 0.05 mmol/L for P, and 0.37 ± 0.01 mmol/L for F ions. The innovative mixture of DMADDM, NACP, and nCaF2 displayed strong antibiofilm effects on salivary biofilm while concomitantly releasing a significant amount of remineralizing ions. This nanocomposite is a promising dental material with antibiofilm and remineralization capacities, with the potential to reduce polymerization-related microleakage and recurrent caries.

Novel Bioactive Nanocomposites Containing Calcium Fluoride and Calcium Phosphate with Antibacterial and Low-Shrinkage-Stress Capabilities to Inhibit Dental Caries

OBJECTIVES

Composites are commonly used for tooth restorations, but recurrent caries often lead to restoration failures due to polymerization shrinkage-stress-induced marginal leakage. The aims of this research were to: (1) develop novel low-shrinkage-stress (L.S.S.) nanocomposites containing dimethylaminododecyl methacrylate (DMADDM) with nanoparticles of calcium fluoride (nCaF2) or amorphous calcium phosphate (NACP) for remineralization; (2) investigate antibacterial and cytocompatibility properties.

METHODS

Nanocomposites were made by mixing triethylene glycol divinylbenzyl ether with urethane dimethacrylate containing 3% DMADDM, 20% nCaF2, and 20% NACP. Flexural strength, elastic modulus, antibacterial properties against Streptococcus mutans biofilms, and cytotoxicity against human gingival fibroblasts and dental pulp stem cells were tested.

RESULTS

Nanocomposites with DMADDM and nCaF2 or NACP had flexural strengths matching commercial composite control without bioactivity. The new nanocomposite provided potent antibacterial properties, reducing biofilm CFU by 6 logs, and reducing lactic acid synthesis and metabolic function of biofilms by 90%, compared to controls (p < 0.05). The new nanocomposites produced excellent cell viability matching commercial control (p > 0.05).

CONCLUSIONS

Bioactive L.S.S. antibacterial nanocomposites with nCaF2 and NACP had excellent bioactivity without compromising mechanical and cytocompatible properties. The new nanocomposites are promising for a wide range of dental restorations by improving marginal integrity by reducing shrinkage stress, defending tooth structures, and minimizing cariogenic biofilms.

Effectiveness of adhesive containing MDPB: A practice-based clinical trial

OBJECTIVES

This prospective practice-based trial assessed the longevity of composite restorations made with an adhesive containing an antibacterial monomer compared to a conventional adhesive.

METHODS

9 general practices in the Netherlands were provided with two composite resin adhesives, each for a period of 9 months. Adhesive P contained the quaternary ammonium salt MDPB, and Adhesive S was a control. Patient's age and caries risk, as well as tooth type/number, reason for restoration placement, used restorative material and adhesive, and restored surfaces were recorded. All interventions carried out on these teeth in the 6 years after restoration were extracted from the electronic patient records, along with their date, type, reason, and surfaces. Two dependent variables were defined: general failure, and failure due to secondary caries. All data handling and multiple Cox regression analysis were carried out in R 4.0.5.

RESULTS

11 dentists from 7 practices made 10,151 restorations over a period of two years in 5102 patients. 4591 restorations were made with adhesive P, whereas 5560 were made with adhesive S. The observation period was up to 6.29 years, median observation time was 3.74 years. Cox regression showed no significant difference between the two adhesive materials when corrected for age, tooth type and caries risk, for general failure nor failure due to caries.

SIGNIFICANCE

No difference in restoration survival could be shown between composite restorations made using an adhesive containing MDPB and control. Restorations made with the adhesive containing MDPB also did not fail more or less frequently due to secondary caries. This trial is registered on clinicaltrials.gov with identifier NCT05118100.

Novel Dental Low-Shrinkage-Stress Composite with Antibacterial Dimethylaminododecyl Methacrylate Monomer

OBJECTIVES

Current dental resins exhibit polymerization shrinkage causing microleakage, which has the potential to cause recurrent caries. Our objectives were to create and characterize low-shrinkage-stress (LSS) composites with dimethylaminododecyl methacrylate (DMADDM) as an antibacterial agent to combat recurrent caries.

METHODS

Triethylene glycol divinylbenzyl ether and urethane dimethacrylate were used to reduce shrinkage stress. DMADDM was incorporated at different mass fractions (0%, 1.5%, 3%, and 5%). Flexural strength, elastic modulus, degree of conversion, polymerization stress, and antimicrobial activity were assessed.

RESULTS

The composite with 5% DMADDM demonstrated higher flexural strength than the commercial group (p < 0.05). The addition of DMADDM in BisGMA-TEGDMA resin and LSS resin achieved clinically acceptable degrees of conversion. However, LSS composites exhibited much lower polymerization shrinkage stress than BisGMA-TEGDMA composite groups (p < 0.05). The addition of 3% and 5% DMADDM showed a 6-log reduction in Streptococcus mutans (S. mutans) biofilm CFUs compared to commercial control (p < 0.001). Biofilm biomass and lactic acid were also substantially decreased via DMADDM (p < 0.05).

CONCLUSIONS

The novel LSS dental composite containing 3% DMADDM demonstrated potent antibacterial action against S. mutans biofilms and much lower polymerization shrinkage-stress, while maintaining excellent mechanical characteristics. The new composite is promising for dental applications to prevent secondary caries and increase restoration longevity.

Long-Term Antibacterial Efficacy of Cetylpyridinium Chloride-Montmorillonite Containing PMMA Resin Cement

Despite being able to adhesively restore teeth, adhesives and cement do not possess any anticariogenic protection potential, by which caries recurrence may still occur and reduce the clinical lifetime of adhesive restorations. Several antibacterial agents have been incorporated into dental adhesives and cement to render them anticariogenic. Due to an additional therapeutic effect, such materials are classified as 'dental combination products' with more strict market regulations. We incorporated cetylpyridinium chloride (CPC), often used for oral hygiene applications, into montmorillonite (CPC-Mont), the latter to serve as a carrier for controlled CPC release. CPC-Mont incorporated into tissue conditioner has been approved by the Pharmaceuticals and Medical Devices Agency (PmontMDA) in Japan. To produce a clinically effective dental cement with the antibacterial potential to prevent secondary caries, we incorporated CPC-Mont into PMMA resin cement. We measured the flexural strength, shear bond strength onto dentin, CPC release, and the biofilm-inhibition potential of the experimental CPC-Mont-containing PMMA cement. An 8 and 10 wt% CPC-Mont concentration revealed the antibacterial potential without reducing the mechanical properties of the PMMA cement.

Development of Autopolymerizing Resin Material with Antimicrobial Properties Using Montmorillonite and Nanoporous Silica

Although autopolymerizing resin offers numerous applications in orthodontic treatment, plaque tends to accumulate between the appliance and the mucosa, which increases the number of microorganisms present. In this study, we added cetylpyridinium chloride (CPC) loaded montmorillonite (Mont) and nanoporous silica (NPS) to autopolymerizing resin (resin-Mont, resin-NPS) and evaluated their drug release capacity, antimicrobial capacity, drug reuptake capacity, mechanical strength, and color tone for the devolvement of autopolymerizing resin with antimicrobial properties. As observed, resin-Mont and resin-NPS were capable of the sustained release of CPC for 14 d, and a higher amount of CPC was released compared to that of resin-CPC. Additionally, resin-Mont and resin-NPS could reuptake CPC. Moreover, the antimicrobial studies demonstrated that resin-Mont and resin-NPS could release effective amounts of CPC against Streptococcus mutans for 14 d and 7 d after reuptake, respectively. Compared to resin-CPC, resin-Mont exhibited a higher sustained release of CPC in all periods, both in the initial sustained release and after reuptake. However, the mechanical strength decreased with the addition of Mont and NPS, with a 36% reduction observed in flexural strength for resin-Mont and 25% for resin-NPS. The application of these results to the resin portion of the orthodontic appliances can prevent bacterial growth on the surface, as well as on the interior, of the appliances and mitigate the inflammation of the mucosa.

Recent Update on Applications of Quaternary Ammonium Silane as an Antibacterial Biomaterial: A Novel Drug Delivery Approach in Dentistry

Quaternary ammonium silane [(QAS), codename – k21] is a novel biomaterial developed by sol-gel process having broad spectrum antimicrobial activities with low cytotoxicity. It has been used in various concentrations with maximum antimicrobial efficacy and biocompatibility. The antimicrobial mechanism is displayed via contact killing, causing conformational changes within the bacterial cell membrane, inhibiting Sortase-A enzyme, and causing cell disturbances due to osmotic changes. The compound can attach to S1' pockets on matrix metalloproteinases (MMPs), leading to massive MMP enzyme inhibition, making it one of the most potent protease inhibitors. Quaternary ammonium silane has been synthesized and used in dentistry to eliminate the biofilm from dental tissues. QAS has been tested for its antibacterial activity as a cavity disinfectant, endodontic irrigant, restorative and root canal medication, and a nanocarrier for drug delivery approaches. The review is first of its kind that aims to discuss applications of QAS as a novel antibacterial biomaterial for dental applications along with discussions on its cytotoxic effects and future prospects in dentistry.

Propolis in Oral Healthcare: Antibacterial Activity of a Composite Resin Enriched With Brazilian Red Propolis

The aim of this study was to obtain a Brazilian red propolis (BRP) enriched composite resin and to perform the characterization of its antibacterial activity, mechanical, and physical-chemical properties. Brazilian red propolis ethyl acetate extract (EABRP) was characterized by LC-ESI-Orbitrap-FTMS, UPLC-DAD, antibacterial activity, total flavonoids content, and radical scavenging capacity. BRP was incorporated to a commercial composite resin (RC) to obtain BRP enriched composite at 0.1, 0.15 and 0.25% (RP10, RP15 and RP25, respectively). The antibacterial activity RPs was evaluated against Streptococcus mutans by contact direct test and expressed by antibacterial ratio. The RPs were characterized as its cytotoxicity against 3T3 fibroblasts, flexural strength (FS), Knoop microhardness (KHN), post-cure depth (CD), degree of conversion (DC%), water sorption (Wsp), water solubility (Wsl), average roughness (Ra), and thermal analysis. Were identified 50 chemical compounds from BRP extract by LC-ESI-Orbitrap-FTMS. EABRP was bacteriostatic and bactericide at 125 and 500 μg/ml, respectively. The RP25 exhibited antibacterial ratio of 90.76% after 1 h of direct contact with S. mutans (p < 0.0001) while RC no showed significative antibacterial activity (p = 0.1865), both compared with cell control group. RPs and RC no showed cytotoxicity. RPs exhibited CD from 2.74 to 4.48 mm, DC% from 80.70 to 83.96%, Wsp from 17.15 to 21.67 μg/mm³, Wsl from 3.66 to 4.20 μg/mm³, Ra from 14.48 to 20.76 nm. RPs showed thermal resistance between 448–455°C. The results support that propolis can be used on development of modified composite resins that show antibacterial activity and that have compatible mechanical and physical-chemical properties to the indicate for composite resins.

Novel composite cement containing the anti-microbial compound CPC-Montmorillonite

OBJECTIVES

The aim of this study was to evaluate the mechanical properties, bonding performance and anti-microbial activity of a novel composite cement containing cetylpyridinium chloride (CPC) modified montmorillonite ('CPC-Mont'), and using these parameters to determine the optimal particle size and concentration of CPC-Mont the composite cement can be loaded with.

METHODS

CPC-Mont particles with a median diameter of 30 and 7 µm were prepared and added to a composite cement at a concentration of 2, 3, 4, 5 and 7.5 wt%. Mechanical properties and bonding performance of the experimental composite cements were evaluated by 3-point bending and micro-tensile bond-strength testing. The amount of CPC released from the cement disks was quantified using a UV-vis recording spectrophotometer. The anti-biofilm activity was studied using scanning electron microscopy (SEM).

RESULTS

Adding 30-μm CPC-Mont decreased the mechanical properties and bonding performance of the composite cement, while no reduction was observed for the 7-μm CPC-Mont loaded cement formulation. Although CPC release substantially decreased during the 7-day period assessed, 5- and 7.5-wt% CPC-Mont loaded composite cement inhibited biofilm formation for 30 days.

SIGNIFICANCE

Loading composite cement with CPC-Mont with a median diameter of 7 µm at concentrations of 5-7.5 wt% was effective in achieving continuous anti-biofilm activity, while maintaining mechanical strength and bonding performance.

A comprehensive review of the antibacterial activity of dimethylaminohexadecyl methacrylate (DMAHDM) and its influence on mechanical properties of resin-based dental materials

The repetitive restorative cycle should be avoided, aiming at the smallest number of restorations' replacements to ensure greater tooth longevity. Antibacterial materials associated with the control of caries etiological factors can help improve restoration's durability. This review aimed to analyze the results of in vitro studies that added Dimethylaminohexadecyl methacrylate (DMAHDM), an antibacterial monomer, to restorative materials. The PubMed, SCOPUS, Web of Science, and Biblioteca Virtual em Saúde databases were screened for studies published between 2015 and 2020. After full-text reading, 24 articles were included in the final sample. DMAHDM has demonstrated antibacterial efficacy against several bacteria related to dental caries and periodontal diseases, causing a transition in the biofilm balance without inducing resistance. When DMAHDM was included in acrylic resin, the material cytotoxicity increased, and changes in mechanical properties were observed. In contrast, resin composites had their mechanical properties maintained in most studies; however, toxicity was not examined. The association between DMAHDM and 2-methacryloyloxyethyl phosphorylcholine or silver nanoparticles improved the antibacterial effect. Besides, the association with nanoparticles of amorphous calcium phosphate or nanoparticles of calcium fluoride can provide remineralization capacity. There is a lack of information on the cytotoxicity and bacteria resistance induction, and further studies are needed to address this.

A lingering mouthwash with sustained antibiotic release and biofilm eradication for periodontitis

Dental plaque biofilms are believed to be one of the principal virulence factors in periodontitis resulting in tooth loss. Traditional mouthwashes are limited due to the continuous flow of saliva and poor drug penetration ability in the biofilm. Herein, we fabricated an antibiotic delivery platform based on natural polysaccharides (chitosan and cyclodextrin) as a novel mouthwash for the topical cavity delivery of minocycline. The penetration and residence mechanisms demonstrate that the platform can prolong the residence time up to 12 h on biofilms. Furthermore, sustained release can enhance the penetration of drugs into biofilms. In vitro antibiofilm experimental results indicated that the mouthwash effectively kills bacteria and eradicate biofilms. Effective treatment in vivo was confirmed by the significantly reduced dental plaque and alleviated inflammation observed in a rat periodontitis model. In summary, this novel platform can improve antibiofilm efficiency and prevent drugs from being washed away by saliva, which may provide benefits for many oral infectious diseases.

Novel Nano Calcium Fluoride Remineralizing and Antibacterial Dental Composites

OBJECTIVE

Composites with remineralizing and antibacterial properties are favorable for caries inhibition. The objectives of this study were to develop a new bioactive nanocomposite with remineralizing and antibiofilm properties by incorporating dimethylaminohexadecyl methacrylate (DMAHDM) and nano-calcium fluoride (nCaF₂).

METHODS

nCaF₂ was produced via a spray-drying method and integrated at 15% mass fraction into composite. DMAHDM was added at 3% mass fraction. Mechanical properties and F and Ca ion releases were assessed. Colony-forming units (CFU), lactic acid and metabolic activity of biofilms on composites were performed.

RESULTS

The new composites had flexural strengths of (95.28±6.32) MPa and (125.93±7.49) MPa, which were within the ISO recommendations. Biofilm CFU were reduced by 3-4 log (p<0.05). The composites achieved high F releases of (0.89±0.01) mmol/L and (0.44±0.01) mmol/L, and Ca releases of (1.46±0.05) mmol/L and (0.54±0.005) mmol/L.

CONCLUSIONS

New nanocomposites were developed with good mechanical properties, potent antibacterial activity against salivary biofilms, and high F and Ca ion releases with potential for remineralization.

CLINICAL SIGNIFICANCE

Novel nanocomposites using nCaF₂ and DMAHDM were developed with potent antibacterial and remineralizing effects and high F and Ca ion releases. They are promising to inhibit recurrent caries, promote remineralization, and possess long-term sustainability.

Covalent Immobilization of Organic Photosensitizers on the Glass Surface: Toward the Formation of the Light-Activated Antimicrobial Nanocoating

Two highly efficient commercial organic photosensitizers—azure A (AA) and 5-(4-aminophenyl)-10,15,20-(triphenyl)porphyrin (APTPP)—were covalently attached to the glass surface to form a photoactive monolayer. The proposed straightforward strategy consists of three steps, i.e., the initial chemical grafting of 3-aminopropyltriethoxysilane (APTES) followed by two chemical postmodification steps. The chemical structure of the resulting mixed monolayer (MIX_TC_APTES@glass) was widely characterized by X-ray photoelectron (XPS) and Raman spectroscopies, while its photoactive properties were investigated in situ by UV–Vis spectroscopy with α-terpinene as a chemical trap. It was shown that both photosensitizers retain their activity toward light-activated generation of reactive oxygen species (ROS) after immobilization on the glassy surface and that the resulting nanolayer shows high stability. Thanks to the complementarity of the spectral properties of AA and APTPP, the effectiveness of the ROS photogeneration under broadband illumination can be optimized. The reported light-activated nanocoating demonstrated promising antimicrobial activity toward Escherichia coli (E. coli), by reducing the number of adhered bacteria compared to the unmodified glass surface.

Antimicrobial and self-crosslinking potential of experimentally developed dioctadecyldimethyl ammonium bromide and riboflavin dentin adhesive

The aim of the study is to investigate a new formulation, based on dioctadecyldimethyl ammonium-bromide (QA) and riboflavin (RF), combining antimicrobial activities and protease inhibitory properties with collagen crosslinking without interference to bonding capabilities in a rabbit model. Quaternary ammonium riboflavin (QARF) experimental adhesives modified with dioctadecyldimethyl ammonium-bromide and riboflavin were bonded (0.5/1.0/2.0%) to rabbit dentin to investigate for pulpal-histology, interfacial-morphology, transmission electron microscopy, mechanical properties, collagen crosslinking, micro-Raman analysis, antimicrobial, and anti-protease activities. Collagen type-I molecules were generated using molecular-docking. Odontoblasts appeared with normal histology, were seen in controls with no inflammatory cells detected in 0.5% specimens at day 7 and mild inflammatory response at day 30. In QARF 2.0%, inflammatory cells were not detected at day 7 and 30 (p < .05). Dentinal tubules are seen with intact collagen surface in 1% specimens. Resin penetrated inside 1% adhesive specimens with few irregularly funnel-shaped tags. Transmission electron microscopy showed thinner collagen in all specimens except 1% QARF specimens. Biofilms were influenced by QARF adhesives. Elastic moduli were significantly higher in 1.0% and 2.0% QARF adhesive specimens with a significant increase in total crosslinks. Stable amide groups with anti-protease activity was observed in QARF groups. Charged residues were seen in the triple helix hCOL3A1, Gly489-Gly510 after stabilisation with formulation. The 1% QARF modified adhesives improved biochemical and biomechanical properties of rabbit dentin.

Antibacterial Effect of Amino Acid-Silver Complex Loaded Montmorillonite Incorporated in Dental Acrylic Resin

Several dental materials contain silver for antibacterial effect, however the effect is relatively low. The reason for the lower antibacterial efficacy of silver is considered to be the fact that silver ions bind to chloride ions in saliva. To develop new effective silver antibacterial agents that can be useful in the mouth, we synthesized two novel amino acid (methionine or histidine)-silver complexes (Met or His-Ag) loaded with montmorillonite (Mont) and analyzed their antibacterial efficacy. At first the complexes were characterized using nuclear magnetic resonance (NMR), and amino acid-Ag complex-loaded Mont (amino acid-Ag-Mont) were characterized using X-ray diffraction (XRD) and scanning electron microscopy (SEM). The antibacterial efficacy of these materials in dental acrylic resin was then investigated by bacterial growth measurement using a spectrophotometer. As controls, commercially available silver-loaded zeolite and silver-zirconium phosphate were also tested. Dental acrylic resin incorporating His-Ag-Mont strongly inhibited Streptococcus mutans growth. This was explained by the fact that His-Ag complex revealed the highest amounts of silver ions in the presence of chloride. The structure of the amino acid-Ag complexes affected the silver ion presence in chloride and the antibacterial efficacy. His-Ag-Mont might be used as antibacterial agents for dental materials.

Long-term antibacterial activity and cytocompatibility of novel low-shrinkage-stress, remineralizing composites

A low-shrinkage-stress (LSS), antibacterial and remineralizing nanocomposite was recently developed; however, validation of its long-term antibacterial potency in modulating human salivary-derived biofilm is an unmet need. This study aimed to evaluate the antibacterial effect of the bioactive LSS composite before and after aging in acidic solution for 90 days using a multi-species biofilm model, and to evaluate its cytotoxicity. The LSS composite consisted of urethane dimethacrylate (UDMA) and triethylene glycol divinylbenzyl ether (TEG-DVBE), 3% dimethylaminohexadecyl methacrylate (DMAHDM) and 20% nanoparticles of amorphous calcium phosphate (NACP). Biofilm colony-forming units (CFU), lactic acid production, and confocal laser scanning microscopy (3D biofilm) were evaluated before and after three months of aging. Cytotoxicity was assessed against human gingival fibroblasts (HGF). The new LSS composite presented the lowest biofilm CFU, lactic acid and biofilm biomass, compared to controls (n = 6, p < 0.05). Importantly, the new composite exhibited no significant difference in antibacterial performance before and after 90-day-aging, demonstrating long-term antibacterial activity (p > 0.1). The LSS antibacterial and remineralizing composite presented a low cell viability at original extract that has increased with further dilutions. In conclusion, this study spotlighted that the new bioactive composite not only had a low shrinkage stress, but also down-regulated the growth of oral biofilms, reduced acid production, maintained antibacterial activity after the 90-day-aging, and did not compromise the cytocompatibility.

The regulation of hyphae growth in Candida albicans

In the last decades, Candida albicans has served as the leading causal agent of life-threatening invasive infections with mortality rates approaching 40% despite treatment. Candida albicans (C. albicans) exists in three biological phases: yeast, pseudohyphae, and hyphae. Hyphae, which represent an important phase in the disease process, can cause tissue damage by invading mucosal epithelial cells then leading to blood infection. In this review, we summarized recent results from different fields of fungal cell biology that are instrumental in understanding hyphal growth. This includes research on the differences among C. albicans phases; the regulatory mechanism of hyphal growth, extension, and maintaining cutting-edge polarity; cross regulations of hyphal development and the virulence factors that cause serious infection. With a better understanding of the mechanism on mycelium formation, this review provides a theoretical basis for the identification of targets in candidiasis treatment. It also gives some reference to the study of antifungal drugs.

Biocompatibility, mechanical, and bonding properties of a dental adhesive modified with antibacterial monomer and cross-linker

OBJECTIVES

This study investigated the antibacterial, cytotoxicity, and mechanical properties of a dental adhesive modified with quaternary ammonium monomer ((2-acryloyloxyethyl)dimethyldodecylammonium bromide) and cross-linker (bis(2-acryloyloxyethyl)methyldodecylammonium bromide).

MATERIALS AND METHODS

Monomer (M), cross-linker (C), or a combination of these (M + C) were incorporated into adhesive Adper Single Bond Plus (SB) in 5, 10, or 25% (as wt%). A colony-forming unit and MTT assays were used to evaluate antibacterial properties against Streptococcus mutans and cell viability. Resin-dentin beams (0.9 ± 0.1 mm²) were evaluated for micro-tensile bond strength (μTBS) after 24 h, 6 months, and 3 years. Hourglass specimens were evaluated for ultimate tensile strength (UTS) after 24 h, 1 week, and 6 months. Micro-hardness measurements after softening in ethanol were taken as an indirect assessment of the polymer cross-linking density. Kruskal-Wallis, one-way ANOVA, two-way ANOVA, and Student's t test were used for analysis of the antibacterial, cytotoxicity, μTBS, UTS, and hardness data, all with a significance level of p < 0.05.

RESULTS

10%M and 25%M demonstrated a significant reduction in S. mutans relative to SB (p < 0.001). No differences in cytotoxicity were detected for any of the groups. After 6 months, no changes in μTBS were shown for any of the groups. After 3 years, all groups evidenced a significant decrease in μTBS (p < 0.05) except 5%M, 5%C, and 5%M + 5%C. All groups demonstrated either stable or significantly increased UTS after 6 months. Except for the cross-linker groups, a significant decrease in micro-hardness was shown for all groups after softening in ethanol (p < 0.05).

CONCLUSIONS

A 5-10% of monomer may render the resin antibacterial without a compromise to its mechanical and bonding properties.

CLINICAL RELEVANCE

Biomodification of a resin adhesive with an antibacterial monomer and cross-linker may help improve the life span of adhesive restorations.

Bioactive low-shrinkage-stress nanocomposite suppresses S. mutans biofilm and preserves tooth dentin hardness

Recurrent dental caries is one of the main reasons for resin composite restoration failures. This study aimed to: (1) develop a bioactive, low-shrinkage-stress, antibacterial and remineralizing composite and evaluate the sustainability of its antibacterial effect against Streptococcus mutans (S. mutans) biofilms; and (2) evaluate the remineralization and cariostatic potential of the composite containing nanoparticles of amorphous calcium phosphate (NACP) and dimethylaminohexadecyl methacrylate (DMAHDM), using dentin hardness measurement and a biofilm-induced recurrent caries model. The antibacterial and remineralizing low-shrinkage-stress composite consisted of urethane dimethacrylate (UDMA) and triethylene glycol divinylbenzyl ether (TEG-DVBE), 3% DMAHDM and 20% NACP. S. mutans biofilm was used to evaluate antibiofilm activity, before and after 3 months of composite aging in acidic solution. Human dentin was used to develop a recurrent caries biofilm-model. Adding DMAHDM and NACP into low shrinkage-stress composite did not compromise the flexural strength. The low-shrinkage-stress composite with DMAHDM achieved substantial reductions in biofilm colony-forming units (CFU), lactic acid production, and biofilm biomass (p < 0.05). The low-shrinkage-stress DMAHDM+NACP composite exhibited no significant difference in antibacterial performance before and after 3 months of aging, demonstrating long-term antibacterial activity. Under S. mutans biofilm acidic attack, dentin hardness (GPa) was 0.24 ± 0.04 for commercial control, and 0.23 ± 0.03 for experimental control, but significantly higher at 0.34 ± 0.03 for DMAHDM+NACP group (p < 0.05). At an instrumental compliance of 0.33 μm/N, the polymerization shrinkage stress of the new composite was 36% lower than that of a traditional composite (p < 0.05). The triple strategy of antibacterial, remineralization and lower shrinkage-stress has great potential to inhibit recurrent caries and increase restoration longevity. Statement of Significance Polymerization shrinkage stress, masticatory load over time as well as biochemical degradation can lead to marginal failure and secondary caries. The present study developed a new low-shrinkage-stress, antibacterial and remineralizing dental nanocomposite. Polymerization shrinkage stress was greatly reduced, biofilm acid production was inhibited, and tooth dentin mineral and hardness were preserved. The antibacterial composite possessed a long-lasting antibiofilm effect against cariogenic bacteria S. mutans. The new bioactive nanocomposite has the potential to suppress recurrent caries at the restoration margins, protects tooth structures, and increases restoration longevity.

In vitro evaluation of composite containing DMAHDM and calcium phosphate nanoparticles on recurrent caries inhibition at bovine enamel-restoration margins

OBJECTIVE

Recurrent caries is a primary reason for restoration failure caused by biofilm acids. The objectives of this study were to: (1) develop a novel multifunctional composite with antibacterial function and calcium (Ca) and phosphate (P) ion release, and (2) investigate the effects on enamel demineralization and hardness at the margins under biofilms.

METHODS

Dimethylaminohexadecyl methacrylate (DMAHDM) and nanoparticles of amorphous calcium phosphate (NACP) were incorporated into composite. Four groups were tested: (1) Commercial control (Heliomolar), (2) Experimental control (0% DMAHDM + 0% NACP), (3) antibacterial group (3% DMAHDM + 0% NACP), (D) antibacterial and remineralizing group (3% DMAHDM + 30% NACP). Mechanical properties and Ca and P ion release were measured. Colony-forming units (CFU), lactic acid and polysaccharide of Streptococcus mutans (S. mutans) biofilms were evaluated. Demineralization of bovine enamel with restorations was induced via S. mutans, and enamel hardness was measured. Data were analyzed via one-way and two-way analyses of variance and Tukey's multiple comparison tests.

RESULTS

Adding DMAHDM and NACP into composite did not compromise the mechanical properties (P > 0.05). Ca and P ion release of 3% DMAHDM + 30% NACP was increased at cariogenic low pH. Biofilm lactic acid and polysaccharides were greatly decreased via DMAHDM, and CFU was reduced by 4 logs (P < 0.05). Under biofilm acids, enamel hardness at the margins was decreased to about 0.5 GPa for control; it was about 1 GPa for antibacterial group, and 1.3 GPa for antibacterial and remineralizing group (P < 0.05).

CONCLUSIONS

The novel 3% DMAHDM + 30% NACP composite had strong antibacterial effects. It substantially reduced enamel demineralization adjacent to restorations under biofilm acid attacks, yielding enamel hardness that was 2-fold greater than that of control composites. The novel multifunctional composite is promising to inhibit recurrent caries.

Novel CaF2 Nanocomposites with Antibacterial Function and Fluoride and Calcium Ion Release to Inhibit Oral Biofilm and Protect Teeth

(1) Background: The objective of this study was to develop a novel dental nanocomposite containing dimethylaminohexadecyl methacrylate (DMAHDM), 2-methacryloyloxyethyl phosphorylcholine (MPC), and nanoparticles of calcium fluoride (nCaF₂) for preventing recurrent caries via antibacterial, protein repellent and fluoride releasing capabilities. (2) Methods: Composites were made by adding 3% MPC, 3% DMAHDM and 15% nCaF₂ into bisphenol A glycidyl dimethacrylate (Bis-GMA) and triethylene glycol dimethacrylate (TEGDMA) (denoted BT). Calcium and fluoride ion releases were evaluated. Biofilms of human saliva were assessed. (3) Results: nCaF₂+DMAHDM+MPC composite had the lowest biofilm colony forming units (CFU) and the greatest ion release; however, its mechanical properties were lower than commercial control composite (p < 0.05). nCaF₂+DMAHDM composite had similarly potent biofilm reduction, with mechanical properties matching commercial control composite (p > 0.05). Fluoride and calcium ion releases from nCaF₂+DMAHDM were much more than commercial composite. Biofilm CFU on composite was reduced by 4 logs (n = 9, p < 0.05). Biofilm metabolic activity and lactic acid were also substantially reduced by nCaF₂+DMAHDM, compared to commercial control composite (p < 0.05). (4) Conclusions: The novel nanocomposite nCaF₂+DMAHDM achieved strong antibacterial and ion release capabilities, without compromising the mechanical properties. This bioactive nanocomposite is promising to reduce biofilm acid production, inhibit recurrent caries, and increase restoration longevity.

Synergetic Effect of 2-Methacryloyloxyethyl Phosphorylcholine and Mesoporous Bioactive Glass Nanoparticles on Antibacterial and Anti-Demineralisation Properties in Orthodontic Bonding Agents

2-methacryloyloxyethyl phosphorylcholine (MPC) is known to have antibacterial and protein-repellent effects, whereas mesoporous bioactive glass nanoparticles (MBN) are known to have remineralisation effects. We evaluated the antibacterial and remineralisation effects of mixing MPC and MBN at various ratios with orthodontic bonding agents. MPC and MBN were mixed in the following weight percentages in CharmFil-Flow (CF): CF, 3% MPC, 5% MPC, 3% MPC + 3% MBN, and 3% MPC + 5% MBN. As the content of MPC and MBN increased, the mechanical properties of the resin decreased. At 5% MPC, the mechanical properties decreased significantly with respect to CF (shear bond strength), gelation of MPC occurred, and no significant difference was observed in terms of protein adsorption compared to the control group. Composition 3% MPC + 5% MBN exhibited the lowest protein adsorption because the proportion of hydrophobic resin composite decreased; CF (91.8 ± 4.8 μg/mL), 3% MPC (73.9 ± 2.6 μg/mL), 3% MPC + 3% MBN (69.4 ± 3.6 μg/mL), and 3% MPC + 5% MBN (55.9 ± 1.6 μg/mL). In experiments against S. mutans and E. coli, addition of MPC and MBN resulted in significant antibacterial effects. In another experiment, the anti-demineralisation effect was improved when MPC was added, and when MBN was additionally added, it resulted in a synergetic effect. When MPC and MBN were added at an appropriate ratio to the orthodontic bonding agents, the protein-repellent, antibacterial, and anti-demineralisation effects were improved. This combination could thus be an alternative way of treating white spot lesions.

Chemistry of novel and contemporary resin-based dental adhesives

The chemistry of resin-based dental adhesives is critical for its interaction with dental tissues and long-term bonding stability. Changes in dental adhesives composition influences the materials' key physical-chemical properties, such as rate and degree of conversion, water sorption, solubility, flexural strength and modulus, and cohesive strength and improves the biocompatibility to dental tissues. Maintaining a suitable reactivity between photoinitiators and monomers is important for optimal properties of adhesive systems, in order to enable adequate polymerisation and improved chemical, physical and biological properties. The aim of this article is to review the current state-of-the-art of dental adhesives, and their chemical composition and characteristics that influences the polymerisation reaction and subsequent materials properties and performance.

Rechargeable anti-microbial adhesive formulation containing cetylpyridinium chloride montmorillonite

Long-term anti-bacterial effect is a desired ability of any dental material in combating tooth caries as one of the most common and widespread persistent diseases today. Among several cationic quaternary ammonium compounds with antiseptic properties, cetylpyridinium chloride (CPC) is often used in mouthrinses and toothpastes. In this study, we incorporated CPC in a soft phyllosilicate mineral (clay), referred to as montmorillonite (Mont), to enable gradual CPC release with rechargeability. Besides measuring CPC release and recharge, we examined the anti-bacterial effect, cytotoxicity and bonding effectiveness of five experimental adhesive formulations, prepared by adding 1 and 3 wt% CPC_Mont, 3 wt% Mont (without CPC), and 1 and 3 wt% CPC (without Mont) to the commercial adhesive Clearfil S³ Bond ND Quick ('C-S³B'; Kuraray Noritake). Strong inhibition of Streptococcus mutans biofilm formation by CPC_Mont adhesives was confirmed by optical density and SEM. CPC release from CPC_Mont adhesives was higher and lasted longer than from CPC adhesives, while CPC_Mont adhesives could also be recharged with CPC upon immersion in 2 wt% CPC. In conclusion, CPC_Mont technology rendered adhesives anti-bacterial properties with recharge ability, this without reducing its bonding potential, neither increasing its cytotoxicity. STATEMENT OF SIGNIFICANCE: Dental caries is one of the most prevalent chronic diseases in the population worldwide and is the major cause of tooth loss. In this study, we developed cetylpyridinium chloride (CPC) loaded montmorillonite (CPC-Mont) with a long-term antibacterial efficacy to prevent caries. CPC is an antibacterial agent approved by FDA, used as an OTC drug and contained in oral hygiene aids. CPC-Mont was incorporated in a dental adhesive to gradually release CPC. CPC_Mont technology rendered adhesives anti-bacterial properties with rechargeability, this without reducing its bonding potential, neither increasing its cytotoxicity.

Effects of Addition of Quaternary Ammonium Antimicrobial Compounds into Root Canal Sealers

Objective The aim of this study is to determine the effect of the addition of benzalkonium chloride and cetylpyridinium chloride in three commercial root canal sealers.

Materials and Methods Three different root canal sealers were used: EndoRez, N2, and Apexit Plus. The samples were prepared by mixing the components according to the manufacturers’ guidelines and adding 2% in weight of the antimicrobials to the newly mixed cement. The paste was placed in molds and stored in an incubator (37°C, 24 h). The samples were then stored in 5-mL distilled water. Samples without antimicrobials served as a control. All samples were tested at 3 time intervals: 1 day, 1 week, and 1 month following their storage in distilled water. The impact of the antimicrobials on the solubility of the sealers, the release of chloride ions (Cl ^— ), and the pH value were examined.

Statistical Analysis Analysis was done using one-way analysis of variance and the post hoc Tukey's honestly significant difference test.

Results Chloride ions are present in storage media with EndoRez, N2, and Apexit Plus samples (without antimicrobials) following all tested storage intervals. The addition of the antimicrobials increased the release of chloride ions. Endodontic cements without addition of antimicrobials show an increase in weight after 1 month. The highest pH value is measured in Apexit Plus samples. The solutions in which N2 samples (with and without addition of antimicrobials) were stored did not have a significant change in their pH, while in the EndoRez solutions, a significant decrease in the pH value after the first week was measured.

Conclusions The addition of antimicrobials might lead to improved characteristics of the root canal sealers.

Experimental composites containing quaternary ammonium methacrylates reduce demineralization at enamel-restoration margins after cariogenic challenge

OBJECTIVE

This study evaluated the influence of experimental composites containing quaternary ammonium monomers (QAM) at different concentrations and alkyl chains on demineralization at enamel-composite margins after cariogenic challenge.

METHODS

Standardized 4×4mm cavities were cut into 35 bovine enamel blocks, which were randomly divided into seven groups (n=5) and restored with the following experimental composites and commercial materials: (G12.5) - 5% dimethylaminododecyl methacrylate (DMADDM) with a 12-carbon alkyl chain (G12.10) - 10% DMADDM, (G16.5) - 5% dimethylaminohexadecyl methacrylate (DMAHDM) with a 16-carbon alkyl chain (G16.10) - 10% DMAHDM, (CG) - control group (without QAM), (GZ250) - commercial composite (Filtek Z250^®), and (GIC) - glass ionomer cement (Maxxion R^®). After restorative procedures, initial microhardness was measured and experimental composites were subjected to Streptococcus mutans biofilm formation for 48h. After cariogenic challenge, the samples were washed and microhardness was reassessed. A 3D non-contact profilometer was used to determine surface roughness and enamel demineralization was assessed by micro-CT. Microhardness results were analyzed by the Kruskal-Wallis and Mann-Whitney tests and micro-CT results were analyzed by Tukey's HSD test (95% confidence interval).

RESULTS

None of the materials could prevent mineral loss at the enamel-restoration margins. The addition of 10% DMAHDM yielded the lowest, albeit statistically significant, mineral loss (p<0.05). 3D non-contact profilometry showed enamel surface roughness modification after biofilm exposure. The CG had the highest roughness values. Micro-CT analysis revealed mineral loss, except for GIC.

SIGNIFICANCE

The addition of 10% QAM with a 16-carbon chain in experimental composites reduced mineral loss at the enamel-restoration margins after cariogenic challenge.

Hydrophobic and antimicrobial dentin: A peptide-based 2-tier protective system for dental resin composite restorations

Dental caries, i.e., tooth decay mediated by bacterial activity, is the most widespread chronic disease worldwide. Carious lesions are commonly treated using dental resin composite restorations. However, resin composite restorations are prone to recurrent caries, i.e., reinfection of the surrounding dental hard tissues. Recurrent caries is mainly a consequence of waterborne and/or biofilm-mediated degradation of the tooth-restoration interface through hydrolytic, acidic and/or enzymatic challenges. Here we use amphipathic antimicrobial peptides to directly coat dentin to provide resin composite restorations with a 2-tier protective system, simultaneously exploiting the physicochemical and biological properties of these peptides. Our peptide coatings modulate dentin's hydrophobicity, impermeabilize it, and are active against multispecies biofilms derived from caries-active individuals. Therefore, the coatings hinder water penetration along the otherwise vulnerable dentin/restoration interface, even after in vitro aging, and increase its resistance against degradation by water, acids, and saliva. Moreover, they do not weaken the resin composite restorations mechanically. The peptide-coated highly-hydrophobic dentin is expected to notably improve the service life of resin composite restorations and to enable the development of entirely hydrophobic restorative systems. The peptide coatings were also antimicrobial and thus, they provide a second tier of protection preventing re-infection of tissues in contact with restorations. STATEMENT OF SIGNIFICANCE: We present a technology using designer peptides to treat the most prevalent chronic disease worldwide; dental caries. Specifically, we used antimicrobial amphipathic peptides to coat dentin with the goal of increasing the service life of the restorative materials used to treat dental caries, which is nowadays 5 years on average. Water and waterborne agents (enzymes, acids) degrade restorative materials and enable re-infection at the dentin/restoration interface. Our peptide coatings will hinder degradation of the restoration as they produced highly hydrophobic and antimicrobial dentin/material interfaces. We anticipate a high technological and economic impact of our technology as it can notably reduce the lifelong dental bill of patients worldwide. Our findings can enable the development of restorations with all-hydrophobic and so, more protective components.

Short-Time Antibacterial Effects of Dimethylaminododecyl Methacrylate on Oral Multispecies Biofilm In Vitro

Quaternary ammonium compounds constitute a large group of antibacterial chemicals with a potential for inhibiting dental plaque. The aims of this study were to evaluate short-time antibacterial and regulating effects of dimethylaminododecyl methacrylate (DMADDM) on multispecies biofilm viability, reformation, and bacterial composition in vitro. DMADDM, chlorhexidine (CHX), and sodium fluoride (NaF) were chosen in the present study. Streptococcus mutans, Streptococcus sanguinis, and Streptococcus gordonii were used to form multispecies biofilm. Cytotoxicity assay was used to determine the optimal tested concentration. 3-(4,5-dimethyl-thiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay and resazurin test of biofilm were conducted to study the biomass changes and metabolic changes of controlled multispecies biofilm. Scanning electron microscopy (SEM) was used to observe biofilm images. TaqMan real-time polymerase chain reaction was performed to evaluate the proportion change in multispecies biofilm of different groups. Cytotoxicity assay showed that there existed a certain concentration application range for DMADDM, CHX, and NaF. MTT assay and resazurin test results showed that DMADDM and CHX groups decreased multispecies biofilm growth and metabolic activity (p < 0.05), no matter after 1 min or 5 min direct contact killing or after 24 h regrowth. The proportion of S. mutans decreased steadily in DMADDM and CHX groups after 1 min and 5 min direct contact killing and 24 h regrowth, compared to control groups. A novel DMADDM-containing solution was developed, achieving effective short-time antibacterial effects and regulation ability of biofilm formation.

A photo-crosslinked hybrid interpenetrating polymer network (IPN) for antibacterial coatings on denture base materials

An interpenetrating polymer network (IPN) structured antibacterial layer was prepared on dental base materials using a one-step photo-crosslinking method.

Effects of water aging on the mechanical and anti-biofilm properties of glass-ionomer cement containing dimethylaminododecyl methacrylate

OBJECTIVES

The aims of this study were to investigate the effects of water aging for up to 6months on the mechanical and anti-biofilm properties of a novel antibacterial glass ionomer cement (GIC) containing dimethylaminododecyl methacrylate (DMADDM).

METHODS

GIC specimens (n=180) which contained DMADDM (0wt.%, 1.1wt.% or 2.2wt.%) were prepared. The mechanical properties surface roughness, microhardness and the surface charge density of ammonium groups were measured before and after water aging for 3 and 6months at 37°C. Further six months aged specimens (n=216) were worn by 6 volunteers in their oral cavities for 24h and 72h. Biofilm formation was analyzed and rated by fluorescence microscopy (FM) and by scanning electron microscopy (SEM). Biofilm viability was analyzed by FM.

RESULTS

Water aging did not show any adverse effects on the surface roughness and hardness of the material. The surface charge density of the GIC samples containing DMADDM decreased due to the aging procedure, however, was still higher than that of the GIC without DMADDM. In situ biofilm formation was significantly reduced after 24h on DMADDM containing GIC (p<0.05). FM results showed a higher ratio of red/green fluorescence on GIC-DMADDM samples.

SIGNIFICANCE

Incorporating DMADDM into GIC affected the material properties in a tolerable manner even after 6months of storage in water. The new GIC is a promising material to affect the biofilm formation on the surface of restorations.

Protein-repellent nanocomposite with rechargeable calcium and phosphate for long-term ion release

OBJECTIVE

There has been no report on the effect of incorporating protein repellent 2-methacryloyloxyethyl phosphorylcholine (MPC) into a composite containing nanoparticles of amorphous calcium phosphate (NACP) on calcium (Ca) and phosphate (P) ion rechargeability. The objectives of this study were to develop a Ca and P ion-rechargeable and protein-repellent composite for the first time, and investigate the effects of MPC and NACP on mechanical properties, protein-repellency, anti-biofilm effects, and Ca and P ion recharge and re-release.

METHODS

NACP were synthesized using a spray-drying technique. The resin contained ethoxylated bisphenol A dimethacrylate (EBPADMA) and pyromellitic glycerol dimethacrylate (PMGDM). Three NACP composites were made with 0 (control), 1.5%, and 3% of MPC. NACP (20%) and glass particles (50%) were also added into the resin. Protein adsorption was measured using a micro-bicinchoninic acid (BCA) method. A human saliva microcosm biofilm model was used to determine biofilm metabolic activity, lactic acid, and colony-forming units (CFU). Ca and P ion recharge and re-release were measured using a spectrophotometric method.

RESULTS

Flexural strengths and moduli of CaP-rechargeable composites matched those of a commercial composite without CaP rechargeability (p>0.1). Adding 1.5% and 3% MPC reduced protein adsorption to 1/3 and 1/5, respectively, that of commercial composite (p<0.05). Adding 3% MPC suppressed biofilm metabolic activity and lactic acid production, and reduced biofilm CFU by nearly 2 logs. All three NACP composites had excellent ion rechargeability and higher levels of ion re-releases. One recharge yielded continuous ion release for 21 days. The release was maintained at the same level with increasing number of recharge cycles, indicating long-term ion release. Incorporation of MPC did not compromise the CaP ion rechargeability.

SIGNIFICANCE

Incorporating 3% MPC into NACP nanocomposite greatly reduced protein adsorption, biofilm growth and lactic acid, decreasing biofilm CFU by nearly 2 logs, without compromising Ca and P recharge. This protein-repellent NACP-MPC rechargeable composite with long-term remineralization is promising for tooth restorations to inhibit secondary caries.

Developing a New Generation of Therapeutic Dental Polymers to Inhibit Oral Biofilms and Protect Teeth

Polymeric tooth-colored restorations are increasingly popular in dentistry. However, restoration failures remain a major challenge, and more than 50% of all operative work was devoted to removing and replacing the failed restorations. This is a heavy burden, with the expense for restoring dental cavities in the U.S. exceeding $46 billion annually. In addition, the need is increasing dramatically as the population ages with increasing tooth retention in seniors. Traditional materials for cavity restorations are usually bioinert and replace the decayed tooth volumes. This article reviews cutting-edge research on the synthesis and evaluation of a new generation of bioactive dental polymers that not only restore the decayed tooth structures, but also have therapeutic functions. These materials include polymeric composites and bonding agents for tooth cavity restorations that inhibit saliva-based microcosm biofilms, bioactive resins for tooth root caries treatments, polymers that can suppress periodontal pathogens, and root canal sealers that can kill endodontic biofilms. These novel compositions substantially inhibit biofilm growth, greatly reduce acid production and polysaccharide synthesis of biofilms, and reduce biofilm colony-forming units by three to four orders of magnitude. This new class of bioactive and therapeutic polymeric materials is promising to inhibit tooth decay, suppress recurrent caries, control oral biofilms and acid production, protect the periodontium, and heal endodontic infections.

Chlorhexidine-encapsulated mesoporous silica-modified dentin adhesive

OBJECTIVES

This work aims to explore the feasibility of chlorhexidine-encapsulated mesoporous silica (CHX@pMSN) as a modifier of a commercial dental adhesive via the evaluation of physicochemical properties and antibacterial capabilities of adhesive-dentin interface.

METHODS

Therapeutic adhesives were developed in the present study by incorporating CHX@pMSN into a commercial adhesive at four mass fractions (0, 1, 5 and 10 wt.%). The antibacterial capability on Streptococcus mutans (S. mutans) biofilm, conversion degree, adhesive morphology, microtensile bond strength (MTBS) and nanoleakage expression were evaluated comprehensively.

RESULTS

MTT and CLSM evaluation showed that CHX@pMSN-doped adhesive inhibits S. mutans biofilm growth, while CHX is released from the modified adhesive continuously. The incorporation of CHX@pMSN did not affect immediate bond strength at the concentration of 1% and 5% (P >  0.05). Moreover, these bonds were mainly preserved in 5% CHX@pMSN group after one month of collagenase ageing. Meanwhile, CHX@pMSN-doped adhesive groups exhibited similar nanoleakage distribution compared with the control.

CONCLUSION

This study showed that the 5% CHX@pMSN-modified adhesive achieved balance amongst unaffected immediate bonding strength, well-preserved bonds against collagenase ageing and effective inhibition of S. mutans biofilm growth.

CLINICAL SIGNIFICANCE

CHX@pMSN-modified dentin adhesive can potentially extend the service life of adhesive restoration in clinic.

Effects of water-aging for 6 months on the durability of a novel antimicrobial and protein-repellent dental bonding agent

Biofilms at the tooth-restoration bonded interface can produce acids and cause recurrent caries. Recurrent caries is a primary reason for restoration failures. The objectives of this study were to synthesize a novel bioactive dental bonding agent containing dimethylaminohexadecyl methacrylate (DMAHDM) and 2-methacryloyloxyethyl phosphorylcholine (MPC) to inhibit biofilm formation at the tooth-restoration margin and to investigate the effects of water-aging for 6 months on the dentin bond strength and protein-repellent and antibacterial durability. A protein-repellent agent (MPC) and antibacterial agent (DMAHDM) were added to a Scotchbond multi-purpose (SBMP) primer and adhesive. Specimens were stored in water at 37 °C for 1, 30, 90, or 180 days (d). At the end of each time period, the dentin bond strength and protein-repellent and antibacterial properties were evaluated. Protein attachment onto resin specimens was measured by the micro-bicinchoninic acid approach. A dental plaque microcosm biofilm model was used to test the biofilm response. The SBMP + MPC + DMAHDM group showed no decline in dentin bond strength after water-aging for 6 months, which was significantly higher than that of the control (P < 0.05). The SBMP + MPC + DMAHDM group had protein adhesion that was only 1/20 of that of the SBMP control (P < 0.05). Incorporation of MPC and DMAHDM into SBMP provided a synergistic effect on biofilm reduction. The antibacterial effect and resistance to protein adsorption exhibited no decrease from 1 to 180 d (P > 0.1). In conclusion, a bonding agent with MPC and DMAHDM achieved a durable dentin bond strength and long-term resistance to proteins and oral bacteria. The novel dental bonding agent is promising for applications in preventive and restorative dentistry to reduce biofilm formation at the tooth-restoration margin.

Nanostructured Polymeric Materials with Protein-Repellent and Anti-Caries Properties for Dental Applications

Dental caries is prevalent worldwide. Tooth cavity restorations cost more than $46 billion annually in the United States alone. The current generation of esthetic polymeric restorations have unsatisfactory failure rates. Replacing the failed restorations accounts for 50–70% of all the restorations. This article reviewed developments in producing a new generation of bioactive and therapeutic restorations. This includes: Protein-repellent and anti-caries polymeric dental composites, especially the use of 2-methacryloyloxyethyl phosphorylcholine (MPC) and dimethylaminododecyl methacrylate (DMAHDM); protein-repellent adhesives to greatly reduce biofilm acids; bioactive cements to inhibit tooth lesions; combining protein-repellency with antibacterial nanoparticles of silver; tooth surface coatings containing calcium phosphate nanoparticles for remineralization; therapeutic restorations to suppress periodontal pathogens; and long-term durability of bioactive and therapeutic dental polymers. MPC was chosen due to its strong ability to repel proteins. DMAHDM was selected because it had the most potent antibacterial activity when compared to a series of antibacterial monomers. The new generation of materials possessed potent antibacterial functions against cariogenic and periodontal pathogens, and reduced biofilm colony-forming units by up to 4 logs, provided calcium phosphate ions for remineralization and strengthening of tooth structures, and raised biofilm pH from a cariogenic pH 4.5 to a safe pH 6.5. The new materials achieved a long-term durability that was significantly beyond current commercial control materials. This new generation of bioactive and nanostructured polymers is promising for wide applications to provide therapeutic healing effects and greater longevity for dental restorations.

Antibacterial quaternary ammonium compounds in dental materials: A systematic review

OBJECTIVE

Quaternary ammonium compounds (QACs) represent one of the most effective classes of disinfectant agents in dental materials and resin nanocomposites. This reviews aims to give a wide overview on the research in the field of antibacterial QACs in dental materials and nanocomposites.

METHOD

An introduction to dental materials components as well as the microorganisms and methods of evaluation for the antimicrobial assays are presented. Then, the properties and synthesis route of QACs, as monomer and filler, are shown. Finally, antimicrobial monomers and fillers, specifically those contain quaternary ammonium salts (QASs), in dental materials are reviewed.

RESULTS

QACs have been used as monomer and micro/nanofiller in restorative dentistry. They possess one or more methacrylate functional groups to participate in polymerization reactions. QACs with multiple methacrylate groups can also be used as crosslinking agents. Furthermore, QACs with chain length from ∼12 to 16 have higher antimicrobial activity in cured dental resins. In general, increasing the chain length leads to a threshold value (critical point) and then it causes decrease in the antimicrobial activity.

SIGNIFICANCE

The current state of the art of dental materials and resin nanocomposites includes a wide variety of antimicrobial materials. Among them, QACs presents low cytotoxicity and excellent long-term antimicrobial activity without leaching out over time.

Novel rechargeable calcium phosphate nanocomposite with antibacterial activity to suppress biofilm acids and dental caries

OBJECTIVE

Rechargeable calcium phosphate (CaP) composites were developed recently. However, none of the rechargeable CaP composites was antibacterial. The objectives of this study were to develop the first rechargeable CaP composite that was antibacterial, and to investigate the effects of adding dimethylaminohexadecyl methacrylate (DMAHDM) into rechargeable CaP composite on ion rechargeability and re-release as well as biofilm properties.

METHODS

DMAHDM was synthesized via a Menschutkin reaction. Nanoparticles of amorphous calcium phosphate (NACP) were synthesized using a spray-drying technique. The resin contained ethoxylated bisphenol A dimethacrylate (EBPADMA) and pyromellitic glycerol dimethacrylate (PMGDM). Two composites were fabricated: rechargeable NACP composite, and rechargeable NACP-DMAHDM composite. Mechanical properties and ion release and recharge were measured. A dental plaque microcosm biofilm model using saliva was tested.

RESULTS

Flexural strength and elastic modulus of rechargeable NACP and NACP-DMAHDM composites matched commercial control composite (p > 0.1). NACP-DMAHDM inhibited biofilm metabolic activity and lactic acid, and reduced biofilm colony-forming units (CFU) by 3-4 log. NACP and NACP-DMAHDM showed similar Ca and P ion recharge and re-release (p > 0.1). Therefore, adding DMAHDM did not compromise the ion rechargeability. One recharge yielded continuous release for 42 d. The release was maintained at the same level with increasing number of recharge cycles, indicating long-term ion release and remineralization capability.

CONCLUSIONS

The first CaP rechargeable and antibacterial composite was developed. Adding DMAHDM into the rechargeable NACP composite did not adversely affect the Ca and P ion release and recharge, and the composite had much less biofilm growth and lactic acid production, with CFU reduction by 3-4 log.

CLINICAL SIGNIFICANCE

This novel CaP rechargeable composite with long-term remineralization and antibacterial properties is promising for tooth restorations to inhibit caries.

High-performance therapeutic quercetin-doped adhesive for adhesive-dentin interfaces

Almost half of dental restorations have failed in less than 10 years, and approximately 60% of practice time has been consumed to replace these dental restorations. As such, contemporary dentin adhesives should be modified to treat secondary caries and prevent the degradation of adhesive–dentin interfaces. To achieve this goal, we developed a versatile therapeutic adhesive in the present study by incorporating quercetin, which is a naturally derived plant extract, into a commercial adhesive at three concentrations (100, 500 and 1000 µg/mL). An unmodified adhesive served as a control. The antibacterial ability on Streptococcus mutans biofilm, conversion degree, microtensile bond strength, failure modes, in situ zymography, nanoleakage expression and cytotoxicity of quercetin-doped adhesive were comprehensively evaluated. Results showed that the quercetin-doped adhesive (500 µg/mL) preserved its bonding properties against collagenase ageing and inhibited the growth of S. mutans biofilm. Efficient bonding interface sealing ability, matrix metalloproteinase inhibition and acceptable biocompatibility were also achieved. Thus, a simple, safe and workable strategy was successfully developed to produce therapeutic adhesives for the extension of the service life of adhesive restorations.