Synthesis of new antibacterial quaternary ammonium monomer for incorporation into CaP nanocomposite

Trends in pH-triggered strategies for dental resins aiming to assist in preventing demineralization: A scoping review

OBJECTIVES

To identify and map the literature on the current state of pH-triggered strategies for resin-based materials used in direct restorative dentistry, focusing on innovative compounds, their incorporation and evaluation methods, and the main outcomes.

DATA AND SOURCES

Through a search across PubMed, Scopus, Embase, Web of Science, LILACS, Cochrane Library databases, and Google Scholar, this review identified studies pertinent to pH-responsive dental materials, excluding resin-modified glass ionomer cements.

STUDY SELECTION

From the 981 records identified, 19 in vitro studies were included, concentrating on resin-based composite resins (50 %), dentin adhesives (25 %), and sealants (25 %). The review identified diverse pH-triggered strategies based on ion release, antibacterial release, antibacterial no release, association of contact-antibacterial compounds with acid neutralizer, and combined ion and antibacterial releasing systems for the development of pH-responsive dental materials. Despite the incorporation of innovative compounds such as nanoparticulated amorphous calcium phosphate (20 %), tetracalcium phosphate (40 %), chlorhexidine-loaded mesoporous silica nanoparticles (10 %), tertiary amine dodecylmethylaminoethyl methacrylate (5 %), and bioactive glass with 4 % nano-POSS (20 %), the mechanical integrity of the materials remained satisfactory, displaying flexural strength and elastic modulus that were similar to or better than control. Materials showcased pH-dependent release of calcium and phosphate ions, especially in acidic conditions, and potential for prevention of tooth demineralization, indicating decreased mineral loss and lesion depth.

CONCLUSIONS

In general, ion releasing and antibacterial-based strategies alone or associated, comprising the incorporation of amorphous calcium phosphate, tetracalcium phosphate, chlorhexidine-loaded mesoporous silica nanoparticles, tertiary amine dodecylmethylaminoethyl methacrylate, and bioactive glass with 4 % nano-POSS were used to provide pH-responsiveness for composite resins, adhesive systems, or sealants, without compromise of the mechanical properties, and with promising potential for enhancing caries prevention.

CLINICAL RELEVANCE

Advancements on smart pH-responsive dental resins based on ion-releasing and antibacterial associated strategies may contribute to prevent or reduce bacterial acid formation and demineralization of tooth structure at the interface between tooth tissues and restoration, possibly favoring the success of restorative treatment in the future.

Microbial Adhesion and Cytotoxicity of Heat-Polymerized and 3D-Printed Denture Base Materials when Modified with Dimethylaminohexadecyl Methacrylate and/or 2-Methacryloyloxyethyl Phosphorylcholine as Antimicrobial and Protein-Repellent Materials

BACKGROUND

Polymethyl methacrylate (PMMA) is ideal for denture bases but is prone to biofilm accumulation, leading to denture stomatitis (DS), often involving Candida albicans. Dimethylaminohexadecyl methacrylate (DMAHDM) and 2-methacryloyloxyethyl phosphorylcholine (MPC) are introduced into dental materials for their antimicrobial and protein-repellent properties. This study investigates the effects of incorporating dimethylaminohexadecyl methacrylate (DMAHDM) and 2-methacryloyloxyethyl phosphorylcholine (MPC) into heat-polymerized (HP) and 3D-printed (3DP) denture base resins on microbial adhesion and cytotoxicity.

METHODS

HP and 3DP denture base specimens were prepared using varying concentrations of DMAHDM and MPC. Microbial adhesion was quantified using CFU counts of C. albicans, and cytotoxicity was assessed via an MTT assay using fibroblast cells after 24 h, 3 days, and 7 days.

RESULTS

Both DMAHDM and MPC significantly reduced the CFU counts in both HP and 3DP materials; the combination of 1.5% DMAHDM and 3% MPC exhibited the most substantial antimicrobial effects. Cytotoxicity results varied between materials and time points; however, all treated groups maintained cell viability above the 70% threshold, indicating no significant cytotoxic effects.

CONCLUSION

Incorporating DMAHDM and MPC into denture base resins can effectively reduce microbial adhesion while maintaining acceptable cytotoxicity levels.

The Effect of Incorporating Dimethylaminohexadecyl Methacrylate and/or 2-Methacryloyloxyethyl Phosphorylcholine on Flexural Strength and Surface Hardness of Heat Polymerized and 3D-Printed Denture Base Materials

BACKGROUND

A major disadvantage of polymethyl methacrylate (PMMA) acrylic resins is susceptibility to biofilm accumulation. The incorporation of antimicrobial agents is a reliable prevention technique. The purpose of this study is to investigate the effect of incorporating dimethylaminohexadecyl methacrylate (DMAHDM) and/or 2-methacryloyloxyethyl phosphorylcholine (MPC) into heat-polymerized (HP) and 3D-printed (3DP) denture base materials on the flexural strength, modulus of elasticity, and surface hardness.

METHODS

DMAHDM and/or MPC were mixed with the acrylic resin liquid of a heat-polymerized (ProBase Hot) and a 3D printed (NextDent Denture 3D) material at mass fractions of 1.5% and 3% and a combination of 3% MPC and 1.5% DMAHDM.

RESULTS

Significant differences in mechanical properties between the control and experimental groups have been detected (p-value < 0.0001). In HP materials, the addition of DMAHDM and/or MPC generally decreased the flexural strength, from (151.18 MPa) in G1 down to (62.67 MPa) in G5, and surface hardness, from (18.05 N/mm2) down to (10.07 N/mm2) in G5. Conversely, in 3DP materials, flexural strength was slightly enhanced, from (58.22 MPa) in G1 up to (62.76 MPa) in G6, although surface hardness was consistently reduced, from (13.57 N/mm2) down to (5.29 N/mm2) in G5.

CONCLUSION

It is recommended to carefully optimize the concentrations of DMAHDM and/or MPC to maintain mechanical integrity.

Mechanical and Antimicrobial Properties of Boron Nitride/Methacrylic Acid Quaternary Ammonium Composites Reinforced Dental Flowable Resins

Dental resin composites (DRCs) are commonly used to restore teeth affected by dental caries or defects. These materials must possess excellent properties to withstand the complex oral environment. The objective of this study was to prepare and characterize Boron nitride nanosheets (BNN)/ dimethyl amino hexadecyl methacrylate (DMAHDM) composites (BNN/DMA), and to evaluate them as functional fillers to enhance the mechanical and antimicrobial properties of dental resins. The BNN/DMA composites were successfully prepared under the theoretical guidance of molecular dynamics (MD), and then the physicochemical and morphological characterization of the BNN/DMA composites were carried out by using various test methods, such as FT-IR, XRD, UV-vis spectroscopy, SEM, TEM, and AFM. It was doped into the dental flowable resin in a certain proportion, and the results showed that the flexural strength (FS), elastic modulus (EM), compressive strength (CS), and microhardness (MH) of the modified resin composites were increased by 53.29, 47.8, 97.59, and 37.1%, respectively, with the addition of 0.8 wt % of BNN/DMA composite fillers. It has a good inhibition effect on Streptococcus mutans, with an inhibition rate as high as 90.43%. Furthermore, this effect persists even after one month of aging. In conclusion, the modification of flowable resins with low-concentration BNN/DMA composites favorably integrates the mechanical properties and long-term antimicrobial activity of dental resins. At the same time, they have good biocompatibility and do not affect the aesthetics. The BNN/DMA composite modified flowable resin has the potential to become a new type of antimicrobial dental restorative material.

New generation of orthodontic devices and materials with bioactive capacities to improve enamel demineralization

OBJECTIVE

The article reviewed novel orthodontic devices and materials with bioactive capacities in recent years and elaborated on their properties, aiming to provide guidance and reference for future scientific research and clinical applications.

DATA, SOURCES AND STUDY SELECTION

Researches on remineralization, protein repellent, antimicrobial activity and multifunctional novel bioactive orthodontic devices and materials were included. The search of articles was carried out in Web of Science, PubMed, Medline and Scopus.

CONCLUSIONS

The new generation of orthodontic devices and materials with bioactive capacities has broad application prospects. However, most of the current studies are limited to in vitro studies and cannot explore the true effects of various bioactive devices and materials applied in oral environments. More research, especially in vivo researches, is needed to assist in clinical application.

CLINICAL SIGNIFICANCE

Enamel demineralization (ED) is a common complication in orthodontic treatments. Prolonged ED can lead to dental caries, impacting both the aesthetics and health of teeth. It is of great significance to develop antibacterial orthodontic devices and materials that can inhibit bacterial accumulation and prevent ED. However, materials with only preventive effect may fall short of addressing actual needs. Hence, the development of novel bioactive orthodontic materials with remineralizing abilities is imperative. The article reviewed the recent advancements in bioactive orthodontic devices and materials, offering guidance and serving as a reference for future scientific research and clinical applications.

Cytotoxicity evaluation, antibacterial effect, and degree of conversion of QAM-containing adhesives

The aim of this study was to evaluate the influence of adding quaternary ammonium methacrylates (QAMs) to experimental adhesives by assessing the degree of conversion (DC), cytotoxicity against keratinocytes and fibroblasts, and antibacterial activity against biofilm formation. Two QAMs were added to an experimental adhesive: dimethylaminododecyl methacrylate bromododecane (DMADDM) or dimethylaminododecyl methacrylate bromohexadecane (DMAHDM) at three concentrations each: 1, 2.5, and 5 wt.%. Experimental adhesive without QAMs (control group) and commercially available Transbond XT Primer (3M Unitek, Monrovia, California, USA) were used for comparisons. The adhesives were tested for DC, cytotoxicity against keratinocytes and fibroblasts, and antibacterial activity against biofilm formation. DC, cytotoxicity against fibroblasts, and antibacterial activity were analyzed using one-way ANOVA and Tukey's multiple comparisons. Cytotoxicity against keratinocytes was evaluated using the Kruskal Wallis and Dunn's post-hoc (α = 5%) tests. Transbond showed lower DC as compared to 5% DMAHDM, 1% DMADDM, and 5% DMADDM (p < 0.05). However, all groups presented proper DC when compared to commercial adhesives in the literature. In the evaluation of cytotoxicity against keratinocytes, Transbond induced higher viability than 2.5 wt.% groups (p < 0.05). Against fibroblasts, Transbond induced higher viability as compared to 5 wt.% groups (p < 0.05). DMAHDM at 5 wt.% reduced biofilm formation when compared to all the other groups (p < 0.05). Despite their cytotoxic effect against keratinocytes, gingival fibroblasts showed higher viability. DMAHDM at 5 wt.% decreased Streptococcus mutans viability. The incorporation of DMAHDM at 5 wt.% may be a strategy for reducing the development of white spot lesions.

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.

Multinary nanocomposite of GO@SrO@CoCrO3@FeCr2O4@SnO2@SiO2 for superior electrochemical performance and water purification applications

Novel multinary nanocomposite using solvothermal method synthesized and studied for their use in supercapacitors and photocatalysis to degrade pollutants using characterization techniques XRD, SEM, EDX, FTIR, Raman, UV-Vis, Zeta potential and photoluminescence spectroscopy whereas electrochemical testing via EIS, CV and GCD analysis. Average crystalline size of 20.81 nm measured from XRD whereas EDX confirms GO suppression within nanocomposite. Mixed matrix like morphology is observable from SEM micrographs. The composite exhibited a band gap of 2.78 eV that could degrade MB dye at 94 % under direct sunlight consistent with first-order kinetics. Multiple distinctive peaks in FTIR spectra indicates various functional groups exsistence in the material alongwith zeta potential value of -17.9 mV. Raman spectra reveals D-band shifting to value 1361 cm-1 while the G-band shifts to 1598 cm-1 relative to GO. Furthermore electrochemical performance evaluated revealing electron transfer rate value 4.88 × 10-9 cms-1 with maximum capacitance about 7182 Fg-1 at a scan rate of 10 mVs-1 respectively. Power density ranges from 3591.18 to 2163 W/kg and energy density from 299 to 120 Wh/Kg as measured from GCD analysis. These findings indicates that novel multinary nanocomposite holds potential as an electrode material in supercapacitors and as a sunlight-driven photocatalyst for the degradation of water-borne organic pollutants.

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.

Novel antibacterial low-shrinkage-stress resin-based cement

OBJECTIVE

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

CLINICAL SIGNIFICANCE

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

Effects of incorporation of nanoparticles into dental acrylic resins on antimicrobial and physico-mechanical properties: A meta-analysis of in vitro studies

Background

A meta-analysis study was conducted to determine whether the incorporation of nanoparticles into the dental acrylic resins influence the physico-mechanical properties and whether there are the appropriate nanoparticles exhibiting excellent antimicrobial activity against cariogenic bacteria along with acceptable physico-mechanical properties.

Methods

We systematically searched the various databases up to December 2021. The review was performed based on the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) and the Consolidated Standards of Reporting Trials (CONSORT) guidelines. A meta-analysis of physico-mechanical properties was performed by a random-effects model at a 95% confidence interval and the antimicrobial effects were analyzed descriptively.

Results

27 studies were included for the final analysis. There was no statistically significant difference in flexural strength (0.553, [95% confidence interval (CI) 0.501-0.604]), microhardness (0.509, [95% CI 0.278-0.736]), surface roughness (0.753, [95% CI 0.315-0.953]), impact strength (0.90, [95% CI 0.188-0.997]), and elastic modulus (0.848, [95% CI 0.514-0.967]), with nanoparticles addition compared with the control group. Forest plots were not generated for the thermal conductivity, tensile strength, and translucency because of the lack of comparison. Although the articles showed high heterogeneity without the high risk of bias, the finding showed the nanoparticles at low concentrations into dental acrylic resins could improve the antimicrobial activities without adverse effects on their physico-mechanical properties.

Conclusion

Adding the low concentration of nanoparticles such as 0.5% Ag, ≤0.25% TiO₂, and ≤0.25% SiO₂ as the most abundant antimicrobial nanoparticles do not influence their physico-mechanical properties and can be effective in the elimination of cariogenic pathogens.

Effects of the crosslinking of chitosan/DCPA particles in the antimicrobial and mechanical properties of dental restorative composites

The development of restorative materials containing antibacterial agents is an alternative to reduce the progression of caries lesions.

OBJECTIVE

to compare the influence of the degree of crosslinking of chitosan particles loaded with dibasic calcium phosphate (DCPA) on the mechanical properties, degree of conversion (DC), and antimicrobial properties of experimental composites.

METHODS

Chitosan/DCPA particles were synthesized by the electrospraying, crosslinked by 0, 8, or 16 h in glutaraldehyde, and characterized by zeta potential and minimum inhibitory concentration (MIC) against S. mutans. Experimental resin composites of Bis-GMA and TEGDMA and 59.5% of barium glass were synthesized, chitosan/DCPA particles were added at 0 or 0.5 wt% with the different crosslinking time. The materials were subject to DC analysis, three-point bending test at 24 h and 7 days, and antimicrobial assays. Data were submitted to one-way ANOVA and Tukey test (α = 0.05).

RESULTS

The particles with longer crosslinking time presented higher zeta potential and MIC, and the composite containing these particles showed significantly higher biofilm inhibition than the control group. The other two groups were similar to each other and the control. The composite containing particles with 88 h crosslinking time showed the lowest flexural strength at 7 days in water, and materials with non-crosslinked particles and longer crosslinking time presented flexural strength similar to control. The flexural modulus and DC showed no statistical difference among groups.

SIGNIFICANCE

composite resin containing 0.5% chitosan/DCPA particles crosslinked by 16 h showed a reduction of biofilm formation without affecting the mechanical properties in relation to the control.

Novel Giomers Incorporated with Antibacterial Quaternary Ammonium Monomers to Inhibit Secondary Caries

The objective of this study was to develop novel modified giomers by incorporating the antibacterial quaternary ammonium monomers (QAMs), dimethylaminododecyl methacrylate (DMADDM) or dimethylaminohexadecyl methacrylate (DMAHDM) into a commercial giomer. The material performances including mechanical properties, surface characteristics, color data, cytotoxicity and fluoride release of the novel giomers were evaluated. Antibacterial activity against severe early childhood caries (S-ECC) saliva-derived biofilms was assessed by lactic acid production measurement, MTT assay, biofilm staining and 16S rRNA sequencing. A rat model was developed and the anti-caries effect was investigated by micro-CT scanning and modified Keyes’ scoring. The results showed that the material properties of the QAMs groups were comparable to those of the control group. The novel giomers significantly inhibited lactic acid production and biofilm viability of S-ECC saliva-derived biofilms. Furthermore, caries-related genera such as Streptococcus and Lactobacillus reduced in QAMs groups, which showed their potential to change the microbial compositions. In the rat model, lesion depth, mineral loss and scoring of the QAMs groups were significantly reduced, without side effects on oral tissues. In conclusion, the novel giomers incorporated with antibacterial QAMs could inhibit the cariogenic biofilms and help prevent secondary caries, with great potential for future application in restorative treatment.

Graphene oxide and mineralized collagen-functionalized dental implant abutment with effective soft tissue seal and romotely repeatable photodisinfection

Grasping the boundary of antibacterial function may be better for the sealing of soft tissue around dental implant abutment. Inspired by ‘overdone is worse than undone’, we prepared a sandwich-structured dental implant coating on the percutaneous part using graphene oxide (GO) wrapped under mineralized collagen. Our unique coating structure ensured the high photothermal conversion capability and good photothermal stability of GO. The prepared coating not only achieved suitable inhibition on colonizing bacteria growth of Streptococcus sanguinis, Fusobacterium nucleatum and Porphyromonas gingivalis but also disrupted the wall/membrane permeability of free bacteria. Further enhancements on the antibacterial property were generally observed through the additional incorporation of dimethylaminododecyl methacrylate. Additionally, the coating with sandwich structure significantly enhanced the adhesion, cytoskeleton organization and proliferation of human gingival fibroblasts, which was effective to improve soft tissue sealing. Furthermore, cell viability was preserved when cells and bacteria were cultivated in the same environment by a coculture assay. This was attributed to the sandwich structure and mineralized collagen as the outmost layer, which would protect tissue cells from photothermal therapy and GO, as well as accelerate the recovery of cell activity. Overall, the coating design would provide a useful alternative method for dental implant abutment surface modification and functionalization.

Novel Rechargeable Nanostructured Calcium Phosphate Crown Cement with Long-Term Ion Release and Antibacterial Activity to Suppress Saliva Microcosm Biofilms

OBJECTIVE

Resin cements with remineralizing and antibacterial properties are favorable for inhibition of caries. The objectives of this study were: (1) to investigate the capability of the novel dimethylaminohexadecyl-methacrylate (DMAHDM) and nano-sized amorphous calcium phosphate (NACP) containing cement to reduce saliva microcosm biofilm, and (2) to investigate the long-term ion release, recharge, and re-release of DMAHDM-NACP cement.

METHODS

Pyromellitic glycerol dimethacrylate (PMGDM) and ethoxylated bisphenol-A-dimethacrylate (EBPADMA) were used to make PEHB monomer. Five cements were fabricated: (1) PEHB+0%NACP+0%DMAHDM (experimental control); (2) PEHB+25%NACP+0%DMAHDM, (3) PEHB+25%NACP+0%DMAHDM; (4) PEHB+25%NACP+3%DMAHDM; (5) PEHB+25%NACP+5%DMAHDM. RelyX luting cement was used as commercial control. Colony-forming units (CFU), lactic acid production, metabolic activities, and minimum inhibitory concentration (MIC) were performed. Long-term Calcium (Ca) and phosphate (P) ion release, recharge, and re-release were assessed.

RESULTS

Compared to experimental and commercial controls, the NACP-DMAHDM cement significantly reduced CFU biofilm by 2-3 orders of magnitude, metabolic activities from 0.24±0.06 A₅₄₀/cm² to 0.03±0.01 A₅₄₀/cm², and lactic acid production from 27.7±2.5 mmol/L to 5.4±2.1 mmol/L (n=6) (p<0.05). The DMAHDM showed an MIC value of 0.03 mg/L. However, when the DMAHDM was combined with PMGDM monomer, the MIC was greater than DMAHDM alone. The ion concentrations for the experimental groups significantly increased over time (1-84 days), indicating continuous ion release (n=3) (p<0.05). Increasing the DMAHDM mass fraction from 0% to 5% and 3% to 5% significantly enhanced ion recharge and re-release at the third cycle (p<0.05).

CONCLUSIONS

Incorporating DMAHDM and NACP into resin-based crown cement provides strong antibacterial action against saliva microcosm biofilm and presents a high level of Ca and P ion recharge abilities, exhibiting long-term Ca and P ion release and remineralization potential.

CLINICAL SIGNIFICANCE

Resin based cement containing NACP and DMAHDM were developed with remineralizing and potent antibacterial effects. This cement formulation showed ion release and remineralization potential and are promising formulations to inhibit the incidence of recurrent caries and could promote remineralization and be sustainable for the long term.

Exploring the use of a Ruthenium complex incorporated into a methacrylate-based dental material for antimicrobial photodynamic therapy

OBJECTIVES

To evaluate the effects of a blue light photosensitizer (PS), Ruthenium II complex (Ru), on the chemical, physical, mechanical, and antimicrobial properties of experimental dental resin blends.

METHODS

The experimental resin (BisEMA, TEEGDMA, HPMA, ethanol, and photoinitiator) was loaded with Ru at 0.00%, 0.07%, 0.14%, 0.28%, 0.56%, 1.12%, 1.2%, 1.5%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, or 10% w/w. Samples were evaluated for the degree of conversion (DC) after 30 and 60 s curing-time (n = 6). Selected formulations (0.00%, 0.28%, 0.56%, 1.12%) were further tested for shear bond strength (SBS) (n = 15); flexural strength (FS) (n = 12); and antimicrobial properties (CFUs), in dark and light conditions. These latter tests were performed on specimens stored for 24-h or 2-month in 37°C water. Water sorption (WS) and solubility (SL) tests were also performed (n = 12). Data were analyzed either by a one- or two-factor general linear model (α = 0.05).

RESULTS

Overall, Ru concentration above 1.2% resulted in reduced DC. In SBS results, only the 1.12%Ru resin blend samples had statistically lower values compared to the 0.00%Ru resin blend at 24-h storage (p = 0.004). In addition, no differences in SBS were detected among the experimental groups after 2-month storage in water. Meanwhile, FS increased for all experimental groups under similar aging conditions (p < 0.001). Antimicrobial properties were improved upon inclusion of Ru and application of light (p < 0.001 for both) at 24-h and 2-month storage. Lastly, no detectable changes in WS or SL were observed for the Ru-added resins compared to the 0.00%Ru resin blend. However, the 0.28% Ru blend presented significantly higher WS compared to the 0.56% Ru blend (p = 0.007).

CONCLUSIONS

Stable SBS, improved FS, and sustained antimicrobial properties after aging gives significant credence to our approach of adding the Ruthenium II complex into dental adhesive resin blends intended for an aPDT approach.

Construction and properties of the antibacterial epitaxial transition layer on a zirconia ceramic surface

Secondary caries is one of the main causes of dental zirconia restoration failure in the clinic. Therefore, it is urgent to improve the antibacterial performance of zirconia ceramics to reduce the occurrence of secondary caries. In this study, a quaternary ammonium compound antibacterial polymer was innovatively synthesized by solution polymerization with a quaternary ammonium salt monomer as the antibacterial component. The antibacterial epitaxial transition layer was successfully prepared on the surface of zirconia ceramics by the hydroxyl group on HEMA reacting with the siloxane group in the KH570 hydrolysate, which makes the antibacterial polymer indirectly chemically combine with the silicate epitaxial transition layer. The antibacterial epitaxial transition layer exhibited excellent mechanical properties, satisfactory biocompatibility and significant antibacterial effects, and the maximum antibacterial rate is 99%. The antibacterial epitaxial transition layer plays an important role in preventing secondary caries and improving the success rate of clinical zirconia ceramic restorations.

Construction of an antibacterial epitaxial transition layer on a zirconia ceramic surface to improve the antibacterial properties.

Mesoporous Calcium-Silicate Nanoparticles Loaded with Low-Dose Triton-100+Ag+ to Achieve Both Enhanced Antibacterial Properties and Low Cytotoxicity for Dentin Disinfection of Human Teeth

Mesoporous calcium-silicate nanoparticles (MCSNs) are excellent biomaterials for controlled drug delivery and mineralization induction. In this study, MCSNs were loaded with low-dose silver ion (Ag⁺) and Triton X-100 (TX-100) as the M-AgTX to achieve both enhanced antibacterial properties and low cytotoxicity for dentin disinfection. The physicochemical property, biocompatibility, infiltration ability into dentinal tubules, anti-bacterial ability against both planktonic Enterococcusfaecalis (E. faecalis) and its biofilm on dentin, effects on dentin microhardness and in vitro mineralization property were systematically investigated. Results confirmed that the MCSNs and M-AgTX nanoparticles showed typical morphology of mesoporous materials and exhibited sustained release of chemicals with an alkaline pH value over time. M-AgTX also exhibited excellent biocompatibility on MC3T3-E1 cells and could eliminate 100% planktonic E. faecalis after 48-h treatment. On dentin slices, it could enter dentinal tubules by ultrasonic activation and inhibit the growth of E. faecalis on dentin. M-AgTX could completely inactive 28-day E. faecalis biofilm. TEM confirmed the destruction of cell membrane integrity and Ag⁺ infiltration into bacteria by M-AgTX. Besides, dentin slices medicated with M-AgTX nanoparticles displayed an increased microhardness. After being immersed in SBF for 7 days, apatite crystals could be observed on the surface of the material tablets. M-AgTX could be developed into a new multifunctional intra-canal medication or bone defect filling material for infected bone defects due to its sustained release profile, low cytotoxicity, infiltration ability, enhanced anti-bacterial and mineralization features.

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.

Intelligent pH-responsive dental sealants to prevent long-term microleakage

OBJECTIVES

Microleakage is a determinant factor of failures in sealant application. In this study, DMAEM (dodecylmethylaminoethyl methacrylate), a pH-responsive antibacterial agent, was incorporated into resin-based sealant for the first time. The objectives of this study were to: (1) investigate the long-term performance of DMAEM-modified sealants against oral microbial-aging; and (2) investigate the long-term preventive effect of DMAEM-modified sealants on microleakage.

METHODS

Depth-of-cure and cytotoxicity of DMAEM-modified sealants were measured. Then, an aging model using biofilm derived from the saliva of high caries experience children was conducted. After aging, microhardness and surface roughness were measured. Biofilm activity, lactic acid production and exopolysaccharide (EPS) production were measured. 16S rRNA gene sequencing were also performed. The effects of DMAEM on microleakage were tested using an in vitro microleakage assessment.

RESULTS

The addition of DMAEM with a mass fraction of 2.5-10% did not affect depth-of-cure values and cytotoxicity of sealants. Adding 2.5-10% DMAEM did not affect the surface roughness and microhardness after aging. Compared to control, adding 2.5-10% DMAEM reduced biofilm metabolic activity by more than 80%. The lactic acid production and EPS production were reduced by 50% in DMAEM groups. DMAEM-modified sealants maintained the microbial diversity of biofilm after aging, they also inhibited the growth of lactobacillus. The 5% and 10% DMAEM groups exhibited a significant reduction in microleakage compared to control.

SIGNIFICANCE

The long-term antibacterial activities against oral microbial-aging and the long-term microecosystem-regulating capabilities enabled DMAEM-modified sealant to prevent microleakage in sealant application and thus prevent dental caries.

Immobilizing Bactericides on Dental Resins via Electron Beam Irradiation

Polymerizable bactericides, such as quaternary ammonium compound-based monomers, have been intensively studied as candidates for immobilizing antibacterial components on dental resin. However, they predominantly exhibit a bacteriostatic behavior, rather than bactericidal, as the immobilized components are left with insufficient molecular movement to disrupt the bacterial surface structure through contact-mediated action. In this study, we developed a novel strategy to increase the density of the immobilized bactericide and enhance its antibacterial/antibiofilm properties by combining a surface-grafting technique with electron beam irradiation. A solution of the quaternary ammonium compound-based monomer, 12-methacryloyloxydodecylpyridinium bromide (MDPB), was coated on polymethyl methacrylate (PMMA) resin specimens at the concentrations of 30, 50, and 80 wt%. The coated resins were subsequently exposed to 10 MeV of electron beam irradiation at 50 and 100 kGy, followed by thermal stabilization at 60 °C. The antibacterial effect was evaluated by inoculating a Streptococcus mutans suspension on the coated PMMA resin samples, which exhibited bactericidal effects even after 28 d of aging (P < 0.05, Tukey's honestly significant difference test). Transmission electron microscopy and bacteriolytic activity evaluation revealed that the S. mutans cells had sustained membrane depolarization. Furthermore, the antibiofilm effects against S. mutans and bacteria collected from human saliva were assessed. The thickness and the percentage of membrane-intact cells of the S. mutans and multispecies biofilms formed on the MDPB-immobilized surfaces were significantly lower than the uncoated PMMA specimens, even after 28-d aging (P < 0.05, Tukey's honestly significant difference test). Thus, the immobilization of antibacterial MDPB via electron beam irradiation induced rapid membrane depolarization, increasing membrane permeability and eventually causing cell death. Our strategy substantially enhances the antibacterial properties of the resinous materials and inhibits biofilm formation, therefore demonstrating significant potential for preventing infectious diseases in the oral environment.

Mesoporous Silica Particles as Drug Delivery Systems-The State of the Art in Loading Methods and the Recent Progress in Analytical Techniques for Monitoring These Processes

Conventional administration of drugs is limited by poor water solubility, low permeability, and mediocre targeting. Safe and effective delivery of drugs and therapeutic agents remains a challenge, especially for complex therapies, such as cancer treatment, pain management, heart failure medication, among several others. Thus, delivery systems designed to improve the pharmacokinetics of loaded molecules, and allowing controlled release and target specific delivery, have received considerable attention in recent years. The last two decades have seen a growing interest among scientists and the pharmaceutical industry in mesoporous silica nanoparticles (MSNs) as drug delivery systems (DDS). This interest is due to the unique physicochemical properties, including high loading capacity, excellent biocompatibility, and easy functionalization. In this review, we discuss the current state of the art related to the preparation of drug-loaded MSNs and their analysis, focusing on the newest advancements, and highlighting the advantages and disadvantages of different methods. Finally, we provide a concise outlook for the remaining challenges in the field.

Synthesis of Novel Dental Nanocomposite Resins by Incorporating Polymerizable, Quaternary Ammonium Silane-Modified Silica Nanoparticles

Diverse approaches dealing with the reinforcement of dental composite resins with quaternary ammonium compounds (QAC) have been previously reported. This work aims to investigate the physicochemical and mechanical performance of dental resins containing silica nanofillers with novel QAC. Different types of quaternary ammonium silane compounds (QASiC) were initially synthesized and characterized with proton nuclear magnetic resonance (¹H-NMR) and Fourier transform infrared (FTIR) spectroscopy. Silica nanoparticles were surface modified with the above QASiC and the structure of silanized products (S.QASiC) was confirmed by means of FTIR and thermogravimetric analysis. The obtained S.QASiC were then incorporated into methacrylate based dental resins. Scanning electron microscopy images revealed a satisfactory dispersion of silica nanoclusters for most of the synthesized nanocomposites. Curing kinetics disclosed a rise in both the autoacceleration effect and degree of conversion mainly induced by shorter QASiC molecules. Polymerization shrinkage was found to be influenced by the particular type of S.QASiC. The flexural modulus and strength of composites were increased by 74% and 19%, while their compressive strength enhancement reached up to 19% by adding 22 wt% S.QASiC nanoparticles. These findings might contribute to the proper design of multifunctional dental materials able to meet the contemporary challenges in clinical practice.

The Antibacterial and Remineralizing Effects of Biomaterials Combined with DMAHDM Nanocomposite: A Systematic Review

Researchers have developed novel nanocomposites that incorporate additional biomaterials with dimethylaminohexadecyl methacrylate (DMAHDM) in order to reduce secondary caries. The aim of this review was to summarize the current literature and assess the synergistic antibacterial and remineralizing effects that may contribute to the prevention of secondary caries. An electronic search was undertaken in MEDLINE using PubMed, Embase, Scopus, Web of Science and Cochrane databases. The initial search identified 954 papers. After the removal of duplicates and screening the titles and abstracts, 15 articles were eligible for this review. The amalgamation of 2-methacryloyloxyethyl phosphorylcholine (MPC) and silver nanoparticles (AgNPs) with DMAHDM resulted in increased antibacterial potency. The addition of nanoparticles of amorphous calcium phosphate (NACP) and polyamidoamine dendrimers (PAMAM) resulted in improved remineralization potential. Further clinical studies need to be planned to explore the antibacterial and remineralizing properties of these novel composites for clinical success.

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

OBJECTIVES

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

SIGNIFICANCE

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

Novel Crown Cement Containing Antibacterial Monomer and Calcium Phosphate Nanoparticles

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

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.

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.

Antimicrobial, biocompatibility, and physicochemical properties of novel adhesive methacrylate dental monomers

For the advancement of Class V restoratives, our goal was to evaluate the physicochemical and mechanical properties, antimicrobial functionality, and cytotoxic potential of novel antimicrobial copolymers. 5-Carboxy-N-(2-(methacryloyloxy)ethyl)-N,N-dimethylpentan-1-aminium bromide (AMadh1) and 10-carboxy-N-(2-(methacryloyloxy)ethyl)-N,N-dimethyldecan-1-aminium bromide (AMadh2) were incorporated into light-curable urethane dimethacrylate, polyethylene glycol–extended urethane dimethacrylate, ethyl 2-(hydroxymethyl) acrylate resin (UPE resin). In the AMadhs-UPE resin, the hydrophobic/hydrophilic balance, degree of vinyl conversion, flexural strength, elastic modulus, and shear bond strength were assessed. Antimicrobial properties were measured using Streptococcus mutans (planktonic and biofilm). Cytotoxicity was tested using human gingival fibroblasts and mouse connective tissue fibroblasts (ATCC® CCL-1™) exposed to two-fold serial dilutions (≤10.6 mmol/L AMadh1 or ≤8.8 mmol/L AMadh2). At 10% mass of AMadh, the attained degree of vinyl conversion values (AMadh1 = 90.1% and AMadh2 = 88.5%) were not statistically different from the UPE resin (88.1%). At both AMadh levels, the flexural strength was reduced in a dose-dependent manner. Elastic modulus and contact angle were not significantly affected by AMadh1. Variations in elastic modulus and contact angle were observed with AMadh2; however, this does not disqualify it in future design of Class V restoratives. Compared to UPE resin, AMadh1-UPE and AMadh2-UPE (10% mass) copolymers reduced S. mutans biofilm 4.2- and 1.6-fold, respectively (p ≤ 0.006). In direct contact with human gingival fibroblasts or ATCC CCL-1 cells, at biologically relevant concentrations, the AMadhs did not adversely affect cell viability or their metabolic activity. This effort addresses a significant oral health issue associated with elderly populations. Its successful completion is expected to yield dental restoratives with well-controlled biofunction.

Novel antibacterial calcium phosphate nanocomposite with long-term ion recharge and re-release to inhibit caries

Short-term studies on calcium-phosphate (CaP) ion-rechargeable composites were reported. The long-term rechargeability is important but unknown. The objectives of this study were to investigate nanocomposite with strong antibacterial and ion-recharge capabilities containing dimethylaminododecyl methacrylate (DMAHDM) and nanoparticles of amorphous calcium phosphate (NACP), and evaluate long-term ion-recharge by testing for 12 cycles (taking 6 months to complete) for the first time. Three groups were tested: (1) Heliomolar control; (2) Resin+20%NACP+50%glass; (3) Resin+3%DMAHDM+20%NACP+50%glass. Biofilm acid and colony-forming units (CFU) were measured. Ion-recharge was tested for 12 cycles. NACP-DMAHDM composite reduced biofilm acid, and reduced CFU by 4 logs. High levels of ion releases were maintained throughout 12 cycles of recharge, maintaining steady-state releases without reduction in 6 months (p>0.1), representing long-term remineralization potential. Bioactive nanocomposite demonstrated long-term ion-rechargeability for the first time, showed remineralization and potent anti-biofilm functions, with promise for tooth restorations to combat caries.

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

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

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

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

Effect of Novel Micro-Arc Oxidation Implant Material on Preventing Peri-Implantitis

Dental implants occasionally fail for many reasons, especially peri-implantitis. The adhesion of bacteria to the surface of titanium is the initial factor in peri-implantitis. Therefore, the aim of this study was to assess the effect of a novel micro-arc oxidation (MAO) titanium on bacteria inhibition and regulation through periodontitis, and on a healthy saliva-derived biofilm, in vitro. MAO, sandblasting and acid etching (SLA), machined titanium and plasma-sprayed hydroxyapatite (HA) were selected for further study. The metabolic activity and biomass accumulation were tested using MTT (3-(4,5-Dimethyl-thiazol-2-yl)-2,5-diphenyltetrazolium bromide) and crystal violet assay after 24 h of anaerobic incubation. The structure was determined by scanning electron microscopy (SEM) and live/dead staining. Moreover, 16S rDNA sequencing was used to assess the microbial community. The results showed that biofilms on MAO were thinner compared to HA and SLA. In the periodontitis group, the biofilm accumulation and metabolic activity reached the highest levels in the HA group (p < 0.05); MAO titanium had the smallest biofilm accumulation and higher live/dead ratio; and the relative abundance of Lactobacillus in the SLA, HA and MAO groups increased significantly compared to the machined group (p < 0.05). In the healthy group, the relative abundance of Lactobacillus in the MAO group increased significantly compared to the other three groups (p < 0.05); the amount and metabolism activity of bacteria in the MAO group was lower (p < 0.05); MAO titanium had the least biofilm accumulation and a higher live/dead ratio. In conclusion, the novel MAO titanium had the ability to combat peri-implantitis by inhibiting the biofilm and regulating the microbial ecosystem to healthier conditions.

Immobilization of quaternary ammonium based antibacterial monomer onto dentin substrate by non-thermal atmospheric plasma

Use of non-thermal atmospheric plasma (NTAP) brush on immobilization of dimethylaminohexadecyl methacrylate (DMAHDM) onto dentin bonding substrate, and resulting antibacterial activity against Streptococcus mutans were investigated. A bonding substrate with several-micron-demineralized layer was created from human dentin. DMAHDM was applied onto the demineralized layer with or without plasma exposure. Scanning electron microscopy (SEM) and Fourier transformed infrared (FTIR) spectroscopy were employed to verify immobilization/grafting of DMAHDM onto the substrate. Antibacterial activity of the resulting substrate was assessed by using colony-forming unit (CFU) and confocal scanning laser microscopy. Effects of saliva pellicle treatment and aging process on the above substrate were also evaluated. The SEM/FTIR results demonstrated that NTAP could induce DMAHDM immobilization onto dentin substrate, which was further verified via quantitative FTIR analysis. Comparing with non-plasma-treated, the plasmatreated substrate, with CFU 4 log lower, exhibited much stronger inhibitory effects, which were minimally affected by saliva or aging. The DMAHDM-immobilized dentin substrate showed effective and sustained antibacterial characteristics.

A novel antibacterial resin-based root canal sealer modified by Dimethylaminododecyl Methacrylate

Persistent apical periodontitis, mainly caused by microorganisms infections, represents a critical challenge for endodontists. Dimethylaminododecyl methacrylate (DMADDM) is a well-studied and potent antibacterial agent used in various studies described in the literature. The aim of this study is to develop a novel antibacterial root canal sealer by incorporating DMADDM into EndoREZ and investigate the properties of the resulting material. Different mass fractions (0, 1.25%, 2.5%, and 5%) of DMADDM were incorporated into EndoREZ and the cytotoxicity, apical sealing ability and solubility of the resulting material were evaluated. Furthermore, a direct contact test, determination of colony-forming units, a crystal violet assay, scanning electronic microscopy and live/dead bacteria staining were performed to evaluate the antibacterial effect of the sealer to multispecies bacteria (Enterococcus faecalis, Streptococcus gordonii, Actinomyces naeslundii, and Lactobacillus acidophilus), in planktonic cells or biofilms. Fluorescence in situ hybridization and quantitative real-time polymerase chain reaction were carried out to assess the composition of the multispecies biofilms. No difference on the cytotoxicity, apical sealing ability and solubility between sealers containing DMADDM (1.25%, 2.5%) and EndoREZ (0%) could be determined. However, when the mass fraction of DMADDM increased to 5%, significantly different properties were found compared to the 0% (p < 0.05) group. Moreover, incorporating DMADDM into the sealer could greatly improve the antibacterial properties of EndoREZ. In addition, the composition ratio of E. faecalis could be decreased in multispecies microecology in sealers containing DMADDM. Therefore, a EndoREZ sealer material containing DMADDM could be considered useful in clinical applications for preventing and treating persistent apical periodontitis.

Effect of D-cysteine on dual-species biofilms of Streptococcus mutans and Streptococcus sanguinis

Dental caries is a highly prevalent disease worldwide. It is caused by the cariogenic biofilms composed of multiple dynamic bacteria on dental surface. Streptococcus mutans and Streptococcus sanguinis are resident members within the biofilms and an antagonistic relationship has been shown between these two species. S. mutans, as the major causative microorganism of dental caries, has been reported to be inhibited by free D-cysteine (D-Cys). However, whether D-Cys could affect S. sanguinis and the interspecies relationship between S. mutans and S. sanguinis remains unknown. The aim of the current study was to investigate the effect of D-Cys on the growth and cariogenicity of dual-species biofilms formed by S. mutans and S. sanguinis. We measured dual-species biofilms biomass, metabolic activity, lactate production. We also detected the biofilms structure, the ratio of live/dead bacteria, extracellular polysaccharide (EPS) synthesis and bacterial composition in the dual-species biofilms. We found that D-Cys could reduce the metabolic activity and lactic acid production of dual-species biofilms (p < 0.05). In addition, biofilms formation, the proportion of S. mutans in dual-species biofilms, and EPS synthesis were decreased with D-Cys treatment. The results suggested that D-Cys could inhibit the growth and cariogenic virulence of dual-species biofilms formed by S. mutans and S. sanguinis, indicating the potential of D-Cys in clinical application for caries prevention and treatment.

Novel dental composite with capability to suppress cariogenic species and promote non-cariogenic species in oral biofilms

Recurrent caries often occurs and is a primary reason for the failure of dental composite restorations. The objectives of this study were to: (1) develop a bioactive composite containing dimethylaminohexadecyl methacrylate (DMAHDM), (2) investigate its antibacterial effects and suppression on biofilm growth, and (3) investigate its ability to modulate biofilm species composition for the first time. DMAHDM was incorporated into a composite at mass% of 0%, 0.75%, 1.5%, 2.25% and 3%. A commercial composite Heliomolar served as a comparative control. A biofilm model consisting of Streptococcus mutans (S. mutans), Streptococcus sanguinis (S. sanguinis) and Streptococcus gordonii (S. gordonii) was tested by growing biofilms for 48 h and 72 h on composites. Colony-forming units (CFUs), metabolic activity and live/dead staining were evaluated. Lactic acid and polysaccharide productions were measured to assess biofilm cariogenicity. TaqMan real-time polymerase chain reaction was used to determine the proportion of each species in the biofilm. DMAHDM-containing composite had a strong anti-biofilm function, reducing biofilm CFU by 2-3 orders of magnitude, compared to control composite. Biofilm metabolic activity, lactic acid and polysaccharides were decreased substantially, compared to control (p < 0.05). At 72 h, the cariogenic S. mutans proportion in the biofilm on the composite with 3% DMAHDM was 19.9%. In contrast, an overwhelming S. mutans proportion of 92.2% and 91.2% existed in biofilms on commercial control and 0% DMAHDM, respectively. In conclusion, incorporating DMAHDM into dental composite: (1) yielded potent anti-biofilm properties; (2) modulated the biofilm species composition toward a non-cariogenic tendency. The new DMAHDM composite is promising for applications in a wide range of tooth cavity restorations to modulate oral biofilm species and combat caries.

Novel Approaches to the Control of Oral Microbial Biofilms

Effective management of biofilm-related oral infectious diseases is a global challenge. Oral biofilm presents increased resistance to antimicrobial agents and elevated virulence compared with planktonic bacteria. Antimicrobial agents, such as chlorhexidine, have proven effective in the disruption/inhibition of oral biofilm. However, the challenge of precisely and continuously eliminating the specific pathogens without disturbing the microbial ecology still exists, which is a major factor in determining the virulence of a multispecies microbial consortium and the consequent development of oral infectious diseases. Therefore, several novel approaches are being developed to inhibit biofilm virulence without necessarily inducing microbial dysbiosis of the oral cavity. Nanoparticles, such as pH-responsive enzyme-mimic nanoparticles, have been developed to specifically target the acidic niches within the oral biofilm where tooth demineralization readily occurs, in effect controlling dental caries. Quaternary ammonium salts (QAS) such as dimethylaminododecyl methacrylate (DMADDM), when incorporated into dental adhesives or resin composite, have also shown excellent and durable antimicrobial activity and thus could effectively inhibit the occurrence of secondary caries. In addition, custom-designed small molecules, natural products and their derivatives, as well as basic amino acids such as arginine, have demonstrated ecological effects by modulating the virulence of the oral biofilm without universally killing the commensal bacteria, indicating a promising approach to the management of oral infectious diseases such as dental caries and periodontal diseases. This article aims to introduce these novel approaches that have shown potential in the control of oral biofilm. These methods may be utilized in the near future to effectively promote the clinical management of oral infectious diseases and thus benefit oral health.

A review of bioceramics-based dental restorative materials

Currently, much has been published related to conventional resin-based composites and adhesives; however, little information is available about bioceramics-based restorative materials. The aim was to structure this topic into its component parts and to highlight the translational research that has been conducted up to the present time. A literature search was done from indexed journals up to September 2017. The main search terms used were based on dental resin-based composites, dental adhesives along with bioactive glass and the calcium phosphate family. The results showed that in 123 articles, amorphous calcium phosphate (39.83%), hydroxyapatite (23.5%), bioactive glass (16.2%), dicalcium phosphate (5.69%), monocalcium phosphate monohydrate (3.25%), and tricalcium phosphate (2.43%) have been used in restorative materials. Moreover, seven studies were found related to a newly developed commercial bioactive composite. The utilization of bioactive materials for tooth restorations can promote remineralization and a durable seal of the tooth-material interface.

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.