Dimethylaminohexadecyl Methacrylate Research Articles

Novel orthodontic adhesives with antibacterial, mineralization and fluorescence properties for enamel demineralization prevention

Enamel demineralization is one of the most common adverse effects of fixed orthodontic treatment, mainly because the appliances affect oral hygiene maintenance, potentially leading to plaque accumulation and oral flora dysbiosis. Adhesives are essential for fixed orthodontic treatment, but excessive adhesives on tooth surfaces might be stained aesthetically and serve as additional sites for plaque accumulation. Some research gaps exist for simultaneously addressing orthodontic enamel demineralization and proper adhesive removal. In this study, novel multifunctional orthodontic adhesives (MFOAs) were developed using amino-silane functionalized zinc oxide quantum dots (AF-ZnOQDS) with fluorescence property, antibacterial agent dimethylaminohexadecyl methacrylate (DMAHDM), and mineralizing material 45S5 bioactive glass (BG-45S5) as the modifiers. The three were incorporated into Transbond XT adhesive at different mass fractions and relevant properties were evaluated in vitro and in vivo. The results indicated that the MFOA-3 with 3 wt% AF-ZnOQDS, 5 wt% DMAHDM, and 7.5 wt% BG-45S5 possessed long-term antibacterial ability, dual-mineralization activity, and strong fluorescence properties. It had clinically acceptable physicochemical properties and good biocompatibility, providing a desirable anti-demineralization effect. Therefore, MFOA-3 provides a new strategy to solve the two major challenges of enamel demineralization and proper removal of adhesives during fixed orthodontics, and thus has great value in clinical application.

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.

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

S. mutans Antisense vicK RNA Over-Expression Plus Antibacterial Dimethylaminohexadecyl Methacrylate Suppresses Oral Biofilms and Protects Enamel Hardness in Extracted Human Teeth.

Streptococcus mutans (S. mutans) antisense vicK RNA (ASvicK) is a non-coding RNA that regulates cariogenic virulence and metabolic activity. Dimethylaminohexadecyl methacrylate (DMAHDM), a quaternary ammonium methacrylate used in dental materials, has strong antibacterial activity. This study examined the effects of S. mutans ASvicK on DMAHDM susceptibility and their combined impact on inhibiting S. mutans biofilm formation and protecting enamel hardness. The parent S. mutans UA159 and ASvicK overexpressing S. mutans (ASvicK) were tested. The minimum inhibitory concentration (MIC) and minimum bactericidal concentrations for planktonic bacteria (MBC-P) and biofilms (MBC-B) were measured. As the ASvicK MBC-B was 175 μg/mL, live/dead staining, metabolic activity (MTT), colony-forming units (CFUs), biofilm biomass, polysaccharide, and lactic acid production were investigated at 175 μg/mL and 87.5 μg/mL. The MIC, MBC-P, and MBC-B values for DMAHDM for the ASvicK strain were half those of the UA159 strain. In addition, combining S. mutans ASvicK with DMAHDM resulted in a significant 4-log CFU reduction (p < 0.05), with notable decreases in polysaccharide levels and lactic acid production. In the in vitro cariogenic model, the combination achieved the highest enamel hardness at 67.1% of sound enamel, while UA159 without DMAHDM had the lowest at 16.4% (p < 0.05). Thus, S. mutans ASvicK enhanced DMAHDM susceptibility, and their combination effectively inhibited biofilm formation and minimized enamel demineralization. The S. mutans ASvicK + DMAHDM combination shows great potential for anti-caries dental applications.

New Generation of Orthodontic Elastomeric Ligature to Prevent Enamel Demineralization In Vivo.

This study aimed to synthesize a novel elastomeric ligature with dimethylaminohexadecyl methacrylate (DMAHDM) grafted, providing a new strategy for improving the issue of enamel demineralization during fixed orthodontics. DMAHDM was incorporated into elastomeric ligatures at different mass fractions using ultraviolet photochemical grafting. The antibacterial properties were evaluated and the optimal DMAHDM amount was determined based on cytotoxicity assays. Moreover, tests were conducted to evaluate the in vivo changes in the mechanical properties of the elastomeric ligatures. To assess the actual in vivo effectiveness in preventing enamel demineralization, a rat demineralization model was established, with analyses focusing on changes in surface microstructure, elemental composition, and nanomechanical properties. Elastomeric ligatures with 2% DMAHDM showed excellent biocompatibility and the best antibacterial properties, reducing lactic acid production by 65.3% and biofilm bacteria by 50.0% within 24 h, without significant mechanical property differences from the control group (p > 0.05). Most importantly, they effectively prevented enamel demineralization in vivo, enhancing elastic modulus by 73.2% and hardness by 204.8%. Elastomeric ligatures incorporating DMAHDM have shown great potential for application in preventing enamel demineralization, providing a new strategy to solve this issue during fixed orthodontics.

Novel antibacterial orthodontic elastomeric ligature with oral biofilm-regulatory ability to prevent enamel demineralization

ObjectivesTo synthesize a novel antibacterial orthodontic elastomeric ligature incorporating dimethylaminohexadecyl methacrylate (DMAHDM) for the first time to prevent enamel demineralization during orthodontic therapy. MethodsVarious mass fractions of DMAHDM (ranging from 0 % to 20 %) were grafted onto commercial elastomeric ligatures using an ultraviolet photochemical grafting method and were characterized. The optimal DMAHDM concentration was determined based on biocompatibility and mechanical properties, and the antibacterial efficacy was evaluated in a whole-plaque biofilm model. TaqMan real-time polymerase chain reaction and fluorescence in situ hybridization were used to assess the microbial regulatory ability of the multispecies biofilms. Furthermore, an in vitro tooth demineralization model was established to explore its preventive effects on enamel demineralization. Statistical analysis involved a one-way analysis of variance and LSD post hoc tests at a significance level of 0.05. ResultsThe elastomeric ligature containing 2 % mass fraction of DMAHDM exhibited excellent mechanical properties, favorable biocompatibility, and the most effective antibacterial ability against microorganisms, which decreased by almost two logarithms (P < 0.05). It significantly reduced the proportion of Streptococcus mutans in the multispecies plaque biofilm by 25 % at 72 h, leading to an enhanced biofilm microenvironment. Moreover, the novel elastomeric ligature demonstrated an obvious preventive effect on enamel demineralization, with an elastic modulus 30 % higher and hardness 62 % higher than those of the control group within 3 months (P < 0.05). SignificanceThe integration of DMAHDM with an elastomeric ligature holds significant promise for regulating biofilms and preventing enamel demineralization in orthodontic applications.

Novel strategy of S. mutans gcrR gene over-expression plus antibacterial dimethylaminohexadecyl methacrylate suppresses biofilm acids and reduces dental caries in rats

ObjectiveStreptococcus mutans (S. mutans) is a major contributor to dental caries, with its ability to synthesize extracellular polysaccharides (EPS) and biofilms. The gcrR gene is a regulator of EPS synthesis and biofilm formation. The objectives of this study were to investigate a novel strategy of combining gcrR gene over-expression with dimethylaminohexadecyl methacrylate (DMAHDM), and to determine their in vivo efficacy in reducing caries in rats for the first time. MethodsTwo types of S. mutans were tested: Parent S. mutans; and gcrR gene over-expressed S. mutans (gcrR OE S. mutans). Bacterial minimum inhibitory concentration (MIC) and minimal bactericidal concentration (MBC) were measured with DMAHDM and chlorhexidine (CHX). Biofilm biomass, polysaccharide, lactic acid production, live/dead staining, colony-forming units (CFUs), and metabolic activity (MTT) were evaluated. A Sprague-Dawley rat model was used with parent S. mutans and gcrR OE S. mutans colonization to determine caries-inhibition in vivo. ResultsDrug-susceptibility of gcrR OE S. mutans to DMAHDM or CHX was 2-fold higher than that of parent S. mutans. DMAHDM reduced biofilm CFU by 3–4 logs. Importantly, the combined gcrR OE S. mutans+ DMAHDM dual strategy reduced biofilm CFU by 5 logs. In the rat model, the parent S. mutans group had a higher cariogenicity in dentinal (Dm) and extensive dentinal (Dx) regions. The DMAHDM + gcrR OE group reduced the Dm and Dx caries to only 20 % and 0 %, those of parent S. mutans + PBS control group (p < 0.05). The total caries severity of gcrR OE + DMAHDM group was decreased to 51 % that of parent S. mutans control (p < 0.05). SignificanceThe strategy of combining S. mutans gcrR over-expression with antibacterial monomer reducing biofilm acids by 97 %, and reduced in vivo total caries in rats by 48 %. The gcrR over-expression + DMAHDM strategy is promising for a wide range of dental applications to inhibit caries and protect tooth structures.

Novel Resin-Based Antibacterial Root Surface Coating Material to Combat Dental Caries.

Root caries caused by cariogenic bacteria are a burden on a large number of individuals worldwide, especially the elderly. Applying a protective coating to exposed root surfaces has the potential to inhibit the development of caries, thus preserving natural teeth. This study aimed to develop a novel antibacterial coating to combat root caries and evaluate its effectiveness using the antibacterial monomer dimethylaminohexadecyl methacrylate (DMAHDM). DMAHDM was synthesized and incorporated into a resin consisting of 55.8% urethane dimethacrylate (UDMA) and 44.2% TEG-DVBE (UV) at a 10% mass fraction of glass filler. Multiple concentrations of DMAHDM were tested for their impact on the resin's mechanical and physical properties. S. mutans biofilms grown on resin disks were analyzed for antibacterial efficacy. Cytotoxicity was assessed against human gingival fibroblasts (HGFs). The results showed an 8-log reduction in colony-forming units (CFUs) against S. mutans biofilm (mean ± sd; n = 6) (p < 0.05) when 5% DMAHDM was incorporated into the UV resin. There was a 90% reduction in metabolic activity and lactic acid production. A low level of cytotoxicity against HGF was observed without compromising the physical and mechanical properties of the resin. This coating material demonstrated promising physical properties, potent antibacterial effects, and low toxicity, suggesting its potential to protect exposed roots from caries in various dental procedures and among elderly individuals with gingival recession.

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.

Novel pit and fissure sealant with nano-CaF2 and antibacterial monomer: Fluoride recharge, microleakage, sealing ability and cytotoxicity.

Conventional resin-based sealants release minimal fluoride ions (F) and lack antibacterial activity. The objectives of this study were to: (1) develop a novel bioactive sealant containing calcium fluoride nanoparticles (nCaF2) and antibacterial dimethylaminohexadecyl methacrylate (DMAHDM), and (2) investigate mechanical performance, F recharge and re-release, microleakage, sealing ability and cytotoxicity. Helioseal F served as commercial control. The initial F release from sealant containing 20% nCaF2 was 25-fold that of Helioseal F. After ion exhaustion and recharge, the F re-release from bioactive sealant did not decrease with increasing number of recharge and re-release cycles. Elastic modulus of new bioactive sealant was 44% higher than Helioseal F. The new sealant had excellent sealing, minimal microleakage, and good cytocompatibility. Hence, the nanostructured sealant had substantial and sustained F release and antibacterial activity, good sealing ability and biocompatibility. The novel bioactive nCaF2 sealant is promising to provide long-term F ions for caries prevention.

Novel antibacterial titanium implant healing abutment with dimethylaminohexadecyl methacrylate to combat implant-related infections

ObjectiveImplant-related infections from the adhesion and proliferation of dental plaque are a major challenge for dental implants. The objectives of this study were to: (1) develop novel antibacterial titanium (Ti) healing abutment; (2) investigate the inhibition of implant infection-related pathogenic bacteria and saliva-derived biofilm, and evaluate the biocompatibility of the new material for the first time. MethodsDimethylaminohexadecyl methacrylate (DMAHDM) and hydroxyapatite (HAP) were polymerized via polydopamine (PDA) on Ti. Staphylococcus aureus (S. aureus), Streptococcus sanguinis (S. sanguinis) and human saliva-derived biofilms were tested. After 4 weeks of DMAHDM release, the antibacterial efficacy of the DMAHDM remaining on Ti surface and the DMADHM in medium was tested. Biocompatibility was determined using human gingival fibroblasts (HGFs) and periodontal ligament stem cells (PDLSCs). ResultsThe DMAHDM-loaded coating filled into the nano-voids in Ti surfaces. The modified Ti showed potent antibacterial activity, reducing the CFU of S. aureus, S. sanguinis and saliva-derived biofilms by 8, 7 and 4 log, respectively (P < 0.05). After 4 weeks of release, the modified Ti was still able to reduce S. aureus and S. sanguinis biofilm CFU by 1–3 log (P < 0.05). This provided strong antibacterial function for more than 4 weeks, which were the high-risk period for implant infections. The new material showed excellent biocompatibility when compared to control (P > 0.05). ConclusionNovel DMAHDM-loaded Ti healing abutment had strong antibacterial effects, reducing biofilm CFUs by orders of magnitude, and lasting for over four weeks to cover the high-risk period for implant infections. The novel antibacterial Ti is promising to combat implant-related infections in dental, craniofacial and orthopedic applications.

Testing mechanical properties and degree of conversion of resin-based composite material containing contact killing antibacterial agent in comparison with fluoride composite resin

BackgroundA major drawback of resin composites is their tendency to accumulate microbial biofilms that can lead to secondary caries. The objective of this study was to compare the mechanical properties and the degree of conversion of commercial resin-based composite materials containing a contact-killing antibacterial agent, dimethylaminohexadecyl methacrylate (DMAHDM), at different concentrations, with a fluoride-releasing composite material. Materials and methodsFour groups were tested: Tetric N Ceram composite material (G1), Tetric Evo Ceram (G2), and Tetric N Ceram with the addition of contact-killing antibacterial agent DMAHDM at concentrations of 3% (G3) and 5% (G4). The mechanical properties, including flexural strength, elastic modulus, and Vickers microhardness and the degree of conversion were investigated. ResultsAdding 3 % and 5 % DMAHDM resulted in flexural strength values that were comparable to Tetric Evo Ceram. Tetric N Ceram was comparable to the group containing 3 % DMAHDM (p > 0.05). However, it was significantly greater when compared to Tetric Evo Ceram (93.3 ± 9.4) and 5 % DMAHDM (p < 0.05). Both the elastic modulus and Vickers microhardness values of Tetric N Ceram were significantly higher than those of the other groups (p < 0.05). Furthermore, the elastic modulus of Tetric Evo Ceram showed similar results to groups with 3 % and 5 % DMAHDM. Nevertheless, the Vickers microhardness value is significantly higher when compared to 5 % DMAHDM (0.394 ± 0.021) (p < 0.05) while it was comparable to that of 3 % DMAHDM (0.484 ± 0.016) (p > 0.05). There was no statistically significant difference in the degree of conversion between the groups (p > 0.05). ConclusionAdding 3% DMAHDM to Tetric N Ceram resulted in flexural strength values that were similar to those of Tetric N Ceram and Tetric Evo Ceram. DMAHDM did not affect the degree of conversion of Tetric N Ceram composite.

Evaluation of the effects of combined application of dimethylaminohexadecyl methacrylate and MDP on dentin bonding and antimicrobial properties

Evaluation of the effects of combined application of dimethylaminohexadecyl methacrylate and MDP on dentin bonding and antimicrobial properties

Dual function of anti-biofilm and modulating biofilm equilibrium of orthodontic cement containing quaternary ammonium salt.

The objectives of this study were to incorporate dimethylaminohexadecyl methacrylate (DMAHDM) into resin-modified glass ionomer cement (RMGI) to develop a novel orthodontic cement which endowed RMGI with strong antibacterial ability and investigated its modulation biofilm equilibrium from cariogenic state to non-cariogenic state for the first time. Cariogenic Streptococcus mutans (S. mutans), and non-cariogenic Streptococcus sanguinis (S. sanguinis) and Streptococcus gordonii (S. gordonii) were selected to form a tri-species biofilm model. RMGI incorporated with different mass fraction of DMAHDM was examined: biofilm colony-forming units, metabolic activity, live/dead staining, lactic acid and exopolysaccharides productions. TaqMan real-time polymerase chain reaction was used to determine changes of biofilm species compositions. The results showed RMGI containing 3% DMAHDM achieved strong antibacterial ability and suppressed the cariogenic species in biofilm, modulating biofilm equilibrium from cariogenic state to non-cariogenic state tendency. The novel bioactive cement containing DMAHDM is promising in fixed orthodontic treatments and protecting tooth enamel.

Mussel-inspired self-assembly platform for staged implant osseointegration: Combining early anti-infection and late osteoinduction

Current implant systems still lack the ability to combat implant-associated infections (IAI) and insufficient osseointegration to reduce the risk of implant failure. There’s an urgent need to develop an effective implant modification method to match the needs of different biological stages post-implantation, which requires anti-infection at the initial stage and osseointegration at the latter long-term stage. Here, we constructed a mussel-inspired layer-by-layer (LbL) self-assembly implant modification platform via tannic acid (TA), sequentially anchoring osteoanabolic drug (Abaloparatide, ABL) and antibacterial (Dimethylaminohexadecyl methacrylate, DMAHDM) to the Titanium (Ti) surface (Ti/ABL/DMAHDM). The Ti/ABL/DMAHDM exhibited outstanding antibacterial properties at the initial stage with an antibacterial rate of 100 % both in vitro (24 h) and in vivo (48 h). Moreover, it showed significant osteogenic induction ability at the latter long-term stage both in vitro (7 days and 14 days) and in vivo (4 weeks), accompanied by good biocompatibility. This TA-mediated self-assembly modification implants platform with staged regulation of anti-infection and osteoinduction offers potential clinical prospects for improving osseointegration after implantation.

Influence of resin modified glass ionomer cement incorporating protein-repellent and antimicrobial agents on supragingival microbiome around brackets: an in-vivo split-mouth 3-month study.

To explore the influence of resin modified glass ionomer cement (RMGIC) adhesives containing protein-repellent and quaternary ammonium salt agents on supragingival microbiome, enamel and gingival health around brackets. Ten patients (21.4 ±3.5 years) about to receive fixed orthodontics were enrolled in this study. Unilateral upper teeth bonded with RMGIC incorporating 2-Methacryloyloxyethyl phosphorylcholine (MPC) and Dimethylaminohexadecyl methacrylate (DMAHDM) were regarded as experimental group (RMD), while contralateral upper teeth bonded with RMGIC were control group (RMGIC), using a split-mouth design. Supragingival plaque was collected from both groups before treatment (T0), and at 1 month (T1) and 3 months (T2) of treatment. High-throughput sequencing was performed targeting v3-v4 of 16S rRNA gene. Streptococcus mutans and Fusobacterium nucleatum quantification was done by qPCR analysis. Bracket failures, enamel decalcification index (EDI), DIAGNODent scores (Dd), plaque index (PI) and gingival index (GI) were monitored at indicated time points. Within 3 months, alpha and beta diversity of supragingival plaque had no difference between RMGIC and RMD groups. From T0 to T2, the relative abundance of Streptococcus depleted in RMD but remained steady in RMGIC group. Streptococcus, Prevotella, and Fusobacterium became depleted in RMD, Haemophilus and Capnocytophaga became depleted in RMGIC group but Prevotella enriched. Quantification of Fusbacterium nucleatum and Streptococcus mutans showed significant difference between RMGIC and RMD groups at T2. Teeth bonded with RMD had significant lower plaque index (PI) and DIAGNODent (Dd) score at T2, compared with teeth bonded with RMGIC (p < 0.05). No difference in bracket failure rate was examined between both groups (p > 0.05). By incorporating MPC and DMAHDM into RMGIC, the material could affect the supragingival microbial composition, inhibit the progress of plaque accumulation as well as the key pathogens S. mutans and F. nucleatum in the early stage of orthodontic treatment.

Novel protein-repellent and antibacterial polymethyl methacrylate dental resin in water-aging for 6 months

BackgroundThe present study aimed to develop a novel protein-repellent and antibacterial polymethyl methacrylate (PMMA) dental resin with 2-methacryloyloxyethyl phosphorylcholine (MPC) and quaternary ammonium dimethylaminohexadecyl methacrylate (DMAHDM), and to investigate the effects of water-aging for 6 months on the mechanical properties, protein adsorption, and antibacterial activity of the dental resin.MethodsFour groups were tested: PMMA control; PMMA + 3% MPC; PMMA + 1.5% DMAHDM; and PMMA + 3% MPC + 1.5% DMADDM in acrylic resin powder. Specimens were water-aged for 1 d, 3 months, and 6 months at 37 ℃. Their mechanical properties were then measured using a three-point flexure test. Protein adsorption was measured using a micro bicinchoninic acid (BCA) method. A human saliva microcosm model was used to inoculate bacteria on water-aged specimens and to investigate the live/dead staining, metabolic activity of biofilms, and colony-forming units (CFUs).ResultsThe flexural strength and elastic modulus showed a significant loss after 6 months of water-ageing for the PMMA control (mean ± SD; n = 10); in contrast, the new protein repellent and antibacterial PMMA resin showed no strength loss. The PMMA–MPC–DMAHDM-containing resin imparted a strong antibacterial effect by greatly reducing biofilm viability and metabolic activity. The biofilm CFU count was reduced by about two orders of magnitude (p < 0.05) compared with that of the PMMA resin control. The protein adsorption was 20% that of a commercial composite (p < 0.05). Furthermore, the PMMA–MPC–DMAHDM-containing resin exhibited a long-term antibacterial performance, with no significant difference between 1 d, 3 months and 6 months (p > 0.05).ConclusionsThe flexural strength and elastic modulus of the PMMA–MPC–DMAHDM-containing resin were superior to those of the PMMA control after 6 months of water-ageing. The novel PMMA resin incorporating MPC and DMAHDM exhibited potent and lasting protein-repellent and antibacterial properties.

Polymer Additives to Personal Protective Equipment can Inactivate Pathogens.

Face masks have been proven to be medicine’s best public health tool for preventing transmission of airborne pathogens. However, in situations with continuous exposure, lower quality and “do-it-yourself” face masks cannot provide adequate protection against pathogens, especially when mishandled. In addition, the use of multiple face masks each day places a strain on personal protective equipment (PPE) supply and is not environmentally sustainable. Therefore, there is a significant clinical and commercial need for a reusable, pathogen-inactivating face mask. Herein, we propose adding quaternary poly(dimethylaminohexadecyl methacrylate), q(PDMAHDM), abbreviated to q(PDM), to existing fabric networks to generate “contact-killing” face masks—effectively turning cotton, polypropylene, and polyester into pathogen resistant materials. It was found that q(PDM)-integrated face masks were able to inactivate both Gram-positive and Gram-negative bacteria in liquid culture and aerosolized droplets. Furthermore, q(PDM) was electrospun into homogeneous polymer fibers, which makes the polymer practical for low-cost, scaled-up production.Supplementary InformationThe online version contains supplementary material available at 10.1007/s10439-022-03100-1.

Novel antibacterial low-shrinkage-stress resin-based cement

ObjectiveA 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. MethodsThe 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. ResultsThe 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). ConclusionsThe new antibacterial low-shrinkage-stress resin-based cement provides strong antibacterial action and maintains excellent mechanical properties with reduced polymerization shrinkage stress. Clinical significanceA 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.

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

ObjectiveThe cariogenic biofilm on enamel, restoration, and bonding interface is closely related to dental caries and composite restoration failure. Enamel remineralization at adhesive interface is conducive to protecting bonding interface and inhibiting secondary caries. This study intended to assess the remineralization efficiency of adhesive with dimethylaminohexadecyl methacrylate (DMAHDM) and nanoparticles of amorphous calcium phosphate (NACP) on initial caries lesion of biofilm-coated enamel. MethodsArtificial initial carious lesion was created via 72-hour immersion in demineralization solution and cariogenic biofilm was formed after 24-hour culture of Streptococcus mutans (S. mutans). Specimens were then divided into 4 groups: enamel control, enamel treated with NACP, DMAHDM and NACP+DMAHDM respectively. Samples next underwent 7-day cycling, 4 h in BHIS (brain heart infusion broth containing 1 % sucrose) and 20 h in AS (artificial saliva) per day. The pH of BHIS was tested daily. So did the concentration of calcium and phosphate in BHIS and AS. Live/dead staining, colony-forming unit (CFU) count, and lactic acid production of biofilms were measured 7 days later. The enamel remineralization efficiency was evaluated by microhardness testing and transverse microradiography (TMR) quantitatively. ResultsEnamel of NACP+DMAHDM group demonstrated excellent remineralization effectiveness. And the NACP+DMAHDM adhesive released a great number of Ca2+ and PO43- ions, increased pH to 5.81 via acid neutralization, decreased production of lactic acid, and reduced CFU count of S. mutans (P < 0.05). SignificanceThe NACP+DMAHDM adhesive would be applicable to preventing secondary caries, strengthening enamel-adhesive interface, and extending the lifespan of composite restoration.

Effects of thermal cycling on mechanical and antibacterial durability of bioactive low-shrinkage-stress nanocomposite

ObjectivesRecent studies developed low-shrinkage-stress composite with remineralizing and antibacterial properties to combat secondary caries and increase restoration longevity. However, their long-term durability in thermal cycling is unclear. The objectives of this study were to develop an antibacterial, remineralizing and low-shrinkage-stress composite, and to investigate its durability in thermal cycling for 20,000 cycles, equivalent to two years of clinical life. MethodsThe resin consisted of urethane dimethacrylate (UDMA) and triethylene glycol divinylbenzyl ether (TEG-DVBE). Composites were made with 5% dimethylaminohexadecyl methacrylate (DMAHDM) and 20% of nanoparticles of amorphous calcium phosphate (NACP). Composites were thermal cycled at 5°C and 55°C for 20,000 cycles. A human salivary biofilm model was used to evaluate antibiofilm activity before and after thermal cycling. ResultsAfter 20,000 cycles, the flexural strength of bioactive low-shrinkage-stress composite matched commercial control with no antibacterial activity (p > 0.05). Surface roughness was clinically acceptable at less than 0.2 μm. UV+NACP+DMAHDM composite reduced the total microorganisms, total streptococci, and mutans streptococci by 2-5 logs, compared to commercial composite. Biofilm lactic acid production was reduced by 11 folds. The antibacterial performance was maintained after thermal cycling, with no decrease after 20,000 cycles. ConclusionsBioactive low-shrinkage-stress composite possessed good mechanical properties that matched commercial composite both before and after thermal cycling. The new composite had potent antibacterial activity, which was maintained and did not decrease after thermal cycling. Clinical significanceThe new bioactive low-shrinkage-stress composite could reduce polymerization shrinkage stress and release calcium and phosphate ions, with good mechanical properties and strong antibacterial function that were durable after thermal cycling. These properties indicate great potential for inhibiting recurrent caries and increasing the restoration longevity.