Mild hyperthermia enhanced synergistic uric acid degradation and multiple ROS elimination for an effective acute gout therapy.

BACKGROUND: Acute gouty is caused by the excessive accumulation of Monosodium Urate (MSU) crystals within various parts of the body, which leads to a deterioration of the local microenvironment. This degradation is marked by elevated levels of uric acid (UA), increased reactive oxygen species (ROS) production, hypoxic conditions, an upsurge in pro-inflammatory mediators, and mitochondrial dysfunction. RESULTS: In this study, we developed a multifunctional nanoparticle of polydopamine-platinum (PDA@Pt) to combat acute gout by leveraging mild hyperthermia to synergistically enhance UA degradation and anti-inflammatory effect. Herein, PDA acts as a foundational template that facilitates the growth of a Pt shell on the surface of its nanospheres, leading to the formation of the PDA@Pt nanomedicine. Within this therapeutic agent, the Pt nanoparticle catalyzes the decomposition of UA and actively breaks down endogenous hydrogen peroxide (H2O2) to produce O2, which helps to alleviate hypoxic conditions. Concurrently, the PDA component possesses exceptional capacity for ROS scavenging. Most significantly, Both PDA and Pt shell exhibit absorption in the Near-Infrared-II (NIR-II) region, which not only endow PDA@Pt with superior photothermal conversion efficiency for effective photothermal therapy (PTT) but also substantially enhances the nanomedicine's capacity for UA degradation, O2 production and ROS scavenging enzymatic activities. This photothermally-enhanced approach effectively facilitates the repair of mitochondrial damage and downregulates the NF-κB signaling pathway to inhibit the expression of pro-inflammatory cytokines. CONCLUSIONS: The multifunctional nanomedicine PDA@Pt exhibits exceptional efficacy in UA reduction and anti-inflammatory effects, presenting a promising potential therapeutic strategy for the management of acute gout.

Odontogenic and anti-inflammatory effects of magnesium-doped bioactive glass in vital pulp therapy.

This study aimed to investigate the effects of magnesium-doped bioactive glass (Mg-BG) on the mineralization, odontogenesis, and anti-inflammatory abilities of human dental pulp stem cells (hDPSCs). Mg-BG powders with different Mg concentrations were successfully synthesized via the sol-gel method and evaluated using X-ray diffraction, Fourier-transform infrared spectroscopy, scanning electron microscopy, and transmission electron microscopy. Apatite formation was observed on the surfaces of the materials after soaking in simulated body fluid. hDPSCs were cultured with Mg-BG powder extracts in vitro, and no evident cytotoxicity was observed. Mg-BG induced alkaline phosphatase (ALP) expression and mineralization of hDPSCs and upregulated the expression of odontogenic genes, including those encoding dentin sialophosphoprotein, dentin matrix protein 1, ALP, osteocalcin, and runt-related transcription factor 2. Moreover, secretion of inflammatory cytokines (interleukin [IL]-4, IL-6, IL-8, and tumor necrosis factor-alpha) was substantially suppressed by Mg-BG. Collectively, the results of this study suggest that Mg-BG has excellent in vitro bioactivity and is a potential material for vital pulp therapy for inflamed pulps.

A low-shrinkage-stress and anti-bacterial adherent dental resin composite: physicochemical properties and biocompatibility.

Polymerisation shrinkage and biofilm accumulation are the two main problems associated with dental resin composites (DRCs) that induce secondary caries, which can cause restoration failure. Polymerisation shrinkage can lead to microleakage gaps between the tooth and the DRCs, causing the aggregation of bacteria and development of secondary caries. Reducing the shrinkage stress (SS) and improving the resistance to bacterial adhesion have always been the focus of this field in modifying DRCs. A thiol-ene resin system can effectively reduce the polymerisation SS via its step-growth mechanism for delaying the gel point. Fluorinated compounds can reduce the surface free energies, thereby reducing bacterial adhesion. Thus, in this study, a range of mass fractions (0, 10, 20, 30, and 40 wt%) of a fluorinated thiol-ene resin system were added to a fluorinated dimethacrylate resin system/tricyclo decanedimethanol diacrylate to create a fluorinated methacrylate-thiol-ene ternary resin matrix. DRCs were prepared using the obtained ternary resin matrix, and their physical and chemical properties, effect on bacterial adhesion, and biocompatibility were investigated. The results demonstrated that the volumetric shrinkage and SS of the DRCs were reduced with no reduction in conversion degree even after the thiol-ene resin system was added. All DRC-based fluorinated resin systems exhibited an excellent anti-bacterial adhesion effect, as evidenced by the colony-forming unit counts, live/dead bacterial staining, and crystal violet staining tests against Streptococcus mutans (S. mutans). The genetic expressions associated with the bacterial adhesion of S. mutans were substantially affected after being cultured with fluorinated DRCs. All fluorinated DRCs demonstrated good biocompatibility through the in vitro cytotoxicity test and live/dead staining images of the L-929 cells. The above results illustrate that the DRCs based on the fluorinated methacrylate-thiol-ene resin matrix can be potentially applied in clinical practice due to their low SS and anti-bacterial adhesion effect.

The mechanism of biomineralization: Progress in mineralization from intracellular generation to extracellular deposition.

Biomineralization is a highly regulated process that results in the deposition of minerals in a precise manner, ultimately producing skeletal and dental hard tissues. Recent studies have highlighted the crucial role played by intracellular processes in initiating biomineralization. These processes involve various organelles, such as the endoplasmic reticulum(ER), mitochondria, and lysosomes, in the formation, accumulation, maturation, and secretion of calcium phosphate (CaP) particles. Particularly, the recent in-depth study of the dynamic process of the formation of amorphous calcium phosphate(ACP) precursors among organelles has made great progress in the development of the integrity of the biomineralization chain. However, the precise mechanisms underlying these intracellular processes remain unclear, and they cannot be fully integrated with the extracellular mineralization mechanism and the physicochemical structure development of the mineralization particles. In this review, we aim to focus on the recent progress made in understanding intracellular mineralization organelles' processes and their relationship with the physicochemical structure development of CaP and extracellular deposition of CaP particles.

Low shrinkage bulk-filled dental resin composites with non-estrogenic dimethacrylate.

This study synthesized and characterized different proportions of nonestrogenic di(meth)acrylate 9,9-bis[4-((2-(2-methacryloyloxy)ethyl-carbamate)ethoxy)phenyl] fluorine (Bis-EFMA)-based resin composite systems to study their physical, chemical, optical and biological characteristics, and adhesive properties after bonding to a tooth. The estrogenic activity of raw materials was evaluated and compared with estrogen and commercial bisphenol A. After photopolymerization, all resin composite systems were prepared, and their properties were systematically investigated. Notably, the nonestrogenic di(meth)acrylate Bis-EFMA exhibited a more suitable refractive index, excellent biocompatibility, low marginal microleakage and improved bonding strength. Except for the pure UDMA and Bis-EFMA groups, the depth of cure and Vickers microhardness ratios of all the other groups met the requirements of bulk filling (one-time curing depth of more than 4 mm). Bis-EFMA resin systems exhibited lower volumetric polymerization shrinkage (about 3-5%), higher curing depth (>6 mm in specific proportions), mechanical properties (flexural strength of 120-130 MPa, etc.), and microtensile bonding strength (>27.8 MPa), which were comparable or superior to Bis-GMA or commercial composites. Herein, we believe that the novel nonestrogenic di(meth)acrylate (Bis-EFMA) has a wide application prospect as an alternative to Bis-GMA.

New Materials and Their Applications: Perspectives in Restorative Dentistry and Endodontics.

"New Materials and Their Application: Perspectives in Restorative Dentistry and Endodontics" is a new open Special Issue of Materials, which aims to publish original and review articles on novel scientific research that closely relates to new dental materials and their synthesis, function, characteristics, and applications [...].

Properties of Bis-GMA free bulk-filled resin composite based on high refractive index monomer Bis-EFMA.

With the aim to prepare Bis-GMA-free bulk-filled dental resin composite (DRC), Bis-GMA-free resin matrix was prepared by mixing Bis-EFMA with TEGDMA at two mass ratios (Bis-EFMA/TEGDMA = 50 wt/50 wt and 60 wt/40 wt), and the bulk-filled resin composites were then obtained by mixing resin matrix with silanated glass fillers at a mass ratio of 30 wt/70 wt. Bis-GMA based resin composites were used as control. Refractive indexes of resin matrixes were measured. Besides the depth of cure mentioned in ISO standard, double bond conversion (DC) and bottom/top Vickers hardness (VHN) ratio of resin composites were investigated to evaluate the curing depth. Physicochemical properties, such as flexural properties, volumetric shrinkage (VS), shrinkage stress (SS), water sorption (WS) and solubility (SL), and cytotoxicity of resin composites were tested and statistically analyzed (ANOVA, Tukey's, p = 0.05). The results showed that Bis-EFMA/TEGDMA resin matrixes had higher refractive indexes than Bis-GMA/TEGDMA resin matrixes. Viscosities of Bis-EFMA based DRCs were higher than Bis-GMA based DRCs. Bis-EFMA-based (50/50) DRC had comparable depth of cure, DC, and VHN as Bis-GMA-based (50/50) DRC (p > 0.05). Though Bis-EFMA/TEGDMA (60/40) had the highest refractive index in all resin matrix, the corresponding DRCs had the lowest depth of cure, DC, and bottom/top VHN ratio in all groups (p < 0.05). Replacing Bis-GMA with Bis-EFMA had no negative effect on flexural properties, WS and SL of DRCs, and could reduce VS and SS of DRCs. Results of CCK8 assay showed that all of DRCs had the same cytotoxicity (p > 0.05), and the thickness of sample had no influence on the cytotoxicity (p > 0.05). All the results indicated that Bis-EFMA could be used to replace Bis-GMA to prepare bulk-filled dental resin composites. According to the results of depth of cure, DC, and bottom/top VHN ratio, 50 wt/50 wt was more appropriate than 60 wt/40 wt as the mass ratio of Bis-EFMA and TEGDMA in the resin matrix for bulk-filled dental resin composites.

Promotion Effect of Carboxymethyl Chitosan on Dental Caries via Intrafibrillar Mineralization of Collagen and Dentin Remineralization.

OBJECTIVE: To observe ultrastructural changes during the process of carboxymethyl chitosan (CMC)-mediated intrafibrillar mineralization, we evaluated the biomimetic remineralization potential of CMC in type-I collagen fibrils and membranes, and further explored the bond strength as well as the bond interfacial integrity of the biomimetic remineralized artificial caries-affected dentin (ACAD). METHODS: A mineralized solution containing 200 µg/mL CMC was used to induce type-I collagen biomimetic remineralization in ACAD, while traditional mineralization without CMC was used as a control. The process and pattern of mineralization were investigated by transmission electron microscopy (TEM), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDS) as well as structured illumination microscopy (SIM). The Vickers hardness test was used to quantify the dentin hardness, while the microtensile bond strength (µTBS) test was used to assess the bond strength and durability. The bond interfacial integrity was evaluated by a confocal laser scanning microscope (CLSM). RESULTS: TEM, SEM, and SIM images showed that CMC had a positive effect on stabilizing amorphous calcium phosphate (ACP) and promoting intrafibrillar mineralization, while extrafibrillar mineralization was formed without CMC. Furthermore, hardness evaluation and µTBS proved that CMC significantly increased dentin hardness and bond strength. CLSM indicated that CMC could create a significantly better bond interfacial integrity with less of a micro-gap in ACAD. SIGNIFICANCE: CMC possessed the ability to promote intrafibrillar mineralization and remineralization in demineralized caries dentin lesions, as well as improve bond performance, which implied its potential in carious dentin demineralization or dentin hypersensitivity and possibly even as a possible material for indirect pulp-capping, to deal with deep caries. HIGHLIGHTS: CMC possessed the ability to induce intrafibrillar mineralization effectively; the bond strength and bond durability of demineralized caries dentin were improved via CMC-induced remineralization; the CMC-induced remineralization complex is a potential material for indirect pulp-capping, to deal with deep caries.

Preparation of Bis-GMA free dental resin composites with anti-adhesion effect against Streptococcus mutans using synthesized fluorine-containing methacrylate (DFMA).

With purpose of preparing Bis-GMA free dental resin composites (DRCs) with anti-adhesion effect against Streptococcus mutans (S. mutans), a new fluorinated dimethacrylate (DFMA) was synthesized and used as base resin of DRCs. Two reactive diluents TEGDMA and SR833s were mixed with DFMA separately to prepare resin matrixes. After mixing with inorganic fillers, two DFMA based DRCs were obtained and named as DT (DFMA/TEGDMA) and DS (DFMA/SR833s) according to the resin matrix composition. Bis-GMA based DRC (BT) was used as control. The double bond conversion (DC), bacteria adhesion, mucin adsorption, contact angle, surface free energy, volumetric shrinkage (VS), shrinkage stress (SS), water sorption (WS) and solubility (SL), flexural strength (FS) and modulus (FM) before and after water immersion were investigated, and all the results were statistically analyzed with ANOVA analysis. The results showed that DT and DS had comparable (ρ > 0.05) surface free energy which was lower than that of BT (ρ < 0.05). Compared with BT, with the same surface roughness (ρ > 0.05), less amount of S. mutans was accumulated on the surface of DT and DS (ρ < 0.05). In all DRCs, the DS had the best resistance to mucin adsorption (ρ < 0.05) due to its high hydrophobicity. Compared with BT, both DFMA based DRCs had advantages such as lower VS and SS (ρ < 0.05), lower WS and SL (ρ < 0.05), and better water resistance. The DS, which had antibacterial adhesion effect, mucin adsorption resistance, lowest VS and SL (ρ < 0.05), and the highest FS and FM no matter before or after water immersion (ρ < 0.05) was considered to have the best comprehensive properties in all DRCs.

Effect of poly (γ-glutamic acid)/tricalcium phosphate (γ-PGA/TCP) composite for dentin remineralization in vitro.

The poly (γ-glutamic acid)/tricalcium phosphate (γ-PGA/TCP) composite was fabricated as a novel biomineralization material function in preventing caries. Demineralized bovine dentin specimens were prepared and randomly divided into 5 groups (i. α-TCP, ⅱ. γ-PGA, ⅲ. γ-PGA/TCP, ⅳ. CPP-ACP, and ⅴ. deionized water) and subjected to 14 days of pH cycling. Remineralization ability was evaluated by lesion depth, mineral loss and microhardness. The morphology of dentin depositions was observed with scanning electron microscope (SEM), the crystal structure was determined by X-ray diffraction (XRD), and the wettability was tested by contact angle measurements. ANOVA revealed specimens treated by γ-PGA/TCP presented the statistically least lesion depth (p<0.01) and mineral loss (p<0.001), and the highest hardness (p<0.001). SEM revealed prominent intra- and inter-tubular precipitates in both γ-PGA and γ-PGA/TCP groups. The XRD patterns of the deposition structures in all groups were similar to those of sound dentin, and the contact angle of water decreased after γ-PGA/TCP treatment.

A universal adhesive incorporating antimicrobial peptide nisin: effects on Streptococcus mutans and saliva-derived multispecies biofilms.

For purpose of enhancing the antibacterial activity of a universal adhesive, the antimicrobial peptide nisin was incorporated into Single Bond Universal and its antibacterial effect on Streptococcus mutans monospecific biofilms and saliva-derived multispecies biofilms was studied. Nisin was incorporated into Single Bond Universal and the antibacterial activity was examined by confocal laser scanning microscopy (CLSM), reverse transcription-quantitative polymerase chain reaction (qRT-PCR), phenol-sulfuric acid method and lactate dehydrogenase enzymatic method. The bonding properties were tested by microtensile bond strength (µTBS) and degree of conversion (DC). Data were analyzed by one-way analysis of variance (ANOVA) and least significant difference multiple comparison tests (P < 0.05). The Single Bond Universal incorporated with 3% (w/v) nisin could significantly inhibit the growth of the S. mutans monospecific biofilms (P< 0.01) and decrease the expression of genes related to extracellular polysaccharide (EPS) synthesis (gtfB, gtfC, gtfD and spaP) and acidogenicity (ldh) (P < 0.05). 3% (w/v) nisin-incorporated Single Bond Universal could also inhibit the growth of saliva-derived multispecies biofilms and decrease the excretion of EPS and lactic acid ( P< 0.05). µTBS and DC of 3% (w/v) nisin-incorporated Single Bond Universal did not deteriorate obviously (P > 0.05). In conclusion, 3% (w/v) nisin-incorporated Single Bond Universal substantially inhibited the growth of both S. mutans monospecific and saliva-derived multispecies biofilms without compromising the bonding properties.

Influence of molecular weight and concentration of carboxymethyl chitosan on biomimetic mineralization of collagen.

The objective of the present study was to systematically investigate the influence of molecular weight (MW) and concentration of carboxymethyl chitosan (CMC), which served as non-collagenous protein (NCP) surrogates, on biomimetic mineralization of type I collagen. Supersaturated CMC-stabilized amorphous calcium-phosphate (CMC-ACP) dispersions containing different MWs (20 kDa, 60 kDa, 150 kDa) and concentrations (25, 50, 100, 200, 400 µg ml-1) of CMC were prepared. After mineralization in the aforementioned dispersions for 7 days, the pattern and extent of biomimetic mineralization of collagen scaffolds were investigated. Our study showed that increasing CMC concentration resulted in increasing stability and decreasing particle size of CMC-ACP dispersions. Images from scanning and transmission electron microscopy revealed that intrafibrillar mineralization of collagen was obtained with 20k-200, 60k-100, 60k-200 and 150k-200 CMC-ACP dispersions, with hydroxyapatite (HAp) formation confirmed by Fourier transform infrared spectroscopy and X-ray diffraction measurements, whereas HAp formed extrafibrillar clusters in other collagen scaffolds. Thermogravimetric analysis showed that the combined effect of MW and concentration of CMC contributed to different extents of biomimetic mineralization, and was correlated with the stability and particle size of CMC-ACP dispersions, and the size-exclusion characteristics of type I collagen. The results of this work support the effective function of CMC as NCP analogs, and provide parameters of MWs and concentrations of CMC for applications in hard tissue engineering as well as insights into intersections of mechanisms in biomimetic mineralization.

The inhibitory effect of carboxyl-terminated polyamidoamine dendrimers on dentine host-derived matrix metalloproteinases in vitro in an etch-and-rinse adhesive system.

The biomimetic remineralization of collagen fibrils has increased interest in restoring the demineralized dentine generated by dental caries. Carboxyl-terminated polyamidoamine dendrimers (PAMAM-COOH), hyperbranched polymeric macromolecules, can act as non-collagenous proteins to induce biomimetic remineralization on a dentine organic matrix. However, in vivo remineralization is an extremely time-consuming process; before complete remineralization, demineralized dentine collagen fibrils are susceptible to degradation by host-derived matrix metalloproteinases (MMPs). Therefore, we examined the effect of fourth-generation PAMAM-COOH (G4-PAMAM-COOH) on the collagenolytic activities of endogenous MMPs, the interaction between G4-PAMAM-COOH and demineralized dentine collagen and the influence of G4-PAMAM-COOH pre-treatment on resin-dentine bonding. G4-PAMAN-COOH not only inhibited exogenous soluble rhMMP9 but also hampered the proteolytic activities of dentine collagen-bound MMPs. Cooperated with the results of G4-PAMAM-COOH absorption and desorption, FTIR spectroscopy provided evidence for the exclusive electrostatic interaction rather than hydrogen or covalent bonding between G4-PAMAM-COOH and dentine collagen. Furthermore, G4-PAMAM-COOH pre-treatment showed no damage to resin-dentine bonding because it did not significantly decrease the elastic modulus of the demineralized dentine, degree of conversion, penetration of the adhesive into the dentinal tubules or ultimate tensile strength. Thus, G4-PAMAM-COOH can effectively inactivate MMPs, retard the enzymolysis of collagen by MMPs and scarcely influence the application of resin-dentine bonding.

Use of experimental-resin-based materials doped with carboxymethyl chitosan and calcium phosphate microfillers to induce biomimetic remineralization of caries-affected dentin.

This study investigated carboxymethyl chitosan (CMC)-induced biomimetic mineralization of collagen fibrils, with the aim of synthesizing experimental resins doped with CMC and calcium phosphate microfillers to remineralize artificial caries-affected dentin (ACAD) and enhance resin-dentin bonding durability. A size exclusion test provided evidence for the rejection of CMC (Mw 150 kDa) by collagen fibrils. Transmission electron microscopy and selected area electron diffraction conducted on reconstituted two-dimensional collagen showed typical deposition of needle-like hydroxyapatite crystals within collagen fibrils through CMC-induced biomimetic mineralization. The Vickers hardness test revealed significant improvement (P < 0.001) of the hardness of ACAD treated with CMC-containing experimental resins. Confocal laser scanning microscopy showed reduced dentin permeability and defect sites after biomimetic mineralization. On microtensile bond strength testing, the CMC-remineralized ACAD had better bonding with resin than ACAD and traditionally remineralized ACAD in both self-etch and etch-and-rinse bonding modes (P < 0.001). In conclusion, CMC is efficient in directing the biomimetic mineralization of collagen fibrils. The experimental resins containing CMC can induce dentin biomimetic remineralization and improve the bonding performance of ACAD.

Sodium Fluoride under Dose Range of 2.4-24 µM, a Promising Osteoimmunomodulatory Agent for Vascularized Bone Formation.

Fluoride has essential effects on bone physiological activity and is widely used in bone biomaterials modification. However, this beneficial effect is highly related to the dose range and improper dosing can lead to pathological conditions such as fluorosis of bone. Therefore, this study first investigated the dose dependent effect of fluoride on bone regeneration. In the range of 0.24-240 µM, in vivo vascularized bone formation can be achieved via fine-tuning the fluoride concentration, and the peak osteogenic effect was found at 2.4-24 µM. The underlying mechanism is related to the modulation of the osteoimmune environment. Fluoride elicited significant osteoimmunomodulatory effect in modulation of the inflammatory cytokines and expression of osteogenic factors (BMP2, OSM, spermine/spermidine) and angiogenic factor (VEGF, IGF-1) during the early response. Fluorine with the doses of 2.4 and 24 µM could increase polyamines and IGF-1 production in macrophages, thus promoting osteogenesis of BMSCs and angiogenesis of HUVECs. These doses could also inhibit the inflammatory response of macrophages. In vitro osteogenesis and angiogenesis were both improved by the fluorine (2.4 and 24 µM)/macrophage conditioned medium, which is consistent with the in vivo results. These results collectively imply that fluoride is an effective osteoimmunomodulatory agent that can regulate both osteogenesis and angiogenesis. "Osteoimmune-smart" bone biomaterials can be developed via incorporating fluorine, and the release concentration should be controlled within the range of 2.4-24 µM for improved bone formation.

LL-37 inhibits LPS-induced inflammation and stimulates the osteogenic differentiation of BMSCs via P2X7 receptor and MAPK signaling pathway.

Oral diseases, such as periapical periodontitis and periodontitis, are characterized by inflammation-induced bone loss. LL-37, a human antimicrobial peptide (AMP), has multiple biological functions and the potential to promote osteogenesis. Therefore, this study aimed to investigate the regulatory effects of LL-37 within normal and inflammatory microenvironments. The roles of P2X7 receptor (P2X7R) and mitogen-activated protein kinase (MAPK) signaling pathway were also demonstrated. The results showed that LL-37 promoted bone marrow stromal cell (BMSC) proliferation, migration and osteogenic differentiation. LL-37 inhibited the expression of the inflammatory cytokines interleukin-1ß (IL-1ß), tumor necrosis factor-α (TNF-α) and receptor activator of nuclear factor kappa-B ligand (RANKL) at both protein and gene levels, and attenuated the lipopolysaccharide (LPS)-induced inhibition of osteogenesis. Immunofluorescence (IF) confirmed P2X7R expression in BMSCs. BBG, a P2X7R antagonist, significantly attenuated LL-37-promoted osteogenesis. The phosphorylation of extracellular signal-regulated kinase 1/2 (ERK1/2) and c-Jun NH2-terminal kinase (JNK) increased after LL-37 stimulation, which did not affect p38 phosphorylation. The effects of LL-37 on osteogenesis-related gene expression were markedly attenuated by selective inhibitors of ERK1/2 and JNK. Furthermore, a mouse model of LPS-stimulated calvarial osteolysis was established, and results showed that LL-37 markedly inhibited osteoclastic bone resorption. In conclusion, we speculate that LL-37 inhibits inflammation and promotes BMSC osteogenesis via P2X7R and MAPK signaling pathway.

Antibacterial effect and bond strength of a modified dental adhesive containing the peptide nisin.

This study attempted to incorporate the antibacterial peptide nisin into an etch-and-rinse dental adhesive to evaluate the antibacterial activity of the modified adhesive against Streptococcus mutans and the bond strength. Single Bond 2 was used as a negative control, and nisin was incorporated at 1%, 3%, and 5% (w/v). The antibacterial activity against S. mutans was evaluated using the film contact test, the agar diffusion test, XTT assays and confocal laser scanning microscopy (CLSM). The microtensile bond strength (µTBS) of the modified dental adhesive was also evaluated. The cured nisin-incorporated dental adhesive exhibited a significant inhibitory effect on the growth of S. mutans (P<0.05), and the inhibitory effect was strengthened as the nisin concentration increased (P<0.05). However, no significant differences in the agar diffusion test were found for the cured nisin-incorporated adhesives compared with the control group. Based on XTT results and CLSM images, the cured nisin-incorporated adhesive interfered with the adherence of S. mutans and the integrity of its biofilms (P<0.05). Compared with the control group, the 1% nisin group did not exhibit a significant difference in µTBS (P>0.05), whereas the 3% and 5% nisin groups displayed decreased bond strength (P<0.05).

Antibacterial activity of the nisin-containing single-bond universal adhesive / 口腔疾病防治

Objective@#To investigate the antibacterial activity to Streptococcus mutans of a nisin-containing single-bond universal adhesive.@*Methods@#Nisin was mixed into the bonding agent to produce concentrations ranging from 0.01 g/mL to 0.05 g/mL for the experiments, and adhesive without nisin was used as the control. Dentin-resin specimens were prepared for the microtensile strength test to evaluate changes in the bonding strength. The proper concentrations were selected for more tests. ① An agar diffusion test was applied with filter paper to detect the release of nisin, and adhesive without nisin was used as the negative control, 0.01 g/mL Nisin aqueous solution was used as the positive control. ② Solidification; resin adhesive specimens were prepared for the assessment of direct contact inhibition activity. ③ Confocal laser scanning microscopy was used to examine the effect of the adhesive on the biological film activity and the ability of Streptococcus mutans to produce extracellular polysaccharides. @*Results @#Nisin did not significantly reduce the bond strength of the modified adhesive at 0.01-0.03 g/mL (P < 0.05); these concentrations were selected for the subsequent antibiosis experiment. Rings could not be observed in the agar diffusion test, except for in the group of adhesive modified with 0.01-0.03 g/mL nisin. Resin adhesive with 0.01-0.03 g/mL nisin could significantly inhibit the proliferation of Streptococcus mutans on the surface of the specimens. The confocal laser scanning microscopy results indicate that only the adhesive resin modified with nisin could reduce the bacteria in the biofilm and the production of extracellular polysaccharides.@*Conclusion@#Single-bond universal adhesive with 0.01-0.03 g/mL nisin can inhibit the growth of Streptococcus mutans and its biofilms on the bonding interface, as well as decrease the production of extracellular polysaccharides, and thus has the potential to decrease the occurrence of secondary caries.

Extrafibrillar collagen demineralization-based chelate-and-rinse technique bridges the gap between wet and dry dentin bonding.

Limitations associated with wet-bonding led to the recent development of a selective demineralization strategy in which dentin was etched with a reduced concentration of phosphoric acid to create exclusive extrafibrillar demineralization of the collagen matrix. However, the use of acidic conditioners removes calcium via diffusion of very small hydronium ions into the intrafibrillar collagen water compartments. This defeats the purpose of limiting the conditioner to the extrafibrillar space to create a collagen matrix containing only intrafibrillar minerals to prevent collapse of the collagen matrix. The present work examined the use of polymeric chelators (the sodium salt of polyacrylic acid) of different molecular weights to selectively demineralize extrafibrillar dentin. These polymeric chelators exhibit different affinities for calcium ions (isothermal titration calorimetry), penetrated intrafibrillar dentin collagen to different extents based on their molecular sizes (modified size-exclusion chromatography), and preserve the dynamic mechanical properties of mineralized dentin more favorably compared with completely demineralized phosphoric acid-etched dentin (nanoscopical dynamic mechanical analysis). Scanning and transmission electron microscopy provided evidence for retention of intrafibrillar minerals in dentin surfaces conditioned with polymeric chelators. Microtensile bond strengths to wet-bonded and dry-bonded dentin conditioned with these polymeric chelators showed that the use of sodium salts of polyacrylic acid for chelating dentin prior to bonding did not result in significant decline in resin-dentin bond strength. Taken together, the findings led to the conclusion that a chelate-and-rinse conditioning technique based on extrafibrillar collagen demineralization bridges the gap between wet and dry dentin bonding. STATEMENT OF SIGNIFICANCE: The chelate-and-rinse dental adhesive bonding concept differentiates from previous research in that it is based on the size-exclusion characteristics of fibrillar collagen; molecules larger than 40kDa are prevented from accessing the intrafibrillar water compartments of the collagen fibrils. Using this chelate-and-rinse extrafibrillar calcium chelation concept, collagen fibrils with retained intrafibrillar minerals will not collapse upon air-drying. This enables adhesive infiltration into the mineral-depleted extrafibrillar spaces without relying on wet-bonding. By bridging the gap between wet and dry dentine bonding, the chelate-and-rinse concept introduces additional insight to the field by preventing exposure of endogenous proteases via preservation of the intrafibrillar minerals within a collagen matrix. If successfully validated, this should help prevent degradation of resin-dentine bonds by collagenolytic enzymes.

Potential applications of antimicrobial peptides and their mimics in combating caries and pulpal infections.

Antimicrobial peptides (AMPs) are short cationic host-defense molecules that provide the early stage of protection against invading microbes. They also have important modulatory roles and act as a bridge between innate and acquired immunity. The types and functions of oral AMPs were reviewed and experimental reports on the use of natural AMPs and their synthetic mimics in caries and pulpal infections were discussed. Natural AMPs in the oral cavity, predominantly defensins, cathelicidins and histatins, possess antimicrobial activities against oral pathogens and biofilms. Incomplete debridement of microorganisms in root canal space may precipitate an exacerbated immune response that results in periradicular bone resorption. Because of their immunomodulatory and wound healing potentials, AMPs stimulate pro-inflammatory cytokine production, recruit host defense cells and regulate immuno-inflammatory responses in the vicinity of the pulp and periapex. Recent rapid advances in the development of synthetic AMP mimics offer exciting opportunities for new therapeutic initiatives in root canal treatment and regenerative endodontics. STATEMENT OF SIGNIFICANCE: Identification of new therapeutic strategies to combat antibiotic-resistant pathogens and biofilm-associated infections continues to be one of the major challenges in modern medicine. Despite the presence of commercialization hurdles and scientific challenges, interests in using antimicrobial peptides as therapeutic alternatives and adjuvants to combat pathogenic biofilms have never been foreshortened. Not only do these cationic peptides possess rapid killing ability, their multi-modal mechanisms of action render them advantageous in targeting different biofilm sub-populations. These factors, together with adjunctive bioactive functions such as immunomodulation and wound healing enhancement, render AMPs or their synthetic mimics exciting candidates to be considered as adjuncts in the treatment of caries, infected pulps and root canals.