Silicon Release Research Articles

Preliminary evaluates of silica/β-TCP/PLGA microspheres for dentin regeneration in vivo

ABSTRACT Silica/β-tri-calcium phosphate/poly (lactic-co-glycolic acid) microspheres, a type of bioactive and biodegradable materials, were produced by a double emulsion and solvent evaporation methods. The biological activity of the microspheres to promote dentin regeneration was investigated in vivo. First, the ionic concentration of silicon in the microspheres was detected by inductively coupled plasma optical emission spectrometry. The results showed the release of silicon continuously and without any obvious burst. Second, the microspheres with or without human dental pulp cells adhered were transplanted into subcutaneous pockets of nude mice to evaluate the bioactivity. The implanted material specimens were obtained after 6 weeks. The specimens were evaluated after H&E staining and toluidine blue staining. The results presented the cells ingrowth of the scaffold material and collagenous tissues around the microspheres. It was demonstrated that the material had outstanding biocompatibility and bioactivity.

Determination of Total Silicon and SiO2 Particles Using an ICP-MS Based Analytical Platform for Toxicokinetic Studies of Synthetic Amorphous Silica.

Synthetic amorphous silica (SAS), manufactured in pyrogenic or precipitated form, is a nanomaterial with a widespread use as food additive (E 551). Oral exposure to SAS results from its use in food and dietary supplements, pharmaceuticals and toothpaste. Recent evidence suggests that oral exposure to SAS may pose health risks and highlights the need to address the toxic potential of SAS as affected by the physicochemical characteristics of the different forms of SAS. For this aim, investigating SAS toxicokinetics is of crucial importance and an analytical strategy for such an undertaking is presented. The minimization of silicon background in tissues, control of contamination (including silicon release from equipment), high-throughput sample treatment, elimination of spectral interferences affecting inductively coupled plasma mass spectrometry (ICP-MS) silicon detection, and development of analytical quality control tools are the cornerstones of this strategy. A validated method combining sample digestion with silicon determination by reaction cell ICP-MS is presented. Silica particles are converted to soluble silicon by microwave dissolution with mixtures of HNO3, H2O2 and hydrofluoric acid (HF), whereas interference-free ICP-MS detection of total silicon is achieved by ion-molecule chemistry with limits of detection (LoDs) in the range 0.2–0.5 µg Si g−1 for most tissues. Deposition of particulate SiO2 in tissues is assessed by single particle ICP-MS.

Effect of biochars, biogenic, and inorganic amendments on dissolution and kinetic release of phytoavailable silicon in texturally different soils under submerged conditions

Extensive cropping leads to higher removal of silicon (Si) from the soils and makes it a limiting element for various crops. Application of silicic acid (H4SiO4) has limited scope due to high cost, low solubility, and high polymerization. The biogenic sources of Si are alternative to silicic acid (H4SiO4) and Si release from these sources is a function of different soil properties like pH, redox potential, texture etc. Kinetics release of plant available Si (PASi) from various organic and inorganic sources was evaluated in texturally different soils such as sandy loam (SL), sandy clay loam (SCL), and clay (CL) under a 60-day incubation study. Our findings suggest that the highest cumulative release of Si (cSi) was observed in SCL (47.6 mg/L) in control sets without any amendments. The highest cSi release among plant residue amendments was observed by bamboo leaves (340 mg/L) and rice husk (RH) (301 mg/L) in SL and SCL soils, respectively. Among biochar amendments, the rice husk biochar (RHB) released the maximum quantity (246.55 and 243.9 mg/L) of Si in SCL and CL soils respectively. Among the ashes, sugarcane bagasse ash had the highest release (316 mg/L) of Si in SCL and RHA which yielded 235.2 Si mg/L in CL soil for 60days. Silicon release kinetics for these sets of systems showed a diffusive behavior of Si being released from amendments primarily dependent on soil type.

Mesoporous Bioactive Glass Combined with Graphene Oxide Quantum Dot as a New Material for a New Treatment Option for Dentin Hypersensitivity.

Dentin hypersensitivity is one of the most common clinical conditions usually associated with exposed dentinal tubules. The purpose of this study was to identify the potential of a graphene oxide quantum dot coating for mesoporous bioactive glass nanoparticles as a new material for the treatment of dentin hypersensitivity by investigating its mineralization activity and dentinal tubules sealing. Mesoporous bioactive glass nanoparticle was fabricated by modified sol-gel synthesis. X-ray diffraction was performed to characterize the synthesized nanoparticle Fourier transform infra-red spectroscopy investigated the functionalized surfaces. The distribution of the specific surface area and the pore size was measure by Pore size analysis. The morphology of sample was observed by Field Emission Scanning Electron Microscope (FESEM) and Field Emission Transmission Electron Microscope (FETEM). After disk-shaped specimens of mesoporous bioactive glass nanoparticles and graphene oxide quantum dot coated mesoporous bioactive glass nanoparticles (n = 3) were soaked in the simulated body fluid for 0, 1, 5, 10,and 30 days, the amount of ions released was observed to confirm the ionic elution for mineralization. Sensitive tooth model discs (n = 20) were applied with two samples and evaluated the dentinal tubule sealing ability. The spherical mesoporous bioactive glass nanoparticles and graphene oxide quantum dot coated mesoporous bioactive glass nanoparticles with a diameter of about 500 nm were identified through FESEM and FETEM. The ion release capacity of both samples appeared to be very similar. The amount of ion released and in vitro mineralization tests confirmed that graphene oxide quantum dot coating of mesoporous bioactive glass nanoparticles did not inhibit the release of calcium, silicon and phosphate ions, but rather that graphene oxide quantum dot promoted hydroxyapatite formation. In the FESEM image of the sensitive tooth disc surface, it was observed that graphene oxide quantum dot coated mesoporous bioactive glass nanoparticles sealed tightly the dentinal tubules. The graphene oxide quantum dot coating of mesoporous bioactive glass nanoparticles not only showed the excellent dentinal sealing ability but also rapidly promoted mineralization while minimizing the size increase by coating the mesoporous bioactive glass nanoparticles.

Promoting bone regeneration of calcium phosphate cement by addition of PLGA microspheres and zinc silicate via synergistic effect of in-situ pore generation, bioactive ion stimulation and macrophage immunomodulation

Calcium phosphate cement (CPC) is an excellent bone graft material due to its self-setting, easiness to shape, good biocompatibility and osteoconductivity. However, low osteogenic activity and slow degradation rate of CPC severely influence its bone regeneration efficiency. Herein, zinc silicate (ZS) and poly (lactic-co-glycolic acid) (PLGA) microspheres were incorporated into CPC to overcome these issues. The addition of ZS obviously downregulated the expression of inflammatory-related genes (interleukin-1β, interleukin-6, and tumor necrosis factor α), while markedly upregulated the anti-inflammatory gene expression (interleukin-10). The incorporation of ZS significantly promoted the adhesion and proliferation of mouse bone marrow stem cells (mBMSCs). In addition, macrophage-conditioned ZS/PLGA/CPC extracts profoundly promoted osteogenic differentiation of mBMSCs, and evidently suppressed osteoclastogenesis of RAW264.7 cells. The optimum added amount of ZS was 10 wt.%. In vivo results also displayed that the addition of 10 wt.% ZS significantly improved bone repair effect of the composite. Therefore, the addition of ZS together with PLGA microspheres is a promising way for modifying the osteogenic activity and degradability of CPC via in-situ pore generation, promoting osteogenic differentiation and macrophage immunomodulation due to the simultaneous release of active silicon and zinc ions.

Calcium and Silicon Delivery to Artificial and Human Nails from Nail Polish Formulations

A deteriorating nail standard is a growing problem as the global prevalence of diabetes is increasing. Systemic treatment with mineral supplements may not be recommended, mainly due to the high doses required to deliver optimal therapeutic concentrations. In this work, we evaluate nail polish formulations for the local delivery of strengthening elements to the nail plate. Specifically, we assess calcium and silicon release from nail polish base coat formulations containing three different concentrations of White Portland Cement to water, as well as to artificial and human nails. The delivery of calcium and silicon to the dorsal nail plate was determined by inductively coupled plasma optical emission spectrometry, scanning electron microscopy, and energy dispersive X-ray spectroscopy. To the best of our knowledge, this is the first study showing that such dual elemental delivery to human nails can be achieved from nail polish formulations. Hence, this work may form the basis for new inventions where therapeutic functionalities can be integrated with the mechanical and cosmetic properties of a base coat nail polish. Future permeability studies are required to verify long-term effects on the nail standard, induced by the formulations under study.

Diversity of silicon release rates among tropical tree species during leaf-litter decomposition

Leaf-litter is a significant source of biogenic Si, and differences among tree species in Si release rates during litter decomposition are important for quantifying Si cycles in forest ecosystems. We conducted two experiments to improve mechanistic understanding of Si release rates from dead leaves, using lowland tropical trees of Sarawak, Borneo. In the first experiment, we assessed Si leaching from leaf litter when they were shaken in water for four hours. In the second experiment, leaf litter samples were allowed to decompose in mesh bags in growth chambers for two months, in order to determine rates of decomposition and Si release, and to explore a relationship between decomposition rate and initial litter chemistry. Among the 12 species with large differences in initial leaf-litter Si concentration (0.72–80.0 mg Si g−1), Si leaching to water varied widely (0.04–0.16 mg Si g−1) and positively correlated with the initial Si concentration (R2 = 0.87; P < 0.001). Si release per unit leaf dry weight in the decomposition experiment was also positively correlated with initial litter Si concentration among six species (R2 = 0.998; P < 0.001). In contrast, proportion of initial Si content released did not exhibit a significant relationship with their decomposition rates, which were correlated with labile carbon content in leaf litter (e.g. hemicellulose). Our results suggest that Si release rates from decomposing leaf litter cannot be simply predicted from decomposition rates. The species differences in locations and stability of opal phytoliths and their resulting effects on Si dissolution rates should be considered.

Assessment of mine tailings as precursors for alkali-activated materials for on-site applications

Year after year the mining industry generates 5–7 billion metric tons of tailings worldwide. They are mostly disposed rather than valorised. The substantial amounts of tailings has led to growing concerns about their ecological and environmental impacts such as occupation of large areas of land, generation of windblown dust, and contamination of surface and underground water. Over the past years the mining industry has been subjected to increase environmental principles. As the consequence, besides waste rock and water management, tailings management becomes a progressively important factor for ecologic and economic reasons.Mine tailings from flotation processes are normally disposed in impoundments on the surface. This may cause environmental and safety problems including serious water pollution arising from contamination of surface water, groundwater, and soils due to the leaching of heavy metals, process reagents, and Sulphur compounds. Recently the process of alkali-activation and geopolymerisation has been explored as a potential method for tailings consolidation and heavy metal fixation. The tailings of many existing mining operations contain the aluminosilicate minerals needed for alkali-activation at least to some extent. From a sustainability point of view it makes sense to use alkali-activated products from tailings directly on the mine site as e.g. (1) backfill material applied to fill open cavities from the (underground) mining operation and (2) cover materials for surface deposits of tailings in order to store them ecologically safe and sealed off from the environment.Mine tailings from different mining operations around the world have been investigated regarding their potential use as precursors for alkali-activated materials. An assessment of the release of gel forming elements into alkaline solutions was performed by leaching experiments under various conditions (time, concentration of the solvent, and temperature). Compared to traditional alkali-activated precursor materials the release of aluminium and silicon is in general low for the mine tailings investigated. However, results indicate a favourable ratio of Si/Al for the formation of gels similar to other alkali-activated products. Additionally, the leached calcium can contribute to the strength of the resulting products by forming C-S-H gels when a considerable amount of Si is present in the pore solution either from the activator or dissolved from the material itself.The results of the leaching tests were used to facilitate the mix design for alkali-activated products. In order to increase the mechanical strength of the final product different approaches were considered: (1) addition of reactive materials (e.g. blast furnace slag), (2) increasing the reactivity of the tailings by grinding, and (3) increasing the reactivity by curing at elevated temperature. Depending on the tailings type, the mix design, and the curing conditions the final material shows a compressive strength in excess of 30 MPa even for curing at low temperatures.The investigated mine tailings can potentially be used for various applications on the mine site. With regard to specific target applications a further evaluation of long term properties of the resulting products (e.g. freeze–thaw resistance) has to be performed. Furthermore, results indicate that products with even higher strength can be manufactured by further reducing the particle size of the tailings or by the addition of other reactive materials.

The Release of Some Elements from Vermiculite during the Short Periods of Incubation by Heterotrophic Bacteria

Microorganisms play an important role in the formation and decomposition of clay minerals. In this research the release of iron, silicon and non-exchangeable potassium from vermiculite owing to heterotrophic bacteria was examined. For this, an experiment was carried out in a completely randomized design at three replications. The experiment factors consisted of bacterial inoculation (control, Pseudomonas sp. Rhizo_9, Enterobacter cloacae Rhizo_33) and incubation period (7, 15, 30, 45 and 60 days). Results showed a significant effect of bacterial inoculation and incubation period on silicon, non-exchangeable potassium and iron release. The most active release of potassium, silicon and iron was recorded at the presence of Enterobactercloacae on the 15, 30 and 45 days after the incubation, respectively. Thin-layer chromatographic analysis of the organic acids in the culture broth of both strains exhibited spots of malic, tartaric and citric acid, produced by Pseudomonas sp. and oxalic, tartaric and unknown acid produced by Enterobactercloacae. The XRD results of mineral decomposition with bacterial treatments indicated converted vermiculite with limited expansion into expansible smectite.

Release of phosphorus and silicon from minerals by soil microorganisms depends on the availability of organic carbon

Microorganisms release nutrients from minerals. However, this process is not yet well understood despite its importance for soil fertility. The aim of this study was to determine which factors control microbial phosphorus (P) and silicon (Si) release from apatite and weathered rock, and to analyze which microbial-mediated processes cause P and Si solubilization. For this purpose, we conducted a series of incubation experiments with apatite and saprolite (weathered bedrock) and soil extracts of four soils that are located along a climate gradient in the Coastal Cordillera of Chile and differ in soil P fractions and degree of weathering. We developed an approach that allowed us to measure the release of P from apatite and the release of Si from saprolite by microbial consortia in soil solution. The microbial consortia of all soil extracts caused release of P from apatite. The addition of carbon (C) and nitrogen (N) to the soil solution increased the rate of microbial P solubilization from apatite by a factor of about 10 in all soil depth increments. The pH decreased strongly during the incubations. In the depth increments 0.1–0.2 and 0.4–0.6 m, the P solubilization rates were negatively correlated with the pH measured at the end of the incubation (r2 = 0.55 and 0.76, respectively, both p < 0.01). Nine organic acids were detected throughout the experiment. The total concentration of carboxyl groups was positively correlated with the P solubilization rate (r2 = 0.94, p < 0.01). The addition of dissolved inorganic P to the soil extracts did not significantly decrease the P solubilization rates. The rate of microbial Si solubilization from saprolite increased strongly with the surface area of the saprolite. We conclude that microbial solubilization of P from apatite was limited by the availability of easily decomposable C and that microbial solubilization of P from apatite was not affected by P availability, indicating that this process is not or not exclusively controlled by microbial need for P. In conclusion, our results indicate that microbial weathering of minerals in saprolite is strongly constrained by the availability of organic C and by the specific surface area of the saprolite.

Ion Release From Prototype Surface Pre-Reacted Glass Ionomer (S-PRG) Sealer and EndoSequence BC Sealer.

Objective:Bioactive ions, when incorporated in an endodontic sealer, can contribute to the long-term success of endodontic therapy by combating the re-infection of a tooth and promoting the healing of the periapical bone. The objective of this study was to measure the release of boron, strontium, and silicon ions from surface pre-reacted glass ionomer (S-PRG) filler containing prototype endodontic sealer over a sustained period in comparison to EndoSequence BC sealer in a simulated clinical model using extracted human teeth in vitro.Methods:Twelve extracted human anterior teeth were instrumented using ProTaper Next (Dentsply Sirona, Johnson City, TN, USA) files up to size X3 (#30/variable taper) with copious 2.5% NaOCl irrigation. Teeth were obturated using a single-cone technique with a matching size tapered gutta-percha point and one of two endodontic sealers: prototype S-PRG (Shofu Inc., Kyoto, Japan) or EndoSequence BC (Brasseler, Savannah, GA, USA). The teeth were soaked in phosphate-buffered saline (PBS) solution for 336 hours. Periodically, 1-mL samples of the PBS were analyzed via an inductively coupled plasma mass spectrometer to determine the concentrations of ions released by the sealers.Results:The average (S.D.) cumulative release (ng/ml) of boron, silicon, and strontium ions over 2 weeks for the prototype S-PRG sealer was 8614.9 (1264.3), 35758.9 (5986.5), and 3965.2 (145.6), and for EndoSequence BC sealer was 1860.5 (82.7), 164648.7 (16468.1), and 227.7 (4.7). Generalized linear mixed model analysis showed significant differences in ion concentration among boron, silicon, and strontium over time between the two sealer groups (Boron: P<0.0001, Silicon: P=0.010, Strontium: P=0.028). Of the three ions, strontium had the lowest amount of release for both sealers. The prototype S-PRG sealer showed a rapid initial burst followed by a slow, continuous release of strontium ions.Conclusion:The prototype S-PRG sealer released boron and strontium ions in higher cumulative concentrations over 2 weeks compared to the EndoSequence BC sealer. Both the prototype S-PRG and EndoSequence BC sealers released silicon ions, although significantly more were eluted from the EndoSequence BC sealer. Antimicrobial and osteogenic ion release from sealers is expected to positively influence the post-treatment control of microbial infections to improve periapical healing.

Effects of background fertilization followed by co-application of two kinds of bacteria on soil nutrient content and rice yield in Northeast China

With the improvement of living standards, people pay more and more attention to the quality and safety of rice. Microbial agents are favored by the public because they can activate the nutrient supply in the soil, and reduce the residue and application amount of chemical fertilizers and pesticides. Based on the conventional fertilization in the field, Bacillus mucilaginosus and Aspergillus niger were applied, Bacillus mucilaginosus was inoculated at four levels in the paddy soil in the cold region of Heilongjiang Province of China. The effects of different proportions of Bacillus mucilaginosus and Aspergillus niger on the number of soil microorganisms, enzyme activity, microbial biomass, soil biochemical intensity, soil nutrient content, plant nutrient content and yield were studied, and the effects on the plant nutrient content of rice and the nutrient dynamics were discussed. The results showed that a 2.62%-21.20% higher yield of rice obtained from co-application treatments compared with that of the control-blank treatment. Furthermore, the highest yield obtained (10736±65 kg/hm2) suggested that the optimized values for the two bacteria applied were 120×1011 CFU/hm2 for Bacillus mucilaginosus and 15×1011 CFU/hm2 for Aspergillus niger. Bacillus mucilaginosus can decompose minerals in soil, dissolve potassium and silicon, decompose apatite and release phosphorus into soil. Aspergillus niger can transform the phosphate which cannot be absorbed by plants into soluble phosphate which can be directly absorbed by plants by producing non-volatile acids. In particular, Bacillus mucilaginosus and Aspergillus niger have synergistic effect, and their combined application effect is greater than that of two bacteria alone. Co-application promoted the release of soil soluble silicon, and then increased the silicon content of plants. At the same time, soil microorganism, microbial biomass, enzyme activity and biochemical activity all increased significantly. This study provides an effective way to reduce the amount of chemical fertilizer applied in rice production in cold regions of China. Keywords: microbial inoculants, microbial fertilizer, rice, co-application, Bacillus mucilaginosus, Aspergillus niger, nutrients DOI: 10.25165/j.ijabe.20201302.4863 Citation: Sun T, Liu Y Y N, Wu S, Zhang J Z, Qu B, Xu J G. Effects of background fertilization followed by co-application of two kinds of bacteria on soil nutrient content and rice yield in Northeast China. Int J Agric & Biol Eng, 2020; 13(2): 154–162.

PH-dependent silicon release from phytoliths of Norway spruce (Picea abies)

Accurate evaluation of the preservation state of fossil phytoliths in glacial lake sediments is important, as these microfossils are often used in paleoecological and archaeological studies. The characteristic phytolith type of the Norway spruce (Picea abies [L.] Karst.) needle is a potential keystone in paleoecological studies. In this laboratory study, we investigated dissolution of Picea abies blocky type phytoliths, to simulate dissolution processes in sediments and soils and create reference material to compare with fossil phytoliths. Intact needles, needle ash, diatomite and silica gel were treated with Britton–Robinson buffer solutions at pH values from 2 to 12 for 22 days. Silicon was measured by microwave plasma atomic emission spectrometry. Treatment effects were evaluated on longitudinal cuts of needles under a stereomicroscope and on phytolith assemblages from needles using a light microscope. Surfaces of treated phytoliths were investigated by scanning electron microscope and elemental analysis of phytoliths was determined by energy dispersive X-ray fluorescence. Dissolution of silicon in spruce needles was inhibited between pH 8.0 and 11.1. Needle tissue protects phytoliths from erosion processes at this alkaline pH range. Most dissolved silicon appeared to originate from the phytolith surfaces and the silica matrix of the apoplast in the tissues, with less from complete dissolution of phytoliths. Our experiment suggests that extraneous metal elements are incorporated into the silica structure during the dissolution process. Thus, higher element content is an effect of partial dissolution rather than a cause of dissolution. Ultrastructure of the surface of Picea-blocky type phytoliths, namely disappearance of the globular structure, may be useful to assess the intensity of destructive processes in sediments. Our experimental treatments indicate that characteristic Picea-blocky phytoliths in needles can be well-preserved, depending on circumstances in sediments. Further micro-analytical measurements will make these needles promising tools for paleoenvironmental reconstructions.

Scalable Superomniphobic Surfaces

Superomniphobic surfaces that repel liquids of extremely low surface tension rely on carefully fabricated doubly re-entrant topographies, typically made by silicon deep reactive ion etching technology. However, previously published processes have depended on critically timed etching steps, which are difficult to downscale. We present a scalable process that eliminates the critically timed etching steps. It is based on the use of silicon-on-insulator wafers and a silicon oxide foot of the micropillar, which makes the isotropic silicon release step non-critical. The process allows easy downscaling of pillars from 20 $\mu \text{m}$ to 10 $\mu \text{m}$ and $5~\mu \text{m}$ . The downscaling increases the stability of the Cassie state. Based on the process, we are able to create superomniphobic surfaces that sustain perfluorohexane (FC-72), which has the lowest surface tension of the known liquids at room temperature ( $\gamma _{\text {lv}}=11.91$ mN/m at 20 °C), in the Cassie state at droplet diameters down to 200 micrometers. These are the smallest perfluorohexane droplets repelled to date. [2019-0207]

Ni/4H-SiC interaction and silicide formation under excimer laser annealing for ohmic contact

Nickel silicidation reactions were activated on 4H-SiC using laser annealing at wavelength of 308 nm to study interaction and reaction of the involved atomic species. With this intent, the deposited nickel layer thickness was scaled from 100 nm to 10 nm and the laser fluence was spanned from 2.2 to 4.2 J/cm2. A combination of structural characterization by X-ray diffraction, Energy-Dispersive X-ray spectroscopy, Raman Spectroscopy, Transmission Electron Microscopy and morphological investigations through Scanning Electron Microscopy with theoretical predictions as a function of the applied laser fluence, have unveiled that the starting nickel thickness plays a main role, especially above the threshold for nickel melting (2.8 J/cm2). As a general paradigm, sufficient silicon release from the substrate occurs above this threshold that is available for silicidation, with amount increasing with the laser fluence. This addresses stoichiometry and morphology of the silicided contact that indeed depend on the available Nickel atoms (i.e., the Ni layer thickness) and on the thermal profile, as tested at a fixed fluence of 3.8 J/cm2. In addition, a layer-by-layer variable stoichiometry is established in each sample through the contact, with the deepest silicide being relatively more Si-rich. All those findings have impact on the electrical parameters of testing diodes. Based on data cross-linking, NiSi2 contacting layers and C-free interfaces provide a convenience in reducing resistance contributions.

Osteogenic differentiation of mesenchymal stem cells on hybrid coatings sterilized by different processes

Abstract

&lt;p&gt;Ion release of chitosan and nanodiamond modified glass ionomer restorative cements&lt;/p&gt;

PurposeIon release from glass ionomer restorative cements (GICs) plays an important role in GICs. The ion release from chitosan and nanodiamond-modified glass ionomers was assessed.Materials and methodsThree GICs (Fuji IX, Ketac Universal and Riva Self Cure) were modified in the powder phase per weight by adding 5% or 10% of a commercially available chitosan powder (CH) or nanodiamond (ND) powder to the GICs. The specimens with dimensions 4 mm diameter and 6 mm height manufactured from the 15 GIC formulations were allowed to set for 1 hr and subsequently placed in neutral de-ionised water. The released ions were assessed using inductively coupled plasma-mass spectrometer (ICP-MS) to determine the elemental release. Additionally, three different disc-shaped specimens (3 mm in diameter and 1 mm thick) were constructed from each material for scanning electron microscopy (SEM) and energy dispersive X-ray spectrometry (SEM-EDS) microanalysis to establish an ion weight percentage.ResultsThere were no significant differences in the ion release between the control materials for aluminium, silicon and strontium. The ion release from CH and most ND-modified GICs were significantly (p<0.00001) increased compared to the control materials. CH modifications significantly increased the ion release of aluminium, sodium, silicon and strontium for all three control materials (with the exception of the strontium release from Ketac Universal that was modified with 5% chitosan).ConclusionIon release can be advantageous to tooth structure due to the interaction of chitosan with the GIC chemistry and moisture during maturation. Ion release up to five times greater than the control was noted for some ions.

Rapid Regeneration of Vascularized Bone by Nanofabricated Amorphous Silicon Oxynitrophosphide (SiONP) Overlays.

Fracture healing is a complex biological process. Severe bone loss and ischemia from traumatic fractures lead to inflammation and accumulation of damaging reactive oxygen species (ROS). Fixative devices that not only provide mechanical support but also stimulate antioxidants such as superoxide dismutase (SOD1) and influence signaling pathways for extracellular matrix (ECM) mineralization, are critical for normal healing of such fractures. In this study, we report a novel biomaterial, silicon oxynitrophosphide (SiONP) that provides sustained release of ionic silicon (Si+4) and phosphorous (P) over few weeks under physiological conditions. Anti-oxidant role of Si+4 and augmented ECM mineralization by P ions lead to enhanced osteogenesis coupled with quick revascularization for rapid bone regeneration. Plasma enhanced chemical vapor deposition (PECVD) provided a conformal, well adherent and highly reproducible surface chemistry overlaid onto nanofabricated bioinspired surfaces. The Nitrogen to P and O content ratio was observed to change the dissolution rate and the release kinetics of the overlaid film. The SiONP films with optimal release kinetics promoted anti-oxidant expression via enhanced SOD1, which downstream upregulated other osteogenic markers with MC3T3-E1 cells. These surfaces also promoted angiogenesis evident by formation of thicker tubules by Human umbilical vein endothelial cells (HUVEC). In-vivo evaluation using a rat critical-sized calvarial defect model showed rapid bone-regeneration for these nanofabricated biomaterials as compared to control groups, and opens new horizon for future clinical trials of new antioxidant materials on biomedical devices that can reduce healing time, lower medical care cost, and increase the quality of newly formed bone in critical size defects.

Fabrication of Si@AP/NC metastable intermixed nanocomposites (MICs) by electrospray method and their thermal reactivity

In order to enhance the heat release of nanoparticles silicon, the Si@AP/NC metastable intermixed composites (MICs) Si@AP/NC with varied content of silicon (40%, 60%, and 80%) were designed and prepared by electrospray. Observation by scanning electron microscopy (SEM) has shown that the morphological characterization of those composites was homogeneously mixed. The thermal properties of those MICs were evaluated by means of DSC-TG techniques. Results show that the low- and high-temperature decomposition of AP transitioned from two separated stages to a one-step process. This was mainly caused by the interaction of thin silica on the surface of silicon and perchloric acid. The dependence of activation energy on the conversation rate was obtained by making use of state-of-the-art kinetic procedures. It has been found that decomposition of Si@NC/AP-40 and Si@NC/AP-60 followed the random chain scission model. With the strengthening of active centers of silica, the mechanism of proton migration of AP turned into the growth of the nucleus. The decomposition process of AP started on the surface of the crystal and gradually decomposed steadily as AP decomposition proceeded. Therefore, it is a first-order reaction model for Si@NC/AP-60 and Si@NC/AP-80 in their second-step reaction. Overall, manufacture spherical Si-NPs composites wrapped in polymer though electrostatic spray technology, a novel way of preparing nanoenergetic materials was created. These nanocomposites could be applied normally as fuels in thermobaric explosives or solid propellants.

Characterization of Leachates from 6 Root Canal Sealers

IntroductionThe aim of this study was to evaluate 6 different endodontic sealers by characterizing their leachates and comparing their solubility in water over a 4-week period. MethodsThe solubility of each sealer (Apexit Plus [Ivoclar Vivadent AG, Schaan, Liechtenstein], MTA Fillapex [Angelus Dental, Londrina, Brazil], AH Plus [Dentsply DeTrey, Konstanz, Germany], BioRoot RCS [Septodont, Saint-Maur-des-Fossés, France], Total Fill [FKG Dentaire SA, La Chaux-de-Fonds, Switzerland], and Obturys [Itena, Paris, France]) was tested according to the ISO specification 6876:2012 over a 4-week period. Residues were chemically analyzed using energy-dispersive X-ray spectroscopy. Solubility was analyzed using 2-way analysis of variance and elution with 1-way analysis of variance (P < .05). ResultsAt 24 hours, the solubility of the tested sealers was as follows: AH Plus, 0.0%; Obturys, 0.2%; Apexit Plus, 0.2%; Fillapex, 1.8%; Total Fill, 9.4%; and BioRoot RCS, 13.1%. BioRoot RCS was significantly more soluble than the other sealers, apart from Total Fill (P < .05). After 1 week, the solubility of Total Fill increased to 11.2%, significantly exceeding the solubility of AH Plus, Obturys, and Apexit Plus. After 2 weeks, MTA Fillapex (10.9%) was significantly more soluble than AH Plus, Obturys, and Apexit Plus. High levels of calcium were released from BioRoot RCS, Apexit Plus, MTA Fillapex, and Total Fill. AH Plus released mainly sodium and lanthanum, and Obturys showed an increase of silicon release over time. ConclusionsAll sealers met ISO 6876:2012 regarding solubility (limit <3% at 24 hours) with the exception of Total Fill and BioRoot RCS. MTA Fillapex exceeded the limit after 1 week. High levels of calcium were released from all materials, except from the epoxy resin-based sealers.