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Abstract Preheating of dental composites enhances their flowability and can improve marginal adaptation and decrease voids leading to more successful restorations. The aim of this research is to study the influence of preheating temperature on the rheological properties of four contemporary nanohybrid dental resin composites. The rheological measurements on the four preheated nanohybrid resin-based composites [Herculite Ultra (Kerr), Tetric EvoCeram (Ivoclar Vivadent), Filtek Supreme Ultra (3 M) and Grandio (Voco)] were conducted utilizing a parallel-plate shear rheometer. The composites were placed on the lower plate, and the upper plate was lowered until it gently touched the surface of the sample at a gap distance of 0.5 mm. Measurements were obtained at three different temperatures 25, 37 and 60 °C. The shear rate varied linearly in ramp mode from 0.1 to 10 s− 1. All dental resin composites tested in this research showed a significant reduction in shear viscosity with increasing temperature. Additionally, all dental resin composites were pseudoplastic, indicating a disproportionate reduction in complex viscosity (η*) with enhancing frequency (shear rate; shear-thinning effects). There is a variation in shear modulus of elasticity (G′) between the four contemporary nanohybrid dental resin composites at low shear rates. Preheating the composite material resulted in enhanced flow and greater adaptability, as evident by decreasing G' values with increasing shear rate which did not occur with samples that were not preheated. The results demonstrated that regardless of the resin composite material, it was found that preheating the nanohybrid dental composites considerably improves their flowability and can improve clinical placement and adaptation. Finally, the obtained results could be employed as a guideline for material behavior to form the desired consistency or compare commercially available preheating devices. Highlights • Preheating the nanohybrid dental composites considerably improves their flowability. • The elastic component of shear modulus decreases with increasing shear strain in the range of 0.1%–10%. • The G′ increases after preheating, even when the material is cooled. • The G′ decreases with increasing shear rate after the material is heated. • There is a variation in G′ between brands at low shear rates. [ABSTRACT FROM AUTHOR]

In this research, a systematic study has been directed to evaluate epoxy matrix nanocomposite performance of Al 2 O 3 nanoparticles incorporated into epoxy resin. An ultrasonic mixing process was utilized to achieve homogenous dispersion of these nanoparticles into epoxy resin. Several mechanical and tribological tests, such as three-point bending test, Izod impact test and pin on ring wear test, were performed to examine mechanical properties and wear performance of epoxy-Al 2 O 3 nanocomposites. Nanocomposites displayed increased bending strength and impact strength due to the incorporation of Al 2 O 3 nanoparticles. In addition, introduction of Al 2 O 3 nanoparticles into epoxy resin matrix at low values resulted in significant reduction of wear rate and coefficient of friction. Such effects could be attributed to dispersion of Al 2 O 3 nanoparticles into epoxy matrix and loading. The influences of the Al 2 O 3 nanoparticle incorporation into epoxy matrix resin are further described in terms of reinforcing methods. [ABSTRACT FROM AUTHOR]

Objective Vascularization is a critical process during bone regeneration/repair and the lack of tissue vascularization is recognized as a major challenge in applying bone tissue engineering methods for cranial and maxillofacial surgeries. The aim of our study is to fabricate a vascular endothelial growth factor (VEGF)-loaded gelatin/alginate/β-TCP composite scaffold by 3D printing method using a computer-assisted design (CAD) model. Methods The paste, composed of (VEGF-loaded PLGA)-containing gelatin/alginate/β-TCP in water, was loaded into standard Nordson cartridges and promptly employed for printing the scaffolds. Rheological characterization of various gelatin/alginate/β-TCP formulations led to an optimized paste as a printable bioink at room temperature. Results The in vitro release kinetics of the loaded VEGF revealed that the designed scaffolds fulfill the bioavailability of VEGF required for vascularization in the early stages of tissue regeneration. The results were confirmed by two times increment of proliferation of human umbilical vein endothelial cells (HUVECs) seeded on the scaffolds after 10 days. The compressive modulus of the scaffolds, 98 ± 11 MPa, was found to be in the range of cancellous bone suggesting their potential application for craniofacial tissue engineering. Osteoblast culture on the scaffolds showed that the construct supports cell viability, adhesion and proliferation. It was found that the ALP activity increased over 50% using VEGF-loaded scaffolds after 2 weeks of culture. Significance The 3D printed gelatin/alginate/β-TCP scaffold with slow releasing of VEGF can be considered as a potential candidate for regeneration of craniofacial defects. [ABSTRACT FROM AUTHOR]

The objective of this study was to evaluate the effect of the addition of synthesized hydroxyapatite (HA) and fluorapatite (FA) nanoparticles to a glass-ionomer cement (GIC) on the mechanical properties, while preserving their unique and potent clinical properties. Bioceramics, such as HA and FA, have been recognized as restorative materials (e.g. GICs) in dentistry due to their chemical and biological compatibility with human hard tissues, which are considered calcium phosphate complexes. In this study, both of these inorganic nanoparticles (HA and FA) were synthesized via a wet-chemical precipitation method. The obtained nanoparticles were characterized with X-ray diffraction (XRD), inductively coupled plasma atomic emission spectroscopy (ICP-AES), Fourier transformed infrared spectroscopy (FTIR), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Brunauer-Emmett-Teller (BET) Theory. Then, HA and FA were incorporated into the powder component of the resin-modified cement (Fuji II, GC gold label, GC international, Tokyo, Japan) at 5% and 8 wt%, and unblended powder was employed as control. Compressive strength (CS) and diametral tensile strength (DTA) before and after 1, 7 and 28 days of storage in distilled water were evaluated using a universal testing machine. Surface microhardness after 1 and 7 days of storage in distilled water was determined using Vickers microhardness tester. Setting and working time was measured as specified in the ASTM standard. The surface morphology of the modified GICs was examined using SEM observations. The morphology of the synthesized HA and FA nanoparticles was hexagonal, and their average sizes were about 25 nm and 30 nm, respectively. The mechanical results of the modified GICs ascertained addition of HA and FA (5 and 8 wt%) into the glass ionomer cement after 7 days of storage in distilled water exhibited statistically higher CS of about 107–113.6 MPa and 111–117.8 MPa, respectively, and also higher DTS, 13–16 MPa and 14–19 MPa, respectively. The hardness of the glass ionomers containing HA and FA nanoparticles (5 wt%) were increased by 2.21% and 11.77%, respectively. In addition, working time and setting time by adding the 5% nanoparticles were reduced about 8.5% and 13.23% for HA and 10.63% and 19.11% for FA, respectively. It was concluded that glass ionomer cements containing nanobioceramics (HA and FA) are promising restorative dental materials with improved mechanical properties. These experimental GICs may be potentially employed for higher stress-bearing site restorations, such as Class I and II restorations. [ABSTRACT FROM AUTHOR]

Abstract: A novel nanostructure pigment of Eu2+ doped SrMgAl2SiO7 was prepared via the sol–gel route. The phase composition and condition of crystallites during heating were characterized by X-ray diffraction (XRD) analysis. Investigation of optical properties by spectrophotometer illustrated that under short ultraviolet excitation wavelength, the main emission peak occurred at about 415–420nm. Also, relatively pure purplish blue color was observed that can be ascribed to the 4f65d1(2D)→4f7(8S7/2) transition of Eu2+. The effect of calcination temperature on the luminescence properties of the phosphors was evaluated and, also in this case, scanning electron microscope (SEM) was employed. From colorimetry results, color coordinations of phosphor shift towards the deep blue region as calcination temperature increases. Finally, grain size of products at optimum calcination temperature was estimated to be about 20–30nm using Scherrer’s equation, which was consistent with transmission electron microscopy (TEM) observations. [Copyright &y& Elsevier]

Abstract: Bioactive glass of the type CaO–P2O5–SiO2 was obtained by the sol–gel processing method. The obtained material was characterized by X-ray powder diffraction (XRD). Composite samples of hydroxyapatite with synthesized bioglass were prepared at 1000°C and characterized by XRD, Fourier transform infrared spectroscopy (FTIR), and surface electron microscopy (SEM). The bioactivity was examined in vitro with respect to the ability of hydroxyapatite layer to form on the surface as a result of contact with simulated body fluid (SBF). XRD, FTIR and SEM studies were conducted before and after contact of the material with SBF. It could be detected that the bioglass was crystallized partly. Furthermore, silicated hydroxyapatite may have formed due to the diffusion of silicate groups to the apatite phase and these may have substituted for the phosphate groups. It can be concluded from SEM and FTIR results that apatite phase formed after 14 days in SBF. [Copyright &y& Elsevier]

Abstract: The preparation of thin films of CdS by chemical bath deposition is mostly based on the utilisation of ammonia as a complexing agent for cadmium ions. Here we report on a technique based on sodium citrate dihydrate that eliminates the problems of ammonia volatility and toxicity. The crystallites with a size range of 10–20 nm in diameter with zinc blend (cubic) and wurtzite (hexagonal) crystal structures and strong photoluminescence were prepared from the mixture solutions of: cadmium chloride dihydrate as a cadmium source, thiourea as a sulfur source and sodium citrate dihydrate as a complexing agent for cadmium ions. The well-cleaned glass used as a substrate for thin film deposition. The obtained samples were characterized by the techniques such as transmission electron microscopy (TEM), X-ray diffraction (XRD), atomic force microscope (AFM) and fluorescence spectroscopy. Also, the effect of two operating conditions, (i) pH, and (ii) the temperature of reaction on the synthesizing of CdS nanocrystals was examined. Finally, it was found that the CdS nanocrystals showed sharp excitation features and strong ”band-edge” emission. [Copyright &y& Elsevier]

Abstract: To be a suitable biolabeling agent (biosensor), the nanoparticles should have high luminescent efficiency and proper surface groups for coupling with biomolecules. In this article, high-quality ZnS:Mn nanoparticles were synthesized from quaternary W/O micro-emulsion system with different Mn% for detecting the best concentration. The addition of biotin and the subsequent specific binding events alter the dielectric environment of the nanoparticle, resulting in a spectral shift of the particle plasmon resonance. Cyclohexane was used as oil, Triton X-100 as surfactant, n-hexanol as a co-surfactant and mercaptoethanol and thioglycolic acid for the best linking of the biological part to the nanoparticle (as linking agents). Surfactant and co-surfactant produce a stable emulsion with connection to the surface of nanoparticles and prevention from contacting together. For qualitative and quantitative analyses of this product scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDS), inductive coupled plasma (ICP), zeta meter for measurement ZP and spectrograph techniques are used. The results showed that with reducing particle size, emission shifted to the lower wavelengths. In addition, with conjugation between avidin and biotin by mercaptoethanol in biologic media, spectral emission decreased. [Copyright &y& Elsevier]

Abstract: In this study, the synthesis of SiO2–CaO–P2O5–MgO bioactive glass was performed by the sol-gel method. Sol-gel-derived bioglass material was produced both in powder and in discs form by uniaxial pressing, followed by sintering at 700 °C. The obtained material was evaluated by X-ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM), thermal gravimetric analysis (TGA) and differential scanning caloremetry (DSC) analyses. The biocompatibility evaluation of the formed glass was assessed through in vitro cell culture [alkaline phosphatase (AP) activity of osteoblasts] experiments and immersion studies in simulated body fluid (SBF) for different time intervals while monitoring the pH changes and the concentration of calcium, phosphorus and magnesium in the SBF medium. The SEM, XRD and FTIR studies were conducted before and after soaking of the material in SBF. At first, an amorphous calcium phosphate was formed; after 7 days this surface consisted of deposited crystalline apatite. The present investigation also revealed that the sol-gel derived quaternary bioglass system has the ability to support the growth of human fetal osteoblastic cells (hFOB 1.19). Finally, this material proved to be non-toxic and compatible for the proposed work in segmental defects in the goat model in vivo. [Copyright &y& Elsevier]