Mechanochemical and Low‐Temperature Synthesis of Nanocrystalline Fluorohydroxyapatite/Fluorapatite

Low‐temperature synthesis of fluorapatite/fluorohydroxyapatite with precursor mixture previously mechanochemically treated is described in this article. Ethylene vinylacetate/versatate copolymer as a surface active substance was mechanically treated to obtain a core‐shell system with strongly controlled grain size. Despite usual behavior of mechanically activated systems, only an amorphous phase formed from precursor ions present in the mixture composed of β‐Ca₂P₂O₇, CaCO₃, CaF₂, and unreacted Ca(OH)₂ was obtained during milling for 5 min to 8 h. The mixture contained depots of labile F^? ions conserved in micelles cages, which are useful for teeth protection from carries. For transformation of these amorphous phases into fluorapatite, an additional low thermal treatment was necessary. The mechanism of the precursor mixture transformation into fluorapatite during milling and thermal treatment was investigated using FTIR spectroscopy and X‐ray diffraction. The morphology and size distribution of the obtained powders was studied using SEM and TEM.     

Modelling and experimental investigations of thin filmsof Mg phosphorus‐doped tungsten bronzes obtainedby ultrasonic spray pyrolysis

In this study, the synthesis of thin films of Mg phosphorus doped tungsten bronzes (MgPTB; MgHPW₁₂O₄₀·29H₂O) by the self‐assembly of nano‐structured particles of MgPTB obtained using the ultrasonic spray pyrolysis method was investigated. As the precursor, MgPTB, prepared by the ionic exchange method, was used. Nano‐structured particles of MgPTB were obtained using the ultrasonic spray pyrolysis method. The nano‐structure of the particles used as the building blocks in the MgPTB thin film were investigated experimentally and theoretically, applying the model given in this article. The obtained data for the mean particle size and their size distribution show a high degree of agreement. These previously tailored particles used for the preparation of thin films during the next synthesis step, by their self‐assembly over slow deposition on a silica glass substrate, show how it is possible to create thin MgPTB films under advance projected conditions of the applied physical fields with a fully determined nanostructure of their building block particles, with a relatively small roughness and unique physical properties.     

Biomimetic deposition of hydroxyapatite on the surface of silica thin film covered steel tape

The biomimetic deposition of hydroxyapatite (HA) on the surface of SiO₂ thin film coated metal substrates was developed and investigated.     

Influence of hydroxyapatite pore geometry on tigecycline release kinetics

Calcium hydroxyapatite (CHA), as one of the most important ceramic materials in bone tissue engineering, was used as a delivery system for tigecycline, a potential antibiotic in treatment of osteomyelitis. Tigecycline, in a solid state, was mixed with CHA powder and the obtained mixture was compressed into tablets. The release of tigecycline from these tablets in a pH 7.4 phosphate-buffered saline solution was measured by a UV–vis spectrophotometer at 37 °C. The total dose of tigecycline was released for 5 to 30 days, depending on the applied pressure and drug concentration. A new drug release mechanism that determines the relationship between pore sizes and drug release rate is proposed. It explains and quantifies the drug release kinetics based on pore sizes and pore size distribution.     

Designing of Copper Nanoparticle Size Formed via Aerosol Pyrolysis

In this article, the synthesis and structural design of spherical, nonagglomerated particles of copper powder, synthesized by ultrasonic atomization of copper sulfate solutions in hydrogen atmosphere at 1173?K (900?°C), was investigated. Well-controlled particle sizes of Cu powders were obtained from precursor solutions of various concentrations. The mean particle diameters and the ranges of particle size distribution were investigated by scanning electron microscopy (SEM). The diameter values of Cu particles obtained experimentally and estimated theoretically, using the most frequently applied atomization models, were compared. Special attention was paid to our break up capillary waves model, described elsewhere and significantly advanced by Jokanovi???s theoretical approach, which was applied for the first time to a copper metal system as described in this article. The best agreement between the calculated and the experimentally obtained values was found using this model.     

Synthesis of TTCP by using inverse micelle method

Tetracalcium phosphate (TTCP, Ca₄(PO₄)₂O) is one of the major powder components of self-setting orthopedic and dental cements. Traditionally, TTCP powders are produced by a solid-state reaction of Ca- and P-containing precursors between 1350 and 1500 °C. Such procedures require expensive high-temperature furnaces and subsequent grinding of sintered particles. Grinding not only leads to the contamination but also alters the structure of TTCP, thereby reducing its bioactivity. The present paper offers an innovative approach to the inverse micelle method of TTCP synthesis, with a subsequent thermal treatment to obtain purer TTCP phase. The obtained powder was a mixture of TTCP and octacalcium phosphate (OCP) phases for thermally untreated sample, while for the sample thermally treated at 800 °C it was a mixture of TTCP and β-TCP phases. The TTCP phase was prevailing phase in both cases. A typical shape of TTCP nanoparticles was needle-like. Somewhere, needles are joined together forming platelet-like structures. Investigations of the obtained phases were made by XRD and TEM. The mechanism of chemical synthesis and structural arrangements of the obtained phases were particularly investigated.     

Synthesis and Properties of a New Dental Material Based on Nano‐Structured Highly Active Calcium Silicates and Calcium Carbonates

A synthesis of a new dental material, based on nano‐structured highly active calcium silicates and calcium carbonates, is described in this paper. Phase analysis of this material, before and after hydration, was performed by X‐ray diffraction and showed that active silicate phases were transformed into tobermorite phase, while carbonates remained unchanged. The mechanism of hydration was fully described. The morphology of the sample was studied by SEM, and typical appearance of the present phases was particularly discussed. The mechanical properties and setting time of this material make it very promising for potential application in dental practice.     

Hydroxyapatite coatings prepared by a high power laminar plasma jet

For two hydroxyapatite (HA) powders, containing particles differing in mass by a factor of 20, a set of optimum deposition parameters was defined, leading to the coatings with high crystallinity (80-90%), high adhesion strength (60 and 40 MPa for the coating thicknesses of 120 μm and 350 μm, respectively) and excellent microstructure (coatings were without micro- or macro-cracks, without delaminating on substrate-coating surface contact, and possess low porosity, 1-2%). It was shown that higher plasma power (52 kW) did not necessarily lead to a higher HA decomposition.     

Biocompatibility Study of a New Dental Cement Based on Hydroxyapatite and Calcium Silicates: Focus on Liver,Kidney, and Spleen Tissue Effects

The effects of a new material based on hydroxyapatite and calcium silicates, named ALBO-MPCA, were investigated on the liver, kidney and spleen. The material was administrated orally for 120 days in an in vivo model in Wistar rats, and untreated animals served as a control. Hematological and biochemical blood parameters were analyzed. Qualitative histological analysis of tissues, change in mitotic activity of cells, and histological characteristics was conducted, as well as quantitative stereological analysis of parenchymal cells, blood sinusoids, and connective tissues. Additionally, the protein expressions of Ki67 and CD68 markers were evaluated. Histological analysis revealed no pathological changes after the tested period. It showed the preservation of the architecture of blood sinusoids and epithelial cells and the presence of mitosis. Additionally, the significantly increased number of the Ki67 in the presence of ALBO-MPCA confirmed the proliferative effect of the material noticed by stereological analysis, while immunoreactive CD68 positive cells did not differ between groups. The study showed non-toxicity of the tested material based on the effects on the hematological, biochemical, and observed histological parameters; in addition, it showed evidence of its biocompatibility. These results could be the basis for further steps toward the application of tested materials in endodontics.     

Optical properties of titanium oxide films obtained by cathodic arc plasma deposition

Structural and optical properties of nanometric titanium oxide(TixOy) films obtained by cathodic arc plasma deposition were investigated. Phase analysis by x-ray diffraction and Fouriertransform infrared spectroscopy showed the presence of anatase, rutile, Ti_2O_3, Ti_4O_7 and amorphous phases. Scanning electron microscopy images showed well-developed surface morphology with nano-patterns. Spectroscopic ellipsometry revealed film thicknesses of 53 and50 nm, variable refractive indices dependent on the light wavelength and close to zero extinction coefficients for wavelengths higher than 500 nm. On the basis of ultraviolet–visible spectroscopy data and using the Tauc equation, band gap values for direct and indirect electron transitions were determined.