Morphology and Structure of TiO2 Nanotube/Carbon Nanostructure Coatings on Titanium Surfaces for Potential Biomedical Application.

Titanium is the most used material for implant production. To increase its biocompatibility, continuous research on new coatings has been performed by the scientific community. The aim of the present paper is to prepare new coatings on the surfaces of the pure Ti Grade 2 and the Ti6Al4V alloy. Three types of coatings were achieved by applying anodization and chemical vapor deposition (CVD) methods: TiO2 nanotubes (TNTs) were formed by anodization, carbon nanotubes (CNTs) were obtained through a metal-catalyst-free CVD process, and a bilayer coating (TiO2 nanotubes/carbon nanostructures) was prepared via successive anodization and CVD processes. The morphology and structure of the newly developed coatings were characterized using SEM, EDX, AFM, XRD, and Raman spectroscopy. It was found that after anodization, the morphology of the TiO2 layer on pure Ti consisted of a "sponge-like" structure, nanotubes, and nano-rods, while the TNTs layer on the Ti alloy comprised mainly nanotubes. The bilayer coatings on both materials demonstrated different morphologies: the pure Ti metal was covered by a layer of nanotubular and nano-rod TiO2 structures, followed by a dense carbon layer decorated with carbon nanoflakes, and on the Ti alloy, first, a TNTs layer was formed, and then carbon nano-rods were deposited using the CVD method.

3D Printing, Histological, and Radiological Analysis of Nanosilicate-Polysaccharide Composite Hydrogel as a Tissue-Equivalent Material for Complex Biological Bone Phantom.

Nanosilicate-polysaccharide composite hydrogels are a well-studied class of materials in regenerative medicine that combine good 3D printability, staining, and biological properties, making them an excellent candidate material for complex bone scaffolds. The aim of this study was to develop a hydrogel suitable for 3D printing that has biological and radiological properties similar to those of the natural bone and to develop protocols for their histological and radiological analysis. We synthesized a hydrogel based on alginate, methylcellulose, and laponite, then 3D printed it into a series of complex bioscaffolds. The scaffolds were scanned with CT and CBCT scanners and exported as DICOM datasets, then cut into histological slides and stained using standard histological protocols. From the DICOM datasets, the average value of the voxels in Hounsfield Units (HU) was calculated and compared with natural trabecular bone. In the histological sections, we tested the effect of standard histological stains on the hydrogel matrix in the context of future cytological and histological analysis. The results confirmed that an alginate/methylcellulose/laponite-based composite hydrogel can be used for 3D printing of complex high fidelity three-dimensional scaffolds. This opens an avenue for the development of dynamic biological physical phantoms for bone tissue engineering and the development of new CT-based imaging algorithms for the needs of radiology and radiation therapy.

Influence of Factors in the Photopolymerization Process on Dental Composites Microhardness.

The aim of the present paper is to investigate the influence of factors in photopolymerization process that govern microhardness of three types of dental composites-universal (UC), bulk-fill (BC), and flowable (FC). Cylindrical specimens with different thicknesses are made and light cured. The significance of light intensity, irradiation time, and layer thickness on Vickers microhardness is evaluated by experimental design, analysis of variance, and regression analysis. It is found that the main factor influencing the microhardness on the top surface of the three composites is light intensity. The second factor is layer thickness for the UC and FC, while for BC, it is curing time. The third factor is curing time for the first two composites and layer thickness for bulk-fill. The significance of factors' influence on the microhardness of the bottom surface is the same for the UC and FC, but different for BC. The main factor for the first two composites is layer thickness, followed by curing time and light intensity. For bulk-fill, curing time is main factor, light intensity is second, and layer thickness is last. Different significance of factors influencing the microhardness on top and bottom surfaces of investigated composites is revealed for the first time in the present study.

Incorporation of the Dry Blossom Flour of Sambucus nigra L. in the Production of Sponge Cakes.

The present study aims to develop recipe compositions and technology for producing sponge cakes from wholemeal flour, partially replaced with a functional plant component dry blossom flour of Sambucus nigra L. Three designs of sponge cakes with 5, 10, and 15% content of flour of Sambucus nigra L. corrected up to 100% with whole-grain oat flour were studied. Their characteristics were compared with sponge cakes of 100% wheat flour/control. The obtained new products were characterized by reduced carbohydrates, increased content of dietary fiber, and preserved volume compared to the control. The physicochemical parameters of sponge cake and marshmallows with different concentrations of dry flowers of Sambucus nigra L. included in them differed from the control with lower water absorption, pH, and moisture, while having a higher relative mass and ash content and retaining the original size. Pathogenic microorganisms such as Escherichia coli, Salmonella sp., and Staphylococcus aureus, and common coliforms were not detected in the control and experimental samples when determining the microbiological parameters. Therefore, the developed formulations are an excellent alternative to wheat flour, significantly improving some nutritional characteristics such as smell, taste, dietary fiber, and lower carbohydrate content.

Finite element analysis of V-shaped tooth defects filled with universal nanohybrid composite using incremental technique.

The aim of the present paper is to study the stresses and strains in fillings of V-shaped tooth defects made of universal photo-cured nanohybrid composite (UPC) using incremental technique. Numerical modeling with FEA and microleakage test are performed. Inhomogeneous distribution of the equivalent Von Mises stresses after polymerization of the two UPC layers is found, as the maximal value after polymerization of the first layer is 1.5 times lower compared to that of second one. In the first layer, maximum stresses are concentrated on dentin surface in cervical region of the obturation border and in occlusal region of the obturation volume. In the second layer, maximum stresses are generated in cervical area of the obturation volume and on dentin surface occlusally along the obturation border. The displacement after polymerization of each layer is inhomogeneous, as its values are more than 2 times smaller compared to that in fillings of glass-ionomer cement and flowable composite. In the first layer, the displacement is maximal on surface in the cervical region, while in the second layer it is maximal on surface occlusal of the obturation. The adequacy of the model used is confirmed by the microleakage test results. It is proven that UPC is better choice for filling of V-shaped defects due to the lower microleakage.

Application of analytical methodology in parametric analysis of the stress state in a coating-substrate system based on dental materials.

The aim of the present paper is to use analytical methodology by 2D shear-lag model in parametric analysis of the normal stress in the coating. The tension of a substrate with coatings on its top and bottom surfaces is considered. The parametric study is performed by varying coating thickness and elastic properties both the coating and the substrate. The calculations are done for different groups of dental materials - polyetheretherketone, dental resin composite and porcelain as a coating material and high gold, palladium and Co-Cr alloys as a substrate material. It is established that the coating thickness strongly influences the normal stresses parallel to the loading axis - its increasing leads to decreasing of normal stresses in the coating. However, the increase of the coating thickness results in negligible increase of the additional normal stresses (perpendicular to the loading axis) in the central part of the coating. Young's modulus of the coating considerably influences the normal stresses parallel to the loading axis, while its influence on the additional normal stresses appears mainly in the zones near the free edge of the coating. The increase of the modulus of elasticity of the coating causes increase of the both normal stresses. The increasing of Young's modulus of the substrate insignificantly influences on the both normal stress in the coating. It is found that: 1) the lowest normal stresses are generated in the porcelain layer with the largest thickness of 2.0 mm; 2) the porcelain is characterized with the highest normal stresses compared to the polymer and composite coating materials; 3) the alloy type of the substrate has negligible effect on both the normal stress in the porcelain coating. The results are validated by tensile test of Co-Cr dental alloy specimens coated with porcelain. A good agreement is found between the analytical approach and the failure behaviour of the porcelain coating. Therefore, the proposed analytical model can be used as a tool to study the stress state in the coating under tensile test of coated flat specimens.