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Hard dental tissue pathologies, such as caries, are conventionally managed through replacement by tooth-colored inert biomaterials. Tissue engineering provides novel treatment approaches to regenerate lost dental tissues based on bioactive materials and/or signaling molecules. While regeneration in the form of reparative dentin (osteo-dentin) is feasible, the recapitulation of the tubular microstructure of ortho-dentin and its special features is sidelined. This study characterized in vitro , and in vivo human EDTA-treated, freeze-dried dentin matrices (HTFD scaffolds) conditioned with calcium phosphate nanoparticles (NPs) bearing plasmids encoding dentinogenesis-inducing factors (pBMP2/NPs or pDMP1/NPs). The uptake and transfection efficiency of the synthesized NPs on dental pulp stem cells (DPSCs) increased in a concentration- and time-dependent manner, as evaluated qualitatively by confocal laser microscopy and transmission electron microscopy, and quantitatively by flow cytometry, while, in parallel, cell viability decreased. HTFD scaffolds conditioned with the optimal transfectability-to-viability concentration at 4 µg Ca/mL of each of the pBMP2/NPs or pDMP1/NPs preserved high levels of cell viability, evidenced by live/dead staining in vitro and caused no adverse reactions after implantation on C57BL6 mice in vivo. HTFD/NPs constructs induced rapid and pronounced odontogenic shift of the DPSCs, as evidenced by relevant gene expression patterns of RunX2, ALP, BGLAP, BMP-2, DMP-1, DSPP by real-time PCR, and acquirement of polarized meta-mitotic phenotype with cellular protrusions entering the dentinal tubules as visualized by scanning electron microscopy. Taken together, HTFD/NPs constitute a promising tool for customized reconstruction of the ortho-dentin/odontoblastic layer barrier and preservation of pulp vitality. In clinical dentistry, the most common therapeutic approach for the reconstruction of hard dental tissue defects is the replacement by resin-based restorative materials. Even modern bioactive materials focus on reparative dentinogenesis, leading to amorphous dentin-bridge formation in proximity to the pulp. Therefore, the natural microarchitecture of tubular ortho-dentin is not recapitulated, and the sensory and defensive role of odontoblasts is sidelined. This study approaches the reconstruction at the dentin-pulp interface using a construct of human treated dentin (HTFD) scaffold and plasmid-carrying nanoparticles (NPs) encoding dentinogenic factors (DMP-1 or BMP-2) with excellent in vitro and in vivo properties. As a future perspective, the HTFD/NPs constructs could act as bio-fillings for personalized reconstruction of the dentin-pulp interface. [Display omitted] [ABSTRACT FROM AUTHOR]

The potential of x-ray powder diffraction to analyze the size and ultrastructure of metallic nanoparticles (silver, gold, silver-gold alloy, and calcium phosphate) is demonstrated. By the Rietveld analysis, it is possible to estimate the crystallite size for such nanoparticles, even if they are very small (4 nm), using the effect of peak broadening in small crystallites. The results correspond well to crystallite size as determined by transmission electron microscopy (TEM), also confirming the twinned nature of the metallic nanoparticles. For calcium phosphate nanorods which are not twinned, the results by x-ray powder diffraction and TEM are in good agreement. [ABSTRACT FROM AUTHOR]

Regularities of the formation of calcium phosphate coatings on the surface of titanium and zirconium alloys formed by the method of microarc oxidation are investigated. The scheme of deposition of the calcium phosphate coating in microarc discharges is suggested that explains the difference in the morphology, microstructure, and properties of coatings on the surface of titanium and zirconium alloys. It is demonstrated that coatings on the surface of titanium and zirconium alloys have different structures, phase compositions, and physicomechanical properties due to different electrophysical characteristics of metal (titanium and zirconium) substrates, disperse β-Nb particles, and passivating oxide films on their surfaces. [ABSTRACT FROM AUTHOR]

Results are presented of studies of the physical-mechanical properties of silver-doped calcium phosphate coatings formed by radio-frequency magnetron sputtering on a surface of technically pure VT1-0 titanium and 12Cr18Ni10Ti stainless chromium-nickel surgical steel. The films have the nanocrystalline structure of hydroxyapatite with mean diameter of the coherently diffracting domains equal to 20-30 nm. It has been established that the configuration of the magnetic field of the magnetron has an effect on the roughness, thickness, and refractive index of the coatings. The thickness of the coatings and the refractive index vary within the ranges 300-700 nm and 1.68-1.80, respectively. The nanohardness of the coatings is within the range 4-7GPa, the modulus of elasticity of the coatings depends on the material of the substrate and is equal to 130-150 GPa for titanium and 170-200 GPa for steel. Sclerometric measurements of the coatings made it possible to establish a high adhesion strength of the coatings. [ABSTRACT FROM AUTHOR]

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Abstract: Thin calcium phosphate coatings with a thickness of 0.09 to 2.7 µm were prepared by radio-frequency magnetron sputtering deposition on NiTi and Ti substrates at a substrate temperature of 500 °C in argon atmosphere. Scanning electron microscopy (SEM) showed that the surface structure is uniform and dense without visible defects (pores and microcracks). Rutherford backscattering spectroscopy (RBS) and energy-dispersive X-ray spectroscopy (EDX) confirmed that the coating contains calcium, phosphorus, and oxygen with a uniform composition. Crystallographically, the coating consists of crystalline hydroxyapatite which is also supported by infrared spectroscopy. The mechanical characteristics of the coating were measured by nanoindentation (Vickers indenter), giving a nanohardness of 10 GPa and a Young''s modulus of 110 GPa. The strength of adhesion of the calcium phosphate coating to the metallic substrates depended on the coating''s thickness and decreased for a thickness larger than 1.6 µm. No difference was observed between NiTi and Ti substrates. [Copyright &y& Elsevier]