Bioactive sphene-based ceramic coatings on cpTi substrates for dental implants: An in vitro study

Titanium implant surface modifications have been widely investigated to favor the process of osseointegration. The present work aimed to evaluate the effect of sphene (CaTiSiO5) biocoating, on titanium substrates, on the in vitro osteogenic differentiation of Human Adipose-Derived Stem Cells (hADSCs). Sphene bioceramic coatings were prepared using preceramic polymers and nano-sized active fillers and deposited by spray coating. Scanning Electron Microscopy (SEM) analysis, surface roughness measurements and X-ray diffraction analysis were performed. The chemical stability of the coatings in Tris-HCl solution was investigated. In vitro studies were performed by means of proliferation test of hADSCs seeded on coated and uncoated samples after 21 days. Methyl Thiazolyl-Tetrazolium (MTT) test and immunofluorescent staining with phalloidin confirmed the in vitro biocompatibility of both substrates. In vitro osteogenic differentiation of the cells was evaluated using Alizarin Red S staining and quantification assay and real-time PCR (Polymerase Chain Reaction). When hADSCs were cultured in the presence of Osteogenic Differentiation Medium, a significantly higher accumulation of calcium deposits onto the sphene-coated surfaces than on uncoated controls was detected. Osteogenic differentiation on both samples was confirmed by PCR. The proposed coating seems to be promising for dental and orthopedic implants, in terms of composition and deposition technology

Gel casting of silicon nitride foams using biopolymers as gelling agents

Abstract Si3N4-based foams were prepared by the gel casting route using egg-albumen, agar-agar, or methylcellulose as biopolymer gelling agents. Microstructural, permeability, and mechanical properties of the foams were determined. The use of a variety of environmentally friendly gelling agents produced Si3N4 foams with a wide range of porosity (79–89%), mean cell size (199–852 μm), and mean window size (51–152 μm). The pressureless sintering method was successfully applied and resulted in Si3N4 foams with compressive strengths ranging from 1.6 to 9.4 MPa when treated at 1600 °C and up to 33.5 MPa when sintered at 1700 °C, due to the formation of the β–Si3N4 phase. Darcian (k1) and non-Darcian (k2) permeability coefficients were 4.41 × 10−12 to 1.61 × 10−10 m2 and 5.07 × 10−7 to 1.02 × 10−6 m, respectively, allowing the produced Si3N4 foams to be used in a wide variety of fluid flow and filtering applications

In vitro evaluation of granules obtained from 3D sphene scaffolds and bovine bone grafts: chemical and biological assays

Sphene is an innovative bone graft material. The aim of this study was to investigate and compare the physicochemical and biological properties of Bio-Oss® (BO) and in-lab synthesized and processed sphene granules. BO granules of 1000-2000 μm (BO-L), 250-1000 μm (BO-S) and 100-200 μm (BO-p) for derived granules, and corresponding groups of sphene granules obtained from 3D printed blocks (SB-L, SB-S, SB-p) and foams (SF-L, SF-S and SF-p) were investigated. The following analyses were conducted: morphological analysis, specific surface area and porosity, inductively coupled plasma mass spectrometry (ICP-MS), cytotoxicity assay, Alizarin staining, bone-related gene expression, osteoblast migration and proliferation assays. All pulverized granules exhibited a similar morphology and SF-S resembled natural bone. Sphene-derived granules showed absence of micro- and mesopores and a low specific surface area. ICP-MS revealed a tendency for absorption of Ca and P for all BO samples, while sphene granules demonstrated a release of Ca. No cellular cytotoxicity was detected and osteoblastic phenotype in primary cells was observed, with significantly increased values for SF-L, SF-S, BO-L and BO-p. Further investigations are needed before clinical use can be considered

Spreadability of Metal Powders for Laser-Powder Bed Fusion via Simple Image Processing Steps

This paper investigates the spreadability of the spherical CoCrWMo powder for laser- powder bed fusion (PBF-LB) by using image processing algorithms coded in MATLAB. Besides, it also aims to examine the spreadability dependence with the other characteristics such as powder size distribution, apparent density, angle of repose. Powder blends in four different particle size distributions are prepared, characterized, and spreadability tests are performed with the PBF-LB. The results demonstrate that an increase in fine particle ratio by volume (below 10 µm) enhances the agglomeration and decreases the flowability, causing poor spreadability. These irregularities on the spread layers are quantified with simple illumination invariant analysis. A clear relation between powder spreadability and 3D printed structures properties in terms of residual porosity could not be defined since structural defects in 3D printed parts also depends on other processing parameters such as spatter formation or powder size over layer height ratio

Preliminary investigations on the use of preceramic polymers to produce metal matrix composites, via powder metallurgy techniques

Ceramic-reinforced metal matrix composites were produced by means of preceramic polymers, as precursors for the ceramic phase and powders of the metal alloy. The use of preceramic polymers as precursors for a reinforcing ceramic phase in metallic components represents a well known technique to produce 3d interpenetrating composites . However it was poorly investigated so far, the use of preceramic polymers in powder metallurgy. Only few results were published in the literature, concerning the use of polycarbosilane in Ti or Fe-Cr alloy. In the present work the use of a polysiloxanes (as precursor for a SiOC reinforcing and /or reacting phase) dispersed within a metal matrix is investigated. Powders of alloys of commercial interest (i.e. Al12Si, Ti6Al4V) were investigated and the properties of the produced composites were compared to the pure alloys, produced via a similar technique

Emissivity measurements of opaque gray bodies up to 2000 degrees C by a dual-frequency pyrometer

In the framework of the SPES project at LNL-INFN a method for emissivity measurements by a double-frequency pyrometer in the infrared region at high temperatures on opaque gray bodies of SiC and graphite is presented. The measurement method proposed in this work reveals a good fitting with literature values. Moreover, the effect of surface finishing on emissivity values has been investigated

Novel microcellular ceramics from a silicone resin

Microcellular silicon oxycarbide open cell ceramic foams were fabricated from a silicone resin. Microcellular foams, with a cell size ranging from 3c1\u201380 \u3bcm, were fabricated using poly(methyl methacrylate) microbeads as sacrificial templates. The compression strength of the foams decreased with increasing cell size

Highly porous macro- and micro-cellular ceramics from a polysilazane precursor

Micro- and macro-cellular SiCN and SiOCN foams were produced via two different routes by using a polysilazane preceramic polymer. In the first route, a mixture of partially cross-linked polysilazane and poly(methylmetacrylate) microspheres, used as sacrificial fillers, was warm pressed and subsequently pyrolyzed to create micro-cellular foams. In the second route, liquid polysilazane was mixed with a physical blowing agent and the blend was cured and pyrolyzed, leading to the formation of macro-cellular ceramics in a one-step process. Ceramic components of different morphology and characteristics, depending on the processing method adopted, were fabricated. The foams had a mostly interconnected porosity ranging from 3c60 to 80 vol% and possessing a compressive strength in the range 3c1\u201311 MPa. Some oxygen contamination was found in the foams obtained using the sacrificial fillers, probably because of the adsorbed humidity on their surface. The polymer derived ceramic (PDC) route is an efficient and cost effective way to produce SiCN-based foams possessing tailored pore architecture and properties suitable for high temperature applications