Abstract
A great variety of powder metallurgy techniques can produce biomimetic porous titanium structures with similar mechanical properties to host bone tissue. In this work, loose sintering and space holder techniques, two frequently used metallurgical techniques, are compared to evaluate the influences of porosity (content, size, morphology and wall roughness), mechanical properties (stiffness and yield strength) and in-vitro cellular responses (adhesion and proliferation of myoblasts and osteoblasts). These comparisons are made to achieve the best balance between biomechanical and bifunctional behavior of a partial porous implant for cortical bone replacement. Cell adhesion (filopodia presence) and spreading were promoted on both porous surfaces and fully dense substrates (non-porous control surfaces). Porous scaffold samples designed using 50 vol.% NaCl space holder technique had an improved bioactive response over those obtained with the loose sintering technique due to higher roughness and scaffold pore diameter. However, the presence of large and heterogeneous pores compromises the mechanical reliability of the implant. Considering both scenarios, the substrates obtained with 40 vol.% NH4HCO3 and pore size ranges between 100 and 200 μm provide a balanced optimization of size and strength to promote in-vitro osseointegration.
Highlights
For many decades, the emphasis of human biomechanics has been on the partial or total replacement of bone tissue with synthetic implants that the body will, in time, integrate as functional parts
In order to study the cell viability, adhesion, proliferation and cell morphologies of myoblast and osteoblasts growing in the different porous substrates, cross-sections were prepared from the titanium porous cylinders
Cell differentiation studies based on alkaline phosphatase (ALP) enzyme quantification were analyzed according to the manufacturer’s protocol (Alkaline Phosphatase Assay kit Colorimetric, Abcam ab83369, Cambridge, UK) of osteoblast cultured on osteogenic media at 4 and 21 days
Summary
The emphasis of human biomechanics has been on the partial or total replacement of bone tissue with synthetic implants that the body will, in time, integrate as functional parts. Among all other metallic biomaterials used for bone replacement, titanium (Ti) and its alloys have been recognized as the materials with the best in-vivo and in-vitro performance due to their high mechanical strength, fracture toughness, good corrosion resistance and excellent biological properties [1,2,3,4,5,6,7], such as biocompatibility and osteoconductivity (the ability to grow bone tissues over the scaffold surface) [8,9,10] These materials have shown important drawbacks that compromise the reliability of implants: stress-shielding phenomena [11,12,13] and poor osseointegration [14,15]. The influences of content, size range, surface roughness and morphology of the porosity on the mechanical behavior (stiffness and yield strength), and cell adhesion and proliferation, were investigated in detail
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