Titanium and its alloys, as well as stainless steel and cobalt-chromium alloys have been used as implantable biomaterials for several decades. Nevertheless, despite their great application as biomaterials, these alloys are known for not presenting physicochemical characteristics that stimulate the growth of bone tissues. Besides being unable to stimulate the cellular differentiation processes, these alloys may suffer from corrosion processes and the formation of fibrous tissues, which leads to the detachment of prostheses and so a shorter lifespan. In order to get around these characteristics, many studies have looked at processes to coat the metal alloys with hydroxyapatite (HAp). This type of coating, over the metal substrate, stimulates bone tissue formation, as well as improving the corrosion properties, reducing the formation of fibrous tissues and so giving a longer life to the implanted products.
A great number of techniques have been developed for coating HAp on titanium, such as plasma spraying, physical vapour deposition, solgel, electrochemical deposition, electrophoretic deposition, immersion in SBF (simulated body fluid) and biomimetic . Amongst these, plasma spraying is widely used commercially , however, the high cost for equipment, low crystallinity and the presence of phases that are undesirable in a coating, are some problems of this technology . These kinds of problems could lead to the solubilization and detachment of the coating, with consequent loosening and movement, resulting in an inflammatory reaction, that may cause loss of the implant.
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