Bioactive Calcium Phosphate Coatings for Bone Implant Applications: A Review

This review article deals with the design of bioactive calcium phosphate coatings deposited on metallic substrates to produce bone implants. The bioceramic coating properties are used to create a strong bonding between the bone implants and the surrounding bone tissue. They provide a fast response after implantation and increase the lifespan of the implant in the body environment. The first part of the article describes the different compounds belonging to the calcium phosphate family and their main properties for applications in biomaterials science. The calcium to phosphorus atomic ratio (Ca/P)at. and the solubility (Ks) of these compounds define their behavior in a physiological environment. Hydroxyapatite is the gold standard among calcium phosphate materials, but other chemical compositions/stoichiometries have also been studied for their interesting properties. The second part reviews the most usual deposition processes to produce bioactive calcium phosphate coatings for bone implant applications. Plasma spraying is the main industrial process, but magnetron sputtering, pulsed laser deposition, electrospray deposition, electrophoretic deposition, and electrodeposition are also widely studied in academic and industrial research. The last part describes the main physicochemical properties of calcium phosphate coatings and their impact on the bioactivity of bone implants in a physiological environment.