HA/TCP (hydroxyapatite/calcium triphosphate) biphasic porous micro-macro phosphocalcic bioceramic is a product with chemical-physical characteristics similar to the mineral matrix of the bone tissue, consisting mainly of more stable phosphocalcic substances, and presenting an intercommunicative porous architecture and required mechanical resistance which allow it to be naturally and continually replaced by human body components in the process of bone reposition. Such composition and structure allow for the transmission of muscular effort compatible with the functions of the skeleton and muscular system.
The scaffold is the physical support which will become the graft (bone replacement, material used for filling or bone reconstruction). To provide effective results, those materials must bear features similar to the mineral bone matrix: chemical composition and physical structure. They must also be as stable as the mineral matrix to allow for a continuous process to occur until the mature bone is formed.
If our mineral bone matrix could be easily reabsorbed and/or turned soluble, our bone structure, or skeleton, would not exist. Those materials require an architectural and geometrical physical structure suitable to receive the deposition of cells, proteins and other substances. They should also keep empty spaces to accept tissue and vascular neoformation. Then they would be incorporated to the newly formed tissue and later gradually replaced.
The balanced association of these components allows an equilibrium between the time of reabsorption of the material by the organism, the bone reconstitution, and the mechanic resistance maintenance, since there is a more stable phase (HA), which is reabsorbed more slowly and a more soluble one (B-TCP), that is less stable and more rapidly reabsorbed. .
The organic mineral structure has specific architectural characteristics and intercommunicative micro and macro pores with the empty spaces required for the interpenetration and deposition of the organic substances and structures which identify this complex structure: a composite, that is, the bone tissue.
The micro pores, with diameters reaching 10μ present capillarity and superficial tension as properties to store, transport and release proteic substances (chemotaxis) - like the individual's morphogenetic signaling factors - for tissue formation, or extrinsic substances as growth factors (BMP's), medications and chemotherapeutics. Those characteristics determine the intrinsic induction property of this material. Associated with its geometry, the product carries additional advantage when compared to other materials which do not have those characteristics, since osteogenesis (bone neoformation) is geometrically dependent.
Similarly, the macro pores reaching up to 500μ allow the deposition of the necessary cells and the development of the process by haptotaxis (directed movement of the cells on the surface of the material), thus enabling bone formation both within the pores and on the surface of the material. The result is optimal adherence due to the release of an amorphous cementing substance produced by the osteoblast, which provides the system with structure and mechanical resistance.