Chemistry and Applications
Calcium Phosphate Compound
There are many calcium phosphate compounds: among them HAp is the form characterized by a stoichiometric Ca/P molar ratio of 1.67 and a crystalline phase having hexagonal symmetry (ref).
Biological calcium phosphates are non-stoichiometric, Ca- and (OH)- deficient crystals, in which the Ca/P molar ratio is <1.67(ref). They are characterized by poor crystallinity, foreign ions presence and non-apatitic surface layers (ref).
Amorphous calcium phosphate (ACP) is instead characterized by a Ca/P ratio in the range [1.5-1.67](ref).
By playing with composition, size and shape, surface and multi-functionality modification, a wide range of hydroxyapatite-based application properties can be achieved.