Synthetic calcium phosphates: models for biological crystals?

Characterization of the mineral phases of calcified tissues or ectopic calcifications has demonstrated the complexity of biological calcium phosphate salts. Chemists and numerous biologists involved in calcified tissue research have generally described bone and teeth crystallites as hydroxyapatite rather than biological apatites. All biological calcium phosphates have a non-stoichiometric formula, and numerous and variable substitutions. Moreover, in vivo transformations/maturations occur. There is no particular representative synthetic calcium phosphate crystal either for the normal mineral phases of calcified tissues or for the pathological phases. However, they constitute efficient models for the understanding of biological mineralization, and are good approaches to in vitro studies of biomaterials.