Model Evaluation the Effect of Size, Shape and Surface Condition of Apatite Nanocrystals on the Deviation of Ca / P ratio from stoichiometric.

The causes of Ca / P ratio deviation in biological apatites from stoichiometric one were discussed. By the simple model evaluation Ca / P ratio was shown to deviate from stoichiometric one because of small sizes of crystals, and peculiarities in chemical composition of their facets. Also size effect is noted to be unsufficient for explanation of wide variations of Ca / P ratio in biological apatites. It proves the significant contribution of lattice isovalent and heterovalent substitution into variability of Ca / P ratio. The problem of revealing the predominant causes of Ca / P deviation from stoichiometric one and estimation of their relative contribution is related to determination of the functional role of the structural imperfections in biological apatites of different origin. [ABSTRACT FROM AUTHOR]