Specific Features of the Crystal Structure of Calcium Hydroxyapatite in Native Bone Tissue

The effects of physiological and pathogenic factors on the crystal structure of calcium hydroxyapatite Ca₁₀(PO₄)₆(OH)₂ in mineralized bone tissues are considered. The unit cell constants of bioapatite, the unit cell deformation, and the crystallite sizes in different groups of bone tissues were analyzed based on the results of X-ray diffraction studies. The main mechanisms responsible for spatial-temporal changes in bone nanostructures were revealed. It was demonstrated that, along with violations of the stoichiometry, an important role is played by the crystallite sizes, estimated as the coherent scattering regions, the number of atoms in which differs by more than two orders of magnitude, and electrostatic interactions between the unbalanced charges of nanocrystallites and hydrated nanolayers of the mineral matrix.