Reaction of stoichiometric hydroxyapatite with different crystallinity in Mg²⁺ aqueous solution

Abstract

The reaction of stoichiometric hydroxyapatite (HAp) with different crystallinity in Mg²⁺ aqueous solution was investigated using X-ray absorption near edge structure (XANES). Crystallinity is one of important factors for the properties of HAp. Therefore, this study aimed to clarify the effect of crystallinity on the behavior of HAp in aqueous solutions. Stoichiometric HAp samples with different crystallinities were prepared using an aqueous solution precipitation method and subsequent calcination. The Mg-K XANES spectra of the HAp pellets after immersing in Mg(NO₃)₂ aqueous solution were classified into two groups: those of Mg-doped HAp and Mg(OH)₂. This difference is caused by the solubility of the HAp pellets in water, owing to their crystallinity. This result provides insights into the reaction mechanism of HAp in the human body and facilitates selection of suitable biomaterials.