The influence of Sr and H^sub 3^PO^sub 4^ concentration on the hydration of SrCaHA bone cement

Sr-contained calcium hydroxyapatite (SrCaHA) cement is a potential biomaterial for in vivo bone repair and surgery fixation due to its excellent biodegradability, bioactivity, biocompatibility, easily shaping and self-hardening. We had ever reported the in vitro physiochemical properties, biocompatibility and in vivo degradability of the SrCaHA cement obtained by mixing a cement powder of Ca^sub 4^(PO^sub 4^)^sub 2^O/CaHPO^sub 4^/SrHPO^sub 4^ and a cement liquid of diluted H^sub 3^PO^sub 4^ aqueous solution. In the present study, we intensively studied the influences of both Sr content and H^sub 3^PO^sub 4^ concentration in diluted phosphoric acid aqueous solution on the setting time, hydration heat-liberation behaviours, and real-time microstructure and phase evolutions of the SrCaHA cement. The results show that both PO^sub 4^ ^sup 3-^ and H^sup +^ ions in PA solution attended the hydration reaction as reactants, and thus the increase of the PA concentration not only promoted the dissolution of Ca^sub 4^(PO^sub 4^)^sub 2^O but also pushed the hydration progress of SrCaHA bone cement. Sr content exhibits a remarkable retardation role on the apatite transformation of the SrCaHA cement pastes which probably attributed to its higher degree of supersaturation for yielding apatite crystals and lower transformation rate when exposed to the Sr^sup 2+^-containing hydration system. This present results contribute to a better understanding on the hydration mechanism of the new SrCaHA cement and help to the more precisely controlling of its hydration process.[PUBLICATION ABSTRACT]