Rietveld structure and in vitro analysis on the influence of magnesium in biphasic (hydroxyapatite and β-tricalcium phosphate) mixtures

The structure of two different Mg‐substituted biphasic (HAP and β‐TCP) mixtures along with the biphasic mixtures without substituted Mg2+ was investigated using Rietveld refinement technique. The substituted Mg2+ was found in the β‐TCP phase and its influence on the composition has led to an increase in HAP content of Mg‐containing biphasic mixtures when compared with the HAP content detected in pure biphasic mixtures. The refined structural parameters of Ca10(PO4)6(OH)2 and β‐Ca3(PO4)2 confirmed that all the investigated compositions have crystallized in the corresponding hexagonal (space group P63/m) and rhombohedral (space group R3c) structures. The substitution of lower sized magnesium was found preferentially incorporated at the sixfold‐coordinated Ca (5) site of β‐TCP, which is due to the strong Ca (5)·O interaction among all the five different Ca sites of β‐Ca3(PO4)2. The in vitro tests using primary culture of osteoblasts showed that all the tested samples are biocompatible and promising materials for in vivo studies. © 2008 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2009