Anomalous hardening behavior of a calcium phosphate bone cement.

In this work, an anomalous microscopic and macroscopic behavior during the hardening process of a calcium phosphate cement, based on anhydrous dicalcium phosphate, was observed. Indeed, the standard compressive strength measurements provided completely unexpected results, which encouraged a deeper investigation by means of X-ray diffraction, Fourier transform infrared spectroscopy, and scanning electron and atomic force microscopies. The energy dispersive X-ray diffraction mode was preferred to the conventional angular dispersive one, the former being particularly suitable for the real-time studies, allowing us to follow the hardening process in situ and to confirm that the investigated cement undergoes a long-time crystallization much more complex than expected.