Effect of Nanocrystallized Hydroxyapatite Coating on Bone Healing Evaluated by Synchrotron Radiation Diffraction

The properties of the interface between biomaterials and the host tissue play an important role for the process of successful adaptation of implants. Extensive research has focused on shortening the time of osseointegration by modifying the surface in adding a coating such as hydroxyapatite (HAp). We have developed a new type of biocompatible nanohydroxyapatite (n-HAp) coatings, which are characterized before and after deposit on a Ti-6Al-4V substrate using neutron diffraction and scanning electron microscopy. Three months after the implantation in the sheep tibias, high-energy synchrotron radiation (ID15B, ESRF, Grenoble, France) diffraction studies of the cortical bone identify that the c-axes of HAp are preferentially oriented in the direction of the stresses that bone usually withstands. This non destructive analysis of the bone-implant interface proves that bone maturation is achieved successfully with this novel n-HAp coating and demonstrates that the mineralization is completed without spatial organization. None of these findings are obtained with uncoated titanium alloys. The presence of this n-HAp coating on Ti-6Al-4V substrate is decisive in obtaining this mature bone at the interface.