The structure of titanate nanobelts used as seeds for the nucleation of hydroxyapatite at the surface of titanium implants

The sequence of steps of a chemical treatment having as its goal the induce of nucleation and the growth of hydroxyl carbonated apatite (HCA) at the surface of titanium implants was studied by scanning and transmission electron microscopy in cross-section. In the first step, an acid etching forms a rough titanium hydride layer, which remains unchanged after subsequent treatments. In the second step, soaking in an NaOH solution induces the growth of nanobelt tangles of nanocrystallized, monoclinic sodium titanate. In the third step, soaking in simulated body fluid transforms sodium titanate into calcium titanate by ion-exchange in the monoclinic structure. HCA then grows and embodies the tangled structure. The interfaces between the different layers seem to be strong enough to prevent interfacial decohesion. Finally, the role of the titanate structure in the nucleation process of HCA is discussed.