Physicochemical Properties and Osseointegration of Titanium Implants with Bioactive Calcium Phosphate Coatings Produced by Detonation Spraying

Detonation spraying is thought to be a promising approach to producing calcium phosphate bioceramic coatings on various implants owing to the possibility of ensuring conditions that minimize undesirable thermal effects. In this work, this method has been used to produce coatings (up to ≈100 μm in thickness) based on nonstoichiometric hydroxyapatite (HA) with a Ca/P atomic ratio in the range Ca/P ≈ 1.45–1.50 on the surface of titanium substrates. Detailed characterization of the coatings by X-ray diffraction, Raman spectroscopy, and optical and electron microscopy has shown that, under the conditions of this study, the parent HA underwent a number of changes during the spraying process, which led to the formation of tricalcium phosphates (TCPs) (α-TCP and β-TCP) along with HA and amorphous phosphates. As a result, the Ca/P stoichiometric ratio increased (to Ca/P ≈ 1.65–1.67). Osseointegration effectiveness was evaluated in vivo by comparing biological reactions with control specimens (uncoated surgical screws) and coated screws using laboratory animals (Wistar rats). Histological and tomographic examination of ante- and postmortem materials showed that the coatings stimulated chondrogenic osteogenesis in the implant/bone contact region. These effects did not show up until 60 ± 5 days after implantation.