Histomorphometric, ultrastructural and microhardness evaluation of the osseointegration of a nanostructured titanium oxide coating by metal-organic chemical vapour deposition: An in vivo study

Over the past decade the increase of elderly population has determined a rise in the incidence of bone fractures, and the improvement of the implant-bone interface remains an open problem. Metal-organic chemical vapour deposition (MOCVD) has recently been proposed as a technique to coat orthopaedic and dental prostheses with metal nanostructured oxide films either through the decomposition of oxygenated compounds (single-source precursors) or the reaction of oxygen-free metal compounds with oxygenating agents. The present study was performed to assess the in vivo biocompatibility of commercially pure Ti (control material: TI/MA) implants (∅ 2mm×5mm length) coated with nanostructured TiO₂ films by MOCVD (Ti/MOCVD) and then inserted into rabbit femoral cortical (middhiaphysis) and cancellous (distal epiphysis) bone. Histomorphometric, ultrastructural and microhardness investigations were carried out. Four and 12 weeks after surgery, significant (p<0.0005) increases in AI of Ti/MOCVD implants were observed as compared to Ti/MA implants (distal femoral epiphysis: 4 weeks=8.2%, ns; 12 weeks=52.3%, p<0.005; femoral diaphysis: 4 weeks=20.2%, p<0.0005; 12 weeks=10.7%, p<0.005). Bone microhardness results showed significant increases for the Ti/MOCVD versus Ti/MA implants at 200μm in the femoral diaphysis (4 weeks=14.2, p<0.005) and distal femoral epiphysis (12 weeks=14.5, p<0.01) at 4 and 12 weeks, respectively. In conclusion, the current findings demonstrate that the nanostructured TiO₂ coating positively affects the osseointegration rate of commercially pure Ti implants and the bone mineralization at the bone-biomaterial interface in both cortical and cancellous bone.