Bioactivity property of TiO2 MOCVD coatings on Ti substrates with different pristine morphology

Titanium and its alloys have been widely used for dental implants due to their excellent combination of strength-to-weight ratio, excellent corrosion resistance and biocompatibility [1]. A surface feature of Ti is the capability to spontaneously form a thin (4-6 nm) stable amorphous TiO2 film. Despite the excellent biocompatibility of the native oxide film, this oxide is known to seldom bond chemically to bone tissue [2 and ref. therein]. Various techniques have been developed in order to grow up TiO2 layers with improved characteristics with respect to the native layer: deposited rutile and anatase layers compared to native TiO2 show enhanced bone-like precipitation at the surface in simulated body fluids. MOCVD technique has been applied to the growth of TiO2 coatings, which successfully underwent several biological tests [2 and ref. therein]. However, the influence of the TiO2 MOCVD coating on the bioactivity of Ti substrate with peculiar pristine morphology has been weakly explored. In this regard, besides to the chemical surface composition, the roughness and the topography of the Ti surface are significant parameters that affect the rate and quality of osseointegration. In this work, three types of Ti substrates (machined, sandblasted, and sandblasted/acid etched) with different morphology were coated with 200 nm titanium oxide films by using MOCVD, operating at 350°C and 100 Pa. The influence of the pristine substrate morphology on TiO2 crystalline structure, morphology, surface wettability and bioactivity is here presented. It is shown that the specific morphology of the substrate influences both the crystalline phase of the TiO2 and the crystallite size. SEM analysis shows an optimal conformal coverage of the coating for all substrates, with specific grain size as a function of the substrate morphology. Even the wettability depends on the Ti substrate features, demonstrating a superhydrophilic behaviour for the sandblasted/acid etched samples after MOCVD deposition. Finally, bioactivity experiments were carried out in order to evaluate the influence of substrate morphology on the bioactivity of the TiO2/Ti samples in simulated body fluid (SBF).