Effect of anodic surface film of titanium with different structures on the in vivo and in vitro performance

JULIANA PELLEJERO; MATIAS BACA; MARIA KATUNAR; LEANDRO SALEMME; CARLOS BLAS VOTTOLA; SILVIA CERÉ; ANDREA GOMEZ SANCHEZ; KHALIL HADAD; JOSEFINA BALLARRE

Montreal

Congreso; 10th World Biomaterials Congress; 2016

The success of an implant in the body strongly depends of its surface properties. Metallic materials can be protected from the physiological media by a protective barrier, thus minimizing the release of particles and ions from the metal into the body fluids [1, 2]. Surface modification of surgical implants is often used to generate a film that besides being protective can also allow the integration of the metal to the human body, creating a bioactive surface [3-6]. The aim of this work is to study of the surface characteristics and electrochemical response of the anodised Ti compared with the as received one.Specimens of titanium grade 2 were used. Uniform surface finish was obtained by polishing. The specimens were anodised in a two electrode cell, with Pt as counter electrode, in either 1mol/L H3PO4 or in 1mol/L H3PO4 + 0.3% HF solution at a constant potential of 30 V for 60 min with continuous stirring. After anodisation, samples anodised in presence of F were submitted to a thermal treatment of 350°C in air. Electrochemical and immersion tests were performed in a solution with ion concentration similar to blood plasma (SBF).The samples were electrochemically studied in a conventional three-electrode cell after 24, 336 and 672 hours of immersion in SBF. Electrochemical impedance spectroscopy (EIS) measurements potentiodynamic polarization curves were measured.Anodised and control Ti were implanted in Wistar adult rats. The implants were placed by press fit into the femur and tibiae, extending into the medullar canal. The animals were sacrificed after 30 days when the bones with implants were ablated. Conventional X-ray radiographs were taken before retrieving the samples. Toluidine blue was used to stain the cut sections after implantation in rat bone.An anodic oxide film with a sunflower structure is obtained for specimens anodised in phosphoric acid, whereas nanotubular oxides are present when HF is used. The stable crystallographic phase in the all anodized surfaces is anatase. An increase in the crystalline phase is found by Raman spectroscopy and grazing angle DRX in the samples anodised in H3PO4+HF after thermal treatment.Electrochemical tests after 24 h. of immersion display a barrier effect for anodic films compared with the polished surfaces, showing lower current densities and higher total impedance values for the modified surface.In vivo studies show that modified surface with HF present a lower thickness profile of bone formation in the surrounding of the implant when compared with the untreated and anodised in phosphoric acid, and this in turn, present higher bone?implant osseointegration than the untreated metal.As conclusion it is possible to state that although surface modification enhance corrosion behavior in SBF, the change in the surface topography plays a key role determining the new bone proliferation, being from the in vivo point of view, a more promising surface the one obtained without fluorides in the anodisation bath.Support from Consejo Nacional de Investigaciones Científicas y Técnicas, and Universidad Nacional de Mar del Plata, Argentina, are gratefully acknowledged. The authors also acknowledge Dr. Mariela Desimone from INTEMA, Argentina for the Raman and DRX measurements.References:[1] Sul, Y.-T., The significance of the surface properties of oxidized titanium to the bone response: special emphasis on potential biochemical bonding of oxidized titanium implant. Biomaterials, 2003. 24: p. 3893 - 3907.[2] Katti, K.S., Biomaterials in total joint replacement. Colloids and surfaces B, 2004. 39: p. 133 - 142.[3] Kim, H.-M., et al., Preparation of bioactive Ti and its alloys via simple chemical surface treatment. Journal of biomedical materials research, 1996. 32: p. 409 - 417.[4] Koller, G., et al., Surface modification of titanium implants using bioactive glasses with air abrasion technologies. Journal of Materials Science: Materials in Medicine, 2007. 18(12): p. 2291-2296.[5] Sanchez, A.G., et al., Surface modification of titanium by anodic oxidation in phosphoric acid at low potentials. Part 2. in vitro and in vivo study. Surface and Interface Analysis, 2013. 45(9): p. 1395-1401.[6] Ballarre, J., et al., Enhancing low cost stainless steel implants: Bioactive silica-based sol-gel coatings with wollastonite particles. International Journal of Nano and Biomaterials, 2012. 4(1): p. 33-53