Electronic properties of anodized TiO₂ electrodes and the effect on in vitro response

Abstract

For dental implants, improved osseointegration is obtained by modifying the surface roughness as well as oxide morphology and composition. A combination of different effects contributes to enhanced performance, but with surface roughness as the dominant factor. To single out the effect of oxide conductivity on biological response, oxide films with similar thickness and surface roughness but different electronic properties were formed using galvanostatic anodization. Three different current densities were used, 2.4, 4.8, and 11.9 mA cm(-2) , which resulted in growth rates ranging from 0.2 to 2.5 V s(-1) . The electronic properties were evaluated using cyclic voltammetry and impedance spectroscopy, while the biological response was studied by cell activity and apatite formation. The number of charge carrier in the oxide film close to the oxide/solution interface decreased from 5.8 × 10(-19) to 3.2 × 10(-19) cm(-2) with increasing growth rate, that is, the conductivity decreased correspondingly. Cell response of the different surfaces was tested in vitro using human osteoblast-like cells (MG-63). The results clearly show decreased osteoblast proliferation and adhesion but higher mineralization activity for the oxide with lower conductivity at the oxide/solution interface. The apatite-forming ability was examined by immersion in simulated body fluid. At short times the apatite coverage was ∼26% for the anodized surfaces, significantly larger than for the reference with only 3% coverage. After 1 week of immersion the apatite coverage ranged from 73 to 56% and a slight differentiation between the anodized surfaces was obtained with less apatite formation on the surface with lower conductivity, in line with the cell culture results.

Assessing the Efficacy of Whole-Body Titanium Dental Implant Surface Modifications in Inducing Adhesion, Proliferation, and Osteogenesis in Human Adipose Tissue Stem Cells

“…The most important factor responsible for the stability and duration of an oral implant is likely the macro- and micro-topography of the implant. In fact, properties such as the shape, elasticity, roughness, chemical composition, electric charge, oxide type, and thickness have been demonstrated to play significant roles [ 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 ]. Theoretically, the surface geometry, charge and their chemical-physical modifications have to fulfill four main tasks: (1) prevent the unspecific adsorption of denatured proteins at the interface between the oral tissues and implants [ 12 ]; (2) attract differentiated or undifferentiated progenitor cells from the native tissue [ 13 ]; (3) induce native tissue or progenitor cell regeneration and differentiation [ 13 ]; and (4) guarantee an optimal load transfer to the bone [ 6 , 14 ].…”