Surface analyses of micro-arc oxidized and hydrothermally treated titanium and effect on osteoblast behavior.

Osteoblast adhesion on the implant material surface is essential for the success of any implant in which osteointegration is required. Surface properties of implant material have a critical role in the cell adhesion progress. Titanium and its alloys are widespread and increasingly used as implant material in dentistry and orthopedics because of their excellent biocompatibility, which is attributed to a passive layer of TiO2 on the surface. In this study, the micro-arc oxidizing (MAO) and hydrothermally synthesizing (HS) methods were used to modify the TiO2 layer on the titanium surface. The surface microstructure was observed by scanning electron microscopy. The surface energy was assessed. The mouse osteoblastic cell line (MC3T3-E1) was seeded on the treated surfaces to evaluate their effect on cell behavior. This included cell adhesion kinetics, cell proliferation, cell morphology, and cytoskeletal organization. The surface structure of MAO samples exhibited micropores with a diameter of 1-3 microm, whereas the MAO-HS-treated samples showed additional multiple crystalline microparticles on the microporous surface. The surface energy of MAO and MAO-HS was higher than that of titanium. The cell adhesion rate was higher on the MAO-HS surface than on the MAO and titanium surface, but without any significant difference between them. After 3 days of culture, cells proliferated significantly more on the MAO and titanium surface than on the MAO-HS surface. The cytoskeletal organization was analyzed by actin and vinculin staining on all the samples. We conclude that the MAO and MAO-HS methods change the surface energy of TiO2 layer on the titanium surface. This may have an influence on the initial cell attachment. Other surface characteristics may be involved in the cell proliferation, which is different from cell attachment on the sample surface. A longer-duration cell experiment should be conducted to see the effect on cell differentiation. Future in vivo evaluation may give further evidence to optimize the surface character of this kind of implant material.

Cell orientation and cytoskeleton organisation on ground titanium surfaces.

A stable connection between the biomaterial surface and the surrounding tissue is one of the most important prerequisites for the long-term success of implants. Therefore, a strong adhesion of the cells on the biomaterial surface is required. Beside the surface composition the surface topography influences the properties of the adherent cells. The quality of the connection between the cell and the biomaterial is-among other factors-determined by the dimensions of the surface topography. Osteoblasts and fibroblast-like cells in contact with a ground biomaterial surface spread in the direction of the surface structures. These aligned cells provide a more favourable adhesion behaviour than a spherically shaped cell. To determine the influence of the surface structure on the cell alignment and cytoskeleton organisation or arrangement, substrate discs of cp-titanium were ground, producing different roughness of the substrates. The oriented cells had a higher density of focal contacts when they were in contact with the edges of the grooves and showed a better organisation of the cytoskeleton and stronger actin fibres. These changes of the aligned cells depend on the peak to valley height of the surface structures.

Interactions between cells and titanium surfaces.

The interaction between cells and implant materials is determined by the surface structure and/or surface composition of the material. In the past years, titanium and titanium alloys have proved their superiority over other implant materials in many clinical applications. This predominant behaviour is caused by a dense passive oxide layer which forms within milliseconds in oxidizing media. Titanium dioxide layers of 100 nm thickness were produced on the surface of cp-titanium grade 2, and on an experimental alloy of high vanadium content (Ti1.5Al25V) as a harmful control. The layers were produced by thermal and anodic oxidation and by coating by means of the sol-gel process. The resulting oxide layers were characterized with respect of their structure and chemical composition. In cell tests (proliferation, MTT, morphology, actin staining), the reaction of the cells was examined. It was shown that the sol-gel-produced titanium oxide layer is able to shield the cells from toxic alloying elements, with the result that the cell reaction is influenced only by the thin titanium oxide surface layer and not by the composition of the bulk material.

The relative influence of the topography and chemistry of TiAl6V4 surfaces on osteoblastic cell behaviour.

Proliferation and adhesion of mouse (MC3T3-E1) osteoblastic cells and primary human osteoblastic cells were carried out on Ti6Al4V titanium alloy samples with varied surface roughnesses. Mechanically or manually polished surfaces were prepared to produce respectively non-oriented or oriented residual polishing grooves. Sand-blasted surfaces were prepared using 500 microm or 3 mm alumina particles. Surface roughness parameters showed a negative correlation in comparison to proliferation and adhesion parameters. X-ray microprobe chemical surface microanalysis showed complete disturbance of the surface element composition of the Ti6Al4V alloy following sand-blasting treatment. An AlOx-enriched layer was observed on sample surfaces. This may lead to the suspicion that the concomittant effect of surface roughness amplitude and AlOx surface concentration has an effect on osteoblastic cell proliferation and adhesion. These findings show the significance of chemical surface analysis after any surface treatment of titanium-based implants before any biological use.