There is currently little information available about the ideal surface conditions for promoting osseointegration around implants. When used for investigations, polycrystalline titanium presents a variety of crystallographic planes, rendering it impossible to distinguish effective binding sites or crystallographic planes. Investigations of protein attachment to and expression of osteoblast phenotype on substrates that are homogeneous and structurally defined such as Ti single crystals will identify molecular and crystallographic attributes that determine the cell-substrate recognition process. The central hypothesis of this proposal is that different crystallographic planes of titanium with different atomic densities will show differences in surface energy and oxide characteristics. Consequently, specific crystallographic planes will be preferred for protein and osteoblast attachment and the expression of bone phenotype. This study seeks to determine the features of the different crystallographic planes of titanium and the surface conditions that will promote expression of the bone phenotype. We have succeeded in devising techniques for fabricating large single crystals of titanium using an optical Imaging Floating Zone furnace. Three crystallographic planes,of different atomic densities have been selected for investigation. To pursue this issue using samples with defined crystal planes we will address the following four specific aims. 1. To identify which crystallographic planes have surface energies that promote cell attachment. 2. To identify the surface treatments that yield the desired surface energy levels and determine the characteristics of oxide layers formed on different crystallographic planes of titanium. 3. To ascertain if atomic density, surface energy, oxide formation and surface treatments govern the adsorption of specific serum proteins to titanium. And 4. To correlate crystallographic plane orientation/surface characteristics with osteoblast attachment and expression of the bone phenotype on titanium single crystals. An understanding of material/cell interactions at the crystallographic level could lead to optimization of implant surfaces for osseointegration.
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