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INTRODUCTION The surfaces of endoosseous dental implants have been subjected to numerous modifications in order to create a surface which can provide rapid bone healing and fast implant loading. Each modification has involved changes to the chemical composition and topography of the surfaces which have resulted in various biological reactions to the implanted material. AIM The aim of this study was to evaluate the surface topography and chemistry of various modified titanium surfaces: (1) machined surface (MA), (2) alumina-blasted (Al2O3), (3) alumina-blasted and acid-etched (Al2O3 DE), (4) hydroxyapatite/tricalcium phosphate grit-blasted (HA/TCP) and (5) hydroxyapatite/tricalcium phosphate grit-blasted and acid-etched (HA/TCP DE) and to analyse the effects of surface roughness, and chemical composition on human osteoblast vitality, differentiation, morphology and orientation. MATERIALS AND METHODS The modified surfaces were subjected to topographic analysis using Scanning Electron Microscopy (SEM), optical profilometry, roughness analysis and chemical composition evaluation using Energy Dispersion Spectroscopy (EDS) analysis. The biological effects of the titanium modifications was analysed using human osteoblasts cell culture where the cell morphology, vitality (MTS assay) and differentiation (ALP activity) was analysed. RESULTS The machined surfaces were classified as anisotropic, smooth and composed of titanium and oxygen. The blasted surface samples along with the blasted and etched samples were found to be isotropic and rough. The grit-blasting procedure resulted in the incorporation of components from the blasting material. In the case of the blasted and etched samples, etching decreased the surface development as indicated by the Sdr and also reduced the amount of chemical compounds incorporated into the surfaces during the blasting procedure. The attached NHOst cells, proliferated the surfaces. With regard to the MA samples, the cells spread close to the titanium surface, with expanded cytoplasmic extensions and lamelipodia and were oriented in line with the groves left after machining. On the rough substrates, cells were less dispersed and exhibited numerous cytoplasmic extensions, filopodia and interconnections, they were not oriented with respect to the surfaces features. The cell viability of all samples except for Al2O3 decreased after the first day of culture. For all Al2O3, Al2O3 DE and HA samples the viability increased with culture time after an initial reduction. At the end of the culture period the ALP activity was slightly greater on Al2O3 and HA samples compared to the control with the HA DE sample having the same activity as the control. The Al2O3, HA and HA DE ALP samples showed comparable activity and were statistically different from MA and Al2O3 DE samples. CONCLUSIONS In this study, variously treated titanium surfaces were correlated with osteoblastic cell viability, morphology and differentiation in comparison with the plastic and smooth titanium. All examined surfaces were found to be biocompatible. Favourable cell reactions were observed for Al2O3 and HA blasted surfaces. The surface roughness patterns influenced the growth orientation while the surface topography influenced osteoblast morphology. Further animal studies are necessary to compare the in-vivo effect on osseointegration of these modified titanium surfaces.