Titanium and its alloys have been widely used as materials in biomedicine and in particular, for dental implants, and one main reason is their unique ability to osseointegrate with the host bone. This phenomenon forms a strong bone-to-implant bonding. The rate and quality of osseointegration of a titanium dental implant depends heavily upon its surface properties. Over time, various surface treatment methods have been developed to further improve osseointegration of titanium-based biomaterials. This PhD thesis focuses on promising surface treatment methodology: surface charge modification. A negative charge has been known to promote the osseointegration of titanium biomaterials. Before the current work there was no practical approach to induce negative charge on titanium surfaces. The goal was to find such a practical technique. The current investigations revealed that sandblasting, a commonly used surface treatment method, can generate a negative charge on the surface of titanium, and also titanium alloy and stainless steel micro-implants, due to the triboelectric effect. Stainless steel doesn’t osseointegrate. The basic methodology of these studies was to sandblast titanium and measure the amount and polarity of the static charge on titanium surfaces. The effects of several important parameters were evaluated, including the sandblasting material, the size of the blasting grits, and the shape of the titanium material. Statistical analysis was performed on the results of the static charge measurements. In addition, the contamination of the titanium sandblasting was also evaluated. The results of the current studies suggested that sandblasting could generate static charges on titanium and stainless steel surfaces. However, such charges gradually dissipate into the atmosphere. The amount, polarity, and the decay rate of the charge depend on many factors tested in the experiments. These results might explain the beneficial of sandblasting on the osseointegration of titanium implants. Osseointegration has been traditionally attributed to its roughening effects. Moreover, the current studies may potentially lead to improved sandblasting techniques, becoming in mind that more research should be carried out. / published_or_final_version / Dentistry / Doctoral / Doctor of Philosophy

The high performance of bone implants depends on the positive response of osteoblasts to the surface of the materials manufactured for the implant. Cell response in turn strongly depends on the nature of the initial interaction of macromolecules involved in cell adhesion and proliferation with the atomic structure of the surface of the material used for the implant. The initial interaction between bone specific extracellular matrix proteins and the solid substrate influences cell response at the cell-implant interface. This interaction is crucial for implant stability, long-term durability, and osseointegration. Despite extensive research undertaken to develop high-quality material for implants in order to improve the cell-substrate interaction, little is known about the significance of the atomic structure of the substrate and the role of molecular machinery involved in cell-substrate interaction. Using a combined approach involving material sciences and cell and molecular biology, the objectives of this research are to evaluate the response of pre-osteoblast and fibroblast cell lines to novel bulk polycrystalline and single crystal titanium based material and assess the role of crystal size and orientation. / Novel bulk nano-structured titanium substrates were produced by the process of high-pressure torsion (HPT). These materials have a significant advantage compared to conventional titanium-based materials by having higher surface wettablity, mechanical properties as well as a distinct surface oxide layer and atomic structure. A co-culture system was adapted to investigate the differential response of pre-osteoblast and fibroblast cell lines to titanium and titanium dioxide single-crystal substrates. / The results of this study provide clear evidence that crystal size and specific crystallographic orientation can be used to improve cell adhesion and proliferation. The nanostructured titanium substrates show strong interaction with pre-osteoblast cells as evident by the higher expression of fibronectin and the formation of extensive focal adhesion. Differential cell behaviour of pre-osteoblasts and fibroblasts are observed in cultures grown on the substrates with specific crystallographic orientations. The degree of cell attachment of the pre-osteoblasts is considerably higher on Ti-(1120) crystal face compared with the fibroblasts. These findings have profound implications for the improved osseointegration and inhibition of fibrosis leading to long-term implant consolidation and stability.

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