Thesis (Ph. D.)--University of Missouri-Columbia, 2000. / Typescript. Vita. Includes bibliographical references (leaves 176-182). Also available on the Internet.

Thesis (M. App. Sc.)--University of Queensland, 2002. / Includes bibliographical references.

Thesis (Ph. D.)--University of Missouri-Columbia, 2000. / Typescript. Vita. Includes bibliographical references (leaves 176-182). Also available on the Internet.

The currently used biomaterials for surgical implantation include stainless steel, titanium and its alloys. However, due to the non-degradability and the mismatch of the mechanical properties between these metallic implants and human bone, there maybe a long-term adverse effect of inflammation or stress shielding effect. This may lead to bone loss which brings with a higher risk of implant failure. To avoid this problem, implants made of biodegradable materials are the alternatives. Due to the poor mechanical properties of biodegradable polymer especially for load-bearing area, biodegradable metal is used instead. Magnesium is the potential candidate since it is degradable with mechanical properties similar to human bone whilst magnesium ion is an essential element to human bodies. With the advantages of using magnesium for implantations, it can be potentially used for fracture fixation implant and bone substitutes. However, its rapid degradation and release of hydrogen gas may inhibit its use. Hence, modification is required. In this project, plasma immersion ion implantation and deposition (PIII&D) using aluminium oxide as the plasma source was conducted on the magnesium alloys. The corrosion resistance properties of the plasma-treated magnesium alloy were found to display significant improvement in immersion test especially at early time points. The plasma-treated sample was compatible with osteoblasts. Cells attached and grew on the treated sample but not the untreated sample. The animal study showed consistent results with the cell study, and there was a significant increase in bone formation around the treated sample when compared to the untreated sample. The other potential application of magnesium is its usage as a bone substitute. Due to the limitations of autografts and allografts, synthetic bone substitutes are developed. The ideal bone substitutes should have similar properties to those found with autografts. However, no such bone substitutes presently exist; hence, a novel hybrid material is fabricated in this project through the addition of magnesium granules into a biodegradable polymer polycaprolactone (PCL). The immersion test showed that an apatite layer composed of magnesium, calcium, phosphate and hydroxide was formed on the hybrids but not on pure PCL, which suggested that the hybrids were osteoinductive and osteoconductive. The compression test showed that the mechanical properties were enhanced with the incorporation of magnesium granules into pure PCL and were still maintained after 2 months of immersion. Osteoblasts grew well on the PCL-Mg hybrids. The addition of smaller amounts of magnesium granules (0.1g PCL-Mg) resulted in higher ALP activity and up-regulation of different bone markers when compared to the pure PCL. Finally, the animal studies showed that more new bone formation was found around the 0.1g PCL-Mg hybrids especially at early time points, which suggested that the healing time could be shortened. In conclusion, fracture fixation implants and novel bone substitutes based on magnesium were developed in this project. The aluminium oxide coating was able to improve the corrosion resistance properties of magnesium alloy by suppressing the release of magnesium ions. The PCL-Mg hybrids were found to be biodegradable, biocompatible, osteoconductive, osteoinductive and mechanically matched to human bone properties. / published_or_final_version / Orthopaedics and Traumatology / Doctoral / Doctor of Philosophy

The present study was carried out to evaluate the osteoconductive nature of Bio-OssRTM (natural deproteinized bone mineral) when used as an onlay bone substitute in a Guided Bone Regeneration model. The lateral surface of the mandible was exposed bilaterally, in 8 rabbits. On one side of the mandible, two titanium chambers were filled with Bio-OssRTM material and the chambers were then firmly secured to the mandible using screws. The pores in the titanium chambers were covered with a layer of Bio-GideRTM material. On the opposite side of the mandible, chambers without Bio-OssRTM were placed on the lateral side of the mandible as a control. After a healing period of 3 months, histologic sections were obtained from each chamber. It was observed that new bone was generated in both test and control chambers to various degrees. In the test group, the newly generated bone was 18.41% and in the control group it was 5.31%. This difference was statistically significant. Thus, in this experiment, Bio-OssRTM was proven to be osteoconductive.

Thesis (M.S.)--University of Missouri-Columbia, 2007. / The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file (viewed on April 16, 2008) Includes bibliographical references.

Thesis (M.S.)--University of Missouri-Columbia, 2004. / Typescript. Vita. Includes bibliographical references (leaves 136-143). Also available on the Internet.

Thesis (Ph. D.)--University of Missouri-Columbia, 1998. / Typescript. Vita. Includes bibliographical references (leaves 168-176). Also available on the Internet.

Thesis (Ph. D.)--University of Missouri-Columbia, 1998. / Typescript. Vita. Includes bibliographical references (leaves 168-176). Also available on the Internet.

Thesis (M.Phil.)--Hong Kong University of Science and Technology, 2008. / Includes bibliographical references (leaves 92-106). Also available in electronic version.