Another PhD from the department!

Summary

Synthetic bone scaffolds can be used in assisting the repair and regeneration of bone tissue in critical size bone defects. Such bone scaffolds need to meet several chemical, physical, and pore architectural requirements in order to facilitate optimal conditions for unobstructed bone tissue regeneration. Reticulated ceramic TiO₂ foams can potentially fulfil many of these requirements, and thus, it was hypothesised that with appropriate processing history, TiO₂ foams may provide a suitable three-dimensional template for the formation of viable bone tissue in a load-bearing physiological environment. Therefore, the main objective of the research work was to produce ceramic TiO₂ scaffolds with appropriate physical, structural, and surface chemical properties for providing a favourable microenvironment for promoting osteogenesis in applications where moderate mechanical support is required, such as maxillofacial and dental applications.

The produced TiO₂ foams were found to exhibit pore architectural features that closely resemble the structural morphology of highly porous human trabecular bone tissue, and which are well-matched with those required from a bone scaffold, namely high porosity, appropriate pore size distribution, and well-interconnected pore volume. When combined with the excellent biocompatibility of the ceramic TiO₂, the highly interconnected pore structure also provided a favourable microenvironment for bone formation, which was manifested by the ingrowth of large quantity of viable mineralised bone tissue within the porous TiO₂ scaffold structures in vivo. As one of the most important prerequisite for a bone scaffold structure is the sufficient permeability of the pore network, the excellent osteoconductive capacity of the TiO₂ scaffolds was attributed to the highly interconnected pore network that allows maximal volume for vascularisation and tissue ingrowth, while still facilitating sufficient structural support at the bone defect site.

The Evaluation committee:

• Professor, PhD Jonathan Knowles, UCL Eastman Dental Institute, University College London, London
• Professor, PhD Kärlis-Agris Gross, Institute of Biomaterials and Biomechanics, Riga University, Riga
• Associate professor dr.odont. Bente Brokstad Herlofson, Univeristy of Oslo, Oslo

The dissertation consists of the following papers:

1. Tiainen H, Lyngstadaas SP, Ellingsen JE, Haugen HJ. Ultra-porous titaniumoxide scaffold with high compressive strength. Journal of Materials Science: Materials in Medicine, 2010, 21, 2783-2792.
2. Tiainen H, Wiedmer D, Haugen HJ. Processing of highly porous TiO2 bonescaffolds with improved compressive strength. Journal of the European Ceramic Society, 2013, 33, 15-24.
3. Tiainen H, Eder G, Nilsen O, Haugen HJ. Effect of ZrO2 addition on themechanical properties of porous TiO2 bone scaffolds. Materials Science and Engineering: C, 2012, 32, 1386-1393.
4. Tiainen H, Monjo M, Knychala J, Nilsen O, Lyngstadaas SP, Ellingsen JE, Haugen HJ. The effect of fluoride surface modification of ceramic TiO2 on the surface properties and biological response of osteoblastic cells in vitro. Biomedical Materials, 2011, 6, 045006
5. Sabetrasekh R, Tiainen H, Lyngstadaas SP, Reseland J, Haugen H. A novel ultra-porous titanium dioxide ceramic with excellent biocompatibility. Journal of Biomaterials Applications, 2011, 25, 559-580.
6. Tiainen H, Wohlfahrt JC, Verket A, Lyngstadaas SP, Haugen HJ. Bone formation in TiO2 bone scaffolds in extraction sockets of minipigs. Acta Biomaterialia, 2012, 8, 2384-2391.
7. Tiainen H, Verket A, Haugen HJ, Lyngstadaas SP, Wohlfahrt JC. Dimensional ridge preservation with novel ultra-porous TiO2 scaffold: an experimental study in minipigs. International Journal of Biomaterials, 2012, Article ID 851264.