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Date of Award

2016

Document Type

Campus Access Dissertation

Degree Name

Doctor of Philosophy in Mechanical Engineering-Engineering Mechanics (PhD)

Administrative Home Department

Department of Mechanical Engineering-Engineering Mechanics

Advisor 1

Tolou Shokuhfar

Advisor 2

Craig Friedrich

Committee Member 1

Cortino Sukotjo

Committee Member 2

Christos Takoudis

Committee Member 3

Mathew T. Mathew

Committee Member 4

Reza Shahbazian Yassar

Abstract

Titanium has been used for dental and orthopaedic implants since decades due to its suitable surface properties. However, these implants require revision surgery after 10-15 years of implantation due to various reasons including lack of osseointegration, infection, corrosion and wear debris causes toxicity and tissue reaction amid implant site. Therefore, developing a surface that has a potential to fight the aforementioned drawbacks, is the area of research in biomedical industries.

Titanium nanotubes (TNTs) have received significant attention for biomedical applications due to its multifunctional benefits that includes 1) improved osseointegration through its high surface area for cells to make strong focal adhesion 2) improved cell differentiation through their biomimetic nano-scale topography, which provides biomechanical cues to the nucleus, thereby triggering cell differentiation, 3) their capability to intercalate biomolecules, including drugs, and growth factors that can facilitate bone-implant contact and anti-inflammatory agents etc. 4) their low elastic modulus can provide stress gradient to the surrounding tissue, thereby preventing stress shielding effect and 5) its excellent corrosion resistance property due to its significantly thick TiO2 layer. Although many advantages of TNTs has been reported, some clinical concern still needs to be answered are how mechanically and electrochemically stable these nanotubes are in presence of biological environment. Therefore, a simulated approach has been employed to investigate 1) electrochemical stability of nanotubes before and after functionalizing with vitamin D and calcium phosphate coating in simulated body fluids, 2) mechanical stability of nanotubes in two different density simulant bone, 3) mechanical stability of nanotubes in PBS or BCS environment, and 4) Cytotoxicity of loose TNTs in varying concentration. The results concluded that the corrosion resistance property of nanotube remains intact even after functionalizing with vitamin D and calcium phosphate coating. Additionally, the nanotubes are mechanically strong after insertion in 15 or 20 pounds per cubic foot simulant bone in the presence of PBS or BCS solution, which is proved by field emission scanning electron microscopy. Additionally, maximum of 1 mg/ml of TNTs agglomerates were exposed to MG-63 cells for a period of 72 hours. After 72 hours, fluorescence microscopy was performed to investigate the cells morphology. It was observed that the TNTs are not toxic and cells appeared to be healthy and well spread. The composition of TNTs is TiO2 that is not only biocompatible and bio-inert but it has also shown some potential in re-mineralization of dental caries after being demineralized by bacteria.

Tissue discoloration is one of cause of revision surgeries for dental implants due to the gray colored appearance of Ti in patients with thin gingiva tissue. In order to overcome tissue discoloration, a novel surface was fabricated by forming transparent TiO2 nanotubes on ZrO2 which not only has bright colored appearance compared to Ti but it is also hydrophilic, and improves cell proliferation and adhesion compared to bare roughened ZrO2.

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