Thermal Oxidation of Titanium for Improved Medical Implant Osseointegration

1. Thermal Oxidation of Titanium for Improved Medical Implant Osseointegration Melanie Hamilton NSF REU Advisor: Dr. CortinoSukotjo Mentors: Arman Butt and Sweetu Patel University of Illinois at Chicago

2. Implant Osseointegration • Implantsimprove quality of life • Implants require bone-implant connection to be successful • Osseointegration Bone Implant • R. Van Noort: Journal of Materials Science, 1987, 22, 3801-3811. http:/www.minuksmile.com/sosimages/cases_missing_teeth10.jpg

3. Titanium • Has many characteristics that enhance osseointegration and are functional for dental use • Biocompatibility • Low density • High ductility • Corrosion resistance • Mechanical resistance • Ti-6Al-4V  alloy with increased mechanical resistance • R. Van Noort: Journal of Materials Science, 1987, 22, 3801-3811.

4. Surface Modification • Creating a micro-rough surface improves osseointegration by increasing surface area • Sandblasting and acid etching • Adding an oxide layer • Increases biocompatibility and corrosion resistance • Purpose: Optimize oxide layer functionality Renfert Sandblaster Rough Surface Rat implant E. Nasatzky, B. Boyan and Z. Schwartz: The Alpha Omegan, 2005, 98, 9-19. J. Pouilleau et al.: Materials Science and Engineering, 1997, B47, 235-243. L. H. Li et al.: Biomaterials, 2004, 25, 2867-2875.

5. Ti Anatase/Hydroxyapatite Cells • When annealed at certain temperatures, TiO2has anatase crystal structure • Anatase crystal structure is similar to hydroxyapatite • Hydroxyapatite is a natural bone growth mineral TiO2 amorphous nanotubes TiO2anatasenanotubes • S. Oh et al.: Wiley Periodicals, Inc. J. Biomed. Mater. Res., 2006, 78A, 97-103. • M. Hirota et al.: Int. J. Oral Maxillofac. Surg., 2012, article in press. M. Uchida et al.: J. Biomed. Mater. Res., 2002, 64A, 164-170.

6. Superlattice: Apatite: Xap = 9.42 Å Anatase: Xan= 9.51 Å Rutile: Xru = 9.19 Å Hydroxyapatite vs. Anatase Apatite Rutile Anatase Masaki Uchida, et. al.: J. Biomed. Mater. Res., 2003, 64, 164-70.

7. Advantages of Thermal Oxidation • Oxide layer thickness is affected by time, temperature, and pressure • Conformal (better than CVD & PVD) • Time efficient – Example: 30 nm oxide layer: • ALD(0.3 Å/cycle/min) 15 hours • Thermal oxidation (550 oC) 1 hour • No precursor (Unlike CVD, PVD, & ALD) • Lower impurities • Lower cost CVD – Chemical Vapor Deposition PVD – Physical Vapor Deposition ALD – Atomic Layer Deposition Rajesh Katamreddy, et. al.: The Electrochemical Society, 2008, 16(4), 113-122. D. Velten, et. al. Journal of Biomedical Materials Research, 2001, 59, 18-28.

8. Thermal Oxidation Schematic O2 http://www.eng.tau.ac.il/~yosish/courses/vlsi1/I-4-1-Oxidation.pdf

9. Experiment Thickness of oxide layers of Ti6A14V after thermal oxidation as a function of temperature and time measured by means ofellipsometry. 600 oC • Thermal oxidation • Atmospheric pressure • Atmospheric air • Constant time (5 hours) • Changing temperatures • Four temperatures • 24 oCexpected to be amorphous • 300 oC, 375 oC, 450 oCexpected to contain anatase • Research shows anatase forms around 250 C – 600 C • Goal: Determine temperatures at which anatase can be detected and characterize the resulting oxide layers with Ellipsometry, Goniometer, and FTIR. 550 oC Velten, D. et. al.: Journal of Biomedical Materials Research, 2002, 59, 18–28. H. Tang et. al.: Journal of Applied Physics, 1994, 75, 2042-2047. E. Gemelli and N.H.A. Camargo: RevistaMatéria, 2007, 12, 525-531.

10. Thermo-couple Air flow Due to fan, only one sample can be done at a time Ti-6Al-4VSample

11. Characterizations • Ellipsometry(smooth sample) • Unsuccessful due to surface roughness • Need smoother and flatter samples • Color Characterization • Relates color of oxide layer to TiO2 thickness • WCA – Water Contact Angle • Measures hydrophilicity • Surface roughness increases with oxidation temperature • Roughness improveshydrophilicity which improves osseointegration • Higher temperature  Increased hydrophilicity • FTIR – Fourier Transform Infrared Spectroscopy (smooth sample) • Determines chemical composition • Crystalline phase (anatase torutile) Güleryüz, H. and Çimenoğlu, H.: Biomaterials, 2004, 25, 3325-3333. Kangarlou, H. and Rafizadeh, S.: Proceedings of the World Congress on Engineering. International Association of Engineers. Volume 2. 2011 • B.E. Deal and A.S. Grove: J. Appl. Phys., 1965, 36, 3770-3778.

12. Color Characterization Thermally oxidized for 5 hours Color vs. Oxide Thicknes from D. Velten, et. al. O. Untracht. “Jewelry Concepts and Technology”; Doubleday: Garden City, New York, 1982, 723-730. D. Velten,et. al.: Journal of Biomedical Materials Research, 2002, 59, 18–28.

13. WCA – Water Contact Angle • Roughness was affected by temperature on sandblasted surfaces (more than smooth surface) • At high temperatures (450 oC) rough samples are more hydrophilic

14. FTIR – Fourier Transform Infrared Spectroscopy 525 oC 600 oC 375 oC 450 oC 300 oC Black = 600 oC Green = 525 oC Red = 450 oC Magenta = 375 oC Blue = 300 oC

15. FTIR – Fourier Transform Infrared Spectroscopy Black 600 oC = 831 cm-1 Green 525 oC = 838 cm-1 Red 450 oC = 847 cm-1 Magenta 375 oC= 854 cm-1 Blue 300 oC = 859 cm-1 CO2 667 cm-1 Anatase – 870 cm-1 Rutile – 830 cm-1 TiO2 420-460 cm-1 Anatase 550 cm-1 ~859 cm-1 D. Velten, et. al.: Journal of Biomedical Materials Research, 2002, 59, 18–28.

16. Conclusions • Anatase exists in the range 300-450oC as the primary crystalline structure • Oxide thickness increases with increasing temperature • Successful optimization of furnace • Expectations were met • Test more samples and temperatures • Obtain more accurate thickness measurements • Possibly test with XRD – X-Ray Diffraction • Santiago Tovar will continue with cell culture assay • Will relate these characterizations to cell assay results Future work

17. Acknowledgements Dr. Christos Takoudis Dr. Gregory Jursich Dmitry Royhman Santiago Tovar Special Thanks to the National Science Foundation EEC-NSF Grant # 1062943 Questions?