MS Defense Seminar
Monday, July 20, 2015
Robert B. Goergen Hall, Room 101
“The Effect of Wear on Corrosion Properties of Surface-Modified Titanium”
Presented by: Ryan Blank
Co-supervised by: Prof. Luiz Meirelles and Prof. Wyatt Tenhaeff
Grade 4 titanium, a primary material for dental implants, was investigated to determine to what degree induced wear from implant insertion elevates corrosion activity. Since these implants may be exposed to a number of chemical environments, as well as a number surface treatments for better integration, it was important to designate specific groups for various changes in corrosion resistance. Electrochemical data analyzed in a three-electrode jacked cell included: (a) corrosion potential (Ecorr); (b) polarization resistance (Rp); (c) corrosion current density (idensity). Surface modifications included polished, blasted (SB) and SB + acid-ecthing (SBA). Samples were tested without and with induced wear in different pH levels. Surface roughness was analyzed by interferometer, and chemical surface analysis was done using a scanning electron microscope with energy-dispersive X-ray spectroscopy (SEM/EDS). Statistical analysis was performed using the MIXED Procedure based on differences of least square means. Results show anodic Ecorr values, lowered Rp, and elevated idensity with the introduction of wear. There was a difference in corrosion demonstrated among polished, SB, and SBA due to the roughness and chemical composition. Results for current density were analyzed using an estimated surface area based on the interfacial ratio of the surface, rather than using geometrical area. Lower pH (3.0) clearly resulted in higher corrosion compared to 7.4 and 9.0. This was a consistent find among testing parameters, in particular for polished samples and samples with induced wear. EDS results show that the polished, SBA, and SB groups contain residual aluminum as a result of the polishing and blasting techniques. Polished and SBA groups were modified with hydroxyapatite (HA) to test changes in corrosion resistance. The HA surface modification was found to improve resistance to corrosion based on some of the electrochemical parameters evaluated (Ecorr and idensity). It is therefore determined that while roughened (blasted) titanium may be a viable means of increasing osseointegration, corrosion must be addressed. HA surface modification represents an alternative to improve corrosion resistance of titanium samples.