TiO2 Nanotubes on Ti Dental Implant. Part 3: Electrochemical Behavior in Hank’s Solution of Titania Nanotubes Formed in Ethylene Glycol

Abstract

Anodic oxidation is an easy and cheap surface treatment to form nanostructures on the surface of titanium items for improving the interaction between metallic implants and the biological environment. The long-term success of the devices is related to their stability. In this work, titanium nanotubes were formed on a dental screw, made of titanium CP2, through an anodization process using an "organic" solution based on ethylene glycol containing ammonium fluoride and water. Then, the electrochemical stability in the Hank's solution of these "organic" nanotubes has been investigated for 15 days and compared to that of titanium nanotubes on a similar type of sample grown in an inorganic solution, containing phosphoric and hydrofluoridric acids. Morphological and crystallographic analysis were performed by using scanning electron microscopy (SEM) and X-Ray diffractometry (XRD) tests. Electrochemical measurements were carried out to study the stability of the nanotubes when are in contact with the biological environment. The morphological measurements revealed long nanotubes, small diameters, smooth side walls, and a high density of "organic" nanotubes if compared to the "inorganic" ones. XRD analysis demonstrated the presence of rutile form. An appreciable electrochemical stability has been revealed by Electrochemical Impedance Spectroscopy (EIS) analysis, suggesting that the "organic" nanotubes are more suitable for biomedical devices.

Electrochemical Evaluation of the Compact and Nanotubular Oxide Layer Destruction under Ex Vivo Ti6Al4V ELI Transpedicular Screw Implantation

“…The layer has average total thickness of length 1500 ± 100 nm. The use of high concentration of ethylene glycol and low pH of this electrolyte by the addition of a high concentration of fluoride allowed to form homogenous TNT in α and β-phases, which has not been obtained yet [14,15], or the layer was cracked [28].…”

“…Previous attempts to elaborate the mechanical degradation of TNT during implantation were carried out using flat foil [9,[14][15][16][17], on Ti, Ti6Al4V, and Ti6Al7Nb screws [19][20][21][22][23] using a nanoindenter test [37], wear test [6,36], or practical implantation of the screws to the bone. The implantation was carried out by inserting a screw into a bone and removing it, which caused double abrasion of the nanotube layer, and prevented TNT characterization inside the bone immediately after implantation.…”

“…The anodizing process significantly changes the corrosion potential of Ti6Al4V ELI from −0.337 V (bare) to −0.193 V for compact Ti6Al4V and to −0.129 V for nanotubular Ti6Al4V measured in 0.9% NaCl. This initial increase seems to be related to the formation and thickening of the oxide film on the metallic surface, improving its corrosion protection ability [15]. It should be mentioned that a more positive corrosion potential results in higher corrosion resistance of the coating, confirming the Bare Ti6Al4V ELI transpedicular screw exhibits a pronounced increasing from −0.40 V/Ag/AgCl towards more positive values until it does not reach a constant value of OCP −0.337 V/Ag/AgCl in 1200 s in 0.9% NaCl.…”

“…Park et al [14] and Acquesta et al [15] examined the growth behavior of nanotubular oxide on Ti6Al4V foil in glycerol solution containing NH 4 F. Anodized surfaces showed a wide distribution of nanotubular diameters and smooth side walls; nanotubes with smaller diameters formed across spaces were present between nanotubes with larger diameters. Interestingly, diameters of the nanotubular features increased toward the base of the nanotubes as opposed to the commonly observed tapered nanotubular morphology.…”

In-vitro corrosion of AZ31 magnesium alloys by using a polydopamine coating

“…As for other metals that are used to produce medical devices, i.e. titanium and its alloys [ [9] , [10] , [11] , [12] ], it is necessary to consider surface treatments to improve their corrosion resistance, antibacterial activity and cellular adhesion. A way to enhance devices surface properties is to use organic coatings.…”