Surface Analysis and Osteoblasts Response of a Titanium Oxi-Carbide Film Deposited on Titanium by Ion Plating Plasma Assisted (IPPA)

Abstract

Titanium is the most widely used material in orthopaedic and dental implantoprosthesis due to its superior physical properties and enhanced biocompatibility due to the spontaneous formation of a passivating layer of titanium oxides which, however, does not form good chemical bonds with bone and tends to brake exposing bulk titanium to harsh body fluids releasing titanium particles which may prime an inflammation response and a fibrotic tissue production. In order to avoid these possible problems and to enhance the biocompatibility of titanium implants, modifications of titanium surfaces by many different materials as hydroxyapatite, titanium nitride, titanium oxide and titanium carbide have been proposed. The latter is shown to be an efficient protection for the titanium implant in the harsh conditions of biological tissues and, compared to untreated titanium, acting like an osteoblast stimulation factor increasing in vitro production of proteins involved in osteogenesis. These results were confirmed by in vivo experiments in rabbits: implants covered by the titanium carbide (TiC) layer were faster and better osseointegrated than untreated titanium implants. The TiC layer was deposited by a Pulsed Laser Deposition (PLD) device which allowed only one deposition per cycle, shown to be unsuitable for industrial applications. Therefore the main objective of the present work was to replace PLD process with an Ion Plating Plasma Assisted (IPPA) deposition process, which is suitable for industrial upgrading. By this technique, nanostructured TiOx-TiCy-C has been deposited on titanium after sandblasting with 120 micron zirconia spheres. XPS analyses revealed the presence of about 33% carbon (50% of which is present as free carbon), 39% oxygen and 28% titanium (37% of which is bound to carbon to form TiC and 63% is bound to oxygen to form non stoichiometric oxides). Surface mechanical response of as-deposited coatings has been performed by nanoindentation techniques. Focused Ion Beam micrographs showed bigger differences on the obtained nanostructure compared to the PLD coating structure; in vitro tests confirm for IPPA produced coatings an improvement in stimulating osteoblasts to produce mRNA's of proteins involved in the ossification process, this latter case they resulted to be faster and more efficient. The proposed treatement is expected to improve the good results obtained by PLD, in vivo as well.

The Surface Anodization of Titanium Dental Implants Improves Blood Clot Formation Followed by Osseointegration

“…Both in vitro [38,39] and in vivo studies [40,41] reported a positive correlation between fibrin adhesion and surface wettability. Fibrin adhesion is influenced by different parameters: Blood drop extension, gravity of the drop, liquid characteristics, and thermodynamics aspects [42].…”

Graphitic carbon in a nanostructured titanium oxycarbide thin film to improve implant osseointegration

“…This sequence produced coating layers with unprecedented preliminary results in biological tests in vitro, which are predictive of good results in vivo and may have an industrial application. We have obtained full evidence that osteoblasts grown on the coated samples have a higher proliferation rate, an increased formation of filopodia, and a positively improved mRNA synthesis of proteins involved in bone formation, when compared to those grown on uncoated ones [6,7].…”

“…Starting from the good results reported in the literature for carbon species [4,[11][12][13] and on the basis of our results with TiC [5][6][7], we tried to build a nanostructured coating layer for implants, mainly composed of sp 2 carbon. Such a layer should be an ideal anchoring material both for Ti carbide, which can give hardness to the Ti implant, and for Ti oxides, which increases biocompatibility, along with graphitic carbon.…”

“…We have long been investigating compositional effects on thin layer deposits containing carbon as TiC, able to stimulate the integration of an orthopedic prosthesis into the bone tissue [5][6][7]. We tested two different techniques, Pulsed Laser Deposition (PLD) and Ion Plating Plasma Assisted (IPPA), to coat Ti prostheses.…”

“…However, the PLD deposition is unfit for industrial application, since the apparatus allows one to coat only one substrate at a time. In IPPA, first proposed by Mattox [8,9], and further developed by Misiano [10], the samples are introduced in a high-vacuum chamber containing a Ti target attached to a magnetron sputter source; a radiofrequency (RF) is applied to the sample holder, and ethylene is used as the reactive gas [6,7]. This sequence produced coating layers with unprecedented preliminary results in biological tests in vitro, which are predictive of good results in vivo and may have an industrial application.…”