In this review, we present our research work on sputtering deposition of metal-transition oxide films on stainless steel substrates as candidates for dental implants. Titanium, zirconium, tantalum and niobium oxides were produced and their corrosion resistance has been evaluated using potentyodynamic polarization and electrochemical impedance spectroscopy using physiological solutions. Similarly, the oral bacterial attachment and biofilm formation on the different surfaces was studied, as well as the effect of the bacterial attachment on the electrochemical response. The biocompatibility of the coatings have also been evaluated directly in-vitro using osteoblast-like cells or indirectly by studying the protein adsorption on the surfaces, which dictates the later cell-surface interactions. Moreover, the effect of the film thickness, structure, surface energy and topography on the functional response has also been analyzed in order to determine what is important for the future development of biomedical coatings.

In 2003, 220,000 Total Hip Replacements (THR) were performed and this figure is expected to rise. Of the surgeries performed, 8% of the THR’s resulted in infections and required revisions. Biofilms are matrices of bacteria enveloped in proteins and polysaccharides which evade the immune system. The goal of this work is to inhibit bacterial colonization with a silver nanoparticle infused linseed oil coating on Ti90Al6V4 alloy which could prevent biofilm formation and avert infection.

Recent work on Y-TZP materials (a dental replacement material) has shown that the effect of pH and exposure time may change the erosion-corrosion mechanism on the surface. Wear and phase transformation maps have been generated for the material. The results have identified that at low pH values, and longer exposure times, the wear rate significantly decreases in such conditions.

In this work, a range of Ti based PVD coatings on Y-TZP were evaluated under combined erosion-corrosion conditions. Wear maps were produced using the results. The maps indicate the mechanisms of wear and the conditions under which the coatings may modify the wear rate in such environments.

The benefits of superhydrophobic surfaces are commonly seen in the biomedical field. For example, bacterial adhesion to biomedical implant surfaces can be greatly reduced if the surface is superhydrophobic. Since the superhydrophobicity of water repellant leaves in nature is often attributed to their microstructures combined with the presence of water repellant waxy nanocrystals on these microstructures, mimicking nature to create micro-/nano-scale topography and chemistry on material surfaces to render superhydrophobic surfaces has attracted much attention. This poster reports the fabrication of micro and nano-textured surfaces on stainless steel surfaces to produce superhydrophobic surfaces for possible use in biomedical applications. Various fabrication techniques, including sandblasting, thermal evaporation, aluminum induced crystallization (AIC) of amorphous silicon (a-Si), and deep reactive ion etching C₄F₈ passivation, were investigated to change the topography as well as chemistry of the stainless steel surfaces. The topographies resulting from these surface modifications were analyzed through scanning electron microscopy and surface profilometry. The wetting properties of these surfaces were characterized by water contact angle measurement. This study determined that the most effective process for creating superhydrophobic surfaces is to perform AIC of a-Si on plain stainless steel, leading to a water contact angle of more than 160°. The results of this study also showed that sharp nano textures fabricated by AIC of a-Si produced higher water contact angles than smooth nano textures produced by thermal evaporation.

Titanium has been widely used to fabricate dental implants due to its resistance to corrosion and biocompatibility. However, during mastication, implants are exposed to mechanical, chemical and microbiological actions, which can be considered a continuous complex degradation process. Studies have looked at chemical corrosion of titanium; however, very few have reported on the effect of combined chemical, mechanical and microbiological actions, which resemble the oral environment. A new multi-disciplinary research area, tribocorrosion, can address such issues.

This study aimed to investigate the tribocorrosive nature of titanium in artificial saliva (pH 6.5) with the presence of Escherichia coli lipopolysaccharide (LPS). A total of 24 titanium discs, 12-mm diameter and 7-mm thickness, were used. Samples were divided into 8 groups (n=3) as a function of different titanium type (commercially-pure titanium and Ti-6Al-4V alloy) and LPS concentration (0, 0.15, 15 and 150µg/ml).The sliding duration (2000 cycles), frequency (1.2Hz) and load (20N) parameters were selected to simulate the oral environment and mastication process. Electrochemical impedance spectroscopy was conducted before and after tribocorrosion to comprehend the changes in the corrosion kinetics. Worn surfaces were examined using white-light-interferometry microscopy and scanning electron microscopy. Total weight loss (K_wc) and roughness values were calculated. Data were analyzed using one-way ANOVA, and Tukey’s HSD and paired-T tests were used where appropriate (α=.05).

LPS influences the tribocorrosive behavior of both titanium types. LPS statistically accelerated the ions exchange between titanium and saliva, and reduced the resistance of titanium surface against corrosion (p<.05). Sliding tends to decrease the protectiveness of titanium surface against corrosion. In general, Ti-6Al-4V alloy exhibited better corrosion behavior. Both titanium types showed similar K_wc values (p>.05). LPS increased the weight loss of commercially-pure titanium (p=.041), and the roughness values (p<0.001). The study clearly indicates that LPS negatively affect the corrosion/wear behavior of titanium, which might increase the failure rate of dental implants.