Organophosphorus compounds, like bisphosphonates, drugs for treatment and prevention of bone diseases, have been successfully applied in recent years as bioactive and osseoinductive coatings on dental implants. An integrated experimental-theoretical approach was utilized in this study to clarify the mechanism of bisphosphonate-based coating formation on dental implant surfaces. Experimental validation of the alendronate coating formation on the titanium dental implant surface was carried out by X-ray photoelectron spectroscopy and contact angle measurements. Detailed theoretical simulations of all probable molecular implant surface/alendronate interactions were performed employing quantum chemical calculations at the density functional theory level. The calculated Gibbs free energies of (TiO2)10–alendronate interaction indicate a more spontaneous exergonic process when alendronate molecules interact directly with the titanium surface via two strong bonds, Ti–N and Ti–O, through simultaneous participation common to both phosphonate and amine branches. Additionally, the stability of the alendronate-modified implant during 7 day-immersion in a simulated saliva solution has been investigated by using electrochemical impedance spectroscopy. The alendronate coating was stable during immersion in the artificial saliva solution and acted as an additional barrier on the implant with overall resistivity, R ~ 5.9 MΩ cm2.

In recent years, extensive studies have been continuously undertaken on the design of bioactive and biomimetic dental implant surfaces due to the need for improvement of the implant–bone interface properties. In this paper, the titanium dental implant surface was modified by bioactive vitamin D3 molecules by a self-assembly process in order to form an improved anticorrosion coating. Surface characterization of the modified implant was performed by field emission scanning electron microscopy (FE-SEM), attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR), and contact angle measurements (CA). The implant’s electrochemical stability during exposure to an artificial saliva solution was monitored in situ by electrochemical impedance spectroscopy (EIS). The experimental results obtained were corroborated by means of quantum chemical calculations at the density functional theory level (DFT). The formation mechanism of the coating onto the titanium implant surface was proposed. During a prolonged immersion period, the bioactive coating effectively prevented a corrosive attack on the underlying titanium (polarization resistance in order of 107 Ω cm2) with ~95% protection effectiveness.

Nitinol, as a shape memory alloy, is attractive material for medical implants and devices. Contrary to titanium, corrosion by releasing Ni 2þ ions occurs during a long-term contact of Nitinol with (physiological) solutions containing Cl À ions. In order to develop chemically/electrochemically stable surfaces and interfaces, Nitinol was modified by dodecylphosphonate (ÀOH and ÀCH 3 terminated) self-assembled monolayers (SAMs), which were characterized by XPS, PM-IRRAS and contact angle measurements. Strongly bounded well-ordered films of high homogeneity and resistance were synthesized. An innovative method that allows in situ study of influence of thermal annealing, following SAM formation, on their protecting properties in simulated (physiological) solutions is presented. Changes of structural sensitive impedance parameters were correlated with the changes in the interfacial layer. Effective thermal annealing greatly enhances the quality of the self-assembled alkyl-phosphonate films, which behave as non-ideal dielectrics, i.e., the solidjliquid interfaces formed represent the blocking contact preventing charge-transfer reactions.

No abstract

This study was focused on the synthesis and characterization of Si/Zr-based hybrid sol-gel coatings with and without the addition of cerium(III) ions. The coatings were deposited on aluminum aiming to act as an effective and ecologically harmless alternative to toxic chromate coatings. The chemical composition, structure, thermal properties and porosity of the non-doped and Ce-doped coatings containing various Zr contents were examined by Raman spectroscopy and photothermal beam deflection spectroscopy. The corrosion properties of the coated aluminum substrates were studied using AC and DC electrochemical methods in 0.1 M NaCl electrolyte solution. Barrier and protecting properties of the coatings were monitored upon long-term immersion in chloride solution using electrochemical impedance spectroscopy. The effect of cerium ions was twofold: on the formation of a more condensed Si−O−Zr network structure and on the formation of Ce-based deposits, which diminish the rate of cathodic reaction at the coating/metal interface. These effects acted synergistically and resulted in the creation of the coatings with effective barrier and active corrosion protection.