Pitting corrosion behavior of SS-316L in simulated body fluid and electrochemically assisted deposition of hydroxyapatite coating

In-vitro biocompatibility evaluation of cast Ni–Ti alloy produced by vacuum arc melting technique for biomedical and dental applications

The investigated cast Ni50–Ti50 shape memory alloy was prepared using a vacuum arc furnace. The cast samples were subjected to in-vitro biocompatibility studies according to ISO 10993-12:2004, and compared to other samples Ni–Ti orthodontic wires commercially available at the dental market. The cast samples were hydroxyapatite-coated using the electrodeposition technique. The effect of surface treatment on the coating quality was addressed. The hydroxyapatite-coated samples were investigated using electrochemical impedance (EIS) and potentiodynamic techniques. Coated samples were also examined using a scanning electron microscope to inspect the coating morphology. Cytotoxicity tests on MG63 and H9C2 cell lines showed the safety and biocompatibility of the cast NiTi alloy, with a direct relationship between the incubation period of the tested samples and cell viability. Well-adhered hydroxyapatite coating was obtained on the surface-treated NiTi samples using the electrodeposition technique. EDS analysis showed a hydroxyapatite coating having a calcium to phosphorus ratio close to that of the natural bone. Electrochemical tests indicated that the highest corrosion resistance was obtained for the uncoated samples followed by the anodized sample and finally the hydroxyapatite-coated samples due to their high porosity.

Electrodeposition of Calcium Phosphate Coatings on Metallic Substrates for Bone Implant Applications: A Review

This review summaries more than three decades of scientific knowledge on electrodeposition of calcium phosphate coatings. This low-temperature process aims to make the surface of metallic bone implants bioactive within a physiological environment. The first part of the review describes the reaction mechanisms that lead to the synthesis of a bioactive coating. Electrodeposition occurs in three consecutive steps that involve electrochemical reactions, pH modification, and precipitation of the calcium phosphate coating. However, the process also produces undesired dihydrogen bubbles during the deposition because of the reduction of water, the solvent of the electrolyte solution. To prevent the production of large amounts of dihydrogen bubbles, the current density value is limited during deposition. To circumvent this issue, the use of pulsed current has been proposed in recent years to replace the traditional direct current. Thanks to breaking times, dihydrogen bubbles can regularly escape from the surface of the implant, and the deposition of the calcium phosphate coating is less disturbed by the accumulation of bubbles. In addition, the pulsed current has a positive impact on the chemical composition, morphology, roughness, and mechanical properties of the electrodeposited calcium phosphate coating. Finally, the review describes one of the most interesting properties of electrodeposition, i.e., the possibility of adding ionic substituents to the calcium phosphate crystal lattice to improve the biological performance of the bone implant. Several cations and anions are reviewed from the scientific literature with a description of their biological impact on the physiological environment.