Nanotubular Titanium Oxide Layers for Enhancement of Bone-Implant Bonding and Bioactivity

Abstract

Titanium and titanium alloys are frequently used in orthopaedic implants in load bearing situations because they possess favourable properties, such as a good ductility, tensile and fatigue strength, modulus of elasticity matching that of bones, low weight, and good biocompatibility. The drawback of Ti implants is their poor osseointegration and osteoconductive properties. The present paper describes the techniques to improve the bioactivity of titanium and enhance the bone-implant bonding ability by the electrochemical anodization to fabricate titania nanotube arrays (TiO 2 ). The naturally formed oxide layer has bio-inert character and does not readily form a strong interface with surrounding tissue. It has been proved that osseointegration of titanium implants can be improved by rough surfaces of Ti implants [1,2]. The nanotubular surface enhances adhesion, growth and differentiation of the cells. The nanotubular arrays increase the roughness of titanium implants on the nanoscale, providing the surface similar to that of a human bone. Bone-forming cells tend to adhere to the surfaces that are similar to natural bone both in chemistry and roughness. Nanotubular layers provide a high surface-to-volume ratio with controllable dimensions which are able to differentiation of mesenchymal stem cells into osteoblastic cells. Moreover, the anodized nanotubular arrays on titanium surface can be used as reservoirs for drugs (antiinflammatory, and improving bone-growth) with prolonged drug release ability. Also, there is possibility to further enhance bioactivity of titanium implant with nanotubular surface by hydroxyapatite deposition into the titania nanotubes which further promotes bone ingrowth. The application of nanotubular structures of oxide layers can be optimized taking into consideration some important parameters as osseointegration rate and interface strength determined by nanotube mean size and length. The paper critically reviews so far investigations focused on nanooxidation of titanium and titanium alloys. The numerical model of nanotubular arrays with the use of Finite Element Method (FEM) is proposed for an assessment of the load transfer and stress distribution under applied loading which could be a critical factor when considering the described application of nanotubes.

The Bioactivity and Photocatalytic Properties of Titania Nanotube Coatings Produced with the Use of the Low-Potential Anodization of Ti6Al4V Alloy Surface

“…This is also the case in biological systems, where a bioliquid surrounds the metal [ 13 , 14 , 15 , 16 , 17 ]. In the case of implants, the stoichiometric defects and low stability of this film can lead to their delamination and loosening [ 18 , 19 , 20 ]. Therefore, it becomes necessary to make the biocompatible coating permanently bond with the surface of implants.…”

Morphology and properties of nanotubular oxide layer on the “Ti–13Zr–13Nb” alloy

“…It might be discussed whether the oxide structure with long tubes may be susceptible to imposed stresses. This problem was considered early based on the Finite Elements Method (FEM) and a simple model of nanotubular structure [68]. It was shown that for a load imposed on the upper surface of nanotubes, being the sum of a specific structure weight and additional load ranging between 0 and 150 μN for a single nanotube, the von Mises stresses changed between 46 MPa and 1.61 GPa, and deformation between 0.19 and 17.9 nm.…”

<p>Anti-inflammatory drug-eluting implant model system to prevent wear particle-induced periprosthetic osteolysis</p>

“…26 Besides anti-inflammatory activity, 27 these systems have also shown several advantages in orthopedic applications such as improved biological activity in terms of osteoblasts attachment, proliferation, and differentiation. 28,29 Although the utilization of anti-inflammatory drug-eluting implants has shown some significant improvements, most of them are still in early research stage.…”