In particular, the nanotube morphology enhances the physical interlocking of osteoblast cells on the implant surface. It is known that the diameter of the nanotube is controlled through the anodization voltage. In the presence of different elements, the composition of the anodized layer is closely related to the metallic ratio of the alloy.
192,193] presented extensive research works on the development and morphological evolution of MONs, as well as the apatite-forming ability and corrosion behavior of Ti–Hf binary alloys for metallic biomaterial applications. Homogeneous Ti–Hf alloys have acicular α-phase microstructure, and the nanotubes grown on Ti-xHf alloys are in the anatase phase after crystallization, as shown in the figure. An improvement in the wear resistance of Ti–V alloy was observed due to the high hardness and low coefficient of friction of the MON structures.
They reported that the surface characteristics were dependent on the duration of the applied voltage. After anodizing the two-phase Ti–6Al–4V alloy, there were two different types of MONs on the surface of the alloy, which are the nanotubes formed in the α phase area and the irregular nanopores expanded in the β . -phase zone. The surface characteristics were influenced by the nature of the electrolyte and the applied voltage.
However, works on the physicochemical, mechanical and biological characteristics of the MONs on such quaternary alloys are limited [295]. Anodic oxidation of the Ti-Nb-Ta-Zr alloys gives unequal formation rates due to the unequal electrochemical oxidation rates of these elements in the alloy [146]. The anodizing behavior of the glassy forms of Ti-based alloys is still in the preliminary stages of investigation.
As soaked in the SBF, the sodium titanate nanofibers induce nucleation and development of the nanostructured HA coating on the implant surface [320]. As can be seen, there are large differences between the antibacterial mediation of the Ti-6Al-7Nb implant and the modified samples. The FESEM micrographs show that the cells are partially attached to the unprocessed Ti–6Al–7Nb after the first day of processing due to the inherent bioactivity of the substrate.
This suggests that the incorporation of GO into the nanotubular arrays improves the cytocompatibility behavior of the Ti-6Al-7Nb implant forming a future bioactive platform. One of the unexpected benefits of nanotubular coatings on the implant surface is that the nanostructured coating also resists Fig. The results confirmed that the TiO2 NTs in the valley of the Ti miniscrew threads are well preserved by the in vivo evaluation.
Clinical trials
Nevertheless, in the context of complex in vivo culture, negative effects of nanotubes on cell growth could be found if cell proliferation is undesirable. The influence of different diameters of nanotubes (30, 70 and 100 nm) on the process of connecting the bone to the surface of the implant after 1-5 weeks after installation was also studied in vivo. They demonstrated that a nanotubular structure with an average diameter of 70 nm at 20 V anodization is sufficient to provide optimal conditions for osteogenic differentiation of hASCs.
342] loosened Ti implant screws from animal models after implantation and found that the interaction of an implant with the adjacent bone increased significantly after the development of the nanotubes. On the contrary, the surfaces of the APH sample show coherent fracture patterns in newly formed bone at both steps. In numerous reports, damage to the nanotubes developed on the implant surface was detected using various techniques, for example, microscratches and nanoindentation.
343] investigated the damage to the surface of nanostructured Ti and Ti-6Al-4V dental implants after elimination from the tissues. It was found that the nanotubes formed on Ti-based screws were destroyed and loosened at the screw edge, whereas the other segments of the implant screw reserved the tubular configuration with appropriate incorporation with the animal tissue. This figure shows the effects of the combination of doped calcium phosphate coating with nanoscale surface modification of porous Ti on early stage osseointegration in a rat distal femur model.
This nanometer-scale surface modification can also be used in the stem areas of total hip or knee arthroplasty to develop different layers of MON to initiate early bone integration at the implant interface, which may ultimately result in improved healing [345]. The main contradiction is that the most favorable microstructural properties and geometry of nanotube arrays differ between different research groups. Taking advantage of this technology allows the production of an oxide layer with a maximum thickness of 5 μm, resulting in nanoroughness at the top of the implant with improved biocompatibility and resistance to corrosion and wear without significant changes in dimensions [333].
The anodization of titanium-based alloys for the production of medical implants consists of the following stages. The materials are then etched in a specific solution in which the soaking time for complete etching depends on the solution.
Future directions
Today, DOTIZE® technology, established by DOT America, is the leading anodizing process used in the industry to produce nanostructured implants. The processing period in this phase can be prolonged by the appearance of holes in the implants, as they are less accessible, and then the substances are excreted and thoroughly washed [333]. The sensor can measure the local temperature in the body, as an elevated temperature signals an infection before symptoms appear.
This benefits both patients and physicians by allowing therapy before infection, which can be complicated and expensive to treat [361]. 355] also recently presented smart bone plates that inspect fracture healing through microscale EIS sensors fabricated to calculate electrical properties of longitudinal fracture callus for the healing period in two different mouse fracture models. From the data of smart knee implants, the peak force as walking after total knee arthroplasty is about 1.8-2.6 times body weight and occurs in the middle of the tibial tray.
Enthusiasm for in vivo intelligent hip implants is currently related to applied research rather than clinical applications for specific patient care. In addition, intelligent implants can present some important information about the function of posture, movement and muscle activation in the biomechanics of the spine, which is very important, since the loading of the spine plays a key role in the disease process and the therapeutic process for low back patients. pain. Careful study of the loads on an intelligent fracture fixation device during weight bearing provides evidence of fracture strengthening and healing [363].
On the other hand, smart implants probably have a better future in the field of spinal and dental implants [367-372]. For this purpose, polymer-based sensors and Microelectromechanical Systems (MEMS) have desirable characteristics that correspond to the characteristics needed to measure the load on the body. This perspective recommends a systematic review of relevant biomechanics to identify relevant sensing factors, simultaneous treatment of sensing and potentiation features, and utilization of energy harvesting aimed at sensing and data transmission.
Moreover, the enhanced bioactive layer of inward growth of anodic nanotubular arrays on Ti and its alloys can provide superior adhesion of the nanotube layer to the substrate, thereby eliminating the problems of poor interfacial bonding of current ceramic coatings. Apart from the above explanations, intelligent orthopedic implantation for clinical practice is a challenging task because the integration of current sensor technology requires some substantial modifications to the implants [378].
Conclusions
Brentley, Nanotubular structure formation on Ti-6Al-4V and Ti-Ta alloy surfaces by electrochemical methods, Korean J. Ahmadian, Synthesis of selforganized mixed oxide nano tubes by sonoelectrochemical anodization of Ti-8Mn alloy, Electrochim. Nasiri-Tabrizi, Microstructural evolution and corrosion behavior of self-organized TiO2 nanotubes coated on Ti-6Al-7Nb, Ceram.
Nasiri-Tabrizi, A self-organized layer of TiO2 nanotubes on Ti–6Al–7Nb for biomedical applications, Surf. Nasiri-Tabrizi, Effect of microstructural evolution on the wettability and tribological behavior of TiO2 nanotube arrays coated on Ti–6Al–4V, Ceram. Choe, Occurrence of nucleation of titanium dioxide nanotubes on Ti–6Al–4V alloy using titanium oxide anodic technique, J.
Schmuki, Electrochemical formation of a self-organized anodic nanotube coating on the surface of a biomedical Ti–28Zr–8Nb alloy, Acta Biomater. Amiri, Optimized fabrication and characterization of TiO2–Nb2O5–Al2O3 mixed oxide nanotube arrays on Ti–6Al–7Nb, RSC Adv. Zhao, Preparation and capacitance of Mn-doped TiO2 nanotube arrays by Ti–Mn alloy anodization, J.
Wang, Homogeneous anodiesis TiO2 nanotube lae on Ti-6Al-4V alloy with improved adhesion strength and corrosion resistance, Advanced Material Interface. Guo, Maklike fabrication of superhidrophobic surfaces with low coarseness on Ti-6Al-4V substrate via anodization, Appl. Li, Fabrication of highly ordered TiO2 nanotube skids by anodizing Ti-6Al-4V alloy sheet, J.
Djenizian, Optical and electrochemical properties of self-organized TiO2 nanotube arrays of anodized Ti-6Al-4V alloy, Frontiers in Chemistry. Rajendran, Electrochemical behavior and effect of heat treatment on morphology, crystalline structure of self-organized TiO2 nanotube arrays on Ti-6Al-7Nb for biomedical applications, Mater. Li, Fabrication of Ti-Al-Zr alloy oxide nanotube arrays in organic electrolytes by anodization, J.
Basirun, Optimization of PVD conditions for electrochemical anodization growth of well-adhering Ta 2 O 5 nanotubes on Ti–6Al–4V alloy, RSC Adv.
