Effects of High-Concentration Alkali Treatment on Surface Bioactivity of Porous Titanium

Various surface treatment methods have been used to modify the surface activation of dense titanium. In this study, a high concentration of sodium hydroxide solution was used to treat porous titanium prepared by adding porous agent at different times. The results of the study showed that after alkali treatment, porous titanium was implanted into the back muscle of the dog and the implanted sample was taken out for bone formation protein-2 enzymatic immunoassay after 6 months. The porous titanium inner wall has been covered. The microstructures vary with the treatment time. The treated surface can induce the formation of hydroxyapatite deposition and promote the expression of BMP-2, which shows good bone induction. High concentration alkali treatment of porous titanium, the method is simple, can shorten the HA formation time, can effectively activate porous titanium inner and outer surfaces, is an effective method to prepare bioactive porous titanium.

Dough Extrusion Forming of Titanium Alloys—Green Body Characteristics, Microstructure and Mechanical Properties

Titanium and its alloys are widely used in structural applications owing to superior mechanical properties and corrosion resistance. In the present study, a simple powder metallurgy-based process is developed to fabricate dense components through formation of dough under ambient condition using Ti6Al4V powder along with chitosan powder as dough forming additive and acetic acid as solvent. The prepared samples had ∼66±1.7% green density and 97.3±2.1% sintered density of the theoretical value. The microstructure of Ti6Al4V was investigated using scanning electron microscopy (SEM) combined with energy-dispersive X-ray (EDX) spectroscopy. Micro-CT analysis was carried out for distribution of defects and their influence on flexural strength and microhardness was assessed as well. The prepared green samples had uniform particle distribution that resulted in minimum deformation after sintering. Assessment of mechanical properties revealed that the values of hardness and flexural modulus for sintered samples were comparable to the reported values of Ti6Al4V components prepared using other process. Therefore, the developed method of dough forming for dense titanium components using powder metallurgy route is a simple and viable alternative.

Titanium Substrate Surfaces Coated with Hydroxyapatite by Magnetron Sputtering

The deposition of hydroxyapatite coatings on titanium via sputtering techniques has been quite studied on commercial dense substrates, for use as a biomaterial. In this work, porous titanium samples produced by powder metallurgy and commercially dense titanium sheet, used as control, were used as substrates. The coatings were deposited by radio frequency magnetron sputtering using a hydroxyapatite target in argon atmosphere with different deposition times. Samples characterization was performed by Optical Microscopy, Scanning Electron Microscopy/Energy Dispersive Spectroscopy and low-angle X-ray Diffraction. Hydroxyapatite coating depositions were obtained on both titanium substrates. The results indicated the potential of this methodology for titanium substrates with homogeneous hydroxyapatite coatings.

Biomimetic Creation of Surfaces on Porous Titanium for Biomedical Applications

Titanium and titanium alloys have been extensively studied for many applications in the area of bone tissue engineering. However, dense titanium is prone to lead into aseptic loosening due to their high elastic modulus compared to natural bone. One way to lower the elastic modulus is to produce a porous structure of the metallic alloy by adjusting its porosity. Another concern is the bioinertness of titanium that have no direct chemical bonding with surrounding tissue. One approach to improve the healing process is the application of a calcium phosphate coating onto the surface of biomedical devices and implants. Biomimetic creation of surface using alkali heat treatment with silica addition was employed in this study. The porosity of the samples ranges from 60% to 70%. It was demonstrated that the biomimetic methods are suitable for inducing apatite on the titanium alloys surface.

Multiscale Design and Multiobjective Optimization of Orthopedic Hip Implants with Functionally Graded Cellular Material

Revision surgeries of total hip arthroplasty are often caused by a deficient structural compatibility of the implant. Two main culprits, among others, are bone-implant interface instability and bone resorption. To address these issues, in this paper we propose a novel type of implant, which, in contrast to current hip replacement implants made of either a fully solid or a foam material, consists of a lattice microstructure with nonhomogeneous distribution of material properties. A methodology based on multiscale mechanics and design optimization is introduced to synthesize a graded cellular implant that can minimize concurrently bone resorption and implant interface failure. The procedure is applied to the design of a 2D left implanted femur with optimized gradients of relative density. To assess the manufacturability of the graded cellular microstructure, a proof-of-concept is fabricated by using rapid prototyping. The results from the analysis are used to compare the optimized cellular implant with a fully dense titanium implant and a homogeneous foam implant with a relative density of 50%. The bone resorption and the maximum value of interface stress of the cellular implant are found to be over 70% and 50% less than the titanium implant while being 53% and 65% less than the foam implant.