Papers by Keyword: Hydroxyapatite Coating

Abstract: We aim at revealing the damage behavior of HAp sprayed coating on the surface of acetabular cup subjected to cyclic loading using AE (Acoustic Emission) method and IR (Infrared thermography) methods. Fatigue test was conducted in SBF(simulated body fluid), and the displacement of acetabular cup embedded in simulated bone was measured by two cantilever pairs. Acoustic emissions from delamination or wear of HAp coating were also measured by AE method, and the temperature change due to friction and wear near the top was measured by IR method. The analysed result could estimate the process in which delamination occurs in the initial stage of test and then friction and wear occur. The rotation displacement of acetabular cup could be associated with cracking or delamination of the HAp sprayed coating, friction and wear at the interfaces between simulated bone and acetabular cup. The subsidence displacement of acetabular cup can be caused by collapse of the simulated bone accompanied by an increase in AE energy as well as an increase in dissipated energy. Combined analyses using AE method and IR method clarified that the inelastic damages in simulated bone at the top of acetabular cups could lead the acceleration of both normal and rotational displacement of the acetabular cup whereas interface damages also attributed to exaggerate the displacement by deteriorated fixation.

Abstract: α + β titanium alloys especially Ti-6Al-4V alloy have dominated implant industry over the years due to their high corrosion resistance, strength, and flexibility. However, their high modulus (110GPa) compared to the human bone (18-30GPa) results in aseptic loosening of implants. Hydroxyapatite (HA) coating on Ti-6Al-4V alloys has been used to mitigate these demerits, nevertheless, more still need to be done. Hence, the present study aims at developing a natural and economical bioceramic coating on low modulus Ti-13Nb-13Zr alloy substrates using plasma spraying technique for biomedical applications. The bioceramic used was natural HA derived from fish scales (FsHA) and FsHA doped yttria stabilized zirconia at (10-20 wt.%). FsHA/YSZ powders and the coated samples were examined by XRD and SEM/EDX and the surface roughness, microhardness and corrosion resistance of the uncoated substrate and coated samples determined. The XRD pattern showed good crystalline FsHA/YSZ powders for all the compositions while the microstructure of the coatings revealed a fine splat lamellar morphology with partially melted and non-melted FsHA particles along with evenly dispersed Zr particles within the coating matrix for the FsHA/YSZ coatings. The maximum surface roughness (4.215 µm) was found with the FsHA coating while FsHA/YSZ coatings presented the highest hardness values (492.5-536.9 Hv) compared to the FsHA coating (467.8 Hv) and the uncoated substrate (385.9 Hv). Similarly, the corrosion resistance of the Ti-13Nb-13Zr alloy was significantly improved with the deposition of FsHA/YSZ bioceramic coatings.

Abstract: Dogs underwent high-frequency automated tibia lengthening with the Ilizarov apparatus over a 1.8-mm hydroxyapatite-coated intramedullary titanium wire. Daily distraction was 3.0 mm with a fraction of 0.125 mm/h and continued ten days. The regenerate was well vascularized, had zonal structure and was of normal or hyperplastic type to the end of distraction. Osteogenesis was fast and complete. The wire served for both mechanical and biological reinforcement of the bone callus and provided reduction of external fixation time. Mean consolidation time with the apparatus on the limb was 13.83±4.02 days. Overall, external fixation index was 10.5 days/cm and 4.8 days/cm in the consolidation phase.

Abstract: Titanium and its alloys are standard for orthopedic prosthetic devices, due to their good mechanical properties and biocompatibility. However, bioactivity on the implant surface needs to be improved to achieve an optimal osseointegration process. Metal implants are often coated by hydroxyapatite because they have a chemical composition and crystal structure similar to apatite in the human skeletal that suitable for bone reconstruction. The focus of this research is on surface treatment designed to promote better biological responses through hydroxyapatite layers. Also combining the acid etching treatment of Ti-6Al-4V and the electrophoretic coating process of the hydroxyapatite to obtain stronger mechanical interlocking interface. Hydrofluoric-Acid treatment conducted in various time. Then, coated with nanosized hydroxyapatite through electrophoretic deposition at 15V voltage for 10 minutes. Scanning Electron Microscopy and Contour measurements were performed to show the surface topography indicating the formation of surface contours with increasing surface roughness parameters in accordance with the time of the etching process. The contours on the surface of the substrate induce the mechanical interlocking of the surface so that the results of hydroxyapatite deposition optimal at the time of etching 5 minutes

Abstract: This study aims at experimentally revealing the effects of damages/fractures in HAp coating layer of acetabular cups on loosening behavior of the acetabular cups. Aseptic loosening is occurred due to degradation of fixing force of acetabular cups by biological effects or mechanical loading. However, effects of mechanical loading on loosening behaviour have not been observed yet. In order to simulate cyclic loading conditions of gaits, a testing system which can load entire components of joint including acetabular cups and stem parts was designed. Moreover, by applying two positions of AE sensors during fatigue testing, it was possible to observe the damage behavior of HAp coating. AE measurement detected different failure modes of HAp coating, which were locally occurred at an edge part of the acetabular cup due to stress singularity at that region. In the cases of changing fixation angles, even though damages in simulated cancellous bone surrounding acetabular cups were less occurred, extents of rotational displacements were compatible with the one in an original fixation angle.

Abstract: Magnesium corrosion has been identified as the main challenge that limits the implementation of this material into various applications, including biomaterials. Simple chemical conversion coatings have been employed in order to minimize the corrosion problems. In this paper, hydroxyapatite-coated magnesium were fabricated by using chemical conversion coatings and the corrosion behaviour of the coated samples were evaluated inside different corrosion media (Ringers, SBF, and PBS) by using electrochemical impedance spectroscopy (EIS). EIS reveals the electrical properties of the coatings towards corrosion attack by the corrosion media. The corrosiveness of the tested solutions was given by (from least to the most aggressive): PBS ˂ SBF ˂ Ringers.

Abstract: In this work a two-step thermochemical deposition of calcium phosphate from ostrich eggshell on titanium surface was performed. After the deposition, the coatings were immersed into 0,1M KOH solution in order to favoring HA precipitation. The coatings were characterized by scanning electron microscope with field emission gun (FEG-SEM), and X-ray diffraction (XRD) analysis. Bioactivity assessment was performed in cell culture media, McCoy 5A medium, for 14 days. XRD patterns showed brushite/monetite as the phases present at first deposition step; in the second deposition step XRD patterns indicated HA phase peaks on titanium surface. After 14 days on McCoy 5A medium, brushite/monetite coatings revealed bone-like apatite precipitation, showing bioactivity; hydroxyapatite coatings showed a surface modification but no significant bone-like apatite precipitation, thus lower bioactivity. The use of ostrich eggshells as an alternative source to obtain bioactive calcium phosphate coatings showed to be effective.

Abstract: The open fracture of femur has been experimentally modeled on dogs. A comparative analysis of the consolidation process under the osteosynthesis with the Ilizarov apparatus (the first group of animals) and the combination of osteosynthesis with the Ilizarov apparatus and intramedullary reinforcement with hydroxyapatite-coated wires (the second group of animals) has been carried out. Fracture consolidation in the second group has been confirmed morphologically in 2-3 weeks without signs of fibrous and cartilaginous tissue. In case of osteosynthesis with the Ilizarov apparatus only, the process of reparative regeneration was slowed down.

Abstract: Additive Manufacturing (AM) - is a technology that fabricates the parts directly from 3D CAD model without the need of any process planning. The convergence of AM and life science has evolved into a new paradigm called Bio-Additive Manufacturing (BAM). In this paper, Hydroxyapatite (HA) powder was coated over the customized implant, which will serve as a good candidate for bone substitutes due to its chemical and structural similarity to bone. Computer Tomography (CT) scan data of human tibia bone was collected and stacked in MIMICS image processing software, which converts it into 3D data, then implant was fabricated using Selective Laser Sintering (SLS), an AM technique with polyamide powder. Hydroxyapatite powder was synthesized by wet chemical process and coated over implant using plasma spray coating machine. This coating will produce an intermediate region between the bone and the implant, which will stimulate the tissue growth and bone contact. Micrograph of coated and uncoated implant was analyzed using SEM and EDX. For In-Vitro study human mesenchymal cell was cultured over the coated implant. The viability and proliferation of the cells was studied by examining the morphology of the cell. Thus the implant was fabricated using SLS technique and coated with hydroxyapatite powder which exhibits a favorable and good response to enhance tissue growth.

Abstract: A hydroxyapatite coating on the porous titanium surface was prepared by NaOH-treated and heat treatment followed by immersing into a supersaturated calcium phosphate solution. It is found that the porous titanium was in an open-cell microstructure. The morphology, element content and phase composition of the hydroxyapatite coating were also analyzed. The cytotoxicity of porous titanium surface were tested. The results showed the hydroxyapatite of porous titanium surface by NaOH-treated and heat treatment was attached uniformly and had a certain thickness after immersion into the simulated body fluid (SBF) solution for 5 days, the hydroxyapatite coating was formed after immersion into the SBF solution for 12 days, it demonstrated good biocompatibility and enhancement of biological activity, it was conducive to the proliferation and adhesion of osteoblasts.