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Application of artificial neural networks for optimization of plasma spraying parameters was considered. Artificial neural networks were used to select realistic parameters of titanium and hydroxyapatite powder coating of titanium products. For titanium coatings, the optimal arc current was found to be 380-450 A; optimal spraying distance, 100-150 mm; optimal titanium powder dispersity, 40-90 μm. Similar optimal ranges were obtained for hydroxyapatite coatings. The goal of the optimization wais to maximize the coating adhesion to the substrate and to improve its porosity.

Hydroxyapatite (HA) coated carbon/carbon composites (CC) is a potential material for orthopedic application because of the combination of good biocompatibility and mechanical properties. In this work, we synthesize a tree-planting interface which is composed of holes formed by micro-oxidized CC substrates and carbon nanotubes (CNTs) to achieve a high bonding strength of HA coating. The holes include annular gaps between carbon fiber and pyrolytic carbon, as well as irregular holes formed by oxidized pyrolytic carbon. The CNTs can grow inside the holes and extend into the HA coating. As a result, the bonding strength of HA coating with tree-planting interface achieves 11.14 ± 0.78 MPa. It increases by 181.3% comparing with the HA coating on CC without interface (3.96 ± 0.30 MPa). The in-vitro bioactivity evaluated by the response of mesenchymal stem cells (MSCs) shows promotions of cell proliferation and cell activity with increasing culture time. After applied with tree-planting interface, the HA coating with strong bonding and good bioactivity may be applied in orthopedic field in the future.

Purpose The purpose of this study is to obtain an effective implant with porous structures on its surface, named porous-surfaced implant, which helps to improve the overall stability of the implant and promote the combination of implant and alveolar bone. Design/methodology/approach Porous-surfaced implants with a porosity of 16%, 21%and 32% were designed and the effect of porosity on the strength of the implant was analyzed by ABAQUS software. Porous-surfaced implants with different porosity were printed by selective laser melting and the surface morphology was observed. Animal experiments of implants with porous structures and coating were carried out in healthy beagle dogs. The experimental group was treated with hydroxyapatite coating and the control group was not treated. Bone volume (BV) and total volume (TV) of the implant surface of the experimental group and control group were calculated by Skyscan CTvol software. Findings With the increase of porosity of porous-surfaced implants, the neck stress of the porous-surfaced implants increased and their strength decreased. In addition, in animal vivo experiments, the ratio value of BV to TV of the porous-surfaced implants was between 55.38% and 79.86%, which was the largest when the porosity of porous-surfaced implants was 16%. The internal and surrounding bone formation content of porous-surfaced implants with hydroxyapatite coating was higher than porous-surfaced implants without coating. Originality/value The results of this study show that the pores on the surface of implants can be filled with the new bone and porous-surfaced implants with 16% porosity provide better space for the growth of new bone. The porous structures with hydroxyapatite coating are beneficial to the growth of new bone around implants. The results of this study are helpful to improve the overall stability of implants and to promote the combination of implant and alveolar bone.

Magnesium and its alloys are promising materials that have potential mainly in the field of transport (e.g. automobile industry) and medicine (e.g. orthopedic implants). Their disadvantage is poor corrosion resistance, which limits their wider use in practice. Therefore, surface treatment by various methods is performed in order to improve corrosion protection. The preparation of a superhydrophobic coating is an interesting approach because the hydrophobic coating minimizes contact of the corrosion medium with the magnesium substrate. In this work, the hydrothermally prepared hydroxyapatite coating on AZ31 magnesium alloy was superhydrophobized by myristic acid. The prepared coatings were characterized by determining contact angle and surface analysis using a scanning electron microscopy with energy dispersive spectroscopy and Fourier transformed infrared spectroscopy. The corrosion resistance of modified surfaces was examined by potenciodynamic polarization in 3.5 % NaCl.

Excellent osseointegration of biomaterial is very important for the stability of dental implants in clinical field. Much has been learned about this concept and significant improvements on the design and surface modification of implants have been done in the implant dentistry.

Magnesium (Mg) alloys are receiving increasing attention as biodegradable implant materials in recent years. However, their low corrosion resistance and fast degradation in the physiological environment remain challenges for a widespread application. Hydroxyapatite (HA) coating on Mg alloys can enhance their corrosion resistance, biocompatibility, and bioactivity of the Mg alloy substrates since the compositions of HA are similar to those of the hard tissue of natural bone. This review analyzes the challenges of Mg alloys for biomedical applications, the fundamental requirements for biodegradable metals, and the corrosion mechanisms of Mg alloys in the physiological environment. The benefits of HA coatings on Mg alloys, the most commonly used surface coating techniques and their advantages and limitations, and the in vitro and in vivo performance of Mg alloys with and without surface coatings are comprehensively elucidated. Multistep processes such as alkali treatment and then HA coating by electrochemical deposition on Mg alloys appear to be necessary to achieve a satisfactory surface coating on Mg alloys, which has been demonstrated to have the potential to improve the degrading behavior, bioactivity and biocompatibility. Multifunctional coatings are most effective in achieving safe and bioactive Mg alloy surfaces for promising biodegradable implant applications.

Hydroxyapatite (HA) coating was deposited on commercially pure Ti to improve its biocompatibility as a biomedical implant material. The HA layer was deposited by the electrophoretic deposition (EPD) method. The processing parameters controlled the HA structure. In this research, the applied voltage was varied 20, 30, and 40 V to optimize a free-crack layer. The current output during EPD at 20 V was in the order of 10-5 A/cm2. A higher current density in the order of 10-4 A/cm2 was obtained at 30 and 40 V. The coating formed at 20 V was relatively free of crack. A high number of cracks began to observe in the layer formed at 30 V, while only a few cracks were revealed on the layer formed at 40 V. The average thickness of the HA layer increased slightly with applied voltage. The thickness was approximately 40±5 µm, as observed by an optical microscope. The optimum voltage to produce a thick HA layer with a small number of cracks was at 40 V.

Metallic implants are extensively used to treat a spectrum of orthopaedic related disorders. Among the metals, titanium and its alloys are considered most excellent and indispensable material for the production of orthopaedic implants regarding their sterling mechanical properties and exceptional biocompatibility. Recently, rapid progress in developing non-toxic titanium-based alloys with modulus similar to that of human bone has inspired researchers globally. Thus, many studies have focused on titanium alloys, their heat treatment processes and several processing technologies. Additive manufacturing has been designed to enhance their mechanical properties tailored towards biomedical applications. Inarguably, the need to further improve on the implant’s biocompatibility with bodily environment for optimum service life is of great importance. Hence, hydroxyapatite coating provides an improvement as demonstrated by in vitro as well as in vivo studies. The present article critically reviews, based on recent scientific literatures, the progress made thus far in the development of titanium-based alloys, additive manufacturing processes and their heat and surface treatments tailored towards biomedical applications.

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.

This study aims to investigate the effect of the electrophoretic deposition process (EPD) of natural HA (extracted from bovine bones) with various particle size on Ti-29Nb-13Ta-4.6Zr (TNTZ) coating surfaces. HA particles were refined from bovine bone powders using planetary ball mill and then sieving to separate the particle based on its size. The maximum size according to sieving mesh size is #25 µm, #63 µm and #125 µm. The coating process was conducted by using EPD apparatus with voltage and time process 10V and 5 minutes, respectively, for each sample. The coating layer morphology was observed with Stereo Microscopy, Scanning Electron Microscopy (SEM) and the thickness was measured with Thickness Gauge. The result shows that the size of the particle determines the coating layer characteristics. The best of HA coating quality according to the implant coating standard is obtained for the 25 µm particle size with the surface coverage is 99%. The thickness is 121 µm and the ratio of chemical composition Calcium and Phosphor Ca/P) is 1,49%. These may be concluded that, on the point of view physical characteristics, natural HA from bovine bone has potential enough as a coating layer to improve the bioactivity implant for biomedical application. However, the mechanical characteristic of the layer is still needed to determine the strength of coating layer for avoiding delamination during application.

Hydroxyapatite (HA) is potentially used as a coating material for titanium alloys to improve their bioactivity and then enhancing the osseointegration characteristic of metal implants for orthopedic application. Electrophoretic Deposition (EPD), one of the coating methods that is widely applied for coating metal because of its simplicity and relatively low cost, is chosen for coating metal implants. HA coating layer quality can be controlled by adjusting applied voltages and coating time of the EPD process. However, the optimum voltage and exposing time has not yet been known for new type titanium implant such as Ti-12Cr and TNTZ. This work is, therefore, focusing on the effect of applied voltage and coating time on the mass growth, HA coating thickness, and surface coverage that can be produced on the surfaces of both alloys, and also on the conventional titanium alloy, Ti6Al4V, for comparison. The result of this work showed that there is a significant influence of the titanium alloy type on the HA layer performances. However, it is necessary to choose a suitable voltage and to expose time for producing a sufficient coating layer that meets the standard of orthopedic implants.

Finite element analysis (FEA) has been proven to be a precise and applicable method for evaluating dental implant systems. This is because FEA allows for measurement of the stress distribution inside of the bone and various dental implant designs via simulation analysis during mastication where such measurements are impossible to perform in-vitro or in-vivo experiment. That is why the relationship between implant design and load distribution at the implant bone interface is a crucial issue to understand. This research study focuses on a static simulation and bonding strength for PLA/HA coating on V thread design of dental implant using three-dimensional finite element. The average masticatory muscle that involves in human biting such as X, Y and Z direction will be used to simulate force with load condition of 17.1N, 114.6N and 23.4N respectively. Based on result obtained, the coated dental implant model is more compatible than uncoated model due to lower maximum stress which is reduce about 16%. The coated model also shows lower deformation and higher bonding strength. Outcomes from this research provide a better understanding of stress distribution characteristics that would be useful in order to improve design of dental implant thread and evaluation of the PLA/HA bonding strength applied.

Both tensile and shear adhesion strength tests were performed to evaluate interfacial strength between hydroxyapatite coatings on titanium alloy substrates subjected to anodization and heat treatment prior to deposition as well as post-deposition heat treatment. Results of the tensile adhesion strength tests were influenced by the size of the blasting media and the processing of pre- and post-heat treatments but not influenced by anodization. The finite element method (FEM) analysis of stress distribution during the shear adhesion strength test was also performed to evaluate the degree of stress singularity. The results show that the stress singularity parameters were dominant factors of stress distribution in the stress singularity fields, and they were also expected to influence the “essential” interfacial strength. In addition, the size of the blasting media had the same influence on the shear and tensile adhesion strength tests. This suggests the possibility of estimating tensile adhesion strength using the results of shear adhesion strength.

Composite materials with a biologically active coating are created. The morphology of a newly formed surface is studied by scanning electron microscopy, as well as the Brunauer–Emmett–Taylor method. The adhesive strength of the hydroxyapatite coating is determined by centrifugal separation. As a result of the studies, the most promising method of deposition, the best shape of the coating material and the optimal porosity of the titanium scaffold are established.

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

Hydroxyapatite (HA) was obtained from eggshells using selective thermal treatment. The properties like mechanical strength, biocompatibility and adhesion of hydroxyapatite were enhanced by adding titanium oxide (TiO2) and aluminum oxide (Al2O3) in two different compositions (HA-10TiO2-10Al2O3 (H10T10A) and HA-20TiO2-20Al2O3 (H20T20A)). Mechanical performance of the detonation sprayed H10T10A and H20T20A hybrid ceramic powders on AISI 304L SS steel were estimated by pin-on-disc apparatus. A load of 110 N was applied constantly over the pin which slides a linear distance of 2700 m at a linear velocity of 1 m/s at atmospheric temperature. The present investigation shows that the specific wear rate of bare AISI 304L SS was 8.23 × 10−5 mm3/N-m, while those of H20T20A and H10T10A coatings were 0.402 and 0.844 × 10−5 mm3/N-m respectively. The coatings and coating powders were characterized by SEM, XRD and FT-IR, XRD techniques respectively. The results showed that H20T20A coating has higher wear resistance in comparison to HA10T10A.

We study the influence of the voltage (100–180 V) of plasma-electrolytic oxidation on the formation of hydroxyapatite coatings on VT1-0 commercially pure titanium in alkaline electrolytes (hydroxyapatite + 1 M potassium hydroxide). We analyze the physical and chemical characteristics of hydroxyapatite coatings (phase composition, thickness, porosity, and surface roughness) and establish the conditions of formation of coatings for which the ratio Ca/P is close to the values typical of biological hydroxyapatite.

A new preparation method of hydroxyapatite coating was proposed for the conservation of gypsum crust on historic limestones. by successive introduction of calcium and phosphorus sources into the crust by surface permeation. Due to the formation of hydroxyapatite coating, both surface protection and integral consolidation of the gypsum crust can be accomplished. The performances of the hydroxyapatite coating were investigated by scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffractometry, water stability, capillary water uptake, color difference and adhesion strength test. The experimental results indicated that the hydroxyapatite coating would be a good solution for the conservation of the gypsified historic limestone surface.

Medical pure titanium (Ti) shows excellent chemical stability and mechanical properties in clinical uses, but its initial fixation with host bone, when implanted, is usually delayed owing to the bioinert Ti surface. In this study, we fabricate the hydroxyapatite (HA)-coated titanium by three steps reactions: (1) to form an activated O2− layer by immersing Ti substrate into an alkaline solution such as NaOH, (2) the O2− bonds with Ca2+ to form Ca–O–Ti bonding, in which O plays the part of bridge materials between Ca and Ti substrate and (3) the conversion of Ca–O–Ti samples to HA-coated Ti samples by immersion into Na2HPO4 2 M at 180 °C for 48 h using hydrothermal methods. The effect of different phosphate solutions (NaH2PO4 2 M and Na2HPO4 2 M solution) and hydrothermal treatment time (24 and 48 h) on the characteristic of hydroxyapatite coating titanium substrate is also investigated using the optical microscope, thin film XRD and SEM/EDX. The HA-coated Ti samples fabricated by immersion into Na2HPO4 2 M at 180 °C for 48 h show fiber HA covering Titan substrate with a diameter varying from 0.1 to 0.3 µm. These HA-coated Ti samples can be regarded as promising multifunctional biomaterials.

The wide application of magnesium alloys as biodegradable implant materials is limited because of their fast degradation rate. Hydroxyapatite (HA) coating can reduce the degradation rate of Mg alloys and improve the biological activity of Mg alloys, and has the ability of bone induction and bone conduction. The preparation of HA coating on the surface of degradable Mg alloys can improve the existing problems, to a certain extent. This paper reviewed different preparation methods of HA coatings on biodegradable Mg alloys, and their effects on magnesium alloys’ degradation, biocompatibility, and osteogenic properties. However, no coating prepared can meet the above requirements. There was a lack of systematic research on the degradation of coating samples in vivo, and the osteogenic performance. Therefore, future research can focus on combining existing coating preparation technology and complementary advantages to develop new coating preparation techniques, to obtain more balanced coatings. Second, further study on the metabolic mechanism of HA-coated Mg alloys in vivo can help to predict its degradation behavior, and finally achieve controllable degradation, and further promote the study of the osteogenic effect of HA-coated Mg alloys in vivo.

Artificial material such as stainless steel (SS) is widely used for orthopaedic applications owing to its superior properties, ease of fabrication and lower cost. However, in the body environment, stainless steel can leach toxic elements such as nickel and chromium. To prevent this, a hydroxyapatite (HAp) coating having chemical characteristics very similar to the human bone was deposited on a medical-grade UNS S31254 austenitic stainless steel by a Low-velocity oxy-fuel spray gun (LVOF). The coating was characterised by using a field emission scanning electron microscope (FESEM), X-ray diffractometer (XRD) and Fourier transform infrared spectroscope (FTIR). The adhesion strength, microhardness and corrosion behaviour were studied using the Tensometre, Vickers microhardness tester and potentiodynamic polarisation with electrochemical impedance spectroscope. The bacterial adhesion and bioactivity of the coating were also evaluated. The LVOF sprayed HAp coating has shown better corrosion resistance, higher bioactivity and higher hardness than the uncoated steel. The presence of tricalcium phosphate, octa-calcium phosphate (OCP) and tetra-calcium phosphate (TTCP) was found in the coating. LVOF sprayed HAp coating is also found suitable in lowering the bacterial adhesion on the steel substrate.

Aluminium-free Mg–4Zn–4Sn–0.6Ca–0.5Mn alloys, with similar mechanical properties to natural bone, were produced and used as substrates for electrophoretic deposition (EPD) of hydroxyapatite (HA) po...

The lack of bioactivity of titanium (Ti) is one of the main drawbacks for its application in biomedical implants since it can considerable reduce its osseointegration capacities. One strategy to overcome this limitation is the coating of Ti with hydroxyapatite (HA), which presents similar chemical composition than bone. Nonetheless, most of the strategies currently used generate a non-stable coating and may produce the formation of amorphous phases when high temperatures are used. Herein, we proposed to generate a Ti-HA composite coating on Ti surface to improve the stability of the bioactive coating. The coating was produced by cold gas spraying, which uses relatively low temperatures, and compared to a Ti coating. The coating was thoroughly characterized in terms of morphology, roughness, porosity and phase composition. In addition, the coating was mechanically characterized using a tensile loading machine. Finally, biological response was evaluated after seeding SaOS-2 osteoblasts and measuring cell adhesion, proliferation and differentiation. The novel Ti-HA coating presented high porosity and high adhesion and bond strengths. No change in HA phases was observed after coating formation. Moreover, osteoblast-like cells adhered, proliferated and differentiated on Ti-HA coated surfaces suggesting that the novel coating might be a good candidate for biomedical applications. info:eu-repo/semantics/acceptedVersion

The goal of the present contribution is to show what is the effect of Ag addition on in vitro bioactivity and degradation characteristics of hydroxyapatite (HAP) in simulated body fluid (SBF), Dulbecco's Modified Eagle's medium (DMEM) and phosphate buffer solution (PBS) over a period of immersion at 37 ± 0.5 °C ranged from 1 to 21 days. Also, the corrosion investigations in all three media were carried out at 37 ± 0.5 °C. The results showed that the coatings behaviour is modulated with respect to the testing media and indicated that the Ag addition into hydroxyapatite has enhanced the general behaviour of HAP by either preventing and/or reducing dissolution of the HAP in SBF and DMEM solutions, while in PBS media the Ag addition contributed to a very slow degradation of hydroxyapatite. Thus, it can be said that the Ag addition into HAP enhances the overall chemical stability and behaviour in acellular media.

Plasma-sprayed hydroxyapatite (HA) coatings have been widely utilized in load-bearing titanium alloy implants. In this study, Mg, Sr co-substituted HA ((Mg, Sr)-HA) nano-scale powders have been synthesized, which are further used to prepare (Mg, Sr)-HA coatings on Ti-6Al-4V alloys in order to improve the biological functions. The average size of (Mg, Sr)-HA nano particles is ∼75 nm. The average bonding strength for (Mg, Sr)-HA coating and samples after heat treatment at 500 °C or 600 °C for 3 h are 26.17 ± 2.11 MPa, 36.07 ± 4.48 MPa and 37.07 ± 2.95 MPa, respectively. There is a significantly increase of bonding strength likely due to low residual stress after heated treatment. MC3T3-E1 cells show a high proliferation rate when cultured with (Mg, Sr)-HA coating extract compared to the normal culture medium, which also exhibit large extension and deposition of extracellular matrices when adhered on the coating surfaces. Thus, these (Mg, Sr)-HA coatings show high bonding strength and improved biological functions, which offer promising future applications in the fields of orthopedics and dentistry.

The optimization of the anodization process of Ti substrate for in situ synthesis of hydroxyapatite/titanium oxide composite coatings on titanium substrate was accomplished. The anodization was performed under 30, 60 and 90 V cell voltage, and the morphology of treated surface, as well as linear and surface roughness, were analysed by field emission-scanning electron microscopy, atomic force microscopy and roughness tester. It was shown by linear and surface roughness analyses that titanium anodized under 60 V has the highest roughness, whereas at 90 V the flattening of the surface occurs. As the highest surface roughness results emerged at 60 V, the novel process of composite anHAp/TiO2 coating synthesis, which comprises simultaneous processes of TiO2 formation and HAp deposition, as well as HAp impregnation within TiO2 surface layer, was performed at this voltage. Ti substrate surface was completely covered by composite coating, with no visible cracks. The adhesion quantified according to ASTM D3359-02 standard is considerably improved with respect to the coatings obtained by cathaphoretic processes, with no need of subsequent sintering. [Project of the Serbian Ministry of Education, Science and Technological Development, Grant no. ON172060]

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.

Biomaterials are natural or synthetic materials that are used in human body and are materials to evaluate, treat, support or replace any tissue, organ, or function of the body. Due to its favorable biocompatibility and mechanical properties, HA-coated metal-based implants are used in the orthopedic surgery operations. For this purpose, sol-gel synthesized nano sized HA powders were produced. Ti6Al4V alloy was coated with hydroxyapatite(HA) by using the sol–gel method. Surface morphologies, thermal, mineralogical properties and bioactivity of the coatings were examined and the characterization of the coatings was performed by using DTA-TG, XRD, SEM, and EDX.

The aim of this work was to investigate the nanomechanical, adhesion and corrosion resistance of hydroxyapatite (HAP) coatings. The electrodeposition process was used to elaborate the HAP coatings on Ti6Al4V alloy. The effect of hydrogen peroxide concentration H2O2 on the electrolyte and the heat treatment was studied. Surface morphology of HAP coatings was assessed, before and after heat treatment, by scanning electron microscopy associated with X-ray microanalysis (SEM-EDXS). Moreover, X-ray diffraction (XRD) was performed to identify the coatings’ phases and composition. Nanoindentation and scratch tests were performed for nanomechanical and adhesion behavior analysis. The corrosion resistance of the uncoated, the as-deposited, and the heat-treated coatings was investigated by electrochemical test. The obtained results revealed that, with 9% of H2O2 and after heat treatment, the HAP film exhibited a compact and homogeneous microstructure. The film also showed a crystal growth: stoichiometric hydroxyapatite (HAP) and β-tricalcium phosphate (β-TCP). After heat treatment, the nanomechanical properties (H, E) were increased from 117 ± 7 MPa and 24 ± 1 GPa to 171 ± 10 MPa and 38 ± 1.5 GPa respectively. Critical loads (LC1, LC2, and LC3) were increased from 0.78 ± 0.04, 1.6 ± 0.01, and 4 ± 0.23 N to 1.45 ± 0.08, 2.46 ± 0.14, and 4.35 ± 0.25 N (respectively). Furthermore, the adhesion strength increased from 8 to 13 MPa after heat treatment. The HAP heat-treated samples showed higher corrosion resistance (Rp = 65.85 kΩ/cm2, Icorr = 0.63 µA/cm2, Ecorr = −167 mV/ECS) compared to as-deposited and uncoated samples.

The morphology, crystal orientation, phase composition and other details of the resulting coating were characterized by means of SEM, XRD, FT-IR and so on. Then, a discussion was conducted about the growth mechanism of HA under the context of magnetic field. According to the research results, the magnetic fields of different intensities have impact on the morphology and crystal orientation of the hydroxyapatite coating to some extent. Additionally, the effect of high magnetic field is found to be more significant.

The production of hydroxyapatite (HAP) composite coatings has continuously been investigated for bone tissue applications during the last few decades due to their significant bioactivity and osteoconductivity. Herein, we highlight the recent experimental and theoretical progresses on HAP coatings, which may bridge the existing gap between theory and practice. The experimental studies mainly deal with electrochemical (EC) and electrophoretic (EP) deposition for the synthesis of nano-HAP in the form of coatings. Additionally, the biocompatible coating method for the fabrication of HAP composite coatings, the plasma spraying (PS) technique, and its mechanism are discussed in this review. Furthermore, the adhesion strength, mechanical, tribological and electrochemical phenomena of HAP composite coatings are critically analyzed. Their ameliorated bactericidal activity is also discussed to recognize the possibility of substituted HAP coatings from a clinical perspective. In addition, computational studies on the HAP system are explored in this report, including the first-principles density functional theory, ab initio modeling and molecular dynamics simulations. Thus, the main significance of this review is to present a collective discussion on the structural features, interfacial mechanics and binding aspects by experimental and theoretical investigations for HAP-based biomaterials, which can provide clear insights for the future research related to orthopedic applications.

Nanotechnology is a very attractive tool for tailoring the surface of an orthopedic implant to optimize its interaction with the biological environment. Nanostructured interfaces are promising, especially for orthopedic applications. They can not only improve osseointegration between the implant and the living bone but also may be used as drug delivery platforms. The nanoporous structure can be used as a drug carrier to the surrounding tissue, with the intention to accelerate tissue&ndash, implant integration as well as to reduce and treat bacterial infections occurring after implantation. Titanium oxide nanotubes are promising for such applications, however, their brittle nature could be a significantly limiting factor. In this work, we modified the topography of commercially used titanium foil by the anodization process and hydrothermal treatment. As a result, we obtained a crystalline nanoporous u-shaped structure (US) of anodized titanium oxide with improved resistance to scratch compared to TiO2 nanotubes. The US titanium substrate was successfully modified with hydroxyapatite coating and investigated for bioactivity. Results showed high bioactivity in simulated body fluid (SBF) after two weeks of incubation.

Hydroxyapatite coatings need similarly shaped splats as building blocks and then a homogeneous microstructure to unravel the structural and chemical hierarchy for more refined improvements to implant surfaces. Coatings were thermally sprayed with differently sized powders (20&ndash, 40, 40&ndash, 63 and 63&ndash, 80 &micro, m) to produce flattened homogeneous splats. The surface was characterized for splat shape by profilometry and Atomic force microscopy (AFM), crystal size by AFM, crystal orientation by X-ray diffraction (XRD) and structural variations by XRD. Chemical composition was assessed by phase analysis, but variations in chemistry were detected by XRD and Raman spectroscopy. The resulting surface electrical potential was measured by Kelvin probe AFM. Five levels of structural hierarchy were suggested: the coating, the splat, oriented crystals, alternate layers of oxyapatite and hydroxyapatite (HAp) and the suggested anion orientation. Chemical hierarchy was present over a lower range of order for smaller splats. Coatings made from smaller splats exhibited a greater electrical potential, inferred to arise from oxyapatite, and supplemented by ordered OH&minus, ions in a rehydroxylated surface layer. A model has been proposed to show the influence of structural hierarchy on the electrical surface potential. Structural hierarchy is proposed as a means to further refine the properties of implant surfaces.

Implantasi menggunakan material titanium Ti-6Al-4V ELI masih memiliki keterbatasan yaitu osseointegrasi yang rendah karena bersifat kurang bioaktif. Hidroksiapatit digunakan sebagai bahan pelapisn meningkatkan bioaktivitas material dan ikatan material dengan jaringan tulang. Material Ti-6AL-4V ELI (kepingan) dilapisi dengan hidroksiapatit menggunakan metode electrophoretic deposition, dengan variasi voltase (5,8, dan 11 volt) selama 5 menit dan variasi waktu deposisi (5,8, dan 11 menit) dengan voltase 8 volt. Pengujian kekasaran dan kekuatan adhesi lapisan hidroksiapatit pada permukaan material dilakukan secara kualitatif. Hasil penelitian yang diperoleh menunjukkan bahwa metode EPD dapat digunakan untuk melapisi material Ti-6Al-4V ELI dengan hidroksiapatit. Massa partikel penyusun lapisan hidroksiapatit relatif dipengaruhi oleh perlakuan waktu deposisi karena terdapat perubahan ketebalan lapisan. Akan tetapi, susunan partikel relatif dipengaruhi oleh daya yang mengakibatkan migrasi partikel yang akan berpengaruh terhadap ikatan lapisan pada permukaan material. Perlakuan voltase 8 volt selama 5 menit menghasilkan kekasaran pemukaan material dilapisi hidroksiapatit Ra 0,88 dan kerusakan lapisan setelah cross cut tape test adalah 2,25% yang berarti lapisan mengalami adhesi dengan baik pada permukaan material. Dengan masa hidroksiapatit relatif tinggi (0,3 mg), lapisan tersebut menutupi permukaan material titanium dengan baik (surface coverage 82,1%) memiliki ketebalan rata-rata (73,3 μm). Hasil yang diperoleh diharapkan sesuai untuk aplikasi biomedis.

Surface modification of orthopedic and dental implants has been demonstrated to be an effective strategy to accelerate bone healing at early implantation times. Among the different alternatives, coating implants with a layer of hydroxyapatite (HAp) is one of the most used techniques, due to its excellent biocompatibility and osteoconductive behavior. The composition and crystalline structure of HAp allow for numerous ionic substitutions that provide added value, such as antibiotic properties or osteoinduction. In this article, we will review and critically analyze the most important advances in the field of substituted hydroxyapatite coatings. In recent years substituted HAp coatings have been deposited not only on orthopedic prostheses and dental implants, but also on macroporous scaffolds, thus expanding their applications towards bone regeneration therapies. Besides, the capability of Q4 substituted HAps to immobilize proteins and growth factors by non-covalent interactions has opened new possibilities for preparing hybrid coatings that foster bone healing processes. Finally, the most important in vivo outcomes will be discussed to understand the perspectives of substituted HAp Q5 coatings from a clinical point of view.

In the present study, the corrosion resistance and bioactivity of AZ91HP magnesium alloy were improved by plasma spraying hydroxyapatite (HA) coating. X-ray diffraction measurements indicated that the coating formed amorphous and little β-Ca3 (PO4)2 besides of HA. The corrosion resistance and bioactivity of the coating and magnesium alloy in simulated body fluid were investigated using immersion test. The coating showed lower corrosion rate and better bioactivity than magnesium alloy. The coating significantly improved the hydrophilicity of Mg alloy. The prothrombin time of the coating was 18 s, and the prothrombin time of Mg alloy was 11 s, so the coating had better anticoagulant activity.

Crystalline strontium-substituted hydroxyapatite (Sr-HAp) coatings with porous structures were directly produced on bulk Ti and TiN-coated substrates by plasma electrolytic oxidation (PEO). PEO was conducted in the electrolytes consisting of 0.4 M Ca(CH3OOH)2·H2O and 0.2 M NaH2PO4·2H2O mixed with various concentrations of Sr(OH)2·8H2O ranging from 0–0.1 M at 350 V for 15 min on bulk Ti. The relative integrated peak intensity, hydrophilicity, and cell viability of obtained Sr-HAp coatings firstly increased and then decreased with increasing the Sr2+ content. This indicates that optimum Sr addition could enhance both the growth and cell viability of the PEO-produced Sr-HAp coatings. Subsequently, the optimum Sr addition [0.05 M Sr(OH)2·8H2O] was employed to make Sr-HAp coatings on TiN-coated substrates. The Sr-HAp coatings with fine porous morphology were obtained. Moreover, average growth rate of the coatings over TiN/Si was much higher than that on bulk Ti. The osteoblast-like cell cultivation tests revealed that the cell viability of the PEO-produced Sr-HAp coatings on TiN-coated substrates was significantly higher than that over bulk Ti. The Sr-HAp coatings with TiN seeding layers are very promising in biomaterials applications.

The effects of preheating and annealing processes on the micromechanical features of thermally sprayed hydroxyapatite (HA) coatings were investigated. The results indicated that subsequent heat tre...

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.

© 2018 American Chemical Society. Bone osteogenesis is a complex phenomenon dependent on numerous microenvironmental cues, with their synchrony regulating cellular functions, such as mechanical signaling, survival, proliferation, and differentiation, as well as controlled regional specification of skeletal progenitor cell fate. Therefore, obtaining a mechanistic understanding of cellular response to a microenvironment is now coming into intense focus, which will facilitate the design of programmable biomaterials for regenerative medicine. State-of-the-art nanomaterial synthesis and self-assembly processes yield complex structures that mimic surface properties, composition, and partially the morphology of the extracellular matrix. However, determining key structural properties that control cell attachment has been challenging and contradictory results are reported regarding the mechanisms and roll of nanostructured materials. Here, we significantly improve osteogenesis on bioinert substrates, demonstrating an exemplary organic-inorganic interface for superior prosthesis biointegration. We identify critical microscale hierarchical features that drastically enhance the cellular response to the same nanoscale architecture. It was observed that hierarchical morphologies, with a porosity above 80%, promote early-stage osteoinduction, as indicated by extensive coating ingrowth and nanofilopodia formation. We determined that cellular integration was mediated by two-way recognition of specific nano- and microtopographical cues between the host tissue and cellular microenvironment. This has allowed us to detail a set of determinant features for the nanofabrication of advanced prosthesis coatings that may ultimately improve implant longevity.

In the present study, we introduce a newly designed antibacterial hydroxyapatite (Ca10(PO4)6(OH)2, HAp) coating that exploits the contact killing capabilities of ZnO. The HAp coating, incorporating ZnO precipitates on its topmost surface layer, was prepared on a Ti substrate using chemical solution deposition followed by heating at 650 °C. The amount of ZnO precipitates could be controlled by changing the ZnO concentration in the deposition solution; furthermore, the Zn release rate from the surface could be controlled by varying the ZnO amount. The ZnO/HAp coating showed excellent antibacterial efficacy against Escherichia coli and Staphylococcus epidermidis strains; however, no correlation was observed between the degree of efficacy and Zn release rate. The antibacterial efficacy of the ZnO/HAp coating likely originates from the contact killing effect of the ZnO precipitates. In summary, the coatings introduced in this work are promising candidates for the surface modification of Ti implants, with a potential ability to combine the prevention of infectious diseases with osteogenic activity.