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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.

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.

Highlights • Septic arthritis of the hip joint is relatively uncommon in adults. • Ag-HA implants have not been used in two-stage total hip arthroplasty. • Ag-HA implants may be used in two-staged total hip arthroplasty., Introduction Septic arthritis of the hip joint in adults is a rare and potentially devasting disease. To the best of our knowledge, there have been no reports of two-stage total hip arthroplasty (THA) for the treatment of septic arthritis of the hip joint with a cementless hip implant that has antibacterial properties. Presentation of case We present a case of two-stage THA with a thermal-sprayed silver oxide-containing hydroxyapatite coating (Ag-HA) implant to treat septic arthritis of the hip joint with hip osteoarthritis in an 80-year-old woman. There was no complication or recurrence at 28 months follow-up after 2nd-stage operation. Discussion Ag-HA implants were found to have antibacterial activity within the subcutaneous tissues and bone, osteoconductive properties, and no adverse reactions in vivo. Moreover, no adverse events due to silver were reported in a clinical or radiographic study. Conclusion To further reduce infection after two-staged THA for septic arthritis of the hip joint, antibacterial implants, such as an Ag-HA implant, may be used.

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.

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.

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.

Using artificial intelligence (AI) applications such as, Artificial neural network (ANN) and Gene expression programming (GEP) to model corrosion performance of the hydroxyapatite coated metallic biomaterials were performed. Created models were analyzed and compared with a response surface methodology (RSM) study. Electrodeposition parameters of the hydroxyapatite on CoCrMo implant materials were used as independent variables in the modeling study. Corrosion potential, Ecorr values calculated from potentiodynamic polarization measurements were used as dependent variable (output data) in AI models. Effect of the deposition parameters on the in vitro corrosion performance of the hydroxyapatite coatings were modeled by ANN and GEP models. ANN models were built with 3 input and 1 output variables using Multilayer Perception Topology. Total 21 electrodeposition and corrosion experiments were used in the ANN and GEP modeling. AI applications were successful for modeling the effect of deposition parameters on the corrosion performance of the hydroxyapatite coatings. Individual effect of the each parameter was investigated statistically. According to the model results predictive capacity and effectiveness of the ANN model is slightly better compared to the GEP and RSM model.

Ag-Ti nanotube array was prepared by simple anodic oxidation method and uniform hydroxyapatite were electrochemically deposited on the nanotubes, and then characterized by SEM, XRD, XPS and EIS. In order to investigate the influence of Ti3+ on the electrochemical deposition of hydroxyapatite on the nanotubes, the Ag-Ti nanotube array self-doped with Ti3+ was prepared by one step reduction method. The experiment results revealed that the Ti3+ can promote the grow rate of hydroxyapatite coatings on nanotube surface. The hydroxyapatite coated Ag-Ti nanotube arrays with Ti3+ exhibit excellent stability and higher corrosion resistance. Moreover, the compact and dense hydroxyapatite coating can also prevent the Ag atom erosion from the Ag-Ti nanotube.

The biocompatible CaP-based coatings are deposited on the bio-materials to improve the metallurgical, mechanical and biological behaviour of medical implants in body fluid environment. Besides, these biocompatible coatings are capable to prevent the leaching of toxic ions from metal to the surrounding body environment and further their porous structure provides good osseointegration. However, in spite of these benefits, it always remains a challenge for the researchers to optimise the various properties of CaP-based coatings which finally affect their clinical performance. To achieve this, several post coating techniques have been developed. Post coating heat treatment is one of the posts coating technique which has been widely investigated by the researchers since last three decades. This review explores the impact of post coating heat treatment on the microstructural, mechanical, electro-chemical corrosion and in-vitro behavior of hydroxyapatite coatings.

A novel one-step hydrothermal method has been developed to deposit a superhydrophobic hydroxyapatite coating on Mg-Gd-Nd-Zn-Zr alloy substrate from a solution containing stearic acid and calcium-phosphate compounds. The as-prepared coatings were mainly made up of hydroxyapatite and calcium stearate. When the volume ratio of ethanol and deionized water is 6:4, the hydroxyapatite coating had a maximum contact angle of 152.8° and a sliding angle of

Atmospheric plasma spraying (APS) is widely used in the fabrication of hydroxyapatite (HA) coating due to the advantages of low-cost, simple operation and it can be used to fabricate coatings with controllable structure. Despite all these advantages, the application of APS deposited HA coating for long-term use is limited by its low crystallinity, low phase purity and poor antibacterial property efficiency. Herein, HA coatings with high crystallinity, phase purity and c-axis crystalline orientation were fabricated by APS. In vitro cell, culture testing suggested that the c-axis oriented HA coating was more effective to promote the proliferation of osteoblasts cells compared with other coatings. The antibacterial activity of HA coating against the bacteria indicated that the c-axis oriented HA coating restrained the bacterial adhesion, and the antibacterial effect of the E. coli bacteria was more pronounced than that of the S. epidermidis bacteria. This study suggests that the HA coatings with the specific c-axis crystalline orientation are available for their potential applications for orthopedic and dental implantation.

Ti-based MOFs have large superficial area, ordered pores array, biocompatible metallic ions and offer better biocompatibility in contrast with other reported MOFs carriers, which makes it possible to be applied in the biomedical field. In this work, we fabricated a novel La3+ doped MIL spherical analogue nanoparticle and use it as an additives for composite coating on titanium implant, which exhibited desirable antibacterial property and corrosion resistance without damaging the biocompatibility. This newly synthesized MOF derivative material provides an option for the development of novel in vivo implant coatings.

WOS: 000409151000003 In this study, in order to increase the adhesive strength of a Hydroxyapatite (HA) coating, deposited on the surface of commercially pure titanium, acid passivation and hydrogen sputtering pretreatments were used. The pure titanium surfaces were passivized by acid solution and treated by hydrogen sputtering, at a temperature of 300 degrees C for 1 h. Ca(NO3)(2)center dot 4H(2)0 and NH4H2PO4 were chosen as starting precursors for Ca and P sources. HA coatings on the titanium surface were deposited using the sol gel method and sintered in air at the temperatures of 750 degrees C-900 degrees C for 1 h. XRD, SEM, EDS and AFM analysis techniques were used for structural and morphological characterization. Scratch test was performed for determining the adhesion of HA coatings. The experimental results indicated that compact and crack free HA coating, which has a Ca/P ratio of 1:6, was formed on pure Titanium (Ti) surface. The adhesive strength values of the HA coating, pretreated with H-2 sputtering and acid passivation were found to be 72.84 MPa and 55.83 MPa at temperature of 900 degrees C, respectively. It was observed that H-2 plasma sputtering pretreatment, improved the adhesive strength of the HA coatings compared to pretreatment with acid passivation. (C) 2017 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

Herein we investigate the efficiency of various biomimetic coatings for localized drug delivery, using vancomycin as key therapeutic drug, which is a widely used antibiotic for the treatment of strong infections caused by positive Gram bacteria. We evaluate classical hydroxyapatite and biomimetic hydroxyapatite-collagen coatings obtained by electrochemical deposition as well as TiO2 nanotubes arrays obtained by electrochemical anodization. Surface morphology, compositional and structural data confirm the incorporation of vancomycin into the layers and drug release profiles for vancomycin evaluate their release ability. Namely, hydroxyapatite coatings lead to a ≈92% vancomycin release after 30h and hydroxyapatite-collagen to 85%, while the TiO2 nanotubes layers lead to 78% release. The antibacterial effect of such drug loaded coatings is evaluated against S. aureus (Gram-positive bacteria). Our study shows that the vancomycin incorporated hydroxyapatite coatings lead to a faster release, while the nanotubular coatings may lead to longer time release and additionally both types of coatings ensure a good antibacterial inhibition.

This study aims at developing the prediction model of cyclic delamination lives of plasma-sprayed HAp coating on Ti-6Al-4V substrate by considering wear by interface contacts and dissolution effect by Simulated Body Fluid (SBF). Delamination of HAp coating can lead to loosening of implants stem and final failure in vivo. In the fracture mechanism of interfaces between HAp coating with Ti substrates, only adhesive strength (interracial tensile strength) or fatigue behavior by longitudinal cracking have been observed. Cyclic delamination mechanism by considering various loading modes and corrosion effect has not been revealed yet. The interface delamination rates by cyclic loading were much higher than those by static loading tests. The result clearly demonstrated that the interface demalination behaviors are dominated not by maximum stress, but by stress range. Surface profile measurement and SEM observation also demonstrated damages by interface contact or third body wear at delamination tips of HAp coating only in the cases of compressions. The mechanisms of acceleration on the delaminations are third-body wear or wedge effect by worn particles which increased mean stress level during cyclic loading. Cyclic loading tests under SBF also revealed that cyclic delamination lives were shortened probably due to crevice corrosion at interfaces. Dissolutions at the tips of delaminations were observed by SEM images under tensile loading condition in SBF. Linearly adding the effects of wear and dissolutions into Paris law could successfully predict the delamination lives of HAp coating for various loading ratios in SBF.

Hydroxyapatite coatings on titanium alloy prepared via electrochemical method show low crystallinity and form cracks that affect implant performance. In this study, the hydrothermal treatment was applied in order to improve the properties of the hydroxyapatite coating. Ti6Al4V substrates were coated with hydroxyapatite via the electrochemical method. The samples were then hydrothermally treated under different temperatures. The effects of hydrothermal treatment temperatures on the hydroxyapatite coating composition, microstructure, crystallinity, as well as on the bonding strength between coatings and substrates, were investigated. The samples' bioactivity was measured by immersing them in a simulated body fluid. Results showed that the hydrothermal treatment healed the cracks of the hydroxyapatite coating deposited by electrochemical method. The coatings became denser with increasing hydrothermal teatment temperatures. The hydrothermal treatment temperatures had negligible effects on hydroxyapatite coating composition. At 180 °C, the hydroxyapatite coating achieved maximum crystallinity, and their bonding strength was about 23 MPa. Bioactivity experiments revealed that the hydroxyapatite coatings obtained via the electrochemical method and the hydrothermal treatment had good bioactivity.

Retrieval analyses allow investigation of the efficacy of artificial implants to replace diseased or damaged natural joints. Implants are not always removed due to mechanical failure; a well-functioning implant may require removal due to causing pain. As an alternative treatment to fusion, total disc replacement is an evolving treatment. Recently, to eliminate the possible failure mechanisms observed in metal-on-polymer and metal-on-metal artificial discs, an all-polymer cervical artificial disc has been introduced. The NuNec cervical arthroplasty system is a self-mating, all-polymer design which utilizes a ball-in-socket configuration with each component made of polyether ether ketone. For the first time, a retrieval analysis of a NuNec cervical disc, which has been removed due to pain from a 54-year-old female patient, has been undertaken. The main reason associated with pain was the size of the implant which was found to be too big for the patient. The time in vivo of the implant was 2 years and at the time of removal, the implant was thought to be functioning well. The average surface roughness values of the socket and the ball of the explanted NuNec disc were measured as 0.067 ± 0.056 μm (Sa) and 0.037 ± 0.023 μm (Sa). Compared to an unused disc, the surface roughness significantly decreased (p = 0.00). The articulating surfaces of the explant had negative skewness and burnished appearances. Evidence for both abrasive and adhesive wear mechanisms was observed on the explant. The hydroxyapatite coatings at the backsides were completely lost.

To improve the bonding strength of Sr and Na co-substituted hydroxyapatite (SNH) coatings for carbon/carbon composites, carbon/carbon composites are surface modified by micro-oxidation treatment. The micro-oxidation treatment could generate large number of pores containing oxygenic functional groups on the surface of carbon/carbon composites. SNH is nucleated on the inwall of the pores and form a flaky shape coating with 10–50 nm in thickness and 200–900 nm in width. The bonding strength between SNH coating and carbon/carbon composites increases from 4.27 ± 0.26 MPa to 10.57 ± 0.38 MPa after the micro-oxidation treatment. The promotion of bonding strength is mainly attributed to the pinning effect caused by the pores and chemical bonding generated by the oxygenic functional groups.

The present work deals with developing a HA coated Mg alloy material system for application in orthopaedic implants. A nanostructured hydroxyapatite (HA) coating was grown on selected Mg alloy (Mg–3Zn) through the electrophoretic deposition (EPD) technique. The mechanical integrity of the coating is established as a function of surface roughness of the substrate and annealing temperature of the coating. Coating on a substrate with lower roughness shows a uniform layer and very few cracks. The mechanical properties of the surfaces help in optimizing the coating conditions to get a better integrated HA coating on the Mg surface. The HA coating shows an impressive 25 times improvement in corrosion resistance of the Mg alloy surface during in vitro exposure. The coating also helps in better growth of bone cells on the Mg surface. This study establishes the potential of electrophoretic deposition of HA coating on Mg–3Zn alloy in orthopaedic application.

In this work, a thick, dense and uniform microstructural hydroxyapatite coating was deposited on a magnesium alloy in an aqueous solution under microwave irradiation at 100 °C in a short time of 10 min. The results showed that the high driving force of interfacial growth under microwave irradiation greatly promoted the growth of hydroxyapatite nuclei into rod-like crystals, and the thickness of obtained hydroxyapatite coating was ∼9.9 μm, larger than that of ∼6.3 μm derived by water-bath heating. The coating derived by microwave heating offered preferable corrosion resistance for the magnesium alloy compared with the coating derived by water-bath heating. The corrosion current density of the coated magnesium alloy was reduced by 100-fold as compared to the naked magnesium alloy.

This paper describes evaluation process of bending strengths of plasma-sprayed hydroxyapatite (HAp) coatings. Plasma-sprayed HAp coatings are widely used in the fields of medical implant in order to improve the biocompatibility of substrate alloys in vivo. Their strength is normally evaluated by indentation-fracture method (IF method) or shearing tests. However, these results are considerably varied because of the pores on the surfaces of coatings and to accurately discuss the quality of coatings, the effects of pore size distributions on their strengths must be considered. The maximum pore size was then predicted using extreme statistics and modified Saltycov’s method. In order to calculate fracture toughness of the specimen, indentation fracture method (IF) was applied. Fracture probability model were then used to determine the strength of the coating layers.

Mechanical resistant bioactive materials are of high interest for biomedical applications. In this work, we address the improvement in mechanical properties of HA coatings by the addition of a cheap and widely available secondary phase material, the talc from soapstone. The composites hydroxyapatite/talc (HA/talc) were successfully obtained by pulsed electrodeposition and characterized by scanning electron microscopy, energy-dispersive X-ray spectroscopy, Raman spectroscopy, corrosion and wear resistance and biocompatibility tests. We found that the addition of talc greatly improves the mechanical properties of coatings (i. e., wear track and friction coefficient in wear tests were significantly diminished) without diminishing corrosion resistance and biocompatibility. Alamar Blue® tests, alkaline phosphatase activity, and collagen production indicate that the biocomposites are biocompatible and talc itself induce bone maturation.

The surface topography of implants plays an important role in affecting the behaviour of osteoblasts. Previous research has demonstrated that porous hydroxyapatite (HAp) coating surfaces fabricated by vapour-assisted flame spraying enhances osteoblast attachment and differentiation, but flame spraying cannot supply sufficient power for fabricating porous surfaces without cracks. To solve this problem, porous HAp coatings were deposited on titanium (Ti) discs using a novel vapour-induced pore-forming atmospheric plasma spraying (VIPF-APS) technique with a higher amount of energy. A water reservoir was placed behind the Ti discs to serve as the vapour source. Ti discs with three different mean pore diameters, namely, ATi (2.65 μm), BTi (15.65 μm), and CTi (35.33 μm), were used, and the HAp coatings that were deposited on these three discs using the VIPF-APS technique were denoted HAp-ATi, HAp-BTi, and HAp-CTi, respectively. For comparison, the conventional APS technique was used to deposit HAp on ATi, and this sample was named HAp-APS/ATi. The results showed that the VIPF-APS technique effectively produced porous HAp coatings, whereas the conventional APS technique yielded dense coatings that are unfavourable for applications. These porous coatings further contributed to higher osteoblast proliferation and distinctive alkaline phosphatase activity. The VIPF-APS technique thus has great potential for producing bioactive coatings that can be used in implants.

A hydroxyapatite (HA, Ca10(PO4)6(OH)2) coating is successfully fabricated on carbon fiber (CF) with SiC interlayer prepared via pack cementation method at 1773 K, 1873 K, 2073 K and 2273 K. The morphologies and microstructures of the SiC interlayer and HA coating are analyzed. The corrosion performance is evaluated by electrochemical behavior in simulated body fluid (SBF). The results show that the morphologies and crystalline structures of SiC interlayers vary with temperatures. The SiC interlayer improves the surface wettability for CF. The HA coating deposited on SiC interlayer modified CF exhibits denser and more uniform structure than that on the CF. Corrosion test shows that the corrosion potential (Ecorr) and corrosion current density (Icorr) for HA coated CF with SiC interlayer are −0.13 V and 0.64 × 10−5 A/cm2, respectively. For HA coated CF, the Ecorr and Icorr are −0.15 V and 1.25 × 10−5 A/cm2, respectively. The Ecorr increases and the Icorr decreases resulting from the introduction of SiC interlayer. The corrosion resistance of HA coated CF with SiC interlayer in SBF is better than that of HA coated CF. The HA coated CF with SiC interlayer would be possible for biological application.

Titanium-based implants are key weight-bearing materials in biomedical engineering due to their excellent bulk mechanical properties and biocompatibility. Designing tissue-material interfaces of titanium implants is essential for an increase in osteointegration of engineered implant materials. Surface morphology is a crucial determinant in the construction of biocompatible and osteointegrative orthopedic and dental implants. Biomimicry of the structural features of bone, specifically its macro-to-mesoporosity, may enable the bone cells to osteointegrate, attain and maintain a physiological strain level. In this study, the surface chemistry and morphology of commercially pure titanium plates were modified using electrochemistry. Titanium oxide substrates were prepared by dual acid polishing and alkaline anodization using 0.1 M KOH in an electrochemical cell with a stainless steel cathode and an anodic voltage of 40 V at 20 °C for 3 min. FE-SEM characterization revealed macro-mesoporous anodized titania surfaces, which were coated by hydroxyapatite using simulated body fluid and pulsed electrochemical deposition at 80 °C, while unprocessed commercially pure titanium surfaces were used as controls. The calcium phosphate deposit on titania plates was characterized as calcium-deficient carbonated hydroxyapatite using XRD, FTIR and FE-SEM, whereas the deposit on non-porous, non-functionalized titanium surfaces was characterized as carbonated apatite. The adhesion strength of the hydroxyapatite coated titania surfaces was 38 ± 10 MPa, implying that these surfaces may be suitable for biological and chemical functionalization of medical implants to tune bioactivity, including delivering drugs. © 2015 Elsevier B.V. All rights reserved. BIDEB 2218 This study has been supported by TUBITAK BIDEB 2218 Post-Doctoral Research Project and TR-SPO . We thank Huseyin Sezer, Talat Apak, Berk Alkan, Sevgin Turkeli, Inci Kol, Muhammet Aydin and Mizrap Canibeyaz for their help in the characterization of titania substrates and HA coatings.

Current processes for coating titanium implants with ceramics involve very high energy techniques with associated high cost and disadvantages such as heterogeneity of the coatings, phase transformations and inability to coat complex structures. In order to address the above problems, we propose a biomimetic hydroxyapatite coating process with the use of peptides that can bind both on titanium surfaces and hydroxyapatite. The peptides enabled homogeneous coating of a titanium surface with hydroxyapatite. The hydroxyapatite-peptide sandwich coating showed no adverse effects on cell number or collagen deposition. This makes the sandwich coated titanium a good candidate for titanium implants used in orthopaedics and dentistry.

Hydroxyapatite (HA) coatings were treated with saturated steam at various temperatures and holding periods. The results show that during plasma spraying a large amount of HA decomposes or transforms to amorphous calcium phosphate (ACP), which results in low crystalline HA coatings. After treated with saturated steam the crystallinity of the HA coatings increases significantly. The relative index of crystallinity indicates that the process temperature together with the corresponding steam pressure has a more pronounced effect on HA crystallinity than the holding period. In addition, HA nanocrystallites form as a result of this process.

Background The effect of hydroxyapatite (HA) coating on the fixation of a cementless femoral stem is discussed, in particular in cases of primary fixation with geometrically stable components. Therefore, we performed a comparative retrospective study of a series of Alloclassic-SL™ stems to: 1) present the long-term results and 2) evaluate the contribution, if any, of proximal HA coating. Hypotheses Long-term cementless press-fit (“flat wedge-shaped”) fixation is reliable and HA coating only improves the radiological results of the proximal bone-prosthesis interface. Materials and Methods One hundred and ninety-eight Alloclassic total hip arthroplasties were performed in 179 patients, mean age 66 years old (22–85), including 105 with proximal HA coating and 93 with the original grit-blast coating. One hundred and ninety-three hips were analyzed after a mean follow-up of 9.8 years (1–24 years). Results Results were excellent or good in 184 hips (95%) with no significant difference between the 2 groups (Merle d’Aubigne ≥ 16 for 89/92 (98%) without HA compared to 95/101 (94%) with HA P = 0.59). Radiographic signs of stable osseointegration were observed in 173 hips (90% of the cases). HA coating significantly improved the radiographic results of the proximal bone-implant interface: (42/92 (46%) of the stems without HA had proximal radiolucencies in zones 1 and 7 compared to 4/101 (4%) with HA ( P = 0.0001)). Polyethylene wear > 0.1 mm/year was observed in 6 hips (3%) including 1/101 (1%) in the group with HA versus 5/92 (5.4%) without HA ( P = 0.17). One intra-operative femoral fracture occurred and there were 9 dislocations in the first 3 postoperative months (4.5%). The main cause of revision surgery was recurrent dislocation (11/17 cases). The “revision per-100 observed-femoral component years” was 0.10 in both groups and survival for aseptic loosening of the stem was 100% (95% CI = 73.2% to 100%) at 20 years. Conclusion This study shows that secondary fixation by osseointegration of a straight standard grit-blasted titanium alloy non-anatomical implant is reliable. Possible proximal fibrous encapsulation, which is reduced by HA coating, but especially conventional polyethylene wear, were the main limitations of this system. Level of evidence III retrospective case-control study.

This study investigates the effects of the electrophoretic deposition process (EPD) at dynamic voltage on the physical and biological characteristics of hydroxyapatite (HA) coatings. HA powder is synthesized and used for preparation of HA/ethanol suspension which is subsequently characterized by X-ray diffraction (XRD), energy-dispersive spectroscopy (EDS), Fourier transform infrared spectroscopy (FT-IR), zeta potential and particle size analyses. Samples are prepared from commercially pure titanium (CP-Ti) substrates and coated with HA using EPD at dynamic voltage that keeps a constant depositional rate by adjusting the current and electrical field during the process. The HA-coated samples are dried and sintered at 800 °C for 2 h to densify the coatings. The XRD, scanning electron microscopy (SEM), EDS and adhesion tests are used to characterize the coated samples. The cross-sectional SEM images indicate that the thickness of coatings enhances as the current increases from 0.07 to 0.35 mA. The coatings are more uniform, packed and non-cracked at lower currents while HA particles start to arrange in a highly porous structure and show non-uniform, cracked and non-stable coatings as the current increases. The results also demonstrate that the best adhesions for the coatings are obtained at lower currents of 0.07 and 0.15 mA. Morphological studies and cell biological experiments are conducted using MG63 cells cultured on the HA-coated sample with the best overall physical performance. The number of attached and proliferated cells on the selected HA-coated sample is higher than on the non-coated titanium sample and culture plate used as control. There are significantly higher ALP activity and better cytoskeleton organization of cells on the HA-coated sample. This study shows that the EPD process at dynamic voltage can influence the structure and morphology of the coatings; therefore, substrate engineering can be used to improve and control cell–substrate interactions.

In this study, a novel method of zinc-substituted hydroxyapatite coating is presented. The technique consists of a two-step hydrothermal process. In the first step, the coatings consisted of parascholzite (JCPDS-01-086-2372), a mixture of parascholzite and monetite (JCPDS-01-071-1759) or parascholzite and brushite (JCPDS-72-0713), depending on the Zn concentration in the precursor solution. The second step consisted of an alkali conversion in a KOH solution. The resulting coating was identified as zinc-doped hydroxyapatite. Growing amounts of ZnO were identified for the coatings obtained with higher Zn content. Rietveld refinement revealed a slight decrease in the unit cell volume, due to zinc partial substitution, when compared to pure hydroxyapatite coatings.

The evaluation of residual stress in bioactive hydroxyapatite (HAP) ceramic coating by nanoindentation technique has been attempted successfully for the very first time ever in the present work. The HAP coatings were deposited on surgical grade 316 L austenitic stainless steel and Ti–6Al–4V substrates by microplasma spraying (MIPS) process. The coatings had Ca/P ratio of 1.67 and were ∼80–90% crystalline. The results showed a residual compressive stress of ∼22 MPa for the MIPS-HAP coatings on the SS316L substrates. For the coatings deposited on the Ti–6Al–4V substrates, however, a residual tensile stress of ∼11 MPa was estimated. These data matched well with those obtained by XRD based technique. Thus, favorable data comparison provides further support to the efficacy of the nanoindentation based technique utilized in the present work for residual stress estimations.

This prospective study was designed to evaluate 196 Anatomique Benoist Giraud (ABG II) total hip arthroplasties which were implanted between September 1999 and December 2000. A minimum 11 years follow up was completed in 183 cases. The bearing surfaces were polyethylene–zirconia in 84 cases, polyethylene–metal in 42 and ceramic–ceramic in 57. Changes in the femoral stem design, in relation to the previous ABG I model, have led to a significant improvement in stress-shielding. Polyethylene wear rate was lower by more than 50% compared with non-crosslinked polyethylene. Excellent and good results were obtained in 90.32% of cases, and implant survival was 98.39% at the end of follow-up.

HA was coated on stainless steel (SS) 316L by using electrophoretic deposition to impart corrosion resistance upon SS 316L. Consequently, corrosion behaviour of HA coated SS 316L deposited from applied voltages 10 V to 60 V (denoted as HA/SS316L-10V until -60V) was evaluated in comparison with pristine SS 316L by various electrochemical studies. As results, linear potentiodynamic polarisation result suggested that HA/SS316L-40V exhibits highest open circuit potential indicating that successful protection of HA coating. Additionally, cyclic polarisation studies revealed that HA coated SS 316L improves pitting corrosion resistance. Finally, EIS results demonstrated that higher polarisation resistance and lower capacitance values for HA/SS316L-40V.

The purpose of this study was to retrospectively investigate the incidence of initial polar gaps and their effect on clinical results in Birmingham Hip Resurfacing cups. A total of 151 hips in 134 patients who underwent hip resurfacing at a mean age of 50 years were examined. The mean follow-up period was 7 years. A polar gap was identified in 47 hips (31%) with a mean width of 2.1 mm. Gaps of 2 mm or more were identified in 21 hips, 6 of which showed reductions in cup inclination during the initial 3 months. After 3 months, no progressive cup migration was observed. There was no cup revision. All gaps were filled with bone within 2 years of surgery. The initial polar gaps had no significant influence on the stability of hydroxyapatite-coated Porocast cobalt-chromium hemispherical monoblock cups (Midland Medical Technologies Ltd, Birmingham, UK), although gaps of 2 mm or more had a higher risk of early migration.

In this study the mechanical behavior of barium titanate foam with hydroxyapatite coating under compressive loads was studied. The effect of foam's porosity and hydroxyapatite coating was investigated in uniaxial compression tests. The results show that the coating magnifies the pressure strength of the structure about five times and enhances its mechanical properties. The uniaxial compression test was simulated in a finite element package in which the porous structure was modeled by crushable foam material model. The results of simulation demonstrate a reasonable correspondence with the experimental data. The results also show that crushable foam material is a good candidate for modeling mechanical behavior of barium titanate foams under compression.

The authors applied the ball impact process, developed by the authors' research group, to fabricate hydroxyapatite (HAp) particle coatings on biocompatible metals such as Ti and its alloys. During this process, under ambient temperature, normal pressure, and in a standard air atmosphere, metal or ceramic balls are accelerated and impacted repeatedly on a metal surface by means of mechanical vibrations; simultaneously, powder particles are sandwiched between the balls and the surface. Consequently, the metal surface is rapidly coated with the powder particles. Using a ZrO 2 vibration chamber and ZrO 2 balls, the authors have successfully fabricated high-density HAp particle coatings with a cover ratio greater than 95% and a thickness of 50 μm, after several tens of minutes of treatment. Experiments were conducted by varying the parameters such as ball diameter, treatment time, and ball filling fraction. The results revealed that the ball diameter should be greater than 5.0 mm and the treatment time longer than 10 min for the fabrication of coatings with high cover ratio and sufficient thickness. This is because, under these conditions, mechanical mixing occurs between the Ti substrate and HAp particle coatings at their interface, and this phenomenon is assumed to enhance adhesion. To decrease the surface roughness of the coatings, repeated treatments using small balls are required.

Pores in hydroxyapatite (HA) coatings affect their mechanical and biological performances, and so far pore characteristic and formation mechanism are not fully understood. In the present study, microstructural observations on plasma sprayed HA coating have been carried out, indicating that globular pores exist commonly on coating surface, cross-sectional facet and fracture surface. Analysis of HA particles plasma sprayed into water shows that hollow HA spheres were formed, and the hollow spheres will transform into globular pores when they impact onto the substrate.

Hydroxyapatite (HA)-coated titanium (Ti) is commonly used for implantable medical devices. This study examined in vitro osteoblast gene expression and antimicrobial activity against early and late colonizers of supra-gingival plaque on nanoscale HA-coated Ti prepared by discharge in a physiological buffered solution. The HA-coated Ti surface showed super-hydrophilicity, whereas the densely sintered HA and Ti surfaces alone showed lower hydrophilicity. The sintered HA and HA-coated Ti surfaces enhanced osteoblast phenotypes in comparison with the bare Ti surface. The HA-coated Ti enabled antimicrobial activity against early colonizers of supra-gingival plaques, namely Streptococcus mitis and Streptococcus gordonii . Such antimicrobial activity may be caused by the surface hydrophilicity, thereby leading to a repulsion force between the HA-coated Ti surface and the bacterial cell membranes. On the contrary, the sintered HA sample was susceptible to infection of microorganisms. Thus, hydrophilic-modified HA-coated Ti may have potential for use in implantable medical devices. From the Clinical Editor This study establishes that Hydroxyapatite (HA)-coated titanium (Ti) surface of implanted devices may result in an optimal microenvironment to control and prevent infections and may have potential future clinical applications.

In this work, three kinds of antibacterial ingredients were loaded into the hydroxyapatite (HA) coating: antibiotic (ampicillin sodium salt), silver ions and water soluble chitosan. Two different kinds of HA coatings with dense and porous structures were prepared by the air plasma spraying (APS) and liquid precursor plasma spraying (LPPS) processes, respectively, for loading the antibacterial ingredients. The effects of different antibacterial ingredients and different coating microstructures on the antibacterial behaviors of HA coatings have been systematically studied. The antibiotic loaded HA coatings showed the best antibacterial activity, while the silver ion loaded HA coatings showed the worst bacterial inhibitory effects among the three kinds of antibacterial materials. The LPPS porous coating loaded with chitosan demonstrated the same excellent antibacterial effect as the antibiotic loaded coatings, while the APS dense coatings loaded with chitosan showed almost no antibacterial effect at 24 h. Overall, the HA coating with porous structure showed increased loading of antibacterial materials and enhanced antibacterial properties. Such observations suggest that both antibacterial material and coating structure have strong influences on the antibacterial properties of the HA coatings.

The novel non-thermal CoBlast process has been used recently to create a hydroxyapatite coating on metallic substrates with improved biological response compared to an uncoated implant. In this study, we compared the biological effect of coatings deposited by this process and the industrial standard technique - plasma-spray. Physicochemical properties of these two coatings have been found to be significantly different in that CoBlast HA is less rough but more hydrophilic than the plasma-spray HA as evidenced by data obtained from profilometry and goniometry. Mesenchymal stem cell attachment and adhesion are enhanced on CoBlast HA. Analysis by a combination of EDX and ICP suggests that the higher crystallinity retained by the CoBlast HA result in slower coating dissolution. Detailed in vitro evaluation reveals that plasma-spray HA might induce slightly faster cell proliferation and earlier osteogenic differentiation, but CoBlast HA becomes equivalent to it by the late osteogenic stage. PCR array facilitated the identification of differentially regulated genes involved in various functional aspects of in vitro osteogenesis by the CoBlast HA coating. The expression level of the functional protein products of these genes are in agreement with the PCR data. Coating metallic screws with HA significantly improves the in vivo osseointegration. By measuring of removal force using torque measurement instrument and analyzing the patterns found in X-ray images it is demonstrated that the two HA coatings elicit comparable osseointegration. Using simulated impaction model, CoBlast HA is shown to maintain better performance in cell attachment and mineralization than plasma-spray HA, especially following significant impactions. This might indicate a potentially greater osteoconductivity of CoBlast HA coating in shear-stress associated surgical applications. Collectively, it was demonstrated that CoBlast HA is an effective alternative to plasma-spray HA coating and a promising replacement for specialized surgical applications.

Hydroxyapatite (HAp) coatings were uniformly formed on pure Mg by a hydrothermal treatment using a C 10 H 12 N 2 O 8 Na 2 Ca (Ca-EDTA) solution. The growth mechanism of the HAp coating was investigated with XRD, SEM and TEM. At the initial stage, dome-shape HAp precipitates were formed on the Mg. Subsequently, the precipitates grew and the coating became a dual-layer consisting of an inner dense HAp layer and outer course layer consisting of rod-like HAp crystals. The protectiveness of the coatings with different treatment times was investigated by a polarization test in a 3.5 wt.% NaCl solution. The corrosion current density decreased with the growth of the HAp coating.

Treating senile osteoporotic patients with unstable hip fractures remains a challenge. We evaluated the results of 87 cementless bipolar hemiarthroplasties using an extensively hydroxyapatite-coated long stem for unstable intertrochanteric fractures in senile patients. Sixty-one hips were followed for a minimum of 2 years (mean, 36 months) postoperatively. The mean Merle d'Aubigne and Postel hip score was 14.7 points (12-18). Two hips were reoperated because of infection. Of the remaining 59 hips, 48 were included in the radiographic analysis. Although cortical porosis around the stem was seen in 18 hips, there was no loosening or osteolysis. Cementless bipolar hemiarthroplasty using an extensively hydroxyapatite-coated long stem is a useful option for the treatment of unstable intertrochanteric fracture in senile patients with severe osteoporosis.

The purpose of this study was to evaluate the effects of different hydroxyapatite (HA) coating thicknesses on osseointegration after dental implantation in dogs. Six dogs, weighing 10–15 kg, were used in this study. The fixtures, with HA coatings of different thicknesses and made by Dentis, were implanted for 12 weeks in right iliac crestal bone sites and for 6 weeks in left iliac crestal bone sites. Implants in the control group were coated with resorbable blast medium, whereas those in the experimental group were coated with HA of different thicknesses (1, 5, and 15 μm). All dogs were sacrificed at 12 weeks after implant placement, and histological and histomorphometric analyses were performed. The implants were all successful, and a significant difference between the control and experiment groups was observed at 6 weeks, although no significant difference between the control and experimental groups was seen at 12 weeks. These results suggested that HA implant coating may positively affect early osseointegration, but coating thickness had no significant effect on ultimate osseointegration.

Chitosan was widely used as an antibacterial component. While most antibacterial materials also possess cytotoxicities, we hypothesize that selectively destruction of bacterial cells can be achieved by controlling the material parameters of chitosan, due to its intrinsic antibacterial mechanism. In this study, porous hydroxyapatite coatings prepared by the liquid precursor plasma spraying process were used for loading the chitosan with different concentrations: 10, 20, 50, and 100 g/L, respectively. The antibacterial properties and osteoblastic cell response of the hydroxyapatite/chitosan complex coatings were studied as a function of chitosan concentration. The results indicated that the antimicrobial activity was directly proportional to the chitosan concentration, while loading of chitosan with lower concentrations (10 and 20 g/L) was even beneficial to the proliferation of osteoblastic cells. Overall, our study demonstrated that combined antibacterial activity and superior osteoblast cell response can be achieved by using hydroxyapatite/chitosan complex coatings, which have great potential in bone replacement and regeneration applications.

A novel process has been developed for the preparation of a hydroxyapatite (HA) coating with a hierarchical structure on a Ti substrate. The Ti substrate was first subjected to electrolytic deposition at −1.6 V (versus Ag/AgCl/KCl) in a solution of 0.042 M Ca(NO 3 ) 2 ·4H 2 O and 0.025 M NH 4 H 2 PO 4 at 85 °C for 3 min, and then post-treated in a 0.25 M NaOH solution, with the addition of 0.05 M Na 3 Cit at 85 °C for 5 h. The experimental results showed that the coating experienced a phase conversion from octacalcium phosphate to HA after the post-treatment step. The HA coating had well-distributed, micro-sized pores comprising three-dimensional interconnected mesoporous HA belts, which would greatly increase the porosity and surface area of the coating.