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With the increasing incidences of orbital wall injuries, effective reconstruction materials and techniques are imperative for optimal clinical outcomes. In this literature review, we delve into the efficacy and potential advantages of using titanium implants coated with nanostructured hydroxyapatite for the reconstruction of the orbital wall. Titanium implants, recognized for their durability and mechanical strength, when combined with the osteoconductive properties of hydroxyapatite, present a potentially synergistic solution. The purpose of this review was to critically analyze the recent literature and present the state of the art in orbital wall reconstruction using titanium implants coated with nanostructured hydroxyapatite. This review offers clinicians detailed insight into the benefits and potential drawbacks of using titanium implants coated with nanostructured hydroxyapatite for orbital wall reconstruction. The highlighted results advocate for its benefits in terms of osseointegration and provide a novel strategy for orbital reconstruction, though further studies are essential to establish long-term efficacy and address concerns.

3D printed porous titanium cage is believed with physiology mechanical properties and biocompatibility for orthopedic usage. Typical split cage design with a grafting window and infilled bone graft has raised a lot of questions. In this research, a modified hydrothermal approach, employing chelated calcium to enhance the medium stability and increase the generated amount, is proposed to construct bioactive hydroxyapatite coating inside the porous structure of 3D printed porous titanium cage. The in vitro and transcriptomic results indicated the hydroxyapatite enhanced the cells physical sensing system, therefore enhanced the osteogenesis inside titanium/hydroxyapatite cage. The in vivo goat spinal fusion experiment indicated the integrative titanium/hydroxyapatite cage, compared with typical split cage/graft cage, showed better bone tissue ingrowth and spinal fusion ability. This research provides a promising hydroxyapatite coating strategy for complex porous structure and revealed the potential advantage of integrative titanium/hydroxyapatite intervertebral cage design.

Introduction The list of pathological conditions that need surgical correction of bone length is very long. In the literature on the topic under discussion, it is reported that the best results are obtained by lengthening according to the Ilizarov method. But many surgeons are not satisfied with the long duration of external fixation, which requires a large number of adjustments and patient compliance. The aim of this work is a analysis of the modern technologies for limb lengthening that actually shorten the time of osteosynthesis using the apparatus for external fixation. Materials and methods Literary sources have been analyzed since the first publication on limb lengthening according to Ilizarov in 1963. The search was carried out in the databases of the RSCI, NCBI Pubmed, Medline. The developments of the employees of the Ilizarov Center are presented. Results An analysis of the literature showed that the fixation units of the apparatus, units for providing movement for distraction, compression and correction of angles have been improved. The invasiveness of the surgical intervention is minimized. Best results can be obtained using automatic lengthening. The Ilizarov Center has developed and experimentally proven methods for reducing the period of distraction and the period of fixation with the apparatus. We combined three factors: an increased round-the-clock distraction rate (2 or 3 mm) with a motorized distractor adjusted to the Ilizarov frame and fixation reinforcement along with regeneration stimulation with HA-coated intramedullary wires in our experimental and clinical trials. This technology has easily conquered a number of clinical practices in Russia, France and Serbia. Conclusion Experimental and clinical substantiation of a two- or three-fold increase in the rate of automated distraction in the conditions of intramedullary reinforcement with a bioactive implant can drastically reduce not only the time of the distraction period, but also the duration of the fixation period with the Ilizarov apparatus.

Membranes of guided bone regeneration (GBR) are widely used in oral implant surgeries. This study successfully developed a new GBR membrane, hydroxyapatite (HA) coating, on Mg–2Zn–Mn–Ca–Ce alloy substrates via a hydrothermal technique. The features of the HA coatings were investigated by complementary characterization methods (SEM, XRD, EDS, and static contact angle). The in-vitro degradation behavior and biocompatibility of HA-coated and bare Mg–2Zn–Mn–Ca–Ce alloys were analyzed in detail. The HA coatings exhibited porous outer surface and compact inner layer, outstanding hydrophilicity, and thus significantly improved the anticorrosion/biodegradability of the Mg alloy substrate in Hank's solution. Moreover, the results of CCK-8 assays and cell adhesion tests suggested that HA-coated samples could further promote cell adhesion and proliferation. HA-coated Mg–2Zn–Mn–Ca–Ce alloys have good biodegradation behavior and biocompatibility, indicating great potential as a GBR membrane material.

Objectives: Titanium implants are regarded as a promising treatment modality for replacing missing teeth. Osteointegration and antibacterial properties are both desirable characteristics for titanium dental implants. The aim of this study was to create zinc (Zn)-, strontium (Sr)-, and magnesium (Mg)-multidoped hydroxyapatite (HAp) porous coatings, including HAp, Zn-doped HAp, and Zn-Sr-Mg-doped HAp, on titanium discs and implants using the vapor-induced pore-forming atmospheric plasma spraying (VIPF-APS) technique. Methods: The mRNA and protein levels of osteogenesis-associated genes such as collagen type I alpha 1 chain (COL1A1), decorin (DCN), osteoprotegerin (TNFRSF11B), and osteopontin (SPP1) were examined in human embryonic palatal mesenchymal cells. The antibacterial effects against periodontal bacteria, including Porphyromonas gingivalis and Prevotella nigrescens, were investigated. In addition, a rat animal model was used to evaluate new bone formation via histologic examination and micro-computed tomography (CT). Results: The ZnSrMg-HAp group was the most effective at inducing mRNA and protein expression of TNFRSF11B and SPP1 after 7 days of incubation, and TNFRSF11B and DCN after 11 days of incubation. In addition, both the ZnSrMg-HAp and Zn-HAp groups were effective against P. gingivalis and P. nigrescens. Furthermore, according to both in vitro studies and histologic findings, the ZnSrMg-HAp group exhibited the most prominent osteogenesis and concentrated bone growth along implant threads. Significance: A porous ZnSrMg-HAp coating using VIPF-APS could serve as a novel technique for coating titanium implant surfaces and preventing further bacterial infection.

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.

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.

Composite scaffolds obtained by the combination of biodegradable porous scaffolds and hydroxyapatite with bone regeneration potential are feasible materials for bone tissue engineering. However, most composite scaffolds have been fabricated by complicated procedures or under thermally harsh conditions. We have previously demonstrated that hydroxyapatite coating onto various substrates under a thermally mild condition was achieved by erbium-doped yttrium aluminum garnet (Er: YAG) pulsed laser deposition (PLD). The purpose of this study was to prepare a polycaprolactone (PCL) porous scaffold coated with the hydroxyapatite by the Er: YAG-PLD method. Hydroxyapatite coating by the Er: YAG-PLD method was confirmed by morphology, crystallographic analysis, and surface chemical characterization studies. When cultured on PCL porous scaffold coated with hydroxyapatite, rat bone marrow-derived mesenchymal stem cells adhered, spread, and proliferated well. The micro-CT and staining analyses after the implantation of scaffold into the critical-sized calvaria bone defect in rats indicate that PCL porous scaffold coated with hydroxyapatite demonstrates accelerated and widespread bone formation. In conclusion, PCL porous scaffold coated with hydroxyapatite obtained by the Er: YAG-PLD method is a promising material in bone tissue engineering.

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]

Background/Aim. The deposition of hydroxyapatite (HAP) on the surface of titanium (Ti) alloys enhances bioactivity and osseointegration of the alloys which are widely used as implant materials in dentistry and orthopaedic surgery. However, the stability of HAP and subsequent biocompatibility of such alloys depends on the coating technique. The aim of this work was to test the cytotoxicity of a Ti alloy (Ti6Al4V), coated with HAP by a new plasma deposition method. Methods. The Ti6Al4V samples prepared as discs, 10 mm in diameter and 2 mm in thickness, were coated with HAP (one or both sides of the alloy) by an innovative atmospheric plasma jet method. The cytotoxicity of uncoated and HAP coated Ti6Al4V samples was evaluated by examining the morphological changes and viability of L929 fibroblasts in direct contact with the test materials. Adequate negative (polystyrene) and positive (nickel) control discs of the same size were used. The indirect cytotoxicity was determined by cultivating L929 cells with conditioning medium (CM), prepared as extract of the test samples incubated in the complete Roswell Park Memorial Institute (RPMI) 1640 medium for cell cultures. The cytotoxic effect was evaluated based on the degree of metabolic activity, necrosis, apoptosis and proliferation of L929 cells, using the appropriate assays. Results. Uncoated and one side HAP coated Ti6Al4V alloys were classified as non-cytotoxic according to the current ISO 10993-5 criteria, whereas two sides HAP coated Ti6Al4V alloy samples were slightlymoderate cytotoxic. The cytotoxicity manifested as the inhibition of metabolic activity and proliferation of L929 cells as well as the induction of their apoptosis and necrosis was significantly reduced by conditioning of HAP/Ti6Al4V alloys for 24 hours. The cytotoxic effect of HAP/Ti6Al4V CM only partly decreased in the presence of nifelate, a calcium (Ca) channel blocker, suggesting that Ca ions were not the only responsible cytotoxic agent. Conclusion. The original HAP coating procedure by atmospheric plasma spraying with high energy input enables the production of the stable adhesive coatings on Ti6Al4V alloys. Their cytotoxicity, which depends on the quantity of HAP coating layer, could be significantly reduced up to the non-cytotoxic level by prior conditioning of the alloys in culture medium. Such a procedure, which removes leachable toxic components, could be useful before implantation of HAP coated alloys in vivo. [Projects of the Serbian Ministry of Education, Science and Technological Development, Grant no. ON 175102 and Grant no. 172026]

Chitosan is a cationic polymer that forms polymerized membranes upon reaction with anionic polymers. Chitosan−carboxymethyl cellulose (CMC) capsules are drug delivery carrier candidates whose mechanical strength and permeability must be controlled to achieve sustained release. In this study, the capsules were prepared from chitosan−γ-glycidoxypropyltrimethoxysilane (GPTMS)−CMC. The mechanical stability of the capsules was improved by crosslinking the chitosan with GPTMS. The capsules were then coated with hydroxyapatite (HAp) by alternately soaking them in calcium chloride solution and disodium hydrogen phosphate solution to prevent rapid initial drug release. Cytochrome C (CC), as a model drug, was introduced into the capsules via two routes, impregnation and injection, and then the CC released from the capsules was examined. HAp was found to be deposited on the internal and external surfaces of the capsules. The amount of CC introduced, and the release rate were reduced by the HAp coating. The injection method was found to result in the greatest CC loading.

The surface of titanium (Ti) dental implants must be modified to improve their applicability, owing to the biological inertness of Ti. This study aims to use sandblasting as a pretreatment method and prepare a hydroxyapatite (HA) coating on Ti to improve its biocompatibility and induce bone bonding and osteogenesis. In this paper, sandblasted Ti discs were coated with α-tricalcium phosphate (α-TCP) via Er:YAG pulsed laser deposition (Er:YAG-PLD). An HA coating was then obtained via the hydrothermal treatment of the discs at 90 °C for 10 h. The surface characteristics of the samples were evaluated by SEM, SPM, XPS, XRD, FTIR, and tensile tests. Rat bone marrow mesenchymal stem cells were seeded on the HA-coated discs to determine cellular responses in vitro. The surface characterization results indicated the successful transformation of the HA coating with a nanorod-like morphology, and its surface roughness increased. In vitro experiments revealed increased cell attachment on the HA-coated discs, as did the cell morphology of fluorescence staining and SEM analysis; in contrast, there was no increase in cell proliferation. This study confirms that Er:YAG-PLD could be used as an implant surface-modification technique to prepare HA coatings with a nanorod-like morphology on Ti discs.

Introduction: The current study aimed as a primary goal is to assess the results of a ceramic-on-ceramic (CoC) bearing hip system matched with ABG (Anatomic Benoist Girard) 2 components in terms of survivorship. Secondary objectives addressed specifically ceramic-related complications as well as specific patterns at the bone-implant interface. Material and methods: This is a retrospective bicentric continuous series involving 147 patients (95 males vs. 52 females) who underwent ABG 2 arthroplasties with CoC bearings. One hundred and twenty-five hips were closely followed-up at a mean period of 11.3 years. Results and discussion: With a mean follow-up of 11.3 years, nine cases (5.7%) underwent revision surgery, four caused by acetabular aseptic loosening, three by deep infections, one ceramic head fracture, and one femoro-acetabular impingement. The global survivorship was 92.2% at 12.7 years. The Harris Hip Score (HHS) mean scores increased post-operatively from 50.1 up to 96.1 points (p

The performance of orthopaedic and dental implants counts on the ability to appraise the mechanical properties of biomaterials. In the present study, nanoindentation was used to characterize the mechanical properties of thermally sprayed hydroxyapatite-coated commercial pure titanium (HA/CP-Ti). From the XRD patterns, the as-sprayed HA coating showed an inhomogeneous mixture of polycrystalline and amorphous phases along with the formation of the decomposed constituents including tricalcium phosphate (α-TCP), tetracalcium phosphate (TTCP) and calcium oxide (CaO). The SEM micrographs of HA coating indicated some incompletely melted particles on the surface of flattened droplets, where the average pore size was around 0.8 µm. After the loadunload indentation experiment, a clear severe sink-in deformation feature was observed around the residual indentation impression of the amorphous part. In contrast, pile-up only occurs during loading for the crystalline part of the coating. In addition, the crystalline part of the coating exhibited a Young’s modulus and hardness of around 120.46 and 7.91 GPa, respectively, which were almost 8 and 259% higher than that of the bare CP-Ti substrate. This is the first report on the nanoindentation characterization of the inhomogeneous mixture of various phase structures in thermally sprayed HA coatings.

Ti6Al4V substrates were anodized in aqueous solution containing 0.15mol/L HF+2mol/L H3PO4. After that, hydroxyapatite coatings is deposited on the anodized Ti6Al4V substrates surface by hydrothermal-electrochemical method at a constant current in an electrolyte containing 0.02mol/L CaCl2, 0.012mol/L K2HPO4·3H2O and 0.139mol/L NaCl. The influence of current density on the coating compositions, microstructure, thickness, bioactivity and bonding strength between the coating and substrate was investigated by XRD, SEM, EDS, step profiler and universal testing machine during deposition process. The results indicate that HA coatings can be successfully obtained on anodized Ti6Al4V surface by hydrothermal-electrochemical deposition with different current densities. The coatings appear a layered growth and parts of crystals are characterized by flower-shape. The thickness of the HA coatings increases firstly and then decreases with increasing current density. When the current density is 1.25mA/cm2, the thickness of the HA coatings reaches the maximum 26.4μm,the coating is the most dense and the bonding strength is near 20.0MPa.The simulated body fluid (SBF) immersion test can quickly promote the deposition of calcium phosphate with a maximum diameter of 7-8μm.

There are treatments available for enamel demineralization or acid erosion, but they have limitations. We aimed to manufacture a device that could directly form a hydroxyapatite (HAp) film coating on the enamel with a chairside erbium-doped yttrium aluminum garnet (Er:YAG) laser using the pulsed laser deposition (PLD) method for repairing enamel defects. We used decalcified bovine enamel specimens and compacted α-tricalcium phosphate (α-TCP) as targets of Er:YAG-PLD. With irradiation, an α-TCP coating layer was immediately deposited on the specimen surface. The morphological, mechanical, and chemical characteristics of the coatings were evaluated using scanning electron microscopy (SEM), scanning probe microscopy (SPM), X-ray diffractometry (XRD), and a micro-Vickers hardness tester. Wear resistance, cell attachment of the HAp coatings, and temperature changes during the Er:YAG-PLD procedure were also observed. SEM demonstrated that the α-TCP powder turned into microparticles by irradiation. XRD peaks revealed that the coatings were almost hydrolyzed into HAp within 2 days. Micro-Vickers hardness indicated that the hardness lost by decalcification was almost recovered by the coatings. The results suggest that the Er:YAG-PLD technique is useful for repairing enamel defects and has great potential for future clinical applications.

Abstract Background The aim of this study was to evaluate osteogenesis ability of CAD/CAM porous zirconia scaffolds enriched with hydroxy apatite used to augment large boney defects in a dog model. Methods Surgical defects were made bilaterally on the lower jaw of 12 Beagle dogs. Cone beam CT images were used to create three dimensional images of the healed defects. Porous zirconia scaffolds were fabricated by milling custom made CAD/CAM blocks into the desired shape. After sintering, the pores of half of the scaffolds were filled with a nano-hydroxy apatite (HA) powder while the other half served as control. The scaffolds were inserted bilaterally in the healed mandibular jaw defects and were secured in position by resorbable fixation screws. After a healing time of 6 weeks, bone-scaffold interface was subjected to histomorphometric analysis to detect the amount of new bone formation. Stained histological sections were analyzed using a computer software (n=12, α=0.05). Mercury porosimetery was used to measure pore sizes, chemical composition was analyzed using energy dispersive x-ray analysis (EDX), and the crystal structure was identified using x-ray diffraction micro-analysis (XRD). Results HA enriched zirconia scaffolds revealed significantly higher volume of new bone formation (33% ± 14) compared to the controls (21% ± 11). New bone deposition started by coating the pore cavity walls and proceeded by filling the entire pore volume. Bone in-growth started from the surface of the scaffold and propagated towards the scaffold core. Islands of entrapped hydroxy apatite particles were observed in mineralized bone matrix. Conclusions Within the limitations of this study, hydroxy apatite enhanced osteogenesis ability of porous zirconia scaffolds.

One of the ways to improve and accelerate osseointegration of a surgical implant with bone is application of biocompatible coatings, in particular, hydroxyapatite (HAp). Since the cases of delamination of the coating take place in dental practice, it is very important to estimate the adhesive strength of HAp with the implant. A measure of the coating-to-substrate bond strength is the energy of this bond. In this research, quantum chemistry is used to calculate the binding energy of functional groups (anions) of hydroxyapatite and titanium 2+, which is a standard implant material. First, using Density Functional Theory with Becke three-parameter Lee-Yang-Parr hybrid exchange-correlation functional, the lowest potential energy surface is calculated. Then, by ab initio molecular dynamics, the reaction path, the reaction products, frequencies of oscillations, the activation energies and binding energies between various combinations of component anions of HAp and Ti(II) are calculated.

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–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 (20–40, 40–63 and 63–80 µm) 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− 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.

The electrochemical behavior of HVOF produced hydroxyapatite (HA) and 80HA-20TiO2 coatings were investigated using electrochemical techniques in natural aerated Hanks' solution in the presence and absence of bovine serum albumin (BSA) for 30 days. All samples presented open circuit potential oscillations, which were associated to the porous nature of the coating that allows the electrolyte reaches the substrate causing activation - passivation at the bottom of the pores. The polarization studies indicated that the 80HA-20TiO2 coating was the only one that showed a narrow potential passive region from around -0.4 V to 0 V in the presence and absence of BSA, indicating the beneficial influence of the addition of TiO2 to the HA coating stability. Our results indicated that BSA in Hanks' solution diminishes the stability of the metallic oxide layer present on the Ti-based alloy accelerating the degrading of hydroxyapatites coatings / substrate interface due to its chelating ability.

Paper presents study on the hydrothermal treatment for hydroxyapatite layer formation on the different biodegradable Mg-substrates. The evaluation of corrosion resistance in Ringer’s solution and contact angle measurements in glycerol were performed. Alloys and composites substrates obtained by mechanical alloying and powder metallurgy route are characterized by submicron range microstructure, which is responsible for further surface processing characteristic. Hydrothermal treatment in Ca-EDTA (ethylenediaminetetraacetic acid calcium disodium salt) led to formation of hydroxyapatite layers, which improves both the corrosion resistance and surface wetting properties compared to microcrystalline magnesium.

The attachment of cells to titanium surfaces is an important phenomenon in the area of clinical implant dentistry. A major consideration in designing implants has been to produce surfaces that promote desirable responses in the cells and tissues. To achieve these requirements, the titanium implant surface can be modified in various ways. This review mainly focuses on the surface topography of dental implants currently in use, emphasizing the association of reported variables with biological outcome.

Nowadays, application of implants as a new method for replacing extracted teeth have been improved. So, many researches have been performed for improving the characteristics of implants. The aim of this study was to design and produce a desired coating in order to obtaining two goals including; improvement of the corrosion behavior of metallic endodontic implant and the bone osseointegration simultaneously. Stainless steel 316L (SS), cobalt-chromium alloy (Vit) and commercial pure titanium (cpTi) were chosen as metallic substrates and hydroxyapatite coating (HAC) were performed by plasma-spraying (PS) process on three different substrates. A novel double layer Hydroxyapatite/Titanium (HA/Ti) composite coating composed of a HA top layer and a Ti under layer was prepared using PS and physical vapor deposition (PVD) process respectively on SS. Structural characterization techniques including XRD, SEM and EDX were utilized to investigate the microstructure, morpholgy and crystallinity of the coatings. Electrochemical potentiodynamic tests were performed in physiological solutions in order to determine and compare the corrosion behavior of the coated and uncoated specimens behavior as an indication of biocmpatibility. Results indicated that the cpTi possesses the highest and SS the lowest corrosion resistance (highest corrosion current density) between uncoated substrates. This trend was independent to the type of physiological environment. The HA coating decreased the corrosion current density of HA coated metallic implants but did not change that trend. HAC acted as a mechanical barrier on the metallic substrate but could not prevent the interaction between metallic substrate and environment completely. The HA/Ti composite coating improved the corrosion behavior of SS. The corrosion current density of HA/Ti coated SS decreased and was exactly similar to single HA coated cpTi in physiological solutions. The results indicated that HA/Ti composite coated SS could be used as an endodontic implant and two goals including improvement of corrosion resistance (biocompatibiiity) and bone osseointegration could be obtained simultaneously.

Although a lot of in vitro and in vivo assays have been performed during the last few decades years for hydroxyapatite bioactive coatings, there is a lack of exploitation of real-time in vitro interaction measurements. In the present work, real-time interactions for a plasma sprayed hydroxyapatite coating were measured by a Multi-Parametric Surface Plasmon Resonance (MP-SPR), and the results were compared with standard traditional cell viability in vitro assays. MP-SPR is proven to be suitable not only for measurement of molecule–molecule interactions but also molecule–material interaction measurements and cell interaction. Although SPR is extensively utilized in interaction studies, recent research of protein or cell adsorption on hydroxyapatite coatings for prostheses applications was not found. The as-sprayed hydroxyapatite coating resulted in 62.4% of crystalline phase and an average thickness of 24 ± 6 μm. The MP-SPR was used to measure lysozyme protein and human mesenchymal stem cells interaction to the hydroxyapatite coating. A comparison between the standard gold sensor and Hydroxyapatite (HA)-plasma coated sensor denoted a clearly favourable cell attachment on HA coated sensor as a significantly higher signal of cell binding was detected. Moreover, traditional cell viability and proliferation tests showed increased activity with culture time indicating that cells were proliferating on HA coating. Cells show homogeneous distribution and proliferation along the HA surface between one and seven days with no significant mortality. Cells were flattened and spread on rough surfaces from the first day, with increasing cytoplasmatic extensions during the culture time.