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Thin hydroxyapatite coating produced by the ion beam dynamic mixing method
Abstract
An ion beam dynamic mixing (IBDM) method was used to produce thin hydroxyapatite coatings on titanium substrates. Structure, solubility and bond strength of coatings were evaluated. The hydroxyapatite-type structure was obtained from heat-treated coatings. As-coated coatings seemed to be almost dissolved within 1 d in Hanks' solution. The thin layer of films, however, was recognized with a firm intermediate compound (such as Ti3P4) to the substrate by X-ray photoelectron spectroscopy, indicating the high tensile bond strengths from the as-coated films. Although slight reductions of the bond strength were observed in heat-treated specimens, the strengths were not reduced by immersion in Hanks' solution for 30 d.
... Introduction Heterogeneous nucleation and growth of calcium phosphates salts (hereafter named as CaP) on metallic substrates (mainly Ti and its alloys) has been a subject of intensive research in the last two decades because of the significance of CaP-coated implants for load bearing applications in the orthopaedic and dental fields. [1][2][3][4][5][6][7][8][9][10][11][12] Few studies, however, have been performed on the nucleation and growth of CaP on non-metallic substrates. [13][14][15][16] Besides its interest at a fundamental level, these studies may have either a biomedical relevance in the preparation of implants for non-load bearing applications, or as a tool to understand heterogeneous nucleation in biological systems, or else, in the preparation of biomimetic functionalized surfaces with potential capability to induce the nucleation of protein crystals. ...
... Raman spectra of calcium phosphate layers deposited at 21 days and 21 days in presence of 0.005 wt% PAA. The insert shows the XRD diagram of the amorphous calcium phosphate layer deposited in presence of 0.005 wt% PAA.The presence of OCP is also revealed by the bands at 958 cm -1 and 966 cm -1 (shoulder) and the broad band at around 1010 cm -1 in the Raman spectra (Figure 5, left), characteristics of the P-O symmetric stretching modes of PO 4 (υ s PO 4 ) and HPO 4 (υ s HPO4) in the OCP phase23 . In the presence of PAA, even at the lowest concentration used (0.005 wt%), the layers are composed of ACP. ...
We propose for the first time the vapour diffusion method to deposit bioinspired calcium phosphate films on mineral substrates, i.e. delaminated mica muscovite sheets, and to assess the capability of these films to affect the nucleation and growth of lysozyme crystals. Deposited calcium phosphate layers were composed of octacalcium phosphate (OCP) and apatite (Ap) nanocrystals as minor phase, with increased amount of OCP at higher crystallization times. In the presence of polyacrylic acid (PAA) deposited layers were composed of amorphous calcium phosphate (ACP). Results of lysozyme crystallization showed that OCP/Ap-coated mica sheets slow down the nucleation process without altering significantly the number of nucleated crystals per droplet respect to the uncoated control. ACP-coated mica sheets acted as an inhibitor, thus delaying the nucleation and reducing in addition the number of lysozyme crystals. These results contrasted with the nucleation induction effect observed when calcium phosphate nanopowders were added to the crystallization drops. All coated-substrates promoted the formation of flat lysozyme crystals at the substrate-solution interface, and some of them retained its laminar morphology. Unexpectedly, the ACP coatings templated the 2D assembly of lysozyme producing thin films. The observation of the lysozyme thin films was possible only in those ACP-coated supports prepared in presence of 0.015 and 0.02 wt% PAA.
... A typical deposition system therefore consists of an electron or ion beam that vaporizes a CaPO4 bulk target to produce a cloud of elements directed towards the substrate surface, and a source that simultaneously irradiates the substrate with high-energy inert (e.g., Ar + ) or reactive (e.g., O2 + ) gas ions to aid deposition. This technique, which consists of two main parts, is called "ion beam dynamic mixing" when Ca + ions are used for irradiation [312,313]. Excellent illustrations of the IBAD technique can be found in these references [32,179,181]. ...
The present overview describes various production techniques for biocompatible calcium orthophosphate (abbreviated as CaPO4) deposits (coatings, films and layers) on the surfaces of various types of substrates to impart the biocompatible properties for artificial bone grafts. Since, after being implanted, the grafts always interact with the surrounding biological tissues at the interfaces, their surface properties are considered critical to clinical success. Due to the limited number of materials that can be tolerated in vivo, a new specialty of surface engineering has been developed to desirably modify any unacceptable material surface characteristics while maintaining the useful bulk performance. In 1975, the development of this approach led to the emergence of a special class of artificial bone grafts, in which various mechanically stable (and thus suitable for load-bearing applications) implantable biomaterials and artificial devices were coated with CaPO4. Since then, more than 7500 papers have been published on this subject and more than 500 new publications are added annually. In this review, a comprehensive analysis of the available literature has been performed with the main goal of finding as many deposition techniques as possible and more than 60 methods (double that if all known modifications are counted) for producing CaPO4 deposits on various substrates have been systematically described. Thus, besides the introduction, general knowledge and terminology, this review consists of two unequal parts. The first (bigger) part is a comprehensive summary of the known CaPO4 deposition techniques both currently used and dis-continued/underdeveloped ones with brief descriptions of their major physical and chemical principles coupled with the key process parameters (when possible) to inform readers of their existence and remind them of the unused ones. The second (smaller) part includes fleeting essays on the most important properties and current biomedical applications of the CaPO4 deposits with an indication of possible future developments.
... The structure of HA is crystallographically similar to that of bone mineral, which is not only bioactive but also osteoconductive, non-toxic and non-immunogenic [39,40]. An HA coating can be prepared by various processes [41][42][43][44][45][46], among which plasma spraying is the most common technology because of its high deposition rate and low cost. When HA is deposited onto Ti-6Al-4V, a relatively high bond strength could be obtained under high temperature by forming CaTiO 3 acting as a bond layer [39]. ...
Dental implants have been widely applied in partially and fully edentulous patients and have shown predictable clinical outcomes, but there are still many cases of implant failures, such as osseointegration failure and peri-implant inflammation. To improve the success rate of implants, especially in improving osseointegration and antibacterial performance, various methods of implant surface modification have been applied. Surface modification methods covered include sandblasting with large-grit corundum and acid etched (SLA), plasma spraying, plasma immersion ion implantation (PIII), sputter-deposition, selective laser melting (SLM), anodic oxidation, microarc oxidation, sol-gel coating, alkaline heat treatment (AH) and Layer-by-Layer (LBL) self-assembly. This review comprehensively summarizes the influence of each method on osseointegration and biofilm attachment. The mechanical, chemical and biological disadvantages of these methods are involved. Besides, the mechanisms behind such techniques as increasing surface roughness to expand superficial area and enhance the adhesion of osteoblastic cells are discussed.
... HA can be deposited on the prosthesis by a range of various methods such as thermal spraying (like plasma spraying or powder plasma spraying (PPS) [174], flame spraying [175], high-velocity oxy-fuel (HVOF) combustion spraying [176], high-velocity suspension flame spraying (HVSFS) [177], Liquid plasma spraying (LPS), and suspension plasma spraying (SPS)) [178], sputter coating (like direct current (DC) sputtering, radio frequency (RF) sputtering, reactive sputtering, ion beam sputtering [179], and magnetron sputtering [180]) [181], electrophoretic deposition [182], electrochemical deposition [183,184], pulsed laser deposition (PLD) [185], solgel [186], dip coating [187], electron-beam and ion beam deposition [188], biomimetic coating [189], hot isostatic pressing, and dynamic mixing [190]. Despite some positive short-term clinical results for HAcoated implants, long-term results have not been very promising [191]. ...
High rate of bone grafting surgeries emphasizes the need for optimal bone substitutes. Biomaterials mimicking the interconnected porous structure of the original bone with osteoconductive and osteoinductive capabilities have long been considered. Hydroxyapatite (HA), as the main inorganic part of natural bone, has exhibited excellent regenerative properties in bone tissue engineering. This manuscript reviews the HA extraction methods from bovine bone, as one of the principal biosources. Essential points in the extraction process have also been highlighted. Characterization of the produced HA through gold standard methods such as XRD, FTIR, electron microscopies (SEM and TEM), mechanical/thermodynamic tests, and bioactivity analysis has been explained in detail. Finally, future perspectives for development of HA constructs are mentioned.
... Osseointegration establishment and infection prevention on a titanium (Ti) medical implant are indispensable for the success of implant surgery. 1,2 Fabricating hydroxyapatite (HAp; Ca 10 (PO 4 ) 6 (OH) 2 ) coatings has been considered the most effective method to improve osteogenesis [3][4][5][6] ; thus, HAp-coated Ti implants are currently being used extensively in the fields of orthopedics and dentistry. Integration of antibacterial functions into implants for decreasing infection rate results has been in high demand among medical experts. ...
Silver‐containing hydroxyapatite (Ag/HAp) layer on a bioinert material provides both bioactive and antibacterial properties; however, the Ag release duration needs to be customized to a patient's age and metabolism for minimizing the toxic effects. Herein, we present a facile chemical process to produce an ultrathin Ag/HAp layer on a Ti implant with a customized Ag‐releasing profile. The process involves the following steps: preparation of a slurry‐type reagent by mixing calcium phosphate powder with an aqueous AgNO3 solution, burying a Ti substrate in the slurry, and heating the slurry in air. An HAp layer, approximately 50 nm thick, with Ag particle deposits was obtained using this process. The Ag‐particle content can be varied by adjusting the concentration of AgNO3 solution used for slurry preparation, resulting in different Ag‐release profiles in a physiological solution. For instance, Ag release was retained for up to 30 days when 100 mM AgNO3 was used, whereas the release lasted 15 days when 10 mM AgNO3 was used. The duration of the antibacterial activity varied accordingly, but Ag‐release‐derived cytotoxicity was not observed irrespective of the AgNO3 concentration. In addition, differentiation of osteoblast‐like cells was facilitated owing to the formation of the HAp layer. Thus, the chemical process presented in this study allows the production—at a clinical site—of an Ag/HAp layer customized to the patient's needs.
... Hydroxyapatite (HA), an inorganic component of bone, can be synthesized on a large scale (Nayak, 2010) and has been widely applied in coatings on orthopedic implants (Oonishi, 1991), not only due to its excellent osteoinductivity and osteoconductivity but also given its ability to separate the implant surface from wear debris and regulate the immune response to accelerate tissue repair (Lahiri et al., 2011;Qin et al., 2018). Various methods, including sputter coating (Van Dijk et al., 1995), thermal spraying (Ong and Lucas, 1994), pulsed dynamic mixing (Yoshinari et al., 1994), laser ablation (Clèries et al., 2000), hot isostatic pressing (Wie et al., 1998), and dip coating (Shi et al., 2002), have been developed for HA coating. Nevertheless, fabrication process-related issues, such as harsh fabrication conditions and expensive instruments, make the doping of antibacterial molecules difficult. ...
There is a substantial global market for orthopedic implants, but these implants still face the problem of a high failure rate in the short and long term after implantation due to the complex physiological conditions in the body. The use of multifunctional coatings on orthopedic implants has been proposed as an effective way to overcome a range of difficulties. Here, a multifunctional (TA@HA/Lys)n coating composed of tannic acid (TA), hydroxyapatite (HA), and lysozyme (Lys) was fabricated in a layer-by-layer (LBL) manner, where TA deposited onto HA firmly stuck Lys and HA together. The deposition of TA onto HA, the growth of (TA@HA/Lys)n, and multiple related biofunctionalities were thoroughly investigated. Our data demonstrated that such a hybrid coating displayed antibacterial and antioxidant effects, and also facilitated the rapid attachment of cells [both mouse embryo osteoblast precursor cells (MC3T3-E1) and dental pulp stem cells (DPSCs)] in the early stage and their proliferation over a long period. This accelerated osteogenesis in vitro and promoted bone formation in vivo. We believe that our findings and the developed strategy here could pave the way for multifunctional coatings not only on orthopedic implants, but also for additional applications in catalysts, sensors, tissue engineering, etc.
... Moreover, degradation of the coatings showing low crystallinity was reported to occur rapidly in the living body, which led to use of a thinner film to resolve these problems [109,110]. The recommended commercial HAp-based coating thickness prepared by the plasma spray technique is around 50 µm, even though the coating is assumed to deteriorate rapidly due to the dissolution process [107,111]. ...
Together, 316L steel, magnesium-alloy, Ni-Ti, titanium-alloy, and cobalt-alloy are commonly employed biomaterials for biomedical applications due to their excellent mechanical characteristics and resistance to corrosion, even though at times they can be incompatible with the body. This is attributed to their poor biofunction, whereby they tend to release contaminants from their attenuated surfaces. Coating of the surface is therefore required to mitigate the release of contaminants. The coating of biomaterials can be achieved through either physical or chemical deposition techniques. However, a newly developed manufacturing process, known as powder mixed-electro discharge machining (PM-EDM), is enabling these biomaterials to be concurrently machined and coated. Thermoelectrical processes allow the migration and removal of the materials from the machined surface caused by melting and chemical reactions during the machining. Hydroxyapatite powder (HAp), yielding Ca, P, and O, is widely used to form biocompatible coatings. The HAp added-EDM process has been reported to significantly improve the coating properties, corrosion, and wear resistance, and biofunctions of biomaterials. This article extensively explores the current development of bio-coatings and the wear and corrosion characteristics of biomaterials through the HAp mixed-EDM process, including the importance of these for biomaterial performance. This review presents a comparative analysis of machined surface properties using the existing deposition methods and the EDM technique employing HAp. The dominance of the process factors over the performance is discussed thoroughly. This study also discusses challenges and areas for future research.
... Nitrogen and argon ions were implanted on HAp coatings to enhance the mechanical strength [40]. Ion beam mixing technique has been used to improve the HAp adhesion on titanium substrate [41]. Cell adhesion, bioactivity, and wettability of the biomaterials were improved by irradiation [42] and ion beam [43]. ...
Nitrogen ions (70 keV) were implanted on composite coatings containing polymer/Mg (magnesium)–Ag (silver) ions co-incorporated hydroxyapatite which is developed by microwave irradiation. Average crystallite size of modified coatings is reduced to 80% compared to pristine. The variation of bond strength of modified coatings is realized. The electrical resistance (77%), microhardness (4.3%), roughness (4.5 times) and pore size are enhanced on the modified coatings. Superhydrophilic surface is tuned to hydrophobic on implantation. At higher fluence (1×10¹⁷ ions/cm²) depicted an enhanced corrosion potential compared to the other coatings. Thus, the new insight of modified coatings is realized by correlating phase-structure, surface and anticorrosion.
... However, some shortcomings of plasma-spray apatite coatings, such as degradation and fatigue of the coating, as well as long-term clinical safety and prognosis, have been suggested [9][10][11] . To overcome these problems, physical vapor deposition (PVD) techniques such as magnetron sputtering and ion beam dynamic mixing have been introduced to deposit thin calcium phosphate coatings on dental implants [12][13][14] . PVD-deposited calcium phosphate coatings are more adherent to the underlying titanium surface and less prone to the formation of cracks than plasma-sprayed coatings. ...
The molecular precursor method is an easy and simple method for coating thin carbonate-containing apatite (CA) films onto titanium surfaces. A molecular precursor solution containing ethanol, calcium-EDTA complex, and phosphate salt was dropped onto a titanium surface and then heated at 600°C for 2 h. An adherent thin CA coating was achieved. Animal implantation experiments showed that CA-coated implants had significantly higher bone-to-implant values than non-coated implants (p<0.05). The molecular precursor method was also used to coat three-dimensional titanium webs (TWs). Thin CA films could be coated inside the center area, as well as the surface of the TW, with excellent bone formation inside the CA-coated TW. Furthermore, the molecular precursor method was used to coat partially stabilized zirconia with CA. Better bone response was observed for CA-coated zirconia. From this, it is concluded that the molecular precursor method is useful for producing thin CA coatings on implant materials.
... [385] Calcium and sodium ion implantation can enhance the formation of HA on the surface of Ti and Ti alloys due to the production of CaTiO 3 or NaTiO 3 . [386][387][388] Silver-ion implanted Ti and Ti alloys possess antiinfective property and therefore they have been widely used as biomedical implants. Wan et al. [389] conducted the surface modification of www.advancedsciencenews.com www.aem-journal.com ...
Thanks to a considerable number of fascinating properties, titanium (Ti) and Ti alloys play important roles in a variety of industrial sectors. However, Ti and Ti alloys could not satisfy all industrial requirements; the degradation of Ti and Ti alloys always commences on their surfaces in service, which declines the performances of Ti workpieces. Therefore, with aim to further improve their mechanical, corrosion and biological properties, surface modification is often required for Ti and Ti alloys. This article reviews the technologies and recent developments of surface‐modification methods with respect to Ti and Ti alloys, including mechanical, physical, chemical, and biochemical technologies. Conventional methods have limited improvement in the properties and/or restriction on the geometry of workpieces. Therefore, many advanced surface‐modification technologies have emerged in recent decades. New methods make Ti and Ti alloys have better performance and extended applications. With requirement of high surface properties in future. Understanding the mechanism in various surface‐modification methods, combining the advantages of current technologies and developing new coating materials with high performance are required urgently. As such, incorporation of different surface‐modification technologies with high‐performance modified layers may be the mainstream of surface modifications for Ti and Ti alloys.
... Surface modification of metallic implants is done by various techniques to improve biocompatibility and bioconductivity [5][6][7][8][9][10][11]. Plasma coating is one such technique used to coat bone-like material hydroxyapatite on Ti implants for primary adhesion and osseointegration [12][13][14][15]. ...
The study was performed to understand the impact of heat in plasma coating and ceramic firing of titanium (Ti) and titanium alloy (Ti-6Al-4V) on their mechanical properties, and microstructure. Standard specimens were prepared to measure tensile strength before and after simulated heating cycles using Instron machine of model 4206 at a crosshead speed of 1 mm/min. Yield strength, ultimate strength, and elongation were recorded. The microstructure was studied using an optical microscope. The mechanical properties, microstructure, and grain size remained the same as that of as-received samples at temperatures of 600 and 700 °C for both Ti and Ti-6Al-4V. At temperature 800 and 900 °C decrease in yield strength, and ultimate tensile strength with a change in microstructure was observed. The temperature of plasma coating and ceramic firing that Ti and Ti-6Al-4V metal substrates encounter during the fabrication of coated implants and metal-ceramic restorations do not affect the mechanical properties and microstructure. Above 800 °C, a significant change in mechanical properties and microstructure is observed. Keywords: Heat treatment, Microstructure, Tensile strength, Titanium, Ti-6Al-4V
... Titanium (Ti) and its alloys are the most commonly used metal for the manufacture of orthopedic implants, while hydroxyapatite (HA), which is a calcium phosphate ceramic, is bioactive and biocompatible when used as a bone substitute. To improve the biocompatibility and mechanical properties of prostheses, calcium phosphate coatings on titanium surfaces are often investigated in order to combine the benefits of both the materials [1,2]. In addition to HA, the deposition of other carbonate-containing apatite (CA) films on titanium substrates is interesting because of the resulting chemical resemblance to bone mineral [3]. ...
... Coatings with specific features can be deposited on metallic substrate through several techniques such as plasma spray [16], vapor deposition [23], solgel method [24], magnetron sputtering [25], pulsed laser ablation [26], dynamic mixing [27], dip coating [28], electrophoretic and electrochemical deposition [29], biomimetic coating [30], ion-beam-assisted deposition [31], hot isostatic pressing [32], polymeric route [33]. Among the aforementioned techniques, electrochemical deposition (ED) is a versatile technique, easy to use, cost effective, which allows a good control of the development of materials with properties [34]. ...
The aim of this study is to develop bioactive-antibacterial coatings on Ti6Al4V using pulsed electrochemical technique. The deposition was carried out in a three electrode set-up within an electrolyte prepared by dissolving Ca(NO3)24H2O, NH4H2PO4 and Ag(NO3) in ultra-pure water. The paper aims to evaluate the effect of Ag addition on morphology, elemental and phase composition of hydroxyapatite coatings. The hydroxyapatite morphology has changed after silver doping, revealing a surface with agglomeration of spherical particles. Phase composition has confirmed the hydroxyapatite formation and, by adding Ag, the peaks have slightly shifted towards left, indicating that Ag is substituting the Ca present in the hydroxyapatite lattice.
... In order to improve the bioinert behaviour of titanium, one major direction is to modify the surface with ceramic based materials using various deposition techniques such as plasma spraying [20], vapour deposition [21], sol-gel method [22], magnetron sputtering [23], pulsed laser ablation [24], dynamic mixing [25], dip coating [26], electrophoretic and electrochemical deposition [27], biomimetic coating [29], ion-beam-assisted deposition [30], hot isostatic pressing [31], polymeric route [32]. Among the above-mentioned techniques, electrochemical deposition (ED) is a versatile technique that seems to be a good alternative, offering the possibility to cover porous structures and complex shape objects. ...
Surface functionalization of pure titanium (cp-Ti) with hydroxyapatite (HAp) was successfully achieved by means of electrochemical deposition (ED) in a solution containing calcium nitrate and ammonium dihydrogen phosphate. The aim of this study is to evaluate the influence of the deposition temperature on the elemental and phase composition, chemical bonds, morphology, and in vitro electrochemical behaviour in biological simulated media (simulated body fluid - SBF). The roughness and wettability of the developed coatings are also investigated. By increasing the deposition temperature from 50. °C to 75. °C, the HAp coatings present a well-crystalized structure, denser and a nobler behaviour in terms of electrochemical behaviour in SBF at 37. °C. Also, by increasing the deposition temperature from 50. °C to 75. °C, the contact angle has decreased from 76.1° to 27.4°, exhibiting a highly hydrophilic surface. Taking into consideration all the obtained data, electrodeposition of HAp at 75. °C was found preferable when compared to 50. °C. The characteristics of the HAp coatings can be easily adjusted by optimizing the electrochemical deposition parameters and/or controlling specific features like pH, temperature, or ionic concentration of electrolyte, etc.
... Synthetic CaP coatings can be prepared by a variety of processes [49,737,738], such as plasma spraying (PS) [49,389,[739][740][741][742], high-velocity oxygen-fuel (HVOF) thermal spraying [743], sputter coating [744], radio-frequency magnetron sputtering [745], pulsed laser deposition (PLD) [746,747], ion-beam deposition [748,749], frit enamelling [49], hot isostatic pressing (HIP) [750], metallo-organic chemical vapour deposition (CVD) [751], derivation from sol-gels [752,753], electrophoretic deposition (EPD) [754][755][756][757], chemical deposition [758,759], and electrodeposition (ED) [92,184,185,189,191,238,425,618,[760][761][762][763][764][765][766]. Some of these processes will be described below. ...
Calcium phosphate (CaP) bioceramics are widely used in the field of bone regeneration, both in orthopedics and in dentistry, due to their good biocompatibility, osseointegration and osteoconduction. The aim of this article is to review the history, structure, properties and clinical applications of these materials, whether they are in the form of bone cements, paste, scaffolds, or coatings. Major analytical techniques for characterization of CaPs, in vitro and in vivo tests, and the requirements of the US Food and Drug Administration (FDA) and international standards from CaP coatings on orthopedic and dental endosseous implants, are also summarized, along with the possible effect of sterilization on these materials. CaP coating technologies are summarized, with a focus on electrochemical processes. Theories on the formation of transient precursor phases in biomineralization, the dissolution and reprecipitation as bone of CaPs are discussed. A wide variety of CaPs are presented, from the individual phases to nano-CaP, biphasic and triphasic CaP formulations, composite CaP coatings and cements, functionally graded materials (FGMs), and antibacterial CaPs. We conclude by foreseeing the future of CaPs.
... The bond strength between the layer and the substrate increased steadily with increasing current, while the dissolution rate decreased remarkably. [30] ...
... Particulate debris formed by pieces of the broken coat-ing breaking off can also have adverse effects on the implant and surrounding tissue, which again may lead to implant failure. 16 Calcium phosphate coatings can be deposited through various techniques such as sputtering [17][18][19][20] electron beam deposition, 18 laser deposition, 21,22 plasma spraying, [23][24][25][26][27][28][29] and many others. Among these techniques, plasma spraying is the current commercial method for depositing HA and calcium phosphate coatings on orthopedic and dental implants. ...
... Based on these properties, therefore, a biomaterial should provide mechanical properties of the tissue to be regenerated and tissue/implant interface stability, as well as to be able to bone regeneration [10,11]. Several works reported bacterial cellulose with chemical changes in bacterial surface for hydroxyapatite adhesion [16,17]. ...
Bacterial cellulose has become established as a new biomaterial, and it can be used for medical applications. In addition, it has called attention due to the increasing interest in tissue engineering materials for wound care. In this work, the bacterial cellulose fermentation process was modified by the addition of chondroitin sulfate to the culture medium before the inoculation of the bacteria. The biomimetic process with heterogeneous calcium phosphate precipitation of biological interest was studied for the guided regeneration purposes on bacterial cellulose. FTIR results showed the incorporation of the chondroitin sulfate in the bacterial cellulose, SEM images confirmed the deposition of the calcium phosphate on the bacterial cellulose surface, XPS analysis showed a selective chemical group influences which change calcium phosphate deposition, besides, the calcium phosphate phase with different Ca/P ratios on bacterial cellulose surface influences wettability. XTT results concluded that these materials did not affect significantly in the cell viability, being non-cytotoxic. Thus, it was produced one biomaterial with the surface charge changes for calcium phosphate deposition, besides different wettability which builds new membranes for Guided Tissue Regeneration.
... Several methods are used for coating metals to improve their integration to the host bone. These coatings are deposited by different techniques including (but not limited to) physical vapor Deposition (PVD) [9], ion plating [10] and sputtering [11]. Using a variety of the above mentioned techniques, a wide range of bioceramic materials has successfully been deposited to improve significantly the mechanical properties of the materials on which they are deposited [12]. ...
... During the years, the bioceramic coatings used for biomedical applications were prepared by various deposition techniques, such as magnetron sputtering, ion beamassisted deposition, plasma spraying process, sol-gel, thermal spraying, electrophoretic deposition, pulsed laser deposition, dynamic mixing, dip coating, biomimetic coating, and hot isostatic pressing [38][39][40][41][42][43][44][45][46][47][48][49][50][51][52]. ...
The performance of present orthopedic implants and prostheses components made by metallic biomaterials is quite limited due to their corrosion in the human body. Therefore, it is important to develop methods for the biofunctionalization of the metallic surfaces by changes in the material’s surface composition, structure, and morphology, which leave intact the mechanical properties of metallic biomaterials. Thus, the performance and service life of dental and orthopedic implants made by metallic biomaterials will be significantly increased. These requirements could be satisfied if biocompatible coatings with unique combinations of properties were produced. The best choice for the surface functionalization of the metallic implants or their parts that are in direct contact with bone is the bioceramic coatings which are classified in three main groups: bioinert, bioactive, and bioresorbable. Bioinert coatings are those which have a minimal interaction with its surrounding tissue after implantation in the human body, such as oxides, nitrides, oxynitrides, carbonitrides, or carbide, due to their valuable properties such as high hardness, better wear and corrosion resistance, and good biocompatibility. Bioactive coatings present after implantation a good interaction with the bone by enhancement adhesion between the bone and implants. In the case of bioresorbable coatings, these are dissolved in contact with the bone and form a new bone. The aim of this chapter is the discussion about different bioinert, bioactive, and bioresorbable coatings prepared by magnetron sputtering used in biomedical applications such as dental or orthopedic implants and medical instruments. Moreover, the possibility to enhance the osseointegration and the antibacterial properties of the metallic implants used in dentistry and orthopedic surgery is discussed in this chapter.
... Several methods are used for coating metals to improve their integration to the host bone. These coatings are deposited by different techniques including (but not limited to) physical vapor Deposition (PVD) [9], ion plating [10] and sputtering [11]. Using a variety of the above mentioned techniques, a wide range of bioceramic materials has successfully been deposited to improve significantly the mechanical properties of the materials on which they are deposited [12]. ...
Biocompatible metals have been suggested as revolutionary biomaterials for bone-grafting therapies. Although metals and their alloys are widely and successfully used in producing biomedical implants due to their good mechanical properties and corrosion resistance, they have a lack in bioactivity. Therefore coating of the metal surface with calcium phosphates (CaP) is a benign way to achieve well bioactivity and get controlled corrosion properties. The biocompatibility and bioactivity calcium phosphates (CaP) in bone growth were guided them to biomedical treatment of bone defects and fractures. Many techniques have been used for fabrication of CaP coatings on metal substrates such as magnesium and titanium. The present review will focus on the synthesis of CaP and their relative forms using different techniques especially electrochemical techniques. The latter has always been known of its unique way of optimizing the process parameters that led to a control in the structure and characteristics of the produced materials.
... 2 9 10 Nevertheless a variety of technologies for coating HAp onto bio-medical metal surfaces have been developed. They included pulsed laser deposition, 11 12 plasma spraying, [13][14][15] ion beam sputtering, 16 solgel, 17 electrophoretic deposition, 18 and electrochemical deposition. 2 14 19 20 In recent years, the electrochemical deposition of HAp on metal or alloy surfaces has become technologically important for various applications. 2 In the present study, the influence of experimental conditions (such as H 2 O 2 content, applied potential, temperature, pH and reaction time) on the electrodeposition of HAp on TiN/316LSS substrate was investigated. ...
Hydroxyapatite (HAp) coatings were prepared on Ti6Al4V substrate by electrodeposition method from electrolyte solution containing Ca(NO3)2, NH4H2PO4 and NaNO3. The results show that the HAp coatings were single phase crystals of HAp. Scanning electron microscope (SEM) images present that HAp/Ti6Al4V have flake shapes which arrange to form like-coral agglomerates. In vitro test of the Ti6Al4V and HAp/Ti6Al4V in simulated body fluid (SBF) solution was investigated with different immersion times. pH of SBF solution decreased and the mass of materials increased. SEM images prove the formation of apatite on the surface of Ti6Al4V and HAp/Ti6Al4V. The corrosion current density during immersion time of substrate is always higher than the one of HAp/Ti6Al4V because the deposited HAp can protect well for the substrate.
... Attempts have recently been made to solve problems, the cold plasma, ion-plating [29] and the ion sputtering [28], which are a kind of physical vapor deposition (PVD), are used to produce implant materials consisting of a thin, homogeneous, and adherent Ca-P coating. Ion beam dynamic mixing (IBDM) was also introduced as a suitable technique for fabricating a thin and adherent ceramic layer [30]. This method is a combination of ion implantation and PVD, and has the advantages of a high deposition rate, producing defect-free transparent thin films, and excellent adhesion compared to conventional thin-film deposition techniques. ...
The implant material must have optimum surface compatibility with the host epithelial tissue, connective tissue, and bone tissue. Because, dental implants, which are partially exposed to the oral cavity, must have firm contact with tissues to prevent the bacterial infection. Such materials can be created under well-controlled conditions by modifying the surfaces that contact these tissues. The rough and grooved surfaced implant contributes to a more rapid cell migration and make osseointegration during wound healing. A number of chemical and physical methods for titanium and/or zirconium surface modification have already been established. Recently, plasma treatment can control surface physiochemical properties and affect protein adsorption for bioengineering. Moreover, the “motif-programming” methodology to “biologically” modify titanium and zirconium surfaces has created interfacing artificial proteins that endowed those surfaces with cell-binding activity. These technique should improve firm contact between tissue and dental implant.
... Many methods were developed to deposit HA for biomedical implant, including ion beam sputtering [10], sol-gel [11], electrophoretic deposition [12], pulsed laser deposition [13], plasma spray [14][15] and electrochemical deposition [3,7]. Among them, electrochemical deposition presents several advantages, like coating uniformity and possible coverage of biomedical substrates having complex shape [16]. ...
In this work, brushite and brushite/hydroxyapatite (BS, CaHPO4·H2O; HA, Ca10(PO4)6(OH)2) coatings were deposited on 316L stainless steel (316LSS) from a solution containing Ca(NO3)2·4H2O and NH4H2PO4 by a displacement reaction based on a galvanic contact, where zinc acts as sacrificial anode. Driving force for the cementation reaction arises from the difference in the electrochemical standard potentials of two different metallic materials (316LSS and Zn) immersed in an electrolyte, so forming a galvanic contact leading to the deposition of BS/HA on nobler metal. We found that temperature and deposition time affect coating features (morphology, structure, and composition). Deposits were characterized by means of several techniques. The morphology was investigated by scanning electron microscopy, the elemental composition was obtained by X-ray energy dispersive spectroscopy, whilst the structure was identified by Raman spectroscopy and X-ray diffraction. BS was deposited at all investigated temperatures covering the 316LSS surface. At low and moderate temperature, BS coatings were compact, uniform and with good crystalline degree. On BS layers, HA crystals were obtained at 50 °C for all deposition times, while at 25 °C, its presence was revealed only after long deposition time. Electrochemical studies show remarkable improvement in corrosion resistance.
Materials such as biocompatible metals, ceramics, composites, and polymers are used in the fabrication of biomedical implants which are used in the human body especially for the replacement of hard tissues. However, they degrade with time since they are subjected to different mechanical conditions and long-term exposure to fluids corrosion. Therefore, to curb these limitations, the surface properties are usually coated with thin metallic and nonmetallic materials. One such nonmetal is Hydroxyapatite (HA) coating which has the potential of mitigating these shortcomings and it is a biocompatible and bioactive material. This paper provides an overview of the existing literature on the sputtering of hydroxyapatite coating for biomedical applications with emphasis on the deposition conditions and parameters.
Additive manufacturing (AM) is being widely explored for engineering biomedical implants. The microstructure and surface finish of additively manufactured parts are typically different from wrought parts and exhibit limited bioactivity despite the other advantages of using AM for fabrication. The aim of this study was to enhance the bioactivity of selective laser melted Ti-6Al-4V alloy by electrophoretic deposition of nanohydroxyapatite (nanoHAp) coatings. The deposition parameters were systematically investigated after the coatings were deposited on the as-manufactured surface or after polishing the surface of the additively-manufactured sample. The surfaces were coated with nanoHAp suspended in either ethanol or butanol using different voltages (10, 30, or 50 V) for varied deposition times. The formation of the nanoHAp coating was confirmed by Fourier-transform infrared spectroscopy and X-ray diffraction. Microstructural analysis revealed that several conditions of the coating led to crack formation. The coated samples were subsequently heat-treated to improve the integrity of the coating. Heat treatment led to crack formation in several conditions due to thermal shrinkages. Coatings prepared using butanol were more uniform and had minimal cracks compared with the use of ethanol. Nanoindentation confirmed good stability and integrity of the nanoHAP coatings on the as-manufactured and polished surfaces. The coating on the as-manufactured sample exhibited higher hardness and lower elastic modulus as compared with the coating on the polished sample. In vitro study revealed that the nanoHAp coating markedly enhanced the attachment, proliferation, and differentiation of preosteoblasts on the alloy. These results provide a viable route to enhancing the bioactivity through deposition of nanoHAp with important implications for engineering additively manufactured orthopedic and dental implants suitable for better clinical performance.
In the present study, a biocompatible coating containing hydroxyapatite, alumina, and yttria-stabilized zirconia was deposited on the surface of titanium substrates by electrophoretic deposition method (EPD) and the reaction bonding process. The coating procedure was carried out using an electrical power supply device and a suspension of hydroxyapatite, aluminum, and yttria-stabilized zirconia nano-powders in isopropanol-acetone solvent (1:1). Iodine was used as a stabilizer. The electrical conductivity, pH, zeta potential, and mobility of the suspension were measured as a function of the iodine stabilizer concentration. The optimum amount of iodine was 0.6 g/l. The particle size distribution of the powders was measured at the optimal iodine concentration. The deposition was conducted at different voltages and durations, where voltage of 10 V and the deposition duration of 120 s led to the best results.
In this study, the improvement of mechanical properties by physicochemical changes of Ni coating layer after irradiation of high energy beam (HEB) was reported through spectroscopy, scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray fluorescence (XRF), X-ray photoelectron spectroscopy (XPS), and nanoindenter. This surface heating method of the irradiation of HEB has advantages of short heating time, uniform temperature distribution, and high heat efficiency by selectively heating desired parts, compared to other post-heat treatment methods. The main reason for this is that irradiation of a irradiation of HEB on the Ni coating layer causes a change in the energy amplitude of the dipole formed in the material. Therefore, the intermolecular friction caused the Ni coating layer to be oxidized to NiO even in a short time, improving the mechanical properties of the surface. In order to understand the diffusion effect of the irradiation of HEB, the indentation hardness, and the skin depth of the Ni coating layer was experimentally performed and theoretically predicted simultaneously.
The pitting corrosion of SS-316L in human body fluid leads the metallic prosthesis to lose its strength along with severe health consequences such as metallosis condition. Hence, an effective alternative for enhancing the biocompatibility of the SS-316L implant is the electrochemical deposition of a bioinert hydroxyapatite (HAP) coating over the metallic surface. A dense HAP coating was successfully developed on SS-316 L in a supersaturated electrolyte containing Ca+2 and PO43− ions. Electrochemical essays and SEM morphological observation showed the SS-316 L pitting corrosion caused by chloride containing body fluid. The effects of the electrodeposition time and the temperature of the supersaturated electrolyte were assessed using current–time transients, scanning electron microscopy, Energy-dispersive X-ray spectroscopy, Raman and X-ray diffraction analyses. The increase in the temperature promotes the HAP coating formation and accelerates the particles nucleation. An instantaneous HAP growth with no evidence for intermediate phase of HAP formation has been noticed.
The nanoscale hydroxyapatite (HAp) is a significant material applied for bone tissue engineering in the human body. This study focuses on the impact of vanadium addition on nano-sized HAp synthesized by sol-gel/hydrothermal technique and microwave device. The as-prepared nanocomposites were analyzed by X-ray diffraction (XRD), field emission-scanning electron microscopy (FE-SEM), energy-dispersive X-ray spectroscopy (EDX), Fourier-transformed infrared spectroscopy (FTIR), and Raman spectroscopy. The calculated crystallite size of the pure and V-HAp ranged from 15.73 nm to 20.77 nm, as supported by the XRD technique. The surface morphology of V-HAp samples is nanorods. Furthermore, the diffused reflectance helps to obtain the absorption spectra and the bandgap of the investigated samples. The dielectric constant and AC electrical conductivity are varied with the applied frequency and recorded at room temperature for HAp and different V-concentrations HAps. The gamma ray's absorption was also studied to consider the gamma attenuation of the tested samples using Cs-137 and Am-241 radioactive sources. The antimicrobial activity of the synthesized nanopowders was considered against pathogenic Gram-negative bacteria (P aeruginosa and Klebseilla sp), Gram-positive bacteria (Micrococcus sp and Bacillus subtilis), and yeast pathogen (Candida albicans). Vanadium-doped HAp nanostructured can be used as a multifunctional material in antimicrobial activity and gamma radiation shielding materials.
Hip prosthesis or hip replacement surgery becomes necessary when the hip joint has been badly damaged from any cause such as arthritis, malformation of the hip since birth, or abnormal development and damage from injury. Figures 16.1 and 16.2 show the anatomy of a natural hip. As can be seen, a natural hip is composed of a femoral stem (thigh bone) with a femoral head on top of it that articulates against the acetabular cup in the acetabulum. As all other joints, there exists a cartilage between the acetabular cup and the femoral head to lubricate their movement and facilitate the articulation. In an arthritic hip joint, the cartilage has been damaged, narrowed, or even lost by a degenerative process or by inflammation. Figure 16.3 shows an arthritic hip joint in which the cartilage has been damaged.
In this chapter, the authors discuss the fabrication and properties of calcium phosphate coatings on titanium (Ti) by radio-frequency (RF) magnetron sputtering. First, they address the necessity of surface modification of metallic biomaterials and the effectiveness of calcium phosphate coating. Next, they briefly review the processes used in the application of calcium phosphate coatings and present the effect of sputtering parameters on the phase and deposition rates of these coatings. Finally, the chapter discusses the performance of amorphous and crystalline (oxyapatite) calcium phosphate coatings on Ti based on in vitro and in vivo evaluations.
This paper presents hydroxyapatite (HA) coatings electrodeposited onto titanium by a new electrochemical approach: one precursor is present in the electrolysis cell, while the other precursor is dropwisely added, simultaneously with the application of an electrochemical potential. The addition order of the precursors was alternated, and the Ti substrate surface modifications were evidenced using various characterization methods. The coatings displayed higher crystallinity, with HA crystals organized into hemispheres, and a double ceramic layer configuration: one uniform base layer (submicrometric crystals), continuous in all cases and with higher density, and one upper layer (micrometric units), uniform only for longer deposition times and with lower density. Adhesion tests were performed to determine coating-substrate bonding strength. Artificial saliva solution tests conducted at 37°C for 30 and 60 days were followed by XRD and SEM characterizations. The coatings could be useful for dentistry or orthopaedics applications, favouring the implant connection with the living tissue.
Commercially available pure titanium surfaces were modified using dry process including ion implantation (Ca^+, N^+, F^+), ion plating (TiN, Alumina), and the application of oxide films (titania spraying, anodic oxidation). Ion-implanted surfaces consisted of Ti compounds with the implanted elements, titanates of the implanted elements, as well as titanium oxides. Calcium titanate and Ti-F compounds were primarily formed on the Ca-implanted and F-implanted titanium surfaces, respectively. Ion-plated surfaces had compositions similar to those of theraw materials for coating. TiN-coated surfaces may be effective in improving wear and corrosion resistance. Alumina-coated surfaces showed hydrophobicity and absence of Ca-ion adsorption. Oxide films created through titania spraying and anodic oxidation treatment consisted of titanium oxides with a thickness of more than several micrometers and 300 nm, respectively. Titania-sprayed films contained a certain amount of anatase. These results indicate that surface treatment by dry process is effective on surface modifications of titanium implants.
We examined the effects of nitric acid and heat treatments on titanium and Ti-6Al-4V alloy by measuring the dynamic contact angle, relative cell adhesion rates after 1 hour and 24 hours, and the cellular adhesive strength of L-929 cells using a cone and disk type viscometer.The dynamic contact angle was not influenced by 40% nitric acid, but was decreased by heat treatment.The relative cell adhesion rate after each treatment remained the same as the control value except for that after 1 hour treatment at 800℃.The percent of adherent cells decreased with longer application of shear stress.However, there was no difference in the percent of adherent cells with changes in the experimental conditions.Thus, a method other than contact angle should be used to evaluate cell adhesive strength.
Hydroxyapatite (HA, Ca10(PO4)6(OH)2) has been widely used as a coating material for dental implants for many years, due to its close similarity of chemical composition with bone material and its ability to bond with bone. In this study, a hydroxyapatite coating was formed on Ti substrate, employing the electrochemical coating method of cyclic voltammetry, in order to enhance the corrosion resistance. Formation of Hydroxyapatite on Ti is confirmed by the XRD and SEM analyses. Polarization curves revealed a substantial improvement in the corrosion potential from -289 to -193 mV (Ag/AgCl) and decrease in corrosion-current density, for the hydroxyapatite coatings in artificial saliva compared with pure titanium that showed positive role of HA on Ti corrosion behavior.
Recently, the problem of infection on implanted devices caused by the formation of biofilms has been recognized. Surface treatment to prevent the initial stages of bacterial adhesion and subsequent bacterial growth is the only possible solution against such infection. In this study, simple electrochemical treatment was used for introducing silver, an antibiotic agent, on the titanium surface. A porous oxide layer containing small amounts of silver was formed on the metal of the substrate. This was done by micro-arc oxidation using the electrolyte silver nitrate. The porous oxide layer was almost amorphous with a small fraction of anatase phase. The samples prepared using the electrolyte containing 0.04 mM or a higher concentration of silver nitrate showed an excellent antibacterial effect against both E. coli and S. aureus. However, the proliferation of osteoblast-like cells in the samples was not affected when a concentration of 0.5 mM or lower was used. Moreover, samples containing silver showed no-harmful effects on the process of bone differentiation. Furthermore, the calcification process of the cells on the samples treated with and without silver were much promoted than that on untreated Ti. Thus, we found that it is possible to use this optimum concentration of silver to realize the conflicting biofunctions; its antibacterial property and osteogenic cell compatibility.
Hydroxyapatite (HA), Ca10(PO4)6(OH)2, the main mineral component of natural bone (∼ 70%), shows the most desirable bone response among the bioactive materials. In the present study, HA coatings of approximately 2–3 µm thickness were deposited on Ti–6Al–4V substrate by KrF excimer laser (λ=248 nm, pulse repetition rate = 10Hz, pulse duration = 20 ns, Laser fluence = 3 J cm⁻²) ablation of HA targets. The deposition process was carried at room temperature under different chamber pressures (10⁻¹–10⁻⁴ Torr of oxygen). The morphology and structure of the deposited layers were studied by scanning electron microscopy and X–ray diffraction analysis. Mechanical and adhesive properties of the coatings were evaluated through the Nanoindentation and scratch test, respectively. The XRD analysis revealed that as-deposited HA film is amorphous. However, for biomedical applications HA coatings should be crystalline, because amorphous HA films easily dissolve in body fluids. The initially amorphous pulsed laser deposited thin films were annealed at 300 °C for 4 h in ambient air in order to restore the crystalline structure. This study reveals that the pulsed-laser deposition followed by post deposition annealing is a promising technique to produce ideal crystalline adherent HA thin films.
A bio-implant is a medical device to replace a missing biological structure, support
a damaged biological structure, or enhance an existing biological structure
which is in much use nowadays. In order to decrease the amount of implant infections
and prevent the implants from loosening or corrosion, coatings are applied
to the implant surface. There are several techniques by which these types of coatings
can be deposited. But many of these methods suffer from a major drawback
due to poor adhesion between the coating and the implant surface, which can
cause severe problems within a living body. This chapter mainly focuses on the various
coating deposition techniques with improved adhesion to the implant surface.
Aim
This study was performed to evaluate the biocompatibility of pure titanium and Ti-6Al-4V metals coated with hydroxyapatite (HA) by plasma spray using different plasma gas atmospheres.
Materials and methods
The cell viabilities for each HA-coated sample in an atmosphere of argon, argon—hydrogen, nitrogen, and nitrogen—hydrogen were studied using MTT assay and platelet adhesion test.
Results
The mean cell viabilities by MTT [3-(4,5-dimethylthiazol- 2-yl)-2,5-diphenyltetrazolium bromide] assay of samples coated with HA in argon—hydrogen plasma atmosphere showed maximum cell viability at different time intervals compared with other coating atmospheres of argon—hydrogen, nitrogen, and nitrogen—hydrogen. A statistically significant value of cell viability (p < 0.001) was observed between and within the groups of argon, argon—hydrogen, nitrogen, and nitrogen—hydrogen plasma gas atmosphere. The platelet adhesion study showed agglomerates of platelet cells in some isolated regions of HA for all atmospheres.
Significance
The results obtained in this study can serve as a guide for the development of new Ti-based HA-coated implants in different plasma gas atmospheres.
How to cite this article
Kotian R, Rao PP, Madhyastha P, Shobha KL, Rao BSS, Ginjupalli K. Cytocompatibility by MTT Assay and Platelet Adhesion of Ti and Ti-6Al-4V coated with Hydroxyapatite in different Plasma Gas Atmospheres. World J Dent 2017;8(1):28-36.
The present paper demonstrates that the cellular response on a Ti surface could be enhanced through surface treatment by an accurately focused beam of a low-power pulsed Nd:YAG laser. Focusing the beam leads to the generation of a laser-induced plasma on the target surface, which makes it possible to enhance the effect of laser irradiation. A chemically stable and thin layer of titanium dioxide (TiO2) was formed on the laser-treated substrate, while changes in the surface microstructure were hardly observed. This result indicates that the oxide formation was developed through a reaction to the plasma instead of an energy transfer from the laser to the surface. The resulting TiO2 layer suppressed the adsorption of the contaminant carbon on the Ti surface, which made it possible to maintain hydrophilicity, even after sterilization. In fact, the cellular adhesiveness and cell proliferation on the Ti surface were notably improved by the laser treatment despite the low power of 5 and 25 mJ·pulse− 1. On the other hand, differentiation of the osteoblast-like cells was not facilitated by the laser treatment.
In the paper, hydroxyapatite coatings enriched with Ti were prepared as a possible candidate for biomedical applications, especially for implantable devices that are in direct contact with bone. The hydroxyapatite coatings with different Ti contents were prepared by an RF magnetron sputtering method on a Ti6Al4V alloy using pure hydroxyapatite and TiO2 targets. The Ti content was modified by changing the RF power fed to the TiO2 target. The formation of the hydroxyapatite compound was not influenced by the addition of Ti. The Ca/P ratio of the Ti-doped hydroxyapatite coatings was found to be in the range between 1.64 and 1.68, which is close to the stoichiometric hydroxyapatite coating. The roughness of the doped hydroxyapatite coatings was augmented by increasing the RF power on the TiO2 cathode. The addition of Ti led to an increase in the contact angle of the hydroxyapatite coatings. The in vitro corrosion performance of the Ti6Al4 alloy was improved significantly by the hydrophobic hydroxyapatite coatings with and without the Ti addition. A surface with a higher Ti concentration and water contact angle exhibited a better corrosion resistance in simulated body fluid at 37 °C. Therefore, the deposition of a hydrophobic Ti-doped HA coating could be a promising surface treatment for the improvement of the electrochemical behaviour of metallic implants.
Medical-grade alloys, such as Ti-6Al-4V, have been used for fixation of fractured bone and for the total replacement of defective bone. Their bioactivity could be improved by applying a bone-like apatite layer onto their surfaces. This, in turn, enhances their integration with the surrounding tissues upon implantation. In addition, the presence of a bioactive bone-like coating minimizes the likelihood of corrosion. Various methods are known for the formation of apatite coating onto Ti-6Al-4V, among which sputtering has shown its promise as a simple direct method. In the current work, a sputtering technique was used to develop a 300 nm-thick bone-like apatite layer onto Ti-6Al-4V. Structural composition, integrity and morphology of the as-coated and thermally treated coatings were investigated. Coated substrates were further evaluated after soaking them in a simulated body fluid (SBF) for up to 14 days. Results showed the formation of an amorphous apatite layer onto the alloy, that was further shown to partially crystallize upon heat treatment. As a result of SBF treatment, the apatite layer was found to remodel through a dissolution-precipitation mechanism due to its amorphous and non-stoichiometric nature, forming a smooth layer with better homogeneity and decreased surface roughness. Electrochemical analysis of the coated alloys showed the enhanced corrosion protection of the alloy surfaces by coating them with apatite. In addition, pre-grinding of the alloy surfaces before the formation of the coating was also found to improve the corrosion inhibition of the alloy surfaces in aqueous media.
The biomaterial science shows an important interest in the production of biocompatible ceramic-like coatings capable to improve the interaction of metal implant to the living tissue. Among the materials used for coating fabrication the most interesting is hydroxyapatite (HA) due to its similarities with the mineral part of the bone. Coatings were prepared by radio-frequency (RF-) magnetron sputtering technique, starting from pure HA. The HA thin films were characterized in terms of structure and chemical composition by many techniques such as Fourier spectroscopy (FTIR), X-ray diffraction (XPS), Rutherford backscattering (RBS) and nanoindentation technique (Vicker's indenter). There were established that deposited coating has the structure of crystalline hydroxyapatite or amorphous one with calcium to phosphorus ratio (Ca/P) in the range 1.53 - 3.88. Calcium phosphate coating with the structure of hydroxyapatite reduces the nickel release rate from NiTi substrates in aqueous saline solution over 7 - 10 times.
Bioglass, 45S5 containing 45% SiO2, 6% P2O5, 24.5% CaO and 24.5% Na2O all in weight percent, was plasma sprayed onto a titanium substrate with and without 60 Al2O3 40 TiO2 as a bond coating. Mechanical properties were evaluated by following the ASTM C633 method and the microstructural characterization has been carried out by using scanning electron microscope. Results indicate that the bonding strength of bond coatings is three times higher than of the coatings that are directly applied to the surface. It has been observed that there is a uniform coating layer with a thickness of 110 mum and that there was not any reaction observed at the coating-metal interface.
The tarnish test, the wear test and the bending test of TiN Ion-plated specimens for various alloys were performed.Results(1)The TiN film had the colorimetric properties which were the hue of about 2.5Y, the value of about 6 and the chroma of about 4 by the standard color chip of JIS.(2)The resistance to tarnish of alloys was improved by Ion-plating.(3)The wear of TiN film didn't depend on mechanical properties of the base(substrate)material if the maximum depth under the wear test was less than Ion-plated film thickness.(4)Wear amounts of TiN film were large to inorganic materials such as TiN film porcelain and enamel but small to metallic materials such as Type IV gold alloy and Ni-Cr alloy.(5)Wear amounts of Ag-In alloy and porcelain were large, but those of Type IV gold alloy, Ni-Cr alloy and enamel were relatively small to TiN film.(6)The composite materials which TiN films of 3μm thickness were plated on both sides of 0.3mm thickness-substrate(Ag-Cu alloy)gave 20 percent increase in the elastic coefficient and 50% increase in the proof stress under the bending test.
The bending characteristics and corrosion resistance were investigated using TiN ion-plated specimens of Al-Cu, Al-Mg system wrought alloys and Al-Si system casting alloy.Results:1.Bending characteristics 1)The proof stress values of these specimens ranged from 91.1 to 231.1MPa.Those of ion-plated materials to wrought used alloy, however, reduced to half of those of the original materials.It was suggested that this was due to the thermal effects of ion-plating procedures.2)The elastic coefficients of these specimens ranged from 7.1 to 8.1×10⁴MPa.3)It was estimated that the practical thickness of aluminum system alloys ion-plated for use as a denture base was from 0.8 to 1.3mm.2.Corrosion resistance 1)Pitting corrosion was only observed on ion-plated specimens of Al-Cu system alloy by means of immersion in an artificial saliva.2)From the results of an electrochemical test, it was suggested that the material had a tendency to give rise to pitting corrosion when the breakdown potential was closed to the corrosion potential.3)The current density of ion-plated specimens of Al-Mg and Al-Si system alloy decreased to 1/50 or 1/170 in comparison with that of original specimens at zero voltage on an anodic polarization technique in an artificial saliva.
Two hydroxyapatite-coated IMZ implants, extracted for psychiatric reasons, were prepared using a cutting-grinding system and studied with scanning electron microscopy and laser scanning microscopy. The examination showed tissue integration with a very intimate bone-implant contact. Laser scanning showed the presence of a layer of dark staining material, resembling a reversal line of bone tissue, at the bone-implant interface, which could be the result of a film of organic material deposited on the bone and hydroxyapatite surfaces.
The ion beam deposition method for the formation of compound films can easily control the composition of each element. The authors have prepared Al//xN//y films by the evaporation of aluminum and the bombardment of N//2 ions with 30-40 keV. The properties of the films have been studied by TEM. In this work, aluminum nitride films were made by mutual deposition of aluminum and nitrogen. The former element was evaporated by electron bombardment and the latter one was implanted into the Al layer. The films were checked by the RBS of He ions and X-ray diffraction.
The surface film formed on titanium in a neutral electrolyte was characterized using XPS with an angular-dependent technique and argon-ion sputtering in order to predict the structure of the substance formed on titanium in a biological system. The results revealed that a calcium phosphate was naturally formed on titanium oxide, indicating that the surface layer of the titanium in the electrolyte consists of two parts: calcium phosphate and titanium oxide (essentially TiO2). The calcium phosphate contained phosphate in the form of PO3−4, HPO2−4 and H2PO−4. The proportion of PO3−4 was the largest among the phosphates and approximately 60% of the phosphate was PO3−4. The calcium phosphate also contained hydroxyl groups and bound water. The formation and growth of the calcium phosphate was caused by the adsorption of hydrated phosphate ions by the titanium surface, the release of protons from the phosphate ions, and the adsorption of calcium ions by the phosphate.
A method has been developed for the consistent adherence of flame-sprayed ceramic coatings to Vitallium. The critical step involves etching the metal by the anodic polarization technique. This procedure allows complex geometrics to be corroded evenly, and, by suitable choice of etching solution and conditions, enables any metal to be substituted. The bond is capable of sustaining more severe deflections than are experienced during intraoral function. Despite the number of cracks generated during testing, the ceramic layer remains intact. The ceramic-metal bond is mechanical. The corroded surface provides greater surface area, thus permitting a number of retention sites. Analysis of the ceramic microstructure finds it to be suitable for tissue ingrowth.
The purpose of this research was to determine the nature of the residual hydroxyapatite (HA)-coated implant surface after treatment with various chemotherapeutic modalities, including: citric acid, chlorhexidine gluconate, hydrogen peroxide, tetracycline HCl, stannous fluoride, polymyxin B and a prototype plastic Cavitron tip. Implant surfaces were evaluated macroscopically, microscopically (scanning electron microscopy (SEM)) and spectrometrically (energy-dispersive spectrometry and X-ray diffraction). HA-substrate bond strength and dissolution testing was also performed for surfaces treated with a supersaturated citric acid solution. All treatments left either microscopic residues or a loss of surface roughness when viewed on SEM. A 30- to 60-s application of citric acid left a significantly greater coating thickness than all other treatments, whereas a 3-min application of citric acid removed significantly more HA than untreated controls. Significant changes in Ca/P ratios were seen with most treatments. The clinical significance of this phenomenon is not known. No treatments altered the crystallinity of the residual HA coating. A 1-min application of citric acid did not significantly alter the tensile bond strength of the coating to the substrate. The clinical significance of these findings is not known at present. However, when taken with results from previous studies, it appears that in treating the infected HA-coated implant surface, a 30- to 60-s application of citric acid (pH 1) may be beneficial in detoxifying the HA coating prior to regenerative procedures. Further in vitro and in vivo studies are necessary to evaluate the biological response to citric acid when used to detoxify the infected implant surface.
Hydroxyapatite-coated and titanium-coated IMZ dental implants were investigated in an animal study. The implants were placed in the distal femurs of rabbits. Six months after placement, histomorphometric evaluation of the bone-to-implant contact was conducted. The hydroxyapatite-coated specimens demonstrated significantly more direct bone contact compared to the titanium-coated controls.
The method used to apply hydroxyapatite to implant surfaces may affect the thickness and ultimately the physical properties of the coating. This study investigated and compared the healing rates of bone around commercially pure titanium implants and titanium implants sputter-coated from a hydroxyapatite target. Forty-five sputter-coated implants and an equal number of noncoated titanium implants were placed into 15 partially edentulated dog mandibles. The implants were removed at three time periods and were evaluated mechanically and histologically. A multiple analysis of variance indicated that the interface bond strength was statistically greater (p less than 0.01) for the sputter-coated implants. Histologic analysis of the bone-implant interface demonstrated that coated implants had nearly twice the percentage of direct bone contact compared with noncoated implants. The results indicate that implants sputter-coated from a hydroxyapatite target will accelerate the healing of bone at the implant interface.
Ion beam sputter deposition was used to produce thin calcium phosphate coatings on titanium substrates. Structure, solubility and bond strength of the as-sputtered and heat treated coatings were evaluated. X-ray diffraction (XRD) analysis of the heat treated coatings revealed a hydroxyapatite-type structure. The heat treated coatings were found to have significantly lower solubility as compared to the amorphous as-sputtered coatings. Although the crystalline coatings exhibited the lowest solubility, in general, the bond strengths were lower for the heat treated coatings.
The frictional coefficients were measured for four wire alloys against the flats of polycrystalline alumina cylinders using a low load, low velocity, single pass device. Ion-implantations of titanium into polycrystalline alumina flats and nitrogen into beta-titanium wires reduced the static and kinetic coefficients from 0.50 and 0.44 before implantation to 0.20 and 0.25 after implantation, respectively. These results are similar in magnitude to frictional coefficients for unimplanted, control couples of stainless steel, cobalt-chromium, and nickel titanium wires against polycrystalline alumina flats. For orthodontic applications, we conclude that more efficient and reproducible appliances can be engineered for tooth movement if ion-implantation is used to reduce the abrasion of beta-titanium by polycrystalline alumina.
The aim of this study was to obtain more information about the bone reaction to titanium and hydroxyapatite (HA)-coated titanium implants during the first 3 months after implantation. Therefore, uncoated and coated implants were inserted into the tibia of rabbits for various implantation periods. The histological results demonstrated that although there were no marked differences in bony reaction at the cortical level to the different implant materials, HA-coating appeared to induce more bone formation in the medullary cavity. It was also noted, that 3 months after insertion loss of coating thickness had occurred.
To improvement the brittleness of hydroxyapatite (HAp) coated on titanium alloy (Ti-6Al-4V), a thin ceramic layer was formed by means of the RF ion-plating method. The alloy substrates were coated with HAp at 1, 3 or 5 microns thickness and heat-treated at 500 degrees C for 4 hours. Properties of HAp-coated alloy were evaluated by characterization of the ceramic films both before and after heat-treatment, as well as by bending, electrochemical and dissolution tests. HAp-coated film had a slightly higher Ca/P ratio than the original material and was stoichiometrically Ca10(PO4)6(OH)2 by EPMA analysis. HAp was mainly recognized crystallographically by XRD analysis of the films after heat treatment, though it was hardly recognized on before heat-treatment film. These coated materials had a residual strain ranging from 0.3 to 0.7% without causing cracks in the HAp films with the three-point bend testing. Electrochemically, it was confirmed that the corrosion resistance of the Ti alloy was improved by any coating process. The amounts of Ca released from HAp coated film in 0.9% NaCl solution tended to increase with films that were 3 and 5 microns in thickness, but there were no significant differences in Ca released from film before and after heat treatment.
To evaluate cancellous allogenic bone graft incorporation into porous-coated implants, the fixation of titanium alloy-(Ti) and hydroxyapatite-(HA) coated implants with and without bone graft was compared. An unloaded model with unilateral carragheenin-induced osteopenia of the knee was used in 12 mature dogs. Ti- and HA-coated cylinders were implanted in the distal femoral condyles and centralized in 2-mm overreamed drill holes. Allogenic, fresh-frozen (-80[degrees]) cancellous bone graft was packed around the implants in six dogs. In a matched group of six other dogs, the implants were left in overreamed canals without bone graft. After six weeks the interface shear strength of grafted Ti-coated implants had significantly increased compared to the nongrafted Ti implants.
However, HA coating used without bone graft was capable of enhancing the bone-implant interface shear strength to nearly the same degree. The fixation of grafted Ti- and HA-coated implants was equal. No significant difference in implant fixation was found between osteopenic and control bone. Histomorphometric evaluation of mineralizing surfaces in direct contact with the implant confirmed the results from the push-out test. Boneimplant fixation when using allogeneic fresh-frozen cancellous bone graft in osteopenic and control bone was enhanced by hydroxyapatite coating but the HA coating alone appeared to offer almost the same improvement in anchorage in 2-mm defects. Loss of bone stock around loose prosthetic implants often requires bone grafting. However, because of anatomic constraints in joint prosthetic surgery, a complete filling of defects with bone graft is difficult, and areas of gaps between bone and implant will remain. Provided mechanical stability of the prosthesis, the results reported here suggest that these areas will probably be filled early with new mineralizing bone if the prosthesis is coated with a thin layer of hydroxyapatite.
(C) Lippincott-Raven Publishers.
Threaded hydroxylapatite-coated implants of commercially pure (CP) titanium were inserted in the rabbit tibial metaphysis. Uncoated CP titanium screw implants inserted in the contralateral leg served as controls. After 6 weeks and 1 year postinsertion, the semiloaded implants were histomorphometrically analyzed. While not significant, there was more direct bony contact with the hydroxylapatite-coated implants after 6 weeks of follow-up. One year after insertion, there was significantly more direct bone-to-implant contact with the uncoated CP titanium controls.
7 clinically stable, "osseointegrated", titanium implants, inserted in human jaws for 1-16 years, were retrieved for morphological analysis of the bone-titanium interface, using 3 different preparation techniques. The bone-titanium interface varied as judged from light microscopy of ground sections. The threads of the implants were well filled (79-95%) with dense lamellar bone as quantified with morphometry. A large fraction of the implant surface (56-85%) appeared to be in direct contact with the mineralized bone. In general, the non-bone areas consisted of pockets with osteocytes, bone marrow tissue and/or vessels. Sections were prepared for light microscopy and transmission electron microscopy using a fracture technique, where the implant was separated from the embedded tissue before sectioning, and an electropolishing technique, where the bulk part of the implant was electrochemically removed. In areas judged as direct mineralized bone-titanium contact in the light microscope, the interfacial structure varied at the ultrastructural level. In areas along the interface, unmineralized tissue was present either as a narrow 0.5-1 micron wide zone containing collagen fibril or as deeper pockets containing osteocytes or vessels. In areas with mineralized bone contact, an amorphous granular layer (100-400 nm wide) with no mineral was observed in the innermost interface bordering the mineralized bone, with an electron-dense lamina limitans-like line (approximately 50 nm thick). It is concluded that the bone-titanium interface of the 7 clinically retrieved titanium oral implants examined in the present study bone was heterogenous. In areas of a direct mineralized bone-titanium contact at the ultrastructural level, mineralized bone reached close to the implant surface, but was separated by an amorphous layer, being 100-400 nm thick.
Ti4+ and V5+ ions were studied in two biologically relevant in vitro test systems to determine their effect on hydroxyapatite (HA) formation. System 1 involved direct HA precipitation from solution, and system 2 dealt with the growth of HA seed crystals. The experiments were carried out in a pH-stat by continuously recording NaOH uptake, which follows HA formation kinetics, at pH 7.4, 37 degrees C, and 0.15 M NaCl. In systems 1 and 2, Ti decreased HA formation kinetics in a dose-related manner without delaying the onset of HA formation. For V, the rate of HA proliferation decreased in system 1 in a dose-related manner, but the curves displayed a complicated shape. In system 2, V brought about a decrease in the HA seeded growth rate. Previous work has shown that Al blocks HA proliferation by adsorbing to active growth sites on the surface of HA crystals. By contrast, in this study V was found not to be adsorbed to the surface of HA. The mechanism of action of V probably involves the poorly understood hydrolysis and solution complex formation chemistry of the metal ion. We have shown here that V ions form V-PO4 complexes in solution in the HA formation systems; undoubtedly these are involved in the mechanism of V inhibition of HA formation. On the other hand, Ti was shown to bind to the surface of HA crystals in this study, which means that the ion may poison active crystal growth sites, as does aluminum. Ti-6Al-4V alloy is widely used in cementless total hip implants. Previous studies have shown that Ti concentrations 10 to 100 times higher than used here accumulate in osseous tissues around porous Ti implants in dogs 6 to 12 months after implantation. Ions leaching out over long periods of time into the implant interface could interfere with the normal osteoid mineralization and remodeling processes of bone in that region, which would result in subsequent loosening of the implant. This research suggests that further in vitro and animal studies should be carried out to determine the extent of Ti and V ion leaching from implants and their effect on tissue mineralization.
In this experiment hydroxylapatite-coated dental implants were submitted to a wear test in order to study their resistance to toothbrushing. After 20,000 double brush strokes the coating had disappeared in some places. It was concluded that the wear resistance of the coating was not good enough to withstand longer brushing periods.
This article addresses three aspects of the mechanical and biological properties of bioreactive glasses. First, it describes the composition and the relationship between the composition and bonding and its influence on the bone bonding mechanism and the rate of bond formation. Second, the mechanical properties of bioglass are dealt with. It is shown that the approaches to use bioglass in highly stressed applications, have met with various degrees of success. Third, the issue of the effect of loading on the glass properties and, above all, on the glass bonding properties is discussed.
Hydroxyapatite from two sources was electrophoretically deposited onto flat titanium plate material. Depending upon the deposition conditions various changes in the structure of the ceramic were identified. A well-adhering Ti-P compound was present at the interface. Hydroxyapatite oxygenated to various degrees and tetracalcium phosphate were reproducibly formed in the coating.
Bone tissue ingrowth in porous materials is enhanced by the deposition of bioactive calcium phosphate ceramic linings onto the pore walls. These bioactive coatings can be deposited using several methods which yield a variety of coating efficiencies and thereby influence the mechanisms and kinetics of ion release from the metal. We analyzed the effect of plasma-spraying hydroxyapatite onto titanium and cobalt-chromium alloys by measuring the release of Ti, Al, V, Co, and Cr in vitro. Plasma-sprayed coatings significantly reduced the Ti and Al release from titanium-based alloy specimens. The tendencies of release from the cobalt-based specimens are less pronounced. The data substantiate that neither localized enhanced passive dissolution of metal ions nor ceramic shielding of the metal occurs. The Scanning Auger Electron Microprobe Spectroscopic data suggest that the dissipation of thermal and kinetic energy of the ceramic particle at the time of impact can produce compositional and structural changes in the metal surfaces. The resulting effects are significant for the titanium alloy but less significant for the Co-Cr alloy system.
Four coating techniques were evaluated to determine which is most suitable for producing a dense, highly adherent coating onto metallic and ceramic implant materials. Two of the selected coating methods have serious limitations for use in this particular application, and did not meet the specified criteria for satisfactory coating as defined in the initial stages of the study. For example, the dip coating-sintering technique was judged to be unsatisfactory because of the adverse effect of the high-temperature sintering cycle on the mechanical properties of the metallic substrate materials. These materials could not be used in load-bearing applications because of the excessive grain growth and loss of the wrought structure of both the commercially pure Ti and Ti-6Al-4V substrates, and the loss of ductility in the cast Co-Cr-Mo alloy. Another area of concern was that bond strength between the HA coating and the substrate was not high enough to insure that interfacial failure would not occur during the lifetime of the implant. The immersion-coating technique, in which the metal substrate is immersed into the molten ceramic, was shown in a previous study to be the best method of coating a bioreactive glass onto a Co-Cr-Mo implant. Heating HA above its melting temperature, however, caused undesired compositional and structural changes, and upon solidification very limited adherence between the modified ceramic and substrate material occurred under the conditions of this study. The HIP technique, in which the Ti powder substrate and the HA powder coating are sintered together in a high-pressure autoclave, shows great promise for the fabrication of high-quality composite implants. Initial studies have indicated that high-density Ti substrates with a small grain size that are well bonded to a dense HA coating can be produced under optimum conditions. Sintering and densification additives, such as SiO2 powder, do not appear to be necessary. The main drawback to this technique appears to be the reaction of the encapsulating material--whether soda glass, steel, or fused silica--to the HA coating. More extensive testing will necessary to determine the ideal conditions for the HIP technique, as efforts on this technique were discontinued in order to concentrate on the HIP technique, as efforts on this technique were discontinued in order to concentrate on the optimization of the sputter-coating technique so that coated implants for an animal study could be produced on schedule. Based on the results of this study, sputter coating appears to be the method of choice for forming a dense, adherent coating of HA onto a metal substrate.(ABSTRACT TRUNCATED AT 400 WORDS)
Experimental implants of polycarbonate covered with a thin metallic layer were inserted in the rabbit tibial metaphysis. The implants had either a magnetron sputtered 316 L stainless steel or commercially pure titanium surface (or an evaporated commercially pure titanium surface). The aim of the experiment was to investigate the interfacial arrangements between bone and the coatings used. Three months after implant insertion, the animals were sacrificed and the intact interface between bone and metal analysed using ultrastructural techniques. In the case of stainless steel a coat of 1-2 cellular layers separating the bone from the metal was found. Inflammatory cells were abundant as well as a wide proteoglycan coat lacking collagen filaments. In the case of titanium there were no cells in the interface which consisted instead of a proteoglycan layer of about 200-400 A width. Bundles of collagen appeared at a minimum distance of 1000-2000 A from the metal surface. Calcium deposits were sometimes seen in direct contact (resolution level 30-50 A) with the titanium oxide. There were no ultrastructural differences in tissue reactions when magnetron sputtered titanium surfaces were compared with evaporated ones.
Bioactive glass ceramic coatings have been proposed for cementless prosthetic fixation. However, a coating procedure that results in a bond of adequate strength with the metal substrate is one of several factors that has to be resolved. In this work a glass ceramic coating was plasma flame sprayed onto a titanium substrate with and without molybdenum as an intermediate bond coating. The higher bond strength of the compound (20 MN m-2) compared to the simple (6 MN m-2) coating could be due to an increased roughness offered by the molybdenum surface, and possibly improved chemical bonding to the glass ceramic.
Ceramic has excellent properties. However, the brittleness of ceramic is one of the major problems. Coating ceramic on stronger substance materials may be one of the ways to overcome this problem. In this study, stainless steel (316L) coated with titanium nitride ceramic (TiN), produced by using a physical vapor deposition method, was investigated. The results indicated that although the yielding strength was decreased by exposing the material to 550 degrees C, the grain structure did not change. Stainless steel with 3.0 micron TiN coating demonstrated high resistance to bending stress and friction. In addition, this material displayed sufficient fatigue strength for an orthopaedic implant after 10(7) loading repetitions. Based on organ cultures and animal experiments, the biocompatibility of TiN coated stainless steel appeared to be superior to uncoated stainless steel. The TiN coating dissolved in H2O2 although it was stable to HNO3. In conclusion, titanium nitride ceramic coated stainless steel appears to be a promising material for implantation. However, further investigation is necessary for a long term results as an implant material.
Radiofrequent magnetron sputtering was used to produce calcium phosphate coatings on metal and plastic substrates. Scanning electron microscopy showed that the deposited films had a uniform thickness and a dense columnar structure. Energy-dispersive X-ray analysis, X-ray crystal diffraction and atomic absorption spectrometry demonstrated that the sputtered layer was well-crystallized calcium phosphate ceramic with a Ca/P ratio varying between 1.9 and 2.5. The biocompatibility of the coatings was determined by in vitro and in vivo experiments. It was found that the coatings were biocompatible without any sign of adverse tissue reaction. It was concluded that magnetron sputtering is a promising method for forming a biocompatible ceramic coating onto an implant material. Nevertheless, several problems have to be solved before magnetron sputtering can be used on a routine basis for the production of Ca/P coatings.
Dental implants obtained from four suppliers were analyzed by electron spectroscopy for chemical analysis and scanning electron microscopy. Three of the implants were delivered in a sterilized condition, while the fourth implant was delivered in a plasma-sprayed condition. The covering oxide layer consisted mainly of TiO2. Divalent and trivalent states of titanium were also detected, showing that TiO and Ti2O3 layers occurred. The thickness of the oxide formed on the plasma-sprayed implant was 3.4 nm. The oxide thicknesses of the sterilized implants were 4.6 +/- 0.4 nm. The surfaces of all samples were covered with organic contaminants. A strong fluorine signal was obtained from one sample, indicating that the supplier etches the implants in hydrofluoric acid. Calcium and zinc were found on the surfaces of all samples from one supplier, while calcium and silicon were found on the surfaces of the implants from another supplier. It is suggested that inorganic contaminants should be avoided because these species can possibly provoke the dissolution of titanium.
Hydroxyapatite-coated and uncoated titanium screws were inserted in the rabbit tibial metaphysis and evaluated by histomorphometry after 6 months of follow-up. There was no difference in direct bone contact between the HA-coated implants and the uncoated controls. The effect of HA-coating on screw-shaped implants seems to be uncertain, in contrast to unthreaded cylindrical designs, where there is more abundant documentation in favour of HA-coated implants.