Anodic Spark Deposition Research Articles

Osseointegration of Multiphase Anodic Spark Deposition Treated Porous Titanium Implants in an Ovine Model

Modification of titanium oxide by multiphase anodic spark deposition (ASD) has the potential to increase bioactivity and hasten osseointegration and biological fixation in uncemented arthroplasty. This study assessed the in vivo performance of control (Ti), plasma-sprayed HA-coated (TiHA) and ASD (Biospark) treated (TiAn) porous titanium implants with a solid core using a standard uncemented implant fixation sheep model. Cortical interfacial shear-strength and bone ingrowth in cortical and cancellous sites were quantified following 12weeks in situ. Ultimate shear-strength for the Ti, TiHA and TiAn coatings was 33±9.5, 35.4±8.4 and 33.8±7.8MPa, respectively, which was limited by coating delamination. ASD treatment was associated with significantly higher mean bone ingrowth at both sites. These results support the osteoconductive potential of the BioSpark treatment of porous titanium.

A Novel Silicon-Based Electrochemical Treatment to Improve Osteointegration of Titanium Implants

Titanium and its alloy represent the most commonly used biomaterials worldwide designed for bone-contact under-load applications, which often require specific mechanical properties. In particular, a large number of different biomimetic surface treatments have been developed to speed up the osteointegration process, which facilitates a reduction in recovery time. The aim of this work is to investigate the physical-chemical, mechanical and bioactivity properties of an innovative biomimetic treatment on titanium performed using Anodic Spark Deposition (ASD) electrochemical treatment. The proposed ASD treatment was obtained in an electrochemical solution containing silicon, calcium, phosphorous and sodium followed by an alkali etching. Surface morphology was characterized using SEM and laser profilometry. Chemical and structural composition was assessed by EDS, ICP/OES and XRD analysis. Vickers micro hardness and static contact angle measurements were performed to assess the surface mechanical properties and wettability. The proposed anodization treatment was capable of providing a chemical and morphologic modified titanium oxide layer, adherent and characterized by superhydrophilic properties. The microporous morphology was enriched by calcium, silicon, sodium and phosphorous.After incubation in Kokubo's Simulated Body Fluid (SBF) the treatment showed very high mineralization potential compared to the reference surfaces, accounting for a deposited hydroxyapatite layer as thick as 12 μm after 14 days of SBF incubation. On the basis of the results obtained in this study, we believe that the novel silicon-based ASD biomimetic treatment represents a promising treatment capable of enhancing the osteointegration of titanium for dental and orthopedic applications.

Mesenchymal Stem Cell Differentiation on Electrochemically Modified Titanium: An Optimized Approach for Biomedical Applications

To speed up the osteointegration process, surface-treated titanium has been widely used in dental and orthopedic applications. The present work describes a new silicon-based anodic spark deposition (ASD) treatment and investigates the properties of the surfaces obtained, focusing on their capability to modulate the osteogenic differentiation potential of adult mesenchymal stem cells (MSCs). The surfaces examined were obtained from commercially pure grade 2 titanium by a single-step ASD (SUM) eventually followed by a thermal treatment in alkali solution (SUMNa), while acid-etched titanium (AE; NextMaterials s.r.l.) was selected as a control. Their morphology, elemental composition, crystallographic structure of the Ti2O layer, wettability and topography were evaluated by scanning electron microscopy, energy-dispersive X-ray spectroscopy, thin-film X-ray diffraction, contact angle measurements and laser profilometry, respectively. MSCs' response to surface properties was assessed by examining cell morphology and viability by scanning electron microscopy and Alamar Blue assay®, while their osteogenic differentiation potential was investigated by evaluating the levels of the enzyme alkaline phosphatase (ALP) and the degree of calcium accumulation by Alizarin Red-S (AR-S) staining. The proposed ASD treatment has allowed the obtaining of surfaces with round-shaped micrometric pores, enriched in calcium, phosphorus and silicon and significantly more wettable than controls; furthermore, the treatment has been shown to promote MSC proliferation and the degree of in vitro mineralization. The described ASD treatment may be an effective technique to modify the surface cues of titanium implants, aiming at enhancing the conveying of osteoprogenitor cells and their functional differentiation in bone cells.

Multi-step anodizing on Ti6Al4V components to improve tribomechanical performances

This work presents the production and characterization of a controlled electrochemical modification of titanium surfaces, consisting of a two-step anodic spark deposition (ASD) process and a barrel finishing. The treatment was performed on titanium alloy Ti6Al4V, as most representative titanium alloy used in mechanical and aeronautical applications, where improved adhesion and tribological performances are required. FIB/SEM microstructural observations, nanoindentation, scratch, fretting tests and wear and friction tests were carried out both on laboratory specimens (planar pellets, 1in. diameter) and on Ti6Al4V bolts of different shapes and sizes, to investigate the effect of a three dimensional shape on the correct execution of the electrochemical treatment and on the coating's mechanical performance. The formation of a double layered coating was observed, with a slightly decreased surface hardness and stiffness compared to the metallic substrate and increased scratch and fretting wear resistances, thanks to an excellent adherence to the substrate, an optimal value of the hardness to modulus ratio (H/E) and a marked decrease of the friction coefficient. The proposed coating procedure could be therefore a suitable solution for those applications where low friction, wear resistance under low load sliding contact and corrosion resistance are required.

A Novel Antibacterial Modification Treatment of Titanium Capable to Improve Osseointegration

Among the different causes of orthopedic and dental implant failure, infection remains the most serious and devastating complication associated with biomaterial devices. The aim of this study was to develop an innovative osteointegrative and antibacterial biomimetic coating on titanium and to perform a chemical-physical and in vitro biological characterization of the coating using the SAOS-2 cell line. We also studied the antibacterial properties of the coating against both Gram-positive and Gram-negative bacteria strains. An electrochemical solution containing silicon, calcium, phosphorous, sodium, and silver nanoparticles was used to obtain the antibacterial by Anodic Spark Deposition (ASD) treatment. Surface morphology was characterized using SEM and laser profilometry. A qualitative analysis of the chemical composition of the coating was assessed by EDS. The adhesion properties of the coating to the titanium bulk were performed with a 3-point bending test. SAOS-2 osteoblastic cell line spreading and morphology and viability were investigated. The bacterial adhesion and the antibacterial properties were investigated after 3 h and 24 h of incubation with Streptococcus mutans, Streptococcus epidermidis, and Escherichia coli bacterial strains. The proposed anodization treatment created a chemically and morphologically modified, adherent titanium oxide layer, characterized by a microporous morphology enriched by calcium, silicon, phosphorous, and silver. The preliminary biological characterization showed optimal SAOS-2 cell adhesion and proliferation as well as a strong antibacterial effect. Based on the results of this study, we believe that this novel biomimetic and antibacterial treatment hold promise for enhancing osteointegration while conferring strong antibacterial properties to titanium.

Bone tissue, cellular, and molecular responses to titanium implants treated by anodic spark deposition

A myriad of titanium (Ti) surface modifications has been proposed to hasten the osseointegration. In this context, the aim of this study was to perform histomorphometric, cellular, and molecular analyses of the bone tissue grown in close contact with Ti implants treated by anodic spark deposition (ASD-AK). Acid-etched (AE) Ti implants either untreated or submitted to ASD-AK were placed into dog mandibles and retrieved at 3 and 8 weeks. It was noticed that both implants, AE and ASD-AK, were osseointegrated at 3 and 8 weeks. Histomorphometric analysis showed differences between treatments only for bone-to-implant contact, being higher on AE implants. Although not backed by histomorphometric results, gene expression of key bone markers was higher for bone grown in close contact with ASD-AK and for cells harvested from these fragments and cultured until subconfluence. Cell proliferation at days 7 and 10 and alkaline phosphatase activity at day 10 was higher on AE surfaces. No statistical significant difference was noticed for extracellular matrix mineralization at 17 days. Our results have shown that the Ti fixtures treated by ASD-AK allowed in vivo osseointegration and induced higher expression of key markers of osteoblast phenotype, suggesting that this surface treatment could be considered to produce implants for clinical applications.

Innovative antibacterial coating by anodic spark deposition

Silver containing coating can represent a solution to the recurring problem of biofilm formation on implant surfaces. In this study, the development of a titanium oxide coating containing silver particles is reported. The coating was obtained on medical grade Ti-6Al-4V alloy by anodic spark deposition in an aqueous electrolyte. Surface characterization revealed a high specific surface area with a succession of flat plateaus and depressions. Silver was present all over the coating surface as small particles of sizes below 200nm. When immersed in a liquid medium, the coating released silver ions at a constant rate over more than 15days. The coating was able to show a complete killing of gentamicin-resistant Staphylococcus epidermidis within the first 12h after inoculation.

Titanium oxide layers on aluminium substrates produced by the anodic spark deposition process

Titanium oxide layers were prepared on pure aluminium substrates by the anodic spark deposition method. The formed crystalline titania (TiO 2) phases rutile and anatase and the sodium titanium oxide (Na 0.23TiO 2) were identified. The corresponding crystallite size values were obtained from X-ray diffraction data by means of the Rietveld method. The crystallite size of each of these phases continuously increases with rising current density. Furthermore, the two-dimensional distribution of the titania phases on the sample surface was determined by Raman spectroscopy. It was found that the rutile/anatase ratio is inhomogeneous distributed on an observed area of 400 × 400 μm 2.

Design of Scanning Micro-Arc Oxidation Forming Ceramic Coatings on 2024 Aluminium Alloy

Micro-arc oxidation (MAO), also called plasma electrolytic oxidation (PEO), anodic spark deposition (ASD), or micro-arc discharge oxidizing (MDO), is an effective surface treatment technique which come from anodic oxidation technology. Via increasing the anodic voltage breaking through faraday area to a high stage accompanied by micro-arc discharge phenomenon, It indicated the ceramic coatings thickness increase along with the scanning times increase, while the thickness increment reduces. The phase composition, morphology and element distribution was studied by X-ray diffraction, scanning electron microscopy and line scanning. The morphology of the ceramic coatings shows it divided into compact layer and loose layer. And it composes of α-Al2O3 and γ-Al2O3.

Photoluminescent properties of barrier anodic oxide films on aluminum

We have investigated the photoluminescence (PL) spectra of barrier anodic oxide films on aluminum, formed in citric acid and in boric acid+borax. Strong PL bands are present in spectra of both electrolytes, featuring two distinct peaks in the 300nm to 600nm range. The first one is centered at about 460nm, while the other peak shifts with the excitation wavelength. The PL intensity increases upon annealing, reaching the maximum value at about 500°C. Experimental results indicate that the PL originates from optical transitions in two kinds of centers which are related to oxygen vacancies, F+ and F. In addition, the PL of oxide coatings formed under anodic spark deposition was performed and a third peak at around 327nm was observed.

Alternating current anodizing of titanium in halogen acids combined with Anodic Spark Deposition: Morphological and structural variations

The identification of anodic processes able to generate high surface area TiO 2 layers is a key requirement, whenever applications focused on its photoactivity or the integration between titanium implants and human body are considered. To achieve this goal, this research proposes an innovative two-step anodizing procedure. The first step consists of supplying alternating current to titanium in halogen acid electrolyte which quickly modifies its morphology. HCl and HBr were found to roughen effectively the metal surface, thus increasing its surface area. The successive step, an Anodic Spark Deposition treatment, generates a thick, semicrystalline oxide, containing both anatase and rutile crystals.

In vitro cellular response and in vivo primary osteointegration of electrochemically modified titanium

Anodic spark deposition (ASD) is an attractive technique for improving the implant-bone interface that can be applied to titanium and titanium alloys. This technique produces a surface with microporous morphology and an oxide layer enriched with calcium and phosphorus. The aim of the present study was to investigate the biological response in vitro using primary human osteoblasts as a cellular model and the osteogenic primary response in vivo within a short experimental time frame (2 and 4 weeks) in an animal model (rabbit). Responses were assessed by comparing the new electrochemical biomimetic treatments to an acid-etching treatment as control. The in vitro biological response was characterized by cell morphology, adhesion, proliferation activity and cell metabolic activity. A complete assessment of osteogenic activity in vivo was achieved by estimating static and dynamic histomorphometric parameters at several time points within the considered time frame. The in vitro study showed enhanced osteoblast adhesion and higher metabolic activity for the ASD-treated surfaces during the first days after seeding compared to the control titanium. For the ASD surfaces, the histomorphometry indicated a higher mineral apposition rate within 2 weeks and a more extended bone activation within the first week after surgery, leading to more extensive bone-implant contact after 2 weeks. In conclusion, the ASD surface treatments enhanced the biological response in vitro, promoting an early osteoblast adhesion, and the osteointegrative properties in vivo, accelerating the primary osteogenic response.

Electrochemical surface modification of titanium for implant abutments can affect oral bacteria contamination.

This research concerns the characterization of an electrochemical surface treatment applied to titanium, focused especially on the treatment of the transmucosal area of dental implants and abutments. The treatment is applied to improve soft tissue adhesion, to control and limit bacteria adhesion and proliferation, and to improve the aesthetic performance through a proper colorization of the metal surface. The electrochemical treatment considered, obtained on titanium by Anodic Spark Deposition technique (ASD), was performed in a calcium phosphate enriched solution. The bacteria behaviour was assessed by in vitro and in vivo tests. The investigated ASD treatment showed some antibacterial effect. No negative cytocompatibility effects were found on MG63 - human osteosarcoma cell lines and L929 - murine fibroblasts. The ASD modified treatment was found capable of modifying the titanium oxide layer providing a prevalent anatase crystalline structure and a microporous morphology, which can play an important role in the tissue integration process. The treatment was found capable of enriching the surface with calcium, providing improved biocompatibility and a light gray colorization. This last point is important for the aesthetic improvement of dental implant systems in the transgingival area.

Attachment, proliferation and osteogenic response of osteoblast‐like cells cultured on titanium treated by a novel multiphase anodic spark deposition process

A new bioactive titanium surface treatment, labeled Ti-ASD, was developed using the electrochemical anodic spark deposition (ASD) technique and results in a thickened titanium oxide layer with higher levels of calcium and phosphorus typical of newly deposited mineral phase. This study was aimed at extending the knowledge on Ti-ASD treatment, by means of evaluation of the attachment, morphology, proliferation, metabolic activity, differentiation, and mineralization of osteoblast-like cells (SaOS-2) after growth on Ti-ASD treated titanium compared with nontreated titanium (Ti) and with chemically etched titanium (Ti-ETC). This novel type of titanium coating supported cell attachment, cell proliferation, and mineralization, revealing no cytotoxicity effects. The expression of differentiation markers on Ti-ASD treated titanium shows that genes related to the proliferation phase (Collagen type I, Coll I; Cbfa-1) were early expressed, whereas genes related to the mineralization phase (alkaline phosphatase, osteopontin, bone sialo protein) increased in a time-related way. Mineralization occurred on all analyzed surfaces, but on Ti-ASD the number of bone-like nodules and the amount of mineralized area was higher. In conclusion, Ti-ASD resulted to be a good surface for osteoblast attachment and proliferation, also promoting the maintenance of cell differentiation and matrix mineralization, a fundamental requirement for sustain the osseointegration and the clinical success of dental implants.

Novel Silicon Based Anodic Spark Deposition Treatment for Dental Implant

Surface treated titanium implants are increasingly being used in dental and orthopaedic applications. This study examined the biological response of primary human alveolar osteoblast (aHOB) cells to a novel silicon based anodic spark deposition treated titanium surfaces. Three different titanium surfaces were investigated: anodic spark deposition (ASD) with silicon based (ASDSi), BioSpark™ (BS), and chemically etched (BioRough™, BR). Commercially pure titanium (cpTi) was the non-treated control surface. Physiological and biological evaluations were conducted on all test and control surfaces. Surface scanning (SEM, EDS, and AFM) confirmed a nano-topography, which was textured for all surfaces; and similar surface chemical composition (Ca and P), of significant was the Si peak on the ASDSi surface. Cell morphological study (SEM) showed good adhere and spreading over the surface, with metabolically active cells having extended filopodia. Biological response was observed with cell proliferation on all test surfaces for the period studied. Proliferation rate was seen to increase with time. This initial favourable cell response will be of benefit in the long term osseointegration of the implant surfaces.

Bone response to a Ca- and P-enriched titanium surface obtained by anodization

This study evaluated bone response to a Ca- and P- enriched titanium (Ti) surface treated by a multiphase anodic spark deposition coating (BSP-AK). Two mongrel dogs received bilateral implantation of 3 Ti cylinders (4.1 x 12 mm) in the humerus, being either BSP-AK treated or untreated (machined - control). At 8 weeks postimplantation, bone fragments containing the implants were harvested and processed for histologic and histomorphometric analyses. Bone formation was observed in cortical area and towards the medullary canal associated to approximately 1/3 of implant extension. In most cases, in the medullary area, collagen fiber bundles were detected adjacent and oriented parallel to Ti surfaces. Such connective tissue formation exhibited focal areas of mineralized matrix lined by active osteoblasts. The mean percentages of bone-to-implant contact were 2.3 (0.0-7.2 range) for BSP-AK and 0.4 (0.0-1.3 range) for control. Although the Mann-Whitney test did not detect statistically significant differences between groups, these results indicate a trend of BSP-AK treated surfaces to support contact osteogenesis in an experimental model that produces low bone-to-implant contact values.

The effect of surface treatments on the fretting behavior of Ti‐6Al‐4V alloy

Stem modularity in total hip replacement introduces an additional taper joint between Ti-6Al-4V stem components with the potential for fretting corrosion processes. One possible way to reduce the susceptibility of the Ti-6Al-4V/Ti-6Al-4V interface to fretting is the surface modification of the Ti-6Al-4V alloy. Among the tested, industrially available surface treatments, a combination of two deep anodic spark deposition treatments followed by barrel polishing resulted in a four times lower material release with respect to untreated, machined fretting pad surfaces. The fretting release has been quantified by means of radiotracers introduced in the alloy surface by proton irradiation. In a simple sphere on flat geometry, the semispherical fretting pads were pressed against flat, dog-bone shaped Ti-6Al-4V fatigue samples cyclically loaded at 4 Hz. In this way a cyclic displacement amplitude along the surfaces of 20 mum has been achieved. A further simplification consisted in the use of deionized water as lubricant. A comparison of the radiotracer results with an electrochemical material characterization after selected treatments by potentiostatic tests of modular stems in 0.9% NaCl at 40 degrees C for 10 days confirmed the benefit of deep anodic spark deposition and subsequent barrel polishing for improving the fretting behavior of Ti-6Al-4V.

A novel multiphase anodic spark deposition coating for the improvement of orthopedic implant osseointegration: An experimental study in cortical bone of sheep

The effect of a new three-step anodic spark deposition process, labeled TiSpark, including two consecutive treatments performed first in a P solution and second in Ca solution, followed by an additional alkali etching step, was investigated for the improvement of osseointegration of commercial grade 2 titanium, machined (Ti) or Al(2)O(3) sandblasted (Ti-SA), cylindrical implants (12 mm in length and 4 mm in diameter) in cortical bone of 12 adult sheep. Histomorphometric and microhardness measurements were carried out at each experimental time (4, 8, and 12 weeks) to quantify the bone-to-implant contact around the implants as well as the newly bone hardness and bone maturation index. TiSpark treated surfaces were covered by a thick layer of crystalline anatase TiO(2) and by a further Ca/P layer. Bone tissue extends and grows on the surface of the TiSpark treated implants without any fibrous tissue, enhancing the short-term osseointegration properties of implant. Bone mineralization rate was also influenced by the chemical composition of implants and sandblasted materials presented the lowest bone maturation rate at the interface. Data suggests that the TiSpark treatment produces a modification of the Ti surface, which presents good bioactivity and may be suitable for achieving a stable implant osseointegration.

Preparation and characterization of selenium incorporated anodic conversion coatings on titanium surfaces for biomedical applications

An anodic spark deposition process was used for preparation of inorganic, glass-ceramic like conversion coatings. The microstructure of the layers was characterized by surface and solid state techniques such as scanning electron microscopy, electron probe microanalysis and Raman spectroscopy. The porous coatings, typically up to 8 mum thick, consist mainly of titanium oxides and amounts of incorporated electrolyte constituents like Se, Ca or P. Beside nano crystalline anatase phases, a mostly amorphous structure is proposed in which network-forming [PO(4)] tetrahedras and [TiO(6)] octahedras in various degrees of condensation are connected. A drastic modification of the film structure was observed when selenium was incorporated into the glassy oxide structure of the coating. In these cases no nano crystalline phases of titanium oxides or other chemical compounds were detected. First cell culture investigations show a significant improvement of the biological properties. Cell proliferation and TGF-beta-expression of these coatings in comparison with commercial pure titanium (CPT) with native titanium oxide films were examined.

Preparation and characterization of doped metal-supported TiO 2-layers

Defined doping of metal-supported TiO 2-layers is possible by using cerium or gadolinium complex-precursors in anodic spark deposition processes. Thereby CeO 2 und Gd 2Ti 2O 7 species are formed in TiO 2-layers and the concentration of anatase increases. Studies using XRD, REM, TGA, DTA und HPLC have been carried out and characteristics of the surface were defined. The doping of TiO 2 using cerium and gadolinium results in a decreasing BET surface area. The band-gap determination of cerium doped samples offers a blue-shift. These results are reflected in studies of photocatalytic activity using reaction of methanol conversion. Gadolinium doped titanium dioxide showed better photocatalytic activity than cerium doped sample possibly because of the stability of Gd 3+-ions.