Syposium D Poster Session

Thursday, May 2, 2013 5:00 PM in Room Grand Hall

DP1 Albumin Adsorption on Zirconium Oxide Thin Films: the Influence of Atomic Ordering
Phaedra Silva-Bermudez (Instituto de Investigaciones en Materiales, Universidad Nacional Autónoma de Mexico, México, Mexico); Sandra Rodil (Instituto de Investigaciones en Materiales, Universidad Nacional Autónoma de Mexico, México)

Whenever a foreign material comes in contact with a biological media a complex cascade of events is triggered. After the adsorption of water molecules and hydrated ions, the adsorption of proteins from the biological media onto the material surface occurs. This leads to the formation of an adsorbed protein layer that directs the next coming cell – material interactions. Consequently, the protein adsorption studies constitute an excellent model to study the interaction between biological media and foreign materials and to gain a deeper understanding of the influence of the material physicochemical properties in this interaction.

In the last years, the influence of the physicochemical properties of foreign materials on the biological response has been widely studied and some surface properties such as the hydrophobicity and roughness are well known to affect the materials-biological media interaction. However, the influence of the atomic ordering has been less explored. In the present study, zirconium oxide, a widely known biocompatible material was chosen as the model material to study the influence of surface atomic ordering on protein adsorption; Fibrinogen (Fbg) was chosen as the model protein. Quasi-amorphous (q-a) and polycrystalline (p-c) zirconium oxide thin films were deposited on Si(100) substrates by Reactive Magnetron Sputtering. The atomic ordering, wettability, surface energy, roughness, optical properties and chemical composition of the films were characterized. The films were immersed in BSA solution and the protein adsorption was studied in-situ using dynamic and spectroscopic ellipsometry.

The results showed that the film roughness, as well as the water contact angle, increased with the atomic ordering of the film. A slightly higher Fbg adsorption rate was observed on the p-c ZrO2 film compared to the adsorption rate observed for the quasi-amorphous film. The differences observed in the Fbg adsorption on the two films might be related to the changes in the films roughness/wettability induced by the changes in the surface atomic ordering.

Acknowledgments to the financial funding and the postdoctoral fellowship for P.S-B from the CONACyT project # 152995.
DP2 Hydroxyapatite Growth Behavior and Osteocompatible Performance of Biomedical Polymer Coated with Titanium Dioxide Interlayer
Meng-Hui Chi (Feng Chia University, Taiwan, Republic of China); Hsi-Kai Tsou (Feng Chia University, Taiwan; Taichung Veterans General Hospital, Taiwan, Republic of China); Chi-Jen Chung (Central Taiwan University of Science and Technology, Taiwan, Republic of China); Ju-Liang He (Feng Chia University, Taiwan, Republic of China)

A widely utilized spinal implant materials, polyetheretherketone (PEEK), with its bio-inert and hydrophobic surface was suggested to proceed surface modifications for seeking better biocompatible performance. On the other hand, hydroxyapatite (HAp) exhibits excellent osteoconductive property, has been also regarded as a promising candidate for biomedical applications. The present study employed an arc ion plating (AIP) technique to respectively deposit rutile-rich titanium dioxide (R-TiO2) and anatase-rich titanium dioxide (A-TiO2) interlayers onto PEEK substrates, which were then immersed in simulated body fluid (SBF) for studying HAp layer growth. The microstructure observation and osteocompatible tests are carried out to evaluate the effects of HAp growth and osteoblast adhesion ability on adoption of TiO2 interlayer.

Experimental results showed that HAp growth can be effectively enhanced by adoption of TiO2 interlayer in SBF environment, with the crystallinity and film thickness of grown HAp layer proportional to immersion time. It was also worth to note that the R-TiO2/PEEK specimen exhibit superior ability to induce HAp formation, due most likely to negatively charged –OH groups on R-TiO2 coating surface at early stage. Furthermore, the osteocompatibility of bare PEEK substrate and interlayered specimen in terms of cell adhesion significantly correlated positively with the extent of HAp layer formation.

Keywords: polyetheretherketone (PEEK); hydroxyapatite (HAp); titanium dioxide (TiO2); osteocompatibility.
DP3 Deposition, Characterization and In Vivo Performance of Parylene Coating on General-purposed Silicone for Biocompatible Surface Modification
Chia-Man Chou (Taichung Veterans General Hospital; National Yang-Ming University); Chiao-Ju Shiao (Feng-Chia University, Taiwan, Republic of China); Chi-Jen Chung (Central Taiwan University of Science and Technology, Taiwan, Republic of China); Ju-Liang He (Feng Chia University, Taiwan, Republic of China)
In this study, a thorough investigation of parylene coatings was performed, including their microstructures, mechanical properties, surface properties and biocompatibility tests. The structure of parylene coatings identified by X-ray diffractometer (XRD) was disclosed its crystallinicity, which was consistent with the cross-sectional morphology shown in field emission scanning electron microscope (FESEM) images. In regard to the mechanical properties, parylene coatings exhibited a very low film hardness value but good film adhesion, as evaluated by a pencil hardness graded at 6B and the cross-cut test of the film adhesion graded at 5B, respectively. The water contact angle of parylene coatings in our study was measured at 86.1o. The relative hydrophobicity contributed to their effective barrier properties, which was related to the residual amount of aromatic rings shown in infrared spectrometry (IR). The surface chemistry of parylene films analyzed by X-ray photoelectron spectroscopy (XPS) showed a large O1s peak and C-O bonding at 286.1 eV because the thin parylene films react with atmospheric oxygen in addition to C-C binding at 285.1 eV. A cell culture on the parylene deposited specimen exhibited a higher cell count than the reference control (Medical grade silicone sheet) group. Platelet adhesion on parylene-coated silicone presented blood compatibility equivalent to or even better than that on medical grade silicone. In the animal study, parylene coatings exhibit similar subcutaneous inflammatory change in comparison with the reference control group. The results of both in vitro and in vivo testes demonstrated relatively good biocompatibility of parylene coatings.Keywords: parylene; in vitro; in vivo; biocompatibility
DP4 The Biological Characteristics of MG-63 Human Osteosarcoma Cell Line and Human Gingival Fibroblast Cells on Tantalum Doped Carbon Films
Ming-Tzu Tsai (Hungkuang University, Taiwan, Republic of China); Yin-Yu Chang (National Formosa University, Taiwan, Republic of China); Ya-Chi Chen (MingDao University, Taiwan, Republic of China); Jui-Ting Hsu, Heng-Li Huang (China Medical University, Taiwan, Republic of China)
Biomaterials are widely used in repair, replacement, or augmentation of diseased or damaged parts of the musculoskeletal system such as bones, joints and teeth. Metal-doped carbon films are gaining interest as an attractive surface modification for medical device materials. Because of their amorphous nature, amorphous carbon films are capable of embedding metallic elements, which can improve their functionality. Tantalum is considered a biocompatible metal with high corrosion resistance and biocompatability. In this study, biocompatible Tantalum (Ta)-doped carbon films with different Ta contents were synthesized by using a twin-gun magnetron sputtering system. The Ta contents in the deposited coatings were controlled by the magnetron power ratio of pure Ta and graphite cathodes. The nanocrystalline Ta was embedded in the amorphous carbon matrix as a nanocomposite film. Characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy (RS), field emission scanning electron microscopy (FESEM), and transmission electron microscopy (TEM), the crystal structure, bonding state and surface morphology of the deposited Ta doped carbon films were studied. The biocompatibility of Ta doped carbon films were examined in vitro by measuring the mitochondrial dehydrogenase activity (MTT test) of MG-63 Human Osteosarcoma cell lines and human gingival fibroblast (HGF) cells. The adhesive morphology of cells on films was also observed by using SEM. Additionally, the three dimensional (3D) biological structure of MG-63 cell was evaluated by using a confocal microscopy. The results suggested that the Ta doped carbon films can exhibit compatible soft-tissue and hard-tissue biological performances. This indicates that Ta doped carbon films are potential candidates for clinical applications of osseointegration of orthopedic implants.
DP5 Cytocompatibility and Antibacterial Properties of Zirconia Coatings with Different Silver Contents on Titanium
Heng-Li Huang (China Medical University, Taiwan, Republic of China); Yin-Yu Chang (National Formosa University, Taiwan, Republic of China); Ya-Chi Chen (MingDao University, Taiwan, Republic of China); Chih-Ho Lai, MichaelYC Chen (China Medical University, Taiwan, Republic of China)
Zirconia and their coatings have been proved to increase their applications in the biomedical fields such as orthopedic devices and dental implants by improving their osseointegration and wear resistance. In this study, doped ZrO2 coatings containing different proportions of Ag were deposited on bio-grade pure Ti implant materials. A twin-gun magnetron sputtering system was used for the deposition of the ZrO2-Ag coating. The Ag contents in the deposited coatings were controlled by the magnetron power and bias voltage. The films were then annealed using rapid thermal annealing (RTA) at 450 °C for 2 min to induce the nucleation and growth of Ag particles on the film surface. The crystalline structure and bonding states of the coatings were analyzed by XRD and XPS. The antibacterial behavior will vary, depending on the amount and size of the Ag particles on the coated Ti sample. In this study, S. aureus and Actinobacillus actinomycetemcomitans (A. actinomycetemcomitans) are Gram-positive and Gram-negative bacteria, respectively, that exhibit physiological commensalism on the human skin, nares, and mucosal and oral areas. Both bacteria were chosen as the model for in vitro anti-bacterial analyses by a fluorescence staining method employing Syto9 and bacterial viability agar tests. The cytocompatibility, mRNA expression, and adhesive morphology of human gingival fibroblast cells (HGFs) on the coatings were also determined by using the MTT assay, quantitative real-time polymerase chain reaction with reverse transcription (QRT-PCR), and SEM. It showed that the nanostructure of Ag on the ZrO2 coatings was correlated with the antibacterial performance and HGF cellular biocompatibility.
DP7 Adhesion and Corrosion Performance of Amorphous Titanium Oxide Films on Stainless Steel
Victor Garcia-Perez (Facultad de Odontología, Universidad Nacional Autónoma de México, Mexico); Phaedra Silva-Bermudez (Instituto de Investigaciones en Materiales, Universidad Nacional Autónoma de Mexico, México); Argelia Almaguer-Flores (Facultad de Odontología, Universidad Nacional Autónoma de México, Mexico); Johans Restrepo (Universidad Nacional Autónoma de México - Instituto de Investigaciones en Materiales, Mexico); Sandra Rodil (Instituto de Investigaciones en Materiales, Universidad Nacional Autónoma de Mexico, México)
Biomaterials are essential in the development of novel biomedical implants; they have to meet two main characteristics in order to have a potential application: a) To be able to stand the functional demands of the implant; which is normally related to the bulk properties of the material and b) To present a compatible interaction with the biological media; which is mainly driven by the surface properties of the material. It is difficult to find a single material that meets both criteria; functionality and biocompatibility. In this sense, the surface modification of a bulk material, which already meets the functional demands, through the deposition of biocompatible coatings to direct the biological interaction is a promising way to develop successful biomaterials. Thus, in the present work biocompatible TiO2 thin films were deposited by reactive radio frequency (RF) magnetron sputtering on stainless steel (AISI316L) substrates. The main objective was to improve the coating-substrate adhesion, which is critical for further evaluations and determine the film-substrate resistance to biological environments. Two deposition variables were changed in order to improve the adhesion of the TiO2 films to AISI316L substrates: a) The deposition of a Ti buffer layer previous to deposition of the TiO2 film; no Ti layer, a 6nm Ti layer and a 10 nm Ti layer, and b) The substrate temperature during the buffer layer deposition; no substrate heating, the substrate heated at 100 °C and the substrate heated at 250°C. The TiO2 films were always deposited under the same conditions: from a pure metallic Ti target (99.99%), no substrate heating, using 200 W of RF power and 1800 s of deposition time and under an atmosphere of Ar/O2 (8:2). The adhesion of the coatings on the AISI 316L was tested by the scratch method using a stainless steel ball with a load speed of 50 N/min, a scratching speed of 10 mm/min and allowing a final load of 40 N after 8 mm. The analysis of the scratch print showed that the first adhesion failure was produced at a shorter scratch distance in the coatings deposited with no Ti buffer layer; the best adhesion seemed to be presented by the coating deposited with the thickest Ti buffer layer (10 nm). The substrate temperature did not show a further important improvement in the adhesion. The optimized TiO2/10 nm Ti buffer layer/AISI316L system was then submerged into biological fluids for several days in order to verify the adhesion under simulated conditions. The electrochemical response was also evaluated and compared to the bare substrate. Acknowledgements: CONACYT 152995
DP8 Blood Compatibility and Adhesion of Collagen/Heparin Multilayers Coated on Two Titanium Surfaces by a Layer-by-layer Technique
Chau-Chang Chou, Hong-Jhih Zeng (National Taiwan Ocean University, Taiwan, Republic of China); Chi-Hsiao Yeh (Chang Gung Memorial Hospital, Keelung, Taiwan, Republic of China); Shang-Chi Liu (National Taiwan Ocean University, Taiwan, Republic of China)
This paper investigates the blood-compatibility and adhesion of collagen/heparin multilayers on a cp-Ti substrate by a layer-by-layer self-assembly technique. There were two surface polishing processes for the titanium samples: one is mechanical polishing and the other, electropolishing. These samples were pretreated by being immersed in an NaOH solution to obtain a negatively charged surface with hydroxyl groups and then, positively charged in a polyl-L-Lysine one. The repeated treatment of the samples by applying heparin and collagen alternatively determined the number and thickness of the multilayers. The surface topography, chemical composition, and hydrophile of the films were investigated by atomic force microscopy, scanning electron microscopy, Fourier transform infrared spectroscopy, and water contact angle measurement. The study of the multilayers' shear adhesion was conducted by a nano-scratch test as well as a cone-and-plate rheological one. The blood compatibility was evaluated by measuring haemolysis ratio and platelet-covered area in vitro. The uncoated titanium surface was used as the benchmark. The results indicate that the collagen/heparin multilayers on the titanium surface have superior anticoagulation performance than the uncoated titanium surface does. The increase of the multilayers’ thickness enhances the adhesion to Ti substrate. The influences of electropolishing process and NaOH pretreatment are also discussed and addressed.
DP11 Effect of Nitrogen Plasma Immersion Ion Implantation Treatment on Corrosion Resistance of Ni-free ZrCuFeAl Bulk Metallic Glass
Hsun-Miao Huang, Ying-Sui Sun, Her-Hsiung Huang (National Yang-Ming University, Taiwan)

This study was to investigate the corrosion resistance of Ni-free Zr62.5Cu22.5Fe5Al10 bulk metallic glass (BMG) alloy, before and after nitrogen plasma immersion ion implantation (N-PIII), for biomedical application. The corrosion resistance, in terms of potentiodynamic polarization curve and metal ions release measurements, was evaluated in artificial saliva and simulated blood plasma solutions. Commercial biomedical pure Ti was used as the reference group for comparison. Results showed that the N-PIII-treated BMG alloy had lower corrosion rate and higher corrosion potential than the untreated BMG and Ti. The N-PIII treatment significantly improved the pitting corrosion resistance and decreased the metal ions release of BMG alloy. In terms of corrosion resistance, the Ni-free Zr62.5Cu22.5Fe5Al10 BMG alloy has potential for biomedical applications; N-PIII treatment further improves the corrosion resistance of BMG alloy.

DP12 Tribocorrosion and Properties of TiAlN/TiB2 Coatings Deposited onto Ti6Al4V Alloy by DC/RF Magnetron Sputtering
Omar Jimenez, Jesus Reyes, Martin Flores, Eduardo Rodriguez (Universidad de Guadalajara, Mexico)

Titanium and its alloys are one of the most used materials in many industries such as aerospace, military and biomedical due in part to a combination of properties including low weight and good biocompatibility. One of the low points of this material is the poor wear resistance particularly in sliding conditions. Many PVD coatings are intended to improve the wear resistance by modifying the surface properties of a big variety of substrates while retaining or enhancing existing properties. In this work, ceramic TiAlN/TiB2 coatings were deposited by DC/RF magnetron sputtering under a selection of parameters. The mechanical properties were measured by nanoindentation techniques, while the structural properties were explored through XRD experiments. The thickness of these coatings and the after deposition roughness were measured by means of profilometry. Tribocorrosion behaviour was evaluated from open circuit potential (OCP) during reciprocating sliding in combined tests using SBF as the electrolyte at 37 °C. Results indicate that hardness values reached more than 20 GPa in all cases, while the thickness was in the range of 3-4 μm. The structural analysis revealed the presence of TiAlN and boron-containing phases. Finally, tribocorrosion results of coated samples showed a considerable change towards positive values in the Ecorr and slightly lower values were registered in the current density Icorr during sliding conditions at 1 and 2N.

DP13 The Tribocorrosion Behavior of CoCrMo Alloys Coated with TIALPtN in Simulated Body Fluid
Martin Flores (Universidad de Guadalajara, Mexico); Eduardo Andrade (Universidad Nacional Autónoma de México, Mexico); Omar Jimenez, Eduardo Rodriguez (Universidad de Guadalajara, Mexico)

The tribocorrosion phenomenon is present in biomedical alloys used in artificial implants to replace natural joints. This damage limit the service life of such implants, the hard coatings can improve the wear and corrosion resistance. The TiAlPtN coatings were deposited on CoCrMo alloys by magnetron sputtering. The structure of coatings was studied by means of XRD and the composition by RBS technique. The tribocorrosion behavior CoCrMo alloys alone and coated with TiAlPtN was studied in simulated body fluid. The tribocorrosion was performed using a ball on plate reciprocating tribometer, the test was conducted in a simulated body fluid at 37 °C of temperature. The loads used were 0.5 N and 1N, the oscillating frequencies was 1Hz. The corrosion and tribocorrosion were studied using open circuit potential (OCP), potentiodynamic polarization, cyclic polarization and potentiostatic polarization measurements. The potentiodynamic polarization was used to estimate the change in the corrosion rate due to wear and the potensiostatic polarization in the passive region to measure the change in the wear rate due to corrosion. The surface topography and worn surface were studied by means of profilometry. The Pt content in TiAlN films was about 0.5 at. %, the coatings improve the corrosion and tribocorrosion resistance of CoCrMo alloys.

DP14 101 Million Cycle Simulator Wear Characterization of Diamond lLke Carbon Coated CoCrMo Articulating Implants
Kerstin Thorwarth, Ulrich Müller, Renato Figi, Bernhard Weisse (Empa, Swiss Federal Laboratories for Materials Science and Technology, Switzerland); Götz Thorwarth (DePuy Synthes Companies, Switzerland); Roland Hauert (Empa, Swiss Federal Laboratories for Materials Science and Technology, Switzerland)

Diamond like carbon (DLC) coatings have been proven to be an excellent choice for wear reduction in many technical applications. However, for successful adaption to the MedTech field, layer performance, stability and adhesion in realistic physiological setups are very important and not consistently investigated. Simulator testing as well as corrosion tests are of great importance to verify the long term stability of such a DLC coated articulating implants in the human body. Commonly one million cycles of simulator testing correspond to 1 year of articulation in the human body. Diamond like carbon coatings were deposited on CoCrMo biomedical implant alloy using a plasma-activated chemical vapor deposition (PACVD) process. As an adhesion promoting interlayer tantalum films were deposited using magnetron sputtering.

It is shown that metal-on-metal (MoM) pairs perform well up to 5 million loading cycles, after which they start to generate wear volumes in excess of 20 times those of DLC-coated implants. This is attributed to the slight roughening observed on unprotected metal surfaces as usually also observed in-vivo. The DLC on DLC inlay pairs show comparable low volume losses throughout the full testing cycle (up to 101 million cycles over a period of three years and two month). To our knowledge this is the first time a simulator test of a DLC-coated articulating implant running for more than 100 million (corresponding to over 100 years of articulation in-vivo) cycles is presented.

Within this time these implants were characterized by high wear resistance, low friction coefficients, high corrosion resistance and low defect growth. These results were obtained by means of optical microscopy, SEM/EDX, FIB cross section and profilometry. The coatings were further analyzed using XRD and XPS.

DP15 Preparation of a Composite Bioceramic HA/Ag Coating and Effect on Insertion Torques of the Coated Ti6Al4V Screws
Tse Cheng, Xueyuan Nie, Yin Chen (University of Windsor, Canada)

A bioceramic TiO2 coating with Hydroxyapatite (HA) and Silver (Ag) deposited on Ti6Al4V alloy screws was produced by using a combination of electrophoretic deposition coupled plasma electrolytic oxidation (PEO) and anodizing processes. The coatings revealed a relatively rough and porous surface which may potentially promote a higher anchorage as well as more favorable osteointegration properties to the bones. In this paper, an insertion torque (IT) analysis on low (10 pcf, pounds per cubic feet), middle (15 pcf), and high (20 pcf) density sawbones and real pig bones were carried out and compared with the uncoated screws. Higher insertion torques and final seating torques were obtained in the coated screws which may result less micromovement after implantation and thus lower the risk of implant failure. Surface morphological evaluation before and after insertion and removal by SEM and EDS were further performed. The coatings remained adhered to the substrates. No loss of HA and Ag particles from the coating was observed. These results qualitatively implied a good bonding strength between oxide coating and Ti alloy substrate.

DP16 Scratch Resistance of Coated Orthodontic Archwires
Emanuel Santos Jr., Dayanne da Silva, Antonio Ruellas, Sérgio Camargo Jr., Claudia Mattos (Federal University of Rio de Janeiro, Brazil)

Metallic archwires have been successfully employed in orthodontics for the last decades. Such commercial archwires are made of either stainless steel (CrNi) or NiTi alloys. Both epoxy resin and polytetrafluoroethylyene (Teflon®) thick coatings are commonly used to cover orthodontic archwires exclusively for esthetic purposes. However, some papers have reported the presence of coatings failures in clinical use. Even so, a few works have been published concerning their coating-substrate adhesion, as well as their mechanical and tribological properties. In the present study, five commercialized coated esthetic orthodontic archwires from different manufacturers were studied, as follows: Orthometric (China), Ortho Organizers (USA), TP Orthodontics (USA), Trianeiro (Brazil), and Tecnidente (Brazil). Coatings hardness and elastic moduli were assessed by instrumented indentation tests. For a 2.0 mN load, they presented hardness in the 170 – 250 MPa range, while their elastic moduli varied from 5.5 to 7.7 GPa. Scratch resistance of coatings and their substrates were evaluated by scratch tests. A total of 5 tests were performed on each sample by the ramping load method with loads from 0 to 500 mN, 500 µm scratch length, 50 µm/s scratch velocity, and a diamond Berkovich-geometry tip displaced in the knife-face position. All tests were carried out in air at room temperature. For the tested coatings, the maximum penetration depths of about 12.0 µm were achieved; thereby, the substrates were not reached once the coatings are as thick as 20.0 µm. Despite having elastic recoveries of about 70 - 90%, different failure features could be observed along the scratches by scanning electron microscopy. In some cases, delamination, crack propagation and debris generation were observed. In fact, such failures must be avoided for clinical use. Coating detachment due to poor substrate-film adhesion was not evident. The coatings coefficient of friction (COF) increased linearly up to 0.3 (~ 50 mN load), and then, leveled off in the 0.34 – 0.40 range for higher loads. The COF of the CrNi and NiTi substrates had a different behavior. They increased during all the tests while the loads were ramped. In the beginning, the COF of the substrates were lower than those obtained for coatings for loads up to 250 mN. For the higher loads, the COF increased until 0.45. The coated archwires most resistant to scratch were those that presented little plastic (permanent) deformation associated with minor damaging features.

DP17 AC Impedance Behavior of HA/TiN Coated Ti-25Ta-xZr Alloy by RF Sputtering and EB-PVD for Dental Implant
Hyun-Ju Kim, Yong-Hoon Jeong, Yeong-Mu Ko (Chosun University, Korea); Sang-Won Eun (Polytechnic V Colleges, Korea); Han-Cheol Choe (Chosun University, Korea)
Cp-Ti and Ti-6Al-4V alloys metallic materials are widely used for dental implant and orthodontic application because of their good properties, however, Ti–6Al–4V alloy can potentially cause some health problems because of the release of toxic metal ions. For improving this problem, Ti alloys with non-toxic elements such as Nb, Ta, Zr, and Hf have been developed, and we have focused on Ti-Ta-Zr alloy system with controlling of Ta and Zr elements. When added to Ti, Ta acts as a β phase stabilizer and lowers the elastic modulus, and Zr, which has similar chemical properties to titanium, provides solid solution strengthening because of its dissimilar atomic radius. The addition of Zr also results in a high level of blood compatibility when used in cardiovascular implants and leads to better corrosion resistance due to the formation of stable ZrO2. The titanium nitride (TiN) coatings are used widely in many dental and industry fields due to their high hardness, good wear resistance, good adhesion, excellent corrosion resistance, and low friction coefficient. Hydroxyapatite [HA; Ca10(PO4)6(OH)2] is a bioactive material that has been used as a bone replacement material in restorative dental and orthopedic implants, and HA can encourage initial bonding between body tissues and an implant surface. However, the bond strength between an HA and substrate can be decreased due to spalling of film in oral environment after long-term use. To overcome, the implementation of a barrier buffer layer on substrate is one way to avoid spalling of HA films, multi-layered coating with TiN and HA showed a fast and stable fusion between the coated implant and the bone. In this study, we investigated AC impedance behavior of HA/TiN coated Ti-25Ta-xZr alloy by RF sputtering and electron-beam physical vapor deposition (EB-PVD) for dental implant. Ti-25Ta-xZr alloys were melted by using a vacuum furnace. Ti-25Ta-xZr alloys were homogenized for 12hr at 1000℃. The microstructures of Ti-25Ta-xZr alloys were analyzed by OM, XRD, and SEM. The TiN coating were obtained by the radio frequency (RF) magnetron sputtering technique. And then, the HA coatings were coated on the samples by EB-PVD method. The surface characteristics were analyzed by field emission scanning electron microscopy (FE-SEM), energy dispersive X-ray spectroscopy (EDX) and X-ray diffractometer (XRD), respectively. Microstructure of Ti-35Ta-xZr alloys changed from α̎ to β phase and, a needle-like to an equiaxed structure with Zr content. The AC impedance test showed high value of polarization resistance on HA/TiN coated Ti-25Ta-xZr alloys than that of non coated surface. (NRF: R13-2008-010-00000-0; hcchoe@chosun.ac.kr)
DP18 Hydroxyapatite Precipitation on Nanotubular Film Formed Ti-25Nb-xHf Alloys for Biomedical Application
Sung-Hwan Kim, Yong-Hoon Jeong, Yeong-Mu Ko, Han-Cheol Choe (Chosun University, Korea)
CP-Ti and Ti–6Al–4V alloy have been studied for the applications of orthopedic and dental implants materials due to its excellent mechanical properties, corrosion resistance, and superior biocompatibility. However, the widely used Ti -6Al-4V is found to release toxic ions (Al and V) into the body, leading to undesirable log-term effects. Recent research on metallic biomaterials has focused on Ti alloys composed of non-toxic elements like Nb, Ta, Mo, Hf and Zr, in order to overcome the long-term health problem caused by the release of toxic metal ions. Moreover, Nb is found to reduce the modulus of elasticity when alloyed with Ti, Hf leads to better corrosion resistance due to the formation of a stable oxide surface layer. The anodization by electrochemical method can be shown highly ordered oxide nanotube layers in fluoride contained acid electrolytes at moderate voltage. Nanotube formation on the surface titanium oxide is conjectured to improve the bone cell adhesion and proliferation in clinical applications of implants. Additionally, hydroxyapatite (HA, Ca10(PO4)6(OH)2) has been used as a surface coating material on metallic surface in dentistry and orthopedics due to their bioactive characteristics, which enable their rapid fixation and stronger bonding between the host bone and the metal surface.Therefore, the objective of the present study was to the hydroxyapatite precipitation on nanotube formed Ti-25Nb-xHf alloys for biomedical application. The Ti-25Nb-xHf ternary alloys contained from 0 wt. % to 7 wt. % contents were manufactured by vacuum arc-melting furnace. The formation of nanotubular film was conducted by electrochemical method in mixed electrolytes with 1 M H3PO4 + 0.8 wt. % NaF at 30V for 2h. After that, electrochemical deposition for HA precipitation was carried out using cyclic voltammetry (CV) method with scanning potential between 0 V to -1.5 V at scan rate 100 mV/s on 80 °C in Ca(NO3)2 (2.5 - 10 mM) + NH4H2PO4 (1.5 – 3 mM) solution. The surface characteristics were investigated using field emission scanning electron microscopy (FE-SEM), x-ray diffractometer (XRD), energy dispersive X-ray spectroscopy (EDS), Fourier transform infrared spectroscopy (FTIR) and contact angle measurement. Microstructures of alloys were transformed from α′′ phase to β phase, which showed a needle-like to an equiaxed structure as Hf content increased. Increasing solution concentration, needle-like deposits transferred to the plate-like and micro plate like precipitates in the case of high SBF concentration. (NRF: R13-2008-010-00000-0; hcchoe@chosun.ac.kr).
DP19 HA/TiN Multilayer Coating on the Ti-30Nb-xTa Alloys by RF Sputtering for Biocompatibility
Eun-Sil Kim, Yong-Hoon Jeong, Yeong-Mu Ko, Han-Cheol Choe (Chosun University, Korea)
Titanium and its alloys are widely used in biomaterials due to their excellent mechanical properties, high corrosion resistance and good biocompatibility. Ti-6Al-4V alloy has been widely used as a high strength biomedical alloy. However, recent studies have shown the release of both vanadium and aluminum ions to the human body, might cause health problems, such as peripheral neuropathy and Alzhemier diseases. To remove this problem, we have focused on alloying with non-toxic contents such as Ta, Nb and Zr elements. Among these, the additions of Nb and Ta to Ti are usual based on their biological passivity and capacity of reducing the elastic modulus.At HA coating techniques, plasma spraying has shown to be a success in clinical applications since they exhibit enough bioactivity than uncoated ones, but, clinical failures sometimes does occur due to the weak mechanical strength due to the relatively thick coatings (50 - 200 µm). On the other hand, magnetron sputtering is one the most important growth techniques that is applicable to a large variety of materials, providing often the optimum with respect to deposition rate and film quality. Also, the titanium nitride (TiN) coatings are used widely in many dental and industry fields due to their high hardness, good wear resistance, good adhesion, excellent corrosion resistance and low friction coefficient. Especially, the bonding strength of HA/TiN multilayer coating on Ti was markedly improved when compared to that of the TiN and HA single layer coating on Ti. Therefore, this study was performed to fabricate an HA/TiN multilayer coating on the Ti substrate, in order to optimize the biocompatibility of the Ti-30Nb-xTa alloys.In this study, we investigated biocompatibility of HA/TiN multilayer on the Ti-30Nb-xTa alloys coated by RF sputtering. Ti-30Nb-xTa alloys with Ta contents of 0 and 7 wt. % were melted by using a vacuum arc-melting furnace, and homogenized for 12 h at 1000℃. The TiN and HA films were coated on the samples by RF sputtering. The surface of these alloy were analyzed by corrosion test and wettability test in order to observe ion release and hydrophilic property. The phase composition and microstructure were investigated by using field-emission scanning electron microscope (FE-SEM) and energy dispersive X-ray spectroscopy (EDS), X-ray diffractometer (XRD), and optical microscopy (OM). The microstructure of Ti-30Nb-xTa alloys changed α’’ phase to β phase, the grain size was increased with Ta content. HA coated Ti-30Nb-xTa alloys surface showed better wettability and higher corrosion resistance than that of non-coated surface. (NRF: R13-2008-010-00000-0; hcchoe@chosun.ac.kr).
DP20 Electrochemical Behaviors of an Interface Between Si/HA Coated Ti-Nb-Zr Alloy and HOB Cell
Yong-Hoon Jeong, Han-Cheol Choe (Chosun University, Korea)
Metallurgy materials have a long history in the medical fields but, metals are definitely artificial materials and have not much bioactive that causes to low attraction of metals as biomaterials. The surface modification techniques are developed according to have major purpose to improve hard tissue compatibility or accelerate bone formation. One of bioactive coating technique, HA (hydroxyapatite; Ca10(PO4)6(OH)2) coating is widely used for surface modification of metal implants due to the mechanical properties of the metal combined with the excellent bioactivity of the HA, moreover, the silicon substituted hydroxyapatite (Si/HA) coatings are greater than single HA coating for bone on-growth. Meanwhile, β rich Ti-35Nb-xZr alloy system shows significant low elastic modulus and has non-toxic elements, Ti-35Nb-10Zr alloy has appropriate properties of low elastic modulus that consisted with non toxic elements as a substrate for bioactive coating. To confirm a cell attachment on modified surface, electrochemical test between cell and metallic biomaterial is excellent to verify the biocompatibility and corrosion characteristics, especially, the electrochemical impedance spectroscopy (EIS) measurement is also good technique to know the characteristics between true surface and interface without any damages on surface behavior.In present study, the research focused on the electrochemical behaviors of an interface between Si/HA coated Ti-Nb-Zr alloy and HOB cell. The Ti-Nb-Zr alloy was manufactured with 35 wt. % of Nb and 10 wt. % of Zr by arc melting furnace to have a β phase. The Si/HA coatings were prepared by electron-beam physical vapor deposition (EB-PVD) method with variable Si contents between 0.5 and 1.2 wt. %. The surface characteristics were analyzed by field emission scanning electron microscopy (FE-SEM), energy dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD), respectively. To evaluate of cell attachment on Si/HA coated surface, the EIS test was performed after osteoblast like cells (HOB). Numerical parameters of EIS test were compared by a non-parametric method at a significance level of α = 0.05. As a result, The EIS measurement could be applied to verify the density of HOB cells on Si/HA coating surface, Si substitution had highly correlation with cell density on their surface to show higher value of corrosion resistance.
DP21 Hydroxyapatite Coating on Micro-pore formed Ti-35Ta-xNb Alloy by Electron Beam-Physical Vapor Deposition
Chae-Ik Jo, Yong-Hoon Jeong, Yeong-Mu Ko, Han-Cheol Choe (Chosun University, Korea); Sang-Won Eun (Polytechnic V Colleges, Korea)
Titanium is an attractive biomaterial for its excellent characteristics such as excellent biocompatibility, corrosion resistance and Ti-6Al-4V alloy is widely used for dental and orthopedic implant. But Ti-6Al-4V alloy concerns about the potential of cell cytotoxic and Alzheimer’s disease, because of vanadium and aluminum. Therefore, Ti alloy require to new alloying element such as Nb, Ta, Zr, Hf, Mo, and Sn, as one of β phase Ti alloy, Ti-35Ta-xNb alloys have shape memory property, low elastic modulus, non-allergic and non-toxicity which can be applied to biomaterial. The use of porous Ti and Ti-6Al-4V alloy implants allows a higher degree of bone in-growth and body fluid transport through three dimensional inter-connected arrays of pores, is improving the interactions with bone and the implant fixation. Additionally, anodic oxidation is reported to be one of interesting method for forming rough and porous oxide film and increasing thickness of the native oxide layer. Hydroxyapatite has been widely used as a bioactive coating material in medical and dental applications. Due to the favorable biocompatibility of HA and attractive mechanical properties of metallic structure, HA coated Ti and Ti alloys have become some of the most promising implant materials for dental applications. In this study, we investigated Hydroxyapatite Coating on Micro-pore formed Ti-35Ta-xNb Alloy by Electron Beam-Physical Vapor Deposition. These alloys were prepared from Ti with 35 wt% and Nb which contents of 0, 5, 10, and 15 wt% and were manufacture in arc-melting furnace, and then, homogeneous treatment was carried out at 1000°C for 12h in argon atmosphere. Anodization treatments on Ti-25Nb-xHf alloys were carried out in electrolyte containing typically 1M H3PO4 at 200V for this experiment. The HA coating was subsequently prepared by EB-PVD method on micro-pore formed Ti-35Ta-xNb alloys surface. The microstructures, morphology and phase transformation were measured by optical microscope (OM), field emission scanning electron microscope (FE-SEM), X-ray dispersive spectroscopy (EDX), X-ray diffractometer (XRD), roughness test, and wettability test. As results, the Ti-35Ta-xNb alloys transformed α’’ to β phase with addition of Nb contents. The XRD peaks showed calcium, phosphate, anatase and rutile phases on HA coating on anodized surface. The micro-pore size depended with Nb content, wettability was highly decreased with HA coating on their surface. (NRF: R13-2008-010-00000-0; hcchoe@chosun.ac.kr [mailto:hcchoe@chosun.ac.kr] )