bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of Solid Solution Treatment on the Microstructure and Mechanical Properties of IN738LC Superalloy
Authors: Kim Jeong Min , Park Joon Sik , Yun Ho Seob , Lee Seung Jin , An Seong Uk
Published: October 2011

Cast IN738LC alloy mainly consists of primary gamma matrix, gamma prime precipitates, and carbides. SEM-EDS analysis results suggested that most of the carbides are MC type ones that possess high Ti or Ta contents. MC carbides were partly dissolved into the matrix during the solid solution treatment, and the morphology and size of carbides were influenced by the solid solution treatment temperature. Characteristics of gamma prime precipitates were also significantly affected by the solid solution treatment conditions. Single or duplex size distributions of gamma prime precipitates were obtained depending on the solid solution treatment condition. Higher tensile strength was obtained in the case of finer precipitation size and in the case of single size distribution as compared with that of duplex size distribution.
Defect Characterization Using Random Telegraph Noise in GaN-Based Light-Emitting Diodes
Authors: Park Jung Jin , Kang Tae Wook , Woo Dae Young , Son Joong Kon , Shin Hyung Cheol
Published: October 2011

In order to investigate the influence of the traps which exist in the multi-quantum-well (MQW) of GaN-based light-emitting diodes (LEDs), we analyzed the output current fluctuation known as random telegraph noise (RTN) at reverse-biased region. We could find the two-level current fluctuations at two samples (S1, S2) and the low-level average time (τlow) is larger than the high-level average time (τhigh) at both samples, which means that the energy level of the trap is located below the mid-gap of used material. With increasing a reverse bias voltage, in case of S1, τhigh becomes higher and τlow becomes lower as the energy level of the trap becomes relatively higher in reference to quasi Fermi level, EFn. On the contrary, the τhigh becomes lower and the τlow becomes higher at S2 as the energy level of the trap becomes relatively lower in reference to quasi Fermi level, EFp.
Bulk Diffusion of Homovalent Non-Magnetic Atomic Probes of Titanium and Zirconium in Tungsten Single Crystals
Authors: Klotsman S.M. , Tatarinova G.N. , Timofeev Alexander N.
Published: October 2011

The bulk diffusion of homovalent non-magnetic atomic probes (APs) from the IVB group of the periodic table of elements (PTE) – Ti and Zr in tungsten single crystals was investigated by sec-tioning, using secondary ion mass spectrometry (SIMS). The Arrhenius dependences had the fol-lowing parameters: DWTi - (D0)WTi = (3.00.4 ) x 10-4 m2s-1, enthalpy QWTi = (576 ± 9) kJ/mole; DWZr - (D0)WZr = (2.3  0.6) x 10-4 m2s-1, QWZr = (561 9) kJ/mole. The measured parameters (D0,Q)WTi,Zr of diffusion of Ti and Zr atomic probes (APs) in W are in accord with the empirical correlation: the diffusion coefficients of the substitutional APs coincide with the self-diffusion coefficients in W at (Tm)W – its melting temperature. Enthalpies QWTi,Zr,Hf of the volume diffusion of homovalent non-magnetic APs of the IVB group of periodic table of elements (PTE) - Ti, Zr and Hf increase with the decrease of relaxation volumes of the complexes «vacancy-IVBAP» in W lattice. The energies (E)WvacIVBAP of elastic relaxation of the complexes «vacancy-IVBAP» in W lattice were estimated. Electron contributions EDN to the energies EWvacIVBAP of interaction of the point defects in complexes «vacancy-IVBAP» increase relative to value EWvacIIIBAP of interac-tion of the point defects in complexes «vacancy-IIIBAP» with the growth of d-electrons number in comparison with the complexes «vacancy-IIIBAP».
The Comparative Mössbauer Analysis of Superfine Structure of Hadfield Steel upon Different Kinds of Severe Deformation
Authors: Shabashov V.A. , Zamatovsky A.E. , Korshunov L.G. , Litvinov A.V.
Published: October 2011

Severe plastic deformation (friction, compression shear, filing or rolling) of Hadfield steel leads to the growth of the internal effective field on 57Fe cores, removal of the magnetic degeneracy in spectra, and the extension of the paraprocess up to room temperature. The observed change of the magnetic characteristics is explained by the deformation-induced redistribution of carbon and short-range ordering of carbon and manganese. Since the magnetic degeneracy is removed in the Hadfield steel upon deformation, it is possible to consider a mechanism of magnetic precipitation hardening, which is realized in local magnetically ordered regions of the structure containing Mn-C pairs.
Influence of Ca2+ and Mg2+ Supplementation on In Vitro Biological Properties of Hydroxyapatite/Collagen Nanocomposite Membrane
Authors: Bodhak Subhadip , Kikuchi Masanori , Oyane Ayako , Sogo Yu , Tsurushima Hideo , Ito Atsuo
Published: October 2011

Hydroxyapatite/collagen (HAp/Col) nanocomposites with bone-like self-organized nanostructure show excellent bioactivity in vivo. However, they show quite high absorbability for cationic ions and lower culture medium ionic concentrations which adversely affects bone cell proliferation and osteogenic differentiation in in vitro cell culture condition. To address this limitation, in this study we have supplemented Ca2+ and Mg2+ ions to the HAp/Col nanocomposite membrane sample prior to cell culture to improve it’s in vitro biological properties. The HAp/Col nanocomposite membrane samples were fabricated by the simultaneous titration method using Ca(OH)2, type-I atelocollagen and H3PO4 as starting precursor materials. Prior to in vitro cell culture experiments, the HAp/Col samples were pretreated with Ca2+ and/or Mg2+ ions by immersing in 10 ml of 20 mM CaCl2 solution, 20 mM MgCl2 solution, or a solution containing 20 mM CaCl2 and 20 mM MgCl2 for 7 days. In vitro bone cell-material interactions on the pretreated and untreated HAp/Col samples were studied by culturing MC3T3-E1 cells up to 7 days. Enhanced bone cell proliferation was found on all the pretreated HAp/col samples as confirmed by the CCK-8 assay. Interestingly, the HAp/Col samples pretreated with both Ca2+ and Mg2+ ions showed the maximum viable bone cell density.
Characterization and Monitoring of the Evolution of a Calcium Phosphate/Calcium Sulfate Self−Setting Bone Cement
Authors: Kasioptas Argyrios , Sandell Veronica , Lidén Eva , Börjesson Oskar , Nilsson Malin
Published: October 2011

The hydration of α−tricalcium phosphate (α−TCP) is known to lead to the formation of an interlinked calcium−deficient hydroxyapatite (CDHA) framework. This apatite resembles the composition and structure of physiologic bone mineral, making it a good candidate for bone reconstruction. The additional presence of a calcium sulfate phase, which has a faster resorption rate than apatite, gives a gradual creation of porosity in the cement. This may in turn enhance bone ingrowth. The aim of this study was to gain deeper understanding of the main characteristics and properties of a bi−phasic α−TCP/α−CSH cement, prepared with an X−ray contrast medium.Isothermal calorimetry has been used to follow the course of the hydration reaction over time as it involves traceable exothermic events with possible contributions from both the calcium phosphate and calcium sulfate components. This was done in an attempt to identify and differentiate the role of each reactive phase. Additionally, the total produced heat from the cement has been used to estimate the degree of conversion and this result has been verified by X−ray diffraction analysis.Furthermore, compressive strength of the α−TCP/α−CSH cement has been measured over time to investigate the possible connection to its thermal evolution signature. Also, the impact of the surrounding environment on the α−TCP and α−CSH conversion was investigated by comparing XRD results between samples that had been kept dry or wet.
Biomimetic Magnetic Nanoparticles for Hyperthermia Treatment
Authors: Múzquiz-Ramos E.M. , Cortés-Hernández Dora A. , Sánchez-Torres C.G. , Escobedo-Bocardo José C. , Zugasti A. , Ramírez-Gómez X.S.
Published: October 2011

The aim of this work was the synthesis of bioactive magnetic particles (BMP) which are expected to form a thin apatite layer on its surface that may bond to bone with the osseous carcinogen tissue. Magnetite and Mg0.6Ca0.4Fe2O4 nanoparticles were obtained by a reverse co-precipitation and sol-gel methods, respectively. Magnetite particles were coated with chitosan in order to obtain a stable ferrofluid. Then both ferrites were biomimetically treated using two different simulated body fluids (SBF and 1.5 SBF). An apatite layer was formed on both types of BMP after the biomimetic treatment. Both ferrites showed superparamagnetic behavior before and after the apatite formation. Their time-dependent temperature profiles were measured under the effect of an AC magnetic field (AMF). After less than 20 min of applying the AMF an appropriate temperature for hyperthermia treatment was obtained. No citotoxicity was observed after osteosarcoma cell culture testing of BMP. Furthermore, after applying an AMF to the cells in contact with the BMP, the cells viability decreased considerably.
The Storing Properties of Electric Energy in Bone
Authors: Hiratai Rumi , Nakamura Miho , Nagai Akiko , Yamashita Kimihiro
Published: October 2011

We have shown that hydroxyapatite (HA), which characteristics were similar to those of bone’s inorganic components, had polarization capability and was possible to accumulate electricity under high temperature and pressure. Then, we presumed that bones had polarization capability which enabled electrical storage and conducted the experiment to measure the polarization capability of bones using rabbit’s femurs. After preparing and polarizing bone samples using KOH treatment (koh), KOH and baking treatment (koh+bake) and decalcification treatment (decalcification) as well as the bone without any treatment (untreat), quantitative amounts of stored charge in samples were determined by thermally stimulated depolarization current (TSDC) measurement of these samples. Under the condition of 400 °C for 1 h with the electric fields of 5kV/cm, samples of koh, koh+bake, and untreat showed polarization capability. In addition, under the polarization condition of 37 °C for 1 hour with the electric fields of 5kV/cm, all samples showed polarization capability. Those findings can be summarized that bones have the polarization capability which enables electrical storage and polarization of bones is possible even under the low temperature condition, which was at 37 °C in our experiment, where polarization is impossible for HA.
Control of Antibiotic Delivery from TCP along with HA on Bone Cement in the Interface Bioactive Bone Cement for Prevention of Infection in Joint Replacement
Authors: Mizokawa Shigekazu , Arita Tomonori , Tachibana Akira , Tanabe Toshizumi , Oonishi Jr. Hiroyuki , Oonishi Hironobu
Published: October 2011

Since 1985, HA granules were interposed on the interface between bone and bone cement at the cementation (Interface Bioactive Bone Cement : IBBC) in THA to prevent generation of connective tissue and osteolysis. To prevent infection, β-TCP impregnated with antibiotics along with HA granules was used. As TCP is resorbable, antibiotic release can be controlled. β-TCP granules were impregnated with antibiotics of folmoxef sodium (F), Vancomycine hydrochloride (V) cefortiam dihydrochloride (C) and cefozopran hydrochloride (CE). Three models of antibiotic release were assumed. Model [1] was antibiotic release from surroundings of β-TCP granules. Model [2] was the condition loaded under normal and reduced pressure. In Model [3], β-TCP was dissolved gradually in EDTA, as the model in the living body. In model [1], the amount of release of F, V and C was 3280, 300 and 3 µg, respectively and completed in 30 hours. In model [2], the amount of release of F, V, C and CE was 16, 8, 0 and 8000 µg in reduced pressure, respectively. The release of F, V and C completed within 24 hours and that of CE was in 6 days. In model [3], released amount of C and CE was 116 and 7100 µg, respectively and completed in 19 days.
In Vitro Dynamic Degradation of Strontium-Hydroxyapatite Granules
Authors: da Silva Helena Marques , de Lima Ingrid Russoni , Bezerra Paula Gil Patrício , Peregrino Gabrielly , de Almeida Soares Gloria Dulce
Published: October 2011

The knowledge of the degradation process is an important role to understand and predict in vitro results. Granules of strontium-hydroxyapatite (Sr-HA) were submitted to a degradation process under dynamic conditions using a bioreactor system and using a solution with pH=5. The degradation process under dynamic conditions can be represented by a curve in which the calcium content firstly increases (dissolution part) followed by calcium decreasing (reprecipitation). The use of a low pH solution does not affect the curve’s shape but reduces the precipitation step.
In Vitro Evaluations of a Mechanically Optimized Calcium Phosphate Cement as a Filler for Bone Repair
Authors: Nezafati Nader , Moztarzadeh F. , Mozafari Masoud
Published: October 2011

Basic drawbacks of calcium phosphate cements (CPCs) are the brittleness and low strength behavior which prohibit their use in many stress-bearing locations, unsupported defects, or reconstruction of thin bones. Recently, to solve these problems, researchers investigated the incorporation of fibers into CPCs to improve their strength. In the present study, various amounts of a highly bioactive glass fiber were incorporated into calcium phosphate bone cement. The obtained results showed that the compressive strength of the set cements without any fibers optimally increased by further addition of the fiber phase. Also, both the work-of-fracture and elastic modulus of the cement were considerably increased after applying the fibers in the cement composition. Herein, with the aim of using the reinforced-CPC as appropriate bone filler, the prepared sample was evaluated in vitro using simulated body fluid (SBF) and osteoblast cells. The samples showed significant enhancement in bioactivity within few days of immersion in SBF solution. Also, in vitro experiments with osteoblast cells indicated an appropriate penetration of the cells, and also the continuous increase in cell aggregation on the samples during the incubation time demonstrated the ability of the reinforced-CPC to support cell growth. Therefore, we concluded that this filler and strong reinforced-CPC may be beneficial to be used as bone fillers in surgical sites that are not freely accessible by open surgery or when using minimally invasive techniques.
Carbonated Apatite, Type-A or Type-B?
Authors: Ren Fu Zeng , Leng Yang
Published: October 2011

Carbonated apatite, the basic mineral component in human hard tissues and an important bioceramic material, has been extensively studied. However, its atomic arrangements in apatite crystal structure and its experimental characterization are still not lack of debating. We analyzed infrared (IR) vibrational spectroscopy for carbonated apatite determinations, by comparatively studying the IR spectra of hydroxyapatite and of surface carbonate absorption, biological apatites (human enamel, human cortical bone, and two animal bones) and carbonated apatite. The carbonated apatite samples were sythesized by various methods, including precipitation method, hydrothermal reaction and solid-gas reaction at high temperature. The comparative study indicates that the bands at ~880 cm-1, ~1413 cm-1, and ~1450 cm-1 should not be used to identify carbonated apatite since they may result from carbonate absorption on surfaces of apatite crystals or separated carbonate phase present with apatite crystals. The IR characteristic bands of carbonate substitution in apatites should be: ν3 at ~1465 cm-1 for type-B (CO3 substituting for PO4) and ν3 band at ~1546 cm-1 for type A (CO3 substituting for OH). These signature IR bands are further confirmed by the ab initio simulations.
Biocompatibility of Carbonated Hydroxyapatite Nanoparticles with Different Crystallinities
Authors: Mavropoulos Elena , Hausen Moema , Costa Andrea Machado , Albuquerque Silvia Raquel , Alves Gutemberg , Granjeiro J.M. , Rossi Alexandre Malta
Published: October 2011

Carbonated apatite (CHA) is commonly considered a promising synthetic material for biomedical applications in orthopedic and dental surgery due to its biocompatibility, bioresorption and bioactivity. CHA5, CHA37 and CHA90 powders were synthesized from wet method and the DRX patterns showed that the crystallinity and particle size of CHA samples increased proportionally with the synthesis temperature. Powder extracts medium were obtained from each sample to interact with MC3T3-E1 osteoblastics cells. It was evaluated morphology, citotoxicity, pH and Ca2+ concentration. Citotoxicity assays showed high metabolic activity on all samples when compared to control. The polygonal shaped and the confluent monolayer observed in control cells progressively changed according to the crystallinity increase of samples. Cells under mitosis and spindle-like shaped where the main alterations observed. In addition the cell viability could be sensitive to the acid reactivity and crystallinity of carbonated apatite samples.
Investigation of HA Cement Preparation and Properties by Using Central Composite Design
Authors: Çetin Ali Emrah , Şimşek D. , Çiftçioğlu M. , Akdeniz Yelda , Özmıhçı Filiz , Yetkiner Arzu Aykut
Published: October 2011

The goal of the present work was to investigate the effects of several cement preparation parameters on setting and hardening reaction mechanisms and hydroxyapatite (HA) cement properties. A central composite experimental design (CCD) was conducted by choosing particle size, solid to liquid ratio, pH, seed concentration and buffer concentration as design parameters along with compressive strength and setting time being the responses. Tetracalcium phosphate (TTCP) powders were prepared by heat treatment of calcium and phosphate source mixtures in the 1200-1400°C temperature range followed by quenching to room temperature in a dessicator. The second phase used in the formulations (brushite) was prepared by aqueous chemical methods. A series of HA pastes/cements were prepared by changing the above mentioned design parameters. Cements were characterized by a standardized setting time test, mechanical testing machine, SEM and XRD. HA cements with the desired properties can be formulated by using CCD in which the responses were expressed by a second order polynomial equation of the parameters. Compressive strengths for the majority of HA cements were determined to be in the 100-160 MPa range which is significantly higher than those reported in the literature.
Solubility and Ingrowth Behaviour of Degradable and Figuline Calcium Alkaline Phosphate Cements
Authors: Dombrowski F. , Marx Heidi , Ploska Ute , Nicolaides D. , Stiller M. , Knabe Christine , Berger Georg
Published: October 2011

The thrust of the investigations presented here is to point out the degradation behaviour in vitro and the ingrowth behaviour in vivo of four different calcium alkaline phosphate cements. Two of the figuline and mouldable composites consist of the crystalline phase Ca2KNa(PO4)2 and two of the crystalline phase Ca10[K/Na](PO4)2 each containing 2wt% medium gel strength porcine gelatin. Furthermore Α-TCP was added to both Ca10[K/Na](PO4)2 cements as a hardening supporting reactant. The testing material groups differ in small amorphous portions containing either silica phosphate (GB9), magnesium potassium phosphate (GB14) or diphosphates (401545 and 401545(70)). The respective composites show a monomodal particle size distribution (d50~7µm; span~4) and an average total porosity around 28vol%.For the solubility studies cylindrical samples (d=6mm; h=12mm) were stored in a 0.1mol TRIS buffer solution and incubated at 37°C for maximum 50 weeks. The storage solution was analysed and renewed every week. The results are plotted cumulative. For the in vivo studies critical size defects were dissected to mandibles in a sheep model in which a 1cm3 area of the bottom of the mandibles was surgically resected and replaced with the figuline cements whereas the mouldability allows the reconstruction of the original outer contour without draining off even when replacing upside down.
Effect of the SBF Concentration on the Apatite-Forming Ability of ASTM F75 Alloy Induced by Wollastonite
Authors: Ortiz-Cuellar J.C. , Cortés-Hernández Dora A. , Escobedo-Bocardo José C. , Muñiz Valdez C.R. , Luna Alvarez J.S. , Rodríguez-Rosales N.
Published: October 2011

A method to promote a bioactive surface on the cobalt base alloy ASTM F75 was tested. A set of cylindrical samples was obtained using the investment casting technique and one of the flat surfaces of each sample was polished. The samples were packed in wollastonite powder and then heat treated for 1 h at 1220°C. To characterize the in vitro bioactivity, a set of heat treated metallic specimens was immersed in a simulated body fluid with an ionic concentration nearly equal to that of human blood plasma (SBF) for 7, 10 and 21 days. To evaluate the effect of increasing the concentration of the simulated body fluid on the bioactivity of the material, a second set of heat treated samples was immersed in a more concentrated solution (1.5 SBF). In both cases the solution was renewed every 7 days. After heat treatment, fine agglomerates homogeneously distributed, containing O, Ca, Si and Al were observed on the metallic surface. After immersion of the samples in simulated body fluids, a ceramic layer containing Ca and P was formed on all the samples. A thicker layer, identified as apatite by XRD, was formed on the samples immersed for 21 days in SBF and as early as 7 days in 1.5 SBF. This may indicate that the heat treated material is useful for bone replacement and tissue regeneration under highly loaded conditions.
Characterization of Plasma Sprayed Yittria Stabilized Zirconia (8 wt %) Hydroxyapatite Coatings
Authors: Anzabi O. , Aydin M.M. , Ozyegin L.S. , Oktar F.N. , Gross Kārlis A. , Göller G. , Kayali E.S. , Erkmen E.Z.
Published: October 2011

Splitting problems at HA-coated implants are generally due to biological reasons. Bond-coatings were used to prevent the splitting problem of zirconia ceramics; this method can be widely seen in industrial applications. Two main groups were used; the first group consisted of spraying a bond layer of titania onto commercially pure titanium. This followed by a spray of HA with 5, 10 and 15 % zirconia (8 % yttria doped) as main layer onto the first bond-coating. For the second group, the samples were coated without bond-coating. Firstly, X-ray diffraction patterns of the starting powders were taken. Then x-ray diffraction patterns of the plasma sprayed samples were taken. In literature, it was seen that 20 % zirconia was sufficient for the transformation into a monoclinic structure for the bond-coated samples. For this study it was found that 10 % zirconia was sufficient to transform to the same structure of the desired crystalline phase transformation. The coating kept its crystal structure and relatively small amount of amorphous transformation was detected. A similar structure was produced using less zirconia. It was thought that the use of titanium-oxide bond-coating layer would play an important role as a third variable in the results. To further investigate these phenomena, more detailed researches must be conducted with using titanium-oxide yittria stabilized zirconia (8 wt %) hydroxyapatite bond-coatings with HA main coatings.
Fabrication of Bioactive Apatite Nuclei-Precipitated Composites
Authors: Yabutsuka Takeshi , Yao Takeshi
Published: October 2011

Many micropores were formed on the surface of a Ti-15Mo-5Zr-3Al alloy plate and a polyethylene terephthalate (PET) plate by sandblasting, Apatite Nuclei were precipitated in the pores, then bioactive Apatite Nuclei-precipitated composites were fabricated. In order to examine the bioactivity, the composites were soaked in SBF and it was observed that hydroxyapatite was induced on the whole surface within 1 d. The hydroxyapatite layer possessed high adhesive strength to the plate due to a mechanical interlocking effect between hydroxyapatite in the micropores and the plate.
Effect of In Vitro Ageing on a Cold Isostatic-Pressed Zirconia Ceramic for All Ceramic Restorations
Authors: Vatali A. , Siarampi E. , Kontonasaki Eleana , Kantiranis Nikolaos , Zorba T. , Vouroutzis N. , Paraskevopoulos Konstantinos M. , Koidis Petros
Published: October 2011

High strength of Yttria stabilized tetragonal zirconia polycrystal (Y-TZP) zirconia ceramics are sensitive to low temperature degradation (LTD) that leads to exaggerated tetragonal to monoclinic transformation and a surface to depth propagating degradation that diminishes their mechanical properties. In vitro tests for accelerating ageing have been proposed for the prediction of zirconia ceramics clinical performance. The aim of the present work was to investigate the in vitro ageing of a cold isostatic-pressed zirconia ceramic for all ceramic restorations. Bar-shaped specimens milled from a zirconia block (Ivoclar IPS e.max ZirCAD) were sintered to full density, mirror-polished and cut into two equal pieces. One piece was used as control while the other was subsequently aged (steam 134°C / 2 bars / 10 hours). Atomic Force Microscopy (AFM) was used to evaluate the surface profile and the micro-structural features before and after ageing. Fourier Transform Infrared Spectroscopy (FTIR) and X-Ray Diffraction Analysis (XRD) were used to determine the degree of the m-ZrO2 transformation. Ageing resulted in an increase of the surface roughness, while the formation of monoclinic spots on the surface of the specimens was verified by surface uplifts in the AFM images. The peaks of the m-phase were clearly observed in the FTIR spectra while an average increase of 16% w.t. of the m-ZrO2 phase was recorded by XRD. Although, no sound lifetime predictions can be made from accelerated tests, based on the ISO standard that imposes that the m-phase should not exceed 25% wt after 5h at 134 °C and 2 bar pressure, it can be concluded that the tested ceramic resisted an extreme transformation that could negatively affect its clinical performance.
Investigation of Strontium Effect on the Bioactive Behavior of Glasses in the System SiO2-CaO-P2O5-Na2O-SrO
Authors: Erol M. , Özyuğuran A. , Özarpat Ö. , Küçükbayrak S.
Published: October 2011

In this study, it was aimed to produce bioactive glasses (SiO2-CaO-P2O5-Na2O-SrO) with the substitution of strontium in different weight percentages. Physical, thermal, and in vitro biological properties of the glasses were studied and compared to each other. In vitro simulated body fluid studies were performed to investigate the bioactivity of the produced glass samples. Scanning electron microscopy, X-ray diffraction, ultraviolet spectroscopy and inductively coupled plasma techniques were used to monitor changes in the glass surface and SBF composition. The results showed that all glasses favored precipitation of calcium phosphate layer when they were soaked in SBF; however bioactivity of the glasses increased with the increase of strontium content in the glasses.
In Vitro Evaluation of Hydroxyapatite-Containing Glass Coating on Zirconia
Authors: Yamashita Daisuke , Noda Makoto , Machigashira Miho , Miyamoto Motoharu , Takeuchi Hironobu , Takeuchi Naoshi , Kono Hiroshi , Noguchi Kazuyuki , Ban Seiji
Published: October 2011

The aim of this study was to investigate the response of osteoblast-like cells (MC3T3-E1) to the surface of hydroxyapatite-containing glass coating on zirconia (HA-G-Zr) in comparison to yttria stabilized zirconia (Y-TZP). The MC3T3-E1 cells were cultured on HA-G-Zr and Y-TZP specimens in 24-well tissue culture plates. Surface properties were evaluated by X-ray diffractometry, Fourier tranfer infrared microscopy (FT-IR) and scanning electron microscopy (SEM). Cell proliferation in each well was measured by MTT assay. Cell morphology was observed by SEM. Cell differentiation was evaluated by alkaline phosphatase (ALP) activity and osteocalcin levels. After the glass coating on Y-TZP, X-ray diffraction peaks due to hydroxyapatite (HA) were observed clearly. HA-G-Zr appeared on surface of uneven and roughened state, wherein microcracks on the microns in width and many voids of several microns in size were present. Time-dependent proliferation and differentiation of MC3T3-E1 cells were found in all the specimens. MC3T3-E1 cells on HA-G-Zr plates showed higher differentiation than Y-TZP. These results demonstrated that HA-G-Zr showed better cellular biocompatibility than Y-TZP.
Comparison of Bone Substitutes in a Tibia Defect Model in Wistar-Rats
Authors: Ganz Cornelia , Xu W. , Holzhüter G. , Götz W. , Vollmar B. , Gerber Th.
Published: October 2011

Various bone graft substitutes were used in clinical practise in the treatment of bone defects after trauma or osteoporosis. Many synthetic biomaterials were developed in recent years primarily based on hydroxyapatite (HA). NanoBone® is a nanocrystalline hydroxyapatite (HA) embedded in a porous matrix of silica (SiO2). The ratio of HA:SiO2 varied between 76:24 (wt%; NanoBone®) and 61:39 (wt%; Nanobone® S). The two bone substitutes NB and NB S and a natural bovine bone substitute Bio-Oss® (BO) were evaluated by means of implantation in the tibia of the rat. The aim of this study was to analyze the remodelling process and to measure new bone formation and degradation after implantation of these biomaterials. A tibia defect model was used for all investigations with testing periods of 12, 21 and 84 days. (n=5 for each time point). The results showed, that all bone grafts were well accepted by the host tissue without inflammatory reactions. In comparison to the biomaterial BO, NanoBone® and NanoBone® S were quickly degraded, whereas autologous proteins were incorporated into nanopores. New bone formation was statistically higher in NanoBone® S compared to Bio-Oss® in defect area after 84 days implantation. The presence of osteoclasts in tissue sections were demonstrated by TRAP- and ED1-immunohistology.
X-Ray Peak Broadening and In Vitro Dissolution Studies of Thermally Stabilized Nanocrystalline Carbonated Hydroxyapatite
Authors: Pavankumar K. , Venkateswarlu K. , Nagumothu Rameshbabu , Muthupandi V.
Published: October 2011

The present work aims to examine the effect of silicon substitution on thermal and in-vitro dissolution properties of carbonated hydroxyapatite. Hydroxyapatite [Ca10(PO4)6(OH)2, HA], carbonate substituted hydroxyapatite [Ca10(PO4)6-x(CO3)x(OH)2, x=1, 1CHA] and carbonate, silicate co-substituted hydroxyapatite [Ca10(PO4)6-x-y(CO3)x(SiO4)y(OH)2, x=1,y=1, 1C1SiHA] nanoparticles were prepared by microwave synthesis method under identical processing conditions. The XRD results of HA, 1CHA and 1C1SiHA correspond to the standard hexagonal HA (JCPDS 9-432). The crystallite size and lattice strain of the synthesized powder particles were estimated by Williamson-Hall isotropic strain model (W-H ISM) from powder X-ray diffraction data. The dislocation density was calculated by Williamson-Smallman formula. The functional groups present in the as-synthesized powder particles were analyzed by Fourier transform infrared (FT-IR) spectroscopy method. The size and the morphology were examined using a transmission electron microscope (TEM). The in-vitro dissolution behaviour of the synthesized powder particles was studied by ethylenediamine tetra-acetic acid (EDTA) titrimetric method. The W-H ISM results confirm that the prepared powder particles of HA, 1CHA and 1C1SiHA are nanocrystalline with an average crystallite size of 40 nm, 36 nm and 32 nm, respectively. Thus the crystallite size of hydroxyapatite was observed to be decreased gradually with increase in substitutions as indicated by the least size for the 1C1SiHA. In addition, the XRD results of powders annealed at 900 °C for 2 h show the improved thermal stability of 1C1SiHA compared to 1CHA. The TEM results show rod-like shaped morphology for HA, near rod-like with modified edge morphology and increased agglomeration for 1CHA and needle-like shaped morphology for 1C1SiHA powder particles. The in-vitro dissolution study results show a gradual increase in the solubility of HA with carbonate and carbonate-silicate co-substitutions. The calculated microstructural parameters, namely, crystallite size, root mean squared strain and dislocation density were correlated with in-vitro dissolution behaviour of hydroxyapatites.
Controlled Synthesis, Characterization and Magnetic Properties of Magnetite (Fe3O4) Nanoparticles without Surfactant under N2 Gas at Room Temperature
Authors: Raz M. , Moztarzadeh F. , Hamedani A.Ansari , Ashuri Maziar , Tahriri M.
Published: October 2011

In this study, magnetite (Fe3O4) nanoparticles were synthesized at room temperature using FeCl3.6H2O (1.28 M), FeCl2.4H2O (0.64 M) and HCl (0.4 M) for preparing a solution as the iron source and NaOH (0.9-1.5 M) for to prepare a solution as the alkali source by the aqueous phase co-precipitation method under vigorous mechanical stirring (450 and 750 rpm) together with N2 gas flowing through the reaction medium during synthesis operation in closed system. The powder samples were characterized by the commonly used techniques of scanning electron microscope (SEM), transmission electron microscope (TEM), Fourier transform infra-red (FTIR), X-ray diffraction (XRD), vibrating sample magnetometry (VSM) and BET analyses. SEM was used to observe the morphology and agglomeration state of the powder. Size and morphology of the precipitated crystallites were examined with TEM. The prevalence of functional groups in the synthesized powders was ascertained by FTIR spectroscopy. The pure magnetite and other phases according to processing parameters were observed by XRD analysis. The magnetic properties of magnetite (Fe3O4) nanoparticles were examined using VSM. Finally, the specific surface area of nanoparticles was measured by BET technique. The results indicate that smaller particles can be synthesized by increasing stirring rate and decreasing the NaOH concentration, which in this case corresponded to 35 nm using 0.9 M NaOH at 750 rpm. The VSM analysis showed a saturation magnetization range of (82-96 emu/g) and coercivity of (83-119 Oe) for particles between (35-96 nm) respectively. Also, the highest specific surface area of 40 m2/g was obtained at 0.9 M NaOH at 750 rpm and the smallest value of 15 m2/g at 1.5 M of NaOH at 450 rpm using BET analysis.
Improvement of Bone Ingrowth on PEEK Surface Implant
Authors: Daculsi Guy , Goyenvalle E. , Aguado E.
Published: October 2011

It was demonstrated that microstructured surfaces improve cell spreading and bone ingrowth. Particularly, the surface roughness modulates the osseointegration of orthopaedic and dental implants. We have developed an innovative grit blasting process using Biphasic Calcium Phosphate, a Resorbable Biocompatible Blast Media (RBBM). PEEK is biocompatible but an inert material, involving no direct bone bonding. Implants coming from a rabbit experimental study, were processed for X-rays Micro tomography. Light microscopy and SEM were performed.It was demonstrated in this study that the surface treatment on PEEK improve the quality of bone architecture in direct contact with the sample surface, compared to the classical surface of PEEK. These data demonstrate that PEEK rough surface obtained by RBBM blasting maintain high biocompatibility and bone osteoconduction, and promote higher stability of the implant.
BMPs as Adsorptive Proteins for Ceramic Scaffolds
Authors: Ito K. , Murata Masaru , Hino J. , Tazaki Junichi , Akazawa T. , Arisue M.
Published: October 2011

Body fluid permeability and blood compatibility of biomaterials are especially critical properties for regenerative bone therapy [1, 2]. To have a role in bone repair, biomaterials must have the adsorptive performance of various bone growth factors. The bone-inductive property of rabbit dentin was discovered in 1967 [3]. In our previous study, we have been researching the autograft of human demineralized dentin matrices (DDM) as a clinical study [4]. DDM is an acid-insoluble collagenous material. On the other hand, hydroxyapatite (HAp) is a mineralized material. Commercially available HAp block (APACERAM-AX®,85%-porosity with micropore) has been used as the artificial biomaterial in bone therapy [5]. Bone morphogenetic proteins (BMPs) are the strong hard tissue-inducing factors [6]. In this study, we investigated the existence of BMP-2 and -7, among proteins adsorbed to DDM and HAp, using immunoblottong analyses. The DDM granules and HAp blocks (64mm3) were implanted subcutaneously in 8-week-old Wistar rats, and sacrificed at 2 days after the implantation. Explanted DDM and HAp were homogenized by the ultrasonic procedure in phosphate-buffered saline (PBS) and the adsorbed proteins were separated on a 5-20% sodium dodecyl sulphate (SDS) polyacrylamide gradient gel by electrophoresis. For Western blotting, proteins in the gel were transferred to a polyvinylidene difluoride membrane and detected by anti-BMP-2 monoclonal antibody and anti-BMP-7 monoclonal antibody. BMP-2 and BMP-7 were detected as a major band at 50 kDa among proteins collected from the in vivo implanted DDM and HAp. BMP-2 was detected the second major band at 125 kDa in HAp and both BMP-2 and BMP-7 were detected the some minor bands in DDM and HAp. The bands of BMP-2 were stronger than those of BMP-7 in all. The DDM and HAp adsorbed BMP-2 and BMP-7. These results indicate that DDM is a useful bone substitute as much as HAp, adsorbed to the bone-inducing factors, in the bone engineering field.
Structural Optimization of Macroporous Magnesium Phosphate Scaffolds and their Cytocompatibility
Authors: Ewald Andrea , Lochner Bernhard , Gbureck Uwe , Groll Jürgen , Krüger Reinhard
Published: October 2011

Mg-phosphate ceramics have aroused growing interest as bone replacement materials due to their ability to degrade under physiological conditions. To mimic cancelous bone and to promote tissue repair mechanisms a highly macroporous structure with open cells is desired. In this study trimagnesium phosphate (farringtonite, Mg3(PO4)2) and struvite ((NH4)Mg(PO4)·6H2O) scaffolds were developed as open cell foams using the Schwarzwalder-Somers technique and optimized for pore size and mechanical performance. Polyurethane (PU) foam (20-80 ppi) was used as a template. For the optimization of the farringtonite scaffolds, ppi number of the PU foam as well as the technique that was used to remove excess slurry were varied. Sample characterization was done by SEM, XRD and compression testing. For best results were obtained using 60 ppi PU foams leading to a compressive strength of 58 kPa (90 % porosity). Farringtonite scaffolds were modified by either polymer infiltration or transformation into struvite with an ammonium phosphate solution. The pore macrostructure was retained for both of these processes and a reduction of porosity was observed. The microstructure of struvite foams was significantly altered showing larger and more facetted crystals than farringtonite. Mechanical properties substantially improved by transformation into struvite to 730 kPa (68 % porosity). Cytocompatibility was tested using osteoblasts and fibroblasts. Cell number and cell activity (WST) were tested over a period of 3 to 13 days. Farringtonite foams showed a tendency for higher cell numbers than struvite, while the WST activity was similar. Infiltration of farringtonite with PLGA approximately doubled cell number compared to pure farringtonite. In conclusion macroporous Mg-phosphate foams have been successfully produced. Compressive strength of the foams was drastically improved by optimization of pore fineness, transformation to struvite and infiltration with PLGA. The open porous structure was retained and the materials showed good cytocompatibility.
Hydroxyapatite Scaffolds Produced by Hydrothermal Deposition of Monetite on Polyurethane Sponges Substrates
Authors: Mishima Fernanda Danielle , Louro Luis Henrique Leme , Moura Felipe Nobre , Gobbo Luciano Andrade , Prado da Silva Marcelo Henrique
Published: October 2011

Hydroxyapatite scaffolds have been being produced by a wide range of processes. The optimun material to be used as bone graft has to be partially resorbable, with resorption rates similar to new bone formation ones. The samples must have porosity compatible with tissue ingrowth. Hydroxyapatite and tricalcium phosphate ceramics are good choices for designing such materials. In the present study, polymeric sponges were coated with hydroxyapatite and sintered. The method consists of coating polyurethane sponges substrates in an aqueous solution rich in phosphate (PO4)3- and calcium (Ca)2+ ions. The solution is composed by 0.5M Ca(OH)2, 0.3M H3PO4 and 1M CH3CHCO2HOH (lactic acid) at pH of 3.7. The sponges were immersed in a beaker with the solution and heated up to 80°C to precipitate monetite on the sponge. Continuous and adherent coatings were formed on the surface of sponges interconections. These coatings were characterised by X-ray diffractometry and the only identified phase was monetite. The substrates were converted to hydroxyapatite in an alkali solution.The total conversion from monetite to hydroxyapatite was confirmed by XRD analyses. The struts were heat treated in order to eliminate the organic sponge and sinter the scaffolds. After sintering, hydroxyapatite and tricalcium phosphate were identified on the struts. Optical microscopy revealed the morphology of the struts, while scanning electron microscopy (SEM) showed the precipitates morphology. The method showed to be efficient in the production of porous scaffolds.
Cell Migration Ability Test for Bioactive Ceramics toward International Standardization of Ceramics for Regenerative Medicine
Authors: Kikuchi Masanori
Published: October 2011

International standard for test method on cell migration into a scaffold is one of the important things to evaluate the scaffold. The "cell migration" ability can divide into two parts. One is infiltration of cell suspension before in vitro cell culture on the scaffold. Another is migration of adherent cells from the edge of scaffold. The latter one could be closely related to cell/tissue migration into the scaffold when it is implanted into bone. Thus, in the present study, the cell migration ability was evaluated toward standardization of in vitro evaluation method for in vivo cell/tissue migration ability using several bioactive ceramics and composites including commercially available materials. The specimen 5 mm in diameter was placed on confluent MG63 cell layer. After 3 days incubation, the specimen was harvested, fixed and divided into two parts. Inside and outside of the scaffold were stained by Giemsa and observed by optical microscopy. In addition, the same specimen was critical point dried and observed with scanning electron microscope (SEM). From microscopic observation, MG63 cells migrated to pore walls of the specimen as well as a sidewall. Maximum migration distances were different among specimens and seemed to depend on pore structure and size as well as porosity. Similar behaviors were observed with SEM.Even relations between this test method and in vivo cell/tissue migration have not been evaluated, this test method is potentially a good method for testing cell migration ability of porous bioactive ceramics as well as other porous scaffold materials.
Mechanical Performance and In Vitro Studies of Hydroxyapatite/Wollastonite Scaffold for Bone Tissue Engineering
Authors: Padmanabhan Sanosh Kunjalukkal , Carrozzo Marina , Gervaso Francesca , Scalera Francesca , Sannino Alessandro , Licciulli Antonio
Published: October 2011

A highly porous (~90%) interconnected hydroxyapatite/wollastonite (HA/WS) scaffolds were prepared by polymeric sponge replica method using a slurry containing HA:Calcium silicate in the weight ratio of 50:50 and sintered at 1300 °C. The phase purity of the scaffolds were analyzed by using XRD. The pore size, pore structure, microstructure and elemental analysis of the scaffolds before and after SBF soaking were analyzed using SEM and EDS. In-vitro bioactivity and bioresorbability confirmed the feasibility of the developed scaffolds. The HA/WS scaffold shows two fold increase in the compressive strength compared to pure HA scaffold.
Static and Dynamic Degradation of Sintered Calcium Phosphate Ceramics
Authors: Newe C. , Cunningham E. , Buchanan F. , Walker G. , Prendergast P. , Lennon A. , Dunne N.J.
Published: October 2011

The chemical compositions of calcium phosphate materials are similar to that of bone making them very attractive for use in the repair of critical size bone defects. The bioresorption of calcium phosphate occurs principally by dissolution. To determine the impact of composition and flow conditions on dissolution rates, calcium phosphate tablets were prepared by slip casting of ceramic slips with different ratios of hydroxyapatite (HA) and β-tricalcium phosphate (β-TCP). Dissolution was evaluated at pH4 using both a static and dynamic flow regime. Both the composition of the HA:β-TCP tablet and flow regime noticeably influenced the rate of dissolution; the 50:50 HA:β-TCP composition demonstrating the greatest level of dissolution, and, exposure of the ceramic specimens to dynamic conditions producing the highest rate of dissolution. Understanding the impact of phase composition and flow condition with respect to the dissolution of calcium phosphate will aid in the development and improvement of materials for bone substitution.
Ti4O7 Used as Electrode in Biomedicine and for Electrochemical Study of Scavenging Mechanism
Authors: Canillas María , Rajnicek Ann , Rosero C. , Chinarro Eva , Moreno Berta
Published: October 2011

The biocompatibility of TiO2 is due to the activity that it shown in front of oxygen and nitrogen reactive species. Some authors suggest that the mechanism go through oxidation reduction reactions where changes of oxidation state in the Titanium and phases are involve. For this reason, Anderson-Magnelli phases could present scavenging activity. Moreover, these materials are use as electrodes and in that way are proposed as electrodes for study their scavenging mechanism by electrochemical methods.
Biological Evaluation of a Novel Tissue Engineering Scaffold of Layered Double Hydroxides (LDHs)
Authors: Fayyazbakhsh Fateme , Solati-Hashjin Mehran , Shokrgozar M.A. , Bonakdar S. , Ganji Y. , Mirjordavi Navid , Ghavimi S.A. , Khashayar P.
Published: October 2011

Bone Tissue Engineering (BTE) composed of three main parts: scaffold, cells and signaling factors. Several materials and composites are suggested as a scaffold for BTE. Biocompatibility is one of the most important property of a BTE scaffold. In this work synthesis of a novel nanocomposite including layered double hydroxides (LDH) and gelatin is carried out and its biological properties were studied. The co-precipitation (pH=11) method was used to prepare the LDH powder, using calcium nitrate, Magesium nitrate and aluminum nitrate salts as starting materials. The resulted precipitates were dried. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) analyses were used to characterize the synthesized powders. The results demonstrated the presence of nanocrystals of Ca-LDH and Mg-LDH as Hexagonal and Layered Morphology. The obtained powders were composed to gelatin via solvent casting method then freez dried. The scaffold was prepared via membrane lamination method from the resulted layers that linked together with gelatin as binder. In order to investigate the scaffold cytotoxicity MTT assay was done with a osteosarcoma cell line. No toxic response was observed in specimens. As a major result, it was demonstrated that the specimen showed a significant cellular response. Then osteosarcoma cells were cultured for 7-day and 14-day extract of powders. The composites osteoconductivity was investigate with cells alkaline phosphatase extraction. The results demonstrated that the Ca-LDH/gelatin composite scaffold has a good potential for bone tissue engineering applications and Mg-LDH specimen has a better osteconductivity.