bluuebunny/crossref_metadata_2025 huggingface dataset:
Evaluation Strength and Fracture Toughness of Reduced Activation Ferritic Steel (JLF-1) for Fusion Reactor
Authors: Yoon Han Ki , Kim D.H. , Park Yi Hyun , Kong Yu Sik , Kohyama Akira
Published: March 2009

Reduced activation ferritic (JLF-1) steel is one of the leading candidates for blanket/first-wall structures in D-T fusion reactors. In fusion applications, structural materials will suffer the effects of repeated temperature changes. Therefore, a database of tensile strength and fracture toughness are very important as the temperature is 400 ° C and it's TIG welded joint. In this paper, fracture toughness JIC and KIC) and tensile tests were carried out at room temperature (RT) and at elevated temperature (400 ° C). The tensile properties of the TIG welding joint of JLF-1 steel was also investigated. It was shown that the tensile strength and fracture toughness values of the JLF-1 steel
are slightly decreased with as increase in temperature. The fracture toughness values of JLF-1 steel at room temperature and at 400°C show excellent JIC values of about 530 kJ/m2 and 340 kJ/m2, respectively.
Study on Fracture Properties of High-Density Polyethylene (HDPE) Pipe
Authors: Qi Fang Juan , Huo Li Xing , Zhang You Feng , Jing Hong Yang
Published: March 2009

Butt-fusion welding is the main technology to join high-density polyethylene (HDPE) plastic pipes, which are widely used in transport the water, gas and corrosive liquid. Investigation shows that one of the failure modes of HDPE pipe is the crack slowly grows across the thick direction and leads to failure at last, so that it is very important to study the resistance to crack initiation of HDPE pipe and its butt-fusion welded joint. In this study, the elastic-plastic fracture mechanics parameter, crack opening displacement (COD) is used to describe the fracture initiation behaviors for the HDPE materials and its butt-fusion welded joints. The resistance to initiation fracture of HDPE pipe materials and butt-fusion welded joints were investigated at different temperature by using multiple specimen resistance curve method and silicon-rubber replica method. The results show that saturation initial crack COD- δis of HDPE pipe materials and butt-fusion welded joints decreases with the decreasing temperature. The δis of butt-fusion welded joints is lower than that of HDPE pipe materials. Investigation also proved that the silicon-rubber replica method is more suitable for HDPE engineering material than the multiple specimen method. At the same time the statistic distribution of the δis of HDPE butt-fusion welded joint was conducted. The results show that the value of the δis has the statistic variance inherently. The optimum fitting distribution of COD is Weibull distribution with three parameters.
Analysis on the Temperature Distribution of Tread Part in Running Tire
Authors: Yang Dong Jo , Kim Jae Yeol , Oh Yool Kwon , Cho Young Tae , You S.
Published: March 2009

Tires are the only means for connecting a vehicle to the ground. The forces such as driving force, braking force, rotation force and the like occur on the contact surface between the tire and the ground and thus determine the motion of the vehicle. A general tire generates separation that continues to repeat tension and compression by the load of the vehicle. The separation raises the temperature of the tire, resulting in loosening between tire members and in the end damages the tire. Since a tire has a composite structure, which consists of rubber and reinforcements, many problems arise in the analysis of the tire. In this study, a tire of a composite structure was analyzed for heat transfer under the same condition as in the running state, so as to examine temperature distribution at tread. Theoretical results were verified using a thermal vision camera a non-contact non-destructive temperature measurement instrument.
Nonlinear Acoustoelastic Interactions of Lamb Waves with LiNbO3 Films Deposited on Sapphire Substrates
Authors: Liu H. , Shin K.C. , Lee J.J. , Cai Z.M.
Published: March 2009

The influence of a biasing electric field on the propagation of the lowest-order antisymmetrical a0 Lamb wave modes in a bi-layered piezoelectric plate is investigated in this paper. It is found that the velocity shifts for the a0 mode due to presence of the bias field on the 10- µm LiNbO3 film structure are comparable with those observed in surface acoustic waves and Lamb waves in LiNbO3 plates. The fractional change in phase velocity of the layered piezoelectric structure is a linear function of the biasing electric field and can be used in voltage sensors.
Numerical Simulation of Impact Transonic Interfacial Fracture
Authors: Nishioka Toshihisa , Tsuda T. , Fujimoto T.
Published: March 2009

In transonic interfacial crack propagating fracture problem, the generation-phase simulations were done using the moving finite element method based on Delaunay automatic mesh generation. And the contact function based on the penalty method was newly developed to consider the crack face contact near the propagating interfacial crack tip.
It was succeeded to visualize in 3-dimensions the Mach shock wave emanated from the propagating crack tip. And it was tried for the transonically propagating crack problem that solving the energy flows through the contact zone or along the Mach shock wave line emitted from the crack tip. The energy flow patterns into the crack tip were also visualized. Furthermore, from the values of the separated dynamic J integrals, it was found that the dynamic J integral is non-zero even for transonic fracture region and the most of the energy release rate is provided from the more
compliant material epoxy.
The Singularity in Multi-Material Wedges under Thermal Loading
Authors: Hwu Chyan Bin , Lee Won Jun
Published: March 2009

By employing the Stroh formalism for plane anisotropic thermoelasticity, closed-form solutions for the orders of stress and heat flux singularities of multi-material wedges have been obtained. Several different boundary conditions are considered in this paper such as insulated or isothermal as well as free-free or fixed-fixed or free-fixed or fixed-free wedge boundaries. The solutions show that the singular orders are influenced by the wedge configurations (n wedge angles), boundary conditions, elastic constants and heat conduction coefficients, but are independent of the thermal moduli.
Measurement of Mechanical Properties of Electroplated Nickel Thin Film
Authors: Baek Dong Cheon , Park Tae Sang , Lee Soon Bok
Published: March 2009

Electroplated nickel manufactured via the LIGA process, offers the possibility of stronger structure and connectors in a micro electro mechanical systems (MEMS). In this study, the mechanical properties of electroplated Nickel thin film were characterized using two methods; tension test and nano-indentation test.
In tension test, a linear guided motor was used as actuator and the applied force was measured using a load cell. Strain was measured with a dual microscope that obtains the displacement of two separated zone by the tracking process of the image captured with CCD camera. In indentation test, elastic modulus was measured using a CSM(continuous stiffness measurement) module.
Two types of specimen were prepared in the same wafer and tested after four months of aging, which reduces the variation of properties caused by fabrication condition and aging effect. The tension specimen is 15 µm thick and 300 µm wide. The indentation specimen is also 15 µm thick. Young's modulus were measured by two different testing methods and compared quantitatively.
Properties of WC-Co Ceramic Coatings of Ultra-Fine Grains Prepared by Electro-Thermal Explosion Method
Authors: Liu Zong De , Yang Kun , Bai Shu-Lin , Duan Peng
Published: March 2009

The high velocity spraying experiments for preparing WC-Co ceramic coatings were carried out by using an electro-thermal explosion directional spraying device. The transient parameters of both the discharge circuit and the voltage applied to the WC-Co sheet were measured. Velocity of the shock wave in the explosive spraying nozzle was approximately measured and that was described with a one-directional piston model. The velocity of molten particles of WC-Co ceramics was estimated to be about 3162m/s. The microstructures and micro-hardness of the WC-Co coating, the interface between the coating and substrate were analyzed in details. The visible WC grain diameter of the coating ranges from 70 to 350nm, and the average value is 195nm. A metallurgical bonding layer with a thickness of about 1 was found at the interface. The values of micro-hardness of the coating are 1-1.4 times of the original one, and the micro-hardness near the interface is much higher than that of the substrate
Finite Element Analysis on the Scoring and the Opening Process of Steel Can
Authors: Huh S.I. , Jung S.W. , Jung C.K. , Han Kyung Seop
Published: March 2009

This study simulated the Scoring process and the Can opening process of Easy Open End by finite element method. A FEM model was developed to predict the limitation of the scoring depth and the opening force at the End of steel Can using ABAQUS. In spite of a complex 3D structure, the shape of the Can End was simplified 2D axisymmetric model and analyses were focused on the change of materials and score shapes.
Adaptive meshing was applied to the region of the score in the scoring process in order to suppress large deformation of elements. The critical depth of the scoring was observed because necking occurred at the panel during the scoring process. Necking could be restrained by changing the shape of the score punch. For the opening simulation, the shear failure model was utilized. The opening force was predicted with various materials, residual thickness, panel thickness (thickness ratio) and score shapes. The influence of these factors changed with the thickness ratio. Synthetically, the score condition of the steel Can End that the opening force is similar to the aluminum End was proposed.
Stress Analysis and Design Strategy for Lightweight Car Seat Frame
Authors: Kim Hong Gun
Published: March 2009

A seat frame structure in automotive vehicles made of polymer matrix composite(PMC) with reinforced by X-shape steel frame was developed to obtain weight reduction at low cost. The frame structure was designed and analysed using
finite element analysis(FEA) and was compared with experimental impact test to verify the structural safety after fabricated. The design model based on safety was analysed with appropriate boundary conditions and loading conditions. Each result was utilized to modify the actual shape to obtain a lighter, safer and stabler design. It was found that the substitution of PMC material reinforced by an X-shaped steel frame resulted in a weight reduction effect with equivalent strength, impact characteristics and fracture property.
Atomistic Simulations of Dislocation-Loop Glidings in Al(111) Nanoindentation
Authors: Jun Sukky , Lee Young Min , Kim Sung Youb , Im Se Young
Published: March 2009

Molecular dynamics simulation of nanoindentation on Al(111) surface is presented. The simulation is performed using the Ercolessi-Adams glue potential and the Berendsen thermostat. Boundary conditions of 'pseudo' thin film are imposed in order to focus on the dislocation motion in ultra-thin film. Nucleation and development of defects underneath the indenter tip are visualized, and the gliding patterns of dislocation loops are investigated with particular emphasis on the effect of film thickness. Simulation results show that the early emission of dislocation loop is highly
dependent on the film thickness.
Effect of Columbic Force on Piezoelectric Fracture
Authors: Gao Cun Fa , Tong Pin , Zhang Tong Yi
Published: March 2009

This paper studies the effect of the Columbic force on piezoelectric fracture. Bound charges emerge on the upper and lower surfaces of a permeable crack when a piezoelectric solid with the crack is subjected to far-field mechanical/electric loading. Taking into account the Columbic force between the bound charges, we obtain a non-linear equation governing the normal component of electric displacement D2(x1)on the crack faces. The results show that D2(x1)is, in general, not a constant along the crack faces and depends on the mechanical/electric loading conditions, the crack
profile and the material properties outside and inside the crack. Furthermore, we examine the Columbic force under low mechanical/electric loads and then discuss the effect of the Columbic force on the fracture behaviour of piezoelectric materials.
Sensitivity Analysis of Major Parameters on Piping Failure Probabilities
Authors: Jung Sung Gyu , Lee Chang Soon , Park In Gyu , Lee Se Hwan , Jin Tae Eun
Published: March 2009

In-service inspections (ISI) of pipes in the nuclear power plants are currently performed based on mandated requirements in the ASME Section XI, which is based on deterministic approach of the critical welds. The 20 years of ISI experience in U.S.A. has revealed less correlation between the critical welds and actual failures, and much conservatism in current ISI requirements. To reduce those problems, risk-informed ISI technology has been developed and proved to be useful. This paper presented a method for predicting piping failure probabilities in an application of
risk-informed ISI, and analyzed the effect of input parameters on piping failure probabilities. Results generated using this approach revealed that the calculated failure probabilities can be sensitive to the different types of stressors, crack size distribution, inspection interval, etc..
Comparison of the Electric Properties and ESCA Result of Oxide Films Formed on AISI 316L Steel in Simulated BWR Conditions during SSRT
Authors: Takeda Yo-ichi , Bojinov M. , Hänninen Hannu , Kinnunen P. , Laitinen T. , Mäkelä K. , Saario T. , Sakaguchi K. , Shoji Tetsuo , Sirkiä P. , Toivonen A.
Published: March 2009

A possible approach to describe the role of the environment in the phenomena behind crack initiation and crack propagation in stress corrosion cracking (SCC) is to assume that the transport of species through the oxide film on the material surface is one of the rate-controlling factors. The transport rates of ionic and electronic defects through the oxide film are, in addition to the environment,
also affected by the stress and strain applied to the bulk material.
In this paper, the surface oxide film formed on AISI 316L steel in slow strain rate tests (SSRT) in simulated BWR condition has been analyzed by using Electron Spectroscopy for Chemical Analysis (ESCA). The obtained film composition and structure have been combined with in-situ contact electric resistance (CER) measurements in order to evaluate the changes in oxide film electric properties during straining in the above environment. The results show that oxide film resistance of the strained part exhibits a maximum at around 2% of strain, which seems to correlate with a maximum in the Cr(III) concentration in the inner layer of the oxide. The implications of these results to SCC are discussed based on Mixed-Conduction Model (MCM).
The Analysis of Hydrogen Diffusion under Heat Transfer Condition around the Heat Affected Zone of Welding
Authors: Takei K. , Yokobori Jr. A.Toshimitsu
Published: March 2009

Hydrogen embrittlement causes a crack initiation and brittle fracture. Therefore, it is important to conduct theoretical analysis to predict hydrogen distribution on the basis of reasonable physical model. In this paper, numerical analysis on the hydrogen diffusion and concentration at the localized stress field was conducted to clarify the behavior of hydrogen concentration and the sensitivity of hydrogen embrittlement. Furthermore, on the basis of this analysis, the effect of post weld heat treatment on the release of concentrated hydrogen was analyzed and optimum condition of post and pre heat treatment on the welding was investigated.
Effects of Co2O3 on the Dielectric Properties of Mg2TiO4- Mg2SiO4 Microwave Ceramics
Authors: Li Ling Xia , Sun Xiao Dong , Wu Xia Wan
Published: March 2009

Effect of Co2O3 on microstructure and dielectric properties of Mg2TiO4-Mg2SiO4 microwave ceramic with low permittivity and high Q value was studied. Co2O3 acts and results in decreasing of the sintering temperature and densification of the ceramic material. As a result, the dielectric loss decreases and quality factor Q increases. Mg2+ is replaced partially with Co2+ in Mg2TiO4 to form (Mg,Co)2TiO4. It is demonstrated that the system with 2.4 wt% Co2O3 possesses better dielectric properties.
Synthesis of Calcium Phosphate/Gypsum Composite Powders
Authors: Yang De An , Yang Zi , Hu Weijie , Li Yuan Yuan , Wang Huan
Published: March 2009

Gypsum powders and calcium phosphate/gypsum powders were synthesized by wet method. The influences of the pH and temperature on the morphology of the gypsum crystal were studied by light microscopy. The effects of the initial calcium/phosphorus molar ratio and the pH of the solution on the microstructure and phase composition of the calcium phosphate/gypsum composite powders were studied by scanning electron microscopy and X-ray diffractometry. The results show that both temperature and pH value had influence on the crystal shape of gypsum and the pH value was the predominant parameter for the particle shape and phase composition of the composite powders.
The Mechanical Properties and Microstructures of Cement Formed from Pyrophosphoric and Orthophosphoric Acids
Authors: Grover Liam M. , Gbureck Uwe , Farrar David , Barralet J.E.
Published: March 2009

In this study the setting times, compressive strengths and microstructures of cements formed using pyrophosphoric acid solution and b-tricalcium phosphate (β-TCP; Ca3(PO4)2) were compared with those of cement formed using orthophosphoric acid solution and b-TCP. It was found that cement formed using pyrophosphoric acid solution set more slowly than that formed using orthophosphoric acid and could be mixed to a higher powder to liquid ratio, facilitating the production of cement exhibiting compressive strengths, without pre-compaction, as high as 25 MPa. The use of pyrophosphoric acid as opposed to orthophosphoric acid resulted in a marked change in the microstructure of the cement.
Increased Bone Ingrowth on a Biomimetic Nanocrystalline Apatite Surface
Authors: Hermida Juan C. , Yang Xiaofan , Li Pan Jian , Patil Shantanu , Colwell Clifford W. , D'Lima Darryl D.
Published: March 2009

Typical plasma-sprayed hydroxyapatite coatings work well on non-porous substrates but do not coat the inner surfaces of open-porous substrates. Solution deposition can produce consistent bioceramic coats of precise thickness on porous surfaces. The resultant “biomimetic” surface more closely mimics the trabecular pattern and biochemistry at the bone interface. This report compares bone response to porous surfaces with biomimetic hydroxyapatite coatings. Implants were
manufactured as Ti6Al4V cylinders (5-mm diameter, 41-mm long) coated with c.p-Ti PorocoatÒ porous layer with a thickness of 750 (± 250 µm). Implants were divided into three groups based on surface treatments. The porous surfaces of control group implants did not receive any treatment. The porous surfaces of HA group implants were plasma sprayed with hydroxyapatite. The porous surfaces of BAp group implants were coated with a biomimetic apatite (BAp) coating using a lowtemperature solution-based process that mimics bone mineralization. BAp coating is pure apatite coating of uniform structure and composition, with a thickness of approximately 15 µm on the outer beads. Because of the reduced thickness, the BAp coating does not block the pores or alter the
porous structure. Bilateral femurs in thirty-six rabbits were implanted with one of the above groups. Twelve rabbits each were euthanized at 2, 4, and 12 weeks. Osseointegration was measured by automated computerized histomorphometry of scanning electron microscopy images of sections taken through the implant. Bone ingrowth on the Control surface was 45 % at 2 weeks and 47% at 12 weeks. Bone ingrowth on the PS surface increased from 51% at 2 weeks to 67% at 12 weeks.
Bone ingrowth on the BAp surface increased from 45 % at 2 weeks to 71% at 12 weeks. At both time points mean bone ingrowth on PS and BAp coated implants was significantly higher than the control uncoated implants (p < 0.01). By 12 weeks the PS hydroxyapatite coat began showing evidence of fragmentation and debris production on SEM. This was not evident in the BAp coat. This study supports the hypothesis that apatite coating benefits osseointegration. A biomimetic coat
of solution deposited apatite may not show the disadvantages of coating delamination and particle generation. Biomimetic apatite coatings may be attractive alternatives for noncemented total hip arthroplasty.
A Study to the Surface Characteristics of RF Magnetron Sputtered Bioglass - and Calcium Phosphate Coatings
Authors: Wolke Joop G.C. , Vandenbulcke E. , van Oirschot B. , Jansen John A.
Published: March 2009

The RF magnetron sputter technique was used to deposit Bioglass (BG) and
hydroxyapatite (HA) coatings onto titanium substrates. In the current study, the physico-chemical and dissolution properties of various deposited coatings were investigated. X-ray diffraction demonstrated that the as-sputtered coatings had an amorphous structure, a heattreatment for 2 hours at 600°C changed only the HA coating into a crystalline apatite structure. Dissolution experiments demonstrated that all the amorphous coatings dissolved during the incubation for 4 weeks in simulated body fluid, while all the heattreated sputter coatings were still maintained. In contrast with the HA heattreated sputter coatings all the bioglass containing sputter coatings showed the formation of a crystalline apatite phase. Scanning electron microscopical examination of the sputtered coatings demonstrated that on all the heattreated BG/HG sputter coating a thick CaP precipitate was formed, while on the BG sputter coating occasionally a globular precipitate was observed.
In Vivo and In Vitro Studies on the Bioactivity of Anodic Oxidized Titanium Metal
Authors: Wu Yao , Yang Bang Cheng , Chen Ji Yong , Zhang Xing Dong
Published: March 2009

In this study, the bioactivity of a new kind of anodic oxidized titanium metal was
investigated in vitro and in vivo. After immersed in SBF solution for 7 days in vitro, apatite formed and covered almost all the surfaces of the anodic oxidized samples. In vivo animal experiment, the apatite was also tested precipitated on the interface of tissue/materials after 12 weeks post-operation, and there were no any fibrous capsule formed around the materials. The materials bonded with the bone very tightly and attached to the skin very closely, which would result in the achievement of the biological sealing for the bone-anchored percutaneous implants. These positive results might be contributed to the precipitated apatite layer formed on the surface of the bioactive oxidized titanium. Thus, Anodic oxidation treatment might be an effective way to prepare bioactive Ti both for bone replacement and percutaneous implant.
Mechanical Properties and Osteoconductivity of Porous Bioactive Titanium Metal
Authors: Takemoto Mitsuru , Fujibayashi Shunsuke , Matsushita Tomiharu , Suzuki J. , Kokubo Tadashi , Nakamura Takashi
Published: March 2009

Porous bioactive titanium implant was produced by plasma-spray method and succeeding chemical and thermal treatment. This porous titanium implant possess a porosity of 40% and complex interconnective porous structure. Mechanical property of porous titanium was characterized for compressive and 4-point bending properties, as well as compressive fatigue. Bone tissue response and biocompatibility of porous bioactive titanium implant was evaluated by in vivo osteoconductive model. Ultimate compression strength and bending strength were 280 and 101 MPa. Bone ingrowth showed significant increases in treated implant, while in these untreated porous titanium implant, bone ingrowth seemed to decrease with time. These results suggest that porous bioactive titanium is a candidate for clinical applications under load-bearing conditions.
Experimental Study on the Osteoinduction of Calcium Phosphate Biomaterials In Vivo and the Capability of Supporting Osteoblast Proliferation In Vitro
Authors: Bao C.Y. , Li P. , Tan Yan Fei , Cao Y. , Ling X.Y , Deng Chun Lin , Li Xu Dong , Chen W.C. , Fan Hong Song , Zhang Xing Dong
Published: March 2009

The purpose of this study was to evaluate the response of osteoblasts to the calcium phosphate with different surface modification, and to evaluate the osteoinductive capabilities of these biomaterials. 60HA/40α-TCP ceramics sintered at 1250oC was applied in this study. The ceramic cylinder with F5mm×8mm and slice with F10mm×1mm were prepared respectively. One thirds of the ceramics were formed bone-like apatite (BLA), and the surface of another one thirds was modified with collagen. Osteoblasts (1×106/ml) were co-cultured with the three kinds of thin slices for 12h, 24h and 48h. SEM observation was applied to evaluate if the surface modification and BLA formation could affect the attachment and proliferation of osteoblast in vitro. The three kinds of cylinder samples were implanted in dog muscle to evaluate their differences in osteoinduction. Cells grew in
multi-layers and well attached to the surface and proliferated well in the group of collagen and HA/TCP. In untreated and BLA precipitated group, cells did not attach to the surface well. Osteoinduction was good in BLA precipitated group and the amount of bone formed was higher; in untreated group and collagen-treated group, no bone formation was observed in the tested period. This result indicated that the scaffold used in cell-materials composites in vitro and that in osteoinductive material based tissue engineering in vivo was not same.
Micro-Spectrometric Investigations of Inorganic Components of the Black Corals for Biomedical Applications
Authors: Nowak Dorota , Florek M. , Nowak J. , Kwiatek Wojciech , Lekki Janusz , Zięba E. , Romero P.G. , Ben-Nissan Besim , Kuczumow A.
Published: March 2009

The distribution of about twenty inorganic elements was traced in the skeletons of black corals of the Antipathes salix species. Electron microprobe and PIXE mappings revealed the peculiar structure of this material, composed of the large cells (arranged in annual rings), surrounded by thin layers with an elevated
level of iodine (up to 5%). Our current knowledge of the chemical composition of these corals’ skeleton is not complete. Essentially the organic skeleton is saturated with inorganic elements and several of these could be commercially important. In fact, they have never been investigated for biomedical applications. In
this preliminary current work, black corals from the Antipathes salix species were studied with the aim of detecting the inorganic components of their matrix and their suitability as biomedical materials.
Cytocompatibility Studies of a Novel Bioactive Glass Coated Porous Hydroxyapatite Bioceramic for Use as a Bone Substitute
Authors: John A. , Varma H.K. , Kumari T.V. , Nisha V.R. , Narayanan D.
Published: March 2009

Cytotoxicity and cytofunctionality of the in-house prepared novel bioactive glass coated hydroxyapatite (BGHA) is described here as a first step in characterizing the biocompatibility of the material for orthopaedic application. Sintered hydroxyapatite was coated with bioactive glass by a sol-gel method. The BGHA granule was 2 - 4 mm in size with a pore size in the range of 50 – 150
µm. FT-IR spectrum depicted the functional groups and XRD spectrum defined the crystallinity of the material. MTT assay proved high cellular activity and morphologically the cells showed normal proliferation with the expression of actin and vimentin network in the cytoplasm. In the resin sections, cells were found located on the walls of the pores while in osteoblast-cultured granules, cellular matrix was also observed along the pore interconnections. Recrystallization on the surface of the cultured granules did not support the adhesion of cells. The electron diffraction pattern displayed the high crystallinity of the raw granule while a diffused pattern of amorphous apatite like crystallites was observed for the cultured granules. High calcium and low phosphorous concentration was observed in the medium of the cells simultaneously with ALP and osteocalcin production. This pre-clinical evaluation proved BGHA, as a promising material for bone scaffolds.
Cathodoluminescence as a Method of Microstructure Characterization of Biphasic Ceramics Composed of Hydroxyapatite and β-Tricalcium Phosphate
Authors: Diggs A.B. , Halloran J.W. , Hollister S.J.
Published: March 2009

This paper describes the investigation into the use of cathodoluminescence for
distinguishing HA and β-TCP phases within the biphasic calcium phosphate ceramic
microstructure. Polished samples were scanned using SEM-CL at an accelerating voltage in the range of 10-15 keV with a beam current of 5-10 nA. The grayscale images produced reveal distinctive patterns for each composition. EDS and EPMA suggest chemical differences among the contrasting regions. Image analysis of voxel values indicate that areas of bright contrast correspond to β-TCP grains with phase amounts confirmed by XRD.
Hydroxyapatite Foams for Bone Replacement
Authors: Ranito Cláudia M.S. , Oliveira Fernando A. Costa , Borges João Paulo
Published: March 2009

Hydroxyapatite, often in the form of synthetic porous blocks, has been used in the repair of bone defects for over 20 years owing to its biocompatibility and osseoconductive behaviour.
Bone ingrowth requires the existence of open and interconnected pores with diameters larger than 150 µm for proper circulation of nutrients. Hence, currently available materials are characterised by poor mechanical properties. Collapse of such products is therefore a major source of concern to surgeons using these weak materials in bone surgery. There is a need to develop stronger highly
porous structures through adequate control over the size, shape and volume fraction of pores. In this work, highly porous open-cell hydroxyapatite foams were fabricated by the polymer foam replication process, where two types of polyurethane (PU) foams were infiltrated with optimised slurries containing appropriate binders and ceramic particles, followed by the removal of excess
slurry, burning out of the polymer to leave a ceramic replica of the polyurethane and finally high temperature sintering. Open-cell HAP foams with porosities of about 80% were obtained, i.e. 30% higher than that determined for commercial ones (50%). Many of the commercial foam cells approach 500 µm in diameter whereas the developed foam cell size ranged from 300 up to 500 µm.
The ultimate compressive strength of the developed foams (1-2 MPa) was found to be higher than that recorded for the commercial ones (0.7 MPa) indicating that these foams can more easily be modelled in theatre. Both the elastic moduli and the compressive strength of the developed foams were found to increase with increasing of the relative density, in accordance with the predictions of available micro-mechanical models.
Calcium Phosphate Open Porous Scaffold Bioceramics
Authors: Gittings J.P. , Turner I.G. , Miles A.W.
Published: March 2009

Calcium phosphate (CaP) ceramics possessing an interconnecting porosity network in the appropriate size range for vascularisation offer the possibility of providing a structural matrix for replacement of diseased or damaged bone. Such bioceramics must possess sufficient mechanical strength to avoid failure whilst offering a bioactive surface for bone regeneration. The objective of the current study was to produce a hydroxyapatite/tricalcium phosphate (HA/TCP) bioceramic that imitated the orientated trabecular structure found in cancellous bone. The structure-property relationship of these bioceramics was then analysed. It was hypothesised that the mechanical properties would be linked to the shape of the pore structure due to the orientation of the open porous scaffolds (OPS) produced. OPS bioceramics possessed an interconnected macroporosity
network of 40-70% by volume with bending strengths of 0.30MPa ± 0.01MPa and apparent densities of 0.35g/cm3 ± 0.05g/cm3. Typically, pore sizes in the range of 150-300µm were produced. The fabrication of CaP OPS resulted in a wide range of macroporosity in the correct size range for osseointegration to occur. Elongating the pore structure did not affect the total porosity of the bioceramics. Strengths were low due to microcrack formation on sintering and not due to the shape of the pores present in the scaffold as initially hypothesised.
The Effect of Hydroxyapatite on the Remineralization of Dental Fissure Sealant
Authors: Park S.W. , Lee Yong Keun , Kim Yeon Ung , Kim Min Chul , Kim Kyoung Nam , Choi B.J. , Choi H.J.
Published: March 2009

The purpose of this study is to investigate the remineralization of enamel in the human tooth by fissure sealant containing various amount of hydroxyapatite. Prior to remineralization experiments, the necessary requirements of the dental fissure sealant, the curing depth and the curing time, were measured with the content of the hydroxyapatite according to the standard of ISO 6874.
Various amount of hydroxyapatite was mixed uniformly using sonicator up to 20 wt% to the fissure sealant. In spite both the curing time and the curing depth were decreased with increasing the content of hydroxyapatite, all samples were satisfied the ISO requirements. Remineralization experimental samples were produced by bonding fissure sealant containing various amount of hydroxyapatite to human tooth enamel using manufacturer’s information. After exposure to the simulated body fluid at 36.5oC for 4 weeks, the bonding strength and the surface morphology were examined using Instron and scanning electronic microscope, respectively. The bonding strength between the fissure sealant and the human teeth was drastically enhanced with the amount of hydroxyapatite. The remineralization zone could be observed along with the boundary of hydroxyapatite and fissure sealant using a scanning electronic microscope.
SEM/EDX and FTIR Characterization of a Dental Resin Cement with Antibacterial Agents Incorporated
Authors: Akaki Emílio , Mansur Herman S. , Angelis Lúcia H. , Castro Barbara A. , Valadão Henrique F. , Faria Danielle B. , Rezende Fernanda C.
Published: March 2009

The demand from patients for aesthetic in posterior teeth restoration has been increasing in recent years. As an alternative to metal alloy restorations used in posterior tooth, aesthetical materials such as ceramics have been more often utilized. Resin cement, a derivative from dental composite, based on the combination of bis-GMA and inorganic filler is used to fixate these ceramic restorations to posterior teeth. Similar to resin composite, incorporated antibacterial agents to resin
cement can be an effective way to increase the aesthetic restoration durability. Resin cements C&B® (Bisco) and Fill Magic Dual Cement® (Vigodent) were used in the present study. For experimental resin cement, Triclosan was incorporated to the base cement paste. Samples were investigated by Scanning Electron Microscopy coupled to EDX microprobe (SEM/EDX) and FTIR
spectroscopy. The results have demonstrated that the incorporation of antibacterial agents to resin cement is possible through the developed procedure.
Porous HA Scaffolds for Drug Releasing
Authors: Queiroz A.C. , Santos José D. , Monteiro F.J.
Published: March 2009

Dense and porous hydroxyapatite materials aimed at being used in controlled drug
delivery, were characterised and studied in order to evaluate their ability to adsorb and release sodium ampicillin in a controlled manner, as a model for a drug delivery system, potentially applicable associated to surgery for the treatment of bone defects. These porous materials should also have adequate mechanical strength to withstand manipulation and sculpturing in surgery room. Adsorption and release profiles were obtained for a range of porous materials, leading to higher
adsorption rates and more adequate release profiles than for dense materials.
Study of In Situ Apatite Formation on Bioactive Substrates Using Confocal Microscopy
Authors: Akhshi M. , Huang Jie , Best Serena , Farrar David , Rose John , Bonfield William
Published: March 2009

This paper describes the use of confocal microscopy as a new method for in situ analysis of the apatite layer which forms on bioactive substrates after immersion in a simulated body fluid (SBF). Conventional methods such as secondary electron microscopy (SEM) require drying and coating of the samples. This approach causes damage to the structure of the apatite layer of which a common example is surface cracking. With confocal microscopy samples are examined in situ and
build a unique optical sectioning of the samples. As shown in this paper, using these sections, a clear image can be constructed of the reactive layer which forms on a sample both in horizontal and vertical cross-sections.
Resorbable Biomaterials Based on Calcium Phosphates: Determination of In Vitro Solubility Applying the ISO 10993-14 (First Experiences)
Authors: Ploska Ute , Gildenhaar Renate , Berger Georg
Published: March 2009

To guarantee of the security of ceramic medical products the identification and
quantification of the current degradation products is required by the ISO 10993-14 standard. Two methods - the gravimetrical registration of the mass loss and the quantitative determination of the leached ions by spectrometric methods - are planned. When checking the application of the ISO standard to calcium phosphate ceramics that can be used as implant materials a considerable difference in the results obtained with both methods was observed. It seems to be that precipitation
reactions are responsible for that situation. To clear up the influence of precipitation reactions on the results the working procedure of the ISO standard was slightly modified. A first interpretation of the results is tried.
Glutamate Release by Osteoblasts in the Presence of Ionic Products from Bioactive Glass 60S
Authors: Valério Patricia , Mendes C.C.P. , Pereira Marivalda , Goes Alfredo , Leite M. Fatima
Published: March 2009

Osteoblasts constitutively release glutamate and this release appears to be regulated by calcium entry. In this work we investigated if the bioactive glass with 60% of silicon (BG60S) could alter glutamate release by osteoblasts. We demonstrated that osteoblasts incubated with medium containing ionic products from the dissolution of BG60S showed lower release of glutamate when compared to control. Since intracellular calcium (Cai 2+) increase is required for glutamate release we investigated the subcellular distribution of the calcium channel inositol
triphosphate receptors (InsP3Rs) in the presence of BG60S compared to control. We found that the type-III InsP3R was not expressed in osteoblast, while the type-II InsP3R was expressed mainly in the cytosol. We also found that the expression of type-II InsP3R decreased in BG60S treated osteoblasts compared to control. On the other hand, we found that the type-I InsP3R was expressed
mainly in the nucleus and its expression increased in the presence of the biomaterial.
Synthesis and Characterisation of Hydroxyapatite Nano-Rods/Whiskers
Authors: Kumar R. Roop , Prakash K.H. , Yennie K. , Cheang P. , Khor Khiam Aik
Published: March 2009

The use of precipitation chemistry to synthesize hydroxyapatite (HA) normally yields nano-crystals with various morphology and sizes depending on the synthesis conditions (e.g., temperature, concentration, level of agitation, pH, etc.). This study involved the synthesis of HA nano-rods/whiskers by modifying an existing chemical route for HA synthesis. The nano-rods were characterised for their structure and morphology and subsequently sintered. The mechanical properties of the sintered compacts were also assessed.
Incorporation of Human Osteoblast Cells and Osteoblast-Like Cells into Porous Hydroxyapatite Scaffolds
Authors: Arumugam Meera Q. , Brooks Roger A. , Rushton Neil , Bonfield William
Published: March 2009

The object of this study was to investigate methods of seeding cells onto porous hydroxyapatite granules with the aim of optimising cell attachment. Two cells types were used; an osteosarcoma cell line, MG63, and human osteoblasts (HOBs) isolated from trabecular bone. Several conditions were investigated to determine their effect on cell attachment. These included varying the initial seeding concentration, pre-adsorption of the granules with the adhesion protein fibronectin and the use of mechanical agitation. Human osteoblasts and MG63 osteosarcoma cells attached to both dense and porous HA granules but with a low seeding efficiency while seeding was not significantly improved by pre-coating scaffolds with fibronectin or by introducing fluid flow.
Effects of Cyclic RGD Peptide Functionalization on the Quantitative Bone Ingrowth Process in Cellularized Biphasic Calcium Phosphate Ceramics
Authors: Fricain Jean Christophe , Pothuaud L. , Durrieu M.C. , Pallu S. , Bareille Reiner , Renard M. , Jeanfils J. , Dard M. , Amédée J.
Published: March 2009

The aim of this study was to evaluate the in vivo effects of the grafting of cyclo-
DfKRG on the early phase of integration of biomaterials made with macroporous hydroxyapatite/b-tricalcium phosphate colonized with autologous bone marrow stromal cells. Non-grafted (-RGD) and grafted (+RGD) biomaterials were implanted in both femoral condyles of rabbits for 2 and 4 weeks. Two weeks after implantation, the global bone formation was higher with +RGD samples (p=0.02). There remained no significant difference 4 weeks after implantation. In conclusion,
grafting of cyclo-DfKRG peptide on materials could promote cell colonization and improve osteoconduction during the first stage of the bone cicatrization process.
The Study of the Frequency of Medium Changing in the Fabricating Tissue-Engineered Bone
Authors: Miyazaki Kazuhide , Yoshikawa Takafumi , Iida Jin , Ueda Y. , Koizumi M. , Takakura Yoshinori
Published: March 2009

Marrow mesenchymal cells contain stem cells and can regenerate tissue. We previously reported the clinical application of autologous cultured bone to regeneration therapy. However there is room for improvement in the culture methods; and here, we examined the optimal frequency of medium changing. Marrow cells were collected from the femur of a Fisher 7 week-old male rat. At 2
weeks after primary culture in a standard medium (MEM containing 15% bovine fetal serum), the cultures were trypsinized to prepare a cell suspension and divided into two groups, with or without addition of dexamethasone (Dex) to the osteogenic medium. To investigate optimal frequency, we further divided into 5 sub-groups; no changing (M0), 1 time/week (M1), 2/week (M2), 3/week (M3),
and everyday (M7). After 2 weeks of subculture, the tissue was harvested and then ALP activity and calcium and DNA contents measured. In both of the Dex groups, there was significantly high ALP activity in the higher frequency group; but there was no significant DNA content. Also, in the Dex(+)group, there was a significant increase of calcium content in only the M3 and M7 sub-groups. Thus,
we showed that the osteogenic potential of cultured bone is cultivated by increasing the frequency of medium changing.
In Vitro Osteogenic Activity of Rat Mesenchymal Cells Cultured on Transparent β-Tricalcium Phosphate Ceramics
Authors: Kotobuki Noriko , Ioku Koji , Kawagoe Daisuke , Nomura Daishiro , Fujimori Hirotaka , Goto Seishi , Ohgushi Hajime
Published: March 2009

We have cultured mesenchymal cells (MSC) on various types of ceramic disks and used these tissue-engineered ceramics for hard tissue regeneration. In this approach, observation of cultured cell morphology is important even if culture substrata are calcium phosphate ceramics, which usually show bioactive nature. However, due to the opaque nature of the ceramics, cells observation is very difficult. Here, we demonstrate light microscopic observation of rat MSC cultured
on transparent β-tricalcium phosphate ceramics (β-TCP). The culture was performed in osteogenic medium. Thus, the cell differentiated into bone-forming osteoblasts, which fabricated a mineralized matrix on the ceramic disks. Microscopic observation revealed that the cascade of osteogenic differentiation after attachment/proliferation of MSC on the ceramic disks was similar to that on a
culture grade polystyrene dish. These results confirmed the excellent property of β-TCP for MSC culture leading to hard tissue regeneration.
Competing Damage Modes in All-Ceramic Crowns: Fatigue and Lifetime
Authors: Zhang Yu , Lawn Brian R.
Published: March 2009

A study is made of fracture from cyclic loading of WC spheres on the surfaces of
brittle layers on compliant substrates, as representative of repetitive occlusal contact on dental crowns. Several damage modes—radial cracks at both top surface and cementation interface, and classical cone cracks as well as deep penetrating cone cracks from the top surface—have been identified and analyzed. The most dangerous fractures are radial cracks that initiate from either the top or bottom surfaces of the brittle layers and spread laterally to failure. In fatigue, these cracks are driven by chemical forces associated with the intrusion of water into the crack. Also dangerous are deep penetrating cone cracks which, unlike their
classical cone crack counterparts, are mechanically driven by hydraulic pumping and can evolve rapidly with cyclic loading, threatening the lifetime of a dental crown veneer.
Amorphous Calcium Phosphates (ACP): Formation and Stability
Authors: LeGeros Racquel Z. , Mijares Dindo Q. , Park J. , Chang X.-F. , Khairoun I. , Kijkowska Regina , Dias Renata , LeGeros John P.
Published: March 2009

Our earlier studies showed that several ions inhibit the crystal growth of apatite and
promote the formation of amorphous calcium phosphates (ACP). These ions include: magnesium (Mg), zinc (Zn), stannous (Sn), ferrous (Fe), carbonate (CO3), pyrophosphate (P2O7). The purpose of this study was to investigate the effect of combination of these ions (e.g., Mg & CO3, Mg &
P2O7, Mg & Zn, etc) on the formation and stability of ACP. ACP compounds containing the different ions were prepared at 25 and 37oC according to the method we previously described. Chemical stability was investigated by suspending the different ACP preparations in solutions with or without inhibitory ions. Thermal stability was determined by sintering the ACP at different temperatures. Dissolution properties were determined in acidic buffer. The ACP before and after chemical or thermal treatment were analyzed using X-ray diffraction, infrared spectroscopy, and
thermogravimetry. Results showed synergistic effects of inhibitory ions on the formation of ACP. ACP materials, regardless of their composition, remained amorphous even after heat treatment at 400oC. Transformation of ACP to other calcium phosphate phases depended on the pH and on the solution composition.