bluuebunny/crossref_metadata_2025 huggingface dataset:
Examination of the Optimal Local Model Size in the Three-Dimensional Local Hybrid Method
Authors: Machida Kenji , Ueno Takanori , Oyama Hirohisa
Published: March 2009

The interior stress field of the surface crack specimen subjected to a uniform tensile load
has been successfully analyzed by the 3-D local hybrid method. In this study, it was examined
whether the 3-D local hybrid method was applicable to the specimen subjected to the bending load.
It has been understood that the decision of the optimal size of the local model is indispensable in the
improvement of accuracy from the previous research. Then, the width and thickness of the local
model were changed widely, and analyses were carried out to find the optimal hybrid local model
size. Moreover, it was examined how to decide the optimal size of the hybrid local model with
various crack length and aspect ratio of the specimen. The optimal size of the hybrid local model
was examined from the comparison with the J integral of the whole model.
A Comparative Study on the Fatigue Evaluation for Weldments under Out-of Plane Bending Load Using Structural Stress and Hot Spot Stress
Authors: Kim Myung Hyun , Ha Chung In , Kang Sung Won , Kim Jeong Hwan , Lee Jae Myung
Published: March 2009

Fatigue strength assessments with two types of load carrying fillet weldment under out-of-plane
bending load have been carried out by using both hot spot stress and structural stress methods. Basis for the
derivation of structural stress method is discussed in detail. Finite element analyses using shell elements models
have been performed for the fatigue strength assessment of weldments. As a result of the fatigue strength
evaluation for load carrying transverse fillet weldment, hot spot stress method is found to be consistent with
structural stress method as well as measurement. Hot spot stress, however, estimated for the load carrying
longitudinal fillet weldment exhibit large variation with respect to mesh size and element type while the
calculated structural stress for the longitudinal fillet weldment is relatively independent of mesh size. The
fatigue life estimation according to structural stress has been introduced with the master S-N curve.
Investigation of Thermo-Chemical Polishing of CVD Diamond Film
Authors: Chou Wen Chen , Chao Choung Lii , Chien Hsi Hsin , Ma Kung Jeng , Lin Hung Yi
Published: March 2009

ZnO/Diamond structure has attracted a lot of attentions and heavy investment recently just because diamond has the capability of producing very high surface acoustic wave (around 10,000m/s). In this present study, the microwave chemical vapor deposition (CVD) method was employed to produce diamond films on silicon single crystal. Thermo-chemical polishing experiments were then conducted on the obtained diamond films. The underlying material removal mechanisms, microstructure of the machined surface and related machining conditions were also investigated. Thermo-chemical polishing was proved to be able to remove the diamond film very effectively (4.8μm deep of diamond film was removed in 30 minutes when polishing at 550oC and 5.7m/s). The material removal rate was increased with polishing speed and pressure. Higher polishing temperature would improve the chemical reaction and result in better surface finish.
Nano-Structures Fabrication by Laser Combined with Near-Field Scanning Optical Microscopy
Authors: Wu Dong Jiang , Zhuang Juan , Wang Xu Yue , Kang Ren Ke , Zhao Fu Ling
Published: March 2009

We have developed the laser nanoprocessing technique by the integration of the fs laser
and near-field scanning microscopy (NSOM). The second harmonic femtosecond laser working in
the optical near-field with the assistance of NSOM equipment was applied to expose the
photosensitive polymer material. The nanopatterns with feature size smaller than the laser
wavelength can be fabricated. The optical diffraction limitation is therefore broken through by the
near-field nanoprocessing. It was found in our experiment that the nanofabrication feature size
depends strongly on the gap between the fiber probe tip and the substrate surface, as well as the
laser coupling efficiency. The approach offers the advantages of high precision, speed and
selectivity in nanopatterning, and is promising to be used in data storage device manufacture for
higher density recording.
Innovated Precision Grinding by Exploiting Grinding Point Movement in Radial Direction and Forward Backward Feeding of Wheel
Authors: Yao Bin , Xi W.M. , Chen C.R. , Shi L.
Published: March 2009

A novel precision grinding technique optimum is proposed for grinding workpiece’s
convex surface. The grinding point moves in radial direction on wheel’s planar face, while the
grinding wheel feed in forward and backward direction. The calculation model of cutting location is
established, experiments and data are shown. The advantages are illustrated by achieved higher
precision grinding, extended life span of wheel, reduced deformation of machining system, and easier
dressed following dullness. Via comparing the machining error to conventional methods, it is
suggested that technique is an optimum option, in particular, for grinding convex surface of
workpiece made of brittle and hard materials.
Forming Fine V-Grooves on a Tungsten Carbide Workpiece with a PCD Electrode by EDM
Authors: Sano Sadao , Suzuki Kiyoshi , Pan Wei Li , Iwai Manabu , Murakami Yoshihiko , Uematsu Tetsutaro
Published: March 2009

Polycrystalline diamond (PCD) exhibits a thermal conductivity similar to that of the
electrically conductive chemical vapor deposition diamond (EC-CVD diamond) found to function as
zero-wear electrodes at short pulse duration. In this study, PCD was used as electrodes applied to
EDM on tungsten carbide. Two kinds of PCD (CTB-010 and CTH-025) with a flat surface were used.
The wear of the PCD electrodes was about 1.5% for very short pulse duration such as te=1μs, but it
was zero wear at te=30μs, though the wear of a Cu-W electrode was 10% even on the machine
recommended conditions for the low wear. EDM experiment using a V-shaped PCD electrode with an
included angle of 45° was also carried out and the performance was compared with the case using a
V-shaped Cu-W electrode. Under the conditions of a no load voltage of 60V, a set peak current of 2A,
and a medium pulse duration of te=15μs, there was no wear on PCD electrodes when observed under
the SEM, whereas a 50μm-deep wear on the Cu-W electrodes even under the machine recommended
condition for the low wear was observed.
Effect of Tool Flank Wear on the Orthogonal Cutting Process
Authors: Zhao X.L. , Tang Yong , Deng Wen Jun , Zhang F.Y.
Published: March 2009

A coupled thermoelastic-plastic plane-strain finite element model is developed to study
orthogonal cutting process with and without flank wear. The cutting process is simulated from the
initial to the steady-state of cutting force and cutting temperature, by incrementally advancing the
cutting tool forward. Automatic continuous remeshing is employed to achieve chip separation at the
tool tip regime. The effect of the degree of the flank wear on the cutting forces and temperature
fields is analyzed. With the flank wear increasing, the maximum cutting temperature values on the
workpiece and cutting tool increase rapidly and the distribution of temperature changes greatly. The
increase of tool flank wear produced slight increase in cutting forces but significant increase in
thrust forces.
Simulation of Burr Formation in Feed Direction in Turning
Authors: Toropov Andrey A. , Ko S.L.
Published: March 2009

The paper proposes a model of burr formation in feed direction during turning operation. Two cases
have been considered in the model: continuous and discontinuous burr development. A computer
program, made on the base of the model, allows simulation of burr development, and predicting
burr form and dimensions. Experimental verification of the program showed that the model is
suitable for the simulation of burr development in both continuous and discontinuous cases of burr
formation. The experiment also proved that burr thickness can be predicted with considerable
accuracy and that burr height can be determined with a maximum error of about 30%.
Novel Gene-Transferring System Using a Laminin-DNA-Apatite Composite Layer
Authors: Oyane Ayako , Tsurushima Hideo , Ito Atsuo
Published: March 2009

A laminin–DNA–apatite composite layer was successfully formed on the surface of an
ethylene–vinyl alcohol copolymer. The immobilized DNA was transferred to the cells adhering
onto the laminin–DNA–apatite composite layer more efficiently than those adhering onto a lamininfree
DNA–apatite composite layer. It is considered that laminin immobilized in the surface layer
enhances cell adhesion and spreading, and DNA locally released from the layer is effectively
transferred into the adhering cells, taking advantage of the large contact area. The present gene
transferring system, which shows high efficiency and safety, would be useful in gene therapy and
tissue engineering.
Protein Loaded Apatite Hydrogel and Protein Release from Its Cake
Authors: Yokogawa Yoshiyuki , Tagaki M. , Siotsu Y. , Watanabe Makoto
Published: March 2009

The time-dependent variation of the protein release from protein incorporated apatite
cake in PBS solution was studied. When protein incorporated apatite cakes were immersed in PBS,
the volume of cakes dropped for 1 day of soaking period and the shrinkage of specimen seems to be
stabilized after 2 or 3 days soaking in PBS. The quantity of released protein from protein
incorporated apatite cake was increased with an increase of soaking period. Around several % of
protein came from the protein incorporated apatite cake in PBS for 2 weeks. The time-dependent
protein release was relatively high for 1 day of soaking period, after that it slowly decreased.
Compared to the decrease in volume of cake, the quantity ratio of released protein and total
incorporated protein was less, which may be associated with recrystallization of the apatite hydrogel.
FE-SEM observation revealed both crystals formed in air or under N2 atmosphere had similar rod
like shape, and seems to be almost same in size. The change of surface appearance between 1 day
and 4 days or longer soaking may be due to the dissolution of the surface layer and its
recrystallization. The aggregate of apatite crystals formed in air is found to be compact, but some
small cavities are observed in the specimens soaked in PBS for 4 – 11 days. The particle size of
protein incorporated apatite were almost similar, independent on the soaking period. But the shape
of apatite in aqueous solution is changing from square and angular shape to round shape.
Effect of Ca/P Molar Ratio and Heat Treatment on Thermal Decomposition and Reconstitution of Hydroxyapatite
Authors: Zhu Qing Xia , Lv Ming , Wu Jian Qing
Published: March 2009

Stability of hydroxyapatite(HA) structure is influenced by preparation conditions and
afterwards heat treatment. In this paper, the powders with different Ca/P molar ratio were calcined
to investigate the influence of Ca/P and heat treatment on thermal decomposition and reconstitution
of HA. The results show that the Ca/P has little change even calcined at a high temperature of
1500°C. The Ca/P molar ratio close to 1.67 is beneficial to form high purity HA. HA gradually
releases its OH- ions in the temperature range of 800-1200°C. The decomposition takes place at
about 1200°C and will become more and more severe with the increase of temperature. Cooling
with slow rate and post-heat treatment in wet atmosphere are beneficial to both the rehydration and
the recovery of HA from the decomposition products (TTCP and α-TCP).
Influence of Abrasive Machining and Annealing on Hydrothermal Stability of Zirconia-Alumina Composites as a Hip Joint Head
Authors: Lim H.B. , Oh K.S. , Kwon Y.J. , Kim Y.K. , Lee Deuk Yong
Published: March 2009

Two tetragonal (t) zirconia-alumina composites were prepared by adding Al2O3 (20
vol%) into t-ZrO2 solid solutions doped with 3.0 mol% Y2O3, 1.6 mol% Nb2O5, 3.6 mol% CeO2
(Al20Ce) and 5.3 mol% Y2O3, 4.6 mol% Nb2O5 (Al20) as the femoral heads for the total hip
replacements. The effect of machining and annealing on the hydrothermal stability and surface
roughness of the composites was evaluated by comparing with the commercial 3 mol% Y2O3
stabilized t-ZrO2 (3Y-TZP). Machining was conducted by using the high-precision machine, where
the spindle speeds (rpm 9000~18000) and the electroplated wheels (#400, 800) can be easily
adjusted. The machined specimens were annealed at temperatures from 900 to 1300 oC and
subsequently autoclaved for 5 days at 120oC under 0.3 MPa water vapor pressure. Although the
phase stability and surface roughness of the machined composites were found to be inferior, the
hydrothermal stability of the annealed and subsequently autoclaved composites was determined to
be excellent as compared with that of the commercial 3Y-TZP. The lower phase stability of the
machined composites was likely to be due to numerous machining damages (surface defects) of the
composites than those of 3Y-TZP.
Corrosion Behaviour of ATZ and ZTA Ceramic
Authors: Begand Sabine , Oberbach Thomas , Glien Wilfried
Published: March 2009

The aim of this study was to record corrosion behaviour of ZTA and ATZ ceramics under
hydrothermal conditions and under influence of boiling acids. Ageing was performed for 30 h and
for 100 h in an autoclave at 134 °C and at a pressure of 2 bar. The sample surface was characterised
with the help of measurements of surface finish, strength and microhardness, as well as by means of
determination of wetting angle of contact. Leaching behaviour was analysed by means of scanning
electron micrographs and weightings. The results of all tests with ZTA and ATZ ceramics
performed in connection with this survey showed positive results, i.e. neither acid treatment nor
hydrothermal ageing resulted in significant changes of properties.
Osteolysis Associated with Polythene Liners in Hydroxyapatite Hip Arthroplasty
Authors: Buchanan James M.
Published: March 2009

Wear debris contributes to the development of granulomatous debris disease and loosening. It is accepted that hydroxyapatite ceramic (HA) will bond a prosthesis to bone.[1,2] Osteolysis has not been seen for several years after implantation but cases are now emerging [3]. Is HA still working? Should we use hard on hard bearings? Should we abandon polythene liners? With a modular hip system, patients with polythene acetabular liners have been compared with those with ceramic liners. Polythene liners wear out and patients with a life expectancy of more than ten years should have ceramic/ceramic bearings.
Crystallinity and Thermal Decomposition of Dialdehyde Celluloses from Bacterial Cellulose
Authors: Feng Yu Hong , Li Jia Cheng , Lin Qiang , Wang Xi Bin , Wu Zhou Xin , Pang Su Juan , Sun Zhong Liang
Published: March 2009

A series of dialdehyde cellulose samples with varied aldehyde content were prepared by oxidation of bacterial cellulose with sodium periodate. The X-ray diffractometry profile showed that the crystallinity degree of bacterial cellulose was 66%, but that of the dialdehyde cellulose (containing 12% aldehyde ) was 56%. Thermal decomposition of these dialdehyde cellulose samples and bacterial cellulose were studied by thermogravimetry. The decomposition of bacterial cellulose in nitrogen started at 230 and rapid weight loss occurred between 300-400. The introduction of dialdehyde group to bacterial cellulose resulted in significant shifts of decomposition to lower temperature range. The decomposition of dialdehyde cellulose (12% aldehyde ) started at 180 and rapid weight loss between 200-350. The temperature of rapidest weight loss shifted from 340 of bacterial cellulose to 290 of the dialdehyde cellulose(12% aldehyde).
Orthopedic Effects of Repelling Rare Earth Magnets on Craniofacial Sutures of Rhesus Monkeys
Authors: Zhao Ning , Shi Han , Xu Yun , Chen Yang Xi
Published: March 2009

The objectives of this study are to investigate the influence of class III orthopedic forces
generated by repelling rare earth magnets of class III magnetic orthopedic appliance (MOA-III) on
the zygmaticomaxillary suture of Rhesus monkeys. Six male Rhesus monkeys in the stage of mixed
dentition were used in this study. Fluorescent dyes were injected intravenously in each animal
before and during the experimental period. Distinct changes from physiologic growth remodeling
were observed in some sutures but not in the control groups. No inflammation was noted in both
experimental and control monkeys. The results show that MOA-III is a small intraoral appliance to
treat class III malocclusion, and the 300gm per side heavy orthopedic forces are safe and effective
for Rhesus monkey.
Hardness, Behavior and Metal Surface Evaluation of Recasting Non-Precious Dental Alloys
Authors: Ozyegin L.S. , Tuncer R. , Avci E.
Published: March 2009

Recasting of economic alloys can change several properties. The number of recasting
was found to have negligible effect on surface texture and on the amount of corrosion products
released. The methods and equipments utilized in the casting of an alloy are important on the
quality of casting. Carbon incorporated in a noble or economic alloy during casting is known to
affect the mechanical values of the metal. In the present study we aimed to investigate the change
in structure and metal hardness due to recasting. Materials and method: The effect of recasting, up
to four times of a non precious “Finalloy” commercial dental alloy on their Rocwell C hardness
behavior and their microstructures was inspected. Using “Kerr casting waxes” patterns were
prepared similar to the samples from “Finalloy”. The investments were pre-heated to phase at
temperatures between 900°C and 1000°C. The alloy was melted by an acetylene-oxygen flame in a
silicate crucible and four groups were compared: New alloy and alloys casted two, three, and four
times (n = 7). After casting, Brinell harnesses were recorded. Values of Rocwell C strength, for
each specimen group were analyzed by one-way analysis of variance, followed by the Student-
Newman-Keuls multiple range test. A metal microscope was used to evaluate the surface
morphology of the samples before hardness tests. 1st Casting :30.65 ± 0.3 kgf, 2nd Casting: 31.33 ±
0.4 kgf, 3rd Casting:34.80 ± 0.3 kgf, 4th Casting: 35.5 ± 28 kgf represents the Rocwell hardness of
the castings. The results showed that hardness, increased with repeated castings. The experimental
data indicates that increasing the number of successive recasting of “Finalloy” enhances the
Rocwell C hardness, thus, after remelting and recasting, the biological properties decreases.
Microscope study: Increase of the carbon content on the gren bounders of a cobalt-chromium alloy
causes a considerable change in its microstructure. The hardness and yield point for 0.05 %, 0.1 %
and 0.2 % tensile strength and elongation were determined for these test-pieces. The results showed
that hardness, yield points and tensile strength increased with increased carbon content, whereas the
elongation lessened. We determined that carbon concentrated at gren bounders. The clinical
importance of the study is that recasting affected the properties of the metal, for best biological
results with dental alloys always new metals must be used.
Effect of Particle Size on New Bone Formation In Vivo Using Calcium Phopshate Glass
Authors: Moon Hyun Ju , LeGeros Racquel Z. , Kim Kyoung Nam , Kim Kwang Mahn , Choi Seong Ho , Kim Chong Kwan , Lee Yong Keun
Published: March 2009

The purpose of this study was to compare the bone regenerative effect of calcium
phosphate glass according to the particle size in vivo. We prepared two different sizes, that is 400
μm and 40 μm, of calcium phosphate glass powder using the system CaO-CaF2-P2O5-MgO-ZnO.
Critical-sized calvarial defects were created in 60 male Sprague-Dawley rats. The animals were
divided into 3 groups of 20 animals each. Each defect was filled with a constant weight of 0.5 g
calcium phosphate glass powder mixed with saline. As controls, the defect was left empty. The rats
were sacrificed 2 or 8 weeks after postsurgery, and the results were evaluated using histological as
well as histomorphometrical studies. The particle size of the calcium phosphate was crucial; 400
μm particles promoted new bone formation, while 40 μm particles inhibited it because of severe
inflammation.
Comparison of Carbonate Hydroxyapatite with and without Sodium Co-Substitution
Authors: Stephen J.A. , Pace C. , Skakle J.M.S. , Gibson Iain R.
Published: March 2009

Carbonate hydroxyapatite (CHA) bioceramics can be synthesised to contain sodium ions
as a co-substituted ion, or as sodium-free compositions. It is unclear, however, which composition
would produce the optimum biological response. The aim of this study was to find a reliable
method to produce sodium co-substituted and sodium-free CHA compositions that would have the
same level of carbonate substitution, and to characterise the effects of the two different substitutions
on the structure of the CHA samples. After sintering at 900oC in a CO2 atmosphere, all samples
contained approximately equal amounts of carbonate groups on the A- and B-sites, as observed by
FTIR. The sample produced with NaHCO3 and the sodium-free sample (CHA1) have comparable
carbonate contents, whereas the sample produced with Na2CO3 contains significantly more
carbonate, probably due to the excess sodium ions allowing more carbonate co-substitution. The
sodium-free CHA sample, however, has significantly smaller unit cell parameters compared to both
sodium co-substituted CHA samples, and also to HA. This characterisation of the samples shows
that the sodium-free CHA sample (CHA1) and the sample produced with NaHCO3 would provide
CHA compositions for biological testing with similar carbonate contents and distributions, but with
structural differences due to the sodium substitution.
Dialysis Efficiency in Rapid Synthesis of Nano-Hydroxyapatite
Authors: Zhou W. , Zhang Sheng Min , Hu W. , Qiu Z.Y. , Liu Y.H.
Published: March 2009

In our previous work the nano-sized hydroxyapatite (nano-HAP) with uniform
morphology has been firstly synthesized by a wet chemical method based on dialysis, but the
dialysis efficiency was not investigated in detail. In this paper, the removal efficiency of impurity
ions such as NH4
+ and NO3
- was respectively evaluated by calculating the concentration of the
representative irons between the inner slurry and outer distilled water. Results showed that 99%
NO3
- ions and 96.9% NH4
+ - ions in the slurry has been eliminated. In the first dialysis time, the
NH4
+ ions diffuse faster than the NO3
- ions due to their smaller size. In the following dialysis times,
the dialysis efficiency of NO3
- ions is higher than that of the NH4
+ ions because of the presence of
higher NO3
- ions concentration gradient. The final nano-HAP is also characterized by XRD, TEM,
and FT-IR. It is revealed that the products are stick-like with a length of about 150nm and a
diameter of about 20-50 nm. Current work suggests that dialysis is an efficient purified method for
nano-HAP production and especially can be applied to industrial preparation of fine nano-sized
HAP powders.
Structural Properties of Hydroxyapatite With Particle Size Less Than 10 Nanometers
Authors: Rossi Antonella M. , Prado da Silva Marcelo Henrique , Ramirez Antonio J. , Biggemann D. , Caraballo M.M. , Mascarenhas Y.P. , Eon J.G. , Moure G.T.
Published: March 2009

Hydroxyapatite, HA, with crystal size smaller than 10 nm was synthesized by dropwise
addition of calcium nitrate and ammonium phosphate under controlled conditions. Powder was
composed by agglomerates of nano-particles with specific surface area higher than 200 m2/g. HA
samples had a main pore size distribution centered at 13-15 nm with a secondary mode centered at
3-5 nm. High resolution TEM revealed that individual particles had nearly spherical shapes and
were mainly composed of a crystalline core and an amorphous external component. EXAFS
measurements confirmed that the short range order of those HA nanocrystals was similar to that of
HA sintered at high temperature. HA powder with small particle size incorporates in its structure
more water and carbonate ions than HA prepared in normal conditions.
Remineralization Effect of the Nano-HA Toothpaste on Artificial Caries
Authors: Lv Kui Long , Zhang Jiu Xing , Meng Xiang Cai , Li Xing Yi
Published: March 2009

The aim of this study is to describe the remineralization effect of the nano-HA toothpaste on artificial caries. The artificial dental caries is made using sour solution. The demineralized teeth specimen is put into five kinds of toothpaste solution respectively for 5 days and 10 days, which are: solution of containing needle like nano-HA, solution of containing spherical nano-HA, solution of general HA, fluorine sodium solution and physiological saline. The hardness of specimen is measured and the surface morphology is characterized by SEM. The remineralized test indicates that the nano-HA toothpaste can enhance the hardness of artificial caries and improve the remineralization of artificial caries. The SEM analysis shows that the cavities and defects of enamel surface are decreased and many mineral salts are sedimentated, which indicate that the nano-HA could promote remineralization for the demineralized enamel.
Remineralization Potential of Sports Drink Containing Nano-Sized Hydroxyapatite
Authors: Lee H.J. , Min J.H. , Choi Choong Ho , Kwon H.G. , Kim B.I.
Published: March 2009

Several studies have reported the on dental erosive potential of sports drinks with a low
pH. Therefore, there is a need for new components that can reduce the erosive potential of a sports
drink. Hydroxyapatites (HA) are the major components of dental enamel and bone mineral as
biological apatites. In addition, HA contains a significant amount of calcium and phosphate, which
can promote remineralization. Hence, some remineralization of the enamel surface can be expected if
nano-sized hydroxyapatite (nano-HA) is added to a sports drink. The aim of this study was to evaluate
the remineralization effects of sports drinks containing nano-HA in vitro. The crowns of extracted
human molars were embedded in acrylic resin and then ground flat and polished. A commercially
available sports drink (Powerade, Coca-Cola, South Korea) was purchased from a local supermarket.
Nano-HA was added at a concentration of 0.05%, 0.25%, and 0.5%. Deionized water (DW) was used
as the negative control. The pH of each solution was measured by a pH-meter at room temperature.
The enamel specimens were immersed in each solution for 15 and 30 minutes at 37°C. In order to
evaluate remineralization effect, the VHN of the enamel surface was measured at every step by
microhardness test (JTTOSHI INC, Japan). CLSM and SEM were utilized to identify the change of
enamel surface. The pH of test solutions and VHN of enamel surface increased in proportion to the
nano-HA concentrations (P<0.05). The nano-HA could reduce the erosive potential of a sports drink
in a concentration dependent manner. These effects were confirmed by the CLSM and SEM images,
which showed the remineralization effect of nano-HA. However, more study will be needed to
examine the optimal concentration and remineralization mechanism of the nano-HA in sports drinks.
In conclusion, the addition of nano-HA to a sports drink can promote enamel remineralization.
Synthesis of Nanosized Carbonated Hydroxyapatite under Microwave Irradiation
Authors: Ran Xu , Chen Ji Yong , Ran Jun Guo , Guo Li , Zhang Xing Dong
Published: March 2009

In order to solve the problems on synthesizing carbonated hydroxyapatites (CHA) by the
conventional heating precipitation method, such as long reaction and large particle size, poor
crystallinity of CHA etc, the nanosized CHA particles have been synthesized by microwave heating
method using phosphoric acid (H3PO4), calcium hydroxide (Ca(OH)2) and calcium carbonate
(CaCO3 ) as starting materials in the present paper. The influences of power level and time of
microwave irradiation on synthesis of CHA have been investigated. The X-ray diffraction (XRD)
analysis has indicated that microwave heating will reduce CHA crystallization time and improve
crystallinity of CHA. Scanning electron microscope (SEM) analysis has showed that CHA particles
are of rod like morphology with about 60nm width and 200nm length respectively. Infrared
spectroscopy (IR) analysis has confirmed the B-type CHA precipitate can be formed under
microwave irradiation. The microwave irradiation plays an important role to promote the reaction
and the synthesis of nanosized CHA particles.
Dissolution of Hydroxyapatite Reinforced Grain Boundary by Glassy Phases
Authors: Youn Sang Heum , Yang Z. X. , Hwang Kyu Hong , Lee Jong Kook , Kim H.
Published: March 2009

Several sintering additives for hydroxyapatite have been tested in order to enhance its
sinterability without decomposing the hydroxyapatite(Ca10(PO4)6(OH)2) and without decreasing the
bioactivity and/or biocompatibility. In case of sintered pure hydroxyapatites significant dissolution
was occurred after immersion in distilled water or in simulated body fluid. At first the dissolution
was iniciated at grain boundary creating the nano-size defects such as small pores and grew up to
micro scale by increasing the immersion time. This dissolution resulted in grain separation at the
surfaces and finally in fracture. And the dissolution was concentrated on those grains adjacent to
pores rather than those in the dense region. So glass-reinforced hydroxyapatite(GR-HA) ceramics
were prepared to strengthening the grain boundary to prevent dissolution. Several glasses were
added at 0 to 10wt.% and sintered at 1200 °C for 2h in air with moisture protection. Glass phase
was incorporated into hydroxyapatite to act as the sintering aids followed by crystallization in order
to improve the mechanical properties without reducing the biocompatibility. From dissolution test,
significant damage was reduced even more than 7days. X-ray diffraction and SEM showed no
decomposition of hydroxyapatite to secondary phases and fracture toughness was increased more
than pure hydroxyapatite.
Studies on Non-Quenched Calcium Phosphate Cement: Influences of Quenching and Milling on Setting Characteristic
Authors: Wang Xue Jiang , Li Yu Bao , Jansen John A. , Li Shi Hong , Wolke Joop G.C.
Published: March 2009

The aim of this study is to explore the effects of quenching and milling processing on
setting property of calcium phosphate cement (CPC). For this purpose, non-quenched α-tricalcium
phosphate (α-TCP) and quenched α-TCP were synthesized and their corresponding cement systems
were prepared. The particle size of α-TCP powder was introduced as a variable. Then, setting
properties of these CPC systems were estimated. By a comparison between non-quenched CPC and
the quenched one, it is found that milling processing mainly influences the initial setting stage by
decreasing reactant particle size whereas the quenching treatment affects the final setting stage by
changing α-TCP content, which supports that CPC setting initially depends on the surface area of
reactants and subsequently on the diffusion through the hydrated layer formed around the reactants.
Electrospun PLLA/MWNTs/HA Hybrid Nanofiber Scaffolds and Their Potential in Dental Tissue Engineering
Authors: Deng Xu Liang , Xu M. M. , Li Dan , Sui Gang , Hu X. Y. , Yang Xiao Ping
Published: March 2009

Novel Poly(l-lactic acid) (PLLA)/ Multi-walled carbon nanotubes (MWNTs)/ hydroxyapatite (HA) nanofibrous scaffolds with high porosity and well-controlled pore architectures were prepared via electrospinning techniques. The structure, morphology, molecular weight change of the scaffolds were investigated using scanning electron microscopy (SEM). The results noticed that the average diameter of hybrid nanofiber was similar to that of PLLA/HA fiber, but the surface of hybrid fibers was much coarser because of the introduction of MWNTs nano-particles. The biocompatibility of the scaffold has been investigated by human Dental Pulp Stem Cells (DPSCs) cell culture on the scaffold. The preliminary results showed that cells were well adhered and proliferated on the hybrid scaffolds as well as PLLA/HA fibers. Based on the experimental observations, the aligned nanofibrous PLLA/ MWNTs /HA scaffold could be used as a potential candidate scaffold in dental tissue engineering.
Highly Bioactive Porous Composite Scaffolds of Bovine Hydroxyapatite (BHA-Ti, BHA-TiO2, BHA-Li2O)
Authors: Oktar Faik N. , Agathopoulos Simeon , Goller Gultekin , Gökçe H. , Kayali E.S. , Salman S.
Published: March 2009

Porous scaffolds of hydroxyapatite (HA), derived from calcined bovine bones and doped with various reinforcing materials, such as Ti, TiO2 and Li2O, were produced with the aid of commercial sugar, which was added as 20 wt% with respect to the total batch, and sintering at 1200°C and 1300°C. The samples were characterized by SEM and X-ray diffraction analysis as well as by porosity measurements. The experimental results showed that porosity can be controlled by the correct selection of doping materials. The optimum sintering temperature was 1200°C since firing at 1300°C caused extended sintering and thus porosity was considerably reduced. Matching of chemical nature as well as thermal expansion coefficients between HA and the doping components are of high importance for the structural integrity of the resultant scaffolds. Doping with Li2CO3 seemed to have the highest potential for achieving high porosity, likely due to the decomposition to Li2O, but the amount of Li2CO3 used should not jeopardizing HA bioactivity. The use of natural sugar is an economic way of producing safe for the health porous HA scaffolds.
Improvement of Microstructure of Bovine Hydroxyapatite (BHA) by Doping with Calcium Fluoride
Authors: Ozyegin L.S. , Oktar Faik N. , Agathopoulos Simeon , Salman S. , Bozkurt Y. , Eruslu Niyazi
Published: March 2009

Composites of calcinated bovine bone derived hydroxyapatite (BHA) doped 0.5 and 1 wt% CaF2 were prepared by sintering. The production of BHA from natural sources is preferred due to money and time saving reasons. Scanning electron microscopy (SEM) and X-ray diffraction analysis together with measurements of density and compression strength were carried out in the produced samples. The experimental results indicated that compression strength of the composites increase when sintering temperature increases. The best compression strength was achieved after sintering at 1200°C for 0.5% CaF2 addition. The results are in agreement with densification measurements and microstructure analysis. With regards to the amount of CaF2, the results indicate that small additions of F, lower than 0.5%, can further improve the mechanical properties of HA.
Spongiosa-like Specimen and Foils of a Biomaterial Composed of Fluorapatite and Calcium Zirconium Phosphate
Authors: Ploska Ute , Berger Georg
Published: March 2009

A long-term stable material, which has two main crystalline phases – fluorapatite (FA) and calcium zirconium phosphate (CZP) [1, 2] and could be processed to dense sintered samples was tested related to the use with two application forms – spongiosa-like specimen and foils. The suitability of various sintering additives was investigated alone and in diverse combinations. During sintering of the spongiosa-like samples volume shrinkage of about 50% was observed whereas the shrinkage in x,y plane was about twice of the shrinkage in z direction. The cuboid form was not affected by the shrinkage. The compression strength of the spongiosa-like materials was in the range of 1MPa up to 1.6MPa. A ceramic foil was generated via foil slip casting of a slip containing about 38vol% of FA-CZP. Temperature programs were created for debindering and sintering of the green foil and the four-fold laminate, respectively.
Surface Modification of Vacuum Plasma Sprayed Titanium Coating via Two Different Treatments
Authors: Chen Yi Kai , Zheng Xue Bin , Ji H. , Ding Chuan Xian , Lee S.W.
Published: March 2009

Vacuum plasma sprayed (VPS) Ti coatings were deposited and their surface modification
processes were performed by NaOH solution treatment and alkali-heat-calcification respectively.
The simulated body fluid test indicated that apatite was formed on the surfaces of Ti coatings. A
net-like structure was observed on the surfaces of Ti coatings treated by alkali-heat-calcification,
whose bioactivity is much better than that treated by NaOH aqueous solution simply.
Hydroxyapatite and Bioactive Glass Composite Coating on Ti6Al4V
Authors: Du Rui Lin , Zeng Shao Xian , Wu Yu Huai , Xie Xing Hui
Published: March 2009

Hydroxyapatite (HA) was widely used as coating on metals and alloys to enhance the
interconnection between metal implants and bone. To improve the bonding strength and bioactivity,
in this work, bioactive glass (G) was added and HA-G composite coating was prepared on
Ti-6Al-4V at low temperature. The scanning electronic microscope (SEM) graphs showed that the
surface of the coating was composed with needle-like crystals, and the X-ray diffractometer (XRD)
and Fourier transform infra-red spectrometry (FTIR) results proved that the crystals was carbonate
hydroxyapatite (CHA), no other crystal phase was detected. The SEM micrographs of the cross
section showed that the coating was porous and bonded closely with the surface of the alloy. The
energy diffraction spectra (EDS) result show that a Si-Ti-Al-V-O layer was formed at the interface
and enhance the interconnection between the coating and alloy. The bonding strength of the coating
was 34.8±6.8MPa, which was much higher than that of the pure HA coating on Ti-6Al-4V
prepared by plasma spraying method. The HA-G composite coating on Ti-6Al-4V showed high
bonding strength, porous structure, and bone like CHA composition, which has good potential to be
used as bone substitutes.
Crystallization of a Bone-like Apatite from a Milk-Containing Revised Simulated Body Fluid (SBF)
Authors: Dorozhkin Sergey V. , Dorozhkina Elena I. , Salman S. , Oktar Faik N.
Published: March 2009

Revised simulated body fluid (rSBF) was prepared using a conventional route but all the chemicals were dissolved in commercial cow milk instead of de-ionized water. To accelerate crystallization and increase the amount of precipitates, the influence of milk on the crystallization of calcium phosphates was studied in supersaturated solutions equal to 4 times the ionic concentrations of rSBF. The experiments were carried out in physiological conditions, i.e. pH of 7.35–7.40, temperature of 37.0 (± 0.2) °C, and duration of 7 days, using a constant-composition double-diffusion (CCDD) device, which enables slow precipitation in strictly controlled crystallization conditions. Similar experiments with 4 times the ionic concentrations of rSBF using de-ionized water as solvent were carried out as control. For comparison purposes, another set of experiments with 4 times the ionic concentrations of rSBF in de-ionized water also containing 40 g of bovine serum albumin (BSA) per liter was also conducted. The experimental results showed that the behavior of milk was similar to the presence of dissolved BSA. Some components of milk, presumably proteins, co-precipitated with calcium phosphates. This phenomenon had a strong negative influence on the crystallinity of the precipitates.
Ultra-Thin Film of Chitosan and Sulfated Chitosan Coating on Titanium Oxide by Layer-by-Layer Self-Assembly Method
Authors: Li Quan Li , Huang Nan , Wan Guo Jiang , Zhao L.S. , Tang Xu Yan
Published: March 2009

The ultra-thin film composed of chitosan (CS) and sulfated chitosan (SCS) was
assembled on the titanium oxide surface by layer-by-layer (LBL) self-assembly methods. The
titanium oxide film was treated by NaOH solution, followed by successively dipping the substrates
in 5mg/ml sulfated chitosan (SCS) and 5mg/ml chitosan (CS) solutions alternatively, We
hypothesized that this biologic coating may have the property of good biocompatibility,
antibacteriostatic effect, anticoagulant activitves and enhancing sell biocompatibility.
The Effect of Titania Deposited by Hydrolysis at Low Temperature on Aptite Formation Ability in DMEM
Authors: Xiao Fan , Song Ren Guo , Osaka Akiyoshi
Published: March 2009

Heating reduces the amount of Ti-OH groups in the surface layers that are considered to
favor apatite nucleation. Thus, low temperature processes are developed to fabricate bioactive
titania. Anatase/rutile dual layers were deposited on titanium substrates when they were soaked in
TiOSO4/H2O2 solution at low temperature, and than aged in hot water, which can induce apatite
formation in DMEM. The resulted titania layers have apatite-forming ability. The organic
molecules in DMEM medium had reduced the apatite formation on as-treated substrates in some
measure.
Biomimetic Synthesis of the Nanocomposite of Phosphorylatd Chitosan and Hydroxyapatite and its Bioactivity In Vitro
Authors: Li Quan Li , Huang Nan , Chen Zhi Qing , Tang Xu Yan
Published: March 2009

Phosphorylated chitosan (PCS) was used as the template to control
hydroxyapatite(HAp) growth, a novel nanocomposite composed of PCS and HAp was
synthesized by biomimetic method. Calcium phosphate (Ca 2+= 60mM, Ca/P = 1.67) solution in
HCl was added dropwise into PCS solution in NaOH. The precipitate was lyophilized to obtain
the composite. The biocompatibility of the PCS-HAp nanocomopite was evaluated by osteoblast
culture in vitro. The results showed that low crystallized HAp nanocrystals was formed on the
PCS fibers and its crystallographic c-axis were aligned preferentially parallel to the long axis
direction of PCS; the composite have good biocompatibility in vitro. It is expected that the novel
composite to be a potential material for bone repair.
Carbonate Substitution and Preferred Growth Orientation of Biomimetic Apatites
Authors: Müller Frank A. , Müller Lenka , Caillard Daniel , Conforto Egle
Published: March 2009

Simulated body fluid (SBF) solutions are widely used for in vitro bioactivity tests and to
coat bioinert materials with biomimetic calcium phosphates. In this study SBF solutions with varying
HCO3
- content were used to precipitate hydroxy carbonated apatite (HCA) on a bioactive titanium
surface. XRD as well as cross-sectional TEM analyses revealed that the biomimetically derived
crystallites show a preferred growth orientation in direction of their c-axis and perpendicular to the
surface of the substrate. FTIR and Raman analyses revealed that, as long as the HCO3
- concentration
in the testing solutions is below 20 mmol/l, only B-type HCA precipitates. Using SBF with a HCO3
-
concentration equal to human blood plasma (27 mmol/l) leads to a AB-type substitution where, in
accordance with bone mineral, CO3
2- substitutes PO4
3- as well as OH-.
Collagenous Molecule Immobilization on Hydroxyapatite Surface
Authors: Jiang Bo , Wu Zhi Hong , Zeng Jing Ying , Lu Jian , Wei Qing Rong , Zhang Xing Dong , Gu Zhong Wei
Published: March 2009

Collagenous molecule was successfully immobilized to hydroxyapatite (HA) surface through a molecular bridge (2-Hydroxyethyl acrylate, HEMA) that was grafted to the surface with covalent bond by gamma irradiation. Hydroxyapatite modified by atelocollagen had been characterized by several surface sensitive techniques, such as FT-IR, SEM, XPS. The investigations showed that the collagen, a bioactive macromolecule, was immobilized on the HA surface through covalent bond.
Preparation and Biocompatibility of Tantalum Oxide Films Containing the Hydroxyl Group
Authors: Tao T. , Li Gui Cai , Yao Y. , Wang X.F. , Yang Ping , Cheng J.Y. , Leng Yong Xiang , Huang Nan
Published: March 2009

Amorphous Ta-O films were synthesized by reactive pulse unbalanced magnetron sputtering system in this paper. Then the well-crystallized Ta-O films were obtained after they were annealed in vacuum at 800°C for 1h. Hydroxyl group on the surface of amorphous tantalum oxide films was prepared by plasma hydrogenation method. The phase structure was investigated by X-ray diffraction (XRD). The hydroxyl group was characterized using Fourier transform infrared spectroscopy (FTIR). The morphology and growth behavior of the vitro platelet adhesion on the as-deposited, annealed and plasma hydrogenated Ta-O films were analyzed through scanning electron microscope (SEM). The results showed that the quantity of platelet adhered onto the annealed surface were less than as-deposited and hydrogenised films. A new method of preparing hydroxyl group without coupling agents on the inorganic biomaterials has been studied by plasma hydrogenation.
Strontium-Substituted Calcium Phosphate Cements Prepared with Strontium-Containing Solutions
Authors: Fujihara Emi , Kon Masayuki , Asaoka Kenzo
Published: March 2009

The purpose of this study was to determine if a strontium (Sr)-containing mixing liquid
could be used as an exchanging agent for calcium phosphate cement crystallized with Sr-replacing
hydroxyapatite (Sr-HAP). Alpha-tricalcium phosphate (α-TCP) powder was mixed with Srcontaining
and phosphorous (P)-containing solutions, that is, SrCl2 or SrCl2+CaCl2 solution and
NaH2PO4 or Na2HPO4 solution. After storage in the incubator for 7 days, the α-TCP crystals in all
set cements were confirmed to have been transformed to HAP crystals by the mixing liquids. The
XRD patterns of the set cements implied that the Sr-HAP could be precipitated by using Srcontaining
solutions as the mixing liquid because of the chemical shift of a peak (002) in XRD of
the HAP crystal. The solubility (shaking immersion in physiological saline) of set cements
containing Sr was markedly higher than that of set cement not containing Sr. These results revealed
that the Sr-containing solutions used as mixing liquids for α-TCP cement acted as precipitating
agents for Sr-HAP. Sr-HAP-precipitating cement could be useful because of its pharmacological
activity with high solubility.
Covalent Immobilization of Heparin on Anatase TiO2 Films via Chemical Adsorbent Phosphoric Acid Interface
Authors: Weng Ya Jun , Hou Ruixia , Xie Dong , Wang Jin , Huang Nan
Published: March 2009

Heparin is covalently immobilized onto the surface of anatase TiO2 film using the
bifunctional linking reagent, APTES (3-Aminopropyltriethoxylsilane), which can be bonded to the
film by reaction between ethoxyl of the linking reagent and hydroxyl of the film. Compared to the
control, the immobilization is enhanced by phosphoric acid chemical pre-adsorption on the film for
there is more hydroxyl group present. Platelets deposited to heparinized surface showed only minor
spreading and aggregation. The results of this study suggest that heparin immobilization to anatase
TiO2 films via phosphoric acid interface may improve the in vivo blood compatibility.
Comparing Adsorptive Property of Natural and Synthesized Hydroxyapatite to Albumin, Fibrinogen and IgG
Authors: Lü Xiao Ying , Yan Huang , Zheng Bu Zhong , Wu Ai Ping
Published: March 2009

The aim of this study was to compare the plasma protein adsorptive property of the
natural hydroxyapatite (HA) and the synthesized HA to human albumin (Alb), fibrinogen (Fib) and
immunoglobulin G (IgG). Different methods such as reflectometry interference spectroscopy (RIfS)
measuring, Fourier transform infrared spectroscopy (FTIR) analysis and weighing assessment were
used to measure the adsorbed amount of Alb, Fib and IgG on the natural HA and the synthesized
HA. To compare the adsorptive property of protein adsorbed on these two kinds of materials, the
ratio of Alb/Fib (RA/F) and the ratio of Alb/IgG (RA/I) were calculated. The results from all three
methods showed that the values of RA/F and RA/I obtained with natural HA were smaller than those
obtained with synthesized HA, that indicated that the natural HA adsorbed more human fibrinogen
than human albumin and thas it would enhance blood coagulation and in favor of bone repairing.