bluuebunny/crossref_metadata_2025 huggingface dataset:
On the Size Effect in Hardness by Nanoindentation Method
Authors: Lee Hun Kee , Ko Seong Hyun , Park Hyun Chul
Published: March 2009

A model describing nanoindentation as plastic deformation resulting from a strain gradient is investigated. Using a simplified axisymmetric nanoindentation, the effective strain gradient for indentation depth is derived. The proposed indentation model is a modification of Nix and Gao’s model (1998) . To validate this approach for nanoindentation, solutions for depth-dependent hardness of single various materials such as Cu, Al, Ni are compared with experiments. Results show that the proposed model agrees well with the hardness experiments.
Computer Simulation of Microstructure Evolution of Fe-Cu Alloy during Thermal Ageing
Authors: Takahashi Akiyuki , Soneda Naoki , Kikuchi Masanori
Published: March 2009

This paper describes a computer simulation of thermal ageing process in Fe-Cu alloy. In order to perform accurate numerical simulation, firstly, we make numerical models of the diffusion and dissociation of Cu and Cu-vacancy clusters. This modeling was performed with kinetic lattice Monte Carlo method, which allows us to perform long-time simulation of vacancy diffusion in Fe-Cu dilute alloy. The model is input to the kinetic Monte Carlo method, and then, we performed the kinetic Monte Carlo simulation of the thermal ageing in the Fe-Cu alloy. The results of the KMC simulations tell us that the our new models describes well the rate and kinetics of the
diffusion and dissociation of Cu and Cu-vacancy clusters, and works well in the kinetic Monte Carlo simulations. Finally, we discussed the further application of these numerical models.
Porous Ceramics of β-Tricalcium Phosphate Composed of Rod-Shaped Particles is Highly Biodegradable and Expresses Prominent Osteoconductivity
Authors: Okuda Takatoshi , Yonezawa Ikuho , Ioku Koji , Minagi Hideyuki , Kurosawa Hisashi , Ikeda Tohru
Published: March 2009

Newly developed porous β-tricalcium phosphate composed of rod-shaped particles was grafted into distal end of the left femur of female Japan White rabbit. As a control, hydrixyapatite generated in the same size was grafted. In both implants, 350µm in diameter-sized holes were created vertically and
horizontally. Three weeks after grafting, margin of the β-tricalcium phosphate was absorbed by osteoclasts and bone formation was seen near the absorbed region. Twenty-four weeks after grafting, more than 80% of the β-tricalcium phosphate was absorbed and newly formed bone was prominently observed. The
hydroxyapatite was not remarkably absorbed even 24 weeks after grafting, and newly formed bone was observed only in the holes created in the implants. These results suggest that porous β-tricalcium phosphate
composed of rod-shaped particles has highly biodegradable and osteoconductive nature, and appropriate to bone graft substitute.
Preparation of Porous Composites with a Porous Framework Using Hydroxyapatite Whiskers and Poly(L-Lactic Acid) Short Fibers
Authors: Mizutani Yoichiro , Hattori Masateru , Okuyama Masahiko , Kasuga Toshihiro , Nogami Masayuki
Published: March 2009

A new type of porous composite with a porous framework was prepared using a mixture of hydroxyapatite whiskers (W-HA) and poly(L-lactic acid) short fibers (F-PLLA) by a particle-leaching technique. The material, composed of a porous framework with interconnecting pore of >1 µm, has large-sized pores of about 200 µm. The large-sized pores were formed by leaching sucrose granules. The porosity can be controlled in the range from 60 to 85 % by the sucrose content. The small-sized pores in the framework formed due to the poor densification of the
W-HAs / F-PLLAs mixture. The pore distribution in the framework can be controlled by the compressing pressure without change in the distribution of large-sized pores.
A New Way to Prepare Porous Polylactide /Hydroxyapatite Scaffold at Room Temperature
Authors: Wang Yi , Fan Hong Song , Xiao Yu Mei , Gu Zhong Wei , Zhang Xing Dong
Published: March 2009

A new way to prepare polymer/hydroxyapatite(HA) composite scaffolds with 3-D
interconnected macro and micro pores at room temperature was established, basically based on solvent-casting and particle-leaching together with foaming technique. With this method, Polylactide (PLA) / HA composites of porous architecture with macro pores (50~300)m, average 200)m) and micro pores (~10)m) on the skeleton were obtained. The bending strength and the
compressive strength of the composite scaffold were reached to 11.5 MPa and 7MPa respectively with the porosity of approximate to 90%. The study supplied a new short time, low energyexpending method to prepare polymer/ceramic composite with high porosity and interconnected porous structure at room temperature.
3-D Analysis of Pore Structure of Porous Biomaterials Using Micro Focus X-Ray Computed Tomography
Authors: Takemoto Mitsuru , Fujibayashi Shunsuke , Otsuki B. , Matsushita Tomiharu , Kokubo Tadashi , Nakamura Takashi
Published: March 2009

Generally, characterizations of pore structures of porous biomaterials are mainly based on 2-dimensional (2-D) analysis using cross sectional micrographs. However, interconnectivity of each pore may be more important factor, when tissue ingrowth into deeper pores is considered. In this paper, using micro-CT imaging with 3-D image processing software, analyses of porous material based on 3-demensional (3-D) geometrical considerations were successfully performed. Plasmasprayed porous titanium implant (PT) and four types of sintered porous titanium implants (ST50- 200, ST50-500, ST70-200, and ST70-500) that possess different porosities (50% and 70%) and pore sizes (200-500+m and 500-1500+m) were analyzed in this study. A micro focus X-ray computed
tomography system was employed to acquire microstructural information from the porous implants. Using 3-D image processing software, we performed three types of 3-D analysis including detection of the dead space (% dead pore), analysis of interconnectivity by blocking the narrow pore throat with caliber less than 52 +m (% pore with narrow throat) and analysis of material construct by
contracting thin strut with thickness less than 52 +m (% construct with thin strut). ST50S and ST50L possessed interconnected porous structure with thicker strut; however, pore throat was considered to be relatively narrow. On the other hand, PT implant possesses favorable interconnectivity despite its’ low porosity; however, relatively thin strut indicate the structural disadvantage for mechanical property. These results suggest that the 3-D analysis of pore and strut structure using micro focus X-ray computed tomography and 3-D image processing software will
provide effective information to develop porous implant.
In Situ Synthesis of PVA-PAA-HA Interpenetrating Composite Hydrogel
Authors: Wang Xiao Min , Li Xu Dong , Zheng Gui Qiu , Jiang Jian Ming , Chen Ji Yong , Zhang Xing Dong
Published: March 2009

A composite hydrogel with interpenetrating network structure was prepared via in-situ synthesis of calcium phosphates during the physical-chemical crosslinking of poly(vinyl alcohol) (PVA) and poly(acrylic acid) (PAA). The hydrogel water content was tested. Fourier transform
infrared absorption spectrum (FT-IR), X-ray diffraction and scanning electron microscopy were employed to evaluate the characteristics of the composite hydrogel. The results showed that the composite hydrogel had high water content and that the inorganic phase was poorly crystalline
calcium phosphates. FT-IR confirmed that the interpenetrating network structure was formed between PVA and PAA. The chemical interactions between inorganic and organic phases were further investigated and discussed. The composite hydrogel with an interpenetrating network achieved using the present novel method could be a promising material for tissue engineering.
Biodegradation of Multilayer Silk Fibroin and Hydroxyapatite Composite Material
Authors: Kino Rikako , Ikoma Toshiyuki , Yunoki Shunji , Monkawa Akira , Matsuda Atsushi , Kagata Go , Asakura Tetsuo , Munekata Masanobu , Tanaka M.
Published: March 2009

Silk fibroin (SF) films containing 5wt% of CaCl2 were prepared by a cast-film method from the degummed SF and then immersed into the simulated body fluid (SBF) to deposit hydroxyapatite (HAp) crystals. The multilayer film of HAp and SF (5-layers), and pure SF film (4-layers) were prepared by a thermo-compression method at 130 °C and 3MPa for 4min. The ratio
of β-sheet structure against other structures in both samples showed almost same value of 55.8% and 55.1%. The swelling ratio and in vitro biodegradation were examined by incubating in phosphate-buffered saline (PBS) with and without protease XIV for 1 to 14 days. The changes of sample weight and its tensile strength were investigated. The multilayer film showed slower biodegradation and higher mechanical strength compared with pure SF film.
Silicon Dissolution from Microporous Silicon Substituted Hydroxyapatite and its Effect on Osteoblast Behaviour
Authors: Guth Katharina , Buckland Tom , Hing Karen A.
Published: March 2009

In this study silicon release from SiHA into tissue culture medium was investigated under static and semi-dynamic conditions. The effect of silicon release under semi-dynamic conditions on alkaline phosphatase activity (ALP) and collagen I (CICP) expression by osteoblast like cells (HOS TE85) was also examined. Under static conditions a low level of silicon was released within 24 hours, this initial level dropped over 3-7 days but subsequently increased again by 10-14 days. Under semi-dynamic conditions silicon was released within 24 hours and was subsequently reduced with each medium change until equilibrating at close to 0 after 10 days. ALP and CICP showed significant variation in expression between culture conditions. In direct contact with SiHA ALP peaked at day 10 and CICP was constantly elevated. Cells grown in the presence of but not on SiHA expressed progressively decreasing levels of ALP from 7-14 days, with CICP peaking at day 10. On thermanox (TMX) ALP constantly increased and CICP peaked at day 10. The results indicate that silicon leaches out of the lattice of the SiHA crystal structure but may also be reprecipitated onto the substrate. We have also demonstrated that Si influences osteoblast metabolism and differentiation whether it is available as free silicon or 'bound' in the apatite lattice.
Hydroxyapatite Hip Arthroplasty in Osteoporotic Bone: A Study in Female Patients Over the Age of Sixty
Authors: Buchanan James M.
Published: March 2009

Uncemented hip arthroplasty is gaining interest. However, it is alleged that uncemented hip implants fail in osteoporotic bone because of early loosening and a higher incidence of periprosthetic fractures. Will Hydroxyapatite Ceramic Coated Hips (HAC) bond on to the osteoporotic bone and continue to function well in this vulnerable group of patients? Post-menopausal women are prone to develop osteoporosis. They are seen too frequently with wrist, hip and spinal crush fractures following minor low impact injuries. These ladies also contribute to the cohort of patents requiring hip arthroplasty for all the usual diagnoses including sub capital fractures. This is a study of HAC hip arthroplasty in female patients over the age of sixty which includes women with osteoporosis.
Revision Total Hip Arthroplasty Performed with a Contemporary Alumina-on-Alumina Bearing Surface; Minimum 5-Year Follow-Up Study
Authors: Yoo Jeong Joon , Kim Hee Joong , Kim Young Min , Yoon Kang Sup , Koo Kyung Hoi , Nam Kwang Woo , Shin Sang Ik
Published: March 2009

Limitation in liner and head options available to the surgeon may be the most practical disadvantage of alumina-on-alumina total hip arthroplasty (THA). This may be more problematic in the revision THA. We evaluated the results of 57 revision THAs (average, 46.2 years old) performed with a contemporary alumina-on-alumina bearing surface after a 5-year minimum follow-up (average, 67 months; range, 60-85 months). A third generation alumina-on-alumina bearing (BIOLOX® forte, CeramTec AG) and a cementless PLASMACUP®-BiCONTACT® hip revision system (AESCULAP AG & Co.) had been used in all patients. Alumina bearing was chosen for a relatively young active patient in whom an acetabular bone defect was not severe and an extremely long neck of artificial head was not required for the restoration of hip joint mechanics. The average Harris hip score improved from 65.0 points to 88.9 points. No implant loosened, no stem or cup was re-revised, and no additional reoperations were required. Ceramic wear was undetectable in 14 hips where differentiation of the femoral head from the cup was possible on radiographs and no osteolysis was observed. During the follow-up period, no hip demonstrated signs of infection or ceramic failure. Short-term results of revision THAs performed with analumina-on-alumina bearing are encouraging. We believe that physiological age and activity level of a patient, severity of acetabular bone loss, and availability of alumina head and liner options required for the restoration of proper limb length and joint stability should be considered to choose this alumina bearing surface during the revision THA.
Efficacy of HA Block Kyphoplasty for Old Osteoporotic Spine Fractures
Authors: Nishimura Taichi , Matsuzaki Hiromi , Okawa Akihiro , Oshima Masashi
Published: March 2009

We have successfully treated osteoporotic spine fractures for about three years, by using transpedicular kyphoplasty with hydroxyapatite blocks (HA Block: PENTAX) (refer with: Fig. 1), The 13 patients, four men and nine women, ranged from 61 to 86 years in age (mean, 73 years). The mean Visual Analogue Scale (VAS) was 8.5 points before operation, improved to 2.7 points on
the next day of operation, and improved significantly to 1.8 points at the final evaluation. The mean deformity rate (Anterior height / Posterior height x 100) was 66.3% before operation, but improved to 91.7% immediately after operation. At the time of follow-up, this rate was 78.6%, indicating that
the correction loss was 13.1%. This procedure caused none of serious complications such as neurological disorder and pulmonary infarction. Kyphoplasty with HA blocks may be safe and effective in the treatment of chronic vertebral fractures.
Stress Distribution in Teeth Due to Dimensional Changes of the Restorative Material
Authors: Engqvist Hakan , Gupta R.
Published: March 2009

The objective of this paper is to theoretically investigate the stress distribution in a tooth model due to expansion or contraction of the filler material. Finite element calculations were carried out to determine the stresses and deformations in a model of the tooth. The tooth was modelled to consist of two concentric cylinders, an inner cylinder of 7 mm diameter dentine and an outer layer of 1 mm thick enamel. The two cylinders were assumed to be rigidly fixed at the bottom end and the top end was free. Different sizes of occlusal cavities (2, 4 and 7 mm) as well as mesial-occlusal and mesial-occlusal-distal were simulated through removal of dentine from the centre. The fillings were subjected to an internal pressure of 1 MPa and a chewing pressure of 1 MPa. Since the cylinders were rigidly fixed at one end, the inner part of the cavity (dentine) tended to bend outwards, thus compressing the outer (enamel) layer. This behaviour, coupled with a strong mismatch of the elastic moduli of dentine and enamel, leads to widely different distributions of stress in the tooth as the cavity sizes and filling types are varied. The radial deformations were of the order of microns, most of it occurring in the softer dentine. The maximum stresses occur in the stiffer enamel layer when a chewing pressure is applied, without a chewing pressure the stresses are more evenly distributed.
TEM Examinations of OCP/HA Transformation
Authors: Xin Ren Long , Leng Yang , Wang Ning
Published: March 2009

We have directly observed the transformation from octacalcium phosphate (OCP) to hydroxyapatite (HA) in transmission electron microscope (TEM). The phase transformation was induced by electron beam irradiation in TEM. Several TEM techniques were employed to examine the crystal structure change, including bright field images, electron diffraction, high resolution microscopy (HRTEM) and fast Fourier transformation pattern of HRTEM images. The examinations indicate possible hydrolysis reaction in solid state transformation and crystallographic
orientation of OCP (010)//HA (010) and OCP (001)//HA (001) which has not been reported previously.
Biodegradation and Characterization of Phase Separated NaCa(PO3)3 and KCa(PO3)3 from Pure Ca(PO3)2
Authors: Chun Sung Su , Tadjiev Timur R. , Kim Kyo Han , Lee J.H. , Kim Suk Young
Published: March 2009

Degradation characteristics of calcium metaphosphate (CMP) ceramics substituted by 5, 10, 15, 20 mol% of NaPO3 and KPO3, respectively, was evaluated in revised simulated body fluid (R-SBF) by measuring the weight change, flexural strength, crystalline phases, and surface morphology with immersion period. The weight loss of CMP substituted by KPO3 was significantly higher than that of CMP substituted by NaPO3. The weight loss in the KCa(PO3)3–CMP samples
was due to the dissolution of KCa(PO3)3 phase. The flexural strength of NaCa(PO3)3–CMP samples increased, however, that of KCa(PO3)3–CMP samples decreased significantly due to the dissolution of KCa(PO3) phase with immersion period. The dissolution of KCa(PO3)3 phase formed a pore
structure in KCa(PO3)3–CMP samples.
Comparative Study of the Degradation Behavior of Mechanically Mixed and Chemically Precipitated Biphasic Calcium Phosphates
Authors: Yang D.J. , Tadjiev Timur R. , Kim Jae Woong , You Chang Kuk , Choi S.K. , Park K.B. , Ryoo K.H. , Kim Suk Young
Published: March 2009

Surface morphology and degradation behavior of mechanically mixed and chemically precipitated biphasic calcium phosphate (M-BCP and P-BCP) were compared. For the M-BCP powder, commercial HA and TCP powders were used. In order to prepare P-BCP powder, precipitation method was used. The particle size of P-BCP was smaller than that of M-BCP. The disk-type specimens of each powder were prepared for the morphology comparison and degradation test. The surface morphology of sintered samples was porous in M-BCP and dense in P-BCP. The degradation test was conducted in the revised simulated body fluid (R-SBF) for 1, 7, and 21 days. Surface morphology and degradation rate of two samples were different. The weight gain in both samples increased linearly with immersion period due to apatite-like layer formation. However, the weight gain in M-BCP was much higher than that in P-BCP. The weight gain was related to the surface morphology and degradation with immersion period.
Histomorphology on Healing of the Chitosan Membrane and β-TCP on Dental Implant Dehiscence Defects in Dogs
Authors: Kim Y.S. , Kim Tae Gyun , Jung Ui Won , Kim C.S. , Choi Seong Ho , Cho Kyoo Sung , Kim Chong Kwan
Published: March 2009

Dehiscence bone defects, frequently observed on dental implants placed in
periodontitis-affected alveolar bone or extraction sockets were treated with β-tricalcium phosphate (β –TCP) and chitosan membrane for guided bone regeneration, and the new bone formation on the treated sites were studied. Beagle dogs were used for the experiment. First to fourth mandibular premolars were extracted, and the post extraction alveolar bone surface was planed. After 8 weeks of healing, 3 by 4mm dehiscence defects were created using straight fissure burs. Total of 16 oxidized titanium surface implants were placed on the bone defects of the subjects, two on each side. Control sites were treated with implants only. Experimental Group 1 sites were treated with implants and
chitosan membrane. Experimental Group 2 sites were treated with implants, β-TCP and chitosan membrane. Experimental Group 3 sites were treated with implants, β-TCP, autogenous bone and chitosan membrane. The animals were sacrificed 12 weeks after implant placement, and the specimens from the treated sites were histologically studied with following results. Limited amount of
new bone formation was observed in control group with unexposed membrane. Slightly greater amount of bone formation was observed on sites treated with β-TCP+membrane or autogenous bone+ β-TCP+membrane compared to control group. Remnants of chitosan membrane and β-TCP encapsulated with connective tissue were observed during experimental periods. These results
suggest that further studies are needed on membrane rigidity and infection control for space maintenance underneath the membrane and bone substitutes in the treatment of dehiscence defects.
The Analysis of Osteoconducting Ability of Alpha-Tricalcium Phosphate-Based Bone Filler Powder
Authors: Yoo Jeong Hyun , Lee Kang Sik , Lee Soo Ho
Published: March 2009

Titanium alloy(Ti-6Al-4V, Samsung techwin, Korea) rods with diameter of 2.5mm were used as the implant materials. Polymethyl methacrylate(PMMA) bone cements(CMW, USA) were used as bone cement and -tricalcium phosphate(TCP)-based bone filler powder was used as osteoconductive additives. Hydroxyapatite(HA) was the desired end product after hydrolysis of the
-TCP-based bone filler powder mixed with the blood. In animal study using rabbits, we divided the group into A, B, C and D. Rabbits were sacrificed at 1, 3, 9 weeks after implantation and the affinity index and bone density were calculated. X-ray diffraction patterns of HA formed by hydrolysis of -TCP-based bone filler powder showed higher and higher intensity in HA peak with increase of time period. There was more bone density increase in the group B and D containing -
TCP-based bone filler powder around implant site than in the group A and C(p<0.05). It is suggested that HA formed by hydrolysis of -TCP-based bone filler powder will play some parts in enhancing osteconducting ability in clinical settings.
Dense Sintered Long-Term Stable Ceramics in the System CaO-P2O5-ZrO2-F
Authors: Ploska Ute , Berger Georg , Willfahrt Manfred
Published: March 2009

The influence of several sinter additives (three glasses, magnesium acetate, bismuth trioxide) on the compressive strength and also on the solubility of a sintered ceramics, which is composed of 57.6Mol% CaO, 26.2Mol% P2O5, 10.4Mol% ZrO2 and 5.8Mol% CaF2 was tested. The amount of sinter additives, pre-mixing of the powders, pressure power, sintering temperature and sintering time were varied. The most dense samples were produced with the finest powders (D50 ~ 1/m) and the highest sintering temperatures (1200°C). The mechanical stability of the samples was more influenced by the particle size of the powders than by the kind of binder as well as the pressure power. The compressive strength of the sintered samples ranged between 180MPa (D50 of the powder = 2.4/m) and 530MPa (D50 of the powder < 1/m). Storing of the samples in simulated body fluid for 4 weeks at a temperature of 37°C did not influence the compressive strength significantly. The sintered ceramics can be finished, for instance by grinding or polishing.
A Histological Study of Human Derived Tooth-Hydroxyapatite (THA)
Authors: Oktar Faik N. , Sayrak H. , Ozsoy S. , Heybeli Nurettin
Published: March 2009

Different types of bone-graft substitutes have been developed and are in the market worldwide to eliminate the drawbacks of autogenous grafting. They vary in composition, strength, osteoinductive and osteoconductive properties, mechanism and rates by which they are resorbed and remodelled. Tooth derived hydroxyapatite (THA) is a novel biomaterial. This study was performed to determine the histological properties of THA on animals. A commercial coralline HA (CHA, Proosteon 200, Interpore Cross, USA) was used as control material. 20 sheeps were used and divided into 2 groups. Human THA (Group A) and CHA (Group B) materials were implanted to the tibiae of 10 sheeps for each group. The histological examinations of surrounding bone response were done 12 weeks after implantation. There was no significant difference histologically between group A and B. All materials were found to be surrounded by new bone tissue. THA was found to be as efficient as the standard CHA on histological basis. In addition, economical production of THA should be taken into consideration. Therefore, THA may be a viable alternative on bone grafting provided that clinical trials will be completed.
In Vitro Study of HA and CMP Grit-Blasted and Acid Etched of Ti Surface
Authors: Haryadi A.W. , You Chang Kuk , Kim Shin Yoon , Park Eui Kyun , Kim Suk Young
Published: March 2009

Grit-blasting using bioactive HA and biodegradable CMP followed by acid etching was done. The apatite formation of prepared Ti samples was evaluated by immersion in R-SBF. And cell viability, proliferation, and differentiation were conducted using MTT assay and ALP staining. In RSBF immersion tests, non-etched HA-blasted samples showed the faster apatite-like formation than other samples. Acid etched and non-etched HA-blasted samples showed better cell viability and proliferation compared to CMP-blasted samples after 1 and 3 days. And the cell differentiation of non-etched HA-blasted samples was better compared to etched ones, and etched and non-etched CMP-blasted samples.
Early Cellular Responses of Osteoblast-Like Cells on Acid-Etching and Alkaline Treated Titanium
Authors: Miyamoto Motoharu , Kono Hiroshi , Yuda Akihiko , Goto Hisanoro , Machigashira Miho , Ban Seiji , Izumi Yuichi
Published: March 2009

The effects of four surface modification (acid-etching, alkaline treatment, acid-etching /alkaline treatment, and sandblasting) of commercially pure titanium (cpTi) on the early cellular responses of osteoblast-like MC3T3-E1 cells were investigated. MTT assay was used to measure the levels of cell attachment to the different surface specimens after 1-, 2-, and 3-hr cell incubation. All data were submitted to two-way analysis of variance. Cell morphology was observed by scanning electron microscopy (SEM). Results showed that initial adhesion of osteoblast-like cells was independent on the surface of cpTi modified with different method.
Effect of Heat-Treatment Temperature on the Osteoconductivity of the Apatite Derived from Bovine Bone
Authors: Rhee Sang Hoon , Park Ho Nam , Seol Yang Jo , Chung Chong Pyong , Han Sang Hyuk
Published: March 2009

Effect of heat-treatment temperature on the osteoconductivity of the apatite derived from bovine trabecular bone was investigated. Three different heat-treatment temperatures (600, 800 and 1000 oC) were adopted in the experiment and their effects on the physical properties of apatite granules, which could affect on the osteoconductivity, were evaluated. The content of carbonate ions
in the apatite structure was assessed by FT-IR and its crystallinity was evaluated by X-ray diffractometry. The microstructure was assessed by field emission electron microscopy. Apatite granules heat-treated at 600 oC and 1000 oC were implanted into the calvaria of New Zealand White rabbit for 4 weeks, respectively, and the undecalcified ground histologic specimens stained with
multiple staining method was observed. As increasing the heat-treatment temperature, the crystal size and crystallinity of the apatite increased while the content of carbonate ions decreased. The apatite granules heat-treated at 600 oC showed much better osteoconductivity comparing to that heat-treated
at 1000 oC. The results were explained in terms of the physical properties of apatite which could affect to the osteoconductivity.
Porous Titanium Membranes Combined with Various Graft Materials Induce Exophytic Bone Formation in Rabbit Calvaria
Authors: Kim Y. , Kown Y.H. , Park J.B. , Chung J.H. , Lim H.N. , Jue S.S. , Cho M.I. , Herr Y.
Published: March 2009

The purpose of this study was to examine if the application of custom-made porous titanium membranes combined with bone graft materials promotes exophytic bone formation in rabbit calvaria. For this purpose, round decorticated calvaria sites were created using a round carbide bur. In the control group, rectangular parallelepiped-shaped porous titanium membranes (RPTMs) were placed on the decorticated sites and fixed with metal pins. In the experimental groups, RPTMs were
filled with one of the following bone graft materials prior to fixing with metal pins: bovine bone mineral (BBM), demineralized freeze-dried human cortical bone (DFDB) or freeze-dried human cancellous bone (FDB). Animals were sacrificed at 8 and 12 weeks after surgery, and new bone formation was assessed by histomorphometric as well as statistical analysis. The results indicate
that at 8 and 12 weeks, all the experimental groups demonstrated exophytic bone formation. At 12 weeks, DFDB group revealed the most new bone formation (p<0.05) and resorption of grafted materials (p<0.05). On the basis of these findings, we conclude that RPTMs may be used as an augmentation membrane for guided bone regeneration and DFDB as an effective bone-inducing graft material.
Direct Gel-Casting of Zirconia for Dental Application: Gelation Kinetics and Pyrolysis of Organic Additives
Authors: Bergström Lennart , Ng Boon Sing
Published: March 2009

The gelation kinetics of two water-based gel-casting systems, made from reagents with very low acute toxicity, has been investigated. The zirconia particles greatly enhance the gelation rate, thus reducing both the temperature and time required for complete gelation. Binder burnout is complete and comparison of the pyrolysis of the net gel and the zirconia-based gel-cast parts revealed that the presence of zirconia particles accelerates the pyrolysis of the gel.
In Vitro and In Vivo Surface Reactivity of Various Calcium Phosphate Coatings Deposited Using Electrostatic Spray Deposition (ESD)
Authors: Leeuwenburgh Sander C.G. , Wolke Joop G.C. , Siebers M.C. , Schoonman J. , Jansen John A.
Published: March 2009

The dissolution and precipitation behavior of various porous, ESD-derived calcium phosphate coatings was investigated a) in vitro after soaking in Simulated Body Fluid (SBF) for several time periods (2, 4, 8, and 12 weeks), and b) in vivo after subcutaneous implantation in the back of goats for identical time periods. At the end of these studies, the physicochemical properties of the coated substrates were characterized by means of Scanning Electron Microscopy (SEM), XRay Diffraction (XRD), Fourier-Transform InfraRed spectroscopy (FTIR) and Energy Dispersive Spectroscopy (EDS). Moreover, part of the implants was prepared for light microscopical evaluation of the tissue response. In vitro, a highly bioactive behavior was observed for all ESD-coatings, characterized by the deposition of a thick and homogeneous carbonate hydroxyapatite precipitation layer on top of the porous coatings. Regarding the in vivo study, no adverse tissue reactions (toxic effects/inflammatory cells) were observed using light microscopy, and all coatings became surrounded by a thin, dense fibrous tissue capsule after implantation. The ESD-coatings degraded gradually at a dissolution rate depending on the specific chemical phase, thereby enabling synthesis of CaP coatings with a tailored degradation rate.
Development of Apatite Micropattern Test Specimen for Cell Operation
Authors: Okada Hidetaka , Yamaguchi Seiji , Hibino Mitsuhiro , Yao Takeshi , Hasegawa Shin , Neo Masashi , Nakamura Takashi
Published: March 2009

Apatite micropattern was fabricated by a combination of biomimetic process and transcription of resist pattern. We optimized some fabrication conditions such as the height of resist pattern, temperature, concentrations and pH of simulated body fluid(SBF). Consequently, we successfully obtained apatite micropattern widely and homogeneously on a substrate in a short fabrication period.
Progress of Structural Elucidation of Amorphous Calcium Phosphate(ACP)and Hydroxyapatite (HAp): Disorder and Surfaces as Seen by Solid State NMR
Authors: Jaeger Christian , Maltsev Sergey , Karrasch Andrea
Published: March 2009

Solid-state Nuclear Magnetic Resonance (NMR) has been used for a detailed structural analysis of different amorphous calcium phosphate (ACP) and hydroxyapatite (HAp) samples. For ACP the NMR data reveal the presence of hydrogenphosphate units in much larger quantities as known previously also showing differences between the samples. Furthermore, phosphate units close to water and a third group (yet unknown) are found in the spectra. A novel proposal has been established to explain the Ca-deficiency in nanocrystalline HAp. It consists of a crystalline core of stoichiometric composition which contains only 50% of the total phosphate amount. The residual phosphate is contained in a disordered surface layer with about 1 nm thickness. Most importantly, this surface layer contains hydrogenphosphate groups to a large extend and carbonate units. A Ca/P ratio of 1.52 is obtained from the NMR data which is very close to the value of 1.51 of the chemical analysis. Thus, NMR allows the investigation of the disordered mineral-protein interface and first examples concerning bone and nacre are presented and discussed.
Protein Adsorption Ability of Porous Hydroxyapatite Microparticle with Metal Ions
Authors: Tonegawa Toru , Ikoma Toshiyuki , Monkawa Akira , Chen Guo Ping , Tanaka M.
Published: March 2009

Hydroxyapatite (HAp) also shows the high absorption ability for proteins with low
degradations. In this study, to modify the absorption ability and to obtain high surface area, metal ions (Zn, Mg, Fe) were introduced in preparing the HAp nanocrystals, and porous microparticles were subsequent fabricated by a spray drying method. HAp microparticles with Zn, Mg, Fe ions had a single phase of low crystalline HAp. The specific surface area of the HAp, Mg-HAp, Fe-HAp and Zn-HAp were 87, 150, 152, 167 m2/g, respectively. In the adsorption experiment of a lysozyme as a
basic proteine, Zn-HAp showed the highest adsorption ability. On the other hand, the HAp microparticles witn metal ions showed higher adsorption ability for BSA as a acitic protein than pure HAp microparticles.
Biodegradable Bone Cement Using Calcium Phosphate Glass
Authors: Lee Byung Hyun , Kim Min Chul , Kim Kyoung Nam , Kim Kwang Mahn , Choi Seong Ho , Kim Chong Kwan , LeGeros Racquel Z. , Lee Yong Keun
Published: March 2009

In preliminary ageing test, the cement using only calcium phosphate glass as power phase cracked with 1 day in simulated body fluid because of high dissolution rate of the cement. We added 30 wt% of either β-TCP or HA to 70 wt% calcium phosphate glass as powder phase to control the dissolution rate of the cement and performed in vitro ageing test in simulated body fluid by dynamic protocol as well as static protocol to confirm the possibility of controlling. Adding either β-TCP or
HA to the cement increases the setting time and decreases the compressive strength. In dynamic assay, the pH of extract is maintained over 7. However, pH decreased to around 5 in static assay. Therefore, weight loss by static protocol continuously increased for 14 days, while weight loss by dynamic
protocol almost saturated. In XRD patterns of ageing cements, CaO peaks appeared. CaO peak was maximized most lately in dynamic assay of the cement adding HA and within 7 days, the cement adding HA showed higher weight loss. It is indicated that CaO formed in surface of the cement hinder the dissolution of the cement. In addition, compressive strength increased when the CaO peak was
maximized.
Controlled Release of rhBMP-2 Loaded Poly(DL-lactic-co-glycolic Acid)/ Calcium Phosphate Cement Composites In Vivo
Authors: Ruhé P.Q. , Boerman O.C. , Russel F.G.M. , Spauwen P.H.M. , Mikos Antonious G. , Jansen John A.
Published: March 2009

The release kinetics of recombinant human bone morphogenetic protein-2 (rhBMP-2) loaded poly(DL-lactic-co-glycolic acid)/calcium phosphate cement (PLGA/Ca-P cement) composites were studied in vivo. RhBMP-2 was radiolabeled with 131I and entrapped within PLGA microparticles or
adsorbed onto the microparticle surface. PLGA microparticles were prepared of high molecular weight (HMW) PLGA (weight average molecular weight [Mw] 49,100 ± 1,700) or low molecular weight (LMW) PLGA (Mw 5,900 ± 300) and used for preparation of 30:70 wt% PLGA/Ca-P cement composite discs. Release of 131I-rhBMP-2 loaded composites was assessed by scintigraphic imaging according to a 22 two-level full factorial design in the rat ectopic model during four weeks.
In vivo release kinetics varied among formulations. All formulations showed slow release without initial burst, and displayed a linear release from 3 to 28 days. Release of LMW entrapped rhBMP-2 composites (1.7 ± 0.3%/day) was significantly faster than release from other formulations (p <
0.01). After 28 days, retention within the composites was 65 ± 5%, 75 ± 4%, 50 ± 4% and 70 ± 6% of the initial rhBMP-2 for HMW entrapped, HMW adsorbed, LMW entrapped and LMW adsorbed rhBMP-2 composites, respectively. Release from the composite was probably slowed down by an interaction of rhBMP-2 and Ca-P cement after rhBMP-2 release from PLGA microparticles. We conclude that PLGA/Ca-P cement composites can be considered as sustained slow release vehicles and that the release and retention of rhBMP-2 can be modified according to the desired profile to a limited extent.
Mechanical and Fracture Properties of Bamboo
Authors: Low It Meng , Che Z.Y. , Latella Bruno A. , Sim K.S.
Published: March 2009

The microstructure, mechanical, impact and fracture properties of Australian bamboo have been investigated. The graded composition and property has been confirmed by depth-profiles obtained by synchrotron radiation diffraction and Vickers indentation. The mechanical performance of bamboo is stronly dependent on age. Results showed that young bamboo has higher strength, elastic stiffness and fracture toughness than its old counterpart. Both crack-deflection and crackbridging are the major energy dissipative processes for imparting a high toughness in bamboo.
The Reliability of Fragmentation Test
Authors: Dai Ying , Ji Xing , Ye Lin , Mai Yiu Wing
Published: March 2009

The single fiber fragmentation test has been continuously used to determine the
interfacial shear strength. However, the results of the tests were still suspected by some researchers. To evaluate the reliability of the fragmentation test, the stress singularity near the interface end of fragmentation is investigated. According to the local failure modes near the interface end of a fiber fragment, there are three cases of the interface end conditions to be considered for the fragmentation
tests: (A) fiber breaks only, without matrix cracking and de-bonding, (B) fiber breaks and matrix cracks, without interface de-bonding, (C) fiber breaks and interface de-bonds, with or without matrix cracking. After the singularity analysis of stress field near the interface end was depicted, it is obvious, that the interfacial shear strength given by the fragmentation test is not proper, because of that a stress singularity exists near the interface end.
Study of Hydroxyapatite/Al2O3 (anodic) Biocomposite Coating on Titanium with a Novel Multi-Step Method
Authors: He Li Ping , Wu Zhen Jun , Chen Zong Zhang , Mai Yiu Wing
Published: March 2009

A novel hydroxyapatite/Al2O3 (anodic) biocomposite coating has been successfully fabricated on titanium using a multi-step technique including physical vapor deposition (PVD), anodization, electrodeposition and hydrothermal treatment. Scanning electron microscopy (SEM), energy dispersive spectrometry (EDS), and X-ray diffraction (XRD) were employed to investigate
morphologies and compositions of the pre- and post-hydrothermally treated hydroxyapatite/Al2O3 (anodic) biocomposite coatings. The results showed that plate-like Ca-deficient hydroxyapatite coating was directly elctrodeposited onto anodic Al2O3 at a constant current density of 2.0 mA/cm2 using NaH2PO4 as the phosphorous source. The plate-like Ca-deficient hydroxyapatite was converted into network-like Ca-rich hydroxyapatite after hydrothermal treatment.
Numerical Simulation of Crack Formation in All Ceramic Dental Bridge
Authors: Li Qing , Ichim Ionut , Loughran Jeffery , Li Wei , Swain Michael , Kieser Jules
Published: March 2009

Ceramics have rapidly emerged as one of the major dental biomaterials in prosthodontics due to exceptional aesthetics and outstanding biocompatibility. However, a challenging aspect remaining is its higher failure rate due to brittleness, which has to a certain extent prevented the ceramics from fully replacing metals in such major dental restorations as multi-unit bridges. This paper aims at simulating the crack initiation and propagation in dental bridge. Unlike the existing studies with prescriptions of initial cracks, the numerical model presented herein will predict the progressive damage in the bridge structure which precedes crack initiation. This will then be followed by automatic crack insertion and subsequent crack growth within a continuum to discrete framework. It is found that the numerical simulation correlates well to the clinical and laboratory observations.
Partial Use of Pseudo-Ductile Cementitious Composites in Concrete Components to Resist Concentrated Stress
Authors: Leung Christopher K.Y. , Cheung Angus K.F. , Zhang Xiu Fang
Published: March 2009

The high pseudo-ductility of Engineered Cementitious Composites (ECC) makes it a particularly effective material to resist the propagation of cracks. In applications where failure is due to cracking initiated by localized stresses, the application of ECC around the stress concentrated region should result in significant improvement in the ultimate failure load. In this investigation, we will study the use of ECC in (i) the anchorage zone of post-tensioned concrete members, and (ii) the region around embedded anchor bolts in concrete blocks. For the first application, the
replacement of concrete with ECC at the anchorage zone is found to be very effective in increasing the load capacity under concentrated compression. Based on our test results, ECC can actually replace all or part of the conventional steel stirrups in resisting splitting failure at the anchorage zone. For embedded anchor bolts, the placement of a small ECC disc above the steel bolt can effectively delay the propagation of cone-shape failure and increase the pull-out force. Through the
present experimental program, we have illustrated the advantage of strategically applying ECC in critical region of structural components, to improve performance without significant increasing the material cost.
Molecular Dynamics Simulation of Nano-Indentation of Carbon Coated Monocrystalline Silicon
Authors: Cheong Wun Chet Davy , Zhang Liang Chi
Published: March 2009

This paper presents the molecular dynamics (MD) simulation of nano-indentation of diamond-like carbon (DLC) coating on silicon substrates. It is found that the mechanisms of nanoindentation of coated systems on the nanometre scale defers considerably from the same process on the micrometre scale. The coating thickness affects the mechanisms of plastic deformation both in the coating and the substrate.
In-Situ Synthesis of Metal Matrix Composite Coating with Laser Melting-Solidifying Processes
Authors: Geng Lin , Meng Qing Wu , Chen Yan Bin
Published: March 2009

In order to improve wear resistance of titanium alloy, with pre-placed B4C and NiCrBSi powders on Ti-6Al-4V substrate, a process of laser melting-solidifying metal matrix composite coating was studied. The coating was examined using XRD, SEM and EDS. A good metal matrix composite coating was obtained in a proper laser process. There is a metallurgical interface bonding between the coating and the substrate. During laser melting-solidifying process, high energy of laser
melted the pre-placed powders and a part of Ti-6Al-4V substrate, which made Ti extend into a melting pool. A reaction between Ti and B4C took place in the melting pool, which in-situ synthesized TiB2 and TiC reinforcements in the coating. The composite coating mainly consists of γ-Ni matrix, TiB2, TiC and CrB reinforcements. Microstructure of the reinforcements obtained using the laser melting-solidifying is not as same as that of reinforcements obtained using general producing methods. Due to high cooling rate of the melting pool, TiC nucleated primarily and grew
up in dendrite morphology from undercooled liquid. Encircling TiC, TiB2 precipitated later and grew up in hexagonal prism morphology. TiC and TiB2 formed an inlaid microstructure.
On the High Pure Alumina Composite Powder for Sintering at 1400°C, A Preliminary Investigation
Authors: Yu Pei Ching , Yen Fu Su
Published: March 2009

Pure alumina composite powders for low-temperature sintering purpose are examined. θ- and α- phase alumina particles with crystallite sizes 20 to 50 nm and 50 to 200 nm, respectively were mixed in an appropriate ratio. The composite powder can be easily sintered at temperatures as low as 1400oC, preparing high density and high pure alumina ceramics with grain size finer than 500 nm. Except the higher surface energy provided by the finer particle sizes, the performance of the powder can be attributed to the critical size phenomena occur during θ- and α- alumina phase transformation and the Furnas model that induced higher pacing density of the compact.
The Role of Particle Filtration in Industrial Scale EPD Processes
Authors: Hope Peter
Published: March 2009

Electrophoretic deposition or EPD is a well established method for creating decorative and
protective coatings and other structures on various electroconductive substrates. The formation of
these coatings and structures can be prejudiced by the presence of oversized or contaminant
particles as well as excess or contaminant electrolytes resulting in appearance and performance
problems in the final product. Nuisance particles come from diverse sources and are an inevitability
in industrial environments. Efficient and effective particle capture strategies are therefore essential.
In water-based EPD processes, control over the content electrolytes and other continuous phase
materials can be accomplished using tangential or cross-flow filtration where the permeate contains
the undesirable materials and can be treated or disposed of outside the system. But for particles and
other disperse phase materials, dead-end filtration techniques are required. Here the undesirable
materials are captured, concentrated and retained on the filter medium within the system. Disposal
only occurs as a result of discarding or treating the filter medium itself. Many types of dead-end
filtration media are commercially available. Retention size and materials of construction all have
relevance for system compatibility and effectiveness of particle capture. Practical experience shows
that selection of the correct type of particle filtration optimises process quality. Using inappropriate
filter media can be not just ineffective, but actively detrimental. This paper describes commonly
available particle filter systems and how they interact with industrial EPD process.
Simulation of Velocity Field of Two-Phase Flow for Gas and Liquid in the Abrasive Water Jet Nozzle
Authors: Hou Rong Guo , Huang Chuan Zhen , Wang Jun , Feng Yan Xia , Zhu Hong Tao
Published: March 2009

Simulation on velocity field of gas-liquid flow in the abrasive water jet nozzle was
studied by the computed fluid dynamics (CFD) software, The complex velocity field of the flow in
the abrasive water jet nozzle can be obtained by means of simulation. The study on the effect of the
nozzle inner cone angle on the velocity field shows that the cone angle affects the whirlpool’s
intension and position of the whirlpool in the nozzle of abrasive water jet (AWJ), and it also affects
velocity ‘s magnitude and distribution of the velocity on the cone surface.
Interference-Free Tool Path Generation for 5-Axis NC Machining with a Flat-End Cutter
Authors: Xie L. , Ruan X.Y. , Li M. , Wu Q.J.
Published: March 2009

A algorithm of interference free tool path generation for 5-axis NC machining with flat end cutter is presented. The approach includes: To obtain cutter location points from cutter contact points; interference pretreatment by convex box of NURBS surfaces and reducing check area; interference detection and tool-position correction based on mesh model while the interference problem is substituted with the relationship between tool and triangles. The algorithm is speed and reliable.