bluuebunny/crossref_metadata_2025 huggingface dataset:
Discussions on the Principle to Reduce the Sliding Fall Rock Impact Force against Protective Structure
Authors: Niu Wen Jie
Published: October 2011

Passive ductile protective system is widely used because of its better performance than buttress wall. This paper intends to determine the sliding fall rock impact force against a steel column at first. Then the rigid protective structure and ductile protective structure were compared. At last the hidden principle that passive ductile protective system can reduce the impact force was revealed. Results indicate that rings for energy dissipation in passive ductile protective system can significantly decrease the bending stiffness EI and decrease the impact force. Buttress wall encounters a lot more impact force than passive ductile protective system because of its bulkiness. Thus to ensure the buttress wall non-destructive, the thickness of buttress wall increases and it is not economic.
Seismic Response Analysis of Frame Structure on a Slope
Authors: Liu Li Ping , Liu Yong , Li Ying Min
Published: October 2011

Frame structure on a slope is a common kind of structure in a mountainous area. It can diminish the impact on environment, by avoiding to dug or fill the slope, using an opening platform, supported by beams and columns. Because the frame structure on a slope connects with the ground on different elevation level, it is evidently different from general frame structure in seismic design. Four sets of frame structure example on a slope sample are designed, with three opening floors connected with the ground on different elevation level, and three, six, nine, twelve upper floors correspondingly. The seismic responses characteristics of frames on a slope are studied in the paper from period, lateral deformation, seismic shear and so on, based on the analysis of the characteristics of frame structure on a slope. The main conclusions are as follows: the slope can enhance structural lateral stiffness to a certain extent; the opening floors connected with the ground on different elevation level, are not necessarily frail stories; the distribution of seismic force is uneven between the columns in the same floors which connect with the ground on different elevation level, and fixed columns undertake more than others, making them more fragile; the torsional effect is noticeable in the frame structure on a slope.
Seismic Assessment of Out-of-Code High-Rise Building Using Dynamic Nonlinear Analysis
Authors: Wu Xue Shu , Xue Wan Li , Rui Guo , Zhao Xu Qian , Li Gu
Published: October 2011

Seismic response of a high-rise building under rare earthquake is numerically investigated in the paper. The Height of the building is 266m, which goes beyond the limit of 150m in Chinese standard, so nonlinear analysis should be performed to investigate its elasto-plastic behaviors under severe earthquake excitations. In the finite-element model for analysis, beam-column members of the structure are simulated by beam elements, while the core tube is simulated by shell elements. The concrete damage plasticity model is used for concrete members, while the kinematic hardening rule is defined for steel beam-column members. Four sets of earthquake wave, including 3 sets of strong earthquake records and 1 set of artificial wave, are adopted in the analysis. The analysis results show that, under severe earthquakes, steel frame members and steel truss members in the strengthened floors keep elastic. Severe damages are detected in almost all coupling beams in the core tube, as well as shear-walls near strengthened stories, where lateral stiffness would decrease seriously. Through the investigation, it is also found that the largest story drift is less than the maximum allowable value in the Chinese code for seismic design of buildings. So it is concluded that the high-rise building will not collapse when the place is subjected to severe earthquakes. Besides, some design suggestions are proposed according to nonlinear dynamic analysis in the paper.
Mechanical Analysis for the Deck Pavement of Long-Span Steel Bridge
Authors: Wu Chun Ying , Zhang Zhi Xiang
Published: October 2011

The mechanical analysis is applied for the steel box girder bridge with orthotropic plate and pavement by means of Finite Element Method. The interaction between steel bridge and pavement on the long-span steel bridge is evaluated in three calculation stages. The emphasis of the analysis includes the mechanical characteristics and the influential factors of large components(cross diaphragm)and local components (U-shaped ribs). Considering the mechanical changes by the load of heavy-duty vehicles and heavy load with braking, the interfacial shear failure is studied for the main form of damage. In view of this major form of damage, this paper puts forward the corresponding mechanical analysis of the indicators.
Calculation of Cable Force for Long-Span Rib Arch Bridge Construction under Seasonal Ambient Temperature
Authors: Tian Wei Feng , Zhou Shui Xing , Alghabsha Ayad Thabet Saeed
Published: October 2011

Calculation of cable force under seasonal ambient temperature is the key and difficult problem in the construction of long-span rib arch bridge. It affects the final cable forces and deformations of arch rib after arch closure. Unstressed state control method is introduced in the construction of Daning River Bridge; unstressed qualities of ribs and unstressed length of cables can be obtained by optimization analysis of the maximum cantilever state in construction. According to unstressed state control method, the cable forces of each segment were calculated using the forward-iteration method. These results offer the basis for construction control, and guarantee the arch rib line and cable forces to meet the design requirements, and an arch closure with high precision.
Defects Detection in Concrete Structure with Infrared Thermal Imaging and Numerical Simulation
Authors: Xu Hong Guo , Shui Zhong He , Chen Bo , Chen Wei , Ding Sha
Published: October 2011

In this paper, infrared imaging and temperature sensor monitoring equipment are used to detect the defect of concrete. By means of experiment and numerical analysis, a nondestructive testing method for concrete based on infrared thermal imaging and the finite element simulation of temperature field was established. Experimental and simulation results show that infrared thermal imaging method and the finite element simulation of temperature field can effectively detect the defect in the sample. When combining such two methods together, the information of internal concrete structure can be revealed more comprehensively and accurately.
Screening Houseplants to Remove Ammonia from Indoor Air through Fumigation
Authors: Yang Hua , Liu Yan Ju , Shao Wei
Published: October 2011

It was the first in China that an attempt was made at screening houseplants to remove ammonia from indoor air. A fumigation system was used to screen 86 species and cultivars at 7.0 mg/m3 of ammonia in the initial screening experiment. Then 9 species of plants were chosen for replication experiment to confirm and quantify the removal effects. Plants in Ericales order showed a promising potential for removing ammonia and further study was suggested. Finally, Nephrolepis exaltata ‘Bostonniensis’ and Plectranthus oertendahlii were fumigated in day-and-night experiment. And the trends of removal rates of ammonia dependence on fumigation time were predicted as cubic functions for both species.
Effects of Mining Excavation on Surface Structures
Authors: Sun Chao , Wang Qing
Published: October 2011

In order to study the effect of mining excavation on planed structure on ground surface, the effect of certain mining excavation on ground stabtility was calculated by use of the advanced Ansys FEM computation program. The recults can not only provide ground deformation parameters for planned structure, but also give light for understanding the deformation mechanism of mining excavation.
Characterization of Silicone Rubber Reinforced with Conductive Powder
Authors: Stoian Elena Valentina
Published: October 2011

Conductive plastics are attracting more and more interest in electronics due to their light weight and inability to rust, which are common problems associated with metals. In this work silicone rubbers reinforced with conductive fillers have been fabricated for use in various applications in electronics, telecommunications, and electronics enclosures, or to protect human factor, namely protective clothing. This paper presents the results of experimental determinations concerning electromagnetic field attenuation in materials containing micro-particles of nanocarbon in their structure. To know the effect of shielding effectiveness of electromagnetic field electromagnetic absorbents were performed by transmission measurements of attenuation in the frequency range 1-18 GHz. The goal of present paper consits in the realization a composit material with polymeric matrix. The materials were characterized by transmision diminishing carried out, relative permittivity, compression test and electrical conductivity.
Pulse-Driving Based Magnetic Coupling Resonant Wireless Power Transmission System Research
Authors: Wang Qiang , Li Hong
Published: October 2011

This paper analyses and designs a kind of pulse-driving based wireless power transmission system via coupled magnetic resonances. It analyzes the influence of the related parameters on the transfer efficiency and transfer power of the system. The experiment tests the proposed wireless power transmission system, and the results show that the above relevant parameters should be comprehensively considered, in order to achieve the optimization design of the transmission efficiency or transmission power. The experiment results also show the validity of the theoretical analysis.
Application of Signal Processing for Motor Condition Monitoring Based on Filtered-Signals and Eliminated-Signals
Authors: Treetrong Juggrapong
Published: October 2011

This paper proposes new procedures of motor fault detection. The proposed methods are based on filtered-signals and eliminated-signals. Generally, the raw stator phase currents collected from the motors are firstly filtered in order to get rid of measurement noises. If the new signals are called “Filtered-Signals” and the signals eliminated from the raw stator phase currents are called “Eliminated-Signals”. The first proposed procedure is to detect the motor faults by spectrum of PSD slope from the filtered-signals. The second proposed procedure is to detect the motor faults by spectrum of the eliminated-signals. The both methods are tested on 3 different motor conditions: healthy, stator fault, and rotor fault motor at full load condition. The experiments show that the both methods can differentiate conditions clearly and they also can indicate the levels of fault severity. Thus, it can be effective when the both methods are applied simultaneously to analyze the faults
Electrostatic Control and New Device Handling Consideration for MEMS Manufacturing Process
Authors: Chakkaew Anusorn , Titiroongruang Wisut
Published: October 2011

Electrostatic potential and electrostatic discharge (ESD) has been a factory issue for years, not only limited to semiconductor-based electronic devices, but there are evidences that new devices from emerging technologies become sensitive which are MEMS and NEMS. This paper describes new electrostatic control and device handling solutions for critical electrostatic control environment for MEMS manufacturing processes. There are experiments of personnel grounding devices, device handling materials, and evaluation of static control surfaces.
Fabrication Optimization of Magnesium Az61 Alloys via Extrusion for High Productivity
Authors: Park Joon Sik , Kim Jeong Min , Song Young Ho , Hwan-Hong Byung , Cho Ye Won , Joo Sang Wook , Seok-Oh Joong
Published: October 2011

The nature of high specific strength compared with other structural materials has led to wide application of Mg alloys. However, Mg alloys often exhibit relatively low strength and/or low surface stability, which can limit the practical application of the alloy system. In order to achieve high strength, the commercial AZ61 alloys were extruded, so that the application of the alloy system can be extended towards new structural parts for requiring the light nature of the alloy system. In this study, a high temperature extrusion has been carried out for the commercial Mg alloys (AZ61). The productivity and mechanical properties of the alloy were critically affected by the extrusion conditions such as temperature, extrusion ratio and extrusion speed. The texture development and alloy strengths with respect to the extrusion conditions have been discussed in terms of microstructural observations and phase analyses.
Cyclic Test of Steel Plate Shear Wall Designed by PFI Method
Authors: Emami Fereshteh , Mofid Massood
Published: October 2011

In this paper, Plate Frame Interaction (PFI) developed by other researches for modeling Steel Plate Shear Wall (SPSW) is applied for designing a half-scale, single bay and one story SPSW. After designing of SPSW, one specimen is constructed accordingly. In order to determine the mechanical properties of steel, coupon test is performed; and then again theoretical relations based on PFI is re-checked. In this study, gravity loads are neglected and only seismic resistance of SPSW is considered. With cyclic lateral loading as quasi-static load, according to Acceptance Criteria for Cyclic Racking Shear Tests For Metal-Sheathed Shear Walls with Steel Framing (AC154) and obtaining its hysteretic loops, force displacement diagram of the specimen is determined. Comparison of theoretical and experimental results shows that ultimate strength of SPSW based on theoretical analysis is lower than that of experimental analysis. By the way, due to large deformation of beam during the applied loading, it is proposed that plastic moment of beam be get higher, rather than that of proposed quantity. However, through increasing of beam and column rigidity and attention to weak girder- strong column theory, it is estimated that ultimate strength, ductility and energy dissipation of steel shear wall will significantly improve.
SIMS Study of 30keV H+ Ion-Implanted n-GaAs
Authors: Sivabharathy M. , Jeyanthinath M. , Vines Lasse , Svensson Bengt Gunnar , Ramachandran K.
Published: October 2011

A detailed analysis on the depth profiles of 30 keV H+ ion implanted n-GaAs for various doses from 1014 to 1017 cm-2 was carried by using Secondary ion mass spectrometry (SIMS), to identify the buried amorphous layer. The results are correlated with Raman and XRD strain parameter studies. Various thermal parameters are computed for the 30 keV H+ ion implanted n-GaAs and SIMS study reported for the first time.
On the Application of the Photoacoustic Method for the Determination of the Thermal Properties of Heat-Treated and Annealed Al-Li Alloy
Authors: Sivabharathy M. , Palanichamy P. , Vasudevan M. , Kalyanasundaram P. , Ramachandran K.
Published: October 2011

In this paper, the application of photoacoustic methods to study thermal properties of Al-Li alloy is described. The photoacoustic measurements are carried out for thermal properties on Al-Li alloy and studied for various thicknesses. The theoretical basis for quantitative measurements is discussed together with the advantages and limitations of these methods as compared with conventional measurements. Applications to spectroscopic and depth-profile analysis and also to thermal property measurements in Al-Li samples heat-treated at 755K per hour and annealed at 505K are discussed. The results are compared with literature values, and discussed.
Evaluation of the Degradation Properties of Carbonate Substituted Hydroxyapatite-Poly(ε-caprolactone) Composites
Authors: Ege Duygu , Lee Koonyang , Bismarck Alexandre , Best Serena , Cameron Ruth
Published: October 2011

The aim of this work is to produce and characterise carbonate substituted hydroxyapatite (CHA) reinforced polycaprolactone (PCL) nanocomposites with a controlled degradation rate in order to match the rate of bone in-growth. The ideal degradation time for this purpose is estimated to be around 5-6 months however, in vivo, PCL degrades over a period of 2 to 3 years. It has been reported that NaOH surface treatment can accelerate the degradation of PCL [1-3]. In order to further modify the degradation rate of PCL, the effects of the incorporation of different volume fractions of CHA in samples surface treated with NaOH was investigated. CHA was produced by wet chemical synthesis. Samples comprising 8, 19, 25 wt% uncalcined CHA-PCL composites were produced by twin screw extrusion which were then injection moulded into cylinders. In order to accelerate the degradation rate of PCL, it was surface treated with 5 M NaOH for 3 days prior to PBS studies. The degradation profile was examined by % weight loss and % water uptake measurements. NaOH treatment was observed to erode the polymer surface and the polymer-filler interface. On subsequently degrading the pre-treated samples in PBS, it was observed that with increasing fraction of CHA, the degradation rate in PBS of the sample increased. Up to 8 wt % CHA filler there appeared to be little change in the degradation properties of the NaOH treated samples with the onset occurring after 60 days. However there was a marked acceleration of degradation for samples containing 19 wt% when degradation appeared to occur immediately. In conclusion, the addition of CHA significantly affects the behaviour of PCL.
Calcite Bone Substitute Prepared from Calcium Hydroxide Compact Using Heat-Treatment under Carbon Dioxide Atmosphere
Authors: Tsuru Kanji , Otsu Akihiro , Maruta Michito , Valanezhad Alireza , Kawachi Giichiro , Takeuchi Akari , Matsuya Shigeki , Kunio Ishikawa
Published: October 2011

The purpose of this study is to investigate whether calcite blocks with high mechanical property could be obtained for a short period from calcium hydroxide (Ca(OH)2) compact using heat-treatment under carbon dioxide (CO2) atmosphere. The Ca(OH)2 disks compacted with different pressure was heated at different temperature ranging from 200°C to 800°C for an hour under CO2 atmosphere. From the X-ray diffractometry, Ca(OH)2 converted into calcite along with the rise of the heating temperature. Small amount of unreacted Ca(OH)2 remained in samples heated at 600°C whereas samples treated at 800°C converted to calcite with very small amount of calcium oxide. The diametral tensile strength (DTS) value increased with the rise of heating temperature up to 600°C then decreased down to 800°C. Meanwhile, the porosity decreased with the rise of heating temperature up to 600°C then slightly increased up to 800°C. From the scanning electron microscope observation, grains grew bigger along with the rise of heating temperature. Intergranular space between grains decreased from 200°C to 600°C. The highest DTS value (14 MPa±1.3) at 600°C could be the result of lesser intergranular space due to sintering.
Preparation and Characterization of Calcium Phosphate Crystals by Precursor Thermolysis Method
Authors: Wang Xin Yu , Han Ying Chao , Li Shi Pu
Published: October 2011

In this paper, a simple precursor thermolysis method is applied to prepare calcium phosphate crystals and macroporous ceramic. The phase composition of sample was determined by XRD and the morphology of sample was observed by TEM and SEM. The macroporous ceramic was observed by 3D digital microscope. Results show that 25-100 nm HAP nanocrystals were obtained at 500°C and HAP rod-like crystals with an equivalent diameter of about 0.50-1.6μm and a length of about 5-10μm were obtained at 700°C. In addition, about 100 nm β-TCP nanoparticles were also obtained at 900°C. The colloidal precursors can also be used to fabricate macroporous calcium phosphate ceramic. The size of pores is about 100-200μm. Pores are well opened and interconnected in three dimensions.
Simultaneous Insertion of Mg2+, Sr2+ and Mn2+ Ions into Hydroxyapatite Structure
Authors: Pereira Moreira Mirna , Teixeira da Silva Aragão Victor , de Almeida Soares Gloria Dulce , Araujo dos Santos Euler
Published: October 2011

The current trends in bioactive ceramics point out the ionic substitution in hydroxyapatite (HA) as a concrete way to create new active ceramics with a high developed biomimetic character. Accordingly, our objective in this work was investigating the effects of the simultaneous replacement of Ca2+ ions for Mg2+, Sr2+ and Mn2+ into the crystalline structure of HA.
Preparation of Submicron-Sized Hydroxyapatite Powders by Spray Pyrolysis
Authors: Cho Jung Sang , Rhee Sang Hoon
Published: October 2011

Dense and submicron-sized hydroxyapatite powders were synthesized through spray pyrolysis of calcium phosphate solution with polyethylene glycol (PEG). Irregular shaped and fragile hydroxyapatite aggregates, and spherical and hollow hydroxyapatite particles were obtained after spray pyrolysis at 1100 °C when using calcium phosphate solution with and without PEG, respectively. After dewaxing at 650 °C for 3 hours, the hydroxyapatite aggregates were broken into submicron-sized particles whereas micron-sized spherical hollow particles were almost intact. The relative densities of hydroxyapatite disks made by submicron and micron sized hydroxyapatite particles were about 90% and 81%, respectively, after sintering at 1110 °C for 3 hours. The results were explained in terms of the disintegrating function of carbon which was previously formed among the hydroxyapatite aggregates by the decomposition of PEG during spray pyrolysis.
The Effect of Microwave Irradiation on Structural and Mechanical Properties of Nano-Structured Bone-Like Carbonated Hydroxyapatite
Authors: Khorami Mina , Hesaraki Saeed , Ebadzadeh Touradj , Farhangdoust Sajad , Zamanian Ali
Published: October 2011

Nanocrystalline carbonated hydroxyapatite was produced through hydraulic conversion of calcium phosphate cement in simulated body fluid (SBF) and then heated in a microwave oven at 1000-1250 °C. The phase composition and microstructures were evaluated, before and after the thermal processing, using XRD and SEM, respectively. Total porosity and bending strength of the samples were also tested. Proliferation and morphology of osteoblastic cells on samples were evaluated using MTT method. Limited growth of apatite crystals was observed by the thermal treatment in which the samples exhibited a crystal size of ~ 150 nm at heating temperature of 1250 º. Based on the results, the microwave irradiation led to a little change in phase composition of carbonated apatite and slight amount of β-TCP phase was found together with large amount of apatite. The sample irradiated at 1250 °C formed more dense material having bending strength value up to 130 % that of unheated sample. The in vitro cell studies showed that the microwave irradiated samples could provide adequate cell proliferation and attachment.
Osseoinduction Evaluation of Hydroxyapatite and Zinc Containing Hydroxyapatite Granules in Rabbits
Authors: Nascimento L. , Medeiros M. , Calasans-Maia J. , Alves A. , Rossi Antonella M. , Alves Gutemberg , Granjeiro J.M. , Calasans-Maia M.
Published: October 2011

This study investigated the osteoinductive potential of granules of stoichiometric hydroxyapatite (HA) and 0.5% zinc containing hydroxyapatite (ZnHA) in intramuscular (IM) site of rabbit’s abdomen. The biomaterials were both used in granular form, with 75% porosity and particle diameter between 450 and 500μm, sintered at 1100°C. Both materials performed adequately on a multiparametric in vitro cytocompatibility assay, indicating their suitability for in vivo testing. After approval by the Ethics Commission on Teaching and Research in Animals, fifteen rabbits were submitted to general anesthesia, incision and tissue dilatation, and a small site was created for HA (right incision) and ZnHA (left incision) intramuscular implantation. The animals were killed after 2, 4 and 12 weeks for biomaterials and surrounding tissues removal. Histological analysis after 2 weeks revealed the presence of granulation tissue surrounding biomaterials with multinucleated giant cells and no newly formed bone for both materials. After 4 weeks there was fibrous tissue involving the material and few inflammatory cells. Following 12 weeks it was observed the presence of connective tissue surrounding the biomaterial, cellularized enough for the two experimental groups, but it was not observed the presence of bone matrix associated with the biomaterials. We conclude that both biomaterials are cytocompatible and did not present the property of osseoinduction after 12 weeks of implantation.
Silver-Doped Apatite as a Bioactive and an Antimicrobial Bone Material
Authors: Thian Eng San , Lim P.N. , Shi Z. , Tay B.Y. , Neoh K.G.
Published: October 2011

Phase-pure nanostructured silver-doped hydroxyapatite (nAgHA) of various Ag contents was synthesised. These nAgHA were then evaluated in-vitro using human mesenchymal stem cells (hMSCs) and Escherichia coli (E. coli). Results revealed that hMSCs grew generally well on all nAgHA at all time points. In addition, fewer E. coli were seen attaching on the surface of all nAgHA. Hence, this work demonstrated that nAgHA offers considerable potential as a biomaterial.
Cytocompatibility and Structural Arrangement of the Collagen Fibers: An In Vitro and In Vivo Evaluation of 5% Zinc Containing Hydroxyapatite Granules
Authors: Fernandes G.V.O. , Cortês J.A. , Melo B.R. , Rossi Antonella M. , Granjeiro J.M. , Calasans-Maia Mônica Diuana , Alves Gutemberg
Published: October 2011

Hydroxyapatite (HA) is one of the most employed materials for bone therapy due to its structural similarity with bone, its biocompatibility and physicochemical properties. Additionally, HA performance may be improved by ionic substitution of calcium with divalent bioactive metallic cations such as zinc. In this context, zinc incorporation into HA have been well studied, in spite of conflicting results regarding its biocompatibility: while previous reports on in vitro cytocompatibility have described 5% zinc containing HA (ZnHA) as slightly cytotoxic, this material presented an excellent response on in vivo studies. In order to bring more information on ZnHA biocompatibility, we performed a multiparametric assay evaluating sequentially on the same cells three different viability parameters: mitochondrial activity (XTT), membrane integrity (Neutral Red) and cell density (Crystal Violet Dye Exclusion test). Additionally, we intended to complement the existing data on ZnHA in vivo performance, by assessing its ability to affect the arrangement of collagen fibers on the grafted area, an important indicative of bone maturation. MC3T3-E1 cells were exposed to 24-hours extracts of ZnHA or stoichiometric HA on culture medium (DMEM) and cell viability was assayed. ZnHA was very cytocompatible, since the levels of viable cells on all 3 tests were similar to the HA and polystyrene (negative control) extracts, but significantly higher than cells treated with 4% phenol (positive control). For the in vivo studies, critical size defects in rats calvaria were filled with HA or ZnHA granules. The histological evaluation after 30 and 180 days revealed an increase along time. Event tough ZnHA is cytocompatible the presence of Zn was unable to alter the interaction between collagen fibers and the mineral bone phase, as compared to stoichiometric HA.
Biological Behavior of Chitosan-Fibroin-Hydroxyapatite Scaffolds with STRO+1A, MC3T3-E1 and SaOS2 Cells
Authors: Lima Paulo Autran Leite , Tavares Débora dos Santos , de Almeida Soares Gloria Dulce , Anselme Karine , Almeida Luiz Eduardo
Published: October 2011

Hybrid composites with chitosan (CHI), silk fibroin (SF) and hydroxyapatite (HA) are biocompatible and attractive for bone engineering applications. The objective of this work was to evaluate in vitro cells behavior in contact with CHI-SF-HA scaffolds. The scaffolds were produced from a chitosan solution (2%wt) with SF (1%wt) and HA powders (1%wt) in acetic acid. This solution was molded, frozen and the scaffolds were freeze-dried, crosslinked, and then, submitted to in vitro tests with STRO+1A, MC3T3-E1 and SaOS2 cells under static conditions for 7, 14 and 21 days. The scaffolds were characterized through X-ray diffraction (XRD), infrared spectroscopy (FTIR) and scanning electron microscopy with energy dispersive spectroscopy (SEM/EDS). Cell viability and activity was assessed by MTT reduction and alkaline phosphate (ALP) activity detection. XRD patterns showed characteristic peaks at 8.8º, 20.3º and 24.6º (corresponding to SF) and peaks at 31.8º, 32.2º and 32.9º (corresponding to HA). The FTIR presented characteristic bands of the amide groups (SF) and of the phosphate and carbonate groups (HA). The EDS showed the presence of the C, O, N, P and Ca elements. SEM analyses showed the scaffold morphology, and indicated cell growth across the surface of the sample. The STRO+1A and MC3T3-E1 cells presented the best cell adhesion. MTT assay showed an increase of the cell number with time and the 21 days analyses showed the best proliferation for SaOS2 cells (p<0.01), STRO+1A cells (p<0.04) and MC3T3-E1 cells, respectively. The ALP activity was higher at 21 days for all cells types and the SaOS2 cells presented the best results in all analyses (p<0.01). Molecular studies are under progress to evaluate more deeply the biocompatibility of these scaffolds. Moreover, dynamic studies in bioreactor are under progress to improve cell colonization inside scaffolds.
Multinucleated Giant Cells for Biomaterials - Ceramics and Dentin Collagen -
Authors: Murata Masaru , Akazawa T. , Hino J. , Tazaki J. , Ito K. , Fujii M. , Shibata T. , Arisue M.
Published: October 2011

Bone and dentin consist of hydroxyapatite, collagen and body fluid. From biological points of view, we have been focusing on HAp and collagen materials for bone regeneration. The aim of this study is to estimate the appearance of multinuclear giant cells for non-organic (functionally graded HAp: fg-HAp) and organic materials (demineralized dentin matrix: DDM), histologically. The fg-HAp ceramic: Biomimetic fg-HAp was designed by using the partial dissolution-precipitation methods. The fg-HAp with micro-pores of 10-160 nm had larger specific surface areas (30-40 m2･g-1) than the synthetic HAp. Acid- insoluble dentin matrix (DDM): Human teeth were crushed under the cooling, completely demineralized in 0.026N HNO3 solution, and dried. The materials were implanted into the subcutaneous tissues (Wistar rats, 4 week-old, male), and removed at 1 and 4 weeks after the operations. Multinucleated giant cells were counted in the H-E sections. Giant cells predominantly appeared on the biodegradable micro-crystals at 1 week. The number of giant cells was more numerous in fg-HAp than in DDM. There was a significant difference in the cell number between fg-HAp and DDM. The absorption mechanism of fg-HAp should be predominantly cellular phagocytosis, while that of DDM might be predominantly enzymatic digestion. These data support the hypothesis that the biological HAp crystals may function as mineral signal in the recruitment and differentiation of multinucleated giant cells.
Calcium Phosphate Bone Cement (CPBC): Development, Commercialization and Future Challenges
Authors: Tofighi Aliassghar
Published: October 2011

The first generation of synthetic bone substitute materials, hydroxyapatite (or HA), was initially investigated as a “non self-hardening” biomaterial for remodeling of bone defects. CPBCs concepts were used as a platform to initiate a second generation of injectable, self-hardening cement. The variety of CPBC’s chemical composition leads to a better understanding of their mechanism of reaction and their proposed classification: acid-base, mono-component and hydrolysable. After hydration, mixing, and full chemical reaction, these cements have the ability to precipitate different end products (e.g. HA, calcium deficient apatite, carbonated apatite, brushite, etc.). In fact, the initial idea of having higher mechanical performance (>50 MPa in compression) for a bone void filler application was abandoned and has led to a greater focus on cement fast-hardening (<15 min), higher total porosity (>60%), extended performance of injectability (8 to 22 G), fast resorbability (< 2 years) and user-friendliness for the clinicians. A new CPBC combination (cement plus additives) has particularly improved rheological and biointegrity performance. A hybrid of CPBC-DBM (Demineralized Bone Matrix) has also added an osteoinductivity performance to the initial osteoconductive CPBC.This paper will propose a comparison of the chemical composition, reaction, and performance characteristics of major commercially available CPBC products. Furthermore, it will describe today’s surgeon’s CPBC needs as bone substitute materials for different clinical applications. Finally, we will discuss what we learned so far, how we can resolve several clinical impacts & product recall, and how we believe CPBC designers can meet development challenges, and users’ specific requirements.
Antibacterial Activity In Vitro of the Developed Glass Ionomer Cements
Authors: Karaś Joanna , Olszyna Andrzej Roman , Zaczyńska Ewa , Czarny Anna , Szamałek Krzysztof
Published: October 2011

The purpose of the study was to identify the influence of the amount of fluoride release from glass ionomer cements on survival of bacterial strains responsible for the development of secondary caries. All developed cements had an antibacterial impact on the strains used in the study. The study demonstrated that the cements exhibit greater antibacterial activity against Streptococcus mutans than Streptococcus sanguinis. The numbers of bacteria count in cultures on the developed cements were approximately 10 times lower compared to the control culture after 24 h, 48 h, 72 h and 7 days. The developed cements had initially (1-2 days) greater antibacterial impact against the strains used in the study, which corresponds to the greatest daily amount of fluoride released from the cements. Following the initial period, the antibacterial activity of all the cements remained roughly at the same level.
Mechanical Properties of Calcium Phosphate Cements (CPC) for Bone Substitution: Influence of Fabrication and Microstructure
Authors: Zhang Jing Tao , Tancret Franck , Bouler Jean Michel
Published: October 2011

Calcium phosphate cements have been widely used in medical and dental applications for decades. However, their intrinsic high brittleness and low strength prohibit their use in many stress-bearing locations, which would require an improvement in mechanical properties. The influence of microstructural parameters on the latter have nevertheless barely been investigated in a systematic manner. Furthermore, due to their inferior reproducibility which is sensitive to the variations introduced during the preparation and the way they are measured, mechanical properties of CPC cannot simply be characterized using mean values, but request a more reliable method. In this aim, apatite cements have been fabricated by mixing liquid and powders based on α-TCP (α-tricalcium phosphate), and their mechanical properties have been measured (Young’s modulus, fracture toughness, compressive strength and flexural strength) in wet environment as a function of various parameters (liquid-to-powder ratio; amount and morphology of porosity, including macropores created by porogens). The reliability of compressive strength of CPC is analysed using Weibull statistics. The above results indicate that fabrication and microstructural features of CPC significantly influence their mechanical properties.
Effect of Surface Charge on the Apatite Mineralization Process
Authors: Carvalho Vilany Santos , Araujo dos Santos Euler , Resende Cristiane Xavier
Published: October 2011

In this current study it was investigated the influence of positively and negatively charged surfaces on apatite nucleation process from a supersaturate solution containing calcium and phosphorus (SBF solution). Glass slides were coated with polyelectrolytes thin films using a standard method to produce self-assembled monolayers (SAMs). Slides without treatment were used as control. Positive and negative glass slides were soaking in simulated body fluid (1.5 SBF) for 2, 8, 24 and 96 hours. The surfaces were characterized by scanning electron microscopy (SEM). Accordingly, the apatite mineralization was observed on all surfaces, no matter the surface charge. No remarkable morphological changes were verified between the precipitate in both positive and negative surfaces. It suggests that the crystal growth is not influenced by the initial attraction between either a negative surface and Ca2+ ions or a positive one and PO43- ions.
Comparison of Microstructures of Bovine Hydroxyapatite and Sol-Gel Derived Porous Alumina-Hydroxyapatite Biocomposite Powders
Authors: Yelten Azade , Yilmaz Suat , Oktar F.N.
Published: October 2011

Alumina (α-Al2O3) and hydroxyapatite (Ca10(PO4)6(OH)2) are biocompatible ceramic materials. Alumina is described as “bioinert” while hydroxyapatite as “bioactive”. These ceramics can be used in production of orthopedic prostheses, dental implants and bone filling materials either separately or in composite form. Especially porous materials attract attention due to their supportive structure for cell and tissue growth/development.Alumina was derived via sol-gel method. Firstly, boehmite (AlOOH) sol was produced by hydrolyzing the starting material, aluminium iso-propoxide (AIP, Al(OC3H7)3). Then this sol was mixed with hydroxyapatite powders (Bovine Hydroxyapatite, BHA) obtained from bovine bones. Subsequently, the mixture was gelated at 110 °C for 3 hours and the resulting gel mixture was heat treated at 1300 °C for 2 hours. BHA powders were not synthetic and added as 10 and 30 wt.% of AIP to the boehmite sol. Irregular shape of the powders produced after the heat treatment was interpreted as a sign of porosity.SEM-EDS and XRD characterization studies were performed on heat treated powders. XRD results showed that powders were composed of α-alumina and apatite based phases such as tricalcium phosphate and hydroxyapatite. SEM images of the composite powders indicated that neck bonds were not formed between α-alumina and apatite based phases. Comparison of SEM images and EDS results of pure BHA and composite powders revealed that pure BHA powders possess granular particle shape. Furthermore, needle shaped alumina particles were observed in the composite sample with 10 wt.% BHA. Finally, it has been found out that alumina particles were placed layer by layer in the composite powders with 30 wt.% BHA.
Gradient Organic Inorganic Nanocomposites for Tissue Repair at the Cartilage/Bone Interface
Authors: Aviv Meital Gavriel , Amit Boaz , Yayon Avner , Garti Nissim , Füredi-Milhofer Helga
Published: October 2011

Damages to articular cartilage that are caused by trauma, age-related diseases (arthritis, arthrosis) and/or physical stress pose major medical problems. A possible solution is to introduce a biodegradable sponge-like scaffold containing cartilage-forming cells. In the current work we developed a model for a partially calcified functional biomedical membrane with a gradient of calcium phosphate crystal density to form the interface between bone and a sponge-like cell containing scaffold for cartilage regeneration. The membrane consists of a biocompatible, biodegradable, partially calcified hydrogel, in our case gelatin was used. One part is an organic-inorganic nanocomposite consisting of nanocrystalline calcium phosphate particles, formed in situ within the hydrogel, while the other part is the hydrogel without inorganic crystals. The experimental method used was one-dimensional single diffusion. Gelatin gels containing calcium or phosphate ions, respectively, were exposed from the upper side to a solution of the other constituent ion (i.e. a sodium phosphate solution was allowed to diffuse into a calcium containing gel and vice versa). Scanning electron microscopy (E-SEM), EDX, XRD and ATR-FTIR spectroscopy confirmed the existence within the gel of a density gradient of carbonate apatite crystals, with a dense top layer extending several microns into the gel. Ca/P atomic ratios were in the range characteristic of calcium deficient apatites. The effect of different experimental parameters on the calcification process within the gelatin membranes is discussed.
Comparison of Mechanical Properties of Sheep Hydroxyapatite (SHA) and Commercial Synthetic Hydroxyapatite (CSHA)-MgO Composites
Authors: Demirkol N. , Meydanoglu Onur , Gokce Hasan , Oktar F.N. , Kayali E.S.
Published: October 2011

In this study, microstructures and mechanical properties of sheep hydroxyapatite (SHA) and commercial synthetic hydroxyapatite (CSHA)-MgO composites were investigated. The production of hydroxyapatite (HA) from natural sources is preferred due to economical and time saving reasons. The goal of development of SHA and CSHA based MgO composites is to improve mechanical properties of HA. SHA and CSHA composites were prepared with the addition of different amounts of MgO and sintered at the temperature range of 1000-1300 °C. The physical and mechanical properties were determined by measuring density, compression strength and Vickers microhardness (HV). Structural characterization was carried out with X-ray diffraction (XRD) and scanning electron microscopy (SEM) studies. In all composites, mean density values and mechanical properties increased with increasing sintering temperature. The increase of MgO content in SHA-MgO composites showed better mechanical properties in contrast to CSHA-MgO composites. Although the highest hardness and compression strength values were obtained at the SHA-10wt% MgO composite sintered at 1300°C, higher hardness and compression strength values were achieved with 5 wt% MgO addition at the CSHA-MgO composites when compared to SHA-MgO composites sintered between 1000-1200°C.
Grafting Materials for Major Sinus Lift
Authors: Ratiu Cristian , Cavalu Simona , Miclaus V. , Ober C. , Ratiu I. , Ponta O.
Published: October 2011

The materials used for major sinus lift varies from autogenous or allogenous bone, to animal origin (xenograft) bone or synthetic (alloplastic) materials. A combination of bone substitutes, alloplastic graft with allogenic or xenogenic bone seems to give satisfactory results in terms of new bone formation and the long-term implant success rate. On the other hand, using PRP (Platelet Rich Plasma) mixed with bone substitutes seems to enhance graft vascularization and osseous regeneration, as well as faster healing. The novel sinus lift technique with PRGF (Plasma rich in Growth Factors) has demonstrated significant development of new bone, minimizing any complications in the event of Scheneiderian membrane perforation. The present study compares two clinical cases where major sinus lifts were performed using as regenerative material xenograft bone and porous titanium mixed with PRGF.
Ag-Doped Sol-Gel Derived Novel Composite Materials for Dental Applications
Authors: Chatzistavrou Xanthippi , Paraskevopoulos Konstantinos M. , Salih Vehid , Boccaccini Aldo Roberto , Kasuga Toshihiro
Published: October 2011

The aim of this work was to improve a newly developed family of glass-ceramic composite materials by incorporating silver ions in the ceramic structure, thus developing new Ag-doped materials with the ability of showing antibacterial activity for dental applications. Two different sol-gel methodologies were applied for the fabrication of colorless, homogenous and chemically durable materials which can slowly release silver ion for relatively long periods. Both methods led to the successful development of Ag-doped glass-ceramics with silver ions incorporated in the structure that can slowly release in buffer solution, during a period of 45 days. The potential, application of these materials involve the development of bioactive surfaces on dental substrates which can seal the marginal gap creating a bacterial free environment finally supporting the success of dental restorations.
Mechanical Properties of CAD/CAM Manufactured and Prefabricated Endodontic Posts
Authors: Sinmazisik Gulden , Tarcin Bilge , Gülmez Turgut
Published: October 2011

The aim of this study was to evaluate the stiffness, elastic limit and strength of CAD/CAM manufactured metal and zirconia posts in comparison to prefabricated zirconia and glass-fiber posts. Materials and methods: Four types of posts were investigated in this study (n=40). Prefabricated posts made of zirconia (Cosmopost) and glass-fiber reinforced composite (FRC Postec Plus), and Cr-Co (Magnum Lucens) and zirconia (Zirkonzahn) posts manufactured with a CAD/CAM system were used. Artificial root canals with similar diameters to those of the posts were drilled on a stainless steel metal block and the posts were cemented with a self-etch/self-adhesive dual cure resin cement (Totalcem). The posts were loaded in a universal testing device at an inclination of 135 degrees at a crosshead speed of 1mm/min. The force-deflection curves were recorded, and stiffness, elastic limit and strength of the posts were determined. Data were analyzed statistically using Mann Whitney U and Kruskall Wallis tests.Results: The difference between the strength, elastic limit and also stiffness values of the groups was statistically highly significant (p<0.01). CAD/CAM Cr-Co posts showed the highest values of strength, elastic limit and stiffness amongst all the posts investigated. CAD/CAM zirconia posts had the lowest values of strength, and FRC had the lowest values of elastic limit and stiffness. Cosmopost had higher values of elastic limit and stiffness compared to CAD/CAM zirconia posts.Conclusions: If an endodontic post restoration is required, functional load and aesthetics should be considered in addition to mechanical properties of the material selected.
Self Hardening Macroporous Biphasic Calcium Phosphate Bone Void Filler for Bone Reconstruction; Animal Study and Human Data
Authors: Daculsi Guy , Durand Marlene , Hauger O. , Elodie Seris , Borget Pascal , LeGeros Racquel Z. , Le Huec J.C.
Published: October 2011

Due to the lack of macroporosity in current available Calcium Phosphate cement used in osteoarticular surgery, Micro and Macroporous Biphasic CaP Cement (MCPC™) was developed. The MCPC™ concept was the association of a settable and a fast resorbable matrix and a sieved fraction of microporous biphasic calcium phosphate (BCP) granules, recognized for the high osteoconductive and osteogenic properties. During the resorption of the matrix, a porous structure is created and the osteoconductive effect of the granules promotes the bone ingrowth. A goat preclinical study was realized to evaluate the efficacy of MCPC™ for C3 and C4 vertebral body filling defects during 6 months. Bone remodelling was evidenced demonstrating bone ingrowth at the expense of the cement and surrounding the residual BCP granules. Bone trabeculae were observed coming from the spongious bone to the implant site. Human vertebral body filling cases demonstrated the biocompatibility and the safety of MCPC™ for bone reconstruction. Results of this study demonstrated the importance of special combination of calcium phosphate granules in the MCPC™ to provide macroporosity and scaffolding for newly formed bone.