bluuebunny/crossref_metadata_2025 huggingface dataset:
Comparison of the Mechanical Properties of Thai Nonlatex with Commercial Latex Orthodontic Elastics for Orthodontic Application
Authors: Dechkunakorn Surachai , Jittanonda Vantida , Anuwongnukroh Niwat , Suddhasthira Theeralaksna , Wichai Wassana , Tua-Ngam Peerapong
Published: October 2011

Natural rubber latex products are used as orthodontic elastics but the increased incidence of latex allergies has led to the development of nonlatex orthodontic products. In Thailand, commercial nonlatex orthodontic elastics are not readily available and the cost of imported non latex products is relatively high. Thai non latex elasticshave been developedas alternative orthodontic products for latex-allergic patients and their costs are affordable.Objective: Tocomparethe mechanical properties of Thai nonlatex elastics with commercial natural latex orthodontic elastics for orthodontic application. Materials and Methods: Samples of imported latex orthodontic elastics [Ormco(USA), G&H (USA), Creative Orthodontics (China), Tomy Elastics (Japan)]were selected to compare their dimensional characteristics and mechanical properties with Thai non latex elastics. The dimensional characteristics of the elastics (i.e., inner diameter, cross-sectional thickness and cross-sectional area) were determined and their mechanical properties [(i.e., initial extension force (F0), 24 h- residual force (F24), percentage of force loss, force exerted at 3x the specified inner diameter(F3xID) and breaking force] were tested next. The data were analyzed with One-way ANOVA and multiple comparison by Tukey’s test was used among groups (p<0.05). Results:Significant differences of dimensional characteristics and mechanical properties were found among each brand of elastics. Thai non latex elastics had significantly different mechanical properties from natural latex elastics as reported in previous studies(p<0.05). Thai non latex elastics had the lowest initial extension force (0.82N), 24-h residual force (0.56 N) and breaking force (19.63 N, 8.183 MPa) but the highest percentage of force loss after 24 h (32.62%).However, the percentage of force loss was higher than commercial non latexelastics as previously reported. Conclusion:Thai nonlatex elastics were not comparable to those of the latex elasticsregardingmechanical properties;however,these are acceptable for orthodontic application. Therefore, the clinical selection of elastics should be based on the patient’s medical history and the specific mechanical properties of the type of elastic. Thai nonlatex orthodontic elastics can be a valid alternativefor patients with latex allergy in Thailand and this study contributes to the continuous development of Thai nonlatex orthodontic elastics.
Ab Initio Study on the Structural Stability and Elastic Properties of Tungsten Borides with Hexagonal Structure
Authors: Xu Xue Wen , Yu Xiao , Hu Long , Lu Zun Ming , Tang Cheng Chun
Published: October 2011

In this paper, we have investigated the structural stability and elastic properties of four tungsten borides with the hexagonal structure by the first principle calculations. The results indicated that m-WB2 and c-WB2 were stable in thermodynamics and structure. The stiffness coefficient and modulus of the stable compounds were also calculated and were compared with those of the typical MAX ceramics. The computed ratios of bulk-to-shear-modulus and bulk-modulus-to-c44 showed that m-WB2 and c-WB2 were ductile.
Structural and Optical Properties of Nanostructured Zn1-XMnxO Thin Films
Authors: Rashid Affa Rozana Abdul , Menon P. Susthitha , Shaari S.
Published: October 2011

Mn doped ZnO films with different doping concentration were synthesized by sol gel method using the spin coating technique. Zn1-xMnxO thin films are prepared using 2-methoxyethanol solution of zinc acetate dehydrate and manganese acetate tetrahydrate. The quantity of Mn in the sol was synthesized with undoped ZnO, 2%, 4%, 6% and 8 % of Mn doped ZnO with an annealing temperature of 500°C. The FESEM images showed many spherical shaped nanoparticles on the cross-sectional of the films. The optical properties were characterized using UV-Vis where the transmittance and band gap value were affected by certain amount of Mn concentration. These films achieve tunable band gap characteristics by means of changing the dopant concentration. It shows an initial decrease of band gap for small concentrations of Mn, followed by an increase at higher Mn doping concentrations.
Study on the Principle of Tunnel Collapse Treatment and its Application
Authors: Mu Lin , Huo Zhen Long , Fan Yong Hui
Published: October 2011

Collapse of crowm broked out with large water gushing at working face during driving tunnel in Ming Ya Zi tunnel’s right tube. According to engineering geology condition and analysis of causes of collapse, double-deck prior ductile grouting reinforcement technique was applied in tunneling surrounding rock consolidation based on the strong pre-support theory.And the result of treatment was successful.Thus,guiding the work of tunnel collapse treatment by strong pre-support theory was proved reasonably and effectively.
Analysis of the Force Characteristics of Stem to the Roots by SM Solver
Authors: Guo Feng Ying , Liu Jing , Ping Li , Wang Cheng Long , Yao Xi Jun , Sun Xu
Published: October 2011

To analogy and calculate the force distributed characteristic of external force of stem to transmition toward the root system by the SM Solver, and take the roots of Caragana microphylla Lam. and Artemisia sphaerocephala krasch. as the object of study in this paper. The results showed that the force of two plants mainly bears by the main roots, and the force of main roots decreases with the increase of soil depth. Force of main roots of Caragana microphylla Lam. and Artemisia sphaerocephala Krasch. at most reach 89℅ and 98℅ of external force of stem, Force of First-level roots of Caragana microphylla Lam. and Artemisia sphaerocephala Krasch. at most reach 14℅ and 10℅ of external force of stem, and that of second roots of Caragana microphylla Lam. and Artemisia sphaerocephala Krasch. is only 2℅ and 0.3℅. Force decreases with the increase of root length and depth, and the force increases with the increase of included angles between roots and vertical line.
Flow Field Analysis and Experiment Study on Air Losing of Hydraulic Retarder
Authors: Li Hui Yuan , Xu Ming , Wu Chao
Published: October 2011

Based on application characteristic of hydraulic retarder in combined braking, the generant mechanism of air losing is analyzed, by adding baffle-plate setting, air losing is reduced. Using CFD technology, the ameliorative hydraulic retarder is studied contrastively, and the results are in good agreement with the experiment.
Solution for Modeling 3D Moving Heat Sources in a Semi-Infinite Medium and Applications to Submerged Arc Welding
Authors: Ghosh Aniruddha
Published: October 2011

The determination of the temperature distribution of submerged arc-welded plates is essential when designing submerged arc-welded joints. The key role for the change of weld-bead geometry dimension, thermal stress, residual stress, tensile stress, hardness, etc., is heat input. Heat input is the function of temperature distribution of submerged arc welded plates. An attempt is made in this paper to find the analytical solution for a moving heat-source of egg-shape in a semi-infinite body. The considered modes of heat transfer for this study are conduction and convection. The solution has been obtained by integrating the instantaneous point heat source throughout the heat source volume. Very good agreement between the predicted and measured transient temperatures at various points on submerged arc-welded plates has been obtained. The predicted yield parameters are also in good agreement with the measured values.
Effect of Ageing on Microstructures, Electrical Properties and PALS of Aircraft Al Alloy 2024
Authors: Refeay Abdullah A. , Kamel N.A. , Abdel-Rahman M.A. , Lotfy Yahia A. , Badawi Emad A.
Published: October 2011

A comprehensive and systematic study using PALS technique, Vickers hardness test and electrical LCR meter were undertaken to follow property development during the recently promoted interrupted ageing treatment for 2024 aluminum alloy. In this work, solution heat treatments at different temperatures were performed in aircraft materials 2024 aluminum alloy. This work describes the development of the dependence of mechanical, electrical properties of 2024 Al-alloys on heat treatment to characterize microstructural changes during heat treatment. PALS, mechanical and electrical testing will be used to measure the features of the material as a function of time for each ageing temperatures.
Development and Characterization of Alumina-Silica Sand Nanoparticle Composites
Authors: Ahmad Tahir , Mamat Othman , Wahjoedi Bambang A.
Published: October 2011

Ceramic-ceramic composites are used around the world in demanding thermal, structural and electrical insulating applications. The present study aims to develop Alumina-Silica sand nanoparticles composites through powder processing route. Effect of amount of silica sand nanoparticles on the composite properties at different sintering temperatures was studied. Composites with 5, 10, 15 and 20 wt.% of silica sand nanoparticles were developed and sintered at 1300, 1400 and 1500 oC. It was observed that the incorporation of silica sand nanoparticles enhanced the hardness and sintered density of the composites. FESEM and EDS analysis evidenced the proposed liquid phase sintering, mullite and spinel formation mechanisms are primary cause of the composites mechanical properties improvement.
Bone Repair Efficiency by Various Round Granular Bone Substitutes
Authors: Jhun Jick Soo , Yun Hui-Suk , Park Eui Kyun , Shin Hong In
Published: October 2011

To improve the efficiency of osteogenic repair, we compared 3 types of round granular bone substitutes composed of hydroxyapatite (HA) in a single opened large pore covered by one or more thin shell structure, biphasic HA and tricalcium phosphate (TCP) in a compact granules with small uniform interconnected internal pores, and bioglass(BG) in a compact granules with hierarchical interconnected pores its bone repair efficiency by evaluation of cellular toxicity, cellular attachment and proliferation rate, and osteogenic supportive effect. They were nontoxic and revealed no noxious effect on cellular proliferation and osteoblastic differentiation. The cultured cells were most effectively proliferated on HA granular bone substitute surface. However, the bony repair of calvarial defects was most effective by BCP granular bone substitutes. The implanted BCP and HA granular bone substitutes showed excellent osteoconductive bone growth and favorable bone regeneration within 3 weeks compared to BG granular bone substitutes. All type granular bone substitutes were well incorporated into newly formed bone without foreign body reaction. Except for HA granular bone substitute, some implanted BG and BCP granular bone substitutes were partially resobed by TRAP positive multinucletated cells. These findings suggest that round granular biphasic calcium phosphate bone substitute structured with fully interconnected uniform sized internal pore might be a more promising bone substitute for small-sized none load-bearing bone defects.
Nanostructured Bone Grafting Substitutes – A Pathway to Osteoinductivity
Authors: Gerber Thomas , Lenz S. , Holzhüter G. , Götz W. , Helms K. , Harms C. , Mittlmeier Th.
Published: October 2011

The comparative investigation of a highly nanoporous bone grafting material (NanoBone S, NBS) and a sintered hydroxyapatite ceramic (Cerabone, CB) aimed to show the influence of the structure of the material on osteoinductivity.NBS consists of synthetic nanocrystalline hydroxyapatite embedded in a porous silica gel matrix. Its specific surface amounts 206 m2/g in contrast to CB with a specific surface of 0.4 m2/g.The biomaterials were implanted in the neck region of 18 sheep and left there for the periods of 6, 12 and 26 weeks. In each case granulate was implanted superficially into the trapezius muscle and into the subcutaneous adipose tissue respectively. The samples were analysed by micro-CT, histochemistry, immunohistochemistry and histomorphometry. In the case of NBS ossicles had developed. An intensive remodelling process was verifiable. The bone formation in CB was marginal.As a basic phenomenon in NBS, the substitution of the original SiO2 gel matrix by organic molecules forming an organic matrix around the embedded hydroxyapatite seams to be the key event causing these results.
Gallium-Doped β-Tricalcium Phosphate Ceramics: Characterization and Properties
Authors: Mellier C. , Schnitzler V. , Deniard P. , Bouler Jean Michel , Bujoli B. , Janvier P.
Published: October 2011

A novel gallium-doped -tricalcium phosphate (-TCP) ceramics with rhombohedral structure (R3c space group) can be obtained by the addition of a Ga precursor in the typical reaction protocols used for the preparation of -TCP. It was found, from the refinement of their XRD patterns, that the incorporation of Ga in the -TCP network occurs by substitution of one of the five calcium sites, while occupation of another Ca site decreases in inverse proportion to the gallium content in the structure. A decrease of the unit cell volume is observed with increasing gallium content, together with improved mechanical properties. Indeed, the compressive strength of these new bioceramics is enhanced in direct proportion of the Ga content, up to a 2.6-fold increase as compared to pure -TCP.
Effect of Al2O3, ZrO2, and TiO2 Addition on the Mechanical Properties and the Microstructure of Natural Hydroxyapatite Obtained from Calf Femoral Bone
Authors: Ozden Ilker , Ipekoglu M. , Mahmutyazicioglu N. , Altıntaş S.
Published: October 2011

Pure hydroxyapatite (HA) was obtained by the calcination of calf femoral bone and was ground manually and by subsequent mechanical grinding to decrease the particle size. Micron-sized Al2O3, ZrO2, and TiO2 ceramics were added at different concentrations (5, 10 and 15 wt. %) to the obtained micron-sized HA powder. After adequate mixing cylindrical test specimen were prepared and sintered at 900, 1000 and 1100 °C. The specimen were tested for their compressive strengths and SEM observations and XRD analyses were conducted to determine the effect of different additives and sintering temperatures on the mechanical strengths, morphology and formed phases of the samples. TiO2 addition to the HA at 15 wt. % powder resulted in highest compressive strength with good sintering behavior.
Raman and Infrared Studies of Substituted β-TCP
Authors: Quillard Sophie , Mellier Charlotte , Gildenhaar Renate , Hervelin Julien , Deniard Philippe , Berger Georg , Bouler Jean Michel
Published: October 2011

Several substituted â-tricalcium phosphates have been prepared with different cations (monovalent, divalent and trivalent) and at various levels of substitution. Structural investigations have proved that fewer than ~10% wt substitution, the substituted compounds are isostructural to â- TCP, leading to solid solutions. These samples have been characterized by infrared and Raman spectroscopies. The vibrational spectra show mainly the bands related to the vibrations of PO43- tetrahedrons present in the structure. As Raman scattering and infrared absorption are local probes, the bands are sensitive to the local environment of the distinct tetrahedrons, related to the site of substitution and to the nature of the cations.
In Vivo Behaviour of the Synthetic Porous Hydroxyapatite Prepared by Low Temperature Microwave Processing and Comparison with Deproteinized Bovine Bone
Authors: Strnadová M. , Strnad Z. , Šponer Pavel , Jirošova Jana , Strnad J.
Published: October 2011

The aim of this study was to evaluate the osteoconductive properties of synthetic porous hydroxyapatite prepared by low-temperature microwave processing OssaBase® HA (SPHA) in comparison with biological apatite, non-sintered deproteinized bovine bone Bio-Oss® (DBB). The materials were implanted into the bone sockets of the tibia of Beagle dogs for 3 and 6 months. The bone response to granules of the materials of similar sizes was compared. Histological analysis of the specimens with histomorphometry was performed at different times after in vivo implantation. Based on the histological analysis, the level of bone formation in the spaces between the implanted granules and through the interconnected pores of both implanted materials within a cortical region was significantly higher (bone area ingrowth 72–85%) than within a cancellous bone site (bone area ingrowth 16–28%) at three and six months after implantation. According to our study, the bioactive and osteoconductive properties (bone implant contact and bone area ingrown) of the synthetic porous hydroxyapatite are very high and comparable with the biological apatite, non-sintered deproteinized bovine bone. The favourable influence of the high specific surface area and carbonate content of the synthetic, porous hydroxyapatite on bone formation was confirmed.
Production of Natural Bioceramic from Land Snails
Authors: Kel D. , Gokce Hasan , Bilgiç D. , Ağaoğulları D. , Duman I. , Öveçoğlu M.L. , Kayali Eyup Sabri , Kiyici Ismail Akin , Agathopoulos Simeon , Oktar F.N.
Published: October 2011

There are thousands of land snail species, ranging in size from 1 mm to the Giant African Snail growing up to a foot long. Two species, known as escargot, helix aspersa and helix pomatia, are commercially important. Helix pomatia is abundant in Turkey. Those snails are exported usually without shells. Shells are damped to trash sites or used as substitute food for animals. The shell is rich in calcium carbonate and some other minor minerals. Thus, snails’ shells can be used as a source for bioceramic production. So far, in the literature there are lot of papers about converting calcite and aragonite structures to hydroxyapatite (HA), like corals, sea shells, sea urchin and other sea creatures. However, there is very limited information about converting land snail shells to HA and other bioceramic phases. The aim of this work was to produce various phases of bioceramic materials from land snails’ shells which are left as a residue waste after their export procedures. Empty local land snails’ shells (helix pomatia) were collected in Istanbul. They were washed, dried, crushed and ball milled until a powder of 100 µm particles size was obtained. Raw powders were stirred at 80°C for 15 min on a hotplate. A second part of the raw powder was stirred with an ultrasonic stirrer at 80°C for 15 min in an ultrasonic equipment. Equivalent amount of H3PO4 was added drop by drop into the solution. The reaction lasted for 8h. Then, to evaporate the liquid part, the mixtures were put into an incubator at 100°C for 24 h and the resultant dried sediments were collected. The produced powders were analyzed with X-ray diffraction, IR and scanning electron microscope (SEM). The experimental results confirmed the formation of various Ca-phosphates, specifically monetite, fluorapatite and some other minor calcium phosphate phases. Bioceramic production from land snail is a reliable and economic way comparing to other tedious methods of producing synthetic HA and other various bioceramics phases.
The Influence of Three Additives on the Setting Reaction Kinetics and Mechanical Strength Evolution of [Alpha]-Tricalcium Phosphate Cements
Authors: Cardoso H.A.I. , Motisuke M. , Zavaglia Cecília A.C.
Published: October 2011

Among the calcium phosphate cements, the system based on alpha-tricalcium phosphate (α-TCP) combines several interesting properties. However, these cements have their use limited to low load applications. The main objective of this study is to evaluate the influence of three different additives on the setting reaction kinetics and mechanical strength evolution of calcium phosphate cements as a function of time. The cement was obtained by mixing α-TCP powder with four different aqueous solutions containing or not containing disodium hydrogen phosphate (Na2HPO4), citric acid (C6H8O7) and/or tannic acid (C76H52O46). It was observed that two cement samples, one of them containing Na2HPO4 and C6H8O7 and another containingNa2HPO4 and C76H52O46 in the liquid phase, presented faster setting reaction and higher mechanical properties. These cements are more suitable for application as bone cement.
Effect of Electrolyte Chemistry on the Structural, Morphological and Corrosion Characteristics of Titania Films Developed on Ti-6Al-4V Implant Material by Plasma Electrolytic Oxidation
Authors: Venkateswarlu K. , Suresh S. , Nagumothu Rameshbabu , Bose Arumugam Chandra , Subramanian S.
Published: October 2011

The present work is aimed at the optimisation of an electrolyte system for the development of an oxide layer on Ti-6Al-4V implant material by plasma electrolytic oxidation (PEO) process, to improve its corrosion resistance under 4.5 pH osteoclast bioresorption and 7.4 pH simulated body fluid physiological conditions. All the PEO experiments were conducted for 12 min in constant current mode by a DC power supply unit with 7 different electrolyte systems consisting of methodically varied concentrations of tri-sodium ortho phosphate (Na3PO4.12H2O), sodium meta silicate (Na2SiO3.9H2O) and potassium hydroxide (KOH). The phase composition of the fabricated oxide coatings was analyzed by X-ray diffraction (XRD) technique. The morphology and thickness of the coatings were determined by scanning electron microscopy (SEM) and the corrosion characteristics were assessed by potentiodynamic polarization and electrochemical impedance spectroscopic techniques. The XRD results demonstrated that the oxide coatings mainly consisted of anatase and rutile phases with different proportions. While the average surface pore size was in the range of 3 to 6 µm, the thickness of the coating varied from 5 to 20 µm. A significant improvement in the corrosion resistance and an added capacitive nature was observed for the PEO treated Ti-6Al-4V implant material compared to that of the untreated. The variation in the proportions of anatase and rutile phases, the surface pore size distribution, the thickness of the coating and the corrosion characteristics of the developed coatings were correlated with the composition and concentration of the electrolyte system. Of the seven different electrolyte systems employed in the present study, the one consisting of 10 g Na3PO4.12H2O, 2 g Na2SiO3.9H2O and 2 g of KOH was established to be an optimized electrolyte system for developing oxide coatings on Ti-6Al-4V to minimise corrosion and thereby reduce the metal ion release under physiological conditions.
Influence of Strontium on In Vitro Bioactivity of Heat-Treated Porous Ca-P Ceramics on Titanium for Biomedical Applications
Authors: Kung Kuan Chen , Lee Tzer Min , Lui Truan Sheng
Published: October 2011

The bioactivity of materials was evaluated based on the ability to induce a bond-like apatite layer on the surface in simulated body fluid (SBF). The aim of this study was to investigate the coatings containing strontium on bioactivity after heat treatment. After the materials were soaked in SBF for 1 day, precipitates did not form on the surface of heat-treated MAO coating without strontium. The precipitates were observed on surface of heat-treated MAO coatings containing strontium. After 7 days, the surface of heat-treated MAO coatings containing strontium was completely covered with precipitates. The precipitates were found to be composed of fiber structures using scanning electron microscope (SEM). The phase was identified as the apatite phase using thin film X-ray diffraction (TF-XRD). The results show that heat-treated MAO coatings containing strontium can induce the formation of an apatite layer on their surface. All finding in this study indicated that heat-treated MAO coatings containing strontium have good bioactivity for clinical applications.
Parascholzite Coatings on Niobium Substrates
Authors: Moura Felipe Nobre , Louro Luis Henrique Leme , Gobbo Luciano Andrade , Prado da Silva Marcelo Henrique
Published: October 2011

This study proposes a hydrothermal process to produce monetite and zinc-doped calcium phosphate coatings with different (Ca+Zn)/P molar ratios, in an attempt to incorporate zinc benefits on bone formation to hydroxyapatite precursors. The method consists of coating niobium and titanium substrates in an aqueous solution rich in (PO4)3- and calcium (Ca)2+ ions under specific conditions (pH ≡ 3.7, 80°C). Scanning electron microscopy (SEM) and X-ray diffraction (XRD) analyses were performed to characterize the coatings. From XRD analysis, we concluded that substitution of Ca by Zn was feasible up to 15% mol Zn, and the new phase obtained was parascholzite (JCPDS-01-086-2372).
A Novel HAp Coating Method on Titanium
Authors: Valanezhad Alireza , Tsuru Kanji , Maruta Michito , Matsuya Shigeki , Kunio Ishikawa
Published: October 2011

A coating layer with hierarchical structure: Titanium-Zinc-Phosphate (Ti-Zn-PO4) / Hydroxyapatite (HAp) coating layer was prepared on titanium (Ti). The Ti plates were treated using two step hydrothermal treatments: first step in acidic zinc phosphate solution to form Ti-Zn-PO4 coating and second step in calcium chloride solution to form HAp. The Ti-Zn-PO4 layer strongly attached to the Ti surface. The adhesive strength of the coating layer was measured higher than 48 MPa. The surface observation and element analysis indicated that the Ti plates were covered with Ti-Zn-PO4 coating layer after hydrothermal treatment at 250°C. When Ti-Zn-PO4 coating was treated hydrothermally with calcium chloride solution, crystalline HAp layer was formed on its surface.
Investigations on Vitro Behaviour of Ceramic Coatings Deposited by High Velocity Suspension Flame Spraying
Authors: Bernstein Anke , Suedkamp Norbert , Mayr Hermann Otto , Gadow R. , Killinger A. , Stiegler N.
Published: October 2011

Bioceramics used as coatings show different biocompatibility and bioactive behavior in relation to their chemical and morphological behavior. Bioactive ceramics such as β-tricalcium phosphate (β-TCP) promote and enhance biological fixation. Stable coatings require an optimum between resorption rate, flexural strength and adhesive strength of the coating. Therefore new bioceramic coating materials that ensure the balance between loss of substances and osteointegration need to be designed and investigated. By modifying the high velocity suspension flame spraying (HVSFS) process parameters, five coatings with different materials were obtained. The in vitro cytotoxicity was determined by the microculture tetrazolium (WST) assay after 24, 48 and 72 h. Cells were grown on the materials for 3, 7, 14, and 21 days and counted. Cell morphology, cell attachment, and cell spreading were investigated using fluorescence microscopy and raster scanning electron microscopy. All substrates supported sufficient cellular growth for 19 days and showed no cytotoxicity. On each material an identical cell colonisation of well communicating, polygonal, vital cells was verified.
Occlusal Surface Reconstruction with Chairside Ceramic Onlay Using CEREC Biogeneric Design Mode: Case Report
Authors: Akgungor G. , Olcer Y. , Şen D. , Tunçelli B.
Published: October 2011

The occlusal design of dental restorations should stay in harmonic relation to the remaining dentition. In CAD/CAM dentistry, the occlusion is generated by the CAD software based on standard morphologies from the dental database. An automated adaptation process of this standard morphology to an individual clinical situation is difficult and leading to manual adaptation of the proposal with design tools. The new biogeneric software of the chairside CAD/CAD system (CEREC) automatically collects optic measurement of the preparation side including mesial and distal neighbor teeth and antagonist teeth to design a restoration with a patient specific occlusal morphology. This clinical report demonstrated a case, which was treated with ceramic onlay designed and milled with CEREC system used in biogeneric design mode. Digital impression of the preparation was taken with the intraoral camera. Buccal scan,technique was used for taking the occlusal record. Preparation and antagonist images were automatically correlated by software and a virtual articulator was created. After trimming the virtual model, preparation margins were outlined with the automatic margin finder option of the software and then the insertion axis of the restoration was determined. The biogeneric restoration proposal was then automatically seated to the virtual model and desired changes were performed with the design tools of the software. The restoration was milled from feldspathic ceramic block.
Clinical Success of IPS Empress II Inlays/Onlays
Authors: Yanıkoğlu Funda , Özyöney Gürol , Özyöney Nuran , Tağtekin Dilek , Öveçoğlu Hesna , Günday Mahir
Published: October 2011

For the dental restorations, ceramic materials have increasing popularities because of their biocompatibility and superior esthetics. IPS Empress which is leucite-reinforced glass ceramic is one of the most popular ceramics. IPS Empress II was developed in following years which is stronger than IPS Empress. In the dental applications some problems occur about ceramic restorations. Hence,this study was performed to examine the six-year clinical performance of IPS Empress II ceramic onlay and inlay restorations.
Calcium Fluoride/Hydroxyfluorapatite Nanocrystals as Novel Biphasic Solid Solution for Tooth Tissue Engineering and Regenerative Dentistry
Authors: Azami Mahmoud , Jalilifiroozinezhad Sasan , Mozafari Masoud
Published: October 2011

In this research, a novel biphasic solid solution consisted of Calcium fluoride (CF) and fluorinated-hydroxyapatite (FHAp) was successfully synthesized through a modified precipitation method using buffer solution. The obtained results confirmed the formation of biphasic nanocrystalline powder composed of about 46% CF and 54% (w/w%) FHAp. This product can be considered as an osteoconductive dental filler or implant with the ability of dental carries prevention due to release of fluorine ions. Herein, the usage of buffer solution for this purpose not only can produces biphasic powder but also provides the possibility of establishment of a continuous synthesis method without manual interfere for adjusting pH of the reactor.
Resin Bond Strength to Alumina Coated Ce-TZP/Al2O3 Dental Ceramic
Authors: Kosmač Tomaz , Kocjan Andraž , Golobicˇ M. , Jevnikar P.
Published: October 2011

The aim of this study was to functionalize the surface of Ce-TZP/Al2O3 dental ceramic with a nano-structured alumina coating to improve resin bonding. A total of 40 densely sintered disc-shaped specimens (15.5 + 0.03 mm in diameter and 2.6 + 0.03 mm thick) were produced from commercially available NANOZIR blocks and randomly divided into 2 groups of 20. Half of the discs in each group received an alumina coating that was fabricated by exploiting the hydrolysis of aluminum nitride (AlN) powder. The coating was characterized using scanning electron microscopy (SEM). The shear bond strength of the self-adhesive luting cement G-cem was then studied for the coated and uncoated surfaces before and after thermocycling (TC). The SEM analysis revealed that the application of an alumina coating to Ce-TZP/Al2O3 ceramics created a highly retentive surface for resin penetration. The resin bond strength to the coated groups was significantly higher than to the uncoated groups, both before and after TC (p ≤ 0,05).
Preparation of Calcium-Phosphate Microspheres by Salt-Assisted Ultrasonic Spray-Pyrolysis Technique and their Drug Release Behavior Using Anti-Angiogenic Agent, TNP-470
Authors: Matsueda Masaru , Emoto Makoto , Aizawa Mamoru
Published: October 2011

Synthetic clcium phosphate based materials, such as hydroxyapatite (Ca10(PO4)6(OH)2; HAp) and tricalcium phosphate (Ca3(PO4)2; TCP), are compounds with high potential for clinical applications to orthopedic and dental region. In previous study, we have reported that the hollow and porous apatite microsphere could be prepared by salt-assisted ultrasonic spray-pyrolysis (SAUSP) technique using sodium chloride (NaCl). In this case, these microspheres have some problems of (i) decrease of dissolubility of microspheres and (ii) cytotoxicity arising from chloride ions elution. To overcome these disadvantages, we prepared novel microspheres by SAUSP technique using potassium nitrate (KNO3) instead of NaCl. The resulting microsphere was washed with pure water to remove the KNO3 phase. The particle shapes of the powders were observed by scanning electron microscopy (SEM); the diameters of the microspheres were of 0.5 - 3.0 m, and the fine pores with the sizes of ~50 nm were present on the surface of the microspheres. The TNP-470 agent as a model of drug were loaded on these microspheres with nano-pores in the surface. In the KNO3 concentration of 1.00 mol·dm-3, 70 % of the total TNP-470 from the microspheres was rapidly released within 1 h. The remaining 30 % was slowly released up to 24 h following immersion, and total amount of TNP-470 released from the microspheres was 42 g·mg-1.
Preparation of Injectable Hydroxyapatite/Collagen Nanocomposite Artificial Bone
Authors: Kochi Akinori , Kikuchi Masanori , Shirosaki Yuki , Hayakawa Satoshi , Osaka Akiyoshi
Published: October 2011

Injectable hydroxyapatite/collagen nanocomposite (HAp/Col) artificial bone was prepared utilizing gelation of sodium alginate (Na-Alg). Mass ratio of the HAp/Col powder, with or without Ca adsorption treatment and Na-Alg (80-120, 300-400, 500-600 cP in viscosity at 10 g/dm3) was fixed at 90/10. Injectable HAp/Col was prepared by mixing the HAp/Col powder with Na-Alg solution at several powder (HAp/Col)/liquid (Na-Alg solution) ratios (P/L ratio, g/cm3). The result of consistency measurement suggested that the operability of injectable HAp/Col paste could be controlled by both the P/L ratio and the viscosity of Na-Alg solution. According to the consistency measurement and practical feelings during mixing, P/L=1/1.67 (80-120 cP) and 1/1.89 (300-400, 500-600 cP) were considered to be the highest P/L ratio allowed to mix the HAp/Col paste with a spatula. At the P/L=1/2.33 (80-120 cP), the paste prepared with the non-treated HAp/Col powder, placed in an incubator (37 °C,relative humidity 100%) for 24h, demonstrated gel-like property, while the paste prepared with Ca-treated HAp/Col powder did putty-like property. The difference in their property might be caused by the initial bonding behavior between Alg and Ca2+ after mixing. The setting time measurement with Gillmore needle was impossible because they were toosoft for this method. Even though, their operability and coalescence/settingproperty could be used as the injectable bone filler.
FTIR Analysis and Cytotoxicity Test of Titanium Dioxide Nanoparticles
Authors: Rodrigues L.R. , Dias C.G.B.T. , Ceragioli H.J. , Rodas A.C.D. , Monteiro F.J.M. , Zavaglia Cecília A.C.
Published: October 2011

Titanium dioxide is a material widely used in electronics industry and little explored in the biomedical area, which is the objective of this work. Nowadays one can find surgical instruments coated with thin films that have bactericidal properties when they are activated in the presence of ultraviolet light. For crystalline phase control TiO2 was calcinated at 500°C. The crystallite mean size for sample calcinated at 500°C was 27nm. With the results of cytotoxicity it is possible to say that biomedical applications are possible. Electron microscopy images showed nanoparticles obtained by sol-gel process and the compounds were identified by FTIR analysis. Raman spectroscopy confirmed the existence of anatase titania phase and X-ray diffraction showed this material to be composed of a crystalline phase. X-ray fluorescence identified chemical contaminants.
Electrospun Scaffolds Composed of Poly(L-lactic acid) and Hydroxyapatite
Authors: Rodriguez G.N.P , Rodrigues L.R. , Dias C.G.B.T. , d´Ávila M.A. , Zavaglia C.A.C.
Published: October 2011

Tissue engineering is an important emerging area for creating biological alternatives for harvested tissues, implants, and prostheses. Biocompatible and biodegradable polymeric materials are considered an important class of materials that can be used as scaffolds in tissue engineering applications. In this work, the system studied was nanocomposites of hydroxyapatite (HA) dispersed in a matrix of PLLA. Scaffolds have to present similar structure and also function as an artificial extracellular matrix for cell attachment and growth. Hydroxyapatite is a bioactive ceramic and has been used in applications of repairing bone tissue due to its biocompatibility and osteoconductivity. Poly(L- lactic acid) is a biodegradable and biocompatible polymer and has been used in different applications in the biomedical field. In this work, polymer solutions were prepared with different percentages of hydroxyapatite and porous membranes consisting of non-woven nanostructured fibers were obtained by electrospinning. The process parameters were: voltage of 13kV, flow rate of 0.5 ml/h and distance from the tip of the needle to the collector of 12 cm. By using these process parameter, fibrous membranes were obtained with different concentrations of HA (1.96, 4.76, 9 [wt %]). The morphology of the samples was observed by SEM and the characteristic physic-chemical were analyzed by XRF, XRD, DSC and FTIR.
Effect of Flow Rate of Medium in Radial-Flow Bioreactor on the Differentiation of Osteoblasts in Tissue-Engineered Bone Reconstructed Using an Apatite-Fiber Scaffold and Rat Bone Marrow Cells
Authors: Miura Maiko , Fukasawa Jun , Yasutomi Yumiko , Maehashi Haruka , Matsuura Tomokazu , Aizawa Mamoru
Published: October 2011

Tissue engineering has been studied as a novel therapeutic technology which replaces organ transplantation. Tissue engineering consists of three factors “scaffolds”, “cells” and “growth factors”, and regenerates defecting tissue using them. We have successfully developed porous apatite-fiber scaffolds (AFSs) which have three-dimensional (3D) inter-connected pores using single-crystal apatite fibers and carbon beads; subsequently, we have clarified that the AFSs have an excellent bioactivity on the basis of both in vitro and in vivo evaluations. In addition, we have reconstructed the 3D tissue-engineered bone through 3D-cell culture of mesenchymal stem cells derived from rat bone marrow (RBMC) using the AFS settled into the radial-flow bioreactor (RFB). Aim in the present work is to examine the effect of flow rate of medium in the RFB on the differentiation of osteoblasts in tissue-engineered bone reconstructed using an AFS and RBMC. The flow rates were set to 1.3 and 6.3 cm3∙min-1; tissue-engineered bones reconstructed by the two flow rates are defined as “bone#1” and “bone#2”, respectively. The ALP activity and OC amount normalized for DNA content of bone#2 were higher than those of bone#1. These results indicate that the faster flow rate may promote the differentiation into osteoblast. Thus, the physical irritation to cells, such as flow rates, may be effective for reconstruction of tissue-engineered bone.
Development and Mechanical Characterization of a Collagen/Hydroxyapatite Bilayered Scaffold for Ostechondral Defect Replacement
Authors: Gervaso Francesca , Scalera Francesca , Padmanabhan Sanosh Kunjalukkal , Licciulli Antonio , Deponti Daniela , Di Giancamillo Alessia , Domeneghini Cinzia , Peretti Giuseppe M. , Sannino Alessandro
Published: October 2011

In this work a novel three-dimensional ostechondral substitute is proposed that is made of an inorganic/organic hybrid material, namely collagen/hydroxyapatite. The two components of the substitute have been characterized separately. The inorganic part, a hydroxyapatite scaffold, was fabricated by a polymer sponge templating method using a reactive sub-micron powder synthesized in our laboratory by hydroxide precipitation sol-gel route. The organic part, a collagen scaffold, was fabricated by a freeze-dying technique varying design parameters. Both the parts were analysed by scanning electron microscopy and their mechanical properties assessed by compression tests. The hydroxyapatite scaffold showed a high and highly interconnected porosity and a mechanical strength equal to 0.55 MPa, higher than those reported in literature. The collagen scaffolds were seeded by chondrocytes, processed for histology analysis and tested in compression. The biological tests proved the ability of the scaffolds to be positively populated by chondrocytes and the mechanical analysis showed that the mechanical strength of the scaffolds significantly increased after 3 weeks of culture.
Adhesion Behaviors of Serum Proteins on Oxide Layer of Commercially Pure Titanium
Authors: Um Seung Hoon , Rhee Sang Hoon
Published: October 2011

Effect of oxide layer formed on commercially pure titanium by heat-treatment on adhesion of serum proteins and differentiation activity of osteoblasts. Commercially pure titanium disks were polished and then heat-treated at 700°C for 30 minutes. Titanium oxide layer (rutile phase) was observed to form on the titanium disk surface after heat-treatment. The contact angle of a water droplet on the heat-treated titanium disk was about 14o while that of non-heat treated one was about 68o. The amount of adsorbed total serum protein on heat-treated titanium disk was four times higher than that on non-heat treated one. ALP activity of primary cultured mouse calvarial osteoblasts on heat-treated titanium disk was also higher than that on non-heat treated one with statistical significance of p < 0.05. It implies that the serum proteins preferentially adsorbed on titanium oxide layer formed on commercially pure titanium and it is likely to enhance the differentiation activity of primary cultured mouse cultured osteoblasts.
The Processing and Fatigue Characterization of TiNi and Ti-6Al-4V Porous Materials
Authors: Aşık Emin Erkan , Nakaş Gül Ipek , Bor Şakir
Published: October 2011

Porous titanium alloys have been extensively studied in biomedical applications due to their elastic moduli similar to that of bone compared to other implant materials. Accordingly, TiNi and Ti-6Al-4V foams have been widely characterized in terms of their various mechanical properties; however, their fatigue properties have not been well studied, even though, it has a vital importance in structural applications such as medical implants. In this study, porous titanium alloys were processed via sintering at 1200 °C for 2 hours employing Mg space holder technique. TiNi and Ti-6Al-4V alloys with a porosity of 49 and 51 vol.%, respectively, were mechanically characterized by monotonic and cyclic compression tests. The compressive strength was determined to be 148 MPa for TiNi foams whereas 172 MPa for Ti-6Al-4V foams with homogenously distributed pores having diameters in the range of 250-600 µm. Endurance limit values were determined relative to the yield strength of each porous alloy in order to enable the comparison of fatigue behavior. The fatigue tests applied with a frequency of 5 Hz and a constant stress ratio (σmin/σmax) of 0.1 have revealed that porous TiNi alloys have an endurance limit of approximately 0.6 σy whereas porous Ti-6Al-4V alloys have an endurance limit of approximately 0.75 σy. The differences and similarities in the microstructure and their effect on mechanical behavior of the two alloys were also studied by employing scanning electron microscope (SEM).
Metallurgical Affects of Three Dimensional Printing Based Rapid Casting Solution
Authors: Singh Rupinder
Published: October 2011

Three dimensional printing (3DP) as rapid casting (RC) solutions has transformed over centuries from black art to science, but the metallurgical impinge on the process responsible for change in mechanical properties (like: surface finish, hardness, dimensional stability etc.) are still disputed. The purpose of the present research paper is to review metallurgical affect of 3DP based RC solution. The result of study suggests that prominent reason found to be responsible for improving the mechanical properties of RC is control of heat transfer rate while solidification (thus reducing dendrite formation).
Performance of HVOF Sprayed NiCr and Stellite-6 Coatings under Pin on Disc Wear Testing
Authors: Singh Hazoor , Sidhu Buta Singh , Prakash Satya
Published: October 2011

Wear behavior of the HVOF deposited NiCr and Stellite-6, coatings on Fe-base alloy steel were evaluated by the pin-on-disc techniques. The coatings were significantly harder and less porous. SEM/EDAX and XRD techniques were used to analyse the worn out surface and wear debris. The Fe2O3 was identified as the major phase in the wear debris. The wear mechanism is mild adhesive wear in nature. The coatings protected the substrate steels against the adhesive wear significantly.
Assessing the impact of virtual educational interface agents on adults with little or no computer skills
Authors: Potgieter Louwrens , De Wet Lizette
Published: October 2011

Which characteristics should an interface agent have to ensure it being helpful? An interface agent must make a system effective, efficient and easy to use. The system being developed will help to accomplish this. We consider the most effective ways to present interface agents.
Cognitive Enhancers in Moderate to Severe Alzheimer's Disease
Authors: Hardeland Rüdiger
Published: October 2011

The treatment of moderate to severe Alzheimer's disease is reviewed with regard to mechanisms of action, pharmacokinetics, metabolism, safety/tolerability, and efficacy in reducing cognitive, behavioral/psychiatric, functional and global symptoms. The cholinesterase inhibitors donepezil, rivastigmine and galantamine and the N-methyl-d-aspartate receptor channel blocker memantine are moderately beneficial. Small improvements over a few months are followed by slowed mental decline. Concerning cognitive, functional and global functions, these drugs are similarly effective. Cholinesterase inhibitors also reduce apathy, memantine counteracts agitation and aggression. Serious adverse effects are rare with all four drugs. Cholinesterase inhibitors bear a risk for patients with cardiac diseases. Adverse emetic events are typical for oral formulations of these drugs, but less for rivastigmine transdermal patches. Other routes of administration and use of a galantamine prodrug are currently investigated. The superiority of combination therapies over monotherapies requires further support. Promising investigational drugs include the copper/zinc ionophore PBT2 and multifunctional hybrid molecules.
Secondary organic aerosol formation from phenolic compounds in the absence of NOx
Authors: Nakao S. , Clark C. , Tang P. , Sato K. , Cocker III D.
Published: October 2011

Abstract. SOA formation from benzene, toluene, m-xylene, and their corresponding phenolic compounds were investigated using the UCR/CE-CERT Environmental Chamber to evaluate the importance of phenolic compounds as intermediate species in aromatic SOA formation. SOA formation yield measurements coupled to gas-phase yield measurements indicate that approximately 20% of the SOA of benzene, toluene, and m-xylene could be ascribed to the phenolic route under low NOx conditions. The SOA densities tend to be initially as high as approximately 1.8 g cm−3 and eventually reach the range of 1.3–1.4 g cm−3. The final SOA density was found to be independent of elemental ratio (O/C) indicating that applying constant density (e.g., 1.4 g cm−3) to SOA formed from different aromatic compounds tested in this study is a reasonable approximation. Results from a novel on-line PILS-TOFMS (Particle-into-Liquid Sampler coupled with Agilent Time-of-Flight Mass Spectrometer) are reported. Major signals observed by the on-line/off-line Agilent TOFMS indicated that products had the same number of carbon atoms as their parent aromatics, suggesting importance of ring-retaining products or ring-opening products following ring-cleavage.