bluuebunny/crossref_metadata_2025_split huggingface dataset:
Multilayered bead ceramic composite coating for hip prostheses: Experimental studies and preliminary clinical results
Authors: Pizzoferrato A. , Toni A. , Sudanese A. , Ciapetti G. , Tinti A. , Venturini A. 
Published: December 2004

AbstractThe clinical use of a new ceramic composite material made up of multilayered alumina beads and adhered to a ceramic surface with a high‐temperature‐melting bioglass is proposed. The result is a structure characterised by a 27% porosity and an average pore diameter of 400 μm. The actual structure of the parts as well as their interface interaction were determined by Raman laser. The mechanical resistance of the adherence of this coating for the ceramic substratum was good enough to resist the stress to which it was submitted when used for a new model of prosthetic acetabulum. Experiments with rabbits revealed the good biocomatibility of the composite. The osteoproductive activity of the tissue surrounding the implant led to the gradual filling of the porosity with trabecular structures. The preliminary results of the clinical experience which began in November 1985, confirm the good compatibility of the ceramic composite.
Ceramic systems for long‐term delivery of chemicals and biologicals
Authors: Bajpai P. K. , Benghuzzi H. A. 
Published: December 2004

AbstractEvaluation of devices, drugs, and drug delivery systems have been investigated by both in vitro and in vivo procedures. Ceramic drug delivery systems can be used to evaluate chemicals and biologicals by both in vitro and in vivo procedures. The system can also reduce handling of the animals and facilitate long‐term evaluations before conducting clinical trials. To date, ceramic systems have been used to deliver aldosterone, androstanedione, beta‐lactoglobulin, bovine serum albumin, chymotrypsin, danazol, difluoromeythylornithine, dihydrotestosterone, estradiol, gamma globulin, gonadotrophic releasing hormone, gossypol, growth hormone, insulin, methylene blue, pepsin, progesterone, and testosterone. The data obtained suggest that ceramic delivery systems can be used in the near future to treat diseases requiring long‐term chronic drug therapy as well as disorders caused by deficiency of certain hormones.
Mechanical properties and short‐term in vivo evaluation of yttrium‐oxide‐partially‐stabilized zirconia
Authors: Christel P. , Meunier A. , Heller M. , Torre J. P. , Peille C. N. 
Published: December 2004

AbstractYttrium‐oxide‐partially‐stabilized zirconia (YPSZ) belongs to a new class of ceramics exhibiting an improved toughness when compared to alumina. The toughening mechanism is related to a martensitic‐like transformation of tetragonal metastable grains into a monoclinic state occurring at the crack tip. Specific tests showed that YPSZ exhibited a high bending strength (900–1200 MPa), a low Young's modulus (200 GPa), and a high toughness (KIC = 9–10 MN/m3/2). Its average grain size of 0.5 m̈m allows a surface roughness as low as 0.008 m̈m. Sterilization or aging in saline solution at room temperature for 100 days did not affect the toughness of this material. Cylindrical YPSZ samples, manufactured by cold isostatic pressing and sintering, were implanted in the paraspinal muscles in the rat up to 12 weeks. The tissue reaction was evaluated with reference to alumina (ISO requirements) by means of quantitative histomorphometry. No significant differences were found between YPSZ and alumina for both the membrane thickness and cell distributions surrounding the implants.
Elastic and ultimate properties of acrylic bone cement reinforced with ultra‐high‐molecular‐weight polyethylene fibers
Authors: Pourdeyhimi B. , Wagner H. D. 
Published: December 2004

AbstractA study of the fracture behavior of poly‐(methyl methacrylate) (PMMA) bone cement reinforced with short ultra‐high‐molecular‐weight polyethylene (Spectra 900) fibers is presented. Linear elastic and nonlinear elastic fracture mechanics results indicate that a significant reinforcing effect is obtained at fiber contents as low as 1% by weight, but beyond that concentration a plateau value is reached and the fracture toughness becomes insensitive to fiber content. The flexural strength and modulus are apparently not improved by the incorporation of polyethylene fibers in the acrylic cement, probably because of the presence of voids, the poor mixing practice and the weakness of the fiber/ matrix interfacial bond. The present polyethylene/PMMA composite presents several advantages as compared to other composite cements, but overall the mechanical performance of this system resembles that of Kevlar 29/PMMA cement, with a few differences. Scanning electron microscopy reveals characteristic micromechanisms of energy absorption in Spectra 900/PMMA bone cement. A scheme for the strength of random fiber‐reinforced composites, which is a simple extension of the Kelly and Tyson model for the strength of unidirectional composites, is presented and discussed. Young's modulus and the fracture toughness results are discussed in the framework of existing theories. More fundamental modeling treatments are needed in terms of fracture micromechanisms to understand and optimize the various mechanical properties with respect to structural parameters and cement preparation technique.
Tissue biocompatibility of cellulose and its derivatives
Authors: Miyamoto Takeaki , Takahashi Shin‐ichi , Ito Hiraku , Inagaki Hiroshi , Noishiki Yasuhara 
Published: December 2004

AbstractTissue biocompatibility of cellulose and its derivatives was examined in two in vivo tests, one for absorbance by living tissue and one for foreign body reaction. The samples examined were regenerated celluloses and cellulose derivatives: methylcellulose, ethyl cellulose, aminoethyl cellulose, hydroxyethyl cellulose, and cellulosic polyion complexes. The in vivo absorbance by living tissue was found to depend on the degree of crystallinity and the chemical structure of the sample. The foreign body reaction was relatively mild for all the samples examined, showing that cellulose can be converted to biocompatible materials by physical and/or chemical transformation.
Enhancement of the kinetics of the aeration of ethylene oxide sterilized polymers using microwave radiation
Authors: Matthews I. P. , Gibson C. , Samuel A. H. 
Published: December 2004

AbstractEthylene oxide (EO) is used extensively to sterilize medical supplies that are heat sensitive. EO residues in materials post sterilization can present a hazard to patients at the point of use. Protracted aeration (i. e. degassing) times are necessary post sterilization to reduce EO residues to an accepted level. The sorption of EO into polyvinylchloride was found to be an active process given that at sorption equilibrium (i. e. when the net flow of diffusant into the host material has reduced to zero) the number of molecules of EO per unit volume was greater in PVC than in its external environment. The diffusion coefficient (D) was concentration (C) dependent and the relationship which best describes this dependence was D(c) ∝︁ In C. The diffusion of EO was dramatically accelerated (as evidenced by a time saving in degassing of up to 400%) if microwave heating (2.45 GHz) was used instead of conventional heating for the same macroscopic temperature. The values of activation energy for diffusion were obtained from the respective Arrhenius plots of diffusion coefficient versus inverse temperature for each process. In general, even small reductions in activation energy can greatly increase the specific rate of reaction. The relative efficacy of microwaves in eliminating EO residues as evidenced by this data occurs as a result of microwaves reducing the activation energy for diffusion by almost a factor of two. The relative efficiency of microwave desorption compared to conventional aeration offers considerable gains in the cost‐effectiveness of gas sterilization since it will permit a much greater throughput of material, thereby obviating the need for excessively large inventories of equipment.
Oligomers with pendant isocyanate groups as tissue adhesives. I. Synthesis and characterization
Authors: Brauer G. M. , Lee C. H. 
Published: December 2004

AbstractA series of methacrylate oligomers containing pendant isocyanate groups were synthesized by reacting 2‐isocyanatoethyl methacrylate (IEM) and/or m‐isopropenyl‐ α, α‐dimethylbenzyl isocyanate (TMI) in ethoxyethyl acetate with methacrylates ranging from methyl to stearyl methacrylate or allyl‐, cyclohexyl‐, glycidyl‐, i‐bornyl‐, or dicyclopentenyloxyethyl methacrylate. The oligomers which are stable at room temperature were characterized by IR for NCO, ester, and C  C groups and by their refractive indices. They have a small number of residual double bonds and a molecular weight low enough so that the compounds are liquids at room temperature and dissolve readily in esters and chlorinated hydrocarbons. HPLC showed no residual monomer. GPC and intrinsic viscosity of selected oligomers indicated a molecular weight range from 1400 to 2600. Isocyanate groups were determined titrimetrically and ranged from 15.9% to 5.1%. Concurrent studies have demonstrated that these oligomers bond strongly to hard and soft tissues. Thus, subject to their biocompatibility they could find many applications as tissue adhesives.
Properties and biological inteactions of polyurethane anionomers: Effect of sulfonate incorporation
Authors: Grasel Timothy G. , Cooper Stuart L. 
Published: December 2004

AbstractIn order to investigate the factors affecting the interaction of polyurethanes and blood, a series of poly (tetramethylene oxide)‐based polyurethane block copolymers was synthesized with systematically varying levels of ion incorporation in the hard segment block. A bimolecular nucleophilic substitution reaction was used to replace up to 20% of the urethane hydrogens with propyl sulfonate groups. Bulk and surface characterization was performed, and a canine ex vivo arteriovenous shunt was used to monitor initial platelet and fibrinogen deposition on these surfaces. The microphase separation and bulk physical properties were found to vary with ionic content. Surface analysis using both in vacuo (ESCA) and water‐equilibrated (contact angle) methods indicated that these polymers, and especially the highly sulfonated materials, could rearrange to minimize their interfacial tension, depending on the contacting environment. Platelet deposition onto these materials decreased as the level of sulfonation increased, with the highly sulfonated polymer showing substantially less platelet spreading and activation than previously seen in the same experiment with other polymers.
Protein‐resistant surfaces prepared by PEO‐containing block copolymer surfactants
Authors: Lee Jin Ho , Kopecek Jindrich , Andrade Joseph D. 
Published: December 2004

AbstractPolyethylene oxide(PEO)‐containing non‐ionic polymeric surfactants were studied as a possible means to produce PEO‐rich surfaces by a simple coating treatment of a common hydrophobic medical material—polyethylene. Surface tension and adsorption properties of PEO/polypropylene oxide(PPO) and PEO/polybutylene oxide(PBO) block copolymer surfactants on a hydrophobic surface (low density polyethylene, LDPE) were investigated, using the Wilhelmy plate surface tension technique and x‐ray photoelectron spectroscopy(XPS). The protein resistance of the surfactant‐treated surfaces was evaluated by XPS and 125I‐labeled proteins. The data presented indicate that adsorption of the surfactants on LDPE is dependent on the molecular geometry of the surfactants. Adsorption of human albumin was significantly decreased on the surfactant‐treated LDPE surfaces, as compared with the untreated surface. Surfactants suitable for the preparation of PEO‐rich surfaces and possible mechanisms for their protein resistance are discussed.
The role of physical and chemical characteristics in assessing the performance of a new biological vascular graft
Authors: Roberts G. , McCormack H. , Ketharanathan V. , Macleish D. G. , Field P. L. , Milne P. Y. 
Published: December 2004

AbstractInformation obtained from physical and chemical characterization of vascular grafts can prove valuable in obtaining a preliminary assessment of potential in vivo performance. The data presented illustrate the concept and show that the new biological graft made from bovine ureters has adequate performance characteristics for use as a potentially successful vascular graft.
The bovine pericardial xenograft: II. Effect of tethering or pressurization during fixation on the tensile viscoelastic properties of bovine pericardium
Authors: Lee J. Michael , Corrente Ralph , Haberer Sean A. 
Published: December 2004

AbstractOur previous article suggested that control of the extensibility of aldehyde‐fixed pericardium could be achieved by controlling shrinkage during fixation. Therefore, to prevent shrinkage, we have used sandpaper‐lined plexiglass plates to clamp circular samples of bovine pericardium during fixation in glutaraldehyde, tethering them at their original dimensions. As well, we have applied transmural pressures of 50 or 100 mm Hg during fixation using a hydraulic column of glutaraldehyde solution. Strips cut at 0°, 30°, 60° and 90° to the base‐to‐apex cardiac direction have been examined for cyclic stress–strain response, stress relaxation, plastic deformation, and fracture behavior. Under physiological stresses, tethered and pressure‐fixed materials were both nearly isotropic. Tethering during fixation produced a material with extensibility nearly identical to that of fresh tissue. Plastic deformation during cyclic loading was reduced below that seen in simple fixation while stress relaxation was unchanged. Pressure‐fixation produced reduced extensibility similar to that produced in porcine aortic valve leaflets. Plastic deformation and stress relaxation were both markedly reduced. Pressure‐fixation reduced the strain at fracture, but fracture behavior was otherwise unaffected. Tethering and pressure‐fixation offer attractive means to control the mechanical behavior of bovine xenograft materials.
Antithrombogenic surfaces: Characterization and bioactivity of surface immobilized PGE1‐heparin conjugate
Authors: Jacobs Harvey A. , Okano Teruo , Kim Sung Wan 
Published: December 2004

AbstractA covalently bonded conjugate of commercial grade heparin and prostaglandin E1 (PGE1) was synthesized to prevent both fibrin formation and platelet aggregation during thrombus formation. The PGE1‐heparin conjugate was immobilized on an imidazole carbamate derivatized sepharose bead surface through hydrophilic spacer groups (diamino‐terminated polyethylene oxides). One end of the spacer group was coupled to the derivatized surface through a urethane bond between the amine group of the spacer and the derivatized surface. The free amine group of the immobilized spacers was coupled to a carboxylic group of the PGE1‐heparin conjugate through an amide bond. Bioactivity of the immobilized conjugate (heparin activity) was measured in terms of increased clotting times (thrombin time assay) and for the inactivation of Factor Xa. Bioactivity of the immobilized compound (PGE1 activity) was analyzed by platelet adhesion and platelet release reactions using C14‐5‐hydroxytryptamine (5‐HT). The conjugate immobilized via the C2 spacer showed the highest incidence of platelet adhesion, 5‐HT released and the lowest activity for coagulation factors. In contrast, the 1000 and 4000 immobilized systems showed a significant reduction in platelet activation, while having the greatest effect on coagulation factors. The results of these experiments imply that the immobilized conjugate is active in preventing both pathways of thrombus formation, and the efficacy is improved thorugh the use of long‐chain hydrophilic spacer groups.
Bone bonding behavior of MgOCaOSiO2P2O5CaF2 glass (mother glass of A · W‐glass‐ceramics)
Authors: Kitsugi Toshiaki , Yamamuro Takao , Nakamura Takashi , Kokubo Tadashi 
Published: December 2004

AbstractIn this study, it was found that a CaP layer and a Si layer were formed on the interface of the mother glass of apatite–wollastonite containing glass‐ceramics (designated AW) and bone tissue. The dissolution of Si, Ca, and P from glass (MgOCaOSiO2P2O5CaF2) is necessary to form a chemical film (a Si layer and a CaP layer). The three kinds of glasses used were (1) a mirror surface of the mother glass (MgO 4.6, CaO 44.9, SiO2 34.2, P2O5 16.3, CaF 0.5 weight ratio) of AW (designated GAW (mirror)), (2) an abraded surface of GAW (designated GAW (#2000)), (3) a mirror surface SiO2 glass (designated GSi, 100%SiO2). The glass plates (15 mm × 10 mm × 2 mm) were implanted into the metaphysis of tibia of mature male rabbits for 10 and 25 weeks. The failure load, when an implant detached from the bone or when the bone itself broke, was measured by a detaching test and the interface of glass/bone was observed by SEM‐EPMA. Failure loads in GSi, GAW (mirror), and GAW (#2000) 10 weeks after implantation were 0.18 ± 0.24, 3.06 ± 1.29, and 2.94 ± 1.77 kg, respectively. Those in GSi, GAW (mirror), and GAW (#2000) 25 weeks after implantation were 1.30 ± 1.18, 3.88 ± 1.06, and 3.55 ± 1.51, respectively. The failure loads in GSi vs. GAW (mirror) and those in GSi vs. GAW (#2000) differed significantly (P < 0.01). There were no significant differences in the failure load according to the surface roughness of GAW. As shown by SEM‐EPMA observation, a Si layer next to G was adjacent to a CaP layer next to the bone. The chemical film showed no increase in thickness as time passed. A CaP layer did not form on the interface of SiG and bone.
Collagen organization in mandrel‐grown vascular grafts
Authors: Ramshaw John A. M. , Peters David E. , Werkmeister Jerome A. , Ketharanathan V. 
Published: December 2004

AbstractThe organization of collagen in custombuilt biosynthetic vascular prostheses (Omniflow Vascular Graft), which are suitable for periphareral revascularization, has been examined. The grafts were a glutaraldehyde‐tanned ovine‐collagen composite with a polymer mesh reinforcement. Comparisons were made between grafts using different mesh fiber polymers and knit patterns. There was a basic similarity in the arrangement of the tissue structure in all graft types. Scanning electron microscopy and light microscopy showed that the collagen formed a layered structure which fully encased the polymer mesh and held it firmly in position. Rather than polymer mesh, the inner surface of the graft was found to be collagen, and lined with a layer of flattened cells. Collagen formed a continuous layer surrounding the mesh, with no distinct boundary membrane or structurally weak point being apparent. Immunohistology, using a monoclonal antibody specific for type III collagen, and chemical analysis, indicated that there was a high proportion of type III collagen in the grafts, particularly in the region surrounding the mesh fibers.
Creep studies of multiphase acrylic systems
Authors: Øysæd Harry , Ruyter Ivar Eystein 
Published: December 2004

AbstractThe influence of type and quantity of five different crosslinking agents on tensile creep properties of multiphase acrylic systems has been studied. The polymeric materials, commonly applied in bioengineering, were processed by polymerization of a mixture of liquid methacrylate monomers and poly(methyl methacrylate) powder. The specimens were made with various ratios of methyl methacrylate and crosslinking agents in the monomer liquid. Two different processing conditions were used, i.e., heat‐polymerization at 100°C and autopolymerization at 45°C. Creep behavior was determined at 37 ± 0.2°C and 50 ± 0.5°C. The investigation showed higher creep values for autopolymerized than for heat‐polymerized materials. In heat‐polymerized materials the creep curves showed little variation with type and quantity of crosslinking agents at low stress levels. However, at high stress levels the creep values decreased with increasing quantity of crosslinking agents. The autopolymerized materials showed a more inhomogeneous structure, and great variation in creep. Both among the heat‐polymerized and autopolymerized materials, the systems with diethyleneglycol dimethacrylate clearly deviated from the others by showing higher creep values.
Interfacial analysis of fiber‐reinforced bioactive glass dental root implants
Authors: Schepers E. , Ducheyne P. , De Clercq M. 
Published: December 2004

AbstractBioactive glass can form an effective bond with bone. Essential for this connection are the interfacial reactions which lead to the development of a Si‐rich film covered by a CaP‐rich film. The presence of these layers can be demonstrated clearly by EDX analysis of fiber‐reinforced bioactive glass and bulk bioactive glass implants installed for 4 and 16 months in the partial edentulous jaws of beagle dogs. EDX analysis reveals three types of microchemical interface. The first type develops when the implant is bonded to bone. Here, a smooth transition of the CaP profile can be observed between bioactive glass and the bone, thus providing for a compositional gradient between the implant and the surrounding tissues. The second type is seen when the implant surface is surrounded by fibrous tissue. This causes a discontinuity in the CaP profile. The third type is characterized by a gradual decrease in the Ca and P concentrations across the interface, caused by the presence of Ca and P in the fibrous tissue near the implant surface. This suggests that the interface is dynamic in time and transforms to a functionally better optimized interface. EDX analysis does not reveal any metal fiber ion contamination of the outer glass rim of the implant. When stainless‐steel or wrought Co‐Cr alloy is exposed to the surrounding fluids, the interfacial osteogenesis is disturbed, possibly by a synergistic effect of glass ions and metal ions. Exposure of titanium does not interfere with this osteogenesis. The bone bonding can also be influenced by surgical trauma. However, with precise implantation techniques, an enhancement of bone growth by osteoconductivity can be measured.
Comparison of coral resorption and bone apposition with two natural corals of different porosities
Authors: Guillemin G. , Meunier A. , Dallant P. , Christel P. , Pouliquen J‐C. , Sedel L. 
Published: December 2004

AbstractPrevious studies showed that natural coral implanted into bone tissue was gradually resorbed and progressively replaced by newly formed bone. The objectives of this study were to compare the fate of two Madreporian corals, Porites and Acropora, after implantation during 1 and 2 months into sheep and pig long bones. These materials are identical in composition (CaCo3) but differ in volume (49 ± 2%, 12 ± 4%, respectively) and mean size (250 vs. 500 μm) of porosities. The non‐decalcified histological slices were observed under light microscopy. Implant resorption and new bone formation were quantified through an automatic image analysis system. Quantitative results showed that the larger the porosity volume, the greater was the coral resorption as well as the new bone apposition. Large differences were found between the two animal species. Histological findings were identical to those previously reported: implants were resorbed and progressively replaced by newly formed bone. Coral was found to be an osteoconductive biomaterial which acted as a scaffold for a direct osteoblastic apposition and consequently could be an interesting alternative to bone auto‐, allo‐, or xenografts.