bluuebunny/crossref_metadata_2025_split huggingface dataset:
Heparin sorptivity and blood compatibility of carbon surfaces
Authors: Bokros J. C. , Gott V. L. , Lagrange L. D. , Fadali A. M. , Ramos M. D. , Vos K. D. 
Published: December 2004

AbstractThe influences of the conditioning treatments, surface topography, and crystal structure of carbonaceous surfaces on their ability to sorb heparin and their in vivo compatibility with blood were investigated. The results of the sorption studies indicated that the adsorption of heparin on the surfaces of turbostratic and graphitic materials is not crystallographically selective and that the amount adsorbed on relatively smooth surfaces is near the amount expected for monolayer formation. Although the adsorption of heparin on relatively smooth carbon surfaces is not influenced by the presence of benzalkonium chloride, the sorption of heparin in porous carbons can be greatly increased by a pretreatment with benzalkonium chloride. This increase was found to be due to the formation and entrapment of the insoluble heparin‐benzalkonium complex in the accessible porosity. Since the heparin sorptions in Dag‐154 coatings were found to be enhanced by a pretreatment with benzalkonium chloride, it was inferred that these coatings contain accessible porosity and that their initial thromboresistance depends on the formation of the benzalkonium‐heparin complex in pores. In vivo tests showed that polished and outgassed, impermeable isotropic carbons deposited at low temperatures were significantly thromboresistant without the exogenous application of heparin. There was no relationship between the amount of heparin sorbed on these materials and their compatibility with blood. Polishing, for example, which reduced heparin sorption, enhanced the thromboresistance of these carbons, and while chemisorption of oxygen markedly reduced their thromboresistance, it did not influence the amount of heparin that could be sorbed. Although the heparin‐benzalkonium complex sorbed in a porous carbon conferred excellent thromoboresistance in a 2‐hr test, the long‐tern (14‐day) compatibility was not as good as for carbon surfaces that were deposited at low temperatures and then polished and outgassed prior to implanting. In vivo tests of HTI carbon structures and annealed LTI carbons indicate that the blood compatibility of a turbostratic carbon is not significantly dependent on crystallite size, Le. Limited tests of surfaces that had a preponderance of c‐faces oriented parallel to the blood‐carbon interface at the surface suggest that orientations of this sort are better than others.
A metallurgical survey of current orthopedic implants
Authors: Cahoon J. R. , Paxton H. W. 
Published: December 2004

AbstractA number of stainless steel and Vitallium orthopedic implants were purchased from the manufacturers and analyzed to determine their metallurgical soundness. From this sampling of current orthopedic implants over 50% contain metallurgical defects and deficiencies similar to those which have been shown previously to cause failures.
Adsorption of fibrinogen on modified polytetrafluoroethylene surfaces
Authors: Ziegler T. F. , Miller M. L. 
Published: December 2004

AbstractThe adsorption of radiotagged fibrinogen on modified polytetrafluoroethylene surfaces was measured to shed light on the reason of reduced thrombogenicity. These measurements show that when fibrinogen is adsorbed from a solution in which the molecules are in a coiled, undenatured state, adsorption is greater on sulfonated, etched Teflon—a reduced thrombogenic surface, than on unsulfonated, etched Teflon—a thrombogenic surface. On the other hand, when fibrinogen is picked up from a water‐air interface in the form of a monolayer consisting of denatured molecules, the pick‐up is independent of the thrombogenicity of the surface.
The determination of the constitutive relationships for a human aorta
Authors: Krokosky E. M. , Krouskop T. A. 
Published: December 2004

AbstractA testing technique was developed that enabled an aortic vascular specimen to be analyzed in a quasi‐physiological environment. The data that was gathered from human and bovine aortas provided the basis for the formulation of the time dependent constitutive relationships describing the viscoelastic behavior of an aorta subjected to a “normal” pressure pulse.
Flexural properties of equine metacarpus
Authors: Bynum D. , Ledbetter W. B. , Boyd C. L. , Ray D. R. 
Published: December 2004

AbstractThe flexural tests on 37 whole equine metacarpus bones are described and the results are given in terms of fundamental material properties as a function of age. The moduli of elasticity, rupture, and failure increase then decrease with increasing age. The rupture and failure deformations decrease with age. The stiffness and fragility indices increase with age. Averaging the data for all ages, the modulus of rupture was 35 ksi, the deflection at rupture was 0.22 inches, and the modulus of elasticity was 1.7 × 10 psi. The flexural rupture strength is about twice the uniaxial compression strength and about five times greater than the torsional strength for whole bone tests. The moduli of elasticity are about the same for flexure and uniaxial compression, and about five times greater than the torsional modulus of rigidity for whole equine bone.
Microvascular and histogenic responses to implantation of a porous ceramic into bone
Authors: Rhinelander Frederic W. , Rouweyha Marwan , Milner John C. 
Published: December 2004

AbstractA porous ceramic, in the form of small discs, has been implanted into the upper tibiae of adult mongrel dogs in survival experiments. A similar sized disc of a metal (vitallium, titanium, or stainless steel) was also implanted, for comparison, into each tibia. The tissue specimens were studied by microangiography and correlated histology. At the 4‐month, and longer, intervals, the specimens were sectioned with the ceramic disc in situ. Injected capillaries were then observed to have penetrated the ceramic.The metals became surrounded by a shell of new‐bone, lined by a fibrous membrane of varying thickness. The ceramic implants, on the other hand, appeared to have remained inert within the cancellous area of the tibiae, not surrounded by either a membrane or an osseous shell.Implications of these findings were discussed and further experiments, some of which are in progress, were proposed.
Polymers in ophthalmic surgery
Authors: Refojo Miguel F. 
Published: December 2004

AbstractSeveral new surgical techniques in which artificial adhesives are used have been developed. Perforated eyeballs were glued, plastic windows were glued to hazy and opaque corneas, and techniques of retinal surgery wth a minimum use of sutures have been developed.The expanding artificial implant is also described. This is a plastic that imbibes body fluids, swelling to a predetermined volume. Upon swelling, it can fill a cavity or it can produce a deformation in the surrounding tissues. Such a plastic is being investigated as a vitreous substitute. It is also being used to buckle the wall of the eye which carries the blood supply to the retina to reapproximate these layers in order to restore the retina's sensitivity to light. The main feature of this development is that a relatively large implant can be introduced into an organ or tissue through a small incision.
Development of blood compatible polymers using the electret effect
Authors: Murphy Preston V. , La Croix Andre , Merchant Suzanne , Bernhard William 
Published: December 2004

AbstractExcellent in vivo thromboresistance has been obtained for FEP Teflon and for a polyether urethane prepared with electronegative surfaces using the electret effect. In vitro tissue culture studies have shown a marked improvement in tissue compatibility for negatively electrified Teflon. Studies on other materials, including Hypalon rubber, sulfonate cross‐linked Hypalon and Kel F have shown a moderate improvement in blood compatibility. These in vitro and in vivo experiments will be described. Surface physical properties of these electrified materials, including water contact angle and charge, have been measured. Correlations between surface physical measurements and blood compatibility data will be presented.
Experience with negatively charged polyurethane‐backed velours
Authors: Sharp W. V. , Taylor B. C. , Wright J. , Finelli A. F. 
Published: December 2004

AbstractThis report concerns the modification of a velour fabric for use in the vascular system. A specially prepared polyurethane was sprayed on the outer surface of this fabric resulting in a negative surface charge. The advantages of this composite were the incorporation of a thin layer of neointima onto the velour surface. Because of its thinness, viability was maintained resulting in a living nonthrombogenic layer at the vascular interface. To prove the efficacy of this material the authors have implanted it into the right atrium, replaced segments of the inferior vena cava, replaced the 4‐mm carotid artery, and have used it in the construction of an artificial ventricle device. All performed in a superior fashion with long‐term promotion of a viable neointima. It is hoped that the concept of negatively charged velours may be applicable to other phases of biomaterial development.
Applications of plastics in membrane oxygenators
Authors: Galletti Pierre M. 
Published: December 2004

AbstractCurrent trends in blood oxygenator development favor devices which separate the blood phase from the gas phase by a thin film of plastic material. The additional barrier to diffusion presented by the plastic film is a low price to pay for the advantages of the “membrane oxygenator” over its cruder competitors of the “bubbler” or “filmer” type, namely, the absence of direct exposure of blood to gas (with the ensuing damage to the most fragile blood constituents) and the physical constraint of the extracorporeal blood volume to a fixed‐size compartment (obviating the need for complex volume control systems). The first generation of membrane lungs relied on the plastic materials (“Teflon” and silicone rubber) and shapes (flat sheets and tubes) available for industrial uses. A new line of devices will be made possible by the development of new biomaterials and the development of production technologies for the specific purposes of artificial organ research.
Viable prosthetic interface
Authors: Dressler Donald P. , Barlyn Lyle , Skornik William A. 
Published: December 2004

AbstractThe ability to produce a viable bond at the interface of living tissue and inert polymeric materials has been tested in three different contaminated environments. The prosthetic implants, consisting of nylon 66 velour and polyurethane, were tested in the intestinal wall of rabbits, the urinary bladder of dogs, and the skin of rats. The small (1.5 × 2.0 cm) velour implants had a tendency to slough in the intestinal wall while a tubular prosthesis (6 × 3 cm) and a large patch (4.5 × 3.0 cm) were of varying success. Utilization of the prosthesis to replace 25% of the urinary bladder wall was successful for as long as 7 months, at which time postmortem examination of the animals revealed no anastomotic leaks or calculi formation. Replacement of 20 or 40% of the rats burned and infected skin resulted in less than a 10% mortality. Furthermore, histologic studies of all successful prostheses revealed a prompt enmeshing of the velour filaments with fibrin followed at 3‐4 days with an ingrowth of fibroblasts, capillaries, and a few foreign body giant cells. Maturation of the wound resulted in a dense, mature collagen matrix. Removal of the prosthesis at this time occurred only by the disruption of the sub‐prosthetic tissue.
The swelling implant
Authors: Refojo Miguel F. 
Published: December 2004

AbstractExpanding artificial implants are made of crosslinked hydorphilic polymers which imbibe body fluids and swell to a predetermined volume. The material is implanted in a dehydrated state; it then swells to fill a body cavity (i.e., vitreous cavity in the eye), or to give a form to the surrounding tissues (i.e., in plastic surgery). Such implants can be introduced in organs or tissues through a smaller incision than regular plastic and rubber implants, and have the advantage over injectable polymers in that they do not separate into globules and do not migrate from the area of implantation. The swelling equilibrium of slightly crosslinked poly (glyceryl methacrylate) [PGMA] hydrogels in salt solutions, urea, serum, and in the homogenized vitreous of the eye is given. Also, the swelling rate of PGMA in physiologic saline solution and in serum, as well as the swelling pressure‐volume relationship of PGMA gels in water, is reported. The application of PGMA as an expanding implant inside the eye, and against its outer wall in retina surgery, is discussed.
Medical and dental applications of cements
Authors: Smith D. C. 
Published: December 2004

AbstractA number of cements based upon polymeric systems are being utilized in both medical and dental fields. The polymethyl methacrylate rapid polymerizing monomerpolymer materials have undergone extensive development as dental materials and are used widely also for rentention of orthopedic prostheses. The cyanocrylates and the newly developed zinc polycarboxylate cements are being used for a variety of dental applications. These latter materials display adhesion to soft tissue and calcified tissue, respectively, and the investigation of adhesion to these substrates compared with the mechanical retention of the methacrylate materials is of considerable interest.The polycarboxylate cements have unusual properties including minimal tissue irritation and relatively high strength. The ability to vary their formulation and manipulative properties has permitted their trial in a variety of clinical applications including cementation of stainless steel orthodontic brackets to teeth.
Quartz and graphite filament reinforced polymer composites for orthopedic surgical application
Authors: Musikant S. 
Published: December 2004

AbstractMaterials conventionally used for orthopedic surgical implants are primarily metallic alloys such as stainless steel 316L, Cr‐Co‐Mo alloys and recently titanium and Ti‐6A1‐4V alloy. Modulus of elasticity of these (E = 15 to 30 × 106 psi) is an order of magnitude higher than that of bone (approximately 3 × 106 psi). Quartz filament reinforced composites were formulated with E = 6 × 106 psi and flexural stress at rupture (modulus of rupture) of approximately 200,000 psi. Similarly graphite filament reinforced epoxy composites were formulated with E = 16 × 106 psi and flexural stress at rupture (modulus of rupture) of approximately 200,000 psi. Specimens of these materials were implanted in white rats subcutaneously. At sacrifice 90 days after implantation there was no evidence of any inflammatory process, although the implants were completely encapsulated. (Similar in vivo compatibility tests in rabbit muscle tissue are currently in progress.) No significant changes in mechanical properties could be measured in the implants after the 90‐day period of implantation. By adjusting the volume fraction of fibers in a given composite, the modulus of elasticity can be adjusted (with concomittant variations in strength) to meet the biomechanical and dynamic requirements of the appliance. A continuing program to investigate other biocompatible resins and other reinforcement is planned.
In vitro investigation of the adhesive strength of cyanoacrylate bonds to human hard tooth structures
Authors: Khowassah Mohamed A. , Shippy Ronald L. 
Published: December 2004

AbstractThree different cyanoacrylate monomers were studied as adhesives for hard tooth structures. Flat plane non‐retentive surfaces of extracted human teeth and cold‐curing acrylic onlays were used as the adherends. Both tensile and shear adhesive strengths were investigated under wet and dry conditions at room temperature. The commonly used zinc phosphate dental cement was the control material.Under all test conditions the cyanoacrylates were shown to have greater adhesive strength than the dental cement. The MBR‐4197 (β,β,β trifluoroisopropyl 2‐cyanoacrylate) polymer showed the greatest bonding strength to hard tooth structures. The adhesive strengths of all cyanoacrylate polymers decreased considerably after water immersion but the control dental cement material showed no adhesive strength under the same condition.However, the results of the experimental monomers when compared to the control cement, should encourage further investigations of these monomers for use as dental adhesives.
Biodegradable poly(lactic acid) polymers
Authors: Kulkarni R. K. , Moore E. G. , Hegyeli A. F. , Leonard Fred 
Published: December 2004

AbstractThe synthesis of poly(lactic acids) from the cyclic lactides and properties of the polymers prepared have been described. Degradation rates in vitro under homogeous and heterogeneous conditions have been measured. The kinetics of deesterification under homogeneous conditions is second order and an activation energy of 11 Kcal/mol has been calculated. This is comparable to the value found for the hydrolysis of alkyl acetates. A biological in vitro method for determining the degradation of poly(lactic acids) has been described. The method indicates, in accordance with expectations, that poly(dl‐lactic acid) degrades at a faster rate than L(+) lactic acid. Initial results of medical evaluation of the polymers in suture, rod, and film form are presented.
Biological tolerance of poly(N‐substituted methacrylamides)
Authors: Šprincl L. , Vacík J. , Kopeček J. , Lím D. 
Published: December 2004

AbstractExperiments were investigated on animals' biological tolerance of the copolymers of N‐substituted methacrylamides with the monomers which can be considered for uses in the modification of the monomeric backbone. The group of N‐substituted methacrylamides is the second one in the series of hydrophilic polymers arranged according to their increasing resistance to hydrolysis, and it follows immediately after the esters of methacrylic acid. Histological analysis has shown that the copolymer of N‐ethyl methacrylamide with methyl methacrylate is the best tolerated polymer of this group. In the case of copolymers with butyl acrylate and butyl methacrylate, in the first days after implantation a stronger and more cellular capsula was formed, and an inflammation was observed in the surroundings of the encapsulated implant. Starting from day 30, however, no differences are found in the encapsulation, and the result of healingin of all the polymers is always favorable. No cancerogenic effects were observed; calcification was found only sporadically in the case of the copolymer with butyl methacrylate.
The amount of tin in the γ1 phase of dental amalgam
Authors: Johnson L. B. 
Published: December 2004

AbstractSpherical‐particle Ag‐Sn alloy powders containing 4.3, 8.3, 12.0, 15.4, 18.5, 21.4, and 24.1 atomic per cent Sn were obtained. Amalgams from these alloys were examined by x‐ray diffraction and metallography for the presence of the γ2 phase and the γ1 → β1 phase transformation. A single amalgam of the approximate composition of dental amalgam was prepared from a melt at high temperature and pressure and likewise examined.Results showed that the solubility of Sn in Ag‐Hg is about 7 atoms of Sn per unit cell of the γ phase. As clinically prepared, the γ1 phase of dental amalgam contains, however, only about 5 atoms of Sn per unit cell. These 5 atoms, nevertheless, result in a very considerable stabilization of this phase due to the increase in its electron concentration.
The need for radiopaque denture base materials: A review of the literature
Authors: Chandler H. H. , Bowen R. L. , Paffenbarger G. C. 
Published: December 2004

AbstractThe need for esthetic and functionally acceptable radiopaque denture base materials is reflected by numerous reports of patients who ingested or aspirated portions of dentures and reports of difficulties encountered in the removal of these dentures because they could not be located radiographically.The type of denture most commonly ingested or aspirated is a maxillary partial consisting of a palatal piece to which is attached one or more anterior teeth. It may or may not have clasps. Ingestion or aspiration of the foreign body commonly occurs when either broken or ill‐fitting dentures are being worn. Few cases have been reported where patients swallowed portions of complete dentures.Previous attempts at providing radiopacity have included addition of heavy metal salts or radiopaque inserts to denture base resins. None of these attempts has been entirely successful.Elimination of dentures as foreign bodies requires a greater effort toward preventive measures by the dentist and the patient. When dentures are swallowed or inhaled, the dentist should immediately seek medical assistance for the patient. The common symptomless period following ingestion or aspiration should not lead the dentist to believe that there will not be serious subsequent complications.
Solute transport across polyelectrolyte complex membranes
Authors: Ryu Seh Man , Miller Irving F. 
Published: December 2004

AbstractThe transport of glucose and urea under electro‐osmosis across two polyelectrolyte complex membrances and two othermembranns, for comparison, was analyzed in detail, both experimentallyand theoretically.The membranes were characterized by measurements of water content, concentration of coion and countrion in the membrane, and distribution coefficient of glucose and urea in the absence of electric current, as a function of external solution composition. In addition, fluxes of those solutes and solvent were measured as a function fo external solution composition and of electric currentThe observed phenomena were modelled by use of Fick's law of of diffusion, with electro‐osmosis treated simply as bulk flow. the effect of stirring was accounted for in terms of a boundars layer mass transfer coefficient.The results indicate a good fit of the model to the data for glucose. For urea, the results indicate substantial binding of urea to the membrane matrix and anomalous behavior in he boundary layer adjacent to the membrane.
Physical properties of a radiopaque denture base material
Authors: Chandler H. H. , Bowen R. L. , Paffenbarger G. C. 
Published: December 2004

AbstractPhysical properties were determied for radiopaque composite denture base materials consisting of poly (methyl methacrylate) as thematrix and 30, 40, and 50% by weight fo a singlane‐treated barum fluoride‐containing glass powder as the reinforcing filler. Specimens without glass were include for comparision.All of the materials met the requirements of Amerrican ental Association Specification No. 12 for Denture Base Polymer except that t6he material containing 50% glass had less deflection than the minimum required at the 5000‐gm load in transverse testing.There was little or no difference among thematerials with respect to hardness, in denation resistance, water sorption, color stability, and resistance to drop impact.Addition of glass of the 30% level decreased the transevers strenght while 50% means with no glass. In general, the addition of glass increased the time to reach only slight effect on densities, and Young's, bulk, shear, and flexural moduli, had only slight effect on solubility and decreased the cold‐cure repairability and the coefficient of linear thermal expanision.The solubility of the glass power was aboutfour times that of powdered porcelain teeth after 24 hr, and totaled 0.55% afeter 5 days.
Segmented polyurethane: A polyether polymer, II. Two years experience
Authors: Boretos John W. , Detmer Don E. , Donachy James H. 
Published: December 2004

AbstractSegmented polyurethane does not indiuce acute toxcity when subjected to intracutaneous and intravascular tests with mices and rabbits. Specimens, which have been implanted in dogs for 18 months, exhibit stability heretofore unattributed tothe general class of polyurethanes. Data on tensile properties, abraxion resistance when wet, tolerance to autoclaving, results of acute toxicity test, and stablity of long‐term implants are described along with appropriate means of processing the polymer into useful biomedial devices.