bluuebunny/crossref_metadata_2025_split huggingface dataset:
Microscopic observations of the wear of a tooth restorative composite in vivo
Authors: Abell A. K. , Leinfelder K. F. , Turner D. T. 
Published: December 2004

AbstractThe wear of a composite restorative material in the oral cavity was followed by examining impressions by scanning electron microscopy. It was demonstrated that filler particles protrude from the polymeric matrix and, eventually, are lost leaving holes in the surface. A measure of the rate of wear was obtained by following the reacession of the matrix on the faces of a large prominent particle. For a restoration that had been in place for 7 years, the average rate of wear over a further period of several months was estimated to be about 0.1 μm/day. For comparison, the gross wear of 2 mm over the entire 7‐year period gives a greater average rate of wear of 0.8 μm/day.
Relationship between release rate and surface concentration for heparinized materials
Authors: Basmadjian D. , Sefton M. V. 
Published: December 2004

AbstractMathematical models are used to predict surface concentrations that result from the release of heparin into flowing blood and stagnant or well‐mixed plasma. Two release rates—4 × 10−2 and 3 × 10−5 μg/cm2 min–are considered, which describe elution from an ionically heparinized material and from an immobilized heparin‐PVA hydrogel, respectively. When heparin is released at the higher rate into blood flowing in cylindrical tubes with dimensions characteristic of the vasculature, or annular tubes representative of catheter experiments, a minium surface concentration of 0.5 μg/mL is attained virtually at the tube inlet. Release at the lower rate requires tube lengths of several thousand meters to attain the same critical value. Similarly, heparin released from a suspension of beads at the higher rate leads to critical surface concentrations of 0.2 μg/mL within a fraction of a second in stagnant plasma, or ca. 5 s in a well‐mixed environment. At the lower release rate, 45 or 100 min must elapse before the same level is achieved. These results support the validity of 4 × 10−2 μg/cm2 min as a reasonable minimum release rate to produce a heparin microenvironment sufficient to prevent thrombosis. The lower rate is shown to be insufficient to generate a critical concentration, thus supporting the argument that heparin‐PVA does not owe its biological activity to a heparin microenvironment. The model equations can be applied to the release of any material to determine surface concentrations.
Biocompatibility test procedures for materials evaluation in vitro. I. Comparative test system sensitivity
Authors: Johnson H. J. , Northup S. J. , Seagraves P. A. , Garvin P. J. , Wallin R. F. 
Published: December 2004

AbstractRelative sensitivity of in vitro biocompatibility test systems was explored. Cellular responses of 12 standardized cell lines to 20 materials representing a range of toxicity were measured. Each cell line and material combination was tested in duplicate using four different culture methods, and each culture plate was examined by two graders. Results of the tissue culture assays were compared to those obtained for the same materials in vivo using a 5‐day rabbit intramuscular implant assay. Methods involving measurement of cellular growth (colony counts or present of confluence) in serumfortified media extracts of test samples were generally more sensitive and discriminating than those in which test materials were placed directly in cell cultures (measurement of zone of growth inhibition). There was good agreement between graders for all test methods. Antibiotics were not used in the test program. Based upon sensitivity, reproducibility, ability to discriminate materials, and grader agreement, 4 of the 12 cell lines and 2 of the 4 test methods appeared most suitable for screening and evaluation of materials. Agreement of results using these four cell lines with intramuscular implantation tests for the 30 materials ranged from 60 to 90%.
Macromolecular, histological, ultrastructural and immunocytochemical characteristics of the neointima developed within PTFE vascular grafts. Experimental study in dogs
Authors: Chignier Elza , Guidollet Jeanine , Heynen Yves , Serres Mireille , Clendinnen Guy , Louisot Pierre , Eloy Rosy 
Published: December 2004

AbstractThe nature and characteristics of the tissue that develops on the inner surfaces of vascular arterial PTFE prostheses have been investigated by histological, morphometrical, ultrastructural, and immunocytochemical criteria. The ability of this tissue to synthetize glycoproteins and glycosamino‐glycuronoglycans (previously called mucopolysaccharides) has been compared to that of the normal arterial wall. PTFE prostheses were used for carotid replacement in the dog and studied until the 90th postoperative day. These prostheses were mainly characterized by (1) a limited or even absent neointimal tissue proliferation; (2) the absence of an endothelial‐like structure on the prosthesis using scanning electron microscopy and immunocytochemical staining with rabbit antidog factor VIII‐related antigen sera; (3) limited activities of both microsomial enzymes (sialyl transferase and N‐acetyl‐glucosaminyl‐transferase) but marked xylosyl transferase activity; and (4) inverse qualitative distribution of the glycosaminoglycans, i.e., decrease of heparan sulfate and chondroitin‐6‐sulfate and increase of hyaluronic acid and dermatan sulfate. The absence of morphological evidence of an endothelial structure at the blood‐prosthesis interface even 3 months after implantation and the marked functional impairment in the biosynthesis of macromolecular components responsible for the normal blood‐vessel interface suggest that this newly developed tissue cannot be considered a true vascular endothelium.
Biochemical features of pseudomembrane at the bone‐cement interface of loosened total hip prostheses
Authors: Shoji Hiromu , Karube Shunji , D'ambrosia Robert D. , Dabezies Eugene J. , Miller Douglas R. 
Published: December 2004

AbstractBiochemical features of pseudomembrane formed at the bone‐cement interface of 13 failed total hip replacements were studied and histological examination of the pseudomembrane was conducted. The results of biochemical analyses revealed on average hydroxyproline, 86 μg/mg; water content, 57%; hexosamine, 12 μg/mg; glucosamine/galactosamine, 1.4%; and calcium, 2.1%. Approximately 78% of collagen was extracted with pepsin, whereas only 8 and 0.3% collagen were extracted with acetic acid and neutral salt, respectively. On further differential salting out of the extracted collagen, about 77% was type I collagen, 19% type III, and 2.6% type V. Unlike pseudoarthrosis of fracture, no type II collagen was identified. Overall biochemical features in the light of the histological appearance suggested that pseudomembrane resembles granulation tissue. Bone healing mechanisms at the bone‐cement interface appear to differ from that of fracture healing.
Strong composites of dimethylacrylates with 4‐methacryloxyethyl trimellitic anhydride
Authors: Atsuta M. , Nagata K. , Turner D. T. 
Published: December 2004

AbstractParticles of a lithium aluminum silicate, which had been treated with a silane coupling agent, were centrifuged either in an adduct of bisphenol‐A/glycidyl methacrylate (Bis‐GMA) or in a mixture of Bis‐GMA and methyl methacrylate. Polymerization was effected by heating with 2,5‐dimethyl‐hexane‐2,5‐dihydroperoxide. Flexural strength passed through an optimum value with increasing loading of the silicate. Inclusion of 4‐methacryloxyethyl trimellitic anhydride, 4‐META (5 wt % on monomer), increased the optimum flexural strength by about 20% (to 240 MPa). Evidence that 4‐META increased the adhesion of filler particles to the polymeric matrix was obtained by examination of fracture surfaces.
Gel route preparation of low fusing dental porcelain frit
Authors: Mabie C. P. , Menis D. L. , Whitenton E. P. , Trout R. L. , Metherate R. S. , Ferry C. H. 
Published: December 2004

AbstractDental porcelain frits have been prepared by the gel route, a procedure involving solubilization of alkalies, boron, rare earth, and other compounds in an alumina‐silica sol. Using this procedure, porcelain frits suitable for metal‐ceramic application have been prepared that fire to maturity at temperatures lower than current commercial porcelains. Solubilities, translucencies, thermal expansion coefficients, dilatometric softening temperatures, and flexure strengths are within the ranges of current commercial porcelains. The high degree of dispersion of pigments and phosphors made possible by gel route technology and the technology's ability to disperse crystalline phases to strengthen porcelain offers many processing advantages. Gel route technology also offers a great degree of freedom in modifying porcelain properties.
Separation of macrophages from mouse peritoneal exudate cells with substrata coated with chemically modified collagens
Authors: Kasai Shunji , Akaike Toshihiro , Miyata Teruo , Kunimoto Takehiko , Nitta Kazuo 
Published: December 2004

AbstractA cell‐separation technique was designed on the basis of specific interaction between macrophages and chemically modified collagens in the presence of serum. When unseparated mouse peritoneal exudate cells containing approximately 50% macrophages and 50% lymphocytes were incubated in dishes coated with unmodified and chemically modified collagens, only macrophages adhered more rapidly and in greater numbers to succinylated and methylated collagen than to unmodified collagen. The adherent macrophages could be easily detached from the substrata by divalent cation chelating agents. The purity and recovery of macrophages separated by this method were approximately 92–94% and 41–48%, respectively.
Water sorption in a bis(GMA)/TEGDMA resin
Authors: Söderholm Karl‐Johan 
Published: December 2004

AbstractSome water sorption–desorption properties of a heat‐cured copolymer of bisphenol‐A‐glycidyl methacrylate/triethylene‐glycol‐dimethacrylate [bis(GMA)/TEGDMA] were investigated during three sequential water sorption–desorption cycles at 60, 37, and 60°C. The results showed that the investigated polymer absorbed almost one molecule of water for each bis(GMA)/TEGDMA molecule, causing a volumetric expansion slightly smaller than the volume of the absorbed water. The determined mean value of the sorption and desorption diffusion coefficients for a specific cycle, here named the “true” diffusion coefficient, was about 1.5 × 10−8cm2s−1 at 60°C, decreasing to one‐third of that value at 37°C. Although there were differences in leaching between the two sorption–desorption cycles at 60°C, no differences in true diffusion coefficients were found during the two cycles at that temperature. However, the sorption process proceeded slower than the desorption process during the first cycle, while the opposite occurred during the second cycle. These variations could be an effect of leaching occuring during the first cycle at 60°C and also the effects of induced swelling stresses on the diffusion process.
Healing pattern of small caliber Dacron grafts in the baboon: An animal model for the study of vascular prostheses
Authors: Keough E. M. , Callow A. D. , Connolly R. J. , Weinberg K. S. , Aalberg J. J. , O'Donnell T. F. 
Published: December 2004

AbstractAlthough dogs have been used widely to study the healing of large caliber synthetic grafts, hypercoagulability probably makes the dog a poor model for studies of small caliber vascular prostheses. The baboon's coagulation system is similar to man's, but large caliber baboon grafts were reported to endothelialize rapidly. In this study the healing pattern of 4mm internal diameter Dacron carotid interpositon grafts in baboons was determined using specimens harvested at time points between 2 weeks and 18 months post‐implantation and examined with light and scanning electron microscopy. The luminal surface of baboon grafts in the acute healing phase (<1 month) was comparable to that reported in the literature for dogs. Baboon grafts did not completely endothelialize until 10–12 weeks post‐implantation. For work with small caliber vascular protheses, the dog appears to have no advantage over the baboon as an animal model on the basis of graft healing.
Applications and failure modes of percutaneous devices: A review
Authors: von Recum Andreas F. 
Published: December 2004

AbstractPercutaneous devices (PD) are designed to serve a variety of clinical and biomedical research purposes. Characteristically they are objects that permanently penetrate through a defect in the skin. The histological aspects of the implant skin interfacial reactions are reviewed in this article. A short description is presented of common applications of PDs. The five presently identified interfacial failure modes are described histologically with the aid of schematic drawings. These failure modes are marsupialization, permigration, avulsion, infection, alone or in combination. Single or multiple etiological factors may be responsible for these failure modes. These factors can be surgically created skin defects around the penetrating foreign implant, epidermal healing characteristics that prevent the formation of a suitable seal at the implant‐skin interface and mechanical forces that may disrupt dermal attempts to seal the interface. Eventually the interface becomes infected necessitating removal of the device. Terminology recommended for use in percutaneous device research is indexed and defined.
Design criteria for percutaneous devices
Authors: Grosse‐Siestrup Christian , Affeld Klaus 
Published: December 2004

AbstractA theoretical model of a percutaneous device is described. The model is split into several components, each with its own function. Special structures such as horns, hair, feathers, fingernails, hoofs, teeth, and antlers are taken as examples where nature has solved the problems of “percutaneous devices.” These structures have been regarded in relation to dimensional and structural differences of epidermis, dermis, and subcutis. Theoretical guidelines are described for the design of a prosthetic percutaneous device.
The mechanical strength of maxillary complete dentures
Authors: Vlissidis D. , Paipetis S. A. 
Published: December 2004

AbstractA complete study of the static and dynamic strength of complete maxillary dentures was undertaken. First, the denture base material was investigated in its various forms from the point of view of tension, creep, relaxation, fatigue, and the effect of a corrosive environment. Complete dentures were tested under static compression, and the distribution of stresses along the midline of the upper dentures was determined by means of strain rosettes and by reciprocating compression, the determination of their fatigue strength. The results were found to conform with experience as far as lifetime of complete dentures is concerned.
Mechanical properties of bone cement: A review
Authors: Saha S. , Pal S. 
Published: December 2004

AbstractMany authors have examined the mechanical properties of bone cement and the various factors that affect its mechanical behavior. This article presents a comprehensive survey on the reported mechanical properties of bone cement. Variables that influence the mechanical properties, such as handling characteristics, strain rate, loading modes, additives, porosity, blood inclusion, in vivo environment, temperature, etc. have also been reviewed. The importance of specifying these variables in reporting test results on the mechanical properties of bone cement is pointed out. Previous attempts to improve the mechanical properties of bone cement are also summarized. Future research areas important for fully characterizing the physical properties of PMMA are also suggested.
A canine ex vivo series shunt for evaluating thrombus deposition on polymer surfaces
Authors: Lelah Michael D. , Lambrecht Linda K. , Cooper Stuart L. 
Published: December 2004

AbstractA new acute canine ex vivo femoral A‐V series shunt experiment is described. Platelet and fibrinogen deposition on a series of up to ten different polymers may be tested in the same nonanticoagulated animal. The method reduces the time and expense associated with animal testing, and also allows for the simultaneous monitoring of platelet and fibrinogen deposition on a number of polymer surfaces. The series shunt technique was used to examine platelet and fibrinogen deposition on polyethylene, Silastic, polyvinylchloride, and oxidized polyethylene surfaces. Following an initial period of minimal deposition, platelet deposition increased dramatically to a peak by about 15–20 min of blood contact on all surfaces studied. The amount of adsorbed fibrinogen fell from initial levels to a minimum at about 5–10 min of blood contact and then increased to a peak at about the same time as observed for the platelet response. Oxidized polyethylene was the most thrombogenic surface studied, followed by polyethylene, polyvinylchloride, and Silastic. Peak platelet and fibrinogen levels were found to be inversely related to flow rate over the range studied. In this experiment it appears that the interaction of blood components with a foreign surface in vivo or ex vivo is localized to the interface with the flowing blood. Within experimental errors, no effect of segment position or any downstream effects were observed. These results suggest that a series shunt may be used to investigate the short‐term interactions of blood with a number of test surfaces.
Fatigue properties of carbon‐ and porous‐coated Ti6Al4V alloy
Authors: Cook Stephen D. , Georgette Frederick S. , Skinner Harry B. , Haddad Ray J. 
Published: December 2004

AbstractA porous metal coating applied to a solid substrate implant has been shown,in vivo, to offer advantages over current polymethylmethacrylate cement fixation in orthopedic devices. These advantages may be lost, however, in devices requiring a sintering heat treatment to apply the coating since these treatments may have a detrimental effect on the substrate material mechanical properties. In addition, more biocompatible interface coating materials have come of interest with recent literature reports of metal ion release. These coatings may be of particular use in porous‐coated systems since the surface area of implant in contact with the surrounding tissues is greatly increased. This study investigated the effects that both a porous Ti6Al4V alloy coating and a ULTI carbon coating have on the fatigue properties of a Ti6Al4V alloy substrate system. The fatigue properties of uncoated as‐received, uncoated sinter heat treated and notched Ti6Al4V material were also investigated. The results of this study revealed endurance limits for Ti6Al4V alloy tested with a rotating beam system of 617 MN/m2(uncoated as‐received), 624 MN/m2(ULTI carbon‐coated), 377 MN/m2(sinter heat treated), 220 MN/m2(notched) and 138 MN/m2(porous‐coated). No effects on fatigue properties were observed when testing the material in saline compared with air. The slight increase in fatigue strength for the carbon‐coated material is thought to be due to the increase in surface hardness resulting from the formation of titanium carbides on the surface. The low‐endurance limit of the porous‐coated material is due to both the transition from the as‐received equiaxed microstructure to a lamellar microstructure upon sintering and to the notch effect created by the porous coating.
Release of corrosion products by F‐75 cobalt base alloy in the rat. I: Acute serum elevations
Authors: Koegel A. , Black J. 
Published: December 2004

AbstractThe release of corrosion products by implants has become a matter of concern. Using a microsphere model, the release of chromium, cobalt, and nickel, secondary to implantation of various surface area exposures of F‐75, a cast cobalt‐chromium alloy, was studied over a 30 day period in the rat. Dose related elevations were observed in the serum concentration of chromium and cobalt but not of nickel, with the maxima being achieved at 3 days after metal implantation followed by declines in concentration. The chromium elevation, approximately twelvefold for a surface area to body weight (SA/BW) ratio of 300 x is similar to that previously reported in patients receiving total hip replacement arthoplasties. However, the cobalt elevation, twentyfold for a SA/BW ratio of 300 x, has not been previously observed. These serum concentration changes are as yet unexplained, but are probably not due to fibrous capsule maturation or alloy repassivation.
Characterization of plasma polymerized silicone coatings useful as biomaterials
Authors: Chawla Attar S. , Sipehia R. 
Published: December 2004

AbstractPlasma polymerization techniques were used to deposit a layer of filler‐free silicone rubber on a variety of substrate materials. The thickness of the deposited film was 0.5–0.8 m̈m. As it is the surface of the biomaterial that comes in direct contact with the body fluids, the surface of the biomaterial is of paramount importance. In this study, the plasma polymerized biomaterials were characterized. Thus, the scanning electron microscope (SEM) showed the surfaces to be smooth. To study the surface layer of the deposited polymer, Fourier‐transform infrared spectrometry in the attenuated total reflection (ATR) mode was used. The deposited material was indeed silicone polymer with adsorption bands at 1262, 1020, and 802 cm−1 for the SiCH3 bending, SiOSi stretching, and SiCH3 bending, respectively. To find the bonding nature of the polymer, electron spectrometry for chemical analysis (ESCA) was used. The silicone polymer was shown to be highly cross‐linked. To find the molecular weight between cross‐links, swelling studies were done. Thus the results of the study show that the plasma polymerization could produce a filler‐free silicone layer on a variety of substrate materials.
In situ immunoradiometric assay of fibrinogen adsorbed to artificial surfaces
Authors: Chuang Hanson Y. K. 
Published: December 2004

AbstractAn in situ immunoradiometric assay was devised to quantitate human fibrinogen deposited on hemodialysis membrane, Cuprophane, from in vitro exposure to fibrinogen solution and from ex vivo extracorporally clinical use. The method requires a monospecific 125I‐labeled antifibrinogen‐IgG purified by DEAE chromatography and immunoadsorption. The labeled antifibrinogen IgG was shown to react specifically with fibrinogen adsorbed and immobilized (by glutaraldehyde) on Cuprophane. Other plasma proteins such as human albumin, IgG, or α‐thrombin, adsorbed singly or coadsorbed with fibrinogen on the surface did not seem to affect the fibrinogen‐antifibrinogen reaction. The presence of blood cells such as platelets and granulocytes with fibrinogen on Cuprophane reduced only slightly the uptake of 125I‐antifibrinogen‐IgG. The examination of fibrinogen‐fibrin deposition on clinically used Cuprophane by this technique and by autoradiography of the same material following 125I‐antifibrinogen‐IgG conjugation indicated that the deposition of fibrinogen was heavy and heterogeneous. We concluded that this in situ method may be useful to monitor fibrinogen‐fibrin deposition and adsorption of other plasma proteins that occur under in vitro, ex vivo, and in vivo conditions.