bluuebunny/crossref_metadata_2025_split huggingface dataset:
Stress distribution in bone arising from loading on endosteal dental implants
Authors: Tesk J. A. , Widera O. 
Published: May 2005

AbstractResults of a preliminary study of stress in bone around dental implants are presented. Stress is calculated using the method of finite elements. Two blade type and one pin type implant are subjected to horizontal and to vertical forces of 19 lb. Differences in blade implant design do not alter the stress distribution significantly. The pin implant shows that most of the load is carried near the entrance into the bone, with a rapid fall in stress.
The biomechanics of the epiphyseal lines as a guide to design considerations for the attachment of prosthesis to the musculo‐skeletal system
Authors: Bechtol Charles O. 
Published: May 2005

AbstractThe configuration of epiphyseal lines in the growing mammal is extremely variable depending upon the principal stresses applied to the specific epiphysis in question. Because man is not highly specialized for rapid locomotion, the configuration of epiphysis in the human is not as well developed as that seen in animals specialized for rapid running, such as the artiodactyls. The several different typical configurations of the epiphyseal line are described and demonstrated in photographs using the deformed coordinate method. It is suggested that when coupling of porous structures, such as ceramics to bone, has been adequately worked out, configurations similar to those seen in the epiphyseal lines may be a successful method of attaching the prosthetic part to bone.
Mechanical properties of the bone‐porous biomaterial interface: Elastic behavior
Authors: Moyle D. D. , Klawitter J. J. , Hulbert S. F. 
Published: May 2005

AbstractThe possibility of evaluating the elastic moduli of the bone‐porous biomaterial interface by treating it as a two‐phase composite is discussed. Methods of placing bounds on the elastic moduli of such a composite are presented and applied to five materials currently being considered for use in porous prosthetic devices: 316 stainless steel, titanium, cobalt‐chromium‐molybdenum alloy (Vitallium), alumina (Al2O3), and high density polyethylene. The results show that when the prosthetic material becomes completely ingrown with bone, the elastic modulus of the composite becomes more compatible with bone. Titanium appears to be very favorable. Young's modulus for bulk titanium is about four times that of bone, while the fully ingrown composite has a Young's modulus approximately twice that of bone. Similar results obtain for the other elastic moduli. It is noted that the results for 316 SS apply to all surgical stainless steels, those for Co‐Cr‐Mo apply to other Co‐Cr alloys and those for titanium apply to alloyed titanium.
Corrosion product formation sequence on Cu‐rich amalgams in various solutions
Authors: Lin Jiin‐Huey C. , Marshall Grayson W. , Marshall Sally J. 
Published: May 2005

AbstractA single particle and four blended Cu‐rich amalgam systems were immersed in 37 °C solutions for 1–20 months in order to determine the characterization and sequence of corrosion product formation. X‐ray diffraction and SEM/EDS were used to characterize the products. The same sequence of formation occurred in all systems in Ringer's and 0.1% Ringer's solutions. The times at which each product formed varied with the brand of the amalgam and the concentration of the solution. The initial products were ZnSn(OH)6 in Zn‐containing systems and SnO2 in most other systems. Cu2O formed next, followed by CuCl2·3Cu(OH)2. Immersion in 1% Na2S yielded only HgS on all brands. A combination of 1% Na2S and Ringer's solution yielded CaSn(OH)6 after 2 months and Cu2O at later periods. Artificial saliva resulted in a retardation of corrosion product formation and only limited amounts of a Sn‐rich product could be found after 20 months. Interactions of the various components appear to alter the nature and rate of corrosion product formation on these systems and additional systematic investigations are necessary to understand the influence of these interactions on corrosion.
The mechanisms of passive dissolution of titanium in a model physiological environment
Authors: Healy Kevin E. , Ducheyne Paul 
Published: May 2005

AbstractThe surface chemistry, oxidation, and dissolution kinetics of titanium were measured to establish the mechanisms of passive dissolution in physiological environments. Titanium thin films were immersed in 8.0 mM ethylenediamine‐ tetraacetic acid in simulated interstitial electrolyte (EDTA/SIE) and maintained at 37°C, 10% O2, 5% CO2 and 7.2 pH for periods of time up to 3200 h (133 days). Two immersion schemes were employed: the integral sequentially determined the titanium released into a solution of accumulated dissolution products; and the differential continuously replenished the test solution. The solutions were analyzed for titanium by electrothermal atomic absorption spectrometry (EAAS), and the sample surfaces were analyzed by Auger electron spectroscopy (AES) and x‐ray photoelectron spectroscopy (XPS) to determine oxide composition, stoichiometry, and thickness. Prior to immersion two types of hydroxyl (OH) groups were distinguished on the TiO2 surface. Upon immersion, the chemistry of the surface changed as a function of immersion: the presence of OH groups increased and P (nonelemental) was detected at the surface. The dissolution kinetics obeyed a two‐phase logarithmic model, where the transition between phases occurred simultaneously with the adsorption of the P‐containing species. The dissolution kinetics depended on surface reactions, electric field strength, and molecular diffusion. These mechanisms explain the observed dependence of dissolution kinetics on the properties of the surface oxide and solution ligands.
Ex vivo and in vitro platelet adhesion on RFGD deposited polymers
Authors: Kiaei David , Hoffman Allan S. , Hanson Stephen R. 
Published: May 2005

AbstractClinical applications of small‐diameter synthetic vascular grafts are hindered by their highly thrombogenic surfaces. To develop vascular grafts that resist thrombotic occlusion, a radio frequency glow discharge (RFGD) process was employed to modify the surface of existing graft materials. Ultrathin coatings of RFGD polymers of ethylene (E), tetrafluoroethylene (TFE), and hexamethyldisiloxane (HMDS) were deposited on the lumen of Dacron grafts. Surfaces were characterized by electron spectroscopy for chemical analysis (ESCA). The effect of glow discharge treatments on plateletgraft interactions was evaluated in an ex vivo baboon shunt model. Following placement of an untreated or RFGD‐ treated graft in the shunt, deposition of 111Indium‐labeled platelets was monitored for 60 min by γ camera imaging. Untreated Dacron rapidly accumulated large numbers of platelets, reaching a plateau i n 60 min. HMDS‐ and TFE‐treated Dacron had significantly lower levels of platelet deposition compared to the untreated control. In contrast, the ethylene treatment of Dacron augmented platelet deposition, making it the most platelet‐ adherent surface studied. In vitro studies were also performed using untreated and RFGD‐treated poly (ethylene terephthalate) (PET) coverslips. ESCA verified that the surface composition of the untreated and RFGD‐treated coverslips were virtually identical to their untreated and treated Dacron graft counterparts. Samples were incubated in washed baboon platelet suspensions for 2 h at 37°C. Platelet adhesion on the untreated PET was relatively high, and many of the platelets had a completely spread morphology. The HMDS and TFE treatment of PET reduced the number of adherent platelets and prevented platelet spreading on the surface. Platelet adhesion and spreading on the ethylene‐treated surface was the highest among the four studied. There is a remarkable linear correlation of the ex vivo and in vitro platelet adhesion data.
Glow discharge plasma deposition of tetraethylene glycol dimethyl ether for fouling‐resistant biomaterial surfaces
Authors: Löpez Gabriel P. , Ratner Buddy D. , Tidwell Caren D. , Haycox Claire L. , Rapoza Richard J. , Horbett Thomas A. 
Published: May 2005

AbstractThe glow discharge plasma deposition (GDPD) of tetraethylene glycol dimethyl ether is introduced as a novel method for obtaining surfaces that are resistant to protein adsorption and cellular attachment. Analysis of films by x‐ray photoelectron spectroscopy and several biological assays indicate the formation of a foulingresistant, PEO‐like surface on several substrata (e.g., glass, polytetrafluoroethylene, polyethylene). Adsorption of 125I‐radiolabelled proteins (fibrinogen, albumin and IgG) from buffer and plasma was very low (typically <20 ng/cm2) when compared to the untreated substrata, which exhibited much higher levels of protein adsorption. Not all coated substrata adsorbed equal amounts of protein (e.g., coated glass samples typically adsorbed more protein than coated polyethylene or coated polytetrafluoroethylene samples), suggesting that the substratum used may affect the amount of protein adsorbed. Measurement of dynamic platelet adhesion, using epifluorescent video microscopy, and endothelial cell attachment further demonstrates the short‐term nonadhesiveness of these surfaces.
Difference in tumor incidence and other tissue responses to polyetherurethanes and polydimethylsiloxane in long‐term subcutaneous implantation into rats
Authors: Nakamura A. , Kawasaki Y. , Takada K. , Aida Y. , Kurokama Y. , Kojima S. , Shintani H. , Matsui M. , Nohmi T. , Matsuoka A. , Sofuni T. , Kurihara M. , Miyata N. , Uchima T. , Fujimaki M. 
Published: May 2005

AbstractThe long‐term (1‐ and 2‐year) adverse tissue responses including tumor formation by subcutaneous implanation of polyurethanes (PUS) and silicone (Sil) films intorats were compared. The weight‐averaged molecular weights (Mw) of the PUS prepared from 4,4′‐diphenylmethanediisocyanate, poly (tetramethyleneglycol) of M, = 1000 and 1,4‐butanediol are 220,000 (U‐4), 124,000 (U‐6), and 55,600 (U‐8). The 50:50 mixed film of U‐6 and silicone (U‐b/sil) was prepared by rollmixing of the noncured silicone and the U‐6 solution followed by evaporation of the solvent and heat‐curing at 70°C. The tissue responses around implants were classified into four groups as follows: (A) tumor, (B) atypical cell proliferation accompanied by preneoplastic changes, (C) cell proliferation without preneoplastic changes, (D) no obvious responses. In both implantation periods, the PUS gave higher incidents of the adverse responses including tumor formation in comparison to Sil. No significant molecular weightdependent trend was found in a 1‐year study using U‐4, 6, and 8. Significant PU‐dose‐dependent trends were found in a 2‐year study: the total active incidence (A + B + C), U‐6(22/29) > U‐6/si1(11/29) > sil(7/28); tumor incidence (A), U‐6(11/29) > U‐6/si1(2/29) = si1(2/28). No detectable amounts of 4,4′‐methylenedianiline (MDA) were found in the PUS. The methanol extracts from the PUS were negative in the mutagenicity tests. These indicate no relationship between the tumor formation by the PU films and the mutagenicities of the chemicals (mainly oligomers) leached from the PUs.
Postadsorptive transition in fibrinogen adsorbed to polyurethanes: Changes in antibody binding and sodium dodecy1 sulfate elutability
Authors: Chinn Joseph A. , Posso Sylvia E. , Horbett Thomas A. , Ratner Buddy D. 
Published: May 2005

AbstractResidence time‐dependent changes in fibrinogen after adsorption to six different polyurethanes were examined by measuring polyclonal antifibrinogen binding to the adsorbed protein. The amount of adsorbed fibrinogen that could be eluted by sodium dodecyl sulfate (SDS) was also measured. Baboon fibrinogen was first adsorbed from dilute plasma to the polymers, which were then stored in either buffer or buffered albumin solution prior to testing. Subsequently, the amount of antifibrinogen bound by the adsorbed fibrinogen was measured using a direct enzyme linked immunosorbent assay (ELISA). Alternatively, the surface with the adsorbed fibrinogen was soaked in a 3% SDS solution, and the amount of retained 125I‐radiolabeled fibrinogen was measured. With increasing residence time, decreases in both antibody binding and the SDS elutability of the adsorbed fibrinogen occurred, but the rate of change was dependent on the polyurethane to which the fibrinogen was adsorbed. In addition, the antibody binding per unit of adsorbed fibrinogen, when measured immediately after the adsorption step, varied by approximately a factor of 3 among the various polyurethanes. When the protein‐coated surfaces were stored in buffered albumin solution rather than buffer, the decrease in the reactivity of fibrinogen with residence time did not occur on some of the surfaces. This study shows that the chemical properties of the adsorbing surface influence the rate at which adsorbed fibrinogen undergoes change. The significance of the polymer‐dependent changes in adsorbed fibrinogen with respect to blood reactions with polymers is discussed.
Biocompatibility studies on plasm polymerized interface materials encompassing both hydrophobic and hydrophilic surfaces
Authors: Johnson Steven D. , Anderson James M. , Marchant Roger E. 
Published: May 2005

AbstractThe biocompatibility of radiofrequency plasma polymerized films (<100 nm thick) deposited on biomedical polymer supports has been characterized by in vitro and in vivo methods. The polymer interface materials covered a wide range of elemental composition and surface properties, and were prepared from N‐vinyl‐2‐ pyrrolidone, γ‐butyrolactone, n‐hexane, and hexamethyldisilazane (PPHMDSZ). The biocompatibility studies showed that the interface materials were noncytotoxic to mouse and human fibroblasts, as shown by morphologic evaluation, and by determination of extracellular LDH; and they did not stimulate interleukin‐1‐like production from human monocytes, as indicated by a thymocyte proliferation assay. The human fibroblast proliferation assay showed that three of the polymers supported cell growth at levels comparable to, or greater than, polymer controls, while the hydrophobic PPHMDSZ inhibited both cell attachment and proliferation. The response to subcutaneous implantation for all test materials was indicative of biocompatibility, with rapid resolution of the acute phase response and normal wound healing. The wide range of composition and surface properties for the plasma polymerized films evaluated in this study suggest that this general class of materials is likely to exhibit excellent biocompatibility.
In vitro and in vivo digestion of collagen covalently immobilized onto the silicone surface
Authors: Okada Toshiyuki , Ikada Yoshito 
Published: May 2005

AbstractIn order to study the in vivo digestion of immobilized collagen and gelatin, these proteins labeled with 125I or fluorescein isothiocyanate (FITC) were covalently immobilized onto silicone surfaces, which were grafted with acrylic acid to introduce carboxyl groups, and implanted subcutaneously in rats and mice. When the proteins were labeled with FITC, the amount of proteins immobilized decreased with the increase of the number of FITC molecules conjugated with the protein molecule. In the wet state, FITC conjugated with the proteins was less stable than 125I. Approximately half of the amount of the immobilized proteins was digested in vivo within the first week and until 5 weeks after implantation the proteins were gradually digested. At that time, the amount of the proteins remaining on the silicone surface ranged from 0.6 to 1.0 μg/cm2, which was several times larger than the amount of an assumed monolayer adsorption of proteins. Even after 15 weeks, the amount of proteins remaining on the silicone was almost the same as after 5 weeks. No significant difference in digestion was observed between collagen and gelatin, regardless of the labeling agent. Because of less stability and easier handling of FITC and higher stability and more difficult handling of 125I, FITC seems more suitable for short‐term and 125I for long‐term studies. © 1992 John Wiley & Sons, Inc.
Changes in fibrinogen adsorbed to segmented polyurethanes and hydroxyethylmethacrylate‐ethylmethacrylate copolymers
Authors: Slack S. M. , Horbett T. A. 
Published: May 2005

AbstractFibrinogen adsorption from blood to biomaterials may regulate platelet adhesion and thrombus formation because of fibrinogen's central role in the coagulation cascade and its ability to bind specifically to the platelet membrane glycoprotein (GP) IIb‐IIIa. Adsorption of fibrinogen from blood plasma to many materials exhibits a maximum with respect to plasma dilution and exposure time (the Vroman effect). In this study fibrinogen adsorption to several polymers was examined to ascertain the influence of controlled changes in surface chemistry on the Vroman effect. The materials included hydroxyethylmethacrylate‐ethylmethacrylate (HEMA/EMA) copolymers, Biomer, and a series of segmented polyurethanes (PEUs), two of which contained fluorinated chain extenders. Each material exhibited maximal adsorption of fibrinogen at intermediate plasma concentrations. Little effect of soft‐segment type or molecular weight was observed and no significant differences in fibrinogen adsorption to the fluorinated PEUs were seen. Changes in the strength of fibrinogen attachment to these materials with time after adsorption were also assessed. Fibrinogen adsorbed for 1 min was displaced more readily by blood plasma than that adsorbed for 1 h, regardless of the material. The more hydrophobic polymers exhibited greater retention of adsorbed fibrinogen. In addition, the fraction of fibrinogen retained by polyethylene depended on the amount of fibrinogen adsorbed to the surface, being greatest when the surface loading was the least. These studies indicate that spreading or transition of adsorbed fibrinogen molecules from a weakly to tightly bound state is a general consequence of protein adsorption to solid surfaces. © 1992 John Wiley & Sons, Inc.
111Indium labeling of microorganisms to facilitate the investigation of bacterial adhesion
Authors: Ardehali R. , Mohammad S. F. 
Published: May 2005

AbstractThe ability of bacteria to adhere to polymeric interfaces has attracted considerable attention in recent years. Metabolic labeling of microorganisms with 35S‐methionine or other β‐emitters is commonly utilized for quantification of bacterial adhesion to biopolymers. Since the use of these isotopes is cumbersome, the possibility of labeling the microorganisms with 111Indium, a strong γ‐emitter, was explored. This report demonstrates that bacteria can be easily labeled with 111Indium. Staphylococcus aureus, Staphylococcus epidermiids, and Pseudomonas aeruginosa were labeled with either 111Indium‐oxine or 35S‐methionine; and labeling efficiency, retention of incorporated labels, and growth kinetics of labeled bacteria were compared under identical experimental conditions. Bacteria labeled with 111In‐oxine incorporated approximately 90% of radioactivity within 10 min, whereas 35S‐methionine incorporation required many hours of incubation. Both the incorporated isotopes were gradually released by rapidly growing bacteria into the suspension medium. Of the total incorporated labels, approximately 20% 111In and 15% 35S were released in the surrounding medium every 24 h. No release of incorporated labels occurred when cells were fixed with 2.5% buffered glutaraldehyde. Growth kinetics and scanning or transmission electron microscopic analysis showed no detectable differences among control (nonlabeled), 111In‐, or 35S‐labeled bacteria. Labeling of bacteria with 111In‐oxine does not interfere with bacterial adherence. These observations suggest that 111In incorporation provides a simple and rapid method of labeling of microorganisms. Compared to currently available techniques, the use of 111In‐labeled bacteria will facilitate the quantitation of adherent bacteria to interfaces. © 1993 John Wiley & Sons, Inc.
Plasma protein adsorption to hemodialysis membranes: Studies in an in vitro model
Authors: Parzer Sabina , Balcke Peter , Mannhalter Christine 
Published: May 2005

AbstractUpon interaction of whole blood with foreign materials, heterogeneous protein films are deposited onto the artificial surface (eg, hemodialysis membranes). The composition of these protein films subsequently affects various processes, eg, thrombogenesis or activation of the complement system. We developed an in vitro model with which we can identify and study proteins interacting with capillaries during hemodialysis. Using this model we studied the cuprophane dialyzer GFS 120 (CP) and the polymethylmetacrylate membrane Filtryzer B2‐1.2 (PMMA). Heparinized whole blood from healthy young volunteers was dialyzed on an extracorporeal dialysis machine. After the dialysis procedure the adsorbed material was eluted from the hemodialysis membranes by different eluants and subsequently analyzed by sodium dodecyl sulfate‐polyacrylamide gel electrophoresis (SDS‐PAGE) and immunoblotting. A number of proteins could be identified in the eluates of both membrane types. Interestingly, platelet glycoproteins could only be found in PMMA eluates. Albumin, IgG, and antithrombin III were mainly present in the cuprophane eluates. Fibrinogen was demonstrable in all eluates, but in relatively low amounts, and the protein was significantly degraded. Degradation products of antithrombin III and complement factor 3 could also be identified. The process causing the degradation has not yet been identified, but may be due to proteases released from damaged cells. © 1993 John Wiley & Sons, Inc.
Human umbilical vein endothelial cell culture on heparin‐like microcarriers
Authors: Najab‐Benhayoun M. , Serne H. , Jozefowicz M. , Fischer A. M. , Brisson C. , Sultan Y. 
Published: May 2005

AbstractBiospecific functional polymers, i. e., polymers randomly substituted with specific chemical functional groups, were designed to interact with living systems. Interactions between polystyrene sodium sulfonate (PSSO3Na) and insulin secreting RINm5F cells have been previously described.For the sake of comparison, interactions of PSSO3Na with human umbilical vein endothelial cells (HUVEC) were studied. In this case, the interaction is indirect, i.e., mediated by a binding protein, fibronectin (Fn). This was evidenced by HUVEC culture on Fn precoated PSSO3Na microcarriers. The interactions between PSSO3Na and HUVEC result in a biologically normal proliferation of cells and synthesis and secretion of Von Willebrand Factor (VWF). These results show that different biospecific interactions may occur between cells in culture, binding proteins and polymers randomly substituted with suitable functional groups. HUVEC, when cultured on heparin‐like microcarriers, behave differently from other cells like RINm5F, whose interaction with the same polymers is not mediated by binding proteins. © 1993 John Wiley & Sons, Inc.