bluuebunny/crossref_metadata_2025_split huggingface dataset:
Exposure to mercury vapor during setting, removing, and polishing amalgam restorations
Authors: Haikel Y. , Gasser P. , Salek P. , Voegel J. C. 
Published: December 2004

AbstractThe level of mercury vapors in the oral cavity was determined by analyzing 242 samples of intra‐oral air before and after removing, setting, and polishing dental amalgam. The analysis was effected using atomic absorption spectrometry in cold vapors with the detection limit of 6 μg/m3. A score of 1 to 3 was assigned to each restoration to adjust the differences of the amalgam sizes. The present study showed that the vapor was released during any procedure: removing, setting, and polishing amalgam. The mean levels were between 85 and 326 μg/m3. However, before the restorative procedures, no mercury vapors had been detected in the oral cavity. This investigation has also demonstrated a significant direct correlation between Hg vapor concentrations in intra‐oral air and the sizes of amalgam restorations during each procedure: removing, setting, and polishing. The statistic analysis showed no significant difference of mercury vapors in the oral cavity between the use or nonuse of water coolant during the amalgam polishing.
Amount and surface structure of albumin adsorbed to solid substrata with different wettabilities in a parallel plate flow cell
Authors: Uyen H. M. W. , Schakenraad J. M. , Sjollema J. , Noordmans J. , Jongebloed W. L. , Stokroos I. , Busscher H. J. 
Published: December 2004

AbstractIn this article we studied the adsorption of serum albumin to substrata with a broad range of wettabilities from solutions with protein concentrations between 0.03 and 3.00 mg · mL−1 in a parallel‐plate flow cell. Wall shear rates were varied between 20 and 2000 s−1. The amount of albumin adsorbed in a stationary state was always highest on PTFE, the most hydrophobic material employed and decreased with increasing wettability of the substrata. Increasing stationary amounts of adsorbed albumin were observed with increasing wall shear rates at the lowest protein concentration. Inverse observations were made at the highest protein concentration. Transmission electron micrographs of replicas from the albumin‐coated substrata showed that proteins were mostly adsorbed in islandlike structures on the hydrophobic substrata. The tendency to form islandlike structures was shear rate‐ and concentration‐dependent and disappeared gradually going to more hydrophilic substrata. On glass, the most hydrophilic material employed, a homogeneous, well distributed, fine knotted, reticulated structure was found. In conclusion, this study demonstrates that both the amount of adsorbed albumin as well as the surface structure of the adsorbed proteins are regulated by the substratum wettability. This observation may well account for the fact that substratum properties can be transferred by an adsorbed protein film to the interface with adhering cells or microorganisms.
Prevention of bioprosthetic heart valve tissue calcification by charge modification: Effects of protamine binding by formaldehyde3
Authors: Golomb Gershon , Ezra Vitoria 
Published: December 2004

AbstractCalcification is the principal cause of the clinical failure of bioprosthetic heart valves (BHV). Calcification occurs through an interaction of host and implant factors, mainly younger age and glutaraldehyde pretreatment, respectively. The hypothesis of this work was that an impaired balance between positively and negatively charged amino acids, due to the reaction with Lys and Hyl tissue‐collagen residues, expose affinity sites to Ca++. We further hypothesized that regardless of the cause(s) of BHV calcification, positive charge modification of the tissues will prevent their propensity to calcify. Modification of BHV tissue was obtained by covalently binding protamine sulfate, a polybasic peptide, via formaldehyde and subsequent glutaraldehyde tissue crosslinking. Protamine‐bound tissue exhibited stability properties (shrinkage temperature and resistance to collagenase digestion) similar to BHV tissue. Protamine‐treated tissue was less permeable to Ca++, and reduced staining was observed with positively charged dyes, indicating the presence of positively charged functional groups in the modified tissue. Significant prevention of calcification was exhibited by the p‐bound tissue in comparison to BHV tissue, 30.9 and 109 μg/mg calcium, respectively, after 30 days of subdermal implants in rats. The modification procedure resulted in stable, covalent links of approximately 10% w/w protamine with undiminished anticalcification properties, even after 1 year storage. The results support our hypotheses, and orthotopical heart valve replacements are required in order to completely evaluate the treatment efficacy and bio‐compatibility.
The effect of the extracorporeal shock wave lithotriptor on bone cement
Authors: Schreurs B. W. , Bierkens A. F. , Huiskes R. , Hendrikx A. J. M. , Slooff T. J. J. H. 
Published: December 2004

AbstractFor the purpose of studying its applicability for acrylic cement removal during total hip revision surgery, experiments with an extracorporeal shock wave lithotriptor were carried out. High‐energy shock waves (HESW) were focussed on discs of polymethylmethacrylate bone cement. The average discharge was 18.1 kV; the number of shock waves 0, 100, 250, 500, 1000, and 2000; the application rate was 85 shocks/min. Macroscopic or radiographic effects were not in evidence. Microscopically, typical lesions in a small concentric focal area with a diameter of 8.5 (± 2.5) mm were found. The individual lesions were smaller than 0.1 mm, and displayed characteristic shapes. The area porosity increased with the number of shocks. The maximal area porosity caused by the HESW, measured by quantitative microscopy, was 4% after 2000 shock waves. The lesions were also studied by scanning electron microscopy. It can be concluded that HESW causes only microscopic lesions on the frontal surface of discs of bone cement, and that these lesions are small compared to the pores normally present in bone cement, when applied clinically.
Use of collagen film as a dural substitute: Preliminary animal studies
Authors: Collins Ronald L. L. , Christiansen David , Zazanis George A. , Silver Frederick H. 
Published: December 2004

AbstractCadaver grafts, laminated metallic materials, and synthetic fabrics have been evaluated as dural substitutes. Use of cadaver tissues is limited by fear of transmission of infectious disease while use of synthetic materials is associated with implant encapsulation and foreign body reactions. The purpose of this study is to evaluate the use of collagen film as a dural substitute. Collagen films prepared from bovine skin were used to replace the dura of rabbits and histological observations were made at 16, 28, 42, and 56 days postimplantation. Controls consisted of dura that was removed and then reattached. Control dura showed no signs of inflammation or adhesion to underlying tissue at 16 and 28 days postimplantation. By 56 days postimplantation, extensive connective tissue deposition was observed in close proximity to adjacent bone as well as pia arachnoid adhesions. Implanted collagen film behaved in a similar manner to control dura showing minimal inflammatory response at all time periods. At 56 days postimplantation collagen film appeared strongly infiltrated by connective tissue cells that deposited new collagen. The results of this study suggest that a reconstituted type I collagen film crosslinked with cyanamide acts as a temporary barrier preventing loss of fluid and adhesion formation. It is replaced after approximately 2 months with host collagen with limited inflammatory and fibrotic complications. Further studies are needed to completely characterize the new connective tissue formed as well as long‐term biocompatibility and functioning of a reconstituted collagen dural substitute.
The importance of the diffusive transfer of tints in the technology of tinting of soft contact lenses
Authors: Polishchuk A. Ya. , Iordanskii A. L. , Zaikov G. E. , Varshavsky V. L. , Yagodkina T. A. , Dubova I. G. , Madyuskin N. N. 
Published: December 2004

AbstractThis paper deals with the kinetics of tint transfer in soft contact lenses. A mathematical model taking into account both diffusion and chemical reactions is proposed and physicochemical parameters are determined. It is shown that bulk tinting is more effective in practice than surface tinting.
Effect of silicone rubber surface on the calcium balance of human serum
Authors: Rosanova Irina , Sevastianov Victor , Kim Sung Wan 
Published: December 2004

AbstractThe nature and mechanism of calcium complexation with human serum components in the presence of silicone rubber were assessed in in vitro model experiments. Silicone rubber samples were incubated for 67 h in serum of both physiologic calcium concentrations and induced hypercalcemic levels. Physiologic calcium incubation decreased the intrinsic and nth binding site association constants by factors of 2 and 4, respectively, from initial serum values. Incubation with silicone rubber did not change the association constants. Hypercalcemia incubation lowered the intrinsic and nth binding site association constants by 39 and 61%, respectively. Polymer incubation increased the intrinsic association constant and decreased the number of binding sites by a factor of 2. With initial binding site association constants unperturbed by incubation and Hill coefficients equivalent to 1, complexation was noncooperative and binding sites were considered to be identical and independent. Both Scatchard and Hill plots show nonlinearity for the polymer incubation case giving two distinct linear regions. This is indicative of cooperative binding for incubation with polymer; the Hill coefficient for the physiologic calcium concentration range was 0.97, while the coefficient for the hypercalcemic calcium range was 6.
A study of the fatigue properties of small diameter wires used in intramuscular electrodes
Authors: Scheiner Avram , Thomas Mortimer J. , Kicher Thomas P. 
Published: December 2004

AbstractSingle and multi‐strand stainless steel and cobalt‐nickel alloy wires, with strand diameters from 26 to 46 μm, were fatigue tested using a modified rotating bending test to determine what factors are most important in controlling fatigue life. The relation between cyclic strain and cyclic life was determined for each material by cyclically straining test specimens at various strain ranges and recording the number of cycles to failure. The results show that (a) the fatigue curves of the 316LVM, MP35N, DBS, and Syntacoben wires are very similar and have many of the same fatigue characteristics of specimens of large cross section. (b) Multi‐stranded wires have the same average fatigue life as their individual constituent strands but the variance of that life is smaller (c) Deformities in the wire, which are created during the manufacturing, appear to have the effect of shortening the fatigue life of these small section wires. (d) Observation of wire fracture surfaces show a relatively small crack propagation zone and a large fast fracture zone suggesting that most of the fatigue life of these small wires is in the original crack formation, which creates a large stress concentration and quickly leads to wire failure, (e) The size of the wire cross sectional area is of secondary importance compared to the amplitude of the maximum cyclic strain of the individual strands in determining fatigue life of the cable. To maximize the fatigue life of electrodes in vivo, the highest fatigue life for a given bending radius of curvature is desired. This suggests wire strands should be manufactured at the smallest diameter possible (without introducing structural flaws) to maximize service life.
Student research award in the graduate degree candidate category, 17th annual meeting of the society for biomaterials, scottsdale, AZ may 1–5,1991. A mechanical investigation of fluorapatite, magnesiumwhitlockite, and hydroxylapatite plasma‐sprayed coatings in goats
Authors: Dhert W. J. A. , Klein C. P. A. T. , Wolke J. G. C. , van der Velde E. A. , de Groot K. , Rozing P. M. 
Published: December 2004

AbstractCeramic coatings of fluorapatite (FA), magnesiumwhitlockite (MW), and hydroxylapatite (HA), and noncoated Ti‐6Al‐4V alloy (Ti) implants were evaluated before and after implantation in an animal study. Cylindrical plugs were coated by plasma‐spraying with FA, MW, and HA. X‐ray‐diffraction patterns showed for FA and HA a crystalline and for MW, an amorphous‐crystalline coating structure. The plugs were implanted into the right femora and left humeri of 16 adult goats. Follow‐up periods were 12 and 25 weeks. The in vivo results were evaluated using push‐out tests and scanning electron microscopy. There were significant differences in push‐out strengths between femur and humerus. The FA and HA implants showed significantly higher push‐out strengths than the MW and Ti alloy implants, especially for the 12 week follow‐up period. Furthermore, at 12 week follow‐up period. Furthermore, at 12 weeks, MW showed significantly lower push‐out strengths than Ti alloy. SEM‐investigation of the interfaces revealed that FA did not degrade while both MW and HA showed extensive degradation at 12 and 25 weeks. In addition, the interface after push‐out testing showed for the MW, HA, and Ti alloy implants to be fractured at the implant‐tissue interface and for the FA to be fractured at the coating‐titanium interface.
Materials for enhancing cell adhesion by immobilization of cell‐adhesive peptide
Authors: Ito Yoshihiro , Kajihara Masako , Imanishi Yukio 
Published: December 2004

AbstractMaterials to enhance cell adhesion were synthesized by surface integration of peptide, Arg‐Gly‐Asp‐Ser(RGDS), which is an active‐site sequence of cell‐adhesive proteins. Polystyrene film was glowdischarged and graft‐copolymerized with acrylic acid. Then the peptide was immobilized to the poly(acrylic acid) grafts by using water‐soluble carbodimide. The cell‐adhesive activity of the RGDS‐immobilized film increased with increasing amount of immobilized peptide, and approached the activity of fibronectin(FN)‐immobilized film. The RGDS‐immobilized film was more stable against heat treatment and pH variation than the FN‐immobilized film. In addition, the RGDS‐immobilized film enhanced cell growth more strongly than the FN‐immobilized film.
Evaluation of biocompatibility, based on quantitative determination of the vascular response induced by material implantation
Authors: Bouet T. , Toyoda K. , Ikarashi Y. , Uchima T. , Nakamura A. , Tsuchiya T. , Takahashi M. , Eloy R. 
Published: December 2004

AbstractThe biocompatibility of nine different materials, including positive and negative references, 4 polyurethane based and 3 latex based materials was investigated by (1) cytotoxic assay using V79 Chinese hamster cells, (2) the thickness of inflammatory layer at 3 and 7 days after intramuscular implantation test, and (3) the course of the blood flow in tissue reaction around subcutaneously implanted materials using Laser Doppler Flowmetry (LDF) over 14 days following implantation. In addition, for some materials, different modes of sterilization were compared. Although the three methods explore different reactive systems, the material ranking obtained was highly similar for the three methods, suggesting a relative accuracy between them. For one latex however, an absence of cytotoxic effect in culture and a highly intense response by LDF investigation of the same order of magnitude as for the positive reference implant suggest that bioincompatibility may result from the material itself and cannot be exclusively investigated by the leaching of toxic components.
On the fractography of overload, stress corrosion, and cyclic fatigue failures in pyrolytic‐carbon materials used in prosthetic heart‐valve devices
Authors: Ritchie R. O. , Dauskardt R. H. , Pennisi F. J. 
Published: December 2004

AbstractA scanning electron microscopy study is reported of the nature and morphology of fracture surfaces in pyrocarbons commonly used for the manufacture of mechanical heart‐valve prostheses. Specifically, silicon‐alloyed low‐temperature‐isotropic (LT1)‐pyrolytic carbon is examined, both as a coating on graphite and as a monolithic material, following overload, stress corrosion (static fatigue), and cyclic fatigue failures in a simulated physiological environment of 37°C Ringer's solution. It is found that, in contrast to most metallic materials yet in keeping with many ceramics, there are no distinct fracture morphologies in pyrocarbons which are characteristic of a specific mode of loading; fracture surfaces appear to be identical for both catastrophic and subcritical crack growth under either sustained or cyclic loading. We conclude that caution should be used in assigning the likely cause of failure of pyrolytic carbon heart‐valve components using fractographic examination.
Degradation of medical‐grade polyurethane elastomers: The effect of hydrogen peroxide in vitro
Authors: Meijs Gordon F. , McCarthy Simon J. , Rizzardo Ezio , Chen Yi‐Chi , Chatelier Ronald C. , Brandwood Arthur , Schindhelm Klaus 
Published: December 2004

AbstractTreatment of Pellethane 2363‐80A—a medical‐grade poly(tetramethylene oxide)‐based polyurethane elastomer—with 25% (w/w) hydrogen peroxide at 100°C for times ranging from 24 h to 336 h led to significant decreases in ultimate tensile properties and decreases in molecular weight, both at the surface and in the bulk. IR spectral changes were similar to those observed after degradation in vivo. Differential scanning calorimetry showed that hydrogen‐peroxideinduced degradation was associated with greater order in the hard domain and greater mobility in the soft domain. Studies conducted with low‐molecular‐weight model compounds for the hard and soft segments confirmed that methylene groups adjacent to oxygen were susceptible toward oxidation. The extent of degradation of a series of commercial polyurethanes on treatment with hydrogen peroxide (25%, 24 h, 100°C) correlated well with their reported susceptibility to environmental stress cracking in vivo. © 1993 John Wiley & Sons, Inc.
Metal ion concentrations in retrieved polyethylene total hip inserts and implications for artifactually high readings in tissue
Authors: Meldrum Russell D. , Bloebaum Roy D. , Dorr Lawrence D. 
Published: December 2004

AbstractAlthough there are many studies which document high metal ion concentrations in clinically retrieved tissues surrounding total joint replacements, most investigations have remained cautious in their interpretation due to the artifactual influences of metal particulate.The possible contribution of polyethylene wear debris to artifactually high periprosthetic metal ion concentration readings has not been previously considered. This study documents the potential role of polyethylene particulate contamination in causing artifactually high metal concentration readings in tissues.The data showed metal ion contamination in the polyethylene was progressive at each stage of exposure to metal: from bar stock preparation, to manufacturing, to in vivo ambulation. The manufacturing and machining processes showed a statistically significant (P ≤ .05) increase in metal ion concentrations in the nonarticulated acetabular inserts over bar stock.The results of this study demonstrate that periprosthetic tissue and synovial fluid metal ion concentration data must be interpreted with caution due to possible artifactual problems associated with metal ion contaminated polyethylene particulate. © 1993 John Wiley & Sons, Inc.
Plasma protein adsorption to artificial ligament fibers
Authors: Stanislawski L. , De Nechaud B. , Christel P. 
Published: December 2004

AbstractThe adsorption of plasma proteins onto biomedical polymers is an important factor in the biocompatibility of biomaterials. We identified the plasma proteins adsorbed onto four polymeric fibers used for synthetic ligament replacement: polyarylamide, polylactic acid, polyester, and polypropylene. The adsorbed proteins were eluted and analyzed by one‐dimensional and two‐dimensional gel electrophoresis. Fibrinogen, albumin, IgG, high molecular weight kininogen (HMWK), and lipoproteins ApoA‐1 and ApoE were the major proteins adsorbed onto polyarylamide. The three others biomaterials bound albumin, fibrinogen, ApoA‐1, and ApoE; however, the proportions of proteins bound to each polymer differed. There was an inverse relationship between ApoA‐1 and fibrinogen binding for all four biomaterials; polyarylamide bound a high percentage of fibrinogen, but little ApoA‐1; polylactic acid, polyester, and polypropylene bound a high percentage of ApoA‐1, but little fibrinogen. These results support suggestions that low fibrinogen adsorption might be due to the preferential adsorption of Apo‐1. High fibrinogen binding to polyarylamide ligaments may favor fibroblast adherence, growth, and tissue repair. © 1995 John Wiley & Sons, Inc.
Adhesion of Staphylococcus epidermidis to biomedical polymers: Contributions of surface thermodynamics and hemodynamic shear conditions
Authors: Wang I‐Wen , Anderson James M. , Jacobs Michael R. , Marchant Roger E. 
Published: December 2004

AbstractAdhesion studies of Staphylococcus epidermidis RP62A were conducted using a rotating disk system to determine the roles of surface physicochemistry and topographies under physiologic shear conditions. Six materials were investigated: biomedical reference polyethylene and polydimethylsiloxane; argon plasma‐treated reference polyethylene (Ar‐PE); Silastic®; expanded polytetrafluoroethylene; and woven Dacron. All of the polymers except Dacron demonstrated reduced bacterial adhesion with increasing shear stress. Argon plasma treatment of polyethylene reduced the level of staphylococcal adhesion. Adsorption of human plasma proteins effected significantly lower numbers of adherent bacteria. The lowest adhesion was observed for Ar‐PE in 1% human plasma protein solution, whereas Dacron had the highest number of adherent bacteria. The high adhesion on Dacron was attributed to increased bacterial flux caused by topography‐induced turbulent flow and physical entrapment of the bacteria in the fiber interstices. The results indicate that the driving force for S. epidermidis adhesion is strongly influenced by substrate physicochemistry, but this may be dominated by physical forces such as shear and turbulence. © 1995 John Wiley & Sons, Inc.
Release of hexavalent chromium from corrosion of stainless steel and cobalt—chromium alloys
Authors: Merritt Katharine , Brown Stanley A. 
Published: December 2004

AbstractExperiments were undertaken to determine whether hexavalent chromium was released during corrosion of orthopedic implants. Uptake of chromium (Cr) by cells and separation using amberlite resin were the methods used to determine that hexavalent Cr was present. We used salts of chromium as trivalent chromium (chromic chloride) and hexavalent chromium (potassium dichromate) to verify that the amberlite separation technique separates hexavalent Cr into the upper phase and trivalent Cr into the lower phase. The use of the salts also verified that only the hexavalent Cr became red blood cell–associated and that most of this was intracellular rather than membrane bound. The use of the amberlite separation technique demonstrated that the hexavalent Cr in the red blood cells was rapidly reduced to trivalent Cr. Cellular uptake of chromium was documented in red blood cells following corrosion of stainless‐steel and cobalt–chromium implants in vivo, in the red blood cells of patients undergoing total joint revisions, and in fibroblasts subjected to products of fretting corrosion of stainless‐steel and cobalt–chromium implants. Thus, corrosion of implants can lead to the release of the biologically active hexavalent chromium into the body. This chromium is rapidly reduced to trivalent chromium in cells. © 1995 John Wiley & Sons, Inc.