bluuebunny/crossref_metadata_2025_split huggingface dataset:
Long‐term behavior of bovine collagen membrane used as vascular substitute. Experimental study in rats
Authors: Chignier Elza , Eloy Rosy , Huc Alain , Gimeno René , Gleizal Claudine 
Published: December 2004

AbstractThe aim of the present study was to evaluate the sequence (1) of the immediate and (2) the mid/long‐term organization of the blood interface of a collagenous membrane used as vascular substitute in rats. The implants were prepared from calf skin type I insoluble collagen, obtained after acidic dispersion, in absence of chemical or tanning treatment. They were used to patch an aortic defect by means of microsurgical techniques. The animals were sequentially sacrificed for immediate hemocompatibility studies at 10 s, 30 s, 10 min, 3 h, and 6 h, for long‐term analyses of the organization of the blood material interface at the 7th, 15th, 45th, 60th, 90th day following the surgery and each month until 14 months after aortic replacement. The superficial immediate events at the blood patch interface demonstrated erythrocytes heavily engulfed in a thin but dense fibrin mesh both at the patch and at the adjacent aortic wall surfaces. Neither adherent platelet nor platelet aggregate were detectable on the collagen patch surface. This fibrinoerythrocytic membrane covered the patch completely at 60 s and at 3 h the deposit was limited to 5–6 erythrocyte layers as confirmed by histology. It did not further develop on the 7th day. At the blood‐collagen interface there progressively developed a tissue composed of active myofibroblasts, collagen bundles, and elastic fibers. After 4 months, nests of fibroendothelial cells were present, and between 6 and 14 months surface cell differentiation, although complete on the adjacent aorta was still incomplete on the bovine collagen patch, amorphous fibers, and fibroendothelial cells coexisting. Heterologous patch debris were still present 14 months after implantation and were associated with macroscopic and ultrastructural calcification, which need further investigations concerning the exact nature and mechanism of mineralization of vascular substitutes of biological nature.
The effect of surface treatments on the interface mechanics of LTI pyrolytic carbon implants
Authors: Thomas K. A. , Cook S. D. , Renz E. A. , Anderson R. C. , Haddad R. J. , Haubold A. D. , Yapp R. 
Published: December 2004

AbstractA mechanical and histological evaluation of LTI pyrolytic carbon implants was undertaken to determine the effect of various surface treatments on the retention characteristics of the implants. Five types of surfaces were evaluated, including as‐deposited, fine grit‐blasted, coarse grit‐blasted, ground, and plasma oxygenated. The four surface treatments were chosen in an attempt to emulate the morphology of the as‐deposited implants. The implants were evaluated in vivo by placement transcortically in the femora of adult mongrel dogs for periods of 12 to 24 weeks. Although the as‐deposited implants exhibited the greatest interface strength at 12 weeks the results of mechanical testing after 24 weeks implantation indicated no statistically significant difference among the interface strength values or among the interface stiffness values of the implants. The histologic response of the implants was similar; while all implants exhibited areas of direct implant‐bone apposition, the as‐deposited implants exhibited this behavior to the greatest extent. Thus the ability to duplicate the biological response to the as‐deposited LTI carbon surface appears possible by one or more of the treatments evaluated.
Mechanical stability of elastomeric polymers for blood pump applications
Authors: Hayashi Kozaburo , Takano Hisateru , Matsuda Takehisa , Umezu Mitsuo 
Published: December 2004

AbstractAs a series of studies on the mechanical properties of materials used in cardiac prostheses, static and dynamic characteristics and stability of five kinds of elastomeric polymers have been studied by uniaxial tensile and fatigue tests in air at room temperature and in saline solution at 37°C. Of all materials tested in this study, Texin MD85A, a segmented polyether polyurethane, has the lowest flexibility under static and dynamic conditions, with relatively high strength. Hexsyn, a polyolefin rubber, is highly flexible with little stress relaxation. However, this material has very low tensile strength and short elongation, and shows unstable change in the elastic modulus during cyclic deformation. Avcothane 51, a copolymer of polyurethane and silicon, has unstable mechanical properties and gradually stiffens upon cyclic deformation. On the other hand, Biomer, a segmented polyether polyurethane, has high flexibility and shows the most stable behavior during cyclic deformation regardless of test environment. Toyobo TM5, a similar segmented polyurethane to Biomer, has higher strength and ductility than Biomer, although its static and dynamic flexibility are slightly worse and less stable than those of Biomer. These results indicate that Biomer and Toyobo TM5 are more suitable for flexible components of cardiac prostheses.
The structure of bone apatite surfaces
Authors: Posner Aaron S. 
Published: December 2004

AbstractThis is a review of the surface chemistry of bone mineral and its synthetic counterpart hydroxypapatite. Small‐angle x‐ray scattering and low‐temperature nitrogen adsorption measurements show bone mineral surfaces range from 100 to 200 m2/g. The heats of adsorption of small molecules on bone and apatite surfaces show that these materials have polarizing surfaces which form strong bonds with polar and polarizable molecules. Water is hydrogen bonded to these surfaces with energies ranging from 23 Kcal/mol, for low coverage, to 11 Kcal/mol after two full layers; the latter value shows that after two monolayers the water is bonded as strongly to the solution as it is to the apatite surface. Stearic acid in cyclohexane adsorbs on bone and apatite surfaces in a closed‐packed manner with the straight‐chain molecules in parallel array with the end carboxyl groups hydrogen bonded to surface electronegative ions. Synthetic hydroxyapatite has long been used in chromatography because of the bonding capacity apatite surface has for certain proteins and polynucleotides. The metabolic interplay between bone mineral and the body results from the high magnitude and high reactivity of the mineral surface.
The interface of various glasses and glass ceramics with a bony implantation bed
Authors: Gross U. , Strunz V. 
Published: December 2004

AbstractBasing on histomorphological evaluations and morphometrical quantifications in a standardized model experiment, a comparison is made between the reactions of skeletal tissues to various glasses, glassceramics and enamels. On the surface of these so‐called reactive biomaterials either a direct bonding to mineralized bone or also different amounts of osteoid or chondroid tissue formation can be observed, depending on the composition of the material. It is shown that (1) the solubility of the glasses cannot directly be related to the reactivity and the resulting bone bonding; (2) bone binds only to glasses with a controlled release of constituents and which exhibit a seam of extracellular matrix on their surface, in which normal primary mineralization can occur; (3) the release of constituents such as Al2O3, Ta2O5, ZrO2, or phosphates from the material can inhibit this normal mineralization and the transformation of chondroid tissue to bone; (4) if connective tissue instead of bone is present at the interface (either primarily or after bone remodelling), the dissolution (or corrosion) of the material may be no longer controllable, and the tissue reacts with a continuous inflammatory response to the corrosion products.
Bioglass coatings and bioglass composites as implant materials
Authors: Ducheyne P. 
Published: December 2004

AbstractThis article addresses three aspects of the mechanical and biological properties of bioreactive glasses. First, it describes the composition and the relationship between the composition and bonding and its influence on the bone bonding mechanism and the rate of bond formation. Second, the mechanical properties of bioglass are dealt with. It is shown that the approaches to use bioglass in highly stressed applications, have met with various degrees of success. Third, the issue of the effect of loading on the glass properties and, above all, on the glass bonding properties is discussed.
In vivo corrosion of sodium silicate glasses
Authors: Pernot François , Zarzycki Jerzy , Baldet Pierre , Bonnel François , Rabischong Pierre 
Published: December 2004

AbstractSquare‐shaped implants of various sodium silicate glasses were weighed and implanted intraperitoneally in rats for periods ranging from 8 to about 60 days. The implants were then removed and their aspect was compared to their aspect before exposure to physiological environment. The corrosion products were studied by x‐ray diffraction and electron microprobe analysis. Weight changes were also measured to calculate a biodegradation rate. The glass 66 S O (66.6 SiO2–33.3 Na2O) was strongly corroded, as early as after the first week. The nonsoluble degradation products formed a cocoon encapsulating the now smaller specimen. The analysis of the cocoon showed that it was made of a silica‐rich layer containing also calcium and phosphorus. In this layer the ratio Ca/P could correspond to that of an apatite. The biodegradation rate reached 71 × 10−4 g · cm−2 · day−1. The glass 75 SO (75 SiO2‐25 Na2O) was not so quickly corroded: Cracks appeared at the surface and progressively reached the center of the implants. There was no removable shell but a white deposit, adherent to the surface. This deposit contained silica and also calcium and phosphorus at the periphery. The biodegradation rate was only 2.6 × 10−4 g · cm−2 · day−1.
Pyruvic acid as an etching agent in clinical dentistry
Authors: Retief D. H. , Harris B. E. , Bradley E. L. , Denys F. R. 
Published: December 2004

AbstractThe objective of this study was to evaluate the use of pyruvic acid as an alternative etching agent to phosphoric acid (H3PO4). Solutions containing 5, 10, 15, 20, 25, and 30 m/m % pyruvic acid and 50% m/m H3PO4 were prepared. The tensile bond strengths of a composite resin to enamel surfaces etched with the respective etching agents were determined. The rates of etching of enamel surfaces by each of the etching solutions were evaluated. Unground and polished enamel surfaces were etched with the respective etching solutions and the surfaces examined by scanning electron microscopy. The tensile bond strengths of the resin to enamel surfaces etched with 10–30% pyruvic acid exceeded those obtained on enamel surfaces etched with 50% H3PO4. The rates of etching of all the pyruvic acid solutions were significantly less than that of H3PO4. Well‐defined etching patterns were observed on the enamel surfaces etched with all the etching solutions. The results of this laboratory study suggest that pyruvic acid may be a suitable alternative to phosphoric acid as an etching agent in clinical dentistry.
Biodegradation of and tissue reaction to 50:50 poly(DL‐lactide‐co‐glycolide) microcapsules
Authors: Visscher G. E. , Robison R. L. , Maulding H. V. , Fong J. W. , Pearson J. E. , Argentieri G. J. 
Published: December 2004

AbstractThe biodegradation of the copolymer 50:50 poly(DL‐lactide‐CO‐glycolide)‐lypressin microcapsules was studied by light and electron microscopic methods and 14C release. Intramuscular injection sites of microcapsules in rats were studied by dissecting and conventional light microscopy as well as scanning (SEM) and transmission electron microscopy. A minimal localized acute myositis was seen initially at the injection sites. By Day 4, a few small foreign body giant cells were present participating in the minimal foreign body response. Later the inflammatory cells decreased and the individual microcapsules were walled off by immature fibrous connective tissue and large syncytial foreign body giant cells. By Day 35, definitive changes in some microcapsules, consisting of a granular and slightly eroded appearance of the internal matrix, were seen by SEM. By Day 42, the outer rims of the microcapsules were extensively eroded. At Day 56, the inflammatory and connective tissue reactions were almost completely resolved and biodegradation continued so that only remnant pieces of the microcapsules were present at Day 63. The morphologic picture correlated well with loss of 14C radioactivity, which could no longer be detected at the injection sites on Day 56. Phagocytosis did not seem to be an important factor in the biodegradation.
Metallographic texture analysis of dental materials by polarizing microscopy in the incidental light
Authors: Newesely H. , Rabe H. 
Published: December 2004

AbstractIncidental polarized light microscopy can be used for the optical analysis of crystal phases with similar anisotropic behavior or preferred textures in polished sections. In this method, the vibration mode of the reflected light is determined by remarkable interference colors in the microscope using a compensator plate. The application of this method for the analysis of dental materials is demonstrated with amalgams and gold‐reduced alloys. As a prerequisite, a modified procedure for preparing suitable polished sections of inhomogenous materials is described. Employing this optical and a crystallographic computing method, more detailed information about the way of element replacement in the course of the chemical reaction can be obtained. The results of these investigations also warrant the assumption that coherent crystal intergrowth which prefers low indicated and closely packed lattice directions, gives rise to a good adhesive strength of the bonding in the alloy.
The structure of highly crosslinked poly(2‐hydroxyethyl methacrylate) hydrogels
Authors: Peppas Nikolaos A. , Moynihan Humphrey J. , Lucht Lucy M. 
Published: December 2004

AbstractFilms were prepared by reaction of HEMA monomer with the crosslinking agent ethyleneglycol dimethacrylate (EGDMA) at crosslinking ratios, X, of 0.005, 0.01, 0.0128, 0.025, and 0.050 mol EGDMA/mol HEMA in the presence of 40 wt. % water at 60°C for 12 h. These membranes were subsequently swollen in water at 37°C and their structure analyzed using a modified Gaussian distribution equation of equilibrium swelling. The calculated values of Mc varied between 800 and 3700 daltons, which corresponded to a correlation length of the mesh size ζ of 16.2 to 35.6 Å. The structural analysis and diffusive studies of PHEMA membranes indicate that the recent determinations of Mc for PHEMA by Migliaresi et al. (C. Migliaresi, L. Nicodemo, L. Nicolais, and P. Passerini), “Physical characterization of PHEMA gels,” J. Biomed. Mater. Res., 15, 307 (1981) and others are not accurate. The methods presented can also be used for analysis of any highly crosslinked polymer network produced by simultaneous polymerization and crosslinking reactions.
The blood compatibility of chitosan and N‐acylchitosans
Authors: Hirano Shigehiro , Noishiki Yasuharu 
Published: December 2004

AbstractA segment of silk polyfilament suture [No. 2‐0(USP)], ca. 10 cm long, was coated with a thin membrane (2–6 μm) of chitosan, N‐acetylchitosan, or N‐hexanoylchitosan. The suture was directly inserted into the lumen of dog's peripheral veins. The in vivo blood compatibility of these membranes was macroscopically determined from the blood coagulum formed on the membrane surface at 2 h. An intense thick blood coagulum formed on the chitosan membrane surface and a thin blood coagulum formed on N‐acetylchitosan membrane surface, but no blood coagulum formed on N‐hexanoylchitosan membrane surface.
The intracellular degradation of poly(ε‐caprolactone)
Authors: Woodward S. C. , Brewer P. S. , Moatamed F. , Schindler A. , Pitt C. G. 
Published: December 2004

AbstractPoly(ε‐caprolactone) [PEC], a biodegradable aliphatic polyester, undergoes a two‐stage degradation process: The first lengthy phase involves nonenzymatic hydrolytic cleavage of ester groups, the second phase beginning when the polymer is more highly crystalline, and of low molecular weight. The cellular events of the second phase were examined by implanting gelatin capsules containing 25 mg of low molecular weight (Mn 3000) PEC powders, 106 to 500 μm, in rats. PEC fragments ultimately were degraded in phagosomes of macrophages and giant cells, the process requiring less than 13 days for completion at some sites. PEC was also identified within fibroblasts. These studies support the intracellular degradation of PEC as the principal pathway of degradation once the molecular weight of the aged polymer is reduced to 3000 or less.
Polymers for the controlled release of macromolecules: Effect of molecular weight of ethylene‐vinyl acetate copolymer
Authors: Hsu Terry Tsong‐Pin , Langer Robert 
Published: December 2004

AbstractMatrices composed of ethylene‐vinyl acetate copolymer (EVAc) have been used for controlled delivery of macromolecular bioactive agents. Three EVAc samples of different molecular weight (MW) were selected from solution fractionated samples. The polymer MW is a sensitive factor in affecting the release rate of bovine serum albumin (BSA); the higher the MW of EVAc, the slower the release rate. Depending on the degree of hydrophilicity of the device, the relatively hydrophilic drug particles would cause various degrees of swelling pressure upon water uptake. The relatively hydrophobic EVAc carrier would impose different degrees of restrictive force as determined by polymer MW. The interaction between the restrictive force of the carrier and the swelling pressure of the drug particles is a key factor in affecting the drug release kinetics. As a result, the selection of the polymer carrier can be used to affect the kinetics of a controlled release device.
Optical properties of esthetic restorative materials and natural dentition
Authors: Cook Wayne D. , McAree Deborah C. 
Published: December 2004

AbstractThe diffuse reflectance spectra of dental ceramic and composite resin specimens were analyzed by the Kubelka–Munk (K–M) theory of light scattering materials. This enabled the prediction of the spectra and color of differing thicknesses of these materials on various backgrounds, which were in good agreement with observation. The reflectance spectra of natural enamel and dentine sections were also measured on white and black backgrounds. This allowed the calculation of the K–M scattering (S) and absorption (K) parameters, which were compared with those of the restorative materials. The Chroma of these tooth sections increased slightly with the age of the patient, but the Hue and Value showed no systematic variation. Comparisons of the measured Munsell color for a range of composite resins and ceramics with that of the natural tooth sections showed that they generally exhibited a similar range of colors.
Biocompatibility test procedures for materials evaluation in vitro. II. Objective methods of toxicity assessment
Authors: Johnson H. J. , Northup S. J. , Seagraves P. A. , Atallah M. , Garvin P. J. , Lin L. , Darby T. D. 
Published: December 2004

AbstractMethods of assessing the biocompatibility of materials for use in medical devices were evaluated. Ten materials were tested using quantative, objectively graded in vitro biochemical and functional assays employing four cell lines (CCL 1, 74, 76, and 131) used in previous work and five primary cell types (human lymphocytes, polymorpho‐nuclear leukocytes, and mixed leukocytes, mouse macrophages, and mouse embryo). The biochemical methods (DNA synthesis, protein synthesis, and ATP activity) demonstrated good agreement in toxicity ranking of the materials, regardless of which cell culture was used and, also, the cell cultures responded similarly for each method. Methods that measured functional characteristics of cells (adhesion and phagocytosis) were highly sensitive but had low toxicity ranking agreement and reproducibility. Assays (defined as method and cell culture combinations) using cell lines were more reproducible than assays using primary cell types. Significant differences in sensitivity were noted among the assay systems for particular material types. The in vitro assays were more sensitive to differences in material composition than was a 90‐day assay by subcutaneous implantation in rats.
A segmented polyurethane composite prosthetic anterior cruciate ligament in vivo study
Authors: Peterson Christopher J. , Donachy James H. , Kalenak Alexander 
Published: December 2004

AbstractA segmented polyurethane prosthetic anterior cruciate ligament prototype has been developed and its in vivo integrity assessed in canine subjects. Prosthetic ligaments surgically implanted for 3, 4, 6, 8, 12, and 16 months were assessed clinically in living subjects, at time of autopsy, and microscopically postautopsy. It was found that the ligaments were adequate in strength to provide stability and last for periods up to 16 months. Notching of the ligaments was observed at two designated friction points.
Effect of drug–vinyl copolymer delivery composites on the rat prostate
Authors: Yoshida Masaru , Asano Masaharu , Kaetsu Isao , Yamanaka Hidetoshi , Nakai Katsuyuki , Yuasa Hisako , Shida Keizo 
Published: December 2004

AbstractA radiation polymerized drug–vinyl copolymer delivery composite (0.8 mm in diameter, 3 mm long) was inserted into the right‐lobe ventral prostate (I), into the right testis (II), and subcutaneously (III) into the back of male Wistar rats. The implantation was carried out over a period of 12 weeks maximum. From the relationship between the site of surgical insertion of the implant and the physiologic response (as measured by the decrease in the weight of the prostatic organs, e.g., ventral prostates, dorsolateral prostates, and seminal vesicles), it was found that in an AA560‐containing composite (36 μg daily), the physiologic response is increased in order of (III) > (II) > (I). The same tendency was observed in the Estracyt‐containing composite system (15 μg daily). The difference in the physiologic response owing to the site of surgical insertion of the implant was not observed in an E2‐17β‐containing composite (6 μg daily), although this composite showed the strongest physiologic response. No physiologic response in rats with CMA‐containing composite (28 μg daily) was noted.
A modification of the cell culture agar diffusion test using fluoresceindiacetate staining
Authors: Schmalz G. , Netuschil L. 
Published: December 2004

AbstractIn order to reduce the uncertainties involved in the morphologic evaluation of the cell culture agar diffusion test, the originally recommended neutral red stain was replaced by fluoresceindiacetate (FDA). This stain proved to be nontoxic in the concentrations used in this study (0.002%). Toxicity tests with phenol, formalin, and methylmethacrylate monomer revealed results corresponding to literature evaluations by other methods. Since FDA makes cell metabolism visible and easily accessible to automated evaluation techniques, it presents certain advantages over the morphologic evaluation using the neutral red stain.