bluuebunny/crossref_metadata_2025_split huggingface dataset:
Auger electron spectroscopic studies of stainless‐steel implants
Authors: Sundgren J.‐E. , Bodö P. , Lundström I. , Berggren A. , Hellem S. 
Published: December 2004

AbstractAuger electron spectroscopy together with scanning electron microscopy has been used to study the interface between stainlesssteel implants and human tissue. The thickness and nature of the oxide layer on the implants have been found to depend on the location of the implants in the body. Before implantation, the oxide layer is about 50 Å thick, consisting mainly of chromium oxide. For implants located in cortical bone the thickness of the interfacial oxide layer remains unaffected, while it increases by a factor of three to four on samples located in bone marrow. In both these cases calcium and phosphorus are incorporated in the oxides. Implants located in soft tissue have an interfacial oxide layer with a thickness of about one and one‐half times that on an unimplanted sample. On these samples, calcium and phosphorus are not found, but occasionally sulfur is found in the oxide layer. All these samples originated from the oral region of the body; the reason for this finding, however, is not known at present time. The interactions between the implants and human tissues resulting in the observed changes of the implant surfaces are discussed in terms of oxygen pressures and metabolic activity.
Mechanical properties and biomechanical compatibility of porous titanium for dental implants
Authors: Asaoka Kenzo , Kuwayama Norihiko , Okuno Osamu , Miura Ishi 
Published: December 2004

AbstractTitanium powder with a granule diameter of 420–500 μm was prepared and porous titanium specimens were made from this powder. The mechanical properties of these specimens were examined. The compressive strength and low cyclic compressive fatigue strength were 182 and 40 MPa, respectively. Fractography was also observed by scanning electron microscopy. Typical fatigue characteristics of the bonding areas of the powder were observed. In addition, porous‐titanium‐coated dental implants with pure titanium cores were prepared. The compressive strength of the material used was 230 MPa, fatigue strength not being improved. Biomechanical stress calculations using the finite element method were made using a model that employed the use of the material implanted in alveolar bone. Shear stress at the implant–bone interface as well as compressive stress concentrations in the bone was calculated. The most suitable elastic modulus for the dental implant was then estimated from these calculations. Finally, based on these results, the use of porous titanium for dental implants was assessed.
Divanillates and polymerizable vanillates as ingredients of dental cements
Authors: Stansbury J. W. , Brauer G. M. 
Published: December 2004

AbstractVanillate esters with multifunctional groups that react with metal oxides to give chainextended molecules have been synthesized. Divanillates were obtained from vanillic acid and the corresponding polymethylenediols. Methacryloylethyl vanillate (MEV) and vanillyl methacrylates were prepared respectively from hydroxyethyl vanillate or vanillyl alcohol and methacryloyl chloride. The properties of cements prepared with liquids incorporating these compounds were determined. Liquids containing divanillates dissolved in the reactive chelating agent o‐ethoxybenzoic acid (EBA) when mixed with zinc oxide powders harden within a few minutes. The resulting cements have a tensile strength much higher than the commonly used zinc oxide–eugenol cements, have low solubility, do not inhibit polymerization, and adhere well to metallic substrates. Similarly, liquids with MEV as an ingredient yield cements with excellent strength and good adhesion to stainless steel and composites. Their brittleness can be overcome by addition of an oligomeric methacryloylethyl vanillate to the liquid or silanized glass to the powder ingredient. These cements, subject to their biocompatibility to oral tissues, could be most useful for a number of dental applications.
Beryllium localization in base metal dental casting alloys
Authors: Covington J. S. , McBride M. A. , Slagle W. F. , Disney A. L. 
Published: December 2004

AbstractInvestigation of dissolution of base metal dental casting alloy constituents in aqueous solutions revealed an unexpectedly high level of beryllium as compared with the other constituents. Analysis of atomic emission spectroscopy is presented here showing the outer surface (0–100 Å) is decidedly enriched in beryllium as compared with the bulk composition of the alloy. This localization is consistent in all samples and forms of the alloy tested.
Leaching of tobramycin from PMMA bone cement beads
Authors: von Frauhofer J. A. , Polk H. C. , Seligson D. 
Published: December 2004

AbstractThe in vitro leaching characteristics of tobramycin from acrylic resin (PMMA) bone cement beads have been determined by a radioimmune assay. Tobramycin was incorporated at two concentrations into bone cement beads fabricated from three commercial brands of acrylic resin. Antibiotic leaching followed a curvilinear relationship of the form X · Y = A · X + B · Y. All beads showed similar tobramycin leaching rates over time but the initial amount of leached material differed with the amount of tobramycin incorporated in the bead and the source of the PMMA bone cement. The data indicate that tobramycin‐impregnated PMMA beads permit antibiotic leaching at a controlled rate compatible with possible clinical application.
Fibronectin binding properties of bacteriologic petri plates and tissue culture dishes
Authors: Bentley Kevin L. , Klebe Robert J. 
Published: December 2004

AbstractWith the aid of a monoclonal antibodybased ELISA assay, the fibronectin binding properties of poly(styrene) bacteriologic and tissue culture petri plates were studied. After treatment of the plastics with serum, both the rate of fibronectin binding and the maximum amount of fibronectin bound were found to be lower for bacteriologic than tissue culture plates. In contrast, when treated with purified fibronectin rather than serum, bacteriologic and tissue culture plates bound fibronectin equally well. Thus, serum proteins are more effective in inhibiting fibronectin binding to bacteriologic petri plates than to tissue culture dishes. The fibronectin binding properties of plastic substrata could be enhanced by oxidation with H2SO4 or diminished by dissolution and recasting of tissue culture dishes. Thus, the fibronectin binding properties of bacteriologic and tissue culture dishes can be interconverted. Plastics with enhanced fibronectin binding properties (tissue culture plates) were found to be hydrophilic and good substrates for cell attachment and growth while plastics with decreased fibronectin binding characteristics were found to be hydrophobic and poor substrates for cell attachment and growth. The cell‐adhesive properties of bacteriologic and tissue culture plastic substrata were found to vary during incubation with cells. While cells remained firmly attached and spread on tissue culture plastics over a period of 5 days or more, previously attached cells gradually detached from bacteriologic plastics at incubation times beyond 12 h. The gradual detachment of cells from bacteriologic plates probably explains the poor properties of bacteriologic plastics for the growth of anchorage‐dependent cells, in particular.
Antithrombogenicity and oxygen permeability of block and graft copolymers of polydimethylsiloxane and poly(α‐amino acid)
Authors: Kumaki T. , Sisido M. , Imanishi Y. 
Published: December 2004

AbstractA‐B‐A‐type block copolymers consisting of poly(α‐amino acid) as A component and polydimethylsiloxane as B component and graft copolymers consisting of polydimethylsiloxane as trunk polymer and poly(α‐amino acid) as branch polymer were synthesized. γ‐Benzyl‐L‐ or DL‐glutamate, ε‐benzyloxycarbonyl L‐lysine, and sarcosine were used as α‐amino acid. Different microphase‐separated structures were found on the film surface according to the copolymer composition and the casting conditions. In vitro antithrombogenicity test showed higher antithrombogenicity of block or graft copolymers than homopolymers. The best antithrombogenicity was independent of the kind of α‐amino acid and the degree of polymerization of copolymers. The best ratio was 65–75% in block copolymer and 40–50% in the case of graft copolymer. The oxygen permeability of block and graft copolymer film was intermediate between those of homopolymers and varied with changing the composition of the copolymer. These experiments showed that the microphase‐separated structure on the film surface was most important both for the antithrombogenicity and oxygen permeability of these copolymer films.
Development of a prosthetic venous valve
Authors: Hill R. , Schmidt S. , Evancho M. , Hunter T. , Hillegass D. , Sharp W. 
Published: December 2004

AbstractThe pathology of thrombophlebitis primarily results from the obliteration of venous valves in the lower extremities. The objective of this study was to develop a prosthetic venous valve that could be implanted in the human femoral system to ameliorate the deleterious effects of thrombophlebitis. Prosthetic venous valves were produced from two materials: Pellethane valves were fabricated from a dip‐casting process; umbilical vein valves were produced by a fixation process. The valves were evaluated as implants within the external jugular veins of 10 research dogs. Each animal was implanted with one Pellethane valve in one external jugular vein and one umbilical vein venous valve in the contralateral jugular vein. Each valve was positioned over a stainless‐steel cylinder that had been implanted into the jugular veins in such a manner that there existed no blood–cylinder interaction. Patency of the valves was determined by X‐ray venography at 24, 48, and 72 h and at 5 and 8 days postoperatively. All of the umbilical vein venous valves were occluded by the end of 48 h, whereas two of the Pellethane venous valves remained patent for at least 5 days but were occluded at 8 days. The results of this study suggest the possibility of success of Pellethane valve implants in the venous circulation and indicate future directions for study.
Surface energies and the bone induction principle
Authors: Eriksson Christopher 
Published: December 2004

AbstractThe macroscopic and histologic sequence of events in the induction of ectopic bone formation by porous demineralized bone and by synthetic porous sponges of poly‐hydroxyethylmethacrylate (poly‐HEMA) is described and reviewed. The observed relationship between the yield of new bone generated, and in vitro calcification, with the zeta potential, seems to parallel the connection between general adhesion in biologic systems and the critical surface tension. Consistent with experimental findings over the years, the bone induction principle (BIP) is probably associated with porous, mechanically suitable, hydrophilic materials with a high polar surface energy. It can be inferred that such surfaces are exposed when bone is suitably demineralized and treated, as has been reported. The discovery of noncollagenous proteins that are important to the BIP may be viewed in this light. Local heterogeneities on cellular surfaces are known to be important but are not detected by macroscopic techniques. It is suggested, following Lerchental, that induced stresses in the cell membranes cause a redistribution of surface charges that increases the local surface energy. This may lead therefore to an agglomeration and alignment of cells, as a response to the stress, accompanied by differentiation, as well.
Wetting characteristics and blood clotting on surfaces of copoly(γ‐Benzyl‐L‐glutamate, γ‐hydroxyethyl‐L‐glutamine)
Authors: Yano Ei , Komai Takashi , Kawasaki Tadayoshi , Kaifu Katsuaki , Atsuta Tomoyoshi , Kubo Yoshihiko , Fujiwara Yukihiko 
Published: December 2004

AbstractThe film surface of poly(γ‐benzyl‐L‐glutamate) (PBLG) was modified with 2‐aminoethanol to enhance its hydrophilicity. Controlling the reaction conditions of PBLG and 2‐aminoethanol, various types of copoly(γ‐benzyl‐L‐glutamate, γ‐hydroxyethyl‐L‐glutamine) film surfaces were obtained.Surface free energy (γsv), the dispersive component of γsv (γ), the nondispersive component of γsv (γ), and the interfacial free energy of polymer surface with water (γsw), which were obtained by using the contact angle measurement and calculation method proposed by Andrade et al., were changed remarkably by the aminolysis. The γsv value increased after 2 h of aminolysis from 48.2 (PBLG) to 65.3 dyn/cm and gradually increased to around 70 dyn/cm after 12 h reaction. (γ) and (γ) changed from 31.0 and 17.2 dyn/cm (PBLG) to 26.5 and 44.3 dyn/cm, respectively. These parameters of the material surfaces, modified over 12 h reaction, were found to be similar to those of the surfaces of canine aorta, vein, and human fibrin membrane. Blood clotting times on these polymer surfaces were comparatively longer than on siliconized glass surfaces.
Effect of palladium on sulfide tarnishing of noble metal alloys
Authors: Suoninen E. , Herø H. , Minni E. 
Published: December 2004

AbstractElectron spectroscopic studies of AuAgCu alloys of the type used for dental castings show that small additions (≤3 wt%) of palladium reduce essentially the thickness of the sulfide layer formed on surfaces of samples treated in aqueous Na2S solutions. Relative to silver, palladium does not enrich in the sulfide, but statistically significant enrichment is found immediately below the sulfide layer. This enrichment probably takes place during the exposure of the substrate surface to atmosphere before the sulfiding treatment. The mechanism of the impeding effect of palladium on sulfiding is assumed to be a decrease in diffusion from the bulk alloy to the surface due to the enriched layer. The effect cannot be explained by changes in the electronic structure of the alloy due to palladium alloying.
Bioerodible polyanhydrides as drug‐carrier matrices. I: Characterization, degradation, and release characteristics
Authors: Leong K. W. , Brott B. C. , Langer R. 
Published: December 2004

AbstractPolyanhydrides based on a variety of aromatic and aliphatic dicarboxylic acids were developed as bioerodible carrier matrices for controlled delivery applications. The high hydrolytic reactivity of the anhydride linkage provides an intrinsic advantage over other classes of bioerodible polymers in versatility and control of degradation rates. For example, using the poly[bis(p‐carboxyphenoxy) alkane anhydrides] as models, polymers with degradation rates in the range of 10−1 to 10−4 mg/h/cm2 were obtained by changing the alkane from a methyl to a hexyl group. The polymers were characterized by infrared (IR), differential scanning calorimetry, gel permeation chromatography, and scanning electron microscopy (SEM). Near zero‐order degradation kinetics were observed for the hydrophobic polyanhydrides over several months. The drug release profile of the model drug p‐nitroaniline followed closely that of the degradation of injection‐molded poly[bis(p‐carboxyphenoxy) propane anhydride] over a period of more than 8 months. Close correlation of polymer degradation and drug release was also observed in other injection‐molded samples (10% loading), suggesting a release mechanism that was dominantly degradation controlled. Degradation of these polyanhydrides was pH sensitive, being enhanced in high pH, and became more stable in acidic conditions.
Efficacy of an antibiotic coated indwelling catheter: A preliminary report
Authors: Sakamoto Izumi , Umemura Yoshihiro , Nakano Hiroshi , Nihira Hiromi , Kitano Taiji 
Published: December 2004

AbstractThis study was conducted to examine if an aminoglycoside (dibekacin sulfate, DKB) incorporated into a coating layer on outer and inner surface of indwelling catheters would be released into urine both in vitro and in clinical cases on a sustained basis and if the released DKB would have any efficacy on delaying lower urinary tract infections. Released amounts of DKB from the catheter silicone rubber (SR) catheter were periodically measured both in vitro and in clinical applications. During the clinical applications, the catheters were indwelled in 14 patients. Organism counts in the patients' urine were determined and organisms were isolated from bacteriuria (defined as ≧104 CFU/mL) and MICs to DKB were measured. Observations on several combined symptoms frequently associated with indwelling catherization were performed. Results showed that sustained release of DKB continued for more than 25 days and 13 days in vitro and in clinical cases, respectively. Clinical studies suggested that 8 days of sterile urine after catherization might be expected in patients without systemic administration of antibiotics and more than 2 weeks if combined with it. No particular problems in its use and associated symptoms were recognized.
Transmission of water through a biocompatible polyurethane: Application to circulatory assist devices
Authors: Reid J. Spence , Rosenberg Gerson , Pierce William S. 
Published: December 2004

AbstractThe permeability characteristics of a water‐segmented polyurethane (Biomer) system under the conditions encountered in circulatory‐assist devices were investigated. A diffusion cell and permeability system providing precise control of membrane boundary conditions and allowing continuous measurement of water vapor transmission was designed. Liquid water at 37°C was used as the donor fluid and the system incorporated a constant‐flow nitrogen carrier gas and an optical dew point sensor downstream to determine the water vapor mass flow rate as a function of time. The mass flow rate was then numerically integrated and plotted against time to allow calculation of effective diffusion coefficient (D) by the dynamic time lag method. Steady‐state permeabilities were found to be insensitive to donor chamber hydrostatic pressure (50–200 mm Hg) indicating that bulk flow is not a transport mechanism in these membranes. The permeability coefficient (P) was independent of membrane thickness (H) over the four samples tested (0.0102, 0.0148, 0.0269, and 0.0366 cm), with an average value of 3.29 × 10−4cm2/s. Thus, diffusion was Fickian with negligible boundary layers. A plot of lag time versus H2 was linear (R = 0.98) yielding a value for D of 2.18 × 10−7cm2/s. A water–Biomer partition coefficient was determined for each sample with an average value of 1525, indicating a moderately hydrophilic membrane with a water sorption of 6.3% at 37°C. Since water transport is by Fickian diffusion in the absence of bulk flow, liquid water cannot be expected to accumulate in circulatory‐assist devices unless a condensing surface is maintained within the system.
The preparation and physicochemical characterization of an injectable form of reconstituted, glutaraldehyde cross‐linked, bovine corium collagen
Authors: McPherson J. M. , Ledger P. W. , Sawamura S. , Conti A. , Wade S. , Reihanian H. , Wallace D. G. 
Published: December 2004

AbstractPepsin‐solubilized bovine corium collagen was purified, reconstituted, and treated with various levels of glutaraldehyde. Treatment of suspensions of fibrillar collagen with low concentrations of glutaraldehyde appeared to have little effect on the gross morphology of fibrils, as judged by electron microscopy, but did have a significant impact on their physicochemical stability. Fibrillar collagen treated with glutaraldehyde at a concentration equal to or greater than 0.0075% demonstrated significant decreases in neutral solubility at elevated temperatures as compared to noncross‐linked controls. Differential scanning calorimetry provided a convenient and quantitative means to correlate increases in melting temperature with increases in glutaraldehyde treatment concentration. Fibrillar collagen cross‐linked with glutaraldehyde concentrations as low as 0.0075% demonstrated a significantly greater resistance to proteolytic degradation than did noncross‐linked fibrillar collagen samples. The residual, extractable aldehyde content of such preparations was between 1 and 3 ppm. Rheological measurements on such cross‐linked suspensions demonstrated that they were non‐Newtonian, shear‐thinning fluids, and that they were two‐ to threefold more viscous than corresponding preparations of noncross‐linked collagen.
The effect of resin formulation on the degree of conversion and mechanical properties of dental restorative resins
Authors: Ferracane J. L. , Greener E. H. 
Published: December 2004

AbstractThe goal of this study was to determine the effects of resin formulation variables, such as diluent concentration, catalyst type and concentration and cure mode, on the degree of conversion of carbon double bonds and mechanical properties of dental restorative resins. Diametral tensile strength, compressive strength, hardness, flexural modulus and strength, and dynamic mechanical properties were tested, and the results were correlated to the degree of conversion results obtained by infrared analysis. The results showed a significant correlation between increased mechanical properties and higher degrees of conversion. Enhanced conversions were achieved by incorporating higher diluent and lower inhibitor concentrations into the resins. Ambient temperature properties were similarly enhanced by lower inhibitor concentrations, but were not enhanced by higher diluent concentration. Dynamic mechanical properties testing at oral and elevated temperatures elucidated possible differences in resin microstructure and network quality. The storage moduli decreased over the dental temperature range and was lower at all temperatures for resins with lower conversions. The glass transition temperature was also lower in resins with poorer conversions, suggesting that these resins may be more unstable at oral temperatures than more highly converted resins. Dynamic mechanical properties were most closely correlated to degree of conversion in these polymeric systems.
The effects of an enhanced inflammatory reaction on the surface properties of cast biomer
Authors: Marchant R. E. , Anderson J. M. , Castillo E. , Hiltner A. 
Published: December 2004

AbstractThe ability of a biomaterial to withstand the rigors of the harsh biologic environment is an important consideration when considering a material for long‐term biomedical applications. Using a cage implant system, the effects of an intense inflammatory reaction on cast Biomer have been investigated. The inflammatory response to cast Biomer was greatly increased by coimplanting Biomer films with a cytotoxic poly(vinyl chloride) (PVC) in rats for a period of 21 days. Cast Biomer films were characterized by weight, advancing contact angle with water in air, attenuated total reflectance infrared spectroscopy and scanning electron microscopy (SEM). The analyses were performed before any treatment, after autoclaving and sonication, and after 21 days implantation with the cytotoxic (PVC) in rats. The results of the study indicated that cast Biomer does not undergo significant chemical degradation when subjected to the effects of an intense inflammatory reaction for 21 days. Implantation does, however, lead to rearrangement that results in a more polar and hydrophilic surface, suggesting that the polymer adapts to the hydrophilic environment of the inflammatory exudate.
Acoustoelectric technique for assessing the mechanical state of the dental implant–bone interface
Authors: Kaneko T. , Nagai Y. , Ogino M. , Futami T. , Ichimura T. 
Published: December 2004

AbstractA simple technique is described for in vivo assessing the interfacial rigidity between a dental root implant and the bone surrounding it. The method is based on estimating the frequency (10 to 150 KHz) and amplitude of the vibration of the implant induced by a small pulsed force. Application of the force to the implant and detection of the vibrational signal from the implant are performed by lightly touching it with two fine needles connected with piezoelectric elements. A distinct signal difference observed in animal tests of bioactive implant and nonbioactive one is shown to well agree with that obtained from corresponding ex vivo models.