bluuebunny/crossref_metadata_2025_split huggingface dataset:
Dental implant materials. II. Preparative procedures and surface spectroscopic studies
Authors: Smith D. C. , Pilliar R. M. , Metson J. B. , McIntyre N. S. 
Published: December 2004

AbstractThe tissue response to an implant may involve both physical and chemical factors. There is little reliable information on the effects of these parameters and the associated ionic release on the cell‐material interaction because the majority of studies have not fully characterized the implant material. In this work surface spectroscopy using ISS, ESCA, and SIMS was carried out on Ti6A14V, Co‐Cr‐Mo, Al2O3, and hydroxyapatite dental implant materials that had been subjected to six commonly used preparative procedures. The results showed that each procedure generated an individualistic composition for the outermost surface of each material. These differences could be significant in cellular and tissue response. Improved understanding of these factors requires defined and reproducible surfaces.
Effect of hydrophilic soft segment side chains on the surface properties and blood compatibility of segmented poly (urethaneureas)
Authors: Takahara Atsushi , Okkema Ann Z. , Wabers Hugh , Cooper Stuart L. 
Published: December 2004

AbstractSegmented poly(urethaneureas) with hydrophilic side chains were prepared from poly(tetramethylene oxide) (PTMO), 4,4′‐diphenylmethane diisocyanate (MDI), ethylene diamine (ED) and a diol with a long hydrophilic side chain comprised of an ethylene oxide‐propylene oxide copolymer. The end groups of the hydrophilic chains were either sodium sulfonate or methoxy groups. The state of microphase separation showed a small dependece on the fraction of long‐chain hydrophilic diol. Surface analysis by means of static underwater contact angle and dynamic contact angle measurements revealed that the graft chains were at the aqueous interface in the hydrated state. An ex vivo A‐V shunt experiment revealed that a more thrombogenic blood‐material response was correlated with an increase in the concentration of polymeric hydrophilic side chain incorporation. The polyurethane containing a long chain diol with methoxy end groups exhibited a higher level of thrombogenicity than the similar polymers possessing a sulfonate terminated side chain.
Mast cells and tissue reaction to intraperitoneally implanted polymer capsules
Authors: Christenson L. , Wahlberg L. , Aebischer P. 
Published: December 2004

AbstractThe inflammatory reaction to implanted biomaterials often compromises the clinical usefulness of implantable devices. Dexamethasone, an anti‐inflammatory agent, acts on macrophages to decrease production of inflammatory mediators, and on mast cells to prevent degranulation. Systemic administration of dexamethasone (dms) in rats decreases the tissue reaction to intraperitoneally implanted vinyl chloride‐acrylic copolymer capsules. Local release of even smaller amounts of dms from a polymeric substrate placed inside an acrylic copolymer capsule may control the tissue reaction while avoiding the undesirable side effects of systemic treatment. Such a system also allows investigation of the local effect of soluble molecules on tissuematerial interactions without altering the surface properties of the implant or adding the effect of a releasing material. In the present study, we investigated the effect of dms released from ethylene vinyl acetate (EVAc) rods placed in acrylic copolymer capsules and implanted in the peritoneal cavity of rats. In vitro the release of dms from EVAc rods was quasilinear for 5 weeks. When implanted intraperitoneally into rats, polymer capsules containing EVAc/dms rods generated a tissue reaction that was significantly thinner and featured fewer fibroblast and collagen layers than that around capsules containing pure EVAc rods at all time points studied. The tissue reaction layer was also thinner than that previously described in rats treated systemically with dms. The trabeculae of implants with dms‐loaded EVAc rods contained significantly more intact mast cells is involved in the tissue reaction to intraperitoneal polymer implants.
The in vitro effects of metal cations on eukaryotic cell metabolism
Authors: Wataha J. C. , Hanks C. T. , Craig R. G. 
Published: December 2004

AbstractThe in vitro cytotoxicity of nine metal cations common in dental casting alloys was evaluated using Balb/c 3T3 fibroblasts and four toxicity parameters: total protein production, 3H‐leucine incorporation, 3H‐thymidine incorporation, and MTT‐formazan production. Concentrations causing 50% toxicity compared to controls (TC50's) and reversibility of these effects were determined. The range of potency of the metal cations was 2–3 orders of magnitude, with Cd2+ showing the greatest potency and In3+ showing the least. Potency did not correlate with atomic weight for these metals. For each metal cation, the TC50's of the various toxicity parameters were similar in most cases. However, several cations (Cu2+, Ga3+) showed greater potency with 3H‐thymidine incorporation. Reversibility of the toxic effects was observed for all cations; the effects generally became irreversible at concentrations in the range of the TC50 value for each cation. Several stimulatory effects were seen. Small but statistically significant stimulations were observed after 24 h of metal exposure for Ag1+, Au4+, Cu2+, Ga3+, and Ni2+. Residual stimulations 24 h after removal of the metal cations were observed for Au4+, Cd2+, Ni2+, and Zn2+. Stimulations always occurred at concentrations below the TC50 concentrations. This study should be useful in evaluating the potential cytotoxic effects of metal cations released from dental alloys.
Synthesis and characterization of aliphatic polyurethane fiber: A potential suture material
Authors: Ray Alok R. , Bhowmick Ashis 
Published: December 2004

AbstractPolyurethane fibers were synthesized and characterized by IR, 1H NMR, DSC, and GPC. Their properties as fiber were compared with commercially available sutures of polypropylene, polyamide, polyester, and silk.
Coating of commercially available materials with a new heparinizable material
Authors: Barbucci Rolando , Albanese Antonietta , Magnani Agnese , Tempesti Federica 
Published: December 2004

AbstractDifferent commercial materials, such as polyurethane (PU), plasticized PVC (PVC), glass, Gore‐tex, and Dacron, were coated with a well‐characterized biomaterial (PUPA) based on polyurethane and poly(amido‐amine) components. Two different classes of coating were obtained due to the different characteristics of the substrates. In the case of PVC and polyurethane which are soluble in the solvent of the PUPA‐coating solution, there was penetration and blending of the coating and underlying materials. In the case of glass, Gore‐tex, and Dacron, which are insoluble in the solvent of the coating solution, only a superficial layer of PUPA could be obtained. The coating stability was investigated and the interaction between coating and underlying material studied by FT‐IR. All the stable coatings showed the ability to bind as much heparin as PUPA material by itself.
Bone bonding mechanism of β‐tricalcium phosphate
Authors: Kotani S. , Fujita Y. , Kitsugi T. , Nakamura T. , Yamamuro T. , Ohtsuki C. , Kokubo T. 
Published: December 2004

AbstractIt has been proposed that the formation of a surface apatite layer in vivo on surface active ceramics is an essential condition for chemical bonding between ceramics and bone tissue. To clarify the difference in bone‐bonding mechanisms between surface active ceramics and bioresorbable ceramics, two experiments were performed using plates of dense β‐tricalcium phosphate (β‐TCP). First, plates of β‐TCP were implanted subcutaneously in rats for 8 weeks. Surface change due to bioresorption was observed with scanning electron microscopy. Formation of the apatite layer on the surface was investigated using thin‐film x‐ray diffraction and Fourier transform infrared reflection spectroscopy. Second, plates of β‐TCP were implanted in tibiae of rabbits for 8 and 25 weeks and subjected to the detaching test to measure bone‐bonding strength. β‐TCP bonded strongly to bone. Undecalcified sections of the interface of bone and β‐TCP were examined with SEM‐EPMA. However, by physicochemical methods, no formation of surface apatite layer was observed. These results suggest that β‐TCP bonds to bone through microanchoring between bone and rough surface of resorbed β‐TCP.
Apatite formation on the surface of ceravital‐type glass‐ceramic in the body
Authors: Ohtsuki C. , Kushitani H. , Kokubo T. , Kotani S. , Yamamuro T. 
Published: December 2004

AbstractPrevious studies on surface structural changes in vitro as well as in vivo of bioactive A‐W‐type glass‐ceramics and Bioglass‐type glasses showed that the essential condition for glasses and glassceramics to bond to living bone is formation of a bonelike apatite layer on their surfaces in the body. Gross et al., however, had explained the bone‐bonding mechanism of Ceravital‐type apatitecontaining glass‐ceramic without mentioning formation of the surface apatite layer. In the present study, apatite formation on the surface of one of Ceravitaltype glass‐ceramics was investigated in vitro as well as in vivo. An apatitecontaining glass‐ceramic of the composition Na2O 5, CaO 33, SiO2 46, Ca(PO3)2 16 wt%, which was named KGS by Gross et al., was soaked in an acellular simulated body fluid which had ion concentrations almost equal to those of the human blood plasma. The same kind of glassceramic was implanted into a rabbit tibia. Thin‐film x‐ray diffraction, Fourier transform infrared reflection spectroscopy, and scanning electron microscopic observation of the surfaces of the specimens soaked in the simulated body fluid showed that Ceravital‐type glass‐ceramic also forms a layer of carbonate‐containing hydroxyapatite of small crystallites and/or a defective structure on its surface in the fluid. Electron probe x‐ray microanalysis of the interface between the glassceramic and the surrounding bone showed that a thin layer rich in Ca and P is present at the interface. These findings indicated that Ceravital‐type glassceramics also form the bonelike apatite layer on its surface in the body and bond to living bone through the apatite layer.
Protein adsorption from human plasma is reduced on phospholipid polymers
Authors: Ishihara Kazuhiko , Ziats Nicholas P. , Tierney Brian P. , Nakabayashi Nobuo , Anderson James M. 
Published: December 2004

AbstractProtein adsorption from human plasma was investigated on phospholipid polymers, poly (2‐methacryloyloxyethyl phos‐phorylcholine (MPC)‐co‐n‐butyl methacrylate (BMA)) or glass by radioim‐munoassay and immunogold labeling techniques. In the present studies the focus was to determine the composition and distribution of proteins at the surface of these materials after contact with human blood plasma. On all materials, protein adsorption was detected and included identification of albumin, IgG, fibrinogen, fibronectin, Hageman factor (factor XII), factor VIII/von Willebrand factor, high‐molecular‐weight kininogen (HMWK) and the complement protein C5. The amount of protein adsorbed decreased with an increase in MPC composition and appeared to adsorb to the surfaces in a uniform and evenly distributed manner. Therefore, we suggest that MPC moieties play an important role in suppression of protein adsorption. From these findings, it is concluded that the reduction of protein adsorption at the blood contacting surface of phospholipid polymers may result in the inhibition of thrombus formation.
Effect of hand mixing tobramycin on the fatigue strength of Simplex P
Authors: Davies Jeffrey P. , Harris William H. 
Published: December 2004

AbstractIn a recent study, we showed that the presence of gentamicin in Palacos R or erythromycin plus colistin in Simplex P bone cement did not significantly decrease the fatigue strength of the cement. [J. P. Davies, D. O. O'Connor, D. W. Burke, and W. H. Harris, “Influence of antibiotic impregnation on the fatigue life of Simplex P and Palacos R acrylic bone cements, with and without centrifugation,” J. Biomed. Mater. Res., 23, 379–397 (1989)] However, the commercially prepared Palacos R with Gentamicin and A K Z (Simplex P with colistin and erythromycin) which were tested are not approved by the FDA for use in the United States. Because of this, many surgeons in the United States hand mix tobramycin with the cement in the operating room if a case calls for the use of antibioticimpregnated cement. In this study, we determined the effect of adding 1.2 g of tobramycin to one pack (40 g) of Simplex P powder on the fatigue strength of the cement. The effect of centrifugation on the fatigue strength of Simplex P with the tobramycin added was also assessed. Simplex P was prepared according to the manufacturer's instructions with and without the addition of 1.2 g tobramycin per 40‐g pack and with and without centrifugation. Fifteen specimens of each of the four cement preparations were tested in fully reversed tension‐compression fatigue at ± 15 MP a, 2 H z. The fatigue strength of the uncentrifuged and centrifuged Simplex P was not significantly reduced by the tobramycin. Centrifugation significantly increased the fatigue life of Simplex P both with and without the addition of tobramycin. The fatigue life of the Simplex P with tobramycin was increased by a factor of 8 by centrifugation.
Physical characteristics of Ti‐6Al‐4V implants fabricated by electrodischarge compaction
Authors: Okazaki K. , Lee W. H. , Kim D. K. , Kopczyk R. A. 
Published: December 2004

AbstractPhysical characteristics of a Ti‐6Al‐4V implant were evaluated following fabrication using a new electrodischarge compaction technique. Ti‐6Al‐4V atomized powders were loaded into Pyrex tubes (3.3 mm ID) and subjected to a highvoltage, high‐current‐density pulse in air for a period of less than 300 μs. Single pulses (1.0, 1.5, 2.0 and 2.5 KJ/grampowder) were applied from a capacitor bank (240, 480 or 720 μF) to produce solid core implants with porous surface layers. Implants were evaluated microscopically for core size, neck size, pore size, grain structure, and incorporated oxide film. Hardness was also evaluated. Implants were compared with Ti‐6Al‐4V commercial powders. Core size increased and pore size decreased with increases in energy and capacitance. The cores were composed of equiaxed grains which were free of oxide at the grain boundary. Porous layers, consisting of particles connected in three dimensions by necks, were free of oxide films at the connecting interfaces. Neck size increased with increases in input energy and capacitance. Hardness readings of the core, necks, and porous particles resulted in readings higher than or similar to control materials. Electrodischarge compaction did not alter the physical characteristics during compaction.
In vivo biocompatibility of an aliphatic crosslinked polyurethane in rabbit
Authors: Jayabalan M. , Shunmuga Kumar N. , Rathinam K. , Kumari T. V. 
Published: December 2004

AbstractA cage implantation technique has been adopted in a rabbit animal model to investigate the biocompatibility of an aliphatic crosslinked polyurethane based on hexamethylene diisocyanate (HDI). In this study, four cages are represented; the cage containing the candidate polyurethane material, biomedical grade polyurethane (Tecoflex), the commercial grade polyvinylchloride (PVC), and an empty cage which were implanted subcutaneously in rabbits. Exudates were aspirated from these cages at 4, 7, 14, and 21 days postimplantation. Exudates were analyzed for variations in proteins, cell counts, and extracellular enzymes. Results with the four types of cage implants showed that the candidate polyurethane caused an inflammatory response comparable to that caused by medical‐grade Tecoflex and the empty cage control.
Release of metal ions from dental implant materials in vivo: Determination of Al, Co, Cr, Mo, Ni, V, and Ti in organ tissue
Authors: Lugowski Stan J. , Smith Dennis C. , McHugh Alana D. , Van Loon Jon C. 
Published: December 2004

AbstractLittle is known of the release of trace elements in vivo from dental implant materials. Conflicting data have been reported in the literature as to the levels of trace elements released and their potential consequences, mainly because of sampling and analytical methodological errors. In this study methods for average concentration levels of Al, Cr, Co, Mo, Ni, Ti, and V in organs were developed using rabbit tissue from an in vivo implantation study. At least 50% of the brain, liver, lung, kidney, and spleen were taken minimizing contamination. The tissue was homogenized by cryogenic milling at LN2 temperature and then freeze‐dried. Samples were digested in nitric acid and hydrogen peroxide using microwave energy. Standard reference materials were utilized for quality control. One liver sample was analyzed 10 times to assess the method precision. Absorbance values in blanks, standards, and test samples were measured using a Varian GTA 95 graphite furnace and 875 spectrophotometer. Very satisfactory method precision and quality control were recorded. Low or very low levels of the trace elements were found in the various organs.
Synthesis and cell attachment activity of bioactive oligopeptides: RGD, RGDS, RGDV, and RGDT
Authors: Hirano Yoshiaki , Kando Yoshihiro , Hayashi Toshio , Goto Kunio , Nakajima Akio 
Published: December 2004

AbstractTetrapeptides, Arg‐Gly‐Asp‐Ser (RGDS), Arg‐Gly‐Asp‐Val (RGDV), and Arg‐Gly‐Asp‐Thr (RGDT), present in the cell‐attachment domain of fibronectin, vitronectin, and collagen, respectively, were synthesized by using an improved liquid‐phase procedure. Bioactivities of RGD and RGDX (X = S, V, and T) as cell recognition determinants were investigated by two methods to evaluate interactions of these oligopeptides with L‐929 fibroblast cells originating in mouse epithelia. In the first method, these oligopeptides were immobilized to ethylene‐acrylic acid copolymer (EAA) film, and the cell‐attachment activity of the immobilized film was measured. In the second method, interaction of oligopeptides with the cells was evaluated by measuring the cell inhibition caused by oligopeptides. It was found that RGD and RGDX exhibit remarkable cellattachment activity, and the activity of oligopeptides depends on X.
Development of a new percutaneous access device for implantation in soft tissues
Authors: Jansen J. A. , van der Waerden J. P. C. M. , de Groot K. 
Published: December 2004

AbstractThe objective of this study was to evaluate a new type of percutaneous device (PD) designed to be implanted in soft tissues. The new PD consisted out of: (1) a flange‐shaped subcutaneous component, made from sintered titanium fiber‐web, and (2) a percutaneous component, made from dense sintered hydroxyapatite. The PDs were inserted in the back of 15 rabbits. The surgical procedure was performed in two steps. In the first session the subcutaneous component was placed. In the second session, after 3–4 months the percutaneous component was fixed in the subcutaneous component. The implants were left in situ for 1 and 4 months after the second implantation session. Clinical and histological investigations were performed. It is found, that there was only a limited epidermal downgrowth in the percutaneous area. No inflammatory reaction was observed in the dermal connective tissue. Histological analysis also demonstrated that titanium fiber mesh evokes minor adverse effects of the surrounding tissues. In conclusion, these experiments have shown that stabilization of the PD in the hypodermal area by using a sintered titanium fiber‐web structure favors the longevity of PDs implanted in soft tissues.
Protein adsorption to poly(ethylene oxide) surfaces
Authors: Gombotz Wayne R. , Guanghui Wang , Horbett Thomas A. , Hoffman Allan S. 
Published: December 2004

AbstractSurfaces containing poly(ethylene oxide) (PEO) are interesting biomaterials because they exhibit low degrees of protein adsorption and cell adhesion. In this study different molecular weight PEO molecules were covalently attached to poly(ethylene terephthalate) (PET) films using cyanuric chloride chemistry. Prior to the PEO immobilization, amino groups were introduced onto the PET films by exposing them to an allylamine plasma glow discharge. The amino groups on the PET film were next activated with cyanuric chloride and then reacted with bis‐ amino PEO. The samples were characterized by scanning electron microscopy, water contact angle measurements, gravimetric analysis, and electron spectroscopy for chemical analysis (ESCA). The adsorption of 125I‐labeled baboon fibrinogen and bovine serum albumin was studied from buffer solutions. Gravimetric analysis indicated that the films grafted with the low‐molecularweight PEO contained many more PEO molecules than the surfaces grafted with higher‐molecular‐weight PEO. The highmolecular‐weight PEO surfaces, however, exhibited greater wettability (lower water contact angles) and less protein adsorption than the low‐molecular‐weight PEO surfaces. Adsorption of albumin and fibrinogen to the PEO surfaces decreased with increasing PEO molecular weight up to 3500. A further increase in molecular weight resulted in only slight decreases in protein adsorption. Protein adsorption studies as a function of buffer ionic strength suggest that there may be an ionic interaction between the protein and the allylamine surface. The trends in protein adsorption together with the water contact angle results and the gravimetric analysis suggest that a kind of “cooperative” water structuring around the larger PEO molecules may create an “excluded volume” of the hydrated polymer coils. This may be an important factor contributing to the observed low protein adsorption behavior.
Tensile strength of the interface between hydroxyapatite and bone
Authors: Hong Lin , Hengchang Xu , de Groot K. 
Published: December 2004

AbstractTensile strength of the interface between hydroxyapatite (HA) and bone was tested. Scanning electron microscopy was used to observe the tensile failure mode and the morphological change of hydroxyapatite ceramic surface in bone. The porosity of hydroxyapatite is 14% and pore size less than 2 μm. After 2 weeks of implantation, the tensile strength of the interface is 0.72 MPa. After 4, 8, and 16 weeks, the average tensile strength stayed at 1.5 MPa. SEM showed that tensile failure occurred at the HA–bone interface at the second week, but after 4 weeks, the failure occurred between HA particles within the bulk, and not at the HA–bone interface. Calcified tissue was directly deposited on the HA ceramic surface and exits also in the micropores. Near the interface, sintered necks among HA ceramic particles were subjected to biodegradation.