bluuebunny/crossref_metadata_2025 huggingface dataset:
Macrophage activation induced by different carbon fiber‐epoxy resin composites
Authors: Peluso G. , Ambrosio L. , Cinquegrani M. , Nicolais L. , Tajana G.
Published: December 2004

The activation of cells by interaction with solid surfaces is important in many settings, including the response of tissue to implanted materials. However, few comprehensive studies of both cell migration and activation have been performed so that the connection between these events and immunological activation against foreign material is not well understood. In the present study, synthesis and expression of Ia antigens by peritoneal exudate macrophages after implantation of different carbon fiber composites in the rat peritoneal cavity have been investigated in order to determine whether the type of material implanted affected the composition of Ia‐bearing cells of the exudate. The results have confirmed the low level of expression of Ia on resident peritoneal macrophages; while we have found that macrophages, harvested after implantation, express a different amount of Ia related to the different cure cycles of the composite materials used.
Effect of some additives on the biostability of a poly(etherurethane) elastomer
Authors: Wu Y. , Zhao Q. , Anderson J. M. , Hiltner A. , Lodoen G. A. , Payet C. R.
Published: December 2004

Four materials based on a single poly(etherurethane) (PEU) prepared from MDI and PTMEG but differing in additives were studied in the cage implant systm. The two additives studied were Santowhite powder at the 1% level and Methacrol 2138F 5%. Methacrol 2138F appeared to be immiscible with the base PEU and was dispersed in discrete domains about 0.5‐μm in size. The retrieved PEU specimens were also cleaned and examined in the optical and scanning electron microscopes, and the size and density of adherent foreign body giant cells (FBGCs) were measured at implantation times up to 10 weeks. Methacrol 2138F had no effect on the density, coverage or size distribution of adherent FBGCs, but leaching of Methacrol 2138F was considered to be responsible for extensive pitting of the PEU surface. On the other hand, Santowhite powder appeared to inhibit formation of FBGCs, and while surface cracking and flaking were observed as early as 3 weeks postimplantation on some PEUs, the Santowhite powder effectively inhibited surface cracking and flaking up to the longest implantation time studied.
Polymorphonuclear leukocyte degranulation with exposure to polymethylmethacrylate nanoparticles
Authors: Papatheofanis Frank J. , Barmada Riad
Published: December 2004

Polymethylmethacrylate (PMMA) is clinically employed in a wide range of orthopaedic procedures. The etiology of the inflammatory reaction of recipient tissues to PMMA remains unresolved. Classically, polymorphonuclear leukocytes (PMNs) release cytoplasmic lysosomal granules when exposed to a variety of proinflammatory stimuli. Such degranulation contributes, and partially defines, the local tissue reaction to this foreign material. In the present investigation, PMMA particles (50–60 nm) were mixed with human PMNs, and the amount of lactate dehydrogenase, lysozyme, and β‐glucuronidase released from the cells was quantitated. In all cases, a dosedependent increase in degranulation followed the addition of increasing amounts of PMMA to the PMNs. In addition, the migration of PMNs was diminished in a dose‐dependent manner with exposure to increasing amounts of the cement. These results suggested that PMMA stimulates the release of leukocyte lysosomal contents and alters the migration characteristics of these cells in a manner that is consistent with the local inflammatory reaction to this cement.
Low wear rate of UHMWPE against zirconia ceramic (Y‐PSZ) in comparison to alumina ceramic and SUS 316L alloy
Authors: Kumar Praveen , Oka Masanori , Ikeuchi Ken , Shimizu Koichiro , Yamamuro Takao , Okumura Hideo , Kotoura Yoshihiko
Published: December 2004

Partially stabilized zirconia ceramic is being recognized among ceramics for its high strength and toughness. With this ceramic, is possible to manufacture a 22‐mm‐size femoral head for low friction arthroplasty of the hip joint in association with an ultra‐high‐molecular‐weight polyethylene socket. Wear‐resistant properties of zirconia ceramic were screened on two principally different wear devices. Sterile calf bovine serum, physiological saline, and distilled water were chosen as the lubricant fluid media. Depending on the lubricant medium, the wear factor of polyethylene against zirconia ceramic counterfaces was 40 to 60% less than that against alumina ceramic counterfaces, and 5 to 10 times lower than with the SUS316L metal counterfaces. Polyethylene wear against metal was more susceptible in saline in which it had 2 to 3 times higher wear rate than with serum. On the other hand, different fluid media had little effect on polyethylene wear against ceramic counterfaces. In each set of tests, the wear factor obtained on an unidirectional wear device showed 10 to 15 times higher values, in comparison to the wear factor estimated on a reciprocating wear device.
An in vivo model to study the pathobiology of infectious biofilms on biomaterial surfaces
Authors: Buret A. , Ward K. H. , Olson M. E. , Costerton J. W.
Published: December 2004

This study examines the morphology, ultrastructure, and microbiology of the intact biofilm developing on an implant surface. Silastic subdermal implant material was colonized with P. aeruginosa and surgically inserted into the peritoneal cavity of adult rabbits. After 4, 8, 28, and 42 days implants were recovered and the intact biofilms examined. P. aeruginosa colonized the implant throughout the entire experimental time. Microcolonies of glycocalyx‐coated bacteria were observed within the biofilm. However, the bulk of the biofilm was host‐generated and typically contained phagocytes trapped within a thick mesh of fibrin. Polymorphonuclear neutrophils were the predominant cell type. Isolated erythrocytes, macrophages, and fibroblasts were also observed. By day 28, the biofilm was enclosed in a fibrous capsule of vascularized connective tissue. The low numbers of neutrophils seen in biofilms from sterile Silastic sheets implanted into control animals suggested that neutrophilia may represent a specific cellular response to the bacterial colonization. The results indicate that the cell‐mediated immune response provides for most of the biofilm mass on colonized implant surfaces. Inactivated phagocytes trapped in fibrin may “wall‐off” the embedded bacterial micro‐colonies and thus shield them from live phagocytic leucocytes. Such a mechanism may play an important role in the pathogenesis of prosthetic device infections.
Platelet consumption by polyvinyl alcohol coated tubing in canines
Authors: Ip W. F. , Sefton M. V.
Published: December 2004

Polyvinyl alcohol (PVA)‐coated polyethylene tubing, with or without immobilized heparin, caused severe thrombocytopenia and enhanced the production of new platelets when inserted in a chronic arteriovenous shunt in canines. A similar length of uncoated polyethylene tubing neither lead to thrombocytopenia nor significantly enhanced platelet regeneration, relative to the shunt only without a test section. Platelet regeneration was monitored by the malondialdehyde assay, which was assumed to make a distinction between “new” and “old” platelets. This distinction was combined with the platelet count values to enable calculation of the cumulative consumption curve and the initial fractional consumption rate in the presence of a non constant platelet count. The resulting initial fractional consumption rates were: 34%/day for PVA, 20.5%/day for polyethylene, and 18%/day for the shunt only blank.
Influence of surface characteristics on bone integration of titanium implants. A histomorphometric study in miniature pigs
Authors: Buser D. , Schenk R. K. , Steinemann S. , Fiorellini J. P. , Fox C. H. , Stich H.
Published: December 2004

The purpose of the present study was to evaluate the influence of different surface characteristics on bone integration of titanium implants. Hollow‐cylinder implants with six different surfaces were placed in the metaphyses of the tibia and femur in six miniature pigs. After 3 and 6 weeks, the implants with surrounding bone were removed and analyzed in undecalcified transverse sections. The histologic examination revealed direct bone‐implant contact for all implants. However, the morphometric analyses demonstrated significant differences in the percentage of bone‐implant contact, when measured in cancellous bone. Electropolished as well as the sandblasted and acid pickled (medium grit; HF/HNO3) implant surfaces had the lowest percentage of bone contact with mean values ranging between 20 and 25%. Sandblasted implants with a large grit and titanium plasmasprayed implants demonstrated 30–40% mean bone contact. The highest extent of bone‐implant interface was observed in sandblasted and acid attacked surfaces (large grit; HCl/H2SO4) with mean values of 50–60%, and hydroxylapatite (HA)‐coated implants with 60–70%. However, the HA coating consistently revealed signs of resorption. It can be concluded that the extent of bone‐implant interface is positively correlated with an increasing roughness of the implant surface.
Prevention of bacterial colonization on polyurethane in vitro by incorporated antibacterial agent
Authors: Golomb Gershon , Shpigelman Arie
Published: December 2004

The presence of implanted biomaterials increases host susceptibility to infections. Once established, biomaterial‐mediated infections are resistant to treatment and persist until the device is removed. The objective of this work was to study the prevention of bacterial‐biofilm formation on polymeric implant (polyurethane) by controlled release of incorporated antibacterial agents (parabens). By embedding parabens in PU by the solvent‐cast method, matrices with amorphous dispersions (or solid solutions) were obtained. Release rate modulation was achieved by using different MW parabens and by a rate‐limiting membrane. Preliminary in vitro antibacterial studies of both methyl and propyl paraben matrices exhibited significant inhibition of Staphylococcus epidermidis biofilm formation. Propyl paraben matrices (15 and 20% w/w drug load) decreased the number of colony‐forming units on PU surface to 2 × 104/mL, in comparison to 6 × 105 on control polymers. This significant reduction was obtained without any effect on the number of viable bacteria in the suspension culture. This type of delivery system provides regional prophylactiv activity by creating a high local concentration of antibacterial agent.
Calcium phosphate formation at the surface of bioactive glass in vitro
Authors: Andersson Ö. H. , Kangasniemi I.
Published: December 2004

The calcium phosphate formation at the surface of bioactive glass was studied in vitro. Glass rods and grains were immersed in different aqueous solutions and studied by means of scanning electron microscopy and energy dispersive x‐ray analysis. Surface morphological changes and weight loss of corroded grains were monitored. In‐depth compositional profiles were determined for rods immersed in the different solutions. The solutions used were tris‐buffer (trishydroxy‐methylaminomethane + HCl), tris‐buffer prepared using citric acid (trishydroxy‐methylaminomethane + C6H8O7·H2O), and a simulated body fluid, SBF, containing inorganic ions close in concentration to those in human blood plasma. It was found that the calcium phosphate formation at the surface of bioactive glass in vitro proceeds in two stages. When immersing the glass in tris or in SBF a Ca,P‐rich surface layer forms. This accumulation takes place within the silica structure. Later, apatite crystals forming spherulites appear on the surface. The Ca/P‐ratio of initially formed calcium phosphate was found to be about unity. It is proposed that this is due to bonding of phosphate to a silica gel. The surface is stabilized, i.e., leaching is retarded, by the rapid Ca,P‐accumulation within the silica structure before apatite crystals are observed on the surface. It is proposed that the initially formed calcium phosphate is amorphous and that the crystallization is initiated within the silica gel. The crystallizing surface provides nucleation sites for extensive apatite formation on the glass surface. In the presence of citrate no Ca,P‐accumulation occur at the glass surface, but soluble Ca‐citrate complexes form. By comparing the weight loss during corrosion in tris with that in the calcium and phosphate containing SBF, it is possible to establish whether the glass can induce apatite formation at its surface or not.
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

The 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

Segmented 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

The 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

The 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

Polyurethane 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

Different 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

It 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

Previous 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

Protein 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

In 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

Physical 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

A 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

Little 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

Tetrapeptides, 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

The 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

Surfaces 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

Tensile 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.
Kinetics supramolecular structure and equilibrium properties of fibrinogen adsorption at liquid–solid interfaces
Authors: Nygren Hȧkan , Stenberg Manne , Karlsson Christin
Published: December 2004

Adsorption of fibrinogen onto hydrophobic and hydrophilic quartz surfaces was studied by ellipsometry and transmission electron microscopy (TEM) of negatively stained proteins. The initial adsorption at the hydrophobic surface, measured by ellipsometry, can be described by an apparent forward rate constant kl of 2 × 104 M−1 s−1. This constant was time‐dependent and is therefore considered as a rate coefficient. The apparent forward rate coefficient of adsorption to a hydrophilic surface was both time‐dependent and concentration‐dependent, indicating a history‐dependent process of adsorption. Plateau levels of adsorption were concentration‐dependent and lower at the hydrophilic quartzsur face (1.2 pmol/cm2) than at the hydrophobic surface (1.8 pmol/cm2). These surface concentrations correspond to rather tight‐packed monolayers of molecules adsorbed end‐on. The initial desorption can be described by a first order rate constant (k−1≈10−4s−1), down to 80‐90% of the initial surface concentration. The dissociation rate then decreased (k−1 ≈10−6 s−1) resulting in an apparently stable level of adsorbed protein. Slow changes of the binding strength of adsorbed proteins was seen during 24–72 h adsorption time. Deviations from an ideal equilibrium isotherm were seen both in the time dependence and as concavities in a Scatchard plot, suggesting intermolecular cooperativity. At low bulk concentrations a heterogeneous distribution of fibrinogen molecules was found at the surface below monolayer coverage. The supramolecular structure was characterized by the formation of end‐to‐end dimers and trimers laying down at the surface. At higher surface concentration adsorbed molecules showed polycrystalline structure with repeated nearest neighbordistances at 16 nm. The distribution of adsorbed fibrinogen molecules indicates that surface‐adsorbed fibrinogen may form a two‐phase system, containing significant amounts of water. The atypical kinetics and concentration dependence of fibrinogen adsorption may thus be due to properties of a two‐dimensional phase separation from a three‐dimensional liquid bulk.
Enhanced ingrowth of porous‐coated CoCr implants plasma‐sprayed with tricalcium phosphate
Authors: Chae John C. , Collier John P. , Mayor Michael B. , Surprenant Victor A. , Dauphinais Leo A.
Published: December 2004

Tricalcium phosphate (TCP) is an osteoconductive bioceramic which, when applied to a porous‐coated prosthesis, may enhance osseous ingrowth and mechanical stability. TCP plasma‐sprayed and unsprayed porous‐coated tibial intramedullary rods were bilaterally implanted in seven adult rabbits. All rabbits were killed at 12 weeks. Pull‐out tests were performed on 4 rabbits while all were evaluated histologically for osseous response and adverse tissue reaction. TCP‐sprayed implants showed significantly greater osseous ingrowth in comparison to unsprayed implants. Neither implant type exhibited adverse tissue reactions. Average pull‐out strengths were 69 lb for treated rods and 72 lb for controls (p > 0.05); quality of fit for all pull‐out specimens except one was deemed poor. We conclude that plasmasprayed TCP enhances osseous ingrowth into porous‐coated devices. However, our data further suggest that enhanced ingrowth may not always lead to enhanced fixation.
In vitrocorrosion fatigue of 316L cold worked stainless steel
Authors: Taira Masayuki , Lautenschlager Eugene P.
Published: December 2004

The corrosion resistance of 316L cold worked stainless steel depends upon its thin protective oxide layer; and if this is partially broken down, corrosion resistance depends upon its tendency for repassivation. Since the intended function of stainless‐steel implants is to sustain musculoskeletal forces, research toward the stability of the oxide film during dynamic loading in simulated bodylike fluids is warranted. A pilot corrosion fatigue study was, therefore, performed on uniaxial tension fatigue specimens cycled to various maximum stress levels near their yield point while immersed in 37°C isotonic saline solution, and combined with the electrochemical insult of (a) imparting an 800 mV vs. SCE anodic potential for 20 s to stimulate local film breakdown, and then (b) returning to a constant 200 mV vs. SCE anodic potential and maintaining that potential during cyclic loading until the specimens broke in two. During the anodic polarization by continuously monitoring the current it was possible to (a) observe the repassivation and corrosion behavior following stimulation, and (b) detect crack initiation, crack propagation and failure onset. The combined effects of accelerated corrosion and mechanical fatiguing disturbed the repassivation tendency and reduced the crack initiation times and the fatigue lives as compared to air and saline controls. As the maximum cyclic load levels were increased, the fatigue lives were further foreshortened.
Protein interaction with tantalum: Changes with oxide layer and hydroxyapatite at the interface
Authors: Sharma Chandra P. , Paul Willi
Published: December 2004

For metallic implants the surface nature is extremely important because blood and tissue interactions with metal depend upon it. Protein adsorption is the initial reaction that takes place when an implant comes in contact with blood or tissue. We attempted to coat different thicknesses of oxide layers and hydroxyapatite on tantalum and examined the changes in water contact angle and adsorption of albumin and fibrinogen. Protein adsorption studies were performed with 125I‐labeled proteins. A decrease in water contact angle was observed as the oxide layer thickness of tantalum increased. Fibrinogen adsorption increased on oxide layer coated and hydroxyapatite coated surfaces, compared to bare tantalum. © 1992 John Wiley & Sons, Inc.
Prevention of tissue calcification on bioprosthetic heart valve by using epoxy compounds: A study of calcification tests in vitro and in vivo
Authors: Tingfei Xi , Jiazhen Ma , Wenhua Tian , Xuehui Lei , Shuhui Long , Baoshu Xi
Published: December 2004

Calcification is the principal cause of the clinical failures of the bioprosthetic heart valves fabricated from glutaraldehyde pretreated porcine aortic valves or bovine pericardium. In this paper, we compared the calcification on various types of bovine pericardiums pretreated with two hydrophilic epoxy compounds adding GA post‐treatment (EP 1 and EP 2), glutaraldehyde (GA)‐ and nontreated pericardium (Fresh), respectively, by in vitro and in vivo tests. Significant decrease of calcification was found by pretreatment with both epoxy compounds rather than with glutaraldehyde : 0.250 ± 0.001 (Fresh), 0.276 ± 0.058 (EP l), 0.302 ± 0.071 (EP 2), and 0.478 ± 0.172 (GA) μg (Ca)/mg (dried tissue), respectively, after 20 days dipping in a simulating serum solution in vitro; 115.13 ± 60.11 (Fresh), 129.84 ± 51.08 (EP 1), 167.39 ± 20.81 (EP 2), and 205.19 ± 16.86 (GA) pg/mg, respectively, after 3 months subcutaneous implantation i n rabbits. The in uifro method for evaluating calcification designed by us gave the similar order among four samples with that obtained by in uiuo test. Because the bovine pericardium pretreated with the epoxy compounds adding GA post treatment possesses the greater tenacity than that pretreated only with epoxy compounds or GA, meanwhile the calcification is also significantly decreased with this pretreatment, it may be expected that the bovine pericardium with this pretreatment will have the greater anticalcification and durability in dynamic stress. © 1992 John Wiley & Sons, Inc.
The effect of calcium phosphate ceramic composition and structure on in vitro behavior. II. Precipitation
Authors: Radin S. R. , Ducheyne P.
Published: December 2004

The formation of a biologically equivalent carbonatecontaining apatite on the surface of synthetic calcium phosphate ceramics (CPC) may be an important step leading to bonding with bone. Reactions of several single phases CPCs upon immersion into a simulated physiologic solution (SPS) with an electrolyte composition of human plasma were determined. The CPCs covered a wide range of solution stabilities from low‐soluble hydroxyapatites (HA) to metastable tricalcium phosphates (TCP) and tetracalcium phosphate (TTCP). Changes in chemical composition of SPS and infrared spectral features after CPC immersion were analyzed. New phase formation was observed on all the CPCs. However, kinetics, compositions, and structures of the new phases were significantly different. The studied CPCs can be characterized by the time to new phase formation in vitro; the minimum time for measurable precipitate formation was found to increase in the order: not‐well‐crystallized HAs < well‐crystallized HAs < α‐TCP, TTCP < β‐TCP. Among the CPCs only not‐well‐crystallized HAs led to immediate new phase formation. The metastable CPCs, β‐TCP, α‐TCP, and TTCP required an induction time during which dissolution occurred. β‐TCP showed the longest induction time and the lowest lattice ion uptake rate of all the CPCs tested. Only the not‐well‐crystallized HAs elicited immediate formation of carbonated HA. The well‐crystallized HAs and β‐TCP did not elicit carbonated apatite formation within the time frame of the experiment. Instead, intermediate phases were formed. On α‐TCP amorphous calcium phosphate (ACP) with a relatively low carbonate content was formed. TTCP was found to transform extensively to poorly crystallized carbonated apatite after 2 days of immersion. © 1993 John Wiley & Sons, Inc.
Extensive porosity at the cement–femoral prosthesis interface: A preliminary study
Authors: James S. P. , Schmalzried T. P. , McGarry F. J. , Harris W. H.
Published: December 2004

This study is the first description of the extensive porosity which is preferentially located at the cement‐prosthesis interface of cemented femoral components of total hip replacements. The observation is important because the interfacial porosity may decrease the strength of the cement‐femoral prosthesis interface and jeopardize the mechanical integrity of the cement mantle. We examined the cement‐metal interfaces from a multiplicity of in vivo and in vitro specimens using both optical and scanning electron microscopy. These samples included several stem designs, implants made from either Co‐Cr or Ti alloy, implants made with a variety of surface finishes and both centrifuged and uncentrifuged cement. All in vivo and in vitro samples had marked porosity in the cement focally concentrated at the cement‐metal interface. The amount of porosity at the interface greatly exceeded the amount of general porosity found throughout the bulk cement. Centrifuging did not affect the interfacial porosity, and neither did alloy nor surface finish. The presence of these pores may be expoained by the rheological characteristics of the cement. © 1993 John Wiley & Sons, Inc.
Bacterial adhesion to poly(HEMA)‐based hydrogels
Authors: Cook Alonzo D. , Sagers Richard D. , Pitt William G.
Published: December 2004

The effects of water content and comonomer chemistry upon the adhesion of Pseudomonas aeruginosa to poly(hydroxyethyl methacrylate)‐based hydrogels were studied. Hydrogels which varied in swollen water content from 33–69 wt% were polymerized onto glass microscope slides pretreated with a vinyl silane. The hydrogel water content was varied by adding methacrylic acid (1–5 wt%) orN‐vinyl pyrrolidone (NVP, 10–25 wt%) or combinations of the two comonomers. The resulting hydrogel surfaces, which were 0.1 mm thick, transparent, and adherent to the glass slide, formed the test surfaces of laminar flow cells (Re = 1.3, wall shear rate = 1.6/s). The bacteria were grown for 8 h in tryptic soy broth (TSB), washed by filtration, and collected on 0.45‐μm filters, resuspended in phosphate buffered saline (PBS) at pH = 7.2, and recirculated through the flow cell and across the test surface at 0.85 mL/min for 2 h. Results show that P. aeruginosa adhered less to hydrogels with higher water contents. In the presence of TSB and possible poly(NVP) contamination, the concentration of adherent bacteria was reduced to low and uniform levels independent of the hydrogel chemistry. © 1993 John Wiley & Sons, Inc.