bluuebunny/crossref_metadata_2025 huggingface dataset:
Surface energies and the bone induction principle
Authors: Eriksson Christopher
Published: December 2004

The 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

The 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

Electron 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

Polyanhydrides 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

This 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

The 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

Pepsin‐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

The 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

The 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

A 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.
Synthesis and bioevaluation of alkyl 2‐cyanoacryloyl glycolates as potential soft tissue adhesives
Authors: Jaffe H. , Wade C. W. R. , Hegyeli A. F. , Rice R. , Hodge J.
Published: December 2004

A series of alkyl 2‐cyanoacryloyl glycolate tissue adhesives were synthesized and characterized by NMR. Physical properties and bond strengths are presented. Within the series, bond strength decreased with increasing molecular weight. Corresponding polymers were evaluated by in vitro and in vivo techniques for biocompatibility. In general, in vitro biocompatibility increased with molecular weight. Based on in vitro and in vivo results, the isobutyl and isoamyl derivatives gave polymers that were most biocompatible, however, the entire series was found to be less reactive than poly(methyl 2‐cyanoacrylate) and only the isopropyl derivative polymers more reactive than poly(isobutyl 2‐cyanoacrylate). Approximately one‐third of the isobutyl polymer biodegraded in vivo after 6 weeks.
Composites for use in posterior teeth: Mechanical properties tested under dry and wet conditions
Authors: Øysæd Harry , Ruyter Ivar Eystein
Published: December 2004

The purpose of this investigation was to determine some mechanical properties of eight different posterior composites, and how they are affected by water sorption. Creep characteristics in compression were expressed as compliance/log time functions. Stress‐strain relationship at a constant loading rate was determined both in compression and flexure, and presented as elastic modulus, ultimate strength, and ultimate strain. Water sorption increased creep values for all materials. Generally, the materials with the highest water sorption had the highest increase in creep. Water sorption decreased the elastic modulus and ultimate strength values. The creep values decreased and the elastic modulus increased with increasing quantity of inorganic fillers.
Zinc release from dental restorative materials in vitro
Authors: Meryon S. D. , Jakeman K. J.
Published: December 2004

Zinc release from a range of dental restorative materials was measured in the absence and presence of dentin over a 2‐week period. The presence of dentin was designed to simulate the residual dentin in vivo. There were considerable differences in both the levels and pattern of zinc release for the different materials. In several cases the concentrations exceeded the level which has been reported cytotoxic to cells in culture. With dentin, little zinc passed into solution, and high concentrations were measured in the dentin. This may explain the discrepancy between in vivo toxicity tests using zinc‐containing materials and previous in vitro tests which have not included dentin in the test system.
A simple method to heparinize biological materials
Authors: Noishiki Yasuharu , Miyata Teruo
Published: December 2004

A new method was developed inducing antithrombogenicity to biologic materials. A basic protein, protamine, was used to increase heparin binding to collagenous materials. Protaminie sulfate solution was poured into a collagen‐rich material (porcine ureter). The protamine adsorbed to the collagen was then cross‐linked to the material by glutaraldehyde. The collagen‐protamine complex was then interacted with a heparin solution to ionically bind heparin to the material. The amount and the distribution of the bound heparin can be controlled by changing the protamine fixation to the material. A heparinized porcine ureter as a vascular substitute showed excellent antithrombogenicity in experimental animal studies. This method is expected to be used as a method for developing antithrombogenic artificial organs, and as a method for the development of antiadhesive membranes.
Polyacrylic acid–metal adhesive bond joint characterization by x‐ray photoelectron spectroscopy
Authors: Nasu Toshio
Published: December 2004

The adhesive force to human tooth and metallic restoration of dental cements which contain polyacrylic acid (PAA) is found to be stronger than that of previous cements. Chemical interaction at the interface between metals and carboxylate groups of PAA were studied by x‐ray photoelectron spectroscopic method combined with Ar+‐ion beam etching technique to examine the mechanism of adhesion. A 2.5 wt% aqueous solution of PAA was painted on the surface of metal plates which are usual elements of dental alloy. Ar+‐ion etching was used to scrape off in situ the PAA film coated on the metal plate gradually in the sample chamber of the ESCA equipment. After a few minutes of etching, ESCA spectra were observed. The profile of the spectra and binding energy of 4f5/2 and 4f7/2 levels of Au coated with PAA show little change by the Ar+‐ion etching, and remain in the same state as those of uncoated Au. Similar behaviours were obtained in case of Pt. There are three chemical states on Sn plate coated with PAA. The lowest binding energy peak is assigned to pure Sn. The middle one is assigned to SnO2. The highest one corresponds to Sn combined with carboxylate groups of PAA. The chemical reaction corresponding to the highest binding energy peak seems to contribute to the strong adhesive force of these cements to Sn. These aspects of spectra corresponded to McLean's results which showed that these cements had weak adhesion to Au and Pt, but strong adhesive force to tinned Au and Pt.
On the correlation between the failure of vascular grafts and their structural and material properties: A critical analysis
Authors: Pourdeyhimi B. , Wagner D.
Published: December 2004

A statistical investigation of reported vascular graft failures over a period of 30 years is undertaken. The most important causes of graft failure are underlined, as well as the time to failure and relative frequency of each failure mechanism. This brings out the need for a critical review of the properties of basic textile structures used in today's vascular prosthetic grafts. The physiologic and structural factors which contribute to mechanical failure of arteries and artery/implant composite systems are analyzed. The importance of obtaining the complete set of time‐dependent elastic constants of the artery—which is viewed as an anisotropic material—is pointed out. Future research areas important for characterizing the mechanical behavior of artery/implant systems are suggested, with the aim of establishing rational standards for prosthesis evaluation.
Ex vivo interactions and surface property relationships of polyetherurethanes
Authors: Lelah Michael D. , Grasel Timothy G. , Pierce Jeffrey A. , Cooper Stuart L.
Published: December 2004

Despite the use of polyurethanes in a number of blood‐contacting applications, little is known about the contributing effects of the various polyurethane components in thrombogenesis. In order to investigate blood‐polyurethane interactions, a number of different polyurethanes were examined in an acute canine ex vivo series shunt experiment. Multiprobe surface characterization techniques, including contact angle measurements, ESCA, ATR‐IR, and SEM were used to obtain surface property information on the materials studied. The polyurethanes examined included several with different soft segment types, a series of materials with different hard segment diisocyanates and chain extenders, a series consisting of the same polymer cast from different solvents, a zwitterionomer, and a hard segment analog. Two commercial urethanes were also examined, and the effect of methanol extraction on these materials was studied.

The blood‐contact and surface characterization results indicated that both the surface concentration and type of hard segment were of importance in determining blood response. The relative concentration of hard segment on the polymer surface was found to affect the observed blood‐material interaction, although the extent of this effect was found to depend on the hard and soft segment components of the copolymer system. Both the surface properties and thrombogenicity of a particular polyurethane were changed by casting from different solvents, indicating the need to optimize and control fabrication conditions. Methanol extraction was found to improve the thromboresistance of the commercial polyurethanes.
Quantitative surface analysis of cardiothane 51 by FT‐IR‐ATR spectroscopy
Authors: Iwamoto Reikichi , Ohta Koji , Matsuda Takehisa , Imachi Kou
Published: December 2004

Surface analysis has been carried out for Cardiothane 51 samples as commercially available balloon pumps and cast films prepared from the solution. Silicone contents on surfaces have been quantitatively determined by FT‐IR‐ATR spectroscopy coupled with a subtraction technique. The contents on the air‐facing surface vary from 0.7 to 5.3% among six balloon pumps examined; three of them contain less silicone on the air‐facing surface than on the substrate‐facing surface, whereas just the opposite is true for one, and the other two have nearly and quite an equal content of it between the two surfaces. Silicone contents on surfaces of cast films vary also from a sample to another even when sample films were prepared from the same Cardiothane solution, indicating difficulty in quality control of Cardiothane surfaces. An appreciable fraction of silicone was found not to be covalently bonded to polyurethane in Cardiothane 51 for the cast film samples.
Mechanical properties of polymeric membranes obtained by radiation cast‐polymerization of hydroxyalkyl and hydroxypolyethyleneglycol methacrylate monomers
Authors: Kumakura M.
Published: December 2004

Polymeric membranes have been prepared by radiation cast‐polymerization of hydroxyalkyl and hydroxypolyethyleneglycol methacrylate monomers, and the mechanical properties of the membranes before and after swelling have been studied as a function of the molecular structure of the monomers. The degree of hydration of the polymers from hydroxypolyethyleneglycol methacrylate monomers increased with increasing the number of ethyleneglycol units in the monomers, and that from hydroxyalkyl methacrylate monomers decreased with an increase in the number of methylene units. The mechanical properties such as tensile strength, tear strength, Young's modulus, and elongation at break varied with the length of the methylene and ethyleneglycol units in the monomers. It was found that flexible polymeric membranes having various properties for medical applications could be obtained by radiation cast‐polymerization of hydroxyalkyl and hydroxypolyethyleneglycol methacrylate monomers.
Use of concentrated fibrinogen in experimental splenic trauma
Authors: Kram Harry B. , Hino Stanley T. , Harley Daniel P. , Fleming Arthur W. , Shoemaker William C.
Published: December 2004

This study evaluated Fibrin Sealant (FS), a two‐component biologic adhesive that is effective in establishing hemostasis, in 27 experimentally produced splenic injuries in five adult mongrel dogs. Ten small superficial lacerations (2.0 cm in length), six large superficial lacerations (3.0–6.0 cm in length), three small wedge resections, and eight stab wounds extending into the splenic hilum were effectively repaired with FS without suture splenorrhaphy or temporary splenic hilar occlusion. Complete hemostasis was achieved in all animals prior to skin closure. Dogs were reexplored postoperatively at intervals varying from 4 h to 6 weeks. When animals were killed, there was no gross evidence of splenic disruption or recurrent bleeding; the spleens all had developed well‐healed capsules. Histologic examination demonstrated a regenerated fibrous capsule extending over the injuries without significant inflammatory response. We conclude that FS (1) provides adequate hemostatic control of superficial and deep splenic injuries; (2) has good systemic and local compatibility; (3) can be applied to bleeding parenchymal wounds; organ ischemia is generally not required; (4) avoids the use of parenchymal sutures, which may be traumatic; and (5) may promote splenic wound healing. Thus, use of FS is an effective technique for splenic preservation after trauma.
The effect of annealing treatments on the tensile properties and hydrolytic degradative properties of polyglycolic acid sutures
Authors: Browning Abigail , Chu C. C.
Published: December 2004

The purpose of this research was to examine the effect of annealing treatments on the mechanical properties of polyglycolic acid sutures, and their subsequent influence on PGA degradation properties. An attempt was made to develop a better understanding of the degradation mechanism of synthetic absorbable sutures, including the relationship of their structure, morphology, and mechanical properties. PGA sutures were annealed under selected axial strain (freely hung, 0%, 1%, 10%), at four temperatures (150°C, 170°C, 180°C, 190°C), and two times (5 and 20 min). The annealed PGA specimens were then subjected to hydrolysis in phosphate‐buffer solutions (pH = 7.4) for up to 28 days at 37°C. Tensile properties were used to evaluate the effect of annealing treatments. The data were subjected to statistical analysis using the SAS system. All of the one‐, and many of the two‐ and three‐factor interactions were found to be statistically significant. Annealing treatments did alter the mechanical properties of PGA sutures, as well as their degradation properties. Except for the increase in tenacity of samples with increasing percent extension, all other respects of the annealing treatments resulted in lower tenacity and breaking elongation when compared with the control samples. Sutures that have been exposed to any level of axial tension during annealing, however, exhibited a lower rate of hydrolytic degradation than the freely hung suture samples. The reduction of the characteristics of fiber structure due to the tendency of the tie‐chain molecules to acquire the less constrained conformations and thus to bring the crystal blocks they connect back to the original arrangement before drawing is believed to be responsible for the freely hung specimens to behave quite differently from the clamped and stressed PGA samples.
Quantitative characterization of cells at the interface of long‐term implants of selected polymers
Authors: Behling Cynthia A. , Spector Myron
Published: December 2004

Comprehensive understanding of the relationship between biologic response and biomaterial characteristic requires quantitative evaluation of the cells at the interface of the material and descriptions of untrastructural features of these cells. The purpose of this study was to qualitatively and quantitatively characterize the long term in vivo tissue and cellular response to two polymeric materials presently employed in the fabrication of surgical implants. Ultrahigh molecular weight polyethylene (PE) and polysulfone (PSF) particles were implanted subcutaneously into rats for 100–118 weeks. Specimens were embedded in paraffin and ERL embedding medium in preparation for light and transmission electron microscopy. Percentage of the particle surface covered by various cell types was determined using a computer interactive image analysis system. PE and PSF particles were sequestered within a subcutaneous fibrous capsule. Cell types present included macrophages, fibroblasts and giant cells characteristic of a foreign body granuloma. Statistical comparison of the percent particle surface covered by each cell type revealed no significant difference between PSF and PE. However, surface texture appeared to influence the tissue response. TEM confirmed the identity of the cells at the interface and consistently revealed a layer of amorphous extracellular substance including cell debris on the material surface. Results evidence the tissue compatibility of PE and PSF and indicate no significant difference in the tissue response to these polymers.
Ligament and tendon substitution with composite carbon fiber strands
Authors: Mendes David G. , Iusim Mauricio , Angel David , Rotem Assa , Mordehovich Dan , Roffman Moshe , Lieberson Samuel , Boss Jochanan
Published: December 2004

Carbon fiber strands were used experimentally to substitute for tendons in dogs and clinically to reconstruct tendons and ligaments in human. The investigation was carried out to determine the histologic appearance of the new composite structure and its tensile strength in comparison to the natural structure. The histologic picture disclosed a remarkable structure evolved by continuous irritation of the carbon fibers and consisting of two interrelated components: synthetic carbon fibers and biologic collagenous tissue. This carbon fiber composite structure was composed of long cylindrical units containing concentric layers of collagenous fibers and cells enveloping the core of each carbon fiber. After one year of physiologic use in dogs, the average ultimate tensile strength of the composite structure which replaced the quadriceps and triceps was 372 N, or 88% the strength of the natural tendons. One year after implantation the histologic picture of the composite structure in human showed a relatively dense collagenous architecture. However, a significant proportion of the structure was taken up by histiofibroblasts produced by the irritation of the carbon fibers. Thus, the density of the collagen in the composite structure remained relatively deficient in comparison to the nature tendon, and the structural tensile strength continued to depend entirely on the integrity of the carbon fibers.
Pulmonary reaction to intravenously injected polymer beads
Authors: Schoen Frederick J. , Kintanar Esperanza B. , Osol Rosalie G. , Lee Ellen
Published: December 2004

The purpose of this study was to characterize the foreign body reaction in the mouse lung following embolization of intravenously injected divinylbenzene copolymer beads. In contrast to usual surgical implantation, this model dissociates the local foreign body reaction to the beads (in the lung) from inflammation and repair of tissue injury associated with implantation (peripheral site of injection). Quantitative determinations of pulmonary granuloma area using light microscopic morphometric measurements on tissue sections confirmed that the intensity of pulmonary inflammatory reaction increased rapidly to a maximum at 48 h following injection, with a volume exceeding 10 times that of the bead; at this time, the cellular exudate was 90% polymorphonuclear leukocytes. Thereafter, the inflammatory reaction decreased in intensity, and individual lesions became progressively richer in mononuclear cells (60% at 4 days and greater thereafter). Determination of intra‐ and interobserver variability indicated that maximal data precision was attained by measurement of the cross‐sectional areas of as few as 10 granulomas in each of five animals for each set of specific experimental conditions. Collagen was undetectable in granulomas at 7 weeks and 6 months, suggesting that the usual fibrous capsule forming in response to surgically implanted biomaterials is largely caused by repair of surgical trauma. The volume of inflammatory exudate at 48 h was reduced 68–86% by the nonsteroidal antiinflammatory agents indomethacin, aspirin, and ibuprofen and the antiinflammatory steroid methylprednisolone. Thus, the pulmonary bead granuloma model is a quantitative, reliable, and economical approach to investigating some aspects of biomaterial/time interactions in the absence of superimposed surgical trauma.
Red blood cells deposit membrane components on contacting surfaces
Authors: Borenstein N. , Brash J. L.
Published: December 2004

An investigation of red blood cell interactions with “foreign” surfaces is reported. Experiments consisted of flowing suspensions of washed human red cells through a packed column of either glass or siliconized glass beads. Conditions were chosen so that hemolysis was minimized. The column was washed to remove suspended red blood cells and then eluted. Samples of beads were examined by SEM after washing and before elution. The eluate was examined by UV/visible spectroscopy and SDS‐PAGE; for both types of packing it was found to contain cell membrane components. It is therefore concluded that membrane material is deposited on the bead surface as the cells flow through the column. The SDS‐PAGE data show that membrane skeleton proteins are essentially missing from the eluate, while SEM examination indicates the presence of filamentous deposits on the bead surfaces. These data suggest that cell‐surface interaction may occur through a tether‐type mechanism involving extrusion of part of the membrane including the integral membrane proteins.
Omiderm, a new synthetic wound covering: Physical properties and drug permeability studies
Authors: Behar D. , Juszynski M. , Ben Hur N. , Golan J. , Eldad A. , Tuchman Y. , Sterenberg N. , Rudensky B.
Published: December 2004

Omiderm (Omikron Scientific Ltd., Rehovot, Israel), a new synthetic wound covering based on hydrophilized polyurethane, was found to be highly permeable to water. Values in the region of 5000 g/m2 24 h were found for the water permeability of Omiderm in comparison to 1400 and 500 g/m2 24 h for Biobrane (Hall, Woodroof Inc., Santa Ana, CA) and Op site (Smith and Nephew Ltd.), respectively. Permeabilities of antibacterial agents through Omiderm were found to be two to three orders of magnitude greater than those through Biobrane. The in vitro effectiveness of various antibacterial agents in lowering bacterial growth of different bacterial strains when applied to seeded agar plates through Omiderm membrane was investigated. NBH ointment (1% Neomycin, 1% Bacitracin, and 0.5% Hydrocortisone) was found to be the most effective material in inhibiting bacterial growth, except for Pseudomonas aeruginosa where silver sulfadiazine was superior. In in vivo experiments bacterial counts of infected wounds covered with Omiderm and topically treated with NBH were lowered to less than 103 organism/g tissue after one day of treatment.
Comparison of in vitro bacterial bioluminescence and tissue culture bioassays and in vivo tests for evaluating acute toxicity of biomaterials
Authors: Burton S. A. , Petersen R. V. , Dickman S. N. , Nelson J. R.
Published: December 2004

The sensitivity of a bacterial bioluminescent acute toxicity test was compared to the sensitivity of the USP mouse safety, rabbit intramuscular implantation, rabbit intracutaneous, mouse systemic injection, and the MEM elution tissue culture tests. A variety of industrial plastics were used to evaluate the comparative sensitivities. Additional tests were conducted on lowdensity polyethylene containing a range of dibutyltin dichloride or trans‐cinnamic acid concentrations. The bacterial bioluminescent test was more sensitive than any of the in vivo acute toxicity tests. The luminescent bacteria test was generally more sensitive than the tissue culture acute toxicity assay. The bacterial bioluminescent test offers a sensitive, rapid, uncomplicated, and inexpensive means for preliminary compatibility evaluation of biomaterials.
Fracture analysis of retrieved orthopedic wires
Authors: Baswell Imogene L. , Sander Tom , Allen Ben , Bechtol Charles O.
Published: December 2004

Ten retrieved samples of 316L stainless steel wires, implanted for times from 11 months to 11 years, were examined fractographically and metallurgically to evaluate the effects of a physiological environment on their fracture. Seven samples were from L‐rod instrumentation, and three samples were from trochanter reattachment. Of 16 breaks in the 10 samples, 94% were caused primarily by cyclic loading (fatigue), and 6% were caused by tensile forces. Two factors were found to influence the effective life of an implanted wire. First, the surface condition (deformation) appeared to be most important, and second, corrosion pits present on most wire surfaces could possibly be an influence in initiating a crack. Biomechanical forces on wires enveloping L‐rods tended to promote metal deformation and faceting, which decreased time to fracture. This decrease in wire life was evident from a substantial hardness increase in faceted areas.
Collagen at interfaces I. In situ collagen adsorption at solution/air and solution/polymer interfaces
Authors: Deyme Michel , Baszkin Adam , Proust Jacques Emile , Perez Eric , Boissonnade Marie Martine
Published: December 2004

Collagen was isolated from rat tail tendons and acetylated with 1–14C acetic anhydride. In situ adsorption of this collagen from a buffer solution (pH = 2.7) was measured at the interfaces to air, polyethylene and polyethylene grafted with poly(maleic acid), respectively.

The kinetics of adsorption were recorded for all surfaces studied and the corresponding diffusion coefficients for collagen in solution with various protein concentrations were calculated. The desorption of collagen from polymer surfaces was also studied.

These experiments reveal the existence of both a reversibly and an irreversibly adsorbed collagen layer on the polymers tested. The desorption/adsorption ratio for the polyethylene is higher than that for the grafted polyethylene indicating stronger interactions of collagen with the grafted surface than with the non‐modified polyethylene.
Polymer coating for hemoperfusion over activated charcoal
Authors: Hasirci N. , Akovali G.
Published: December 2004

Plasma polymerization (glow discharge) was used to make a polymeric coat with hexamethyldisiloxane on the surface of activated charcoal granules. These samples were examined with ESCA and SEM for surface chemical analysis, coat thickness, and uniformity, and for changes in surface topography. The effects of the coat on absorptive capacity and release of fine particles were examined.
Suppression of platelet activity on microdomain surfaces of 2‐hydroxyethyl methacrylate‐polyether block copolymers
Authors: Okano Teruo , Uruno Michio , Sugiyama Norihide , Shimada Masashi , Shinohara Isao , Kataoka Kazunori , Sakurai Yasuhisa
Published: December 2004

Block copolymers constructed from chains of poly(2‐hydroxyethyl methacrylate) (PHEMA) and either poly‐ethyleneoxide (PEO) or poly‐propyleneoxide (PPO) were synthesized. These block copolymers exhibited microdomain structure. Platelet adhesion on their surfaces was investigated by a column elution method to examine the effect of microdomain structure. The number of platelets adhered from whole blood was smaller for the block copolymer systems than for the homopolymers. Minimum points of platelet adhesion appeared at approximately 0.38 mol fraction of HEMA in the HEMA‐PO system. Both block copolymer surfaces showed microdomains of alternate lamellar structure. Furthermore, the percent of platelets released from the column after incubation was investigated using PRP. In the case of homopolymers, released platelet percentages decreased with an increase of incubation time. Released platelet percentages from the block copolymers, however, were nearly constant with changing incubation time. These results showed that HEMA‐EO and HEMA‐PO block copolymers had the ability to suppress both reversible and irreversible adhesion of platelets to their respective microdomain surfaces.
Influence of mixing technique on some properties of PMMA bone cement
Authors: Eyerer P. , Jin R.
Published: December 2004

PMMA bone cements (Refobacin‐Palacos R, Sulfix 6, AKZ, and CMW bone cement, types I and II), from six different clinics, were investigated in three stages. In the first stage, studies of density, hardness, flexural strength, and compressive strength were made, as well as molecular weight measurements and microscopic investigations. These studies reflected the current state of techniques of application used in operating theaters. They revealed wide variations in the properties of the materials studied.

Secondly, a comprehensive study of the process‐technology in the laboratory was performed. The following variables were investigated or discussed: mixing vessel, order of the individual components, mixing time, rate of mixing, pressure application on the mixed bone cement, kneading, cement thickness, pouring into the syringe, contact force during polymerization, and preparation quantity.

The third stage involved the development and clinical testing of an improved mixing technique. Using this improved mixing technique, all three selected clinics achieved far better results with reduced variability. A comparison between a centrifuging technique after mixing and our improved, but conventional, mixing technique, displays advantages for the latter.

The question regarding a correlation between cement specimens of high porosity and early implant loosening could not be answered on the basis of the 43 PMMA bone cement explants investigated (implanted 6 months to 15 years).

In some cases, the studies revealed that the bone cement manufactureres should be required to revise and quantify existing instructions for use. The users, on the other hand, should give more consideration to the mixing technique and its consequences.
Bonding strength of alkyl‐2‐cyanoacrylates to bone in vitro
Authors: Kilpikari J. , Lapinsuo M. , Törmälä P. , Pätiälä H. , Rokkanen P.
Published: December 2004

This study measured the bonding strength between alkyl‐2‐cyanoacrylates and bone, and examined how treatment of the bone surface with acid, and prolonged exposure to moisture, affected this strength. The initial strength of all cyanoacrylates was high (9.6–11.2 N/mm2). In long‐term experiments under water, n‐ and i‐butylcyanoacrylates lost their strength at a far slower rate than ethylcyanoacrylates. However, the butylcyanoacrylates also showed a decrease of 15% in strength after three weeks. Pretreatment of the bone surface with acid did not have a marked effect on bonding strength, although SEM investigation revealed that the acid treatment had increased the porosity of the bone surface. A study of the fracture surface proved that the adhesive film tended to loosen or break after 3 to 6 weeks under water. The decrease in the bonding strength was probably due to the degradation of the adhesive film in water which loosened mechanical bonds between the bone and adhesive. Considering clinical use it would be necessary to achieve better long‐term strength.
Short‐term biocompatibility studies of hydrogel‐grafted collagen copolymers
Authors: Amudeswari S. , Nagarajan B. , Reddy C. Rami , Joseph K. Thomas
Published: December 2004

Synthetic hydrogels are an interesting class of biomaterials. Hydrogels were prepared by the graft copolymerization of either HEMA and MMA or HEMA and GDMA onto soluble collagen using different cross linking agents. The tissue compatibility of these hydrogels was studied by implantation in rats. It was observed that there were no untoward rejection phenomena of these gels when implanted in vivo except for the typical healing process. The hydrogels were well tolerated and might well serve as good tissue equivalents.
In vitro testing of dental materials by means of macrophage cultures I: Methodological aspects
Authors: Syrjänen Stina , Nilner Krister , Hensten‐Pettersen Arne
Published: December 2004

Macrophages play a central role in the pathogenesis of inflammation. In addition, activated macrophages are the first cells to come in contact with foreign particles in tissue. In the present study the applicability of macrophages for In vitro biological screeining of dental materials was tested. Monolayers of murine peritoneal macrophages were prepared. After three days culture the macrophages were inoculated with alloy particles prepared from silver and tin (Ag3Sn), the γ‐phase of dental silver‐amalgam. After different inoculation periods the macrophages were fixed and examined with phase contrast microscopy, scanning electron microscopy, and energy dispersive x‐ray analysis. Comparison with phagocytosis of particles injected intraperitoneally was also performed. Macrophage cultures inoculated with Latex particles served as controls. Ten minutes after inoculation with alloy particles, about 58% of the macrophages had ingested particles. EDAX‐analysis indicated that the phagocytized alloy particles contained both silver and tin in the same proportions as in the original alloy. When the cultures had been inoculated for ten days, however, a marked reduction in phagocytosis was observed probably due to cytolysis of those macrophages which initially had phagocytized the alloy particles. The results indicate that, although the Ag3Sn alloy particles at all the time intervals studied were phagocytized more slowly and to a lesser extent than the Latex particles, the method could be of value in studying the biocompatibility of dental materials available in particulate form.
The biological performance of calcium phosphate ceramics in an infected implantation site III: Biological performance of β‐whitlockite in the noninfected and infected rat middle ear
Authors: Van Blitterswijk C. A. , Grote J. J. , Koerten H. K. , Kuijpers W.
Published: December 2004

The biological performance of macroporous β‐whitlockite implanted in the rat middle ear was evaluated. The material was studied in the non‐infected middle ear and in middle ears infected by Staphylococcus aureus. β‐whitlockite was quickly covered by a normal mucosa. One week post‐operatively the macropores were filled with exudate, fibrous tissue, and a small quantity of bone. Six months after the operation the greater part of the macropore area was filled with bone (74%); fibrous tissue accounted for 20%, and exudate for 5%. In histological sections, the macropore area of β‐whitlockite had increased by 68% after six months, indicating biodegradation. Macrophages and multinucleated cells were present in the vicinity of the implant and played a role in this biodegradation. Besides cytoplasmic vacuoles containing calcium phosphate, the cells showed smaller granules containing trace elements originally present in the implant material, such as silicon, titanium, aluminum, iron, and magnesium.