bluuebunny/crossref_metadata_2025 huggingface dataset:
The quasistatic and fatigue performance of the implant/bone‐cement interface
Authors: Raab S. , Ahmed A. M. , Provan J. W.
Published: December 2004

Loosening is a major cause of failure in total arthroplasties. The efficacy of the fixation systems depends not only on the bulk properties of the components but also on the interfaces through which they interact. This study was initiated to examine the implant/bone‐cement interface for four of the most commonly used implant materials, CoCrMo, Ti6Al‐4V, 316SSLVM and ultrahigh molecular weight polyethylene (UHMWPE). The surface preparation, specimen design, joining, and testing techniques were studied and then standardized in a manner which accurately represents current clinical procedures. The interfaces were tested for both their quasistatic and fatigue properties. Finite‐element and fracture toughness analyses of the quasistatic shear specimens were performed in order to provide results of an absolute nature which could be subsequently compared to bulk material properties of bone cement. The interfaces were tested “dry” (i.e., at room temperature and 50% R.H.) and in physiological saline at 37°C. The interfaces demonstrated both fracture toughness and fatigue properties far inferior to those of bone cement. A predominantly interfacial type failure was observed using SEM fractography. The ultimate compressive strength (U.C.S.) of bone cement was measured after prolonged exposure to saline at 37°C and showed no decrease in U.C.S. suggesting that the reasons for the interface strength reductions were interfacial rather than bulk in nature. The “wetting'” ability of bone cement was measured using contact angles at various cure times on the four implant materials. These measurements showed that intimate interfacial contact is impossible with current clinical methods. This study indicates that failure of the implant/bonecement interface is likely only a short period after implantation and therefore may be a major contributor to implant loosening.
Pressurized polymerization for reaction casting of poly(2‐hydroxyethyl methacrylate)
Authors: Pinchuk Leonard , Eckstein Eugene C.
Published: December 2004

Homopolymers of the hydrogel poly(2‐hydroxyethyl methacrylate) are produced with no observable bubbles trapped in the lattice by performing the free radical initiated polymerization reaction under pressure (700 kPa). Implantable hydrogel structures of intricate and exact geometry, such as nipples for ureteral anastomoses in the prosthetic urinary bladder, can be made using this technique.
Mechanical properties of poly(methyl methacrylate) bone cements
Authors: Robinson R. P. , Wright T. M. , Burstein A. H.
Published: December 2004

Samples of low viscosity poly(methyl methacrylate) (PMMA), graphite reinforced PMMA, and graphite reinforced low viscosity PMMA were evaluated for their compression strength and fracture toughness. These results were compared with two currently used plain PMMA bone cements. There were no statistically significant differences in compression strength between the five cements. Graphite reinforcement of plain cement produced a 32% increase in fracture toughness over plain cement. Graphite reinforcement of low viscosity cement also produced a significant increase in toughness (31%) over low viscosity cement with fiber reinforcement. However, low viscosity cement demonstrated significantly less fracture toughness than plain PMMA.
Effect of radiation sterilization and aging on ultrahigh molecular weight polyethylene
Authors: Roe Ryong‐Joon , Grood Edward S. , Shastri Ranganath , Gosselin Cynthia A. , Noyes Frank R.
Published: December 2004

The mechanical properties of polyethylene components used in prosthesis are altered after fabrication by the sterilization procedure and by the environmental and mechanical aging which occurs after implantation. To assess the importance and extent of these alterations, ultrahigh molecular weight polyethylenes from two sources, Hercules 1900 and RCH 1000C, were subjected to gamma‐ray irradiation and aging in serum and argon environments. Changes induced by these treatments in the structural and mechanical parameters have been determined by a variety of experimental techniques. The effect of irradiation is to introduce crosslinks and to increase the degree of crystallinity resulting in changes in the tensile properties in the direction of higher stiffness and reduced ductility. Aging for six months produced similar changes with subtle differences. The results suggest that the initially low degree of crystallinity which results from the sluggish mobility of the very long chain molecules offers the opportunity for significant changes in the properties during use in the long run.
Biological and mechanical behavior of autologous pericardium used for tricuspid valvular replacement in dogs
Authors: Dureau Georges , Kepenekian Georges , Heynen Yves , Paul Jacqueline , Tabib Alain , Clendinnen Guy , Belleville Jean , Eloy Rosy
Published: December 2004

The fate of autologous pericardium when used to replace a tricuspid valve leaflet has been investigated in dogs. Changes have been studied by means of macroscopic, mechanical, histological, scanning electron microscopy, and in vitro culture techniques. In each of nine experiments the valve failed and death occurred within the first 15 post‐operative days. Retraction, thickening of the cusp, fibrinous deposition and/or tissue rupture were associated with a decrease of resistance to traction tests, decrease of elasticity and increase of viscosity of the implanted tissue. The early behavior of autologous pericardium was characterized by precocious inflammatory reaction on the valve leaflets, focal disruption of the collagenous structure of the leaflets, absence of fibroblastic cell infiltration as confirmed by in vitro culture of implanted pericardium and the lack of endothelial‐like cell surface at the 10th–15th postoperative day.
Surface spectroscopic studies of avcothane
Authors: Graham Susan W. , Hercules David M.
Published: December 2004

Avcothane is a commercially available copolymer of polyether, polyurethane, and polydimethylsiloxane; it is used primarily in aortic balloon pumps. The pumps consist of three segments which are cemented or fused together to form the balloon. The objective of this work is to characterize the surfaces, inside and outside, of the three balloon pump sections. By using x‐ray photoelectron spectroscopy (ESCA), ion scattering spectroscopy (ISS), and secondary ion mass spectrometry (SIMS) a detailed analysis of the Avcothane surfaces can be performed and comparisons between various surfaces made. Previous workers have reported ESCA and Auger electron spectroscopy (AES) measurements of Avcothane and comparisons with their results will be presented. SIMS and ISS are useful analytical tools for studying polymeric biomaterials because these techniques are usually more surface sensitive than either ESCA or AES. SIMS and ISS data indicate that a thin fluorine‐rich film (probably a fluorocarbon polymer) is present on the Avcothane surface. Signals from the fluorine‐rich layer are more intense from the inside of the balloon pump and the intensity generally decreases from top to bottom. The outside sections of the aortic balloon pump also show the presence of fluorine, but the signals are far less intense than from the inside. One possible explanation for the fluorine‐rich layer is that a fluorine‐containing compound is deposited on the balloon pump during molding and preparation. Another possibility is that the layer is deposited during preparation of the Avcothane itself, but is essentially removed from the outside during sterilization.
Effect of hydrophilic and hydrophobic microdomains on mode of interaction between block polymer and blood platelets
Authors: Okano Teruo , Nishiyama Shoji , Shinohara Isao , Akaike Toshihiro , Sakurai Yasuhisa , Kataoka Kazunori , Tsuruta Teiji
Published: December 2004

ABA‐type block copolymers composed of 2‐hydroxyethyl methacrylate (HEMA), a hydrophilic monomer, and styrene (St), a hydrophobic monomer, were synthesized by the coupling reaction of telechelic oligomers used as prepolymers. These block copolymers may be represented as microphase‐separated structures. It is therefore possible to change the balance between hydrophilicity and hydrophobicity in the level of an assembled order of macromolecules. In response to the relative composition of the copolymers, three typical morphological patterns were observed in electron microscopic photographs: dispersed domains of continuous St chains in the region of HEMA chains, alternate HEMA and St lamellae and finally, dispersed phases of continuous HEMA chains in the region of St chains. The effect of the hydrophilic and hydrophobic microdomains of the copolymers on the mode of interaction between polymers and platelets was studied by the microsphere column method. In the case of homopolymers and random copolymers, a significant degree of platelet adhesion and aggregation was observed. However, the degree of platelet adhesion and deformation was suppressed on the surfaces of the block copolymers containing 0.608 and 0.347 mole fractions of HEMA whose microdomains were hydrophilic‐hydrophobic lamellae and isolated hydrophilic islands in hydrophobic areas, respectively. These results show that the microphase‐separated structures were antithrombogenic and prevented platelet adhesion and deformation. On the basis of the results obtained, the interaction between platelets and polymer surfaces was described in terms of the effect of hydrophilic and hydrophobic microdomains.
Permanent set and stress relaxation in elastomeric impression materials
Authors: Cook Wayne D.
Published: December 2004

The permanent set of a range of elastomeric impression materials, used in dentistry, was investigated as a function of the materials′ age and the duration and level of the deformation. The permanent set appears to be primarily controlled by the rate of polymerization at the time of deformation. However, stress relaxation experiments revealed that, for condensation silicone and in particular polysulfide elastomers, bond interchange reactions produce additional permanent set. The rate of recovery of the elastomers from deformation was very rapid and was consistent with the influence of entanglements in the network.
Friction and wear properties of polymer, metal, and ceramic prosthetic joint materials evaluated on a multichannel screening device
Authors: McKellop H. , Clarke I. , Markolf K. , Amstutz H.
Published: December 2004

A 12‐channel wear screening device was used to compare the wear properties of a variety of prosthetic joint materials. Two types of tests were run: (1) Ultrahigh molecular weight (UHMW) polyethylene bearing against metal or ceramic counterfaces and (2) various polymers bearing against 316 stainless steel as a standard counterface. Wear was quantified by weighing the polymer specimens, with presoaking and control‐soak specimens used to minimize the error due to fluid absorption. The specimens were lubricated with bovine blood serum. Friction and polyethylene wear was very low with each of the metals (316 stainless steel, cobalt‐chrome alloy, multiphase alloy, and titanium 6–4 alloy) such that the differences in wear rate would not be significant in terms of choosing a material for clinical application. However, titanium 6–4 alloy was found to be especially susceptible to abrasive wear by particles of acrylic cement. Nitrided titanium 6–4 counterfaces were impervious to acrylic abrasion. Polyethylene wear against highly polished, fully dense ceramics (Sialon, Alumina, Macor, and pyrolytic graphite) was as low as that with the metal counterfaces. Wear increased slightly with increasing ceramic surface roughness. The coefficient of friction of polyethylene against pyrolytic graphite was two to three times higher than with the metals or other ceramics. All of the alternate polymers underwent more wear than UHMW polyethylene. Teflon and polyester, two polymers that have proven unsuccessful in prior clinical use, had wear rates 1600 and 830 times greater than polyethylene, respectively, an indication that the laboratory wear test provided a quantitative prediction of the behavior of the materials in vivo. However, it was difficult to assess the clinical significance of the less extreme wear rates since the ability of the tissues encapsulating a prosthesis to accomodate wear debris is not known on a quantitative basis.
Development of a silica‐free silicone system for medical applications
Authors: Ashar B. , Ward R. S. , Turcotte L. R.
Published: December 2004

Filler‐free silicones are believed to be more blood‐compatible than those containing fillers. An ultrapure silica‐free room temperature vulcanizing silicone system was prepared and characterized using a swelling experiment, an infrared spectrometer, an x‐ray spectrometer, a scanning electron microscope and neutron activation analysis. The polymer was found to be suitable for medical applications needing an extremely smooth surface.
Adsorption of proteins from plasma to a series of hydrophilic‐hydrophobic copolymers. II. Compositional analysis with the prelabeled protein technique
Authors: Horbett Thomas A.
Published: December 2004

Plasma protein adsorption is an important initial event in the response of tissue to foreign materials. Little is known about the way in which the chemical properties of materials influence the nature of the adsorbed layer and thus the later cellular responses. In this study, the amounts of fibrinogen, immunoglobulin G, albumin, and hemoglobin adsorbed from plasma to a series of HEMA‐EMA random copolymers varying in hydrophilicity was measured. The adsorption of each protein varied in a characteristic way with copolymer composition probably reflecting a different affinity of the proteins for the various copolymers. A complex variation in the composition of the adsorbed protein layer on polymers varying in hydrophilicity was thus evident. Surface enrichment of the proteins, calculated as the ratio of the surface and bulk fraction of each protein, also varied with copolymer composition, and indicated substantial differences in the composition of the surface and bulk phases. Surface area variations among the copolymers, preferential adsorption of 125I proteins, and the possibility of structural degradation of 125I proteins in plasma were investigated but did not appear to influence the adsorption results. The ability of polymers to fractionate plasma proteins and concentrate them at their surface is concluded to be a key factor in the complex processes which determine the compatibility of polymers in vivo.
Blood compatibility of hydrophilic polymers
Authors: Ikada Y. , Iwata H. , Horii F. , Matsunaga T. , Taniguchi M. , Suzuki M. , Taki W. , Yamagata S. , Yonekawa Y. , Handa H.
Published: December 2004

Blood compatibility has been studied for hydrophilic polymers such as poly(vinyl alcohol) (PVA), its derivative, and polyethylene grafted with water‐soluble monomers. The surfaces in contact with electrolyte solutions have been characterized by measuring the zeta potentials. The study of plasma protein adsorption on these polymers has revealed that bovine serum albumin as well as bovine serum fibrinogen adsorbs to a lesser extent as the hydrophilicity of the polymers increases. Platelet deposition and fibrin formation, examined using platelet‐rich plasma, have been found to take place less significantly on PVA as well as sodium acrylate‐ and acrylamide‐grafted polyethylene than on nongrafted and acrylic acid‐grafted polyethylene. Ex vivo experiments with canine whole blood have shown that formation of thrombus on PVA is less than on siliconized glass but increases upon heat treatment which reduces the hydrophilicity. When PVA tubes of about 1 mm diameter are anastomosed to the carotid artery of rat, the patency rate is found to depend strongly on the anastomotic technique. From the results on the zeta potential and the experiments in vitro and ex vivo it can be concluded that the material having a surface from which solvated, neutral chains are extended into the outer aqueous phase may exhibit excellent resistance to thrombus formation.
The effect of carbon fiber reinforcement on contact area, contact pressure, and time‐dependent deformation in polyethylene tibial components
Authors: Wright T. M. , Fukubayashi T. , Burstein A. H.
Published: December 2004

To study the mechanical behavior of a commercially available UHMWPE reinforced with carbon fibers, measurements of contact area, contact pressure and time‐dependent deformation were made on tibial components from a contemporary total knee replacement loaded to physiological levels. For comparison, similar measurements were performed on identical components manufactured from plain UHMWPE. Contact area and pressure results reflected the increased stiffness of the carbon‐UHMWPE material, with smaller contact areas and generally higher contact pressures versus the plain UHMWPE at the same load. Stresses in both materials under the contact area approached or exceeded the yield stresses for the materials when the physiological load was high or the radius of the femoral component indenter decreased (similar to flexion of the knee). Time‐dependent deformation over a 24 h period was reduced significantly in the carbon‐UHMWPE components for a high physiological load.
Investigations on the galvanic corrosion of multialloy total hip prostheses
Authors: Lucas L. C. , Buchanan R. A. , Lemons J. E.
Published: December 2004

Total hip prostheses combining cobalt and titanium alloys in direct physical contact are currently being used. The purpose of this paper was to investigate the possibility of an accelerated corrosion occurring due to the coupling of these alloys. Electrochemical corrosion studies based on mixed potential and protection potential theories were used to study thein vitroeffects of coupling the titanium and cobalt alloys. Verification of these studies was made by direct coupling experiments. Macroscopic examination of surface features of four retrieved total hip prostheses ranging from 0–6 years implantation were conducted. The electrochemical studies predicted coupled corrosion potentials of ‐0.22 V and low coupled corrosion rates of 0.02 μA/cm2. Direct coupling experiments verified these results. Cobalt‐titanium interfaces on the implants were macroscopically examined, and no instances of extensive corrosion were found. Overall, thein vitrocorrosion studies and the examination of retrieved prostheses predicted no exaggeratedin vivocorrosion due to the coupling of these cobalt and titanium alloys.
Determination of partition coefficients of acrylates, methacrylates, and vinyl monomers using high performance liquid chromatography (HPLC)
Authors: Fujisawa Seiichiro , Masuhara Eiichi
Published: December 2004

Retention times (Rt) for acrylates, methacrylates, and vinyl monomers were measured with two different columns (C18 Corasil and C8 LiChrosorb) using reverse‐phase HPLC in order to obtain their partition coefficients between 1‐octanol and water (log P). The log P values of test compounds were determined from the regression curves between RT and log P values of a number of standards using C8 LiChrosorb. The log P values obtained in this manner agreed closely with the log P values observed in previous studies. However, the peaks of these compounds were not sharp and some compounds were eluted for more than 10 min. Thus, the measurement of accurate Rt values is tedious. C18 Corasil was therefore used for this experiment in a mobile phase (methanol : water = 85 : 15). The Rt of some methacrylates with P values over 4 were delayed due to the hydrophobic interaction between these compounds and the C18 packing material. However, in the measurable region of the log P values (about −1 to +4), log P correlated linearly with log Rt following two different regression curves: one for aliphatic and aromatic compounds with the functional groups (r = 0.92), and the other for compounds without these groups (r = 0.99). It is concluded that log P values of methacrylates widely used in dentistry can be determined easily and accurately by HPLC.
Anticoagulant activity of a synthetic heparinoid in relation to molecular weight and N‐sulfate content
Authors: Sederel L. C. , van Der Does L. , van Duijl J. F. , Beugeling T. , Bantjes A.
Published: December 2004

Addition of chlorosulfonyl isocyanate to CC bonds in cis‐1,4‐polyisoprene and reaction of the adduct with NaOH resulted in the formation of a water‐soluble polyelectrolyte with N‐sulfate and carboxylate groups. The polyelectrolyte showed anticoagulant activity and it was found, just as with heparin, that the activity was related to molecular weight and N‐sulfate content.
Effect of age on the creep of a high‐copper amalgam
Authors: Mahler David B. , Nelson Lyle W.
Published: December 2004

A previous study of the effect of final Hg content on the static creep of a single‐composition high‐Cu amalgam alloy showed a sudden increase or jump in creep at a specific Hg content, and the presence of the SnHg phase (γ2) at final Hg contents subsequent to this creep jump. This observation is consistent with the less‐than‐optimum clinical performance reported for this alloy. A repetition of these tests conducted on test specimens 3 months and 6 months of age showed the creep jump to shift to higher Hg contents. However, even at 6 months of age, the final Hg content to be expected in clinical restorations was still positioned after the initiation of the creep jump where a small amount of γ2 is known to be present.
Organic surface film contamination of Vitallium implants
Authors: Malcolm Carter J. , Flynn Harry E. , Meenaghan Michael A. , Natiella Joseph R. , Akers Charles K. , Baier Robert E.
Published: December 2004

Conventional finishing and polishing techniques used to prepare Vitallium subperiosteal dental implant castings were found to produce low energy surfaces as measured by critical surface tension. Standard metallographic preparation gave slightly higher values. Glow discharge cleaning of both types of polished surface gave much higher critical surface tension values. This suggests the presence of an organic film after surface polishing of the implant which may later affect tissue reaction, in particular attachment, as has been noticed in related animal studies.
Crevice and fretting corrosion of stainless‐steel plates and screws
Authors: Brown S. A. , Simpson J. P.
Published: December 2004

Mechanisms of corrosion at the areas of contact between screw heads and plate holes were investigated using electrochemical potential recording techniques. Static crevice corrosion was studied with plates and screws in isotonic and hypertonic saline solutions (0.9 to 7.2% NaCl). Fretting corrosion was studied in vitro with plates screwed to tubular bone analogs which were subjected to cyclic axial loads, and was studied in vivo with plates screwed on the tibia of sheep. Static tests showed that crevice corrosion does not occur in isotonic saline for periods up to one year, but can occur in hypertonic saline solutions. Dynamic loading tests demonstrated immediate potential changes which were related to the magnitude of the applied load, indicating fretting corrosion due to motion between screw head and plate, both in vitro and in vivo. A mechanism for screw‐plate relative motion is proposed. It is hypothesized that corrosion seen in clinically retrieved implants due to fretting corrosion which predisposes the contact area to crevice corrosion attack.
The influence of implant elastic modulus on the stress distribution around LTI carbon and aluminum oxide dental implants
Authors: Cook S. D. , Klawitter J. J. , Weinstein A. M.
Published: December 2004

A three‐dimensional finite element analysis (FEA) has been used to determine the effect of implant elastic modulus on stresses in tissues around LTI carbon and aluminium oxide dental implants. The finite element model was constructed to represent a baboon mandible containing a blade type dental implant. A three unit fixed bridge was modeled connecting the dental implant to a natural molar. The results of the study indicate that stress levels of approximately a factor of 3 lower in the crestal region can be expected for aluminum oxide implants when compared to the LTI carbon implants. It was also observed that the use of LTI carbon and aluminium oxide dental implants as an abutment in a fixed bridge results in a reduction of stresses in tissues around the natural tooth when compared to normal physiological stress levels.
The role of the fibrous capsule in the function of implanted drug‐polymer sustained release systems
Authors: Anderson J. M. , Niven H. , Pelagalli J. , Olanoff L. S. , Jones R. D.
Published: December 2004

Numerous studies have been carried out on drug‐polymer sustained release systems designed for implantation. The majority of these efforts have been directed toward determining the in‐vitro rate of drug release from specific systems or drug polymer combinations and the in‐vivo studies have attempted to utilize analysis of the blood serum and excretory products as a measure of the release rate and behavior. To gain a better understanding of the influence of the local tissue environment and implant site on release behavior, we have investigated the release behavior of a gentamicin‐silicone rubber system implanted in canines. Particular attention has been directed toward investigating the role that the fibrous capsule which eventually surrounds the implant plays in determining the rate and pattern of drug release. The drug burst effect was decreased by the use of a drug‐free silicone rubber membrane on the gentamicin‐silicone rod implant. Analysis for gentamicin in the tissue adjacent to the implant for periods up to four weeks indicated that the release rate was retarded by the development of the fibrous capsule. The temporal and spatial variations in gentamicin levels in the tissue surrounding the rod implants were determined. In addition, the influence of implant coating and gentamicin loading level in the implant on local tissue concentrations with time were also investigated. These studies provide evidence that the fibrous capsule surrounding a drug‐polymer sustained release implant may influence the release behavior of the drug in an avantageous or disadvantageous manner depending upon the desired function of the sustained release system.
A quantitative microassay for in‐vitro toxicity testing of biomaterials
Authors: Ulreich Judith B. , Chvapil Milos
Published: December 2004

A quantitative tissue culture method is described for toxicity testing of biomaterials. The material to be evaluated, or in the case of insoluble materials—an extract of the material, is incubated on a monolayer of fibroblasts in 24 well culture plates. The activity of the fibroblasts is ascertained by measuring the rate of mitosis (3H‐thymidine incorporation), the synthesis of glycosaminoglycans (35SO incorporation) or production of total protein (3H‐tryptophan incorporation). By proper choice of label, the effect of the biomaterial on cellular proliferation or production of macromolecules or both may be assessed. Materials with a cytotoxic effect cause inhibition of incorporation of radioactive label in the above assays. The cell monolayers can also be inspected microscopically for evidence of cytotoxicity. The method is quantitative, simple, reproducible, rapid, and suitable for screening of a large number of samples.
Novel mode of contraception using polymeric hydrogels. I
Authors: Singh Harpal , Vasudevan Padma , Misro Manmohan , Ray Alok R. , Guha Sujoy K.
Published: December 2004

A new method of fertility control has been proposed and tested. The technique involves the use of the polymer, which when injected into the vas deferens lowers the pH sufficiently so as to kill the spermatozoa passing through. The polymer provides an acidic environment for a prolonged time and slowly erodes. The fertility may be restored after complete solubility of the polymer itself over a period of time or by flushing it with a suitable solvent. This method of male contraception is nonsurgical, nonocclusive, and reversible.
Permeability of heparinized hydrophilic polymer (H‐RSD): Application to semipermeable membrane for microencapsulation of activated charcoal
Authors: Mori Yuichi , Nagaoka Shoji , Tanzawa Hiroshi , Kikuchi Tetsuya , Yamada Yosuke , Hagiwara Masaru , Idezuki Yasuo
Published: December 2004

A series of heparinized hydrophilic polymers (H‐RSD) composed of a hydrophobic element, a nonionic hydrophilic element, a cationic element and ionically bound heparin was synthesized. The permeability of the H‐RSD polymers with various chemical compositions and water contents was investigated. From the studies on the permeability, it has been found that in order to maintain good permeability after heparinization, the nonionic hydrophilic element is necessary. In addition, the microencapsulation of activated charcoal granules using a H‐RSD polymer with a similar permeability to that of Cuprophan was examined. In vitro adsorption studies and in vivo direct hemoperfusion studies on the activated charcoal microencapsulated with the H‐RSD polymer, show that the H‐RSD coating prevents clot formation without loss of the absorption power of the activated charcoal.
Hemostatic and healing studies of sodium amylose succinate (IP760)
Authors: Jeffery Diane L. , Dressler Donald P. , Anderson James M. , Gallagher Michael J.
Published: December 2004

Acute and chronic studies were performed in the canine model to evaluate a new topical hemostatic agent in terms of initial hemostatic capability and tissue/material interaction during the healing process. IP760, a porous amylose succinate material, was applied to large spenic surface wounds in six acute and twelve chronic animals. Microfibrillar collagen (Avitene) was used in twelve chronic animals for comparison. While the hemostatic capabilities of the two agents were comparable, marked differences were noted in the healing response. In the IP760‐treated wound sites the acute inflammatory response, granulation tissue infiltration with fibrosis and healing occurred earlier and in a more homogeneous manner than in the Avitene‐treated wound sites. Healing of the IP760‐treated wounds occurred concomitantly with the development of granulation tissue and fibrosis and the rapid resorption of the IP760.
Phase identification and incipient melting in a cast Co‐Cr surgical implant alloy
Authors: Kilner T. , Pilliar R. M. , Weatherly G. C. , Allibert C.
Published: December 2004

Phase relationships in cast CoCr surgical implant alloys, heat treated at temperatures from 1180 to 1300°C, are reported. Interdendritic material was identified by selected area diffraction as a quaternary near eutectic mixture between sigma phase, M23C6, M7C3, and fcc Co. Incipient melting and subsequent resolidification of this near‐eutectic mixture accounts for observations of behavior at temperatures above 1235°C. At temperatures just below its melting point the interdendritic material initially breaks down to M23C6, which subsequently dissolves in the Co matrix.
The biocompatibility of polypyrrolidone in test implantation
Authors: Šprincl L. , Kušková M. , Roda J. , Králíček J.
Published: December 2004

The biological compatibility of polypyrrolidone was investigated using subcutaneous implantation in rats. Acute (10 days) and chronic (360 days after implantation) tissue reaction was characterized numerically and compared with poly(2‐hydroxyethyl methacrylate), used in the Drug Control Research Institute in Prague as a standard in the evaluation of polymers, for which good tolerance in the clinical practice has been demonstrated. Surface changes in the polymer were evaluated by using a scanning electron microscope.
The effect of pH on the in vitro degradation of poly(glycolide lactide) copolymer absorbable sutures
Authors: Chu C. C.
Published: December 2004

The pH effect on the hydrolytic degradation of Polyglactin 910 copolymer was studied in terms of the tensile properties of the suture specimens. The use of a cord/yarn grip, newly designed specifically for fibrous materials, eliminated the grip‐induced failure. Different degrees of hydrolytic degradation of this copolymer at 3 different pH levels were observed. The suture specimens exhibited the best retentions of breaking strength at the physiological pH of 7.44, while the specimens at pH = 10.09 showed the fastest loss of breaking strength. Thus, a maximum retention of tensile properties occurred around the pH level of 7.0, whereas smaller percentages of retention of tensile properties were observed at both acidic and strong alkaline solutions. This synthetic absorbable suture material exhibits the basic characteristic of hydrolysis which is catalyzed by both acid and base.
The effects of proteins on metallic corrosion
Authors: Clark G. C. F. , Williams D. F.
Published: December 2004

The corrosion of the pure metals aluminium, cobalt, copper, chromium, molybdenum, nickel, and titanium and of a cobalt‐chromium molybdenum casting alloy has been studied in buffered saline with and without the presence of the proteins serum albumin and fibrinogen. The corrosion of aluminium and titanium was unaffected by the protein. The corrosion rates of chromium and nickel showed a slight increase, while cobalt and copper dissolved to a very much greater extent in the presence of protein. However, with molybdenum the corrosion was inhibited by protein.
The education of the biomaterialist: Report of a survey, 1980–81
Authors: Black Jonathan
Published: December 2004

Biomaterials as a class includes a wide variety of both artificial and natural materials. The discipline of Biomaterials must be recognized as the study of the materials aspects of both fabricated materials and natural tissues, as well as their interactions. Emerging disciplines give rise to academic establishments. A survey of 97 U.S. and Canadian universities reveals a wide range in institutional settings and course offerings in Biomaterials. Plans for faculty additions suggest that the field is still actively expanding.
The effect of oxidation of copoly(L‐alanine, L‐methionine) membranes on oxygen permeability and tensile properties
Authors: Aiba Sei‐ichi , Minoura Norihiko , Fujiwara Yukihiko
Published: December 2004

This study pertains to the development of poly(α‐amino acid) membranes which have potential as biomaterials. Copoly(L‐alanine, L‐methionine) membranes have been subjected to oxidation which produced a hydrophilic structure allowing the improvement of oxygen permeability. L‐Methionine residues in the copolymers were converted to methionine sulfoxide and/or sulfone groups by action of hydrogen peroxide in various reaction compositions. Water absorption, permeability to oxygen dissolved in water, and tensile strength of the modified membranes were changed with the extent of oxidation. The water absorption was found to increase with oxidation time from 10 to 300%. The oxidation time dependency on the oxygen permeability coincided with the increase in the water absorption. The permeability coefficients of oxidized membranes were of the order of 10−9 cm3 (STP) cm/cm2 s cm Hg, while those of unoxidized membranes were approximately 10−11. As expected, the tensile strengths of oxidized membranes were smaller than those of unoxidized ones. In addition, the effect of L‐alanine and L‐methionine residue composition on the membrane properties is discussed.
The viscosity of acrylic bone cements
Authors: Krause William R. , Miller Jo , Ng Philip
Published: December 2004

The viscosity of the acrylic bone cement used in total joint arthroplasty is an important material property for determination of the proper handling characteristics and interlock with bone. In this article the rheological properties of the three leading bone cements were determined over a three‐decade range of shear rates. In addition, four other cements were tested at a single shear rate. The results indicate that all the acrylic bone cements are non‐Newtonian, pseudoplastic materials with significant differences between them. It is shown that the viscosity increases at different rates with respect to increases in time. For the majority of cements there is a steady or increasing rate of viscosity change with time.
Considerations on manufacturing principles of a synthetic burn dressing: A review
Authors: Chvapil Milos
Published: December 2004

This review presents various considerations on the construction of a synthetic burn dressing, based mainly on collagen protein. Membranous wound covers are compared with sponge‐felt types, monocomponental with composite. The importance of collagen crosslinking agent and the nonextractibility of any component from the dressing material are discussed. According to the type of the burn the dressing should be used dry or wet, plain or medicated, and changed often to reduce substantially the presence of necrotic tissue, inflammatory cells of the granulation tissue, and bacterial contamination.
The evaluation of new dental resins prepared with polyfunctional methacrylate monomers
Authors: Suzuki Shiro , Nakabayashi Nobuo , Masuhara Eiichi
Published: December 2004

The combinations of several composite fillers and dimethacrylates for crown and bridge resins were investigated. The composite filler prepared from TMPT markedly improved the mechanical and physical properties of crown and bridge resins. The enhancement of the mechanical and physical properties is due to the highly crosslinked structure which is developed with the use of the reactive composite filler which copolymerizes with the matrix monomer. The combination of the 2.6E‐UDMA comonomer and the TMPT composite filler exhibited the maximum compressive strength, transverse strength, and Brinell hardness, and minimum abrasion loss and thermal expansion. This hard resin was superior to the resins currently available for clinical use.
Sulfonated poly(vinylidene fluoride) as a biomaterial: Immobilization of urokinase and biocompatibility
Authors: Aoshima R. , Kanda Y. , Takada A. , Yamashita A.
Published: December 2004

The adsorption of urokinase (UK) on sulfonated poly(vinylidene fluoride) (PVDF) films was examined. The amount of adsorbed UK on sulfonated PVDF films increased linearly with the degree of the ion exchange capacity (IEC) of sulfonated film. Moderately sulfonated PVDF film (IEC = 0.25 meq/g) adsorbed 3 IU/cm2 UK, and highly sulfonated film (IEC = 0.54 meq/g) adsorbed 5 IU/cm2 UK. All UK‐immobilized PVDF films were active for ten weeks. The presence of the sulfonated films in the culture of rat lymphocytes did not result in any change of their viability. The implant of the film (IEC > 0.48 meq/g) into the subcutaneous layer of rats resulted in the cell infiltration composed of lymphocytes and plasma cells or the blastogenesis within the surrounding tissues of the implant and the regional lymph nodes. On the contrary, the implant of the films (IEC < 0.27 meq/g) did not exert any visible changes, indicating that the lightly sulfonated films may be applicable in the sense of biocompatibility in vivo.
Polyphosphazenes: Effect of molecular motions on thrombogenesis
Authors: Reichert W. M. , Filisko F. E. , Barenberg S. A.
Published: December 2004

The effect and interrelationship between primary (segmental backbone) and secondary (side chain) molecular motions on thrombogenesis, independent of morphological order/disorder, crystallinity, and/or associated water is elucidated using an amorphous hydrophobic polymer of poly‐[(trifluoroethoxy) (fluoroalkoxy)phosphazene], PNF. The results indicate that thrombogenesis for an amorphous hydrophobic polymer is sensitive and dependent on the degrees and types of primary and secondary molecular motions at the polymer interface.
Rheological studies of the polymerization of elastomeric impression materials. I. Network structure of the set state
Authors: Cook Wayne D.
Published: December 2004

As part of the detailed study of the curing of a range of dental elastomeric impression materials, their chemistry was investigated. This information, the dependence of the stress relaxation modulus of the set material on the catalyst/base ratios, and the level of diluent were used to elucidate the network structure. Such information is required before the rheological behavior during cure can be understood. The clinical significance of the recommended catalyst/base ratio is discussed.
Application of immunoperoxidase method to electron microscopic observation of plasma protein on polymer surface
Authors: Noishiki Yasuharu
Published: December 2004

The immunoperoxidase technique was applied to observe the electron microscopic presence of human plasma protein on a polymer surface. Two types of polymer material, i.e., Dacron and a newly synthesized heparinized hydrophilic polymer (H‐RSD, Toray Industries, Inc.), showed different reactions to human plasma proteins. The hydrophobic Dacron showed a decreased affinity for plasma albumin, but a greater affinity for fibrinogen, α1‐lipo‐protein, and β‐lipoprotein when compared to H‐RSD. The thrombo‐resistant H‐RSD showed a relatively strong affinity for albumin, but in a spotty or focal manner. Most of the H‐RSD surface did not adsorb albumin. Fibrinogen adsorption was observed in areas smaller than albumin adsorption. The adsorption of fibrinogen appeared to occur through certain material. The α‐lipoprotein and β‐lipoprotein were not adsorbed on the H‐RSD. The immunoperoxidase method is a sensitive and useful technique in studying the interactions between plasma proteins and the surface of polymer materials.
Blood–materials interactions: The minimum interfacial free energy and the optimum polar/apolar ratio hypotheses
Authors: Coleman D. L. , Gregonis D. E. , Andrade J. D.
Published: December 2004

Numerous hypotheses exist to explain observed blood–materials interactions. It is the purpose of this article to test two popular hypotheses, namely, the minimum interfacial free energy hypothesis and the optimum polar/apolar ratio hypothesis. Methacrylate polymers and copolymers were characterized using the captive bubble underwater contact angle method; bulk water content was determined by gravimetric methods; streaming potential measurements were made; and surface roughness and possible particulate contamination were evaluated by reflected light microscopy. In vitro blood tests include whole blood clotting time measurements on polymer‐coated tubes; centrifugal force platelet adhesion on polymer‐coated coverslips; and a measure of the partial thromboplastin time, Russell's viper venom time (Stypven time), and the prothrombin time of native whole blood exposed to polymer‐coated microscope slides. Results suggest that platelet adhesion correlates in the opposite direction of whole blood clotting time and partial thromboplastin time, emphasizing the need for a multiparameter approach to blood–materials testing. Based on these tests the minimum interfacial free energy hypothesis is not supported. In fact, the data suggest the opposite to be true. It is apparent that platelet adhesion can be a misleading indicator of blood compatibility. Neither hypotheses can explain the apparent conflict between the platelet adhesion data and the coagulation time data.
Analysis of retrieved implants: Crystallinity changes in ultrahigh molecular weight polyethylene
Authors: Grood Edward S. , Shastri Ranganath , Hopson Clark N.
Published: December 2004

The extent of in vivo induced structural alterations were evaluated in 13 retrieved implants ranging from two weeks' to seven years' implantation. A statistically signifiant difference in crystallinity was seen between weight‐bearing and non‐weight‐bearing region, regions of the implants. Further, in the weight‐bearing region, crystallinity was higher in components implanted for two or more years than in those implanted for less than one‐half year. These results were consistent with our prior in vitro study on the effects of sterilization and aging. Taken together, the data indicate that UHMW polyethylene is not a static material but is continually undergoing dynamic changes in vivo.
Intramedullary fixation of artificial hip joints with bone cement‐precoated implants. I. Interfacial strengths
Authors: Barb W. , Park J. B. , Kenner G. H. , von Recum A. F.
Published: December 2004

In order to minimize the problems associated with implant fixation using acrylic bone cement, a new technique has been investigated. Canine hip prostheses were precoated with self‐curing acrylic bone cement and implanted in random source dogs using the same cement for fixation, a precoated prosthesis on one side and an uncoated (control) on the other. After 1, 3, and 6 months, both femora were excised and sectioned for mechanical assessment of the interfaces among bone, cement, and implant. It was found that the precoated implants had much higher interfacial shear strengths than the uncoated ones (average 14.2 and 6.8 MPa for implant‐cement interface; 2.0 and 1.2 MPa for the cement‐bone interface for all implant periods). The precoated “old” cement and the “new” cement's interfacial shear strength was the strongest with an average of 15.1 MPa for all implant periods. The present results indicate that the precoated hemiarthroplastic implants provide a firmer intramedullary fixation than the traditional, uncoated implants.
Ex vivo shunt testing of hydrogel–silicone rubber composite materials
Authors: Vale Bradley H. , Greer Raymond T.
Published: December 2004

Hydrogel polymers consisting of HEMA (2‐hydroxyethyl methacrylate) alone or copolymerized with NVP N‐(vinyl pyrrolidone) were incorporated into silicone rubber tubing to produce hydrophilic composite materials. Polymerization methods of the interpenetrating network (IPN) and radiation‐induced type were used to impregnate the silicone rubber substrates. These methods produced materials with varied wettability (contact angle with water ranged from 57° to 95°) but similar texture. The surface morphology as observed in the scanning electron microscope was the same for all the materials. Four types of composite materials and two sizes of silicone rubber control tubing in a total of 19 dogs were used as ex vivo femoral artery‐to‐vein (A–V) shunts and were sampled at 5, 15, 30, 45, and 60 min. Data obtained by using scanning electron microscopy (SEM) were used to determine the type and amount of adhering blood cells at the time intervals described. Large platelet aggregates and/or a variable initial response were found to be predictors of shunt failure (occlusion). Most samples showed only varied levels of platelet adhesion, but other cell types were seen in some samples. The adhesion was found to peak in all cases by 30 min and to reach lower levels by 60 min, suggesting that an initial phase of reaction was complete. The course of platelet adhesion for a 60‐min period is presented.
A comparison of the in vitro cytotoxicity of four restorative materials assessed by changes in enzyme levels in two cell types
Authors: Meryon S. D. , Riches D. W. H.
Published: December 2004

A system is described for assessing the toxicity of freshly mixed restorative materials in vitro by measuring changes in the levels of β‐galactosidase and lactic dehydrogenase in both cultured cells and supernatants. The toxic effects of a zinc phosphate and silicate cement, a composite, and zinc oxide/eugenol were studied on two cell types, macrophages and fibroblasts, after 24 h exposure. Zinc oxide/eugenol, Silicap, and zinc phosphate were toxic to macrophages, in that order; Concise appeared to be nontoxic. Only zinc oxide/eugenol exerted significant effects on fibroblasts. Interposing dentine powder between the test cells and the material ameliorated the effects of all materials, possibly by the absorption of toxic components.