bluuebunny/crossref_metadata_2025 huggingface dataset:
The effect of HIPing on the fatigue and tensile strength of a cast, porous‐coated CoCrMo alloy
Authors: Georgette F. S. , Davidson J. A.
Published: December 2004

The process required to sinter porous CoCrMo alloys results in the formation of substrate porosity through carbide dissolution. Since hot isostatic pressing (HIPing) has been shown to eliminate casting porosity in the CoCrMo alloy, it is possible that it may be equally effective on pores that are generated from the sintering operation. The effect that HIPing a porous‐coated CoCrMo material has on the fatigue and tensile properties was investigated. Fatigue testing was performed on sintered materials as well as sintered and HIPed materials, both with and without a porous coating. Further, the effect of varying coating thickness on the resulting fatigue strength of sintered and HIPed materials was studied. Light microscopy was performed in order to define the microstructural changes brought about by the various thermal cycles. Scanning electron microscopy was utilized to define the crack initiation process. The fatigue strength of uncoated “as sintered” materials was found to be reduced by 34% relative to the “as cast” condition. The same material that was HIPed revealed a fatigue strength slightly lower than the “as cast” condition. It was found that porous coatings created preferential sites for fatigue crack initiation. However, the presence of the coating did not further reduce the fatigue strength of “as sintered” materials because of the already low strength created by the sintering operation. Materials that were sintered exhibited a lowering in both tensile strength and elongation to failure relative to the “as cast” condition. The HIPing of sintered materials improved both fatigue and tensile properties relative to the “as sintered” condition.
Histopathologic evaluation following chronic implantation of chromium and steel based metal alloys in the rabbit central nervous system
Authors: Rauch Helene C. , Ekstrom Merlin E. , Montgomery Ilene N. , Parada Frank , Berke Joseph
Published: December 2004

Histopathologic evaluation of three metal alloys for chronic implanatation in the central nervous system (CNS) was undertaken in rabbits. Throughout the 8 month evaluation period the inflammatory response to the alloys was bland. Two of the alloys tested (chromium based MP35N, Trademark of the Standard Pressed Steel Company, and a stainless steel alloy, BG42 VacArc, Trademark of Latrobe Steel) appeared suitable as CNS implants. The third alloy (stainless steel 440C, Carpenter Steel Company) showed more corrosion than the other alloys, and may be less suitable for implantation. While E. cuniculi infection was found in four rabbits, the infection did not directly interfere with the assessment of the histologic changes directly due to the implants. Autoantibodies to a brain constituent were not observed.
Bone bonding behavior of three kinds of apatite containing glass ceramics
Authors: Kitsugi Toshiaki , Yamamuro Takao , Nakamura Takashi , Higashi Shoichiro , Kakutani Yoshiaki , Hyakuna Katsufumi , Ito Setsuro , Kokubo Tadashi , Takagi Masataka , Shibuya Takehiro
Published: December 2004

We have produced three kinds of apatite‐containing glass ceramics of the same chemical composition: MgO (4.6), CaO (44.9), SiO2 (34.2), P2O5 (16.3), CaF2 (0.5) (in weight ratio). They contain different crystal combinations and have different mechanical properties.

The first glass ceramic (A–;GC) was prepared by heating a glass plate to 870°C. It contains only oxy‐ and fluoroapatite (35 wt%). The second glass ceramic (A–W–GC), and the third (A–W–CP–GC), were prepared by heating glass powder compacts to 1050°C and 1200°C, respectively. A–W–GC contains oxyapatite and fluoroapatite (Ca10(PO4)6(O,F2)) (35 wt%) and β‐wollastonite (40 wt%). A–W–CP–GC contains oxyapatite and fluoroapatite (20 wt%), β‐wollastonite (CaO·SiO2) (55 wt%), and β‐whitlockite (3CaO·P2O5) (15 wt%). The bending strengths of A–;GC, A–W–GC, and A–W–CP–GC were 88MPa, 178MPa, and 213MPa, respectively, in air.

Rectangular ceramic plates (15mm × 10mm × 2mm) were implanted into a rabbit tibia. Ten and 25 weeks after implantation, the segment of tibia with implant was excised for examination. The segment was held by a special jig and the traction breaking load (failure load) was measured by an autograph.

A–;GC showed a lower load than A–W–GC and A–W–CP–GC. The loads for A–W–GC and A–W–CP–GC were almost equal. The failure loads did not change significantly between 10 and 25 weeks for any of the materials.

The interface was examined by Giemsa surface staining, contact micro‐radiography, and SEM‐EPMA. Giemsa surface staining and CMR revealed direct bonding between the materials and the bone for all the three materials.

SEM‐EPMA showed that Si and Mg content decreased, Ca content did not change, and P content increased at the reaction zone between all three glass ceramics and bone. This was observed at 10 weeks, as well as at 25 weeks, after implantation. The reaction zone was narrowest with A–;GC, wider with A–W–GC, and widest with A–W–CP–GC.
A histologic and mechanical evaluation of carbon‐coated polyester suture
Authors: Cook Stephen D. , Kester Marcus A. , Brunet Michael E. , French H. Graeme , Haddad Ray J. , Haubold Axel D.
Published: December 2004

Ultra low temperature isotropic (ULTI) carbon‐coated polyester suture material was evaluated histologically and mechanically in dogs. These results were compared to those obtainedfor uncoated polyester and polybutylate coated polyester. The suture materials were used in therepair of the surgically incised medical collateral ligament and subcutaneous tissues to evaluate the potential of the carbon‐coated system for ligamentous repairs. Following surgery, the dogs were sacrificed at periods of 1–48 weeks postoperatively for evaluation of tissue biocompatibility and mechanical strength of the materials. The polybutylate‐coated polyester suture broke at lower force levels than did comparable sizes of uncoated or carbon‐coated polyester. All three types showed a high retention (>98%) of mechanical strength at 48weeks, often exhibiting an increase in tensile strength due to tissue ingrowth. The histologic response to carbon‐coated polyester was equal to or better than the response to either the uncoated polyester or polybutylate‐coated polyester. A greater degree of tissue growth into the carbon‐coated material was evident at most time periods following an initial acute inflammatory response which was also present in the other materials.
Evaluation of the in vitro and ex vivo blood compatibility of primary reference materials
Authors: Pelzer H. , Heimburger N.
Published: December 2004

The blood compatibility of the primary reference materials, low density polyethylene and polydimethylsiloxane, was evaluated using human in vitro and human ex vivo test devices, and was compared with that of polyetherurethane and polyvinylchloride. The effect of the materials on in vitro platelet activation was studied by measurement of platelet factor 4 release by enzyme immunoassay. The adsorption of fibrinogen and platelets from human native blood onto the surface of the material was measured using enzyme immunoassay technique. The four materials tested exhibited significantly different effects on in vitro platelet activation. In addition, the materials adsorbed fibrinogen and platelets to a different extent under ex vivo test conditions. Materials, which induced strong in vitro platelet activation, e.g. low density polyethylene and polyvinylchloride, demonstrated high concentrations of fibrinogen and platelets on the surface when tested under ex vivo conditions. Polydimethylsiloxane and polyetherurethane, which induced slight in vitro platelet factor 4 release, adsorbed significantly lower concentrations of fibrinogen and platelets from human native blood.
Growth of bone marrow cells on porous ceramics in vitro
Authors: Uchida Atsumasa , Nade Sydney , McCartney Eric , Ching William
Published: December 2004

Following the transplantation of bone marrow cells to extra‐osseous sites, bone formation occurs in those sites. This osteogenic potential of bone marrow cells might be utilized for filling defects in bone if they could be transported on porous ceramic materials. Before such an approach becomes feasible, it is important to know what happens to the cells in the presence of the ceramics that might be used. In order to investigate the interaction between bone marrow cells and ceramics, in vitro, a system for culturing bone marrow cells on ceramic materials has been developed. Bone marrow cells adhered well to the surface of calcium hydroxyapatite and tricalcium phosphate ceramics, and this was followed by the formation of fibrous tissue on and within the ceramics. These ceramics were compatible with bone marrow cells even in culture conditions in which there was a large surface area of ceramic interfacing with cells. The results support the proposal that calcium hydroxyapatite and tricalcium phosphate are appropriate as bone replacement materials. In contrast, calcium aluminate had an adverse effect on bone marrow cells when there was a high proportion of ceramic to culture medium. However, this effect was not present if the proportion of ceramic to culture medium was low. Therefore, a large amount of biodegradable porous calcium aluminate ceramic should not be used as an alternative to autogeneous bone grafting.
Composites for use in posterior teeth: Composition and conversion
Authors: Ruyter Ivar Eystein , Øysæd Harry
Published: December 2004

The purpose of this investigation was to determine the composition, as well as the conversion after polymerization, of some dental composite materials. Eight posterior composites and two anterior composites were investigated. The weight and volume fractions of inorganic fillers were determined by combustion and pycnometric analyses. The monomers were analyzed qualitatively and quantitatively by high performance liquid chromatography, nuclear magnetic resonance spectroscopy, and gel permeation chromatography. Infrared multiple internal reflection spectroscopy was applied for determination of conversion of the methacrylate groups. The conversion in light activated materials was examined at shallow depths, that is, the level of optimal conversion. This investigation demonstrated that the conversion can be correlated with the composition of monomers and oligomers used in the materials.
Specific removal of paraquat by hemoperfusion through antiparaquat conjugated agarose‐polyacrolein microsphere beads
Authors: Azhari Rosa , Margel Shlomo , Labes Ari , Haviv Yolanta
Published: December 2004

A novel specific adsorbent for removal of paraquat from blood has been developed. Immobilized antiparaquat antibodies provide the specificity and high affinity of the adsorbent. The antibodies were raised in rabbits and goats immunized with an analogue of paraquat, conjugated to bovine serum albumin (BSA). Specific antiparaquat antibodies were isolated from the animals' sera by affinity chromatography. The antibodies were polyvalently bound to crosslinked agarose‐polyacrolein microsphere beads (APAMB). Antiparaquat conjugated beads (APB) were used as packing material in a hemoperfusion column for detoxification of paraquat and were compared to activated charcoal. In vitro and in vivo experiments showed specific and enhanced rate of removal of paraquat from plasma and blood by using APB. Minimal alteration of the formed elements and plasma constituents of the blood was observed.
Tissue biocompatibility of kevlar aramid fibers and polymethylmethacrylate, composites in rabbits
Authors: Henderson James D. , Mullarky Richard H. , Ryan Doreen E.
Published: December 2004

Two groups of female NZW rabbits were implanted in the paravertebral muscles with aramid (du Pont Kevlar aramid 49) fibers and aramid‐polymethylmethacrylate (PMMA) composites for 14 and 28 days. Rabbits were killed at these times periods, necropsies performed, sites scored for gross tissue response, and tissue specimens containing the implants removed for histopathological evaluation. A mild fibrous tissue reaction was observed around all implants containing aramid fiber similar to that observed around the silicone control implant. Some foreign body giant cells were also present adjacent to the fibers. An intense necrotic inflammatory reaction was present around the positive control material (PVC Y‐78). The tissue response to implantation of aramid fiber and fiber‐PMMA composites indicates that aramid is a biocompatible material.
125I‐fibrinogen uptake on peripheral venous cannulas: A comparison between different cannula materials and coatings
Authors: Lindblad Bengt , Johansson Arne
Published: December 2004

Using a similar technique as 125I‐Fibrinogen uptake test for detection of deep venous thrombi, the radioactivity over cannulas inserted into veins on the dorsal aspect of the hands was measured 1, 2, 4 and 24 h after insertion. In three groups of 10 postoperative patients it was by random allocation inserted on one side a siliconized tetrafluorethylene cannula and on the other side one of either: a nonsiliconized tetrafluorethylene, a heparinized tetrafluorethylene or a fluorethylenpropylene cannula. The same volume and type of infusion was given in both cannulas. No difference in protein deposition was seen between siliconized and nonsiliconized tetrafluorethylene. A tendency of lower protein deposition, especially at 24 h on heparinized tetrafluorethylene was found. The fluorethylenpropylene cannulas had both over cannula and adjacent vein higher protein deposition at all measurements compared to the siliconized tetrafluorethylene cannula (p < 0.01). The results implicate that fluorethylenprophylene could induce a higher incidence of thrombophlebitis than tetrafluorethylene cannulas.
Effect of the surface geometry of smooth and porous‐coated titanium alloy on the orientation of fibroblasts in vitro
Authors: Inoue T. , Cox J. E. , Pilliar R. M. , Melcher A. H.
Published: December 2004

The migration and orientation of human gingival fibroblasts in relation to the rim of smooth‐surfaced and porous‐coated titanium discs placed on multilayers in vitro was investigated. Samples were examined after 6 h, 24 h, 3 days, and 7 days of culture using phase‐contrast and scanning electron microscopy. The cells migrated from the multilayer onto the smooth‐surfaced discs forming bridges between them, and orientated along parallel circumferential grooves in the rim of the discs. This resulted in the cellular bridges orientating at an acute angle to the rim of the disc, and adjacent cells in the multilayer orientating parallel to the rim. Cellular bridges were also formed between the porous‐coated discs and the multilayer but, because the cells that migrated onto, and between, the spheres of the porous‐coat showed no preferred orientation, the bridges retained their orientation at right angles to the surface of the rim. This in turn resulted in the cells of the adjacent multilayer becoming similarly orientated. These observations suggest that the geometrical configuration of the surface of implants could influence whether a capsule or an orientated fibrous attachment is developed in relation to implants in vivo.
Localized prevention of postsurgical adhesion formation and reformation with oxidized regenerated cellulose
Authors: Shimanuki Takao , Nishimura Kazunori , Montz Fredrick J. , Nakamura Robert M. , Dizerega Gere S.
Published: December 2004

We evaluated oxidized regenerated cellulose (ORC) in experimental rabbit and dog models to assess its potential for reducing or preventing adhesion formation and reformation. Evaluation was performed in the following anatomical sites: (1) uterine horn trauma; (2) small bowel resection and anastomosis; (3) parietal peritoneum excision; and (4) adhesion reformation in the uterine horn. Ten to 14 days after ORC treatment, adhesion formation was macroscopically and microscopically evaluated. Results demonstrate that ORC produced graded reduction in adhesion formation and significantly prevented adhesion reformation.
Bone‐particle‐impregnated bone cement: An in vitro study
Authors: Liu Y. K. , Park J. B. , Njus G. O. , Stienstra D.
Published: December 2004

Bone‐particle‐impregnated bone cement specimens (up to 30% by weight) were characterized by various test methods. The experimental bone cement showed decreased crack propagation rates and increased Young's modulus, while the ultimate tensile strength and impact strength were decreased. The viscosity could be adjusted by adding initiators lost when substituting the PMMA powder with bone particles. The present study warranted fur‐ther in vivo experiments on the possibility of tissue ingrowth for which the new bone cement was developed.
Luminal surface fabrication for cardiovascular prostheses
Authors: Deininger William D. , Gabriel Stephen B.
Published: December 2004

Methods to produce highly ordered, specific surface morphologies on polytetrafluoroethylene (PTFE Teflon) surfaces were developed. These methods included the use of photolithographic techniques for pattern definition and directed argon ion beam sputter etching to produce the desired surface morphology. Use of these techniques resulted in the formation of regular arrays of sharply defined hexagonal pillars with smooth, vertical walls with heights of up to 80 μm. Pillar height‐to‐width ratios ranged up to 5.2–1. Surface hole depths of up to approximately 80 μm were also obtained. These surface morphologies could have an important application in medicine for improving the patency of cardiovascular prostheses. This would be accomplished by creating a luminal surface in the implant which promotes the development of a healthy neointima lining.
In vitro and in vivo kinetics of regulated drug release from polymer matrices by oscillating magnetic fields
Authors: Edelman E. R. , Brown L. , Taylor J. , Langer R.
Published: December 2004

The kinetics of drug release from polymerdrug matrices containing an embedded magnet was continuously monitored in vitro and in vivo. The application of an oscillating magnetic field increased the rate of drug release from the polymer matrices. Within the limits of detection the increase in release occurred immediately, remained stable for as long as the field was applied, and returned exactly to baseline upon withdrawal of the field. The increase in release was directly proportional to field amplitude. The same pattern of results were observed in vivo as in vitro, though higher strength fields were required in vivo to achieve the same effect observed in vitro.
Wear‐accelerated corrosion of Ti‐6Al‐4V and nitrogen‐ion‐implanted Ti‐6Al‐4V: Mechanisms and influence of fixed‐stress magnitude
Authors: Buchanan R. A. , Rigney E. D. , Williams J. M.
Published: December 2004

Wear‐accelerated corrosion rates at constant anodic potentials were evaluated for unimplanted and nitrogen‐ion‐implanted surgical Ti‐6Al‐4V while wearing against ultrahigh‐molecular‐weight polyethylene at stress levels up to 6.90 MPa (1000 psi). The ion implantation processing was found to reduce the wear corrosion rates in both saline and serum solutions at all applied stress levels. During wear testing, all of the ion‐implanted surfaces remained visually unchanged from the polished condition. However, many of the unimplanted surfaces developed damage zones characterized by wear tracks and black wear debris. A surface‐damage mechanism is proposed and discussed which involves disruption of the Ti‐6Al‐4V protective oxide film, subsequent entrapment of oxide particles in the polyethylene, then self‐perpetuating damage due to the abrasive action of the embedded particles.
The effect of injection of powdered biomaterials on mouse peritoneal cell populations
Authors: Pizzoferrato A. , Vespucci A. , Ciapetti G. , Stea S. , Tarabusi C.
Published: December 2004

The authors suggest an experimental model for the assaying, before implantation, of the tissue reaction that wear particles from artificial joints can cause in the human body. Mice were intraperitoneally injected with biomaterial powders in suspension in saline. The materials used were chromium, chromium oxide, nickel, nickel oxide, aluminium, alumina, alumina‐titania, cobalt, molybdenum, titanium, silver, zirconium oxide, iron oxide, and stainless steel. Peritoneal lavage was performed a week after injection. A thorough morphological and quantitative analysis of the cell suspension thus obtained was made both immediately after collection and after a 24 h culture.
Surface characterization of heparin‐complexing poly(amido amine) chains grafted on polyurethane and glass surfaces
Authors: Barbucci Rolando , Baszkin Adam , Benvenuti Manuela , Costa Maria De Lourdes , Ferruti Paolo
Published: December 2004

Poly(amido‐amine) chains grafted onto polyurethanes and glass form stable complexes with heparin yielding potential nonthrombogenic surfaces. The characterization of the surfaces, and the product of each chemical reaction including final heparinized surfaces, has been studied by contact angle data and scanning electron microscopy (SEM). Air in water, octane in water, and drop‐on‐plate contact angle data were used to estimate surface (γsv) and interfacial (γsw) free energies. Solid–water work of adhesion (Wa) and its dispersive (W) and polar (I) components were calculated for all studied surfaces. It has been found that the viscosity of polyurethane solution used for film casting influences wetting properties of these films. It has also been found that a direct correlation exists between the I/W values and the degree of coverage of the surfaces by cellular deposits after their exposure to platelet‐rich plasma. Final heparinized polyurethane and glass materials are hydrophilic, their I/W ratio is high, and little or no cellular deposit is observed on their surfaces.
Tissue reactions to wear products from polyacetal (Delrin®) and UHMW polyethylene in total hip replacement
Authors: Mathiesen E. B. , Lindgren J. U. , Reinholt F. P. , Sudmann E.
Published: December 2004

The tissue reaction to implanted materials and their wear products is important for the long‐term fixation of a total hip replacement (THR). Recent reports indicate a relatively high incidence of aseptic loosening with Christiansen total hip prostheses. We examined tissue reactions to wear products in two groups of prostheses: (1) 16 Christiansen prostheses with polyacetal (Delrin) sockets, and (2) 18 Charnley‐Müller total hip prostheses with ultrahigh‐molecular‐weight polyethylene (UHMWP) sockets. Specimens from these 34 patients were compared in a combined qualitative and semiquantitative morphological study. We saw similar histological changes in specimens of both groups, but specimens from the bone–cement interfaces of the acetabulum and femur shaft in the polyacetal group showed more inflammation and necrosis.
A histological comparison of the tissue interface of bioglass and silica glass
Authors: Ito G. , Matsuda T. , Inoue N. , Kamegai T.
Published: December 2004

The objectives of the present article are to confirm the bone bonding phenomenon of Bioglass (BG) developed by Hench et al., and to observe the singularity of tissue reaction to it. BG and nonreactive silica glass (SG) were implanted in the femurs of rabbits and rats. Histological examination revealed that a relatively acellular zone with little inflammation was formed on BG surface at 1 day after implantation. Neither fibrous tissue nor a distinct boundary was observed between BG and bone after 7 days. On the contrary, a moderate post‐operative inflammatory reaction was observed on SG at 1 day, and fibrous tissue was observed between SG and bone after 7 days. From these findings, it was confirmed that BG bonded directly with bone. As the relatively acellular zone observed on BG surface at 1 day was replaced by bone after 7 days, the formation of this zone might play an important role in bone‐bonding process. Further research should be focused on the mechanism and biological meaning of bone bonding, for this phenomenon can not be explained by the conventional pathological theory of foreign body encapsulation.
Studies of poly(ether)urethane pacemaker lead insulation oxidation
Authors: Thoma R. J. , Phillips R. E.
Published: December 2004

Published reports suggest that silver ions may catalyze the oxidation of poly‐(ether)urethane soft‐segments resulting in the failure of urethane insulations of specific models of pacemaker leads. Attempted oxidation of soft‐segment models, poly‐(tetra‐methylene ether)glycols, by silver nitrate has shown that metal‐ion catalyzed oxidative‐reduction (MICOR) does not adequately explain observed failures unless antioxidants are removed in process. Such cracking can, however, be explained in terms of a metal ion enhanced environmental stress cracking.
In vitro and in vivo characterization of synthetic polymer/biopolymer composites
Authors: Gilbert Donna L. , Lyman Donald J.
Published: December 2004

Collagen, extracted from rat tail tendons using dilute acetic acid, was fabricated into films for subsequent characterization and biocompatibility testing. The reconstituted collagen was characterized with infrared spectroscopy, solution viscosity, contact angle, and tensile testing techniques and was found to be pure with molecular and physical properties consistent with findings of previous researchers. Composites composed of collagen coated on urethane and Silastic Rubber® films were fabricated to give improved tear resistance.

The biocompatibility of the composites and individual polymers was evaluated by discs implanted in the paravertebral muscle of rabbits. After four weeks none of the materials induced any gross changes in the muscle. Histopathological evaluation revealed a fibrous capsule around all of the materials. Collagen and collagen composites exhibited a stronger reaction as evidenced by a larger fibroblast layer and a variety of inflammatory cells, lymphocytes, eosinophils, and macrophages. The urethane was rated with a response index of 1.5 versus 3.25 for the urethane/collagen composite; Silastic Rubber® rated a response index of 1.67 versus 3.12 for the Silastic Rubber®/collagen composite; collagen rated a response index of 3.3. The polyester sutures also induced a reaction with a larger fibrous capsule but fewer inflammatory cells as compared to collagen and collagen composites.
The determination of Al, Cr, Co, Fe, and Ni in whole blood by electrothermal atomic absorption spectrophotometry
Authors: Lugowski S. , Smith D. C. , van Loon J. C.
Published: December 2004

Procedures for the determination of aluminum, chromium, cobalt, nickel, and iron in whole blood are presented and discussed. Chromium, cobalt, nickel, and iron were determined from one sample after decomposition of the blood with a mixture of nitric and perchloric acids. A graphite furnace was used for the determination of chromium, cobalt and nickel, and flame AAS was used for iron. The determination of Al was done from separate samples by GFAAS after dilution with 1% Triton TX‐100. The normal concentration of these elements was measured in rabbit and dog blood.
The influence of protein adsorption on interactions of cultured human endothelial cells with polymers
Authors: van Wachem P. B. , Vreriks C. M. , Beugeling T. , Feijen J. , Bantjes A. , Detmers J. P. , van Aken W. G.
Published: December 2004

A systematic study of the effects of polymer surface properties on the interaction with human endothelial cells (HEC) may lead to the development of small‐diameter vascular grafts. HEC, suspended in culture medium containing 20% serum adhered and spread onto moderately wettable polymers such as TCPS (tissue culture polystyrene). Reduced or no adhesion of HEC was observed upon the hydrophobic polymers PETP (polyethyleneterephthalate, Dacron) and FEP (fluoroethylenepropylene copolymer, Teflon). Polymers precoated with the proteins albumin (Alb), high density lipoprotein (HDL), and immunoglobulin G (IgG) inhibited the adhesion of HEC, whereas fibronectin (Fn) coátings promoted cell adhesion. Endothelialization of PETP and FEP only occurred after precoating of these materials with Fn. The adsorption of Fn, Alb, HDL, and IgG from solutions of different serum concentrations onto TCPS, PETP, and FEP was related to the adhesion of HEC. Serum Fn only adsorbed onto TCPS, with the maximum at 0.1% serum concentration. Maximal cell adhesion onto TCPS was also observed after pretreatment with a solution containing 0.1% serum. The cell adhesion inhibiting proteins Alb and HDL preferentially adsorbed at higher serum concentrations. Desorption of these proteins and exchange for, e. g., cellular Fn may result in cell spreading and proliferation of HEC upon TCPS.
Comparison of the mechanical properties of simplex P, zimmer regular, and LVC bone cements
Authors: Davies Jeff. P. , O'Connor Daniel O. , Greer James A. , Harris William H.
Published: December 2004

The mechanical properties of the three cement preparations most widely used in the United States were compared by conducting tensile and fatigue tests on Simplex P, LVC, and Zimmer Regular bone cements. Specimens of all three cement preparations were prepared for mechanical testing with and without centrifugation of the cement immediately after mixing. Although the results of the tensile testing revealed a few specific instances of significant differences in the tensile properties of the three cement preparations, there was no consistent evidence that one cement was superior in tension to the others. However, the fatigue properties of Simplex P were consistently and significantly superior to the fatigue properties of both LVC and Zimmer Regular bone cements. Centrifugation of the cement immediately after mixing significantly improved both the tensile and fatigue properties of all three bone cements. However, the fatigue strength of centrifuged Simplex P was substantially and significantly superior to the fatigue strength of the centrifuged LVC and Zimmer Regular bone cements. Since in total joint replacements bone cement is subjected to cyclic loading, these data suggest that centrifuged Simplex P is a preferable bone cement to LVC and to Zimmer Regular cement with or without centrifugation.
Complement activation by hydroxyethylmethacrylate‐ethylmethacrylate copolymers
Authors: Payne Mark S. , Horbett Thomas A.
Published: December 2004

Certain biomaterials, including nylon oxygenator and cellulosic dialysis membranes, are potent activators of human complement. In this study, the effect of polymers containing 2‐hydroxyethyl methacrylate (HEMA) on the human complement system was investigated. Copolymers of HEMA with ethylmethacrylate (EMA) varying from 100 to 40% HEMA in the monomer made by radiation initiation were used to coat glass discs. These were equilibrated with human plasma in vitro and the degree of complement activation was quantitated by C3a radio immunoassay. Significant activation was caused by copolymers made from monomers containing 60% or greater HEMA. A direct relationship between the amount of activation and the percentage of HEMA was found. The degree of activation by poly HEMA, when corrected for surface area, was quite similar to that observed for dialysis and oxygenator membranes. Similar observations were made when solid casts of crosslinked HEMA/N‐vinylpyrrolidone (NVP) copolymer gels were tested, but the magnitude of activation was much greater. The results are significant because complement activation may play an important role in the response to foreign surfaces, in both extravascular and intravascular settings. A new concept of molecular biocompatibility is proposed in which surfaces eliciting molecular transformations in any of the biological defense systems are deemed nonbiocompatible. By this criterion, the hydrogel poly‐HEMA, which has so frequently been thought of as biocompatible, is considered to be a molecularly nonbiocompatible material.
Shear creep of injectable collagen biomaterials
Authors: Wallace Donald G. , Rhee Woonza , Weiss Barbara
Published: December 2004

Shear creep experiments in a parallel‐plate apparatus were carried out on two injectable forms of collagen: semidilute nonfibrillar solutions (32 and 45 mg protein/mL) and aqueous fibrillar suspensions (at 35 and 65 mg/mL). Nonfibrillar solutions were more easily deformed than fibrillar suspensions, and both materials continued to deform slowly, even at long times (up to 6 × 104 sec). When the creep compliance, J(t), was plotted versus t1/3, regions of linear dependence were identified, which indicated that the materials were undergoing Andrade creep. At higher stress levels, J(t) diverged from t1/3, and true viscous flow occurred. A delayed viscosity could be calculated which agreed with viscosities derived from measurements under conditions of steady shear Couette flow. The time of onset of viscous flow was identified with a specific strain for each material, suggesting yield strain behavior. An analysis of recovery curves showed that at low stress levels or for short experimental times, the Boltzmann superposition was approximately obeyed, indicating linear behavior. At high stress levels and times >103 sec, both nonfibrillar solutions and fibrillar suspensions showed marked curvature of stress‐strain curves, which indicated that the materials are nonlinear in creep.
The electrochemical behavior of metallic implant materials as an indicator of their biocompatibility
Authors: Zitter H. , Plenk H.
Published: December 2004

This study introduces a simple in vitro arrangement to measure current densities of implant metals. The in vivo condition of a metallic implant lying in tissues exhibiting different redox potentials is simulated in so‐called straddle tests by applying a constant potential difference of 250 mV in saline containing the stable, fast‐reacting redox system K4Fe(CN)6/K3Fe(CN)6. From a variety of corrosion‐resistant implant metals and alloys, gold showed the highest current densities, followed by the stainless steel, the cobalt‐based alloy, and the TiAIV‐alloy. The pure metals titanium, niobium, and tantalum showed the lowest values. This can be explained by the stable oxide layer on these base metals, preventing an exchange of electrons and thus any redox reaction. This rating of metallic implant materials based on in vitro measurements of current densities is in good accordance with their biocompatibility rating reported from in vivo experiences. It seems that simple and cheap electrochemical tests allow an even more precise differentiation of the suitability of metallic materials for implant purposes than most of the conventional implantation tests, considering that biocompatibility is not only determined by corrosion products, but also by exchange currents and reaction products of redox processes involving tissue compounds.
Enhanced in vitro fibrinolytic activity of immobilized plasmin on collagen beads
Authors: Shankar Hariharan , Senatore Fred , Zuniga Pat , Venkataramani Edamanal
Published: December 2004

Plasmin was immobilized on collagenous substrates using carbodiimide as a linking agent. The kinetics of soluble and immobilized plasmin were monitored by reacting them with the chromogenic substrate S‐2251 (H‐D‐Val‐Leu‐Lys‐pNA) in the presence and absence of a2‐antiplasmin (a2‐PI). The ability of immobilized plasmin to lyse synthetic clots formed from fibrinogen and thrombin was determined by detecting the formation of fibrin degradation products (FDP). The activity of immobilized plasmin was 0.02 casein units (CU)/mg of collagen. The kinetic analysis of soluble and immobilized plasmin in the presence and absence of a2‐PI shows that while soluble plasmin activity was inhibited by the presence of a2‐PI, the plasmin inhibitor did not interfere with the ability of immobilized plasmin to attack fibrin. In the absence of a2‐PI, the ability of the immobilized plasmin to lyse synthetic clots was the same as that of soluble plasmin. In the presence of a2‐PI, immobilized plasmin produced twice the amount of FDP as did soluble plasmin. The immobilized plasmin activity was stable for a period of at least 3 months.
Cell responses to biomaterials I: Adhesion and growth of vascular endothelial cells on poly(hydroxyethyl methacrylate) following surface modification by hydrolytic etching
Authors: McAuslan B. R. , Johnson G.
Published: December 2004

Hydrogels of poly(hydroxyethyl methacrylate) (polyHEMA) homopolymer do not normally support the attachment and growth of mammalian cells. By altering the surface it has been possible to dramatically change this cell–substratum interaction so that vascular endothelial cells can attach and completely populate a poly HEMA surface. While this can be achieved by copolymerisation of polyHEMA with methacrylic acid or diethylaminoethyl methacrylate, it is most conveniently achieved by brief treatment of polyHEMA hydrogel with concentrated sulphuric acid. The resultant creation of surface—COOH groups, revealed by electron spectroscopy for chemical analysis, is consistent with the hydrolytic formation of methacrylic acid on the surface layer. Surface—COOH groups created by treatment with chloric or hydrofluoric acids were not effective. Following sulfuric acid treatment, cell adhesion and growth on polyHEMA hydrogel were better than on Teflon and approached those attained on glow–discharge‐treated polystyrene. The capacity of acid‐treated polyHEMA to adsorb albumin or fibronectin was of the order of 100‐fold or 10‐fold lower respectively than either polystyrene, Teflon, or segmented polyurethane. Hydrolytic “etching” in this way is proposed as an efficient means of expanding the use of polyHEMA hydrogel as a biomaterial without modifying the overall physicochemical properties of the bulk of the material.
The use of extraction replicas in scanning electron microscopy for the elemental analysis of marginal seals
Authors: Witcomb M. J. , Jodaikin A. , Grossman E. S.
Published: December 2004

Elemental analysis of marginal seal material on 20 bulk samples of occlusally restored teeth have shown that, generally, more elements were detected in the seal material analyzed on the bulk restoration or fractured tooth surfaces than when such material was extracted using a nitrocellulose replica prior to analysis. No mercury was detected in any of the extracted seal material and only three of the replica specimens contained silver. This implies that the technique of using extraction replicas to remove material from the amalgam‐tooth interface for subsequent x‐ray microanalysis can provide an accurate elemental composition. The details of fabrication and the advantages of using high resolution nitrocellulose replicas for extracting marginal seal material from teeth for subsequent x‐ray microanalysis are described.
A new reconstitued connective tissue matrix: Preparation, biochemical, structural and mechanical studies
Authors: Aprahamian Marc , Lambert Alain , Balboni Ginette , Lefebvre Françoise , Schmittaeusler Roland , Damge Christiane , Rabaud Michel
Published: December 2004

A fibrinogen derivative generated by thrombin was reacted with elastin to yield a new addition product or adduct between the two proteins. Addition of fibronectin, and then of collagen, did not interfere with the basic elastin‐fibrinogen reaction and conferred the qualities of an artificial connective tissue to the product. Biochemical, structural and biomechanical aspects of the new matrix were studied. Aprotinin, heparin, thiomersal, and thiourea did not inhibit the main reaction; indeed, some of these ingredients improved the matrix cohesion. Scanning electron microscopy showed the genesis of a true network whose meshes were more reticulated by the addition of thiourea. Biomechanical studies, i.e., strength and elasticity showed the thiourea matrix to be the strongest. These intrinsic properties suggest the product could have biological and clinical applications.
The influence of postcuring on the fracture properties of photo‐cured dimethacrylate based dental composite resin
Authors: Cook Wayne D. , Johannson Melinda
Published: December 2004

The dependence of the fracture behavior of photocured dimethacrylate‐based composite resins on the matrix crosslink density (varied by postcuring at various temperatures) was investigated. In general, the fracture toughness (Klc) was increased by posfcuring as has been observed for epoxy–amine networks. The flexural and diametral tensile strength was also raised by postcuring. Calculation of the inherent flaw size (a0) from these properties produced conflicting dependencies on the state of cure. It is suggested that improved wear resistance and incisal edge strength of dental composite resin restoratives may be achieved by increased degree of cure.
The enzymatic degradation of polymers in vitro
Authors: Smith R. , Oliver C. , Williams D. F.
Published: December 2004

Specimens of 14C‐labeled poly(ethylene terephthalate), nylon 66, and poly(methyl methacrylate) have been synthesized and exposed, in vitro, to a number of enzyme solutions. Poly(ethylene terephthalate) was found to be affected by esterase and papain, although in different ways, but not by trypsin or chymotrypsin. Nylon 66 was unaffected by esterase but degraded by the other three. Poly(methyl methacrylate) was not affected by any of these enzymes. This indicates that some nominally stable polymers are susceptible to degradation by enzymes under some circumstances. The amount of degradation is small, but could have significant sequelae should it be reproduced in vivo.
The evaluation of the interface between bone and a bioceramic dental implant
Authors: Gatti A. M. , Zaffe D. , Poli G. P. , Galetti R.
Published: December 2004

Methods for evaluating the interface between bone and an experimental dental implant have been analyzed. The material studied was a titanium implant coated with a mixture of alumina and titanium dioxide by means of a plasma‐jet system with the dog as the animal model. The evaluations were made on two levels: (1) in vivo, by analyzing radiographs of the peri‐implant zone with a video display computer (2) in vitro, after explantation, by analyzing vertical and horizontal sections of the sample with an optical and a scanning electron microscope, and by a video display computer analysis of the microradiographs of these sections.
Competition between adsorbed fibrinogen and high‐molecular‐weight kininogen on solid surfaces incubated in human plasma (the vroman effect): Influence of solid surface wettability
Authors: Elwing Hans , Askendal Agneta , Lundström Ingemar
Published: December 2004

The influence of the surface energy on the competition between fibrinogen and high‐molecular‐weight kininogen has been studied with the use of a recently described wettability gradient method. One finding is that the decrease in the antifibrinogen binding on plasma incubated gradient surfaces was not associated with an increase in anti‐HMWK binding at all parts of the gradient surfaces.
Adsorbed behavior of spin‐labeled silane coupling agent on colloidal silica studied by electron spin resonance
Authors: Nishiyama Norihiro , Katsuki Hirokazu , Horie Kozo , Asakura Tetsuo
Published: December 2004

The adsorption mechanism of silane coupling agent on the colloidal silica surface is studied with spm‐labeled silane coupling agent using ESR method. The density of the adsorbed silane molecules was determined to be approximately 1.5–2 molecules per 100 Å2 of the silica surface in 95% ethanol solution. In addition, ESR signal of spin‐labeled agent adsorbed on the colloidal silica surface was composed of two components; slow component attributable to the agents adsorbed directly on the SiOH groups of the silica surface through hydrogen bond formation and rapid one attributable to the agents interacted with such adsorbed silane molecules.
Viscoelastic behavior of polyurethane vascular prostheses
Authors: How T. V. , Annis D.
Published: December 2004

A method of evaluating the in vitro viscoelastic properties of microfibrous Biomer poly(ether‐urethane‐urea) vascular prostheses is outlined. Quasi‐static and dynamic tests were carried out on Biomer grafts of diameter between 3.4 mm and 3.8 mm and wall thickness between 0.25 mm and 0.55 mm. It is shown that the quasi‐static compliance of a Biomer graft may be determined from an equation relating transmural pressure, radius, and longitudinal strains in terms of the graft dimensions and material constants. The dynamic compliance spectra were evaluated as a function of the longitudinal and circumferential strains and temperature. Although the ratio of dynamic compliance to quasi‐static compliance was linearly related to the logarithm of frequency it was not significantly affected by strains or temperature over the relevant ranges studied. Employing the usual assumptions of linear isotropic incremental elastic theory the dynamic elastic and viscous moduli were calculated as a function of frequency. Biomer grafts were more viscous than canine carotid and femoral arteries, especially at the higher frequencies. The variation in the ratio of dynamic to static incremental modulus with frequency was similar to that observed in the femoral arteries by Bergel (J. Physiol., 156, 458–469 (1961)).
Bonding behavior between two bioactive ceramics in vivo
Authors: Kitsugi Toshiaki , Yamamuro Takao , Nakamura Takashi , Kokubo Tadashi , Takagi Masataka , Shibuya Takehiro , Takeuchi Hiroyasu , Ono Mikiya
Published: December 2004

The purpose of this study is to examine the chemical bonding mechanism between bioactive ceramics in vivo. Two experiments were performed. In the first experiment, rectangular specimens (5 mm × 5 mm × 25 mm) of apatite‐wollastonite containing glass‐ceramics (designated A 7middot; W — GC) were used. In the second experiment, plates (15 mm × 10 mm × 2 mm) of A · W — GC and three types of hydroxyapatite (designated HA) were used. The sintering temperature and porosity (%) of the three types of HA were 1200°C (0.4%), 1000°C (4.8%), and 800°C (45%), respectively. In each experiment, two pairs of specimens of identical material, one bound with silk thread, the other not bound, were implanted subcutaneously into rats. In the first experiment, bonding of only bound specimens was observed at 3 and 6 months after implantation. The observation of interface by SEM‐EPMA showed that a Ca — P‐rich layer formed between the two specimens. In the second experiment, bonding of both bound and nonbound A · W — GC produced identical results 1 month after implantation. For HA sintered at 800°C and 1000°C, bonding was observed in every specimen. This phenomenon might be caused by the chemical change of hydroxyapatite occurring at different sintering temperatures. The Ca — P‐rich layer was observed between two plates. These results suggest that self‐repair of bioactive ceramic is possible under certain conditions.