bluuebunny/crossref_metadata_2025 huggingface dataset:
Dental cements, direct filling resins, composite and adhesive restorative materials: A resume
Authors: Paffenbarger George C.
Published: December 2004

This resume concerns experimental and commercial dental cements and restorative and adhesive materials usually containing nonmetallic inorganic components, the biocompatibility of the above with oral tissues, proposed methods of bioevaluation, the oral environment, the nature of the hard tooth tissue, cavity treatment, agents for bonding the restorative material to the tooth, and 112 references.

The cements include those based on (C‐1) zinc oxide‐eugenol with additives such as zinc acetate, rosin, polymers and most important o‐ethoxybenzoic acid (EBA); (C‐2) metallic oxides‐phosphoric acid; (C‐3) acid phosphate salts‐water; (C‐4) aluminosilicate glass‐phosphoric acid; (C‐5) zinc oxide‐polyacrylic acid; (C‐6) methyl methacrylate‐poly‐(methyl methacrylate) with or without inorganic fillers. Direct filling resins (C‐6) without filler and composite restorative materials (C‐6) with filler are based on acrylic resins or reaction products of acrylic (methacrylates) with other resins. Coupling agents include cyanoacrylates, epoxy‐acrylic adducts and polyurethanes. The 10 tables give composition, values for pertinent physical properties or dental requirements. (C‐2) Dominates the cements but (C‐1) with (EBA) and (C‐5) which has some adhesion to hard tooth tissues and stainless steel may displace (C‐2). (C‐4) Restorative materials are anticariogenic and widely used but are being supplanted by composite restorative materials.
Macromolecular aspects of biocompatible materials—a review
Authors: Bruck Stephen D.
Published: December 2004

This paper is limited chiefly to the question of blood compatibility and will not cover areas such as dental applications and mechanical support prostheses. The demand for blood compatible materials has become important for cardiac and pulmonary assist devices and artificial hearts. Since the second World War, a larger number of synthetic materials became available ranging from elastomeric to hard, hydrophobic to hydrophilic systems, but almost all of these were developed for large‐scale commercial end‐use where the presence of small quantities of impurities, traces of catalysts, plasticizers, etc., is not too critical. For medical implants, it is necessary to prepare the appropriate polymers in the chemically pure state. The ultimate goal is the fabrication of practical, economical, and working devices. This goal demands that the material not only be compatible with blood, but also be able to perform distinct mechanical and physico‐chemical functions or be useful for the isolation of implantable prostheses from body fluids.
Development of blood‐compatible elastomers. III. Hematologic effects of avcothane intra‐aortic balloon pumps in cardiac patients
Authors: Nyilas E. , Leinbach R. C. , Caulfield J. B. , Buckley M. J. , Austen W. G.
Published: December 2004

As of this date, tri‐segmented intra‐aortic balloons made from Avcothane‐51 elastomer were applied in the counterpulsation treatment of about 80 cardiac patients. The combined effects induced by the implanted elastomer and the hemodynamics of pumping are analyzed by means of hematologic changes observed in a set of 28 patients who were treated at the Massachusetts General Hospital for an average period of about 4 days, and represent a widely diversified group in terms of their clinical conditions. In no case were, any significant adverse hematologic effects induced by this assist device whether the hosts had been anticoagulated or not heparinized at all. While platelet levels were somewhat affected by the assist device, the particular conditions of the patient appear to have an effect of at least, equal magnitude. In addition to platelet levels steadily decreasing with pumping time, changes in platelet levels similar to the pattern of “platelet tide” occurred with about equal frequency. Monitored in terms of erythrocyte counts and plasma hemoglobin levels, no significant degree of hemolysis could be detected. Leukocyte counts in patients having above‐normal levels at the beginning of pumping returned to normal while in other cases there were no significant changes. Fibrinogen, one of the plasma proteins most sensitive to foreign surfaces, showed levels increasing from subnormal to normal as a function of pumping time. The overall in vivo performance of Avcothane‐51 balloons appers to be consistent with the state of the surfaces of recovered devices, showing only the presence of occasional adherent platelets upon examination by scanning electron microscopy.
Vitreous carbon percutaneous elctrodes for muscle stimulation
Authors: Gibbons D. F. , Peckham P. H. , Martin R. L.
Published: December 2004

In vivo and in vitro tests have demonstrated that vitreous carbon anodes are corroded when operated under conditions typical of those used for the physiological stimulation of muscle. Similar electrodes are completely inert under cathodic conditions. The chronic stimulation experiments demonstrate acute and chronic inflammation with increased vascularity in the tissue adjacent to an anode.
Artificial skin I. Preparation and properties of pluronic F‐127 gels for treatment of burns
Authors: Schmolka Irving R.
Published: December 2004

The preparation of block polymer surface‐active agents derived solely from propylene oxide and ethylene oxide is described. The physical properties of a nonionic surfactant of 12,500 molecular weight, Pluronic F‐127, are presented. The toxicity data of the polymeric series is reviewed. The preparation of cold aqueous solutions of the F‐127 solution, to which silver salts and other medicaments are then added, is described. By raising the temperature, these fluid liquids are then converted to strong “ringing” gels or viscous ointments which are suitable for application to a burn wound or abraded skin area. The factors involved in altering the yield strength of the gel are presented.
Carbon fiber reinforced polyethylene for possible orthopedic uses
Authors: Sclippa Ermes , Piekarski K.
Published: December 2004

Properties of injection‐molded high‐density polyethylene reinforced with carbon fibers were investgiated. With 20% by weight carbon fibers tensile strength of polyethylene was almost doubled. Further increase of volume fraction of fibers did not produce as dramatic results. With 40% by weight carbon fibers, elastic modulus increased one order of magnitude: from 0.225 × 106 psi to 2.48 × 106 psi. This value is close to the value of the elastic modulus of bone, hence the material may substitute for bone where the same stiffness is required. The total strain at fracture was reduced two orders of magnitude, but still stayed comparable to total strain at in bone failures (1–2%).

No appreciable changes were noted in shear strength, impact strength and wear resistance. The work to fracture increased from 0.9 to 2.9 kg cm/cm2 with 40% of carbon fibers.

The most significant improvement of polyethylene with addition of carbon fibers was demonstrated in measurements of viscoelastic properties of the material. Creep characteristics were dramatically improved.

In summary, it can be stated that injection‐molded reinforced polyethylene has much superior properties to the nonreinforced P.E. which can be further improved if better adhesion between P.E. matrix and reinforcing fibers can be secured.
New types of synthetic infusion solutions. I. Investigation of the effect of solutions of some hydrophilic polymers on blood
Authors: Kopeček J. , Šprincl L. , Lím D.
Published: December 2004

The behavior of aqueous solutions of poly [N‐(2‐hydroxypropyl) methacrylamide], poly(N‐ethyl methacrylamide), poly(N‐ethyl acrylamide), and poly‐(triethyleneglycol monomethacrylate) was investigated and characterized in tests required for synthetic infusion solutions. The above solutions were characterized from the viewpoint of toxicity, pyrogenic properties, antigenic properties, effect on the determination of the blood groups, and effects on hemocoagulation. The elimination from blood circulation was studied on several fractions of the 14C‐labelled poly[N‐(2‐hydroxypropyl) methacrylamide] having different molecular weights. It was found that in all tests the properties of the polymers investigated do not depart from the expected behavior.
Development of block copolyether‐urethane intra‐aortic balloons and other medical devices
Authors: Brash John L. , Fritzinger Bruce K. , Bruck Stephen D.
Published: December 2004

The development of materials and technology suitable for the fabrication of intra‐aortic balloons (IABs) is described; a brief discussion of materials and a fabrication process for flexible ventricular assist devices (heart massage cups) is also given. A series of block copolyether‐urethanes was developed, the mechanical properties of which can be varied over a wide range. One member of the series was “tailored” specifically for nondistensible IABs of a particular design. Several of the block copolyether‐urethanes were subjected to selected in vitro and in vivo tests for blood compatibility and compared favorably with other materials. A two‐stage process was developed for the fabrication of high‐quality IABs from block copolyether‐urethanes. This process involves dip‐forming over expendable wax mandrels, followed by removal of the wax and solvent‐welding the balloon to the tip and catheter.
Aspects of three types of hydrogels for biomedical applications
Authors: Bruck Stephen D.
Published: December 2004

Some of the chemical and physical properties of three different hydrogels are analyzed as they relate to biological compatibility. The importance of the permeability and diffusion coefficients, porosity, and the possible role of quasiorganized water within the hydrogels are emphasized. It is suggested that the biological environment with its dissolved components such as ions, proteins, carbohydrates, lipids, and enzymes will influence the ultimate biological performance of hydrogels. This biological performance will depend not only on the hydrophilicity of the system but on numerous other parameters including the chemical composition, types and number of crosslinks, presence of functional groups, quasi‐organized water structure, porosity, and the thermodynamic interaction parameters between the components of the biological environment and the gel. It is suggested that the presence of anionic gorups on certain synthetic hydrogel surfaces may be not essential for blood compatibility, provided that such materials are carefully distinguished from other hydrophilic gels.
Analyses of a silicone elastomer heart ball valve
Authors: Mayhan K. G. , Biolsi M. E. , Simmons E. M. , Almond C. H.
Published: December 2004

This work represents a preliminary study of one case history of a silicone heart valve. The laboratory techniques employed have proven useful in characterizing the polymer before and after implantation. Before any model explaining ball variance can be proposed it must be determined whether the polymer loses its integrity because specific constituents in the body fluids interact with primary valence bonds in the polymer chains, or if the fluids simply cause swelling and plasticization of the crosslinked system and the damage is the result of mechanical work on the weaker polymer system. Detailed kinetic and thermodynamic studies are underway to answer these questions.

The work summarized in this paper refers to the evaluation of only one specimen and should not be taken to mean that every silicone ball from a heart valve prosthesis will show this variance. The incidence of functionally variant silicone balls as reported to one manufacturer represents approximately 1.5% of the aortic and less than 0.05% of the mitral prostheses which have been supplied by this manufacturer. A small percent of valves of this type have the potential of becoming functionally variant and this is one failure mode which should be considered in the implantation of silicone ball valves.
Changes in nonosseous tissue adjacent to titanium implants
Authors: Meachim G. , Williams D. F.
Published: December 2004

A combined histological, metallurgical, and clinical study has been made in 19 instances where a surgical operation had been performed to remove a titanium implant used in the treatment of disease or trauma in man. All the implants were static devices such as pins, plates and rods. Histological examination of nonosseous tissue excised from adjacent to the implant was supplemented by estimation of its titanium content by neutron activation analysis.

The results indicate that in some patients titanium can be liberated into tissue adjacent to titanium implants. The phenomenon can occur in the absence of corrosion or fracture of the implant, and is unrelated to the possible liberation of wear particles from an artificial articular surface. There is variation from individual to individual in the amount, if any, of titanium released. In the case of those implants showing titanium release, the results suggest that local release of the metal, or its subsequent accumulation in the tissue, is a patchy process at the implant site. The histological features of the local reaction of nonosseous tissue to titanium release are described. No conclusions have been drawn concerning possible effects on the osteogenic response to the insertion of the implants and on the overall state of the bone at the time of their removal. From study of the clinical records it is apparent that considerable caution is needed before concluding that release of titanium can cause clinically significant local effects. Although such effects may have occurred in a minority of patients, this possibility is by no means proven. A distinction must be drawn between a “metal reaction” in the histological sense and a “metal reaction” in the clinical sense.
A study of the influence during trituration of air‐borne impurities on the strength of amalgam
Authors: Hansen David A. , Holland John W. , Lewis Stephen A. , Moore David L.
Published: December 2004

The purpose of this study was to determine the effect of air‐borne gaseous impurities, introduced during trituration, on the strength of amalgams.

Four experiments were conducted. Each experiment consisted of a control group (1) in which the amalgam was triturated in air and an experimental group (2) in which the amalgam was triturated in argon, an inert gas. Standard specimens yielded mean diametral tensile strengths of 5950 psi (1) and 6603 psi (2). Hand compacted specimens yielded mean diametral tensile strengths of 5829 psi (1) and 6412 psi (2). Standard specimens yielded mean compressive strengths of 46,636 psi (1) and 47,269 psi (2). Specimens compacted hydraulically yielded mean uniaxial tensile strengths of 10,928 psi (1) and 11,660 psi (2).

Statistically, the differences between the means for each experiment are significant. Hence, trituration in an inert gas has been shown to be an effective method for increasing the strength of amalgam.
A preliminary report on thirty‐five geometric total knee arthroplasties
Authors: Fortune William P. , Adams John P.
Published: December 2004

This paper reviews the first 35 cases of geometric total knee arthroplasties performed on 32 patients at The George Washington University Medical Center. The procedure was done in 25 patients with rheumatoid arthritis, 5 patients with osteoartritis, and 2 patients with traumatic arthritis. Ages ranged from 38–83 years with an average of 58 years. This is a short‐term follow‐up with the longest of one year duration and the shortest two months. Fourteen patients had previous knee surgery including one that had three previous procedures. Indications and contraindications are outlined and the surgical procedure is described with an effort to point out certain technique problems. Twenty patients had complete relief of pain, ten had slight pain with activity. One has severe patellofemoral pain on weight‐bearing and one has constant pain. Twenty patients had varying degrees of instability prior to surgery and none following the procedure and a 50° valgus deformity has been corrected satisfactorily. It was observed that patients with restricted motion and pain gained significant motion and pain relief while those with good motion and pain gained less overall and in some instances lost. Peroneal nerve palsies, patellar tendon avulsions, and wound complications are presented. We feel on the basis of this limited experience that this total knee system offers to the patient in need of a salvage procedure a stable, essentially pain‐free knee that has increased mobility and function.
Porous titanium dental implants
Authors: Young F. A.
Published: December 2004

Titanium implants have been designed which utilize a solid core and porous exterior. The technique for implants containing posts utilizes a cast chromium‐cobalt splint for fixation and the buried implants are held in place by the overlying gingiva until tissue growth into the porosity results in stabilization.

Clinically successful post implants with apparent bone ingrowth and healthy gingiva surrounding the post have been achieved for periods up to three months.
Hemiarthroplasty: A histological and scanning electron microscope study
Authors: Cameron Hugh U. , Macnab Ian , Anderson William
Published: December 2004

The membrane surrounding the hip joint containing metal endoprostheses were examined in 20 patients using histology and the scanning electron microscope (SEM). No synovial cells were found. The capsule was dense fibrous tissue, covered at the surface with an amorphous membrane of doubtful composition. Several questions have been raised, such as the role of synovial cells in cartilage nutrition, the nature of the fluid in these joints, and secretion into and absorption out of the artificial joint.
Determination of mercury vapor pressure over amalgams from weight loss data
Authors: Reynolds C. L.
Published: December 2004

Mercury vapor pressure over clinically used amalgams, as well as the individual phases composing dental amalgam, has been determined from weight loss data using Langmuir's time averaged weight loss technique. The results show that the Hg vapor pressure of 38.2 × 10−6 torr over the pure γ1 (Ag2Hg3) phase is more than an order of magnitude greater than that over the remaining amalgams considered: β1, α1, γ2, Ag‐Sn amalgams, True Dentalloy amalgams, Au‐containing amalgams, and Dispersalloy amalgams.
Tracer diffusion of silver and tin in a dental alloy (Ag3Sn)
Authors: Okabe Toru , Hochman R. F. , McLain M. E.
Published: December 2004

The diffusivities of Ag110m and Sn113 in bulk Ag3Sn were measured using the method of Gruzin. The volume diffusion coefficients were determined over the temperature range 200 to 400°C, with temperature dependence given by D \documentclass{article}\pagestyle{empty}\begin{document}$ \mathop = \limits_ \cdot $\end{document} 1.03 × 10−3 exp (−22,400/RT) and D = 4.01 × 10−4 exp (−22,800/RT) cm2/sec. The fact that silver is the faster moving species in bulk Ag3Sn is important to the amalgamation process. On the other hand, it was found that along grain boundaries, tin tracer atoms diffused faster than did silver atoms. Faster grain boundary diffusion of tin, however, may not be a decisive factor in the actual amalgamation process, since mercury penetration exceeds the migration of tin atoms along grain boundaries.
Reduction of maximum temperature in the polymerization of cold‐ and heat‐curing acrylic resins
Authors: de Wijn J. R.
Published: December 2004

Kinetic concepts of reducing exothermal effects during curing of biomedical acrylic resin systems are discussed. The effects of addition of 1, 4‐cyclohexadiene and cyclohexylmethacrylate to the monomer on the temperature rise in cold‐ and heat‐curing resin have been determined. Both compounds appear to be effective in damping the temperature peaks. Screening of compressive strengths and residual monomer determinations revealed that addition of cyclohexadiene results in a less complete polymerization than in the case of cyclohexyl methacrylate modified resins.
Thermal properties of cancellous bone
Authors: Calttenburg Richard , Cohen Jonathan , Conner Scott , Cook Nathan
Published: December 2004

Specimens of beef bone were analyzed for thermal conductivity and thermal capacity. The thermal conductivity was about 7 × 10−4 cal/cm/sec/°C, that is about the same as for other tissues. As regards thermal capacity, the determination of 0.73 cal/cm2/°C also was similar to that in other tissues Both thermal conductivity and capacity were isotropic with respect to the layer of epiphyseal cartilage, and the orientation of bony trabeculae.

Thermal probes were devised heated either by water or by electric current to destroy localized volumes of bone, as in surgery. To achieve necrotizing temperatures, the sizes of such probes and the times of application of heat were determined.
Auger analysis of surface films on Ag3Sn
Authors: Grenga Helen E. , Carden John L. , Okabe Toru , Hochman Robert F.
Published: December 2004

The surface properties of Ag3Sn are important in the amalgamation process so that mechanical abrasion is generally necessary to get a satisfactory amalgam. Therefore, the present study was undertaken to characterize the surface of Ag3Sn after several types of surfaces treatments.

Homogeneous polycrystalline rods of Ag3Sn were prepared in vacuo from high purity (99.99%) Ag and Sn. Specimens were sliced from these rods and prepared as follows: (1) mechanically polished, (2) polished as in (1) and allowed to sit in air for three days and (3) polished as in (1) and electrolytically etched. Each of these specimens was examined by Auger electron spectroscopy.

The results showed that after mechanical abrasion the surface film was primarily oxide and the Ag to Sn ratio was lower than the bulk composition, indicating preferential oxidation of Sn. After sitting in air sulfur was also present on the surface and the Ag to Sn ratio was greater than that immediately after polishing, indicating the formation of Ag2S. After electrolytic etching some oxide was still present, but only a trace of sulfide was found. However, the Ag to Sn ratio was greater than that for mechanically polished specimens, indicating preferential dissolution of Sn. Therefore, it is seen that the surface preparation of Ag3Sn has a marked effect on Ag and Sn concentrations and the nature of films at the surface.
Modified collagen membrane as a skin substitute: Preliminary studies
Authors: Tavis Michael J. , Harney John H. , Thornton James W. , Bartlett Robert H. , Woodroof E. Aubrey
Published: December 2004

Modified collagen membrane when compared to autograft, homograft, heterograft and silicone polymer memberane, demonstrated a superior adherence on split and full‐thickness surfaces, but proved to be an inferior covering for granulating surfaces. Water vapor transport was found to be adequate and adaptable to modification. It was found to be permeable to most commonly used topical antibiotics, and no significant antigenicity could be demonstrated. In a controlled animal burn study, modified collagen membrane proved superior to homograft and heterograft in regard to mortality, time to grafting, bacteriology and autograft take. These studies provide a background for further laboratory and clinical studies now in progress.
MP35N: A corrosion resistant, high strength alloy for orthopedic surgical impants: Bio‐assay results
Authors: Escalas Felix , Galante Jorge , Rostoker William , Coogan Philip S.
Published: December 2004

A cobalt based alloy, MP35N, with excellent mechanical properties has been recently introduced as a material for surgical orthopedic implants.

A study was made of local and systemic host response to this material in two different mammal species. The implantation time ranged from one to 12 months.

The result of this study indicated: MP35N produces a degree of local tissue response comparable to that of 316L stainless steel. No sytemic side effects were observed during the implantation times included in this study.
Experiences with Al2O3 implantations in humans to bridge resection defects
Authors: Engelhardt A. , Salzer M. , Zeibig A. , Locke H.
Published: December 2004

Various implants have been developed for the upper and lower extremities and the spine. In order to establish whether endoprostheses made of Al2O3 will show the same good biocompatibility in humans as it has in experiments with animals, endoprostheses implantations were performed in 4 patients: 2 upper arms, 1 radius, 1 vertebra body. The implants were exposed to various loads. The biomechanical conditions were considered in the construction. The results reveal that the knowledge of material properties and prior calculations make possible the development of satisfactory endoprostheses. X‐ray examinations confirm these deductions. Good functionality was achieved in vivo with all implants. They were all mechanically anchored, no bone cement was used. Thus the biocompatibility of the material was not limited. A histological examination is made of one implant. The macroscopic examination showed a stable fit and no pathological reactions. X‐rays revealed that the bone remained in good contact with the implant. The longest observation period was over 1 1/4 years. Present observations show that the use of Al2O3 implants, without the use of additional materials (bone cement), results in a tight fit of the implants.
Thromboresistance of glass after glow discharge treatment in argon
Authors: Baier R. E. , Depalma V. A. , Furuse A. , Gott V. L. , Kammlott G. W. , Lucas T. , Sawyer P. N. , Srinivasan S. , Stanczewski B.
Published: December 2004

Glow discharge treated (GDT) inorganic materials are sterile and free of all organic contaminants. Such materials implanted in the canine inferior vena cava often demonstrate significant thromboresistance. Standard Pyrex glass tubing was GDT in argon to provide a surface free energy above 70 dynes/cm, slight surface negativity, and other surface‐physical modifications of its interface. Chromic acid cleaned lengths of the same tubing, and short segments whose edges were not fire‐polished were used as controls. Upon canine implantation, the in vivo results were similar in independent surgical laboratories. The glass was implanted as 1.4 cm long rings or as 5 cm long tubes in separate medical centers according to different protocols. GDT specimens remained patent; all controls accumulated thrombi. A remarkably pure, low critical surface tension, labile protein coating covered all cylindrical lumens after 2 hr in vivo. This coating diminished within 2 weeks and was essentially absent after 480 days, even though scanning EM showed evidence of a micron thick luminal film, probably eroding glass. No emboli were found in the implant animal's kidney or lungs at any stage.
Relative thrombogenicity of polydimethylsiloxane and silicone rubber constituents
Authors: Weathersby Paul K. , Kolobow Theodor , Stool Edward W.
Published: December 2004

Medical grade silicone rubber (MGSR) is composed of polydimethylsiloxane (PDMS) as well as silica filler, oxidation products from the curing process, and other components. In a test that excludes air‐blood interfaces, PDMS radiation cured under nitrogen has a whole blood clotting time 22% longer than MGSR. Curing the PDMS under oxidizing conditions maintains a 10% prolongation, but addition of silica filler to the PDMS returns the clotting time to that of MGSR. Extracting MGSR with solvents other than water appreciably lowers the clotting time. These results indicate that “pure” PDMS has an intrinsically high thromboresistance. Thrombogenicity is increased by the use of silica filler and oxidizing cure, as in MGSR.
Biological evaluation of polymers I. Poly(methyl methacylate)
Authors: Dillingham E. O. , Webb N. , Lawrence W. H. , Autian J.
Published: December 2004

A series of poly(methyl methacrylate) formulations differing widely in chemical and physical properties was employed for the evaluation of primary screening methods for the assessment of acute toxicity. Materials and USP extracts of materials were tested in parallel. Tissue culture, hemolysis, intradermal irritation, systemic toxicity, muscle implant and histopathologic responses were determined for each of 27 formulations. A determination of the nonvolatile methanol extractable components was carried out on each formulation. The formulations varied with respect to percent, w/w, methyl methacrylate, N,N‐dimethyl‐p‐toluidine, stannous octoate, 3,4‐diamino‐toluene and, also, with respect to curing conditions. Volatile components, primarily methyl methacrylate, of three selected formulations were determined quantitatively by vacuum distillation and mass spectrographic analysis.

Statistical analysis of the primary data indicated a significant correlation of residue weight (methanol extractable) with hemolytic activity (r = 0.93) and with the cumulative biological response (r = 0.9). Multiple linear regression analysis of residue weights with hemolysis and intradermal irriation responses gave the highest overall correlation (r = 0.96). Hemolytic activity and tissue culture responses were significantly correlated (r = 0.87). It was concluded that the observed variation of biological test results reflected significant differences in the toxicity of the test materials. The poly(methyl methacrylate) series examined was relatively low in toxicity and the biological tests examined, particularly the in vitro tests, were found to be responsive to formulation and curing conditions which indicated their suitability for primary toxicity screening.
The influences of electrical potential and surface finish on the fatigue life of surgical implant materials
Authors: Bapna M. S. , Lautenschlager E. P. , Moser J. B. , Meyer P. R.
Published: December 2004

The influence of both imposed anodic potential in Ringer's solution and surface finish on the fatigue lives of annealed 316 type stainless steel and annealed pure titanium were measured and statistically compared to fatigue data run in air. The applied potentials in simulated extracellular fluid approximated conditions existing within the body while also producing the types of surface defects actually found on removed long time implants within the time interval of the accelerated R. R. Moore fatigue tests. Differentiating tests were run at single levels of applied cyclic stress well above the endurance limits.

In Ringer's solution, the fatigue life of the 316 stainless steel decreased with increasing applied potential, and at +500 mV was significantly shorter than when run in air. At each condition, the 316 stainless steel was independent of initial surface finish. In contrast, the fatigue life of titanium improved rapidly with increasingly fine surface finishes. Furthermore, compared to air, the application of +500 mV in Ringer's solution improved the life of the rough surface finished material and markedly increased the number of cycles to failure for the electropolished specimens.
Ultrathin coating by plasma polymerization applied to corneal contact lens
Authors: Yasuda H. , Bumgarner M. O. , Marsh H. C. , Yamanashi B. S. , Devito D. P. , Wolbarsht M. L. , Reed J. W. , Bessler M. , Landers M. B. , Hercules D. M. , Carver J.
Published: December 2004

Plasma coating (deposition of polymer under the influence of plasma) is utilized to modify the surface properties of corneal contact lens. An ultrathin layer (thickness of roughly 200 Å) of plasma polymer of acetylene/H2O/N2 is applied to poly(methyl methacrylate) (PMMA) corneal contact lenses. The surface becomes highly wettable with water compared to uncoated lens. When coated and uncoated contact lenses are placed on rabbit eyes, a remarkable difference in accumulation of mucous matter is observed. With the control lenses, the accumulation of mucous matter in a week is sufficient to affect the optical clarity of the lenses, whereas the coated lenses show no change after three months continuous wearing. The comparative degree of adhesion of the corneal epithelium cells onto glass, modified glass, PMMA, and coated PMMA surfaces is studied using tissue cultures and phase contrast microscopy. The coated PMMA surface exhibits a degree of tissue adhesion lower than that of control PMMA and higher than that of glass surface, and no sign of toxicity of the coated surface is observed by the tissue cultures.
Pharmacological properties of the plasticizer, acetyl N‐tributyl citrate, and its extraction from poly(vinyl chloride) tubing
Authors: Hollingsworth M.
Published: December 2004

Aqueous extracts of a PVC transfusion tubing contracted isolated guiea‐pig ilea. A pharmacological and chemical study (infrared spectroscopy, gas–liquid chromatography) showed that this was due to extration of the plasticizer, acetyl N‐tributyl citrate (ATBC). The concentrations of ATBC to produce contractions of the isolated guinea‐pig ileum (from 1 μg/ml) can be compared with those achieved after recirculating tubing under conditions simuflating use (up to 6 μg/ml).

In assenssing the toxicity of plastic tubing, there is a need to determine extraction of constituents under conditions simulating use and the effects of such extracts on a cariety of tissues.
Microstructure in gold‐containing Ag3Sn‐amalgam
Authors: Malhotra Manohar L.
Published: December 2004

The present study was conducted in order to understand the microstructural characteristics in dental amalgam which consists of both spherical and irregular Ag3Sn alloy particles with gold substituted in varying amounts for silver (0, 9, and 15%). Spherical alloy particles were used as obtained from Western Gold and Platinum and irregular alloy particles were prepared in the laboratory and then employed in the present study. The amalgam was prepared from the alloy particles by the trituration and condensation method. The polished and etched samples were studied using the techniques of X‐ray diffraction, optical metallography, scanning electron microscopy, and X‐ray energy dispersive spectroscopy. The microstructure in both types amalgam studied after two weeks of preparation contains γ (unreacted Ag3Sn particles), γ1 (Ag2Hg3), and γ2 (Sn7–8Hg) phases in pure Ag3Sn‐amalgam and γ, γ1, and (Au–Sn) phases in gold‐containing amalgam. The (Au–Sn) phase existed in the form of rings surrounding the γ grains and acted as a barrier for mercury diffusion in Ag3Sn particles.
The rate of bone ingrowth into porous metal
Authors: Camron H. U. , Pilliar R. M. , Macnab I.
Published: December 2004

Experiments have been devised to study the rate of ingrowth of bone into porous metal with pore sizes up to 100 μ and to study the significance of a gap between the porous metal surface and bone.

When the porous coat was in direct apposition with bone, the implant was firmly locked in place after a three week period and the plateau value of implanttissue shear strength was reached at four weeks. A gap of 1.5 mm between the bone and the implant was bridged by new bone wihtin four weeks.
Diffusion of mercury in Ag2Hg3 from weight‐loss data
Authors: Timmons C. F. , Hines A. L. , Lightsey G. R. , Okabe T.
Published: December 2004

The weight‐loss method was employed to determine the diffusion coeffcients of mercury in Ag2Hg3 alloy at temperatures in the range of 64–120°C. Diffusion coeffcients for nonhomogeneous specimens obey the relationship:

Diffusion coeffcients for nonhomogeneous samples were found to be an order of magnitude greater than values found for homogeneous samples.
In vivo degradation of silicone rubber poppets in prosthetic heart valves
Authors: Cuddihy Edward F. , Moacanin Jovan , Roschke E. John , Harrison Earl C.
Published: December 2004

Dynamic shear modulus G′ was measured throughout the volume of three nonvariant silicone rubber poppets which were recovered from aortic prosthetic heart valves that had been implanted for 4 days, 52 days, and 8 years. Similar measurements were obtained for two unused silicone rubber poppets. Although the recovered poppets exhibited no obvious physical evidence of damage, the silicone rubber had undergone in vivo degradation throughout the poppet volume as indicated by decreases in modulus. The measurements also indicate that the poppet surface degrades at a rate faster than the core. Further, comparison with data reported in the literature suggests that the surfaces of variant poppets degrade at a rate faster than the surfaces of nonvariant poppets.
Prefabricated silicone subdermal mandibular implants: Observations and problems related to their application
Authors: Habal Mutaz B. , Chalian Varoujan A.
Published: December 2004

Success in the use of custom‐fabricated Silastic implants in patients with facial contour defects led us to utilize this method in reconstructing mandibular defects. However, mandibular reconstruction with alloplastic material is quite difficult because of the presence of continuous stress and motion in that region. The evolution in the use of the mandibular implant from the commercially available one to the K‐wire reinforced, prefabricated, silicone implant was largely dependent on the availability of silicone and the ultimate result obtained.

In the past few years, about 30 subdermal implants were inserted. Some of those implants were placed immediately into patients undergoing resection for tumor. The implant was prefabricated prior to surgery from x‐ray measurements of the anticipated segment to be resected; it was then used to reconstruct the defect prior to the final closure of the operative wound. Other implants were manufactured 6–18 months after resection for tumor or for deformity as a result of trauma. The implants were used to reconstruct the facial defects and to correct the functional abnormality, such as drooling or deviation of the affected side by the unstable mandibular segment. Patients with severe congenital malformation have soft tissue deficiency in association with their bony malformation. Therefore, implants in such conditions were doomed to failure.

Patient selection is the key to successful implantation.
Oxidized orlon as a blood interface
Authors: Ross J. N. , Wright J. T. M. , Eskin S. , von Koch L. , Normann N. A.
Published: December 2004

Polyacrylonitrile fabric (Orlon) may be oxidized by heating in air, when it becomes black and carbonized. During the heat treatment, the fibers shrink; this shrinkage allows components such as diaphrams to be shaped around molds. Oxidation reduces the tensile strength by about 25% and also reduces the stiffness of the material.

The oxidized Orlon was screened in tissue culture for possible cytotoxic effects. Finding none, patches of the material were sutured into the right atrium of dogs and examined after 48 hr. Because of encouraging results, 10 atrial patches, consisting of Dacron velour and oxidized Orlon side‐by‐side, were implanted into the right atrium of dogs. Five patches were backed with Silastic to render them impervious, and five with segmented polyurethane. The atrial patches were examined after 48 hr, and in all instances the oxidized Orlon part of the patch was coated with a thinner and smoother fibrin layer than was the Dacron velour half.

A left ventricular bypass pump was fabricated from oxidized Orlon and spraycoated on the nonblood surface with segmented polyurethane. After 48 hr implantation in the chest cavity of a calf, pumping without systemic anticoagulation, the pump was found covered by a thin, smooth, firmly attached layer of fibrin.
Poly(methyl methacrylate)–aqueous phase blends: In situ curing porous materials
Authors: de Wijn J. R.
Published: December 2004

A potential implant material has been developed which combines the advantages of curing in situ and an open porous structure. This paper deals with synthesis and characterization of the material, which is a modification of the well‐known acrylic bone cements. Some early results of animal experiments are mentioned.
Biomaterials and collagen synthesis
Authors: Cohen I. Kelman , Diegelmann Robert F. , Wise William S.
Published: December 2004

A highly reactive biomaterial (clay) and a relatively nonreactive substance (silicone) were implanted separately in primarily closed incisions on the backs of rats. Collagen synthesis was determined in biopsies from each test site after 8 days. The biochemical measurements of collagen synthesis showed a significant correlation with the gross pathologic and histologic findings.
Development of blood‐compatible elastomers. V. Surface structure and blood compatibility of avcothane elastomers
Authors: Nyilas E. , Ward R. S.
Published: December 2004

The Avcothane 51 elastomer, a member of a series of proprietary materials best characterized as polyurethane/poly(dialkylsiloxane) block copolymers, displays considerable hemocompatibility without any incorporated anticoagulants. In the form of intra‐aortic balloons, the elastomer was implanted in several thousands of cardiac patients without intolerable hematologic effects. Hemocompatibility has been assumed to result from a predominantly dispersion‐type surface force field whose intensity fluctuates within small domains, maintaining adsorbed blood proteins in an unstable state. The relative hemocompatibility of films, which were obtained from a prepolymer solution cast on substrates impenetrable to the solvent, is a function of the effective surface molecular structure. This can vary as a function of preparative conditions (temperature and rate of evaporation), and has been correlated with an anisotropic distribution of the silicone component in cured films. The concentration of this component in surface layers was quantified independently by IRATR spectroscopy and electronmicroprobe analysis, giving consistent results. An IRATR index, which is computed from the ratio of absorptivities measured at 13.00 and 12.62 μ and is inversely proportional to the relative silicone content of surface layers, was found to correlate with the apparent hemocompatibility determined by different in vitro methods. Optimized reproducible hemocompatibility is attained by strict process controls.
Interaction of living cells with polyionenes and polyionene‐coated surfaces
Authors: Rembaum A. , Senyei A. E. , Rajaraman R.
Published: December 2004

Polyionenes have been shown recently (A. Rembaum, Appl. Polym. Symp. No. 22, 299, 1973) to produce the following biological effects: (1) bactericidal action, (2) formation of insoluble complexes with DNA and heparin, (3) neuromuscular blocking action, (4) cell aggregation and lysis, and (5) cell adhesion.

In the present study, polyionenes of various structures (mainly I3,3, I6,10) were used as molecular probes to gain an understanding of the cell surface phenomena of adhesion on glass‐ and polyionenes‐treated surfaces. Since tumor cells show different surface cell properties, including an increase in the anodic mobility, they bind preferentially to polyionene‐treated surfaces. Normal human diploid WI‐38 cells were found to adhere at a lower rate than SV‐transformed WI‐38 cells. However, cell spreading was accelerated in both cases.

A study of the interaction of polyionenes in solution in vitro and in vivo and polyionenes covalently bound to polymeric microspheres with leukemic murine EL 4 cells and normal thymocytes showed specific cytotoxity towards the leukemic cells.
Histological reaction to various conductive and dielectric films chronically implanted in the subdural space
Authors: Loeb G. E. , Walker A. E. , Uematsu S. , Konigsmark B. W.
Published: December 2004

Thirty different test patches of various thin film materials were chronically implanted in the subdural space of cats to determine their suitability as components for proposed neuroprosthetic devices. In particular, materials employed by the microelectronics industry were screened, and reactions were found to be quite dependent on specific formulations or surface preparations of otherwise similar materials. A nonspecific but severe complication of pressure necrosis under thin films that spontaneously roll and curl in vivo was noted.
A new antithrombogenic heparinized polymer
Authors: Miyara Hajime , Harumiya Noriho , Mori Yuichi , Tanzawa Hiroshi
Published: December 2004

A new antithrombogenic polymer was synthesized by photoinduced graft copolymerization of both a hydrophilic polymer and a cationic polymer to hydrophobic poly (vinyl chloride) copolymer, and by quarternizing and heparinizing the obtained graft copolymer.

For polymers of various compositions obtained by the method described above, chemical composition, water absorption, membrane potential, and quantity of adsorbed heparin were determined and antithrombogenicity evaluated in vivo. Thus, it has been found that the polymer of excellent antithrombogenicity has a negative membrane potential, a moderate elution rate of heparin, adsorbs heparin in a quantity of approximately 15 wt‐%, and has a degree of water adsorption of about 30 wt‐%. Also, measurement of membrane potential was very useful for the estimation of the quantity of the adsorbed heparin and its change with time.
Polytetrafluoroethylene–N‐Vinylpyrrolidone graft copolymers: Affinity with plasma proteins
Authors: Boffa G. A. , Lucien N. , Faure A. , Boffa M. C. , Jozefonvicz J. , Szubarga A. , Mandon P. , Larrieu M. J.
Published: December 2004

N‐vinylpyrrolidone was grafted onto films, grains, and tubes of polytetrafluoroethylene (PTFE) using a radiation procedure. By controlling the experimental conditions, it was possible to obtain an analogous grafting percentage on films and grains. Kinetic grafting onto a tube might be used under certain conditions to preserve both size and water tightness. Poly(vinylpyrrolidone) (PVP)‐grafted material became hydrophilic and slightly swollen according to the grafting percentage obtained

A scanning electron microscope (SEM) analysis of polymer surfaces showed preferential polymerization sites at a low radiation dose. A regular, velvet‐like surface was obtained for a high grafting percentage induced at a low radiation intensity

Biological properties of PTFE were compared before and after PVP grafting. PTFE appeared to be a nonreactive polymer with respect to the blood‐clotting proteins. No significant change was observed using different granulometric sizes of PTFE grains, and its noteworthy inertness was preserved after PVP grafting

Interactions between polymer surfaces and human plasma proteins were analyzed using 125I‐isolated proteins. Fibrinogen and immunoglobulins have a high affinity for PTFE; on the other hand, albumin was weakly adsorbed on the polymer surface

Marked changes in protein adsorption were observed after PVP grafting. Hydrophilic group grafting induced an increase of albumin adsorption and a decrease of fibrinogen adsorption. Prothrombin affinity was not significantly affected by modified PTFE

Studies of serum protein adsorption using solid‐phase radioimmunoassays were developed with monospecific and polyvalent antisera. After incubation of the whole serum protein and polymer, immunoglobulins were found to exhibit the major part of bound protein radioactivity on the polymer surface. No evidence of increasing adsorption of immunoglobulins from rabbit serum after immunization by PTFE or PTFE/PVP was observed. The immunoglobulin adsorption was submitted to a copetitive effect with the other serum proteins. It was possible to postulate the competitive action of albumin, particularly after biological property change induced by chemical grafting.
Fabrication of large arrays of cortical electrodes for use in man
Authors: Klomp G. F. , Womack M. V. B. , Dobelle W. H.
Published: December 2004

Techniques are described for fabrication of electrode arrays for stimulation and/or recording from a human cerebral cortex. These arrays may be neurosurgically inserted (with or without a Penrose drain) in the course of a conventional craniotomy or craniectomy, and are easily removed without reopening the ineision. Termination of the connecting wires in a special percutaneous pedestal has also permitted chronic implantation. The contacts and connecting wires are made of pure platinum embedded in a Teflon ribbon‐cable matrix. The choice of materials combines biological acceptability, electrochemical stability, and integrity of the insulation, but imposes special fabrication procedures.