bluuebunny/crossref_metadata_2025 huggingface dataset:
Tissue reaction to three ceramics of porous and non‐porous structures
Authors: Hulbert S. F. , Morrison S. J. , Klawitter J. J.
Published: December 2004

In this investigation, ceramics were studied to determine their role as rigid, abrasive implants in soft, living tissue. Discs and tubes of three ceramics, CaO·Al2O3, CaO·TiO2, and CaO·ZrO2, were introduced as porous and non‐porous structures into muscle and connective tissue sites in rabbits. The animals were observed grossly to determine the duration of redness and swelling following surgery, and samples were retrieved at 1 week, 3 months, 6 months, and 9 months after implantation. A mild, acute inflammatory response immediately followed the implantation of all three materials in both the porous and non‐porous forms. Histological sections of the ceramics and surrounding tissue, cut and stained for light microscopy, demonstrated the absence of inflammatory cells and revealed the normal morphology and organization of the cells present around all types of implants tested. Tissue around discs of porous ceramics healed faster and exhibited thinner fibrous encapsulations than with impervious discs of the same material. Healthy fibrous connective tissue with an ample blood supply occupied those implants with pores of 45–100 mμ, and even more rapidly filled the samples with a 100‐ to 150‐μ pore size. The tissue ingrowth and tight adherence to the porous samples was believed responsible for the more moderate response to porous implants. No adverse responses of any kind were observed, except in a very few, atypical specimens.
Attachment of bone to threaded implants by ingrowth and mechanical interlocking
Authors: Predcki Paul , Auslaender B. A. , Stephan J. E. , Mooney Vert L. , Stanitski Carl
Published: December 2004

Threaded cylindrical samples of titanium, aluminum oxide, and titanium flame‐sprayed with Al2O3 were implanted trasnversely in dog femurs. Half the samples were pushed into slightly oversize holes in the femurs, and half were screwed into slightly undersize holes. After implantation for 4 weeks, the former samples were pushed out and the latter torqued out.

Metallographic and electron microprobe examination showed that essentially complete ingrowth of new trabecular bone had occurred into the threads of all samples. The highest push‐out shear strengths, (of the order of 2000–2500 psi), were obtained with sharp V‐threads on surface oxidized titanium at 56 thread/inch. In these samples, the fracture path was mostly through the new bone rather than along the bone/implant interface. Torque‐out shear strengths were substantially lower (300–1000 psi) with the fracture path following the macroscopic bone‐implant boundary.
Reduction of tissue and bone adhesion to cobalt alloy fixation appliances
Authors: Homsy Charles A. , Stanley Rufus F. , Anderson M. Sidney , King Joe W.
Published: December 2004

The cobalt‐based alloy containing approximately 30% chromium and 5% molybdenum is widely used for the fabrication of internal fixation appliances. This alloy exhibits superior corrosion resistance in the presence of body fluid because of a durable and rapidly formed surface layer of chromium oxide. Although biocompatible, clinical use of this alloy appears to have been complicated by relatively great adhesion of tissue and bone to the metal. The adhesion engenders considerable difficulty when removal of an applicance should become necessary.

It was hypothezied that this adhesion derives from the ceullular growth proceeding within the microporosity of the metal surface; the growth proceeds efficiently because of relatively low levels of cytotoxic metal ions released at the metal surface. In order to limit adhesion, polytetrafluoroethylene polymer (PTFE) was used to virtually eliminate surface microporosity and to substantially reduce metal surface free energy.1 One of the efficient techniques was to lap the metal surface with a solid piece of PTFE.

A series of eighteen 12– to 22–kg dogs were used to evaluate the above thesis. Control and treated cobalt alloy plates and screws were used to fix induced longbone fractures in the same animal. Also, five animals received implants on decorticated iliac crests. The histological data for control (untreated) plates showed that in nine of the eleven experiments bone was demonstrated closely adjacent to the surface of the appliance. However, in seven of these cases fibrous tissue was also present to a substantial degree. The presence of bone correlated with generally increased difficulty in removal of the plate. On the other hand, the results with treated implants showed that in ten of eleven cases the appliances were grossly encapsulated with fibrous tissue and were relatively easy to remove.
Intravascular radiopaque catheters in the dog: Tissue reaction and possible lead loss
Authors: Winders Robert L. , Rostorfer Howard H. , Blackschaffer Bernard C.
Published: December 2004

Male mongrel dogs were divided into two groups and placed in urine collection cages for 24‐hr urine samples. One group was implanted with sterile radiopaque polyethylene catheter and stainless steel guide wire fragments in the venous vasculature via an incision in the left femoral vein and the remaining group in the arterial vasculature via the left femoral artery. The catheter fragments, made radiopaque by an admixture of 25% lead oxide and 75% polyethylene, were located by roentgenograms and along with the guide wire fragments removed at necropsy 18–46 weeks following implantation. Gross and microscopic tissue lesions consisted of fibrous tissue tubes and slings which completely enclosed and anchored the fragments and intimal hyperplasia with fibrous tissue organization of thrombi, respectively. Tissue staining techniques for lead, catheter fragment weights, blood lead levels, and urine lead content all revealed no evidence of lead loss from the catheter fragment implants.
Poly(ethyleneglycol methacrylate) as a material for hemodialysis
Authors: Špaček P. , Kubín M.
Published: December 2004

Diffusion and permeation coefficients of urea, creatinine, and sodium chloride in poly(ethyleneglycol methacrylate) swollen to equilibrium in water were determined; on their basis, geometrical dimensions of a simple artificial kidney are estimated and discussed.
Precipitation hardening in gold‐platinum alloys containing small quantities of iron
Authors: Fuys R. A. , Fairhurst C. W. , O'Brien W. J.
Published: December 2004

Gold‐10% platinum alloys with additions of minor amounts of iron exhibits age hardening characteristics. Maximum hardness and maximum hardening rate occurred in gold‐10% platinum alloys containing 0.16 wt% iron. Electron microscopy techniques employing replicas of Au‐Pt‐Fe alloys revealed intragranular and intergranular precipitation phenomena occured in the overaged condition. Electron diffraction and x‐ray diffraction methods showed the intergranular phase to be an ordered face‐centered cubic structure.
Splat‐cooled alloys in the Ag‐Sn‐Cu system
Authors: Johnson L. B. , Otani H. , Neary M. J. , Hauck J. W. , Heaven T. M. , Regenitter R. J.
Published: December 2004

Strength, dimensional change during setting, and corrosion resistance have been measured for amalgams prepared from splat‐cooled alloys of different compositions in the Ag‐Sn‐Cu system. The amalgam with optimum values of these properties was made from the alloy containing 60 at. % Ag, 25 at. % Sn, and 15 at. % Cu. Tensile strengths for amalgams from this alloy were about 8000 psi, dimensional change during setting near zero, and corrosion resistance was good.

X‐Ray diffraction showed that the γ1 and γ2 phases formed during the early stages of setting but that the γ2 phase had essentially disappeared after about 24 hr. At the latter time Cu6Sn5 was present.
Studies of the stability and toxicity of zinc polyacrylate (polycarboxylate) cements (PAZ)
Authors: Peters Walter J. , Jackson Robert W. , Smith Dennis C.
Published: December 2004

Zinc polycarboxylate cement (PAZ) was shown to actively bond to 45Ca in vitro, with maximum uptake occurring at a Ca+2 concentration of 0.2 mg/ml. When the resultant PAZ‐45Ca complex was subsequently incubated in the presence of high levels of unlabeled Ca+2, there was an exchange between the 45Ca bond to the cement and the Ca+2 in solution. When PAZ prepared using 65Zn was incubated with high levels of Ca+2, there was no exchange between the Ca and the 65Zn. 14C‐PA failed to be taken up by L‐cells in tissue culture, during 16 division cycles. Using radioactive PAZ prepared from 14C‐PA, the PA moiety of the cement was shown to be extremely insoluble and stable in vivo.
Experimental analysis of ceramic‐tissue interactions. A morphologic, fluoroescenseoptic, and radiographic study on dense alumina oxide ceramic in various animals
Authors: Griss Peter , Krempien Burkhard , von Andrian‐Werburg Hanns Frhr. , Heimke Gunther , Fleiner Roland , Diehm Theo
Published: December 2004

Two types of dense Al2O3 ceramics (99.6% purity, 96% purity) were tested in the following fields of interest.

Wear resistibility using a pin and disk method under distilled water and human synovial fluid. Both types showed minimal initial corpuscular wear.

Biocompatibility of ceramic wear particles in mice and rats after injection by different ways. The crystal material is permanently deposited in macrophages, after transport via lymphpatic and blood vessels also in the RES without chronic inflammatory and progressive fibrotic response.

Under moderate stress conditions ceramic plates are fixed firmly by new bone formation within 2–3 months according to tetracycline label studies of bone growth in rats.

A new ceramic total hip prosthesis with two different socket designs for cement free fixation in bone is proposed and used in sheep experiments. The results of a 4 month experiment is presented showing firm fixation of the prosthesis under full stress conditions.
The foreign body reaction—an experimental protocol
Authors: Coleman D. L. , King R. N. , Andrade J. D.
Published: December 2004

A comprehensive protocol is presented for the in vivo evaluation of soft tissue foreign body reactions to surgical implants. A number of methods of evaluation and quantitation of the tissue reaction to implants are presented and discussed. A strong plea is made for semi‐quantitation of tissue reactions, rather than relying on subjective, qualitative methods.
A comparison of soft tissue reaction to silastic and absorbable suture material
Authors: Toranto I. Richard , Salyer Kenneth E. , Nickell William B.
Published: December 2004

Alloplastic implants in reconstructive surgery have many varied applications. The problem of extrusion in certain areas has not been totally resolved. Our intent was to design and develop a composite alloplastic implant which would be fixed to local tissues by fibrous ingrowth. Small amounts, less than 5% by weight, of a biodegradable substance with either Silicone type A or clear dental acrylic were used. Laboratory rats were implanted subcutaneously with sterile prostheses measuring 21 mm × 1 mm. The biodegradable portion consisted of presently available absorbable suture‐polyglycolic acid, chromic catgut, and plain catgut in small particles. The implants were harvested at six weeks and three months and objectively evaluated for tissue fixation and fibrous reaction. In our model, the composite alloplastic prosthesis of chromic catgut and Silicone type A established superior fixation by fibrous ingrowth with a minimum of fibrous capsular thickness.
Calcium‐phosphate magnesium‐aluminate osteoceramics
Authors: McGee Thomas D. , Wood Jack L.
Published: December 2004

Ceramic materials for permanent implantation in osseous tissue, called osteoceramics, were based on an equimolar mixture of Ca3(PO4)2 and MgAl2O4. Tooth roots with dense regions and with regions of controlled porosity for tissue ingrowth were made from the material. They were implanted submucosally in the mandible and maxilla of dogs. Tissue response was aceptable and strong attachment occurred. Thin sections are presented showing the interface of the alveolar bone and the prosthesis.
Establishment of a theoretical base‐design of a lower extremity prosthesis
Authors: Newell P. H. , Krouskop T. A. , Jendrucko R. J. , Chakraborty B. K.
Published: December 2004

A conceptual model that relates the phenomenological stimuli responsible for bone remodeling has been developed as a preliminary exercise in a study designed to quantify Wolff's Law. In this regard, a set of thermodynamic and chemical kinetic equations have been formulated and their use in describing and predicting the formulation of crystalline hydroxypatite is presented.

As a parallel activity, a macrocopic structural analysis of the bone‐pylon interface has been conducted using a finite element representation and the results of this investigation are discussed as they relate to establishing a set of pylon design criteria.

Finally, a modular, endoskeletal prosthetic system is described. The design of this appliance is based on the concept of total cosmesis and provides the present amputee with increased comfort and functionality as well as providing a system that can be effectively interfaced with a bone pylon when direct skeletal attachment (DSA) becomes a clinically accepted procedure.
Materials in maxillofacial prosthetics
Authors: Chalian V. A. , Phillips R. W.
Published: December 2004

Maxillofacial prosthetic materials are classified in two main groups: extraoral and intraoral prosthetic materials.

Among extraoral prosthetic materials vinyl chloride polymers, poly (methyl methacrylate), silicone, and polyurethane are discussed for use in facial prosthetics. At present silicones and polyurethane materials are considered most desirable for their strength, even though both are somewhat difficult to color.

Intraoral prosthetic materials include silicones, poly (methyl methacrylate), Tantalum, Ticonium, Vitallium, and Titanium mesh materials. Here again, silicone is particularly valued for its tissue tolerability. Metallic mesh materials have the advantage of permitting granulated tissue to migrate through the mesh.

The criteria for ideal materials in maxillofacial prosthetics are as follows: extraoral prostheses should not irritate the surrounding tissues, yet it should be strong enough about the periphery to endure. It should be translucent, light weight, easy to process, and easy to manipulate prior to processing. It should be resistant to various chemicals such as ether, oil and to sunlight, heat, and cold.

Implantable prosthetic materials must not be physically modified by the soft tissue; must not be capable of inciting inflammatory or foreign body reaction; must be chemically inert, noncarcinogenic, capable of resisting strain, easy to construct, and easy to sterilize.

Progress toward meeting these criteria depends upon cooperation between laboratory and clinical researchers.
Molecular aspects of calcified tissue
Authors: Walton A. G.
Published: December 2004

The detailed relation between primary, secondary, tertiary, and ultrastructure of collagen is presented. Electron micrographs of stained collagen are described in terms of specific peptide location. Data relating to the interaction of polysaccharides, notably chondroitin‐6‐sulfate, and proteoglycan and collagen are reviewed and a model for connective tissue developed. The relationship between such structure and that of calcified tissue is examined and some new data pertaining to the mechanism of calcification are introduced.
The load‐deformation characteristics of connective tissues
Authors: Kenedi R. M.
Published: December 2004

Following the classification of tissues according to their “dominant” and “interactive” components the paper surveys their load‐deformation behavior, highlighting in particular the significance of time dependence. This leads to a discussion of the implant/tissue interaction in which the complexity that could be created by varying load and deformation time rates at the interface is explored.
The role of biomechanics in oral implantology
Authors: Knoell A. C. , Grenoble D. E.
Published: December 2004

This paper begins with a brief historical review of the field of biomechanics applied to oral implantology. Based on the current status of development, a set of generalized biomechanical requirements are presented covering analytical, experimental and clinical considerations. The current biomechanics status and requirements are then used to derive a three part role for the biomechanics of oral implantology. The expected benefits to be gained from implementing this role are outlined.
A thromboresistant surface by enzyme immobilization
Authors: Nguyen An‐Lac , Wilkes Garth L.
Published: December 2004

A process is described for binding brinolase, a fibrinolytie enzyme, to a solid support. Evidence is presented to prove the activity and stability of the bound enzyme at physiological conditions of pH and temperature. A scheme is suggested for preparing suitable material onto whose surface the fibrinolytic enzyme can be bound in an approach to creating a thromboresistant surface.
Porous Vitallium in implant surgery
Authors: Cameron H. U. , Pilliar R. M. , Macnab I.
Published: December 2004

The reactivity of porous Vitallium in vivo and in vitro has been tested. Samples have been implanted subcutaneously and intramuscularly in Wistar Rats for periods of up to two years. No untoward tissue reaction was found, and the samples did not show any evidence of corrosion. Samples have also been tested in an electrochemical cell. No increase in reactivity for unit surface area was found.

It is therefore concluded that porous Vitallium is a safe, inert material, and is acceptable for use in clinical practice.
Study of pig valve heterografts by X‐ray diffraction
Authors: Huc A. , Planche Cl. , Weiss M. , Mannschott Ph. , Chapin F. , Chabrand D.
Published: December 2004

The study of collagen fibers by X‐ray diffraction, utilizing semiquantitative indices for appraisal of “structuration” and “orientation” was applied to 30 aortic valve grafts. These grafts, of pig origin, were studied in the fresh state, after tanning with aldehydes, and after having been implanted in patients for at least 18 months. It was shown that the collagen fibers are preferentially orientated parallel to the transverse axis of the valve cusps, and that this arrangement, enhanced by tanning, had a tendency to disappear in the post‐implantation samples. The structuration index which concerns the fibril network was also augmented by tanning, and was found a little high or slightly diminished in post‐implantation cusps. Evidence for a new compound, probably fibrin, was found in the diffraction patterns of implanted cusps, but crystallized calcium was noticeably absent.
The development of an abrasion testing machine for dental materials
Authors: Harrison Alan , Lewis T. T.
Published: December 2004

Wear testing should be an important part of the investigations into the physical and mechanical properties of some dental materials. It has, however, largely been ignored because of conflicting and unreproducible results. It was decided, therefore, to review the work done by other researchers and to examine the human masticatory cycle, and then present new parameters to design and construct a new dental abrasion testing machine. This new machine is described in detail and its capabilities briefly illustrated.
The influence of compositional variations on bone ingrowth of implanted porous calcium aluminate ceramics
Authors: Graves G. A. , Noyes F. R. , Villanueva A. R.
Published: December 2004

Sixteen ceramic specimens were implanted in the femur of mature rhesus monkeys. The specimens consisted of four groups of a basic calcium aluminate composition with additions of 5, 10, 15 and 20 wt% phosphorous pentoxide (P2O5). The increasing amounts of P2O5 caused variations in the resorption rate, microstructure and surface characteristics of the implant. The influence of these variables on bone and tissue growth within and about the implant was investigated.

After sacrifice the ceramic‐bone specimens were studied by a tetracycline‐based histological analysis, scanning electron microscopy and energy dispersive analysis.

The results indicate an increase in mesenchymal cell proliferation, fibrous and bone tissue formation at the ceramic tissue interface and within the implant with increasing concentrations of P2O5.

The results obtained from the study did not furnish sufficient evidence to differentiate between the direct chemical influence the increasing P2O5 had on osseous tissue formation or the indirect influence that may have resulted from its effect on the ceramic microstructure and morphology.
Fractography of poly(methyl methacrylates)
Authors: Kusy R. P. , Turner D. T.
Published: December 2004

For convenience in clinical manipulation, it is the practice to fabricate PMMA prostheses from mixtures of powder and monomer. When the monomer is subsequently polymerized an unusual 2‐phase polymeric material results in which grains of PMMA are dispersed in a matrix of the same polymer.

The mechanical properties of the 2‐phase materials are inferior in certain respects relative to 1‐phase polymers.

The purpose of the present work is to evaluate the failure of 2‐phase materials by microscopical examination of their fracture surfaces. A granular microstructure was clearly distinguishable and a distinction made between materials which fail exclusively by transgranular fracture and others which additionally exhibit intergranular fracture.

In order to interpret markings observed on the fracture surfaces of the complex 2‐phase systems a study was made of the influence of molecular weight on the fractography of 1‐phase PMMA. Molecular weight was reduced by degradation of samples by exposure to γ‐rays. The spacing of periodic rib markings on fracture surfaces was found to decrease with molecular weight and this relationship used to provide an estimate of the molecular weight of polymer in the matrix of 2‐phase materials.
Porous, heat cured poly (methyl methacrylate) for dental implants
Authors: Gettleman Lawrence , Nathanson Dan , Myerson Richard L. , Hodosh Milton
Published: December 2004

The use of polyl (methyl methacrylate) for tooth replica implants, as developed by Hodosh, is described as to indications, ingredients, and fabrication technique. Laboratory testing of this material for mechanical and thermal expansion properties, and porosity content were determined as a function of foaming agent and anorganic bone particle content.
Growth kinetics of γ2 crystals on mercury‐plated Ag3Sn
Authors: Okabe T. , Hines A. L. , Hochman R. F. , Sims L. O.
Published: December 2004

Previous work has shown that needles of γ2 crystals form when mercury is plated on the surface of an Ag3Sn specimen. In the present study, the growth kinetics of γ2 needles were investigated from room temperature to 50°C for varying amounts of plated mercury. Straight‐line relationships between crystal length and the square root of the time of growth showed that the growth rate is diffusion controlled. The growth rate increased with temperature up to 40°C but decreased at higher temperatures. Further, as the temperature was increased, fewer γ2 crystals formed and their growth length decreased. This demonstrates that a number of competing factors are involved in the growth process at high temperatures.
Deposition of blood cells on collagen and cuprophane membranes
Authors: Schwartz A. , Stenzel K. H. , Kohno I. , Ast D. , Miyata T. , Rubin A. L.
Published: December 2004

Dogs were dialyzed with collagen and cuprophane membranes, human renal failure patients were dialyzed with cuprophane membranes, and samples of the membranes were observed by scanning electron microscopy at different time periods. Fixation was done in glutaraldehyde and cacodylate buffer, and samples were dried at the critical point. All cellular elements were well preserved and appeared viable. Cuprophane adsorbed platelets almost selectively in dog dialyses, whereas collagen adsorbed a smaller number and more heterogeneous group of cells. In contrast to these findings, when cuprophane was used in clinical dialyses, the cell population was predominantly polymorphonuclear leukocytes.
The interactions of thrombin with borosilicate glass surfaces
Authors: Waugh David F. , Anthony Linda J. , Ng Helen
Published: December 2004

Borosilicate glass (G) and commercial poly(methyl methacrylate) (PMM) surfaces were examined at pH 7, monovalent ionic strength 0.14 and 22°C. Thrombin concentrations ranged from 6 × 10−9 to 5.2 × 10−8M. Decreases in thrombin concentration in 10 ml vessels were determined by clotting time assay. Adsorption to PMM vessels is small. These were examined to establish the validity of the method. For G‐vessels, the terminations of initial rapid decreases, associated with adsorption equilibrium, are accounted for mainly by an average isotherm having an association constant of 1.8 × 107 1./mol. Adsorption equilibrium is accompanied by a slower rate of decrease consistent with the surface denaturation of 2.5%/min of adsorbed molecules.

Molecules remaining adsorbed to the surfaces of 1 mm i.d. G‐capillaries were examined using the sequence of thrombin adsorption, buffer washing for times tw, removal of buffer and introduction of a fibringen aliquot for determination of effective surface thrombin concentration by a capillary clotting time. Most adsorbed molecules (<90%) essentially desorb within tw = 2 min, a second class (>8%) desorb in tw ∼30 min, and members of additional classes are still present after tw = 1440 min. For all of the properties examined, there is a small variance between vessels taken at the same time from the same batch, and a larger variance between groups of vessels taken at different times from the same batch or from different batches.
Corrosion of surface defects in fine wires
Authors: Rentler R. M. , Greene N. D.
Published: December 2004

Defects were observed on the surfaces of various fine diameter wires commonly used in biomedical applications. These surface irregularities were viewed at high magnifications using a scanning electron microscope which has a much greater depth of field than normal light microscopy. Defects include scratches, pits, and crevices, which are the result of commercial wire drawing practices. Corrosion test results show that imperfections can serve as sites for localized corrosion attack which could lead to premature failures.
Hydrophilized polyethylene catheters
Authors: Kaganov A. L. , Štamberg J. , Synek P.
Published: December 2004

Complications arising in the application of polyethylene catheters in surgery may be reduced by their surface hydrophilization. This study describes a combination of chemical transformation and coating with a hydrophilic gel. Modified catheters were tolerated well by the patients and in contrast with the original catheters, they did not lead to the formation of thrombi or phlebitis.
Electrical stimulation of bone growth into porous Al2O3
Authors: Weinstein Allan M. , Kalwitter Jerome J. , Cleveland Thomas W. , Amoss Donald C.
Published: December 2004

Porous, cylindrical, high alumina, ceramic structures were fabricated for implantation in the superior third of canine femoral medullary canals. Implant durations of one, two, four, and eight weeks using three animals per time period were studied. A constant current (10 μA) power supply was used to attempt to stimulate bone growth into the porous ceramic structures. Osseous tissue ingrowth was evaluated using a mechanical push‐out test, microradiography, and histological thin sectioning. The interfacial shear strength and tissue microstructure was studied as a function of implant residence site and implant residence time.

The results indicate that initially the proximal implants have a higher interfacial shear strength, however, after eight weeks of implantation the distal implants have a shear strength about twice that of the proximal implants. This trend is observed for both the electrically stimulated and nonstimulated specimens. The 10 μA current level used in this investigation was found to have a small but significant effect on shear strength increasing it at implantation times of less than eight weeks.
A comparative study of the early vascularization of porous carbon and bone as a graft
Authors: Lozano Alexander J. , Cestero Herman J. , Salyer Kenneth E.
Published: December 2004

Utilizing rats as a model, it was demonstrated that both iliac crest bone and porous carbon disks, when used as onlay grafts, become vascularized as early as 3 days. There is no significant difference between the two. The soft tissues, periosteum, and recipient bone are all capable of supplying vascularization to the graft or implant.
An in vitro investigation of the anodic polarization and capacitance behavior of 316‐L stainless steel
Authors: Sutow Elliott J. , Pollack Solomon R. , Korostoff Edward
Published: December 2004

Determinations were made of how the corrosion‐resistant properties of the passive film on 316‐L stainless steel are influenced by the material's mechanical and surface states, and the variable pH and PO2 conditions of the interstitial fluid.

Cold‐rolled and annealed specimens were surface‐prepared, commercially and in the laboratory, respectively, as if for orthopedic implantation. Passive film behavior was studied by the anodic polarization and pulse‐ potentiostatic capacitance methods. The pH and PO2 of the Ringer's test solution were varied to include interstitial fluid values occurring postoperatively and onto recovery.

The anodic polarization behavior of all specimens was found to be pH‐ and PO2‐independent. Breakdown potentials of annealed specimens were 800–950 mV (SCE), in contrast to previously reported values of approximately 350 mV. This substantial increase is related to the influence of surface preparation and, in particular, to the optimization of electropolishing time which acts to produce a microscopically smooth surface, free of debris and disarrayed material. Capacitance behavior of annealed material for potentials > 400 mV was consistent with a model involving the entry of chloride and metal ions (mostly Fe) into the passive film. This entry is related to the onset of pitting.
Biochemical response to Dacron vascular prosthesis
Authors: Noishiki Yasuharu
Published: December 2004

Dacron vascular prostheses were examined under both light and electron microscopes from 1 to 1184 days after implantation in the thoracic aorta of 96 dogs. Each Dacron fiber of the implanted prostheses was found to be covered with a single layer, which closely resembled the outer half leaflet of plasma membrane. The control experiment in vitro revealed that when untreated Dacron fibers were dipped into a solution of lecithin, the fibers became covered with monomolecular leaflets of lecithin micelles. On the basis of the in vivo and in vitro findings, it was suggested that the implanted Dacron fibers of vascular prosthesis were covered at an early stage with a monomolecular micelle layer of phospholipid or phospholipoproteins originating from the living body, and thus became adapted to the living body.
The bone–metal interface following hip nailing
Authors: Cameron H. U. , Fornasier V. L.
Published: December 2004

In order to establish a base line for tissue reaction in relationship to loaded implanted foreign materials that might be used for comparison with new materials, the interface between the trabecular bone in the femoral head and hip nails has been studied in 20 specimens.

The interface consists of four distinguishable layers: a cellular layer at the surface, a layer of fibrovascular connective tissue, a layer of collagenous connective tissue and/or fibrocartilage, and a peri‐implant bone plate. Even 10 years after insertion of the nail this interface remained cellularly active, the activity presumably being related to the different modulus of elasticity between the metal and the surrounding trabecular bone.
Mechanical strength of acrylic bone cements impregnated with antibiotics
Authors: Lautenschlager E. P. , Marshall G. W. , Marks K. E. , Schwartz J. , Nelson C. L.
Published: December 2004

Admixing of several antibiotic powders which were insoluble in methyl methacrylate did not decrease the compressive and diametral tensile strengths of two acrylic bone cements when tested after setting for 1 day and after leaching 40 days in water at 37°C. When antibiotics were added as water solutions, the included water resulted in a significant decrease in these bulk mechanical properties.

Storage in water for 40 days caused surface irregularities only on specimens of the set antibiotic admixtures. Approximately 0.5% of the admixed dosage of these water‐soluble antibiotics could be leached from the set cements. The observed surface channels, presumably left by the loss of antibiotic, suggest further study of surface‐sensitive mechanical properties may be needed.

The bulk mechanical strengths presented here are conclusive only for the particular combinations of antibiotics and cements investigated, and should not be generalized at this time to any or all antibiotic admixtures or other mechanical properties.
Further experimental and clinical experience with aluminum oxide endoprostheses
Authors: Salzer M. , Zweymüller K. , Locke H. , Zeibig A. , Stärk N. , Plenk H. , Punzet G.
Published: December 2004

This paper describes the design principles of a new endoprosthesis made of dense aluminum oxide (Al2O3) and implanted without bone cement. Mechanical tests and animal experiments have proved the sufficient mechanical strength of the bone–prosthesis connection as well as the biocompatibility of the material. So far, 12 tumor patients selected according to strict indication criteria have been operated on. Both the clinical–radiologic and the first histological findings available are encouraging. Special reference is made to the first fully ceramic total hip joint endoprostheses implanted in a human without bone cement.
Interactions of synthetic and natural surfaces with blood in the physiological environment
Authors: Bruck Stephen D.
Published: December 2004

Efforts to explain blood compatibility with synthetic and natural surfaces based on a single parameter or a single biological test procedure have either been unsuccessful or led to misleading generalizations. The problem reflects the complex interdependence between material's properties, the composition and properties of blood, and in vivo biorheological conditions. Among the initial events that occur when materials contact blood is the very rapid adsorption of plasma proteins; this process effectively influences the subsequent interactions with the formed blood elements, especially the platelets with the proteinated surfaces.

In the case of natural surfaces, when the endothelium is damaged, collagen may become exposed that may cause the activation, adhesion, and aggregation of platelets leading to thrombosis. Current evidence indicates that the platelet‐aggregating ability of collagen depends on its “multimeric” or fibrillar structure, rather than on the activation of the platelet‐bound enzyme system. Under normal conditions, the flowing blood is probably not in direct contact with endothelial cells that line the blood vessel walls, but with an adsorbed layer of plasma proteins. Should a formation of a multilayer of plasma proteins occur following the initial adsorption of a monolayer, this process could be influenced by changes in the solubility of the proteins, especially fibrinogen, the solubility of which is quite low in plasma. The hypothesis is proposed that such changes may be intimately related to the electrical properties of proteins present in the vascular wall and in blood. It is possible that these properties play a much greater role in thrombogenesis and in the problem of blood compatibility than is currently appreciated.

Considering synthetic polymers, a number of these have been prepared that exhibit little adverse effects on blood components and, at the same time, retain their physical properties for various periods of time in the physiological environment. These combined biological and physical properties make them useful for various prosthetic and other biomedical applications in surgery and therapy.
Effects of polymer surface molecular structure and force‐field characteristics on blood interfacial phenomena. I
Authors: Nyilas E. , Morton W. A. , Cumming R. D. , Lederman D. M. , Chiu T.‐H. , Bailer R. E.
Published: December 2004

To quantify the effects of major surface structural factors influencing interfacial reactions induced by polymers in native blood, model surfaces of solvent‐cast films of two analogous poly (ether urethanes) and three homologous polyamides (nylon 4, 6/6, and 12) were exposed ex vivo to canine blood under the well‐defined hemodynamic conditions of the Stagnation Point Flow Experiment. The selected surfaces allow for incremental changes in properties and were characterized by their “Composite Surface Free Energy Function,” γ′s, which describes the surface force field as the sum of the mean dispersion (\documentclass{article}\pagestyle{empty}\begin{document}$ \bar \gamma $\end{document}sd) and polar (\documentclass{article}\pagestyle{empty}\begin{document}$ \bar \gamma $\end{document}sp) contributions and is computed from wettability spectra obtained with ultrapure diagnostic liquids. Blood interfacial effects were measured by the shear‐limited diameter of the white cell circle formed around the stagnation point, the flow parameter at which symmetric aggregation occurred, and the surface‐number density of platelets, [Ps], remaining adherent under fixed conditions. At identical flows, within each group of polymers, both the WBC‐circle diameter and [Ps] scale with \documentclass{article}\pagestyle{empty}\begin{document}$ \bar \gamma $\end{document}sp/γ′s, implying that (1) only the magnitude but not the interaction mechanism varies as a function of incremental structural and surface changes, (2) the primary determinant of surface‐induced effects is the polar force contribution, and (3) the magnitude of γ′s is secondary if \documentclass{article}\pagestyle{empty}\begin{document}$ \bar \gamma $\end{document}sd/γ′s is sufficiently great.
On the fate of methyl methacrylate in blood
Authors: Rijke A. M. , Johnson R. A. , Oser E. R.
Published: December 2004

The fate of methyl methacrylate in fresh human blood was investigated in vitro by using gas chromatography. It was found that methyl methacrylate is present in cells in concentrations twice as large as in plasma, but it disappears exponentially with time at a rate that is at least 10 times faster than that in cells. The rate constant in cells is very small or even zero. The half‐life of methyl methacrylate in whole blood is 3 hr at 20°C. Gas chromatography is a convenient method for the rapid determination of methyl methacrylate levels in blood.
Inhibition and enhancement of platelet aggregation by collagen derivatives
Authors: Kay W. W. , Kurylo E. , Chong G. , Bharadwaj B.
Published: December 2004

Rat tail tendon tropocollagen rapidly caused the aggregation of blood platelets coincident with collagen multimerization. Several long‐chain alkyl derivatives of collagen, however, were completely unable to induce platelet aggregation even at unusually high concentrations. These collagen derivatives varied in their polymerization properties, and the polymerization of tropocollagen derivatives was shown not necessarily to be a prerequisite for platelet aggregation. These collagen derivatives may enhance the antithrombogenic properties of collagenbased prostheses. A short‐chain derivative, collagen‐glycine ethyl ester, profoundly enhanced platelet aggregation in the absence of any measurable polymerization. This derivative may be useful as a growth‐promoting burn dressing.
Membrane permeability for inorganic phosphate ion
Authors: Moise O. , Sideman S. , Hoffer E. , Rousseau I. , Better O. S.
Published: December 2004

The need for a more efficient removal of inorganic phosphate ions from the blood of uremic patients has led to the quest for blood‐compatible semipermeable membranes with a high permeability for phosphate ions. Commercial hemodialysis membranes, various hydrogel‐type membranes and a number of collodionbased charged membranes were compared. Positively charged collodion membranes were found most promising for future application in hemodialysis or hemoperfusion systems.
A study of the corrosion of dental amalgam using the ring‐disk electrode
Authors: Gal‐Or Leah , Bruckenstein Stanley , Carter J. M.
Published: December 2004

The rotating ring‐disk electrode technique has been applied to the study of anodic dissolution of dental amalgam in a simulated saline solution.

The electroactive domains of the silver, tin, and mercury couples (the main constituents of the amalgam) were determined from current–potential curves obtained at a rotating gold‐disk electrode in solutions containing salts of the respective metals. Subsequently, anodic currents were applied to a rotating amalgam‐disk electrode and the soluble products produced were identified using a concentric gold ring electrode, i.e., using the rotating gold‐ring, amalgam‐disk electrode. Species generated at the amalgam disk are transferred to the gold ring by convective diffusion. Tin ions were found to be the only soluble species generated at the amalgam disk. No evidence for dissolution of other components was found. The selective dissolution of tin from the amalgam is also consistant with potential shifts observed in repetitive current‐potential curves of an amalgam disk.

This study provides a direct proof for the selective dissolution of tin during corrosion of dental amalgam in an in vitro environment.
Biocompatibility testing of polymers: In vivo implantation studies
Authors: Gourlay Stuart J. , Rice Robert M. , Hegyeli Andrew F. , Wade Clarence W. R. , Dillon James G. , Jaffe Howard , Kulkarni R. K.
Published: December 2004

An in vivo method is described for screening polymeric materials for biocompatibility. The test is based on grading acute and subacute tissue reactions at 7 and 28 days, respectively, following implantation in rats. The method is reproducible and reliable. It is designed to provide uniform test criteria for biocompatibility assessment in the early phases of the development of surgical implant materials.
Surface finish of dental composite restorative materials
Authors: Tolley L. G. , O'Brien W. J. , Dennison J. B.
Published: December 2004

Five composite filling materials were finished using six finishing procedures currently in clinical use. The average roughness produced by each procedure was measured by means of a Surfanalyzer with four replications for each procedure on each of the five materials. Statistical analysis indicated that finishing with silicon carbide disks produced the smoothest surfaces. Acceptable surfaces were obtained with stones or with burs. Use of an alumina paste after a green stone‐white Arkansas sequence did not produce a significant improvement.

Two processes of filler particle abrasion were distinguished by means of electron microscopy: wear and shear. Fracture striations indicated particle shear.

The roughest surfaces were produced by the use of a diamond instrument which is contraindicated. Acceptable finishing procedures for the composite materials tested include silicon carbide disks for accessible areas or 12 fluted finishing burs for more inaccessible areas.
Strength of a dense alumina ceramic after aging in vitro
Authors: Krainess F. E. , Knapp W. J.
Published: December 2004

Rods of dense alumina ceramic were aged in Ringer's solution for time periods up to 12 weeks, with half of the rods being aged while mechanically stressed. Pyrex‐type glass rods were similarly tested for comparison purposes. No reduction in flexural strength was observed in dense alumina rods after aging, providing no permeation of the solution into the ceramic occurred. However, a marked reduction in flexural strength was experienced by alumina rods, nominally dense and nonporous, into which some permeation of the saline solution was observed after aging; the largest reduction in strength occurred in such rods aged while mechanically stressed. The results indicate the importance and advantage of using densely sintered alumina ceramics as implants for optimum structural performance over an extended time period.
Tissue reaction to ceramic implant material
Authors: Harms J. , Mäusle E.
Published: December 2004

The biocompatibility of alumina ceramic was tested by means of macrophage cultures, intraperitoneal (i.p.) and intramuscular (i.m.) application of powdered particles in rats, and by implantation of solid samples in the paravertebral muscles and the condylus of femur. No acute cytotoxicity was found in macrophage cultures. The i.p. and i.m. application of powdered particles in the beginning showed a granulocytic reaction, later followed by a histiocytic reaction. Also, the morphological changes in the organs of reticulo histiocytic system (RHS) are shown. In the solid sample implantation, the fibrogenetic stimulus is measured by morphological analysis of the connective tissue membrane around the sample. The importance of the individual cell observation by transmission‐electron microscope (TEM) examination is evidenced. The experimental results are compared to the environmental reaction of smaller animal‐adapted prostheses and prostheses having been implanted in human patients. Good biocompatibility is confirmed by these investigations; also regarding central position of the macrophages, the environmental reaction due to implant material is shown.
In vitro evaluation of hemolytic and cell culture toxicity potential of residual ethylene oxide in selected medical materials
Authors: Jones Alan B.
Published: December 2004

The hemolytic potential of pure ethylene oxide in solution was evaluated as a function of initial ethylene oxide concentration in three test systems, diluted whole blood in isotonic saline, erythrocytes washed and resuspended in isotonic saline, and erythrocytes washed and resuspended in isotonic phosphate buffer. Concentrations of 2 mg/ml (2000 ppm) were necessary before cell lysis was observed in either of the isotonic saline systems. This value increased to 10 mg/ml (10,000 ppm) in the isotonic buffer system. Efforts have been made to correlate the hemolysis and cell culture toxicity of residual ethylene oxide in five medical materials to the toxicity of pure ethylene oxide. Only materials exhibiting a low order of inherent toxicity showed any correlation. In poly(vinyl chloride) tubing containing 1.8 and 2.1 mg ethylene oxide per gram of materials, a small amount of toxicity was seen in the cell culture system but toxicity was absent in the hemolysis test.
Mechanical properties of antibacterial silicone rubber for hydrocephalus shunts
Authors: Van Noort R. , Bayston R.
Published: December 2004

In an effort to find a solution to the serious problem of bacterial colonization of cerebrospinal‐fluid shunting devices, room‐temperature and heat‐vulcanizing silicone rubbers were impregnated with gentamicin sulphate. The effects on the mechanical properties of the two rubbers were studied. Results show that the tensile strength and extensibility of the room‐temperature‐vulcanizing silicone rubber reduced with increasing concentration of the drug. For the heat‐vulcanizing silicone rubber, the tensile strength was also found to decrease with increasing drug content. The extensibility after an initial reduction at low concentrations was found to increase at drug concentrations in excess of 10 mg/g. Nevertheless, the changes in mechanical properties measured are considered not to be so great as to preclude the application of drug‐impregnated silicone rubbers to cerebrospinal‐fluid shunting devices.