bluuebunny/crossref_metadata_2025 huggingface dataset:
An evaluation of bone growth into porous high density polyethylene
Authors: Klawitter J. J. , Bagwell J. G. , Weinstein A. M. , Sauer B. W. , Pruitt J. R.
Published: December 2004

The purpose of this investigation was to study bone growth into porous polyethylene rods as a function of time and pore structure. Previous studies have indicated the biocompatibility of solid polyethylene materials which are currently being used clinically. Porous polyethylene rods were implanted in the femurs of mongrel dogs which were sacrificed four, eight, and 16 weeks postoperatively. The implants were then sectioned and examined histologically and microradiographically. Quantitative techniques were employed to determine the amount of bone ingrowth as a function of time and pore size. The pore structures of the materials were evaluated using optical microscopy and mercury intrusion porosimetry.

The results of this investigation have demonstrated that porous polyethylene is capable of accepting bone growth into pores as small as 40 μm. The optimum rate of bone ingrowth was observed in pore sizes of approximately 100 to 135 μm, with no increase in the rate of bone ingrowth observed in samples possessing larger pore sizes. No adverse tissue response was found at implant times up to 16 weeks in pore sizes of 100 μm or larger.
Materials for selective tissue heating in a radiofrequency electromagnetic field for the combined chemothermal treatment of brain tumors
Authors: Moidel R. A. , Wolfson S. K. , Selker R. G. , Weiner S. B.
Published: December 2004

A technique of creating localized heating by implanting metallic materials in the brain and inserting the head into a radiofrequency electromagnetic field is described. The heating properties of various materials for implantation were studied, and the two best materials were carbon steel rods and Hysterloy (1000 and 655 cal/g‐min, respectively). Heating of these materials was done primarily by eddy current since their heating rates were significantly affected by their shapes and orientation in the field, rods oriented parallel to the field producing the most heat. There is evidence that warmer cells have a greater uptake of chemotherapeutic agents. This suggests a combined therapeutic approach employing localized brain heating in conjunction with systemic or intrathecal chemotherapy. In this way, large doses of chemotherapeutic drugs might be concentrated in a warmed brain tumor while toxicity is prevented by keeping the rest of the brain and body hypothermic.
A statistical treatment of fatigue of the cast Co‐Cr‐Mo prosthesis alloy
Authors: Miller H. L. , Rostoker W. , Galante J. O.
Published: December 2004

Fatigue tests have been conducted on commercially produced cast Co‐Cr‐Mo alloy in tension‐tension while surrounded by a physiological solution at 37°C The data have been analyzed by statistical techniques to yield an allowable stress such that there is 95% confidence of less than one failure in 1,000 after 5 × 107 cycles of stress fluctuation. These results are valid for a substantially sounder material than may be common in commercial use and therefore a more conservative allowable stress probably ought to be used for design purposes.
Adhesion of platelets to artificial surfaces: Effect of red cells
Authors: Brash J. L. , Brophy J. M. , Feuerstein I. A.
Published: December 2004

Adhesion of Platelets to several polymer‐ and protein‐coated glass surfaces has been studied in vitro. The apparatus consists of a cylindrical probe rotating in a test tube containing the platelet medium and allows close control of fluid shear and mass transport. Suspensions of washed pig platelets constitute the basic platelet medium, and can be modified by adding back red cells and plasma proteins. Adhesion is measured via 51Cr‐labeling of platelets. In the absence of red cells, identical low levels of adhesion were seen on all surfaces and saturation was reached within 2 min. In the presence of red cells, adhesion was greater. Saturation on all surfaces except fibrinogen and collagen again occurred within 2 min. The adhesion levels on polymer surfaces and glass were indistinguishable, while those on albumin were lower and those on fibrinogen were higher. Collagen was the most reactive surface. It did not equilibrate within 15 min, and kinetic data indicated a platelet diffusivity strongly dependent on hematocrit. These effects were attributed to rotational and translational motion of the red cells causing increased diffusion and surface‐platelet collision energy.
Flame‐sprayed alumina on stainless steel for possible prosthetic application
Authors: Baldwin C. M. , Mackenzie J. D.
Published: December 2004

Various methods of roughening type 316 stainless steel substrate surfaces for flame‐spraying alumina (Al2O3) were investigated and tested for the best alumina‐to‐metal bond strength. Best strength values were obtained by means of roughening via anodic polarization pitting of the stainless steel. Subsequent in vitro testing indicated a severe loss in bond strength following exposure to aerated Ringer's solution. It is suggested that the utilization of flame‐sprayed devices has potential in orthopedic prostheses, but precautions must be observed.
Evaluation of a bioglass‐coated Al2O3 total hip prosthesis in sheep
Authors: Griss P. , Greenspan D. C. , Heimke G. , Krempien B. , Buchinger R. , Hench L. L. , Jentschura G.
Published: December 2004

A bioglass‐coated fully dense alumina total hip was evaluated in sheep without using polymer bone “cement.” After 3 months following surgery, both the acetabular cup and femoral stem component were firmly attached to bone. Histologic and radiographic analysis of the bone–implant interface showed regions of woven and even lamellar bone formation where high load transmission occurred. In regions of low loading or poor fit, a pseudosynovial fibrous lining was present.
Craniofacial contour defect reconstruction with a Dacron/urethane composite: An alloplastic tray for bone induction fabrication and application
Authors: Leake Donald L. , Habal Mutaz B.
Published: December 2004

An alloplastic tray made of poly(ethylene terephthalate) cloth mesh and poly(ether urethane) used in conjunction with cancellous bone‐chip grafts is the basis for this new method for reconstructing facial osseous contour defects. The tray can be prefabricated in quantity and at low cost for standard defects, such as discontinuity defects of the mandible or for chin augmentation. It can be custom‐fabricated for specific defects in individual patients as, for example, gunshot wounds to the forehead. The materials were chosen because of their known histocompatibility, the ease of fabrication, and because the materials can be molded to form esthetic contours. They can be easily modified at the time of surgery. Sterilization is by autoclaving.

Initial studies were undertaken in mongrel dogs where mandibular discontinuity defects in the range of 2–4 cm were reconstructed. In man, the technique has been used to reconstruct discontinuity defects of the mandible ranging in size from 1.5–12 cm in 16 patients. Atrophic mandibular alveolar ridges have been augmented using this technique in 7 patients, thus providing an adequate alveolar ridge for dentures. Two patients with defects of the skull secondary to gunshot wounds have had frontal bone restoration using this method.Reconstructions of the ear, the chin, and the orbital floor are currently being evaluated. This technique overcomes many problems of esthetic contour reconstruction and combines the use of autogenous cancellous pmarticulate bone and a tissue‐compatible synthetic composite material.
Interaction effects among cortical bone, cancellous bone, and periodontal membrane of natural teeth and implants
Authors: Widera G. E. O. , Tesk J. A. , Privitzer E.
Published: December 2004

Following the initial successes of Goldberg and Gershkoff (Dental Digest, 5, 11, 1947) with the placement of subperiosteal implants, interest in all types of implants emerged. As an aid to the evaluation of various designs and materials without resorting to clinical testing, finite element analyses are being conducted by a number of researchers to determine the stress system induced in bone. The present study investigates the effects of variation in the thicknesses of the periodontal membrane and cortical bone and of the model boundary on the stresses developed around a natural tooth or a tooth‐shaped implant. The results show that strong effects due to the variation in these parameters can be expected. As a consequence, the problem of the analysis of any single implant must consider additional factors. These can influence overall implant design and may eventually help to explain what could appear as anomalies in clinical test results.
Biocompatibility of nitinol alloy as an implant material
Authors: Castleman L. S. , Motzkin S. M. , Alicandri F. P. , Bonawit V. L. , Johnson A. A.
Published: December 2004

The biocompatibility of nitinol alloy as a potential implant material was investigated through in vivo studies on beagles. A high‐purity alloy was fabricated into prototype bone plates and implanted into the femurs of beagles. Commercial cobalt–chromium (CoCr) alloy bone plates served as reference controls, and additional control data were obtained from beagles subjected to “sham” operations.

The bone plates were removed from the animals and examined after exposures of 3, 6, 12, and 17 months. There was no evidence of either localized or of general corrosion on the surfaces of the bone plates and screws. Gross clinical, radiological, and morphological observations of the tissue at the implantation sites during the autopsies uncovered no signs of adverse tissue reactions resulting from the implants. Histological analyses were performed on samples of muscle and bone adjacent to the implantation sites, and of tissues removed from such organs as the liver, spleen, brain, and kidneys. No significant differences were noted between samples taken from controls and those taken from dogs exposed to the implants. Neutron activation analyses were carried out on suitable samples. The analysis data suggest that there is no metallic contamination in the organs due to the implants; however, there does appear to be some chromium contamination from the CoCr alloy implants in the adjacent bone.

On the basis of the totality of the data, it is concluded that nitinol alloy is sufficiently compatible with dog tissue to warrant further investigation of its potential as a biomaterial.
In vitro effects of bone cement on S. aureus growth and phagocytosis and glucose metabolism of macrophage: A preliminary study
Authors: Shoji Hiromu , Nicastro Joseph F. , Rovere George D. , Gristina Anthony G.
Published: December 2004

A preliminary study of the effects of Surgical Simplex, mixed for various time periods, was performed on S. aureus growth rate, and phagocytosis and glucose metabolism of macrophage in vitro. Quantitatively, no significant effects of the mixture on S. aureus growth rate were observed. The cement mixed for less than 4 min tended to cause adverse effects on phagocytosis rate and hexose monophosphate shunt activity of macrophage. This information may not be directly applicable to in vivo, but in vitro the cement mixture in a certain situation can cause decreased phagocytosis and hexose monophosphate shunt activity of macrophage.
A unified mathematical model for diffusion from drug–polymer composite tablets
Authors: Fu J. C. , Hagemeir C. , Moyer D. L. , Ng E. W.
Published: December 2004

The derivation and experimental verification of a unified mathematical model for the estimation of drug release rate from drug–polymer composite tablets are presented. Cylindrical coordinates are utilized in the solution of the diffusion equation for a three‐dimensional system. The model is applicable to tablets that range from the shape of a flat disk (radius > thickness) to that of a cylindrical rod (radius < thickness). The general solution for the fraction of drug released at a time t is

This approach to a three‐dimensiona system, utilizing cylindrical coordinates, presents a comprehensive method for the estimation of drug release rates from sustained release tablets with drug distributed homogeneously throughout a polymer matrix. The calculated and experimental drug diffusion rate of pyrimethamine from pyrimethamine‐silicone rubber composite tablets that range in shape from that of a disk to a cylinder, and of hydrocortisone from EVA, poly‐caprolactone, and PVA terpolymer, are compared.
Fracture characteristics of acrylic bone cements. I. Fracture toughness
Authors: Freitag Thomas A. , Cannon Stephen L.
Published: December 2004

The vital first phase of the overall materials study to protract the life of the total joint replacements is the identification of the fracture toughness and fatigue properties of bone cements. Information gained from fatigue testing, performed in a manner which simulates in vivo conditions, and fracture toughness, which is a measure of the propensity of a crack to propagate, is the first step towards the prediction of the life of the total joint replacement. This study is concerned with the fracture toughness of Zimmer and Simplex‐P cold‐curing bone cements.

Following cement fabrication conditions which closely approximate clinical procedures, fracture toughness testing was conducted on cement specimens which were immersed in bovine serum at 37°C in order to simulate in vivo conditions. In addition, a similar study was completed on specimens, tested in air at ambient temperature for purposes of comparison. Results of this procedure, when analyzed by a Student's t‐test at the 95% confidence level with eight degrees of freedom, indicate that both Zimmer and Simplex‐P exhibit a higher fracture toughness in the simulated physiological environment.

In order to determine whether the addition of barium sulfate to these cements compromises the fracture toughness, the above described testing rationale was repeated, indicating the existence of a complicated relationship between the different testing environments and barium sulfate. The importance of these results lies in the fact that an increased fracture toughness indicates that a cement will inherently exhibit a greater degree of resistance to the propagation of cracks, which could contribute to the ultimate failure of the total joint replacement.
Carbon fiber‐reinforced bone cement in orthopedic surgery
Authors: Pilliar R. M. , Blackwell R. , Macnab I. , Cameron H. U.
Published: December 2004

A tougher, more fatigue‐resistant bone cement consisting of short, highmodulus carbon fibers dispersed randomly in normal poly(methyl methacrylate) bone cement has been developed. Fatigue and impact tests are reported that demonstrate the superior fracture resistance and prolonged load‐carrying ability of this system.

The use of this carbon fiber‐reinforced bone cement in the treatment of a pathological fracture of the femur associated with neoplastic disease of the bone is reported. The tougher cement has provided long‐term stability of the fracture.
New types of synthetic infusion solutions. III. Elimination and retention of poly‐[N‐(2‐hydroxypropyl)methacrylamide] in a test organism
Authors: Šprincl L. , Exner J. , Štěrba O. , Kopeček J.
Published: December 2004

The elimination and retention of a new, fully synthetic plasma prosthesis of Czechoslovak origin under the working name of Duxon (poly[N‐(2‐hydroxypropyl)methacrylamide]) was investigated in experiments on rabbits by using a 14C‐labeled polymer. Results published earlier on elimination have been confirmed and extended. Retention was examined after repeated application. The effect of molecular weight prevailed both in elimination and in retention. Polymers of lower molecular weights, which possess a good therapeutical effect, are not permanently deposited in the organism.
Role of protein and fatty acid adsorption on platelet adhesion and aggregation at the blood–polymer interface
Authors: Kim S. W. , Wisniewski S. , Lee E. S. , Winn M. L.
Published: December 2004

Thrombus formation on a foreign surface is a complicated process, involving many factors. However, there is little doubt that a foreign surface adsorbs plasma proteins upon blood contact and that the nature of this adsorbed layer may determine the mechanism of platelet adhesion and aggregation. The adhesion and aggregation of platelets play an important role in the initial events of thrombus formation on a foreign surface. In this work, adsorption studies using human blood plasma were done on several polymer surfaces. Some drugs which prevent platelet adhesion were utilized to verify the proposed mechanism for platelet adhesion which includes glycosyl transferase reaction. Also, adsorption and release of fatty acid salts, including fatty acid‐bonded albumin, were investigated at different polymer interfaces. It is postulated that adsorbed fatty acid salts are released from the surface upon contact with plasma to form a high local concentration of fatty acid, and that this fatty acid suspension would cause platelet aggregation at the interface.
Reactions of human platelets with microspheres of poly(hydroxymethyl methacrylate) and polyacrylamide
Authors: Kronick Paul L. , Rembaum Alan
Published: December 2004

We have studied the contact interaction of platelets with hydrogels. In the form of microspheres, 0.6–1.0 μ, poly (glycol methacrylate) (poly HEMA) and poly (methyl methacrylate) beads cause platelets to aggregate at concentrations of about 108 beads/ml. Polyacrylamide and (20/80) poly (acrylamide–HEMA) copolymer were ineffective in aggregating platelets. The admixture of 20% methacrylate to polyHEMA rendered the beads inactive. Blood plasma components other than fibrinogen were found essential to the interaction of the beads with platelets. Near‐infrared spectra of the hydrogels polyacrylamide and polyHEMA showed the water hydrogen bonds to be the same for both and different from those in pure water. The monomer HEMA is an inhibitor of platelet aggregation and the release reaction at levels of 0.1%. It is concluded that the two hydrogels have different blood compatibilities, which depend more on the network structures than the water structures in the respective gels.
Mechanochemical studies of enzymatic degradation of insoluble collagen fibers
Authors: Huang C. , Yannas I. V.
Published: December 2004

A mechanochemical method was developed for studying the enzymatic degradation of insoluble collagen fibers. The method involves stretching the collagen fiber to a fixed extension in the presence of a solution of collagenase and measuring the rate of relaxation of the force induced on the fiber. In this work, bacterial collagenase was used for reasons of availability. We observed invariably an exponential decrease in force with respect to time. The slope of the linear plot of logarithm of the force versus time was taken as a measure of the rate of enzymatic degradation. This rate was found (a) to vary linearly with collagenase concentration; (b) to be maximized at pH 7–8; (c) to vary with temperature according to the Arrhenius relationship in the range 10–56°C; (d) to be reduced to varying extent by addition of EDTA, o‐phenanthroline, 2,3‐dimercaptopropanol, and D, L‐cysteine; (e) to be minimal when the strain on the fiber was ca. 4%; (f) to be increased dramatically by denaturation of the collagen fiber; and (g) to be reduced by an increase in the crosslink density of the collagen fiber. Except for the effect of strain, which can not be conveniently sudied by existing methods, these results are consistent with those observed by other methods for the study of the enzymatic degradation of collagen. The mechanochemical method is, however, uniquely suited to monitor continuously the enzymatically induced decay in the stress‐bearing ability of collagen fibers. It has also been found useful in the design of collagenous implants with specified resistance to enzymatic degradation in vivo.
Reactions of the articular capsule to wear products of artificial joint prostheses
Authors: Willert H.‐G. , Semlitsch M.
Published: December 2004

Examination of a great number of tissue samples taken from the newly formed capsules surrounding artificial joints reveals small particles of prosthetic material. Abraded from the joint by wear and tear, these particles of plastic, metal, and acrylic cement initiate a foreign‐body reaction and result in the formation of granulation tissue, including macrophages and foreign‐body giant cells. Typical features of tissue reactions exist for each of the materials from which prostheses are made. The consequent formation of scar tissue produces a thickening of the capsule, which, in turn, may cause a reduction in the mobility of the joint.

In small amounts, the foreign‐body particles are eliminated via the perivascular lymph spaces. Where this transport system is insufficient to handle the volume, however, the foreign‐body response may extend to the whole environment surrounding the joint. In such cases, there may be loosening of the cemented prosthetic parts because of deterioration of contiguous bone anchors by the tissue membrane lining the bone cement.
Immobilization of enzymes on slowly soluble carriers
Authors: Torchilin V. P. , Tischenko E. G. , Smirnov V. N. , Chazov E. I.
Published: December 2004

The preparation and some properties of microspheres composed of oxidized polysaccharides and some vinyl polymers are described. The microspheres contain immobilized enzyme and can be slowly solubilized in water solutions, thereby releasing active a enzyme into the surrounding medium. The kinetic characteristics of the immobilized enzyme bound with a fragment of matrix after complete solubilization are unchanged, but the enzyme exhibits high thermostability. These preparations could have a wide range of medical applications, e.g., to form a drug “depot” directly in an affected organ.
Interactions between segmented polyurethane surfaces and the plasma protein fibrinogen
Authors: Stupp S. I. , Kauffman J. W. , Carr S. H.
Published: December 2004

Surfaces of a segmented polyurethane were varied by casting on poly(ethylene terephthalate) (PET) and glass substrates, and were characterized through infrared‐attenuated total‐reflection spectroscopy (ATR). Surfaces cast on glass substrates showed a higher content of polyether segments, whereas those cast on PET contained a higher relative concentration of aromatic segments. Adsorption, and possible conformational changes of fibrinogen, were found to be more substantial on polymer surfaces having a higher content of polyether segments. It is concluded that the relatively good blood compatibility of segmented polyurethanes is partly due to the presence of peptide‐like bonds on aromatic segments.
Properties of heparin–poly (methyl methacrylate) copolymers. II
Authors: Labarre D. , Jozefowicz M. , Boffa M. C.
Published: December 2004

A heparin–poly (methyl methacrylate) copolymer in which heparin has been covalently bound was studied. This copolymer showed no release of heparin but presented heparin‐like anticoagulant activity when suspended in plasma. After contact with plasma, the copolymer lost part of its antithrombin activity which could be restored by a high ionic‐strength medium. Because of its solid form, this copolymer offers new possibilities for producing interesting anticoagulant surfaces.
Effect of collagen crosslinking on the rate of resorption of implanted collagen tubing in rabbits
Authors: Chvapil M. , Owen J. A. , Clark D. S. , Koorajian S. , Goodman A. P.
Published: December 2004

Collagen tubes were tanned with glutaraldehyde for different periods of time. Some were oxidized with periodate and sterilized with either 60Co (1.5 Mrad) or propylene oxide. The tubes were coated with polyfilamentous polyester fabric, filled with x‐ray contrast material, and implanted subcutaneously in rats and rabbits. Rate of resorption was ascertained by x‐ray procedure of progressive leakage of contrast material.

A close relation between tanning time of the collagen fabric‐combined prostheses and rate of their resorption in subcutis was found in both rats and rabbits. In rabbits, however, the implants were resorbed at a significantly faster rate than in rats. No effect of oxidation of collagen on the resorption was observed. Collagen tubes tanned for shorter time periods and sterilized with propylene oxide were more resistant to degradation than those sterilized with irradiation. This difference was absent, however, with material tanned for longer times.

The mechanism of resorption of implanted collagen tubes was studied by morphological methods. The role of inflammatory cells in resorption is documented. The paper indicates the advantages as well as limits of the x‐ray method of studying the resorption rate of biodegradable materials.
Skin replacement with bioplast fibrin in ophthalmology
Authors: Tapasztó István , Kerényi Géza
Published: December 2004

The study includes 40 cases of skin replacement performed by an ophthalmologist over a period of 4 years. An absorbable implant material, Bioplast fibrin, was used as a graft following the extirpation of 12 eyelid tumors, the treatment of eight fresh, destructive skin injuries, and the removal of deforming scars around the eyes, in 20 cases. The biocompatible implant provided barrier properties preventing infection or excessive fluid loss. The resorption rate was adjusted to 3–4 weeks. These grafts were gradually replaced by new epithelial tissue growing in from the periphery of the wound edge. The new tissue had the elasticity and cosmetic appearance of surrounding skin. Thus, small periorbital skin tumors can now be removed without the necessity of doing a split thickness skin graft to cover the defect.
Influence of a functional dynamic loading on bone ingrowth into surface pores of orthopedic implants
Authors: Ducheyne P. , De Meester P. , Aernoudt E. , Martens M. , Mulier J. C.
Published: December 2004

The present status of skeletal fixation of permanent orthopedic implants by poly(methyl methacrylate) (PMMA) is discussed. It is proposed that alternatives to the acrylic cement can improve the skeletal fixation. The present paper is concerned with the fixation method by bone ingrowth into pores of the implant surface.

Two different implantation models have been designed to investigate the influence of load bearing upon ingrowth in surface pores of the implant: intramedullary nails as a means of fixation of a femoral pseudarthrosis and hinged knee prostheses. In each animal, implants with identical material characteristics (pore size, density, and thickness of the porous layer) but different loading conditions were used: one implant was “statically” loaded, the other “dynamically.” This procedure allows the evaluation of ingrowth with regard to load bearing only.

Two different mean pore sizes, viz., 87 and 110 μm, have been used with the two models. After an 8 week implantation period, bone ingrowth was evident for the statically loaded implants. Calcified tissue ingrowth was, however, not observed in the dynamically loaded implants. The discrepancy in bone ingrowth behavior between the statically and the dynamically loaded implants has been attributed to 1) the gross movement or the micromovement existing at the bone prosthesis interface and 2) the fact that the critical mean pore size for ingrowth with static loading is smaller than the one with dynamic loading.

The experimental implantations allow still another conclusion: the results suggest that designs of present clinical prostheses fixed by bone cement cannot be used with the alternative fixation by bone ingrowth unless the deisgn has been changed in a fundamental way. Mechanical factors as well as the phenomenology of bone ingrowth fixation account for this conclusion.
A polymethacrylate–silica composite material for dental implants
Authors: Hodosh M. , Shklar G. , Povar M.
Published: December 2004

A study has been carried out on the structure and surface texture of a new dental implant material composed of silica microspheres (3 or 5 wt %) and poly(methyl methacrylate). A recently developed composite material composed of vitreous carbon microballoons and poly(methyl methacrylate) has proven highly successful in clinical use, but the black color presents aesthetic problems at the gingival margin. The new material was developed in order to reproduce the many desirable qualities of the vitreous carbon‐polymethacrylate composite, while omitting the black color. Square wafers (10 mm × 10 mm × 1 mm) were studied, with the surface sandblasted in half of the specimens. Light microscopy revealed an even spacing of spherical configurations throughout the material. Scanning electron microscope studies revealed a finely porous surface with many large craters in the sandblasted specimens.
A total internal‐reflection technique for the examination of protein adsorption
Authors: Watkins Robert W. , Robertson Channing R.
Published: December 2004

A Total internal‐reflection fluorescence (TIRF) technique for examining protein adsorption at solid‐liquid interfaces is described. For the representative case of adsorption of bovine γ‐globulin onto silicone rubber, the applicability of the technique to several important aspects of protein adsorption phenomena is demonstrated. Specifically, in addition to the tightly adsorbed protein layer observed herein and previously by many others, the presence of a loosely adsorbed protein layer was also noted under conditions of either static or flowing protein solutions. Taking advantage of the continuous real‐time measurements possible with TIRF, a rate constant for the protein adsorption step during laminar flow was estimated at both 25 and 37°C. These results serve to demonstrate that the TIRF technique represents a significant and versatile new tool for the study of protein adsorption phenomena.
Adsorption of plasma proteins on hydrophobic surfaces. I. Albumin and γ‐globulin
Authors: Bagnall Robert David
Published: December 2004

The adsorption of albumin and γ‐globulin from solution at the liquid/air and liquid/liquid interfaces has been studied by the pendant drop technique as a model for the solid‐liquid system. It is concluded that each protein adsorbs in a constant manner at the air, isooctane, and methylene iodide interfaces at equilibrium (1 hr), and the surface tension components of the protein layer presented to the hydrophobic phase have been found. The range of hydrophobic surfaces for which such constants behavior might be expected has been deduced, and it is shown that most common polymers lie within this range. A new model for protein adsorption is proposed, and the implications for biomaterials are discussed.
Carbon fiber‐reinforced carbon as a potential implant material
Authors: Adams D. , Williams D. F. , Hill J.
Published: December 2004

A carbon fiber‐reinforced carbon is being evaluated as a promising implant material. In a unidirectional composite, high strengths (1200 MN/m2 longitudinal flexural strength) and high modulus (140 GN/m2 flexural modulus) may be obtained with an interlaminar shear strength of 18 MN/m2. Alternatively, layers of fibers may be laid in two directions to give more isotopic properties. The compatibility of the material with bone has been studied by implanting specimens in holes drilled in rat femora. For a period of up to 8 weeks, a thin layer of fibrous tissue bridged the gap between bone and implant; but this tissue mineralizes and by 10 weeks, bone can be observed adjacent to the implant, giving firm fixation. Potential applications include endosseous dental implants where a greater strength in the neck than that provided by unreinforced carbon would be advantageous.
“Floating‐socket” total shoulder replacement: Anatomical, biomechanical, and surgical rationale
Authors: Buechel Frederick F. , Pappas Michael J. , DePalma Anthony F.
Published: December 2004

A prosthesis based on a new concept of gleno‐humeral motion has been developed and clinically tested for the past 2 years. The “floating‐socket” total shoulder replacement contains a nondislocatable, dual spherical bearing system consisting of a small sphere within a larger sphere with their centers offset to provide the physiologic “floating fulcrum” for mechanically advantageous motion. This geometric configuration allows a prosthetic range of motion in excess of anatomical limits to allow soft tissue structures to limit motion rather than mechanical impingement. The device is constructed from Co‐Cr‐Mo alloy and RCH‐1000 polyethylene such that no metal‐metal contact can occur.

Experimental results in a 112‐lb adult male chimpanzee and six clinical cases have revealed superior fixation strength of both glenoid and humeral components, as well as functional adaptation of the prosthesis without fracture of fixturing bone or prosthetic dislocation.
Development of adhesive pit and fissure sealants using a MMA resin initiated by a tri‐n‐butyl borane derivative
Authors: Nakabayashi Nobuo , Masuhara Eiichi , Mochida Ei , Ohmori Ikuo
Published: December 2004

A new adhesive fissure sealant, which consists of a solution of 3% 2‐hydroxy‐3‐β‐naphthoxypropyl methacrylate in methyl methacrylate (MMA), poly‐MMA powder and an oxidized tri‐n‐butyl borane, a polymerization initiator, was developed. Tensile bond strength between an acid‐etched bovine enamel and a poly‐MMA bar joined by this sealant was 60 kg/cm2, and the value did not decrease much after 30 days immersion in water at 37°C. Penetration of fuchsin into the sealant–enamel interface during a percolation test was not observed. SEM observation showed no voids between the enamel and the cured sealant.
Platelet–foreign surface interactions: Release of granule constituents from adherent platelets
Authors: Whicher S. J. , Brash J. L.
Published: December 2004

The interaction of suspensions of washed pig platelets with nine artificial surfaces (glass, polystyrene, three segmented polyurethanes, and surfaces formed by coating glass with albumin, fibrinogen, γ‐globulin, and collagen) is reported. Platelet adhesion and release from adherent platelets were measured via labeling with 51Cr and 14C‐serot onin. The apparatus was a couette flow device allowing observation of surface‐platelet effects uncomplicated by transport or flow effects. Using a two‐level factorial design the effects of albumin, fibrinogen, red cells, and platelet count on adhesion and release were estimated for each surface.

Comparison of the various surfaces showed that collagen and γ‐globulin are the most reactive (mean adhesion, 34 platelets/1000 μm2, mean release 50% of granule contents). The other surfaces showed lower levels of release (∼25%), indistinguishable one from another. The adhesion levels of two hydrophilic polyurethanes and albumin were low, while those of the remaining surfaces were moderate.

The effect of albumin was to reduce adhesion for the “moderate” group of surfaces. Fibrinogen increased adhesion to nonprotein surfaces and decreased release for collagen and γ‐globulin surfaces. High platelet count increased adhesion to fibrinogen, γ‐globulin, and collagen surfaces. Red cells increased adhesion to all surfaces and increased release for collagen and γ‐globulin.
Evaluation of a precipitation hardened wrought cobalt‐nickel‐chromium‐titanium alloy for surgical implants
Authors: Cahoon J. R. , Hill Liliane D.
Published: December 2004

A Co‐Ni‐Cr‐Ti precipitation hardening alloy is evaluated for use as a surgical implant alloy. Static and fatigue strength studies indicate that the alloy is equivalent, or superior to, present implant alloys. In vitro and in vivo corrosion studies indicate that the material has good general corrosion resistance but may be susceptible to crevice corrosion. However, there appear to be no inherent difficulties in using precipitation hardened alloys for surgical implants and therefore it may be possible to develop a new class of materials possessing ultra‐high strength and excellent corrosion resistance for use in surgical implant applications.
Evaluation of couple/crevice corrosion by prosthetic alloys under in vivo conditions
Authors: Rostoker W. , Galante J. O. , Lereim P.
Published: December 2004

Alloys of cast Co‐Cr‐Mo, wrought Co‐Cr‐W, wrought Co‐Ni‐Cr‐Mo (MP35N), Ti‐6% Al‐4% V, and graphite were incorporated in specimens which simulated both a couple and a crevice corrosion condition. These specimens were implanted in a dog for 30 months. Post‐sacrifice examination showed no substantial evidence of corrosion activity on the surfaces of the metals except for a tarnish film on the titanium alloy specimens. The presence of the tarnish film is taken as some evidence of corrosion activity and this correlated with a thicker average fibrous membrane, cellular activity in and near the fibrous membrane, and some increased vascularity. These must be regarded as preliminary observations.
Ferrographic analysis of wear particles in arthroplastic joints
Authors: Mears D. C. , Hanley E. N. , Rutkowski R. , Westcott V. C.
Published: December 2004

Analysis of aspirated synovial fluid appears to be a useful method for the study of the rates, mechanisms, and biological responses to wear in surgical joint replacements. Ferrography, an industrial technique of magnetic separation of particulate matter from samples of lubricating solutions, allows separation of wear debris from synovial fluid. Bichromatic microscopy and SEM X‐ray analysis permit identification of metallic particles from arthroplastic joints. Polarized light microscopy characterizes and differentiates polyethylene and polymethacrylate debris. The number and morphology of the wear particles in synovial specimens from arthroplastic joints correlate with the rate and the mechanisms of wear, as confirmed by examination of the implant and the adjacent synovial tissue.
Reaction of vaginal tissue of rabbits to inserted sponges made of various materials
Authors: Chvapil M. , Chvapil T. A. , Owen J. A. , Kantor M. , Ulreich J. B. , Eskelson C.
Published: December 2004

Sponges of the same size made of collagen (CS), polyurethane (PU), polyvinylalcohol (PVA) and acetylcellulose (AC) were inserted for 10 days in the vaginas of 22 rabbits. Light and scanning electron microscopy of the vaginal wall and its mucosal lining showed signs of cytotoxicity only with PU and AC while CS and PVA picture did not differ from sham controls. In order to explain the reasons for the toxic effects, all sponges were extracted into aqueous or organic solvent media and analyzed by gas liquid chromatography. Only several minute peaks in organic solvents were found. Extracts of all sponges tested for cytotoxicity in fibroblast cultures showed significant inhibition of H3–thymidine uptake. Nevertheless, extract of collagen sponge was significantly less cytotoxic than the extracts of all other sponges.
Arterio‐venous shunt with percutaneous leads in calves for long‐term in vivo testing of blood‐contact materials
Authors: Grosse‐Siestrup C. , Krautzberger W. , Bücherl E. S.
Published: December 2004

In six calves an extracorporeal arteriovenous shunt in combination with a successful type of percutaneous lead has been implanted. Flow chambers with various test materials can be inserted. Preliminary results show that this shunt can be used for long term tests for evaluation of blood contact material and studies about thrombus formation in an ex vivo setting as well as for permanent blood access for the purpose of various measurements, drug application and for hemodialysis.
A correlation between abrasion resistance and other properties of some acrylic resins used in dentistry
Authors: Harrison A. , Huggett R. , Handley R. W.
Published: December 2004

This investigation studies the relationship of hardness, elastic modulus and scratch width as dependent variables to the abrasion resistance of twenty‐three dental acrylic resins. The multiple correlation R, when all three variables are used as predictors, is 0.727. Because of the significant intercorrelations between the variables themselves a stepwise multiple regression analysis showed hardness as a redundant variable. Abrasive wear can be estimated from the following equation

The deletion of scratch width does not appreciably reduce the standard deviation of the estimate:

The method of curing the specimens conformed to the respective manufacturers' instructions. Abrasion and scratch tests were performed using methods developed by the authors and previously described in the literature, whereas the hardness and elastic modulus results were devised from standard test procedures.

Further research is currently in progress to improve the predictive power of abrasion resistance with additional new variables.
Investigations with bioactivated polymethylmethacrylates
Authors: Hennig W. , Blencke B. A. , Brömer H. , Deutscher K. K. , Gross A. , Ege W.
Published: December 2004

Compound bone cement on a PMMA base with an additive of bioactive glass ceramic particles in different portions and different particle sizes are tested in animal experiments. The tissue reactions to extracorporal polymerized specimens and to in situ polymerized specimens are observed. The experiments with an implantation period up to six months demonstrate a tight bonding between the newly formed osseous tissue and the glass ceramic particles at the interface. The inflammatory reactions in the vicinity of the implant are small. It is the objective of the investigations to improve the adherance of the bone cement at the interface to achieve a more durable anchorage of bone cement in the tissue.
Implant site infection rates with porous and dense materials
Authors: Merritt Katharine , Shafer Judith W. , Brown Stanley A.
Published: December 2004

The infection rate of implant sites bearing porous and dense implants was studied in mice. In the first model (acute infection) the mice were injected with Staphylococcus aureus subcutaneously at the implant site at the time of implantation. In the second (chronic) model the implants were left in place for four weeks for encapsulation or invasion to occur and then the organisms were inoculated. In the acute model the infection rate with the porous materials was greater. In the chronic model after tissue invasion the infection rate with the dense materials was greater. This supports the hypothesis that microorganisms can evade host defense mechanisms if they enter the pores of the implant before tissue invasion, but that once the implant is invaded with host tissue the bacteria are less apt to establish infection.
ESCA studies of surface chemical composition of segmented polyurethanes
Authors: Paik Sung C. S. , Hu C. B.
Published: December 2004

Surface chemical analysis of two commercially available polyurethanes, i.e., Avcothane and Biomer was carried out by electron spectroscopy for chemical analysis (ESCA). The depth which is subject to analysis is in the range of 50–100 Å. The variables studied in this study are the difference in exposure to air or to the mold substrate during the solvent casting process. Model compounds such as a pure polydimethylsiloxane, polyether soft segment and hard segment copolymer were used to identify and assign various ESCA peaks. The air facing surface of Avcothane which is the blood contacting surface is found to be covered mostly with polydimethylsiloxane polymer, with a small amount of polyether soft segment mixed with silicone. Therefore, the hard segment of the polyurethanes is hidden beneath the blood contact surface in Avcothane. In Biomer films, the air facing surface contains a greater concentration of polyether soft segment than the substrate surface. These results are consistent with our previous results obtained by Fourier transform IR internal reflection studies and Auger electron spectroscopy.
In vitro corrosion testing of titanium surgical implant alloys: An approach to understanding titanium release from implants
Authors: Solar Ronald J. , Pollack Solomon R. , Korostoff Edward
Published: December 2004

The excellent corrosion resistance of titanium and its alloys to physiological chloride solutions is well documented. Occasionally, however, titanium compounds have been found in tissue adjacent to titanium implants. These findings were reported to be unrelated to wear processes, suggesting that either the metal or its passive film was dissolving. The unpredictability of these findings further suggests that preimplantation surface treatments and/or variations in the physiological environment may be factors. To determine a mechanism by which titanium can be released from an implant a study was initiated which employed electrochemical techniques, Auger electron spectroscopy (AES), and replica transmission electron microscopy (RTEM). Specifically, the purpose was to characterize the passive film on titanium and Ti‐6Al‐4V, and to determine if there is dissolution of the film or metal in a static unstressed state. Passive film behavior of commercially pure titanium, Ti‐6Al‐4V and nitrided Ti‐6Al‐4V was studied by anodic polarization and pulse potentiostatic capacitance techniques in Ringer's solution at 37°C with and without physiological additions of several amino acids. Solution Po2, pH, and specimen surface finish were varied to include all probable in vivo conditions. In all tests, potentiostatic anodic polarization of each material yielded potential‐current density curves which showed passivity over the entire experimental range. This range greatly exceeded the oxygen‐reduction reversible electrode potential. No breakdown potentials were observed. The passive current density was not significantly affected by varying the experimental parameters. AES as well as charge and capacitance measurements showed that the electrochemical reaction which occurred was growth of the passive film. The data indicated that the effective electrochemical area of each specimen was less than its geometrical area, and was dependent on both pH and surface finish. The findings of this study showed that, under static conditions, titanium and Ti‐6Al‐4V should withstand exposure to physiological chloride solutions at body temperature indefinitely. Furthermore, the findings are consistent with a model of the implant surface inwhich the naturla air oxide that initially forms on an abraded implant surface is comprised of microscopic oxide needles. It is proposed that (i) the needless canbe broken off or dissolved in vivo, providing the source of the titanium sometimes found in tissue adjacent to an implant, and (ii) use of certain pretreatments may remove the needles prior to surgery, resulting in the more common case in which titanium is nto found in the tissue.
Use of fracture mechanics theory in lifetime predictions for alumina and bioglass‐coated alumina
Authors: Ritter J. E. , Greenspan D. C. , Palmer R. A. , Hench L. L.
Published: December 2004

The fatigue behavior of alumina and bioglass‐coated alumina was determined in air and biological test environments by the dynamic fatigue test technique in which strength is measured as a function of stressing rate. The good correlation found between the test data and fracture mechanics theory indicates that fatigue failure is controlled by the slow crack growth of preexisting flaws and that fracture mechanics theory can be used in making failure predictions for alumina and bioglass‐coated alumina in biological environments. Thus, it is believed that lifetime predictions can be made for ceramic implants on the basis of short‐term test data utilizing fracture mechanics principles.