bluuebunny/crossref_metadata_2025_split huggingface dataset:
Midroelectrode studies of stress‐generated potentials in four‐point bending of bone
Authors: Starkebaum W. , Pollack S. R. , Korostoff E. 
Published: December 2004

AbstractA microelectrode technique has been developed to enable the study of stress‐generated potentials (SGP) in bone to a spatial resolution of 5 μm. The technique has been used to measure the electrical potentials as a function of bone micromorphology in four‐point bending. Electric fields ranging from 30 to 103 times greater than is measured by conventional macroscopic methods have been discovered at the Haversian canals for human and bovine cortical bone. The amplitude and direction of the electric field in the osteons depend specifically upon the amplitude and the sign (i.e., compression or tension) of the stress. The implications of this finding with regard to the origin of SGP and their possible physiological significance are considered.
Microelectrode study of stress‐generated potentials obtained from uniform and nonuniform compression of human bone
Authors: Iannacone W. , Korostoff E. , Pollack S. R. 
Published: December 2004

AbstractBy use of a previously developed microelectrode technique, the effect of nonuniform stresses on the stress‐generated potentials (SGP) in bone were studied to a resolution of 5 μm. Comparison was made between uniformly and nonuniformly applied compression of human cortical bone. It was found that the radial electric fields for osteons in a specimen under uniform compression were equivalent, and such specimens possessed no macroscopic SGP; for nonuniform compression, the electric fields of osteons differed, and a macroscopic SGP was measured. The magnitude of the macroscopic SGP thus appears to be dependent upon local stress differences and, hence, on the SGP of local regions.
Degradation resistance of some candidate composite biomaterials
Authors: McKenna G. B. , Bradley G. W. , Dunn H. K. , Statton W. O. 
Published: December 2004

AbstractThe degradation resistance of matrix, fiber and composite systems which we have been studying as candidate orthopedic materials has been examined in two appropriate environments. Both resistance to steam sterilization in an autoclave environment and resistance to a simulated physiologic solution have been studied. In the autoclave study, samples were placed in a pressure cooker at 123°C for differing amounts of time and tested for retention of mechanical properties. Results indicate that most of the materials tested could be autoclaved several times, as along as autoclave times did not exceed 1 hr. Longer autoclave times result in an accelerated degradation and loss of strength of all materials except the polypropylene. Polysulfone degrades after even the shortest autoclave duration. Resistance to the simulated physiologic environment was tested by measuring retention of mechanical properties after immersion times in pseudo‐extracellular fluid (PECF) at 37°C for as long as three years. None of the materials showed any significant changes in properties after immersion in the PECF.
Bone ingrowth and stress shielding with a porous surface coated fracture fixation plate
Authors: Pilliar R. M. , Cameron H. U. , Binnington A. G. , Szivek J. , Macnab I. 
Published: December 2004

AbstractThe extent of bone remodelling under metal fixation plates attached to bone by (i) normal screw fixation and (ii) bone ingrowth into a porous metallic surface underlayer sintered to the metal plate was investigated. Extensive bone remodelling was observed under the integrally bonded porous surface layered plate. This remodelling could be attributed to the more extensive stress transfer from bone to metal plate because of the good bone‐to‐implant bonding. The importance of stress shielding with high stiffness implants is demonstrated.
Porous titanium endosseous dental implants in rhesus monkeys: Microradiography and histological evaluation
Authors: Young F. A. , Spector M. , Kresch C. H. 
Published: December 2004

AbstractArtificial tooth roots with porous surface coatings were fabricated by sintering spherical powder of titanium alloy to solid cylindrical cores. The tooth roots were implanted subgingivally in healed mandibular premolar extraction sites of fifteen Rhesus monkeys. Supracrestal abutments were screwed into pretapped holes in the superior aspect of the primary subgingival stage four to eight weeks after implantation of the root. Clinical evaluations were performed monthly. Ten animals were sacrificed for histological evaluation of the functioning free standing implants. Of twenty‐nine implants placed, three were lost and four were rated failures on the basis of histological evaluation. Postmortem evaluations revealed bone growth into the porous surface coating of the primary stage of all the implants. The most characteristic features which could be used to describe differences in the implant histology were the buccal and lingual crestal bone heights measured in relation to the root porosity. Twelve of sixteen implants had crestal bone heights within one millimeter of the superior aspect of the root. Four other implants displayed excessive bone recession, revealing as much as one half of the root porosity supracrestally. The four implant failures could be related to unfavorable features of recipient bone sites. The results demonstrate that the bone growth into the porous surface coatings of artificial tooth roots is an efficacious method of dental implant fixation.
Removal of gamma‐II phase in amalgam
Authors: Abbott J. R. , Makinson O. F. 
Published: December 2004

AbstractTo examine the quantitative change in the γ2 phase, specimens of three conventional, four dispersed‐phase and two ternary amalgams were prepared. A higher energy amalgamator caused more γ2 phase to be formed in conventional amalgam and less in the dispersed‐phase material. With storage at 37°C this γ2 phase decreased quantitatively in dispersed‐phase amalgams over one week but not in conventional amalgams. The selective etch system of γ2 did not disclose this phase in the ternary amalgams.
Adhesion of cells to random copolypeptide films
Authors: Soderquist Mark E. , Gershman Howard , Anderson James M. , Walton Alan G. 
Published: December 2004

AbstractThe kinetics of attachment of NIL B and SV‐NIL cells to glass, siliconized glass, and surfaces coated with random copolypeptides have been studied. It was found that in the absence of serum proteins, neither the rate nor the extent of attachment of cells is affected by the nature of the surface. In the presence of bovine serum albumin, the total uptake and rate of attachment of both NIL B and SV‐NIL cells to the neutral, hydrophobic, and negatively charged copolymers is decreased compared with attachment to the same surfaces in the absence of protein. In contrast, the attachment of NIL B and SV‐NIL cells to the positively charged (lysyl) copolymers was not decreased in the presence of protein. It was shown that the effect of protein resulted from its adsorption to the surface rather than to the cells. It was also concluded that both the NIL B and SV‐NIL cells consist of a single cell population with respect to adhesiveness, and that both cell lines reach a kinetic equilibrium with the surfaces. This work represents one of the first studies to vary copolypeptide compositions systematically from negatively to neutral to positively charged surface and to examine these substrates without any mediating effects from various serum proteins. The results of this study support the concept that while cells bind to an adsorbed layer of protein rather than directly to the surface, the underlying surface can modify the attachment process by its effect on the protein adsorbed.
Blood‐Surface interactions: Fourier transform infrared studies of protein surface adsorption from flowing blood plasma and serum
Authors: Gendreau R. M. , Jakobsen R. J. 
Published: December 2004

AbstractThe adsorption of blood proteins onto various surfaces in contact with flowing blood plasma or serum has been investigated using Fourier Transform infrared spectroscopy (FT‐IR) coupled with attenuated total reflection (ATR). Comparison of adsorption from a static versus a flowing blood plasma system indicated that a greater amount of protein was adsorbed when the static system was employed, but desorption was observed with the static system and not in the flowing system. When plasma and serum were compared in terms of amount and type of protein adsorbed, little difference was noted in either kinetics of adsorption or stability of the adsorbed layers. Variations in the ratios of infrared adsorption bands (from either plasma or serum) indicate that changes occur during the adsorption process in the protein layers. A comparison of poly(vinyl chloride) to germanium as the protein adsorbing surface in the static system showed differences in terms of the composition of the adsorbed layers.
A resonance frequency technique to determine elastic modulus of hydroxyapatite
Authors: Torgalkar Anil M. 
Published: December 2004

AbstractA resonance frequency technique was applied to determine the elastic modulus of hydroxyapatite. A Free—Free Vibration Transducer was designed to determine elastic modulus in a longitudinal direction. A Fixed—Free Vibration Transducer was also designed to study elastic modulus of materials where specimens longer than 3 cm in length were not available. Six lots of hydroxyapatite were prepared utilizing the same process. The elastic modulus of hydroxyapatite varied between 3.94 × 1010(dyn/cm2) and 6.30 × 1010(dyn/cm2) in a longitudinal direction. For the same six lots, it varied between 1.95 × 1010(dyn/cm2) and 3.20 × 1010(dyn/cm2) in a cross direction. The elastic modulus values of cortical bone from dog tibias, fibulas, and femurs were also determined.
Immobilized enzyme electrodes for the potentiometric measurement of glucose concentration: Immobilization techniques and materials
Authors: Wingard L. B. , Schiller J. G. , Wolfson S. K. , Liu C. C. , Drash A. L. , Yao S. J. 
Published: December 2004

AbstractGlucose oxidase, catalase, and bovine serum albumin were co‐immobilized with glutaraldehyde around a platinum screen or around a single platinum—iridium wire. The potential difference between this dual enzyme electrode and a Ag/AgCl reference electrode was proportional to the logarithm of the glucose concentration over the range from 10 to about 150 mg glucose per 100 ml in buffered solution at pH 7.4 and 37°C. The enzyme electrode responded in serum only if coated with a semipermeable film, such as cellulose acetate, to exclude serum macromolecules. The potentiometric results were similar to those obtained with the two enzymes co‐immobilized in polyacrylamide gel around a platinum screen or with only one of the enzymes, glucose oxidase, covalently coupled to a platinum screen. The results so far suggest that these potentiometric enzyme electrodes may have sufficient specificity for glucose for development of a continuous in vivo glucose sensor.
Contact pressure dependence of wear rates of ultra high molecular weight polyethylene
Authors: Rostoker W. , Galante J. O. 
Published: December 2004

AbstractWear rates of orthopaedic polyethylene in 37°C water are not very contact stress dependent below 1000 psi (6.9 MPa) but above that level they accelerate substantially. The pressure dependence overall follows an exponential function. Creep in the contact pressure range of 3–17 MPa and above is a much larger factor than wear in indentation effects. For accurate measurement of wear rates by depth measurements it is necessary to permit creep to proceed under static load until it ceases before beginning the wear test.
Evaluation of sunlight stability of polyurethane elastomers for maxillofacial use. II
Authors: Chu C. C. , Fischer T. E. 
Published: December 2004

AbstractThe effect of selected UV stabilizers on the stability of mechanical properties of a polyurethane material, Calthane ND 2300, was evaluated. The addition of UV stabilizers prolonged the service life of the systems studied but did not achieve completely satisfactory results. The tensile strength and modulus of elasticity decreased after extended exposure to UV. The rate of decrease, however, was much less for the specimens with UV stabilizers. The polyurethane system that contains a mixture of a UV stabilizer and an antioxidant is considered to be the best of the groups tested, in terms of the percentage of retention of tensile strength and modulus of elasticity. It was also found that elongation at break was increased when the duration of UV aging was increased. This phenomenon occurred in all the systems, with or without UV stabilizers, and can be understood in terms of the concepts of the fragmentation of macromolecules that resulted from UV aging. The physical appearance in conjunction with mechanical property tests are needed to ensure the successful performance of any UV stabilizer.
A new surface treatment for bonding
Authors: Maijer R. , Smith D. C. 
Published: December 2004

AbstractBonding resins to enamel requires some form of mechanical attachment. Currently the dissolution of the outermost enamel layer is involved in etching with phosphoric acid. A new approach to mechanical bonding is described using a crystalline interface which itself bonds chemically to enamel. The crystals produced as good a bond strength as conventional acid etching. The crystals can be removed from the enamel with an ultrasonic or sickle‐scaler followed by pumice prophylaxis. Many variations of the crystal growth principle may be visualized, including the development of fluoride‐containing crystals.
Adsorption of plasma proteins on hydrophobic surfaces. IV. Contact angle studies on implanted polymers
Authors: Bagnall R. D. , Annis J. A. D. , Sherliker S. J. 
Published: December 2004

AbstractContact angle studies have been carried out on plasma protein layers adsorbed on selected polymer surfaces under buffered saline at 37°, in an attempt to demonstrate directly a recent suggestion that the interfacial free energy between such protein layers and surrounding liquid phase should be zero at equilibrium. Although an initial contact angle of 180° was always obtained, the angle decayed slowly to a stationary value which varied for any one drop on each polymer surface. The stationary values could be reasonably correlated with the reversible work of adhesion predicted for each polymer/protein combination, suggesting that protein desorption from the solid surface is a dominant event in the contact angle decay process. It is concluded that the data bear more relevance to the protein layer/polymer interface than to the protein layer/solution interface, and that the contact angle technique is not a suitable technique for studying the latter on biomaterials.
Implant‐bone interface characteristics of bioglass dental implants
Authors: Weinstein A. M. , Klawitter J. J. , Cook S. D. 
Published: December 2004

AbstractThree‐dimensional finite element analysis (FEA) has been used to determine the implant‐bone interface characteristics of bioglass dental implants. The results of the FEA were verified by comparison with the results of mechanical testing performed on animal implant specimens. The results of the study showed that the assumption of a discontinuous change of elastic properties at the bone‐implant interface was a poor assumption for the bioglass implants. Interface elastic moduli of 354.0, 155.0, and 47.0 MPa for conditions of 25, 50, and 100% tissue attachment were determined for the bioglass implants.
Haversian osteons: Longitudinal variation of internal structure
Authors: Black Jonathan , Richardson Stephen P. , Mattson Richard U. , Pollack Solomon R. 
Published: December 2004

AbstractPrevious studies have suggested that one general type of osteon exists, rather than the three types previously classified as light, intermediate, and dark. A method is presented that permits rapid, quantitative measurement of the percent transmission of osteons seen in thin section between crossed polarizers. In studies of osteon segments from human cortical bone, cut either 200 or 5 μm in length, a continuous variation of transmission is seen, both for the populations as a whole and for serial sections. These variations cannot be ascribed to angulation between the direction of observation and the axis of the osteonal segment. No correlation can be observed between the angle of the segment axis and the percent transmission. It is suggested that the collagen fiber orientation in osteonal segments must be considered to be continuous, as judged by scattering of polarized light.
Compositional dependence of the formation of calcium phosphate films on bioglass
Authors: Ogino Makato , Ohuchi Fumio , Hench L. L. 
Published: December 2004

AbstractBioglass, which has a composition of sodium carbonate, calcium carbonate, phosphorous pentoxide and silica, has been shown to bond to living bone. This ability is dependent on controlled surface reactions. Investigators with 45S5 bioglass have demonstrated that the formation of a SiO2‐rich layer and a calcium phosphate film on its surface in an aqueous environment is associated with the film bonding the bioglass to bone. The objects of this research were:

To study SiO2 dependence on the formation of a silica‐rich layer and calcium phosphate films on a bioglass surface in a simulated physiological solution, and
To establish a correlation between in vitro surface reactions and in vivo bonding ability.
It was discovered that three types of reactions occur in a simulated physiological solution depending on bioglass composition:

A calcium phosphate film and SiO2‐rich layer form simultaneously and the reaction rate is fast for bioglasses which have a lower content of SiO2 (∼46 mol% SiO2).
A SiO2‐rich layer forms first and a calcium phosphate film develops later between the aqueous environment and the SiO2‐rich layer for bioglasses whose SiO2 content is between 46–55 mol %.
A calcium phosphate film does not form for glasses whose SiO2 content is more than 60 mol %.
Design of an artificial skin. I. Basic design principles
Authors: Yannas I. V. , Burke John F. 
Published: December 2004

AbstractIndividuals who suffer extensive loss of skin, commonly in fires, are acutely ill, in danger of succumbing either to massive infection or to severe fluid loss. Patients who survive these early threats must often cope with problems of rehabilitation arising from deep, disfiguring scars and crippling contractures. In this report we describe the physiocochemical, biochemical, and mechanical considerations that form the basis for two‐stage design of a membrane useful as an experimental wound closure. Stage 1 of the design, applicable to short‐term acute use, calls for a membrane which displaces efficiently air pockets from a carefully prepared woundbed, free of weak boundary layers, and maintains the moisture flux through the wound at an optimal level. Optimization of the surface energy modulus of elasticity, energy to fracture and moisture permeability of the membrane are among the essential attributes of Stage 1 design. Stage 2 of the design, applicable to long‐term, chronic use, focuses on a nonantigenic membrane which performs as a biodegradable template for synthesis of neodermal tissue. A survey of candidate materials suggests reasons for selection of a porous, crosslinked collagen—glycosaminoglycan coprecipitate as the chemical basis of an evolving design which was initiated 10 years ago. Over the past several years a set of membranes has been iteratively designed on this basis and has been used to cover satisfactorily large experimental fullthickness skin wounds in guinea pigs. Such membranes have effectively protected these wounds from infection and fluid loss for over 25 days without rejection and without requiring change or other invasive manipulation. When appropriately designed for the purpose, the membranes have also strongly retarded wound contraction and have become replaced by newly synthesized, stable connective tissue. Several rules relating the molecular structure and morphology of these membranes to cellular response of adjacent tissue have also been derived. This report is the first in a series which details the methodology of preparation and the record of performance.
Adhesive bonding of various materials to hard tooth tissues. XX. Calcium‐to‐calcium distances in hydroxyapatite
Authors: Schroeder Leroy W. , Bowen Rafael L. , Ferris James S. 
Published: December 2004

AbstractDistributions of Ca‐to‐Ca distances have been obtained from the crystal structure of hydroxyapatite for all biologically significant planes. Most frequently, calcium ions are separated by about 4, 6.3, 7.9, and 9.0 to 9.6 Å. Frequent occurrence of distances at 10.4, 11.8, and 12.6 Å result from a Ca ion in one repeating unit being paired with a Ca in another unit cell.
Controlled slow release of chemotherapeutic drugs for cancer from matrices prepared by radiation polymerization at low temperatures
Authors: Kaetsu Isao , Yoshida Masaru , Yamada Akio 
Published: December 2004

AbstractAn effective method for controlling the release of drugs is entrapping them in a polymeric carrier. This research employs the application of radiation polymerization of glass‐forming monomers at low temperatures for the preparation of polymer composite materials comprising such biofunctional bodies and substances as enzymes, microbial cells, organellas, and drugs. The glass‐forming monomers are very advantageous for entrapping these biofunctional components because they are formed easily in an extremely viscous supercooled state at low temperatures, efficiently disperse a biofunctional component, and polymerize at a high rate in this state. Therefore, they can catch and trap the biofunctional components very firmly. This entrapping method can be used not only for the immobilization of enzymes but also for the controlled slow release of drugs. Among these drugs, the antibiotics may be the most important ones to be employed. The process makes it possible to give the antibiotics a durable effect and prevents harmful side reactions. In this report, the radiation polymerization method is applied to the controlled release of antibiotics by the preparation of polymer composites which include antibiotics.
Effect of hydroxyapatite impregnation on skeletal bonding of porous coated implants
Authors: Ducheyne P. , Hench L. L. , Kagan A. , Martens M. , Bursens A. , Mulier J. C. 
Published: December 2004

AbstractSkeletal fixation of permanent implants by new methods such as fixation by mechanical interlocking of bone with porous prosthetic coatings or chemical bonding with bioactive materials shows growing potential. This paper reports on the resulting skeletal fixation of a combined porous and bioactive material. Metal plugs with a porous metal fiber coating impregnated with hydroxyapatite were implanted for 2, 4, and 12 weeks and were compared to the parent porous, nonbioactive, metal fiber material. Statistical analysis of the interfacial failure shear stress, as obtained by mechanical testing, shows there is a marked influence of hydroxyapatite impregnation on the rate of bone ingrowth and the strength of the interfacial bond the few weeks following surgery. Microscopical examination reveals that the apparent stimulation of bone ingrowth into the surface pores of the implant is the reason for the increased rate of bond formation. The results are of particular clinical interest: with an increased rate of bone ingrowth, weight bearing might be allowed much earlier, thus reducing the recuperation period.