bluuebunny/crossref_metadata_2025 huggingface dataset:
Porous titanium endosseous dental implants in rhesus monkeys: Microradiography and histological evaluation
Authors: Young F. A. , Spector M. , Kresch C. H.
Published: December 2004

Artificial 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

To 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

The 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.
A method for the measurement of dimensional change of dental amalgam
Authors: Lemaitre L. , Moors M. , Van Peteghem A. P.
Published: December 2004

A dimensional change occurs during the setting of a dental amalgam. A measurement circuit, which makes it possible to register these changes, is introduced. To this purpose strain gages were used. The registration instrument is tested by comparing different dental amalgam products.
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

The 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

A 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

Glucose 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

Wear 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

The 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

Bonding 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

Contact 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

Three‐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

Previous 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

Bioglass, 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

Individuals 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

Distributions 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

An 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

Skeletal 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.
Thrombogenicity of different suture materials as revealed by scanning electron microscopy
Authors: Dahlke Hermann , Dociu Nicolae , Thurau Karla
Published: December 2004

The thrombogenicity of five suture materials—polypropylene (Prolene), polyester (Mersilene), polyglactin 910 (Vicryl), nylon (Ethilon), and silk—was examined in vivo by scanning electron microscopy. The most blood‐compatible material appeared to be Prolene. A rather satisfactory antithrombogenciity was shown by Mersilene, in comparison with which Ethilon and Vicryl provided less thromboresistance. The possible connection between the chemical changes which occur during the hydrolysis of Vicryl and its blood compatibility is discussed. Of the tested materials, silk proved to be the most thrombogenic. This study shows that the thrombogenicity of a suture material could be easily and conveniently tested in an experimental model by scanning electron microscopy, thus enabling the first choice of a suitable suture for the cardiovascular surgery, before one continues with other more sophisticated methods for the evaluation of thromboresistance.
Biophysical evaluation of the tumorigenic response to implanted polymers
Authors: Habal Mutaz B. , Powell Rodger D.
Published: December 2004

An evaluation of the biophysical changes of methylcholanthrene induced tumor (M4) in laboratory animals receiving four different alloplastic implants was conducted. The implants are silicone, polyether urethane, poly(methyl methacrylate), and bioglass. The tumor was allowed to grow to a large size in 28 days and then removed by shelling it from the surrounding tissue. Three different analytic volumetric measurements were carried; size in cm3, volume in milliliters and weight in grams. Statistical analysis on the three different analytic measurements did not disclose any significant differences in tumor growth potential between the control and the experimental groups. We conclude that in this study we were unable to demonstrate any tumor “facilitation” effect by any of the implantable polymers used. Therefore, there is no contraindication in using the polymers to reconstruct defects produced by cancer ablative procedures.
Interaction of the absorbable hemostatic agent (IP760) with aminoglycosidic antibiotics
Authors: James Boyle V.
Published: December 2004

The linear, crosslinked amylose‐succinate hemostatic agent, IP760, has been evaluated for its interaction with aminoglycosidic antibiotics. The highly structured polymer appears to act as a cationic exchange resin which binds the basic aminoglycosides. Binding of these agents to IP760 is reversed by increased pH and/or increased ionic strength. Dialysis experiments demonstrated that 85 and 90% of the bound gentamicin was released at pH 7.5 and 8.0, respectively, over a period of 36 hr. Formation of the IP760‐antibiotic complexes suggests potential medicinal use for hemostasis and slow release of the antibiotic for prophylaxis of postsurgical contamination or infection.
The influence of electropolishing on the corrosion resistance of 316L stainless steel
Authors: Sutow Elliott J.
Published: December 2004

A study was conducted which examined the influence of electropolishing on the corrosion resistance of a cold rolled 316L stainless steel. Test specimens were surface prepared to a final mechanical finish of wetted 600 grit SiC paper, prior to electropolishing. An oH3PO4/Glycerol/H2O electropolishing solution was employed for times of 15, 20, and 25 min. Control specimens were surface prepared only to the final mechanical finish. Anodic polarization tests were performed in a deaerated Ringer's solution (37°C) which was acidified to pH 1, with HCl. The electropolished specimens demonstrated increased corrosion resistance, when compared to the control specimens. This was evidenced for the former by more anodic corrosion and breakdown potentials, and the absence of a dissolution peak which was observed for the control specimens at the initial polarization potentials. Surface hardness measurements indicated that this increase in corrosion resistance was produced, in part, by the removal of the cold worked surface layer produced by the mechanical finish. In terms of increasing corrosion resistance, no optimum electropolishing time was found within the 15–25 min treatment period.
The anchoring of glass ceramics of different solubility in the femur of the rat
Authors: Gross U. M. , Strunz V.
Published: December 2004

A direct physicochemical bond between alkali‐rich bioglass or glass ceramic (45 S 5 A and B, Hench) or alkali‐poor glass ceramic (KG S, Brömer) and bone has been well documented. Since long‐term studies have revealed the interface to be subjected to remodeling of the bone and to increased focal disintegration of the implant, glass ceramics of reduced solubility have been developed by lowering the Na2O content and adding Al2O3, Ta2O5, TiO2, and Sb2O3. Implants of glass ceramic KG S and different compositions with reduced solubility have been studied histologically 14, 29, or 30, 60, 119, and 245 days after implantation in the femur of male Sprague‐Dawley rats. Implants of KG S are anchored at an interface with bone connection, which is known to provide for application of considerable shear and tensile strengths; whereas, at the interface of ceramics of reduced solubility, soft tissue, chondroid and osteoid are mainly observed. The dynamics of the events at the interface indicate a disturbance of the transformation of chondroid cells into osteoblasts and of the mineralization of osteold. This disturbance of pathophysiologic processes during bone healing or bone regeneration is discussed.
An investigation of the bacteriostatic properties of pure metals
Authors: Bundy K. J. , Butler M. F. , Hochman R. F.
Published: December 2004

The effect of 16 pure metals on the in vitro growth of a form of dental caries producing Streptococcus mutans was studied under both aerobic and anaerobic conditions. Cobalt and copper were consistently observed to be inhibitory. With less consistency nickel, titanium, iron, and vanadium also exhibited ability to inhibit growth of the organism. Bacteriostasis apparently is contingent upon the presence of a corrosion process. The bacteriostatic agent is of uncertain identity and could be a corrosion product or a process secondary to the occurrence of corrosion. Concentrations of metals after 6 days of electrochemical dissolution in the growth medium were measured via electron microprobe analysis and compared with the amount of inhibition which resulted. Threshold concentrations above which growth did not occur were identified. As measured by threshold concentrations, wide variability between metals exists in the ability to inhibit the growth, with cobalt being particularly effective at small concentrations. This implies a sensitivity on the part of the organism that is different for different metals. The threshold concentration varied between aerobic and anaerobic conditions. Streptococcus mutans appeared more resistant to the effects of the metals under anaerobic conditions even though little difference in the amount of corrosion was detected.
Time‐dependent failure of a polyolefin rubber candidate material for blood pump applications
Authors: McKenna G. B. , Penn R. W.
Published: December 2004

Failure behavior of a polyolefin elastomer which is a candidate material for blood pump applications has been studied under uniaxial and equibiaxial test conditions. Both static and dynamic (fatigue) testing were performed to study four aspects of material failure behavior as suggested by a cumulative damage failure model. Results from testing a standard formulation butyl rubber are presented for comparison. Our results show that the uniaxial failure behavior under static loads for the butyl rubber is superior to that of the polyolefin rubber at high loads but that the polyolefin is superior at low loads. Under fatigue loading conditions, the failure times for both rubbers decrease with increasing test frequency. The observed frequency dependence lies between that predicted by the cumulative damage model and that predicted by a cycle dependent fatigue model. The distribution of failure times for the polyolefin rubber is broader than that for the butyl rubber. For both uniaxial and equibiaxial testing, the distribution of failure times changes in going from the static testing to dynamic testing. This is true for both rubbers.
Interaction of some serum proteins with hydroxylapatite and other materials
Authors: Klein C. P. A. T. , de Groot K. , Vermeiden J. P. W. , van Kamp G.
Published: December 2004

In order to investigate whether the immune system is involved in the degradation of hydroxylapatite as implant material the adsorption behavior of several serum proteins to hydroxylapatite was studied and compared with the adsorption to other calcium phosphate compounds (Ca3(PO4)2, CaHPO4), calcium carbonate, aluminium oxide, and zinc oxide. It was found that complement factors, C4 and C3, and α2‐HS‐glycoprotein adsorbed to the calcium phosphate compounds, but not to the other materials. IgG and albumin were adsorbed to all investigated compounds. These results suggest that the complement factors are directly adsorbed on the surface of the calcium phosphate compounds. Therefore, the activation of complement, if any, proceeds by the classical pathway. The binding of complement factors to the calcium phosphate salts investigated points to a more specific involvement of the immunosystem in the degradation process of calcium phosphate implants.
The elastic modulus of soft denture liners
Authors: Ellis Bryan , Lamb D. J. , Al‐Nakash Suad
Published: December 2004

Under certain circumstances, e.g., when treating “denture sore mouth” or after the provision of immediate dentures, dentures may be lined with soft rubberlike materials which have Young's moduli within the range ≃105 N m−2. Measurement of the compression modulus Ec of such soft liners is described and Gent and Lindley's method of calculating Young's modulus E was evaluated. It was established that the Young's modulus may be calculated using: Ec = E(1 + 2kS2), where k = 1 for soft rubbers, and for disks S is a shape factor and = radius/2 × thickness. It is also shown that Young's modulus is a linear function of log(rate of strain) for both tension and compression measurements. When gellation has occurred subsequent to mixing there is an increase in Young's modulus due to loss of ethanol. When immersed in brine the elastic modulus remains approximately constant from a day to a week or longer.
Biological effects of residual glutaraldehyde in glutaraldehyde‐tanned collagen biomaterials
Authors: Speer Donald P. , Chvapil Milos , Eskelson C. D. , Ulreich Judith
Published: December 2004

Glutaraldehyde is commonly used to control physical and biological properties of collagen structure by means of intramolecular and/or intermolecular crosslinking of collagen molecules. Solubility, antigenicity, and biodegradation of naturally occurring or reconstituted collagenous matrices are effectively reduced by glutaraldehyde treatment. Adverse biological reactions to glutaraldehyde have been limited to infrequent contact dermatitis and to biocidal effects which are exploited in chemical sterilization media. In the present study of glutaraldehyde‐tanned collagen sponge, the presence of glutaraldehyde was correlated with cytotoxic effects upon fibroblasts in tissue culture and foreign body giant cell reaction to bioimplants of the sponge. Fibroblast growth in tissue culture is 99% inhibited at media concentrations of 3.0 ppm glutaraldehyde. Extracts of glutaraldehyde collagen sponge in aqueous media at pH 7 and 4.5 yielded 6 μg and 65 μg glutaraldehyde per gram of collagen sponge, respectively. The yield increased tenfold at pH 4.5. Observations indicate that leaching of the glutaraldehyde from glutaraldehyde‐tanned collagen sponge is sufficient to produce potentially adverse cellular effects both in vivo and in vitro.
Detection of aluminum oxide and polyethylene wear particles from joint endoprostheses using cathodoluminescence and x‐ray analysis in SEM
Authors: Roschger P. , Hoerl E. M. , Stachelberger H. , Plenk H.
Published: December 2004

A highly sensitive method to localize aluminum oxide or polyethylene wear particles in biological tissues is presented. Using the scanning electron microscope (SEM) with a special cathodoluminescence detector system, small amounts of these foreign materials can be visualized in simple frozen sections by their bright luminescence, even at low magnifications (200X). At higher magnifications, a differentiation of free as well as phagocytized aluminum oxide and polyethylene particles can be made due to their different behavior in light emission. In addition, aluminum oxide such as other metals can be identified by x‐ray microprobe analysis. This combination of SEM with microprobe analysis and with the highly sensitive cathodoluminescence mode enables to detect and identify wear products from all the materials, commonly used in manufacturing artificial joint replacements.
Gelatin‐based sprayable foam as a skin substitute
Authors: Neumann P. M. , Zur B. , Ehrenreich Y.
Published: December 2004

Physical and antimicrobial properties of a newly developed gelatin based spray‐on foam bandage for use on skin wounds have been evaluated. The aqueous foam is sprayed from aerosol containers and effectively covers and washes uneven wound surfaces. The foam dries to form an adherent and stable three‐dimensional matrix which diminishes evaporative water losses. The foam possesses antimicrobial activity against gram‐positive, gram‐negative, and fungal contaminants.
An in‐vitro study of the effect of buffer on the degradation of poly(glycolic acid) sutures
Authors: Chu C. C.
Published: December 2004

The tensile strengths of poly(glycolic acid) (PGA) sutures immersed in buffered and unbuffered aqueous media were compared. The media used were an unbuffered physiological saline solution (pH = 5.0) and a phosphate‐buffered physiological saline solution (pH = 7.4). PGA samples were immersed for various periods in each medium, and kept at 37 ± 1°C in a constant temperature oven. The tensile strengths of the specimens were tested immediately after removal from the medium. Stress‐strain curves of the specimens were expressed in terms of the stress unit “tenacity,” commonly used in the study of fibrous polymers; it is an appropriate unit for materials of fibrous nature. These stress‐strain curves were investigated as functions of buffering and duration of immersion. Degradation reduced the tensile strength of PGA more in the buffered saline solution than in the unbuffered. This higher rate of degradation in the buffered solution might be due to the presence of Na2HPO4, which removed the degradation products, shifted the reaction toward increased hydrolosis, and accelerated the loss of tensile strength in the PGA. A continuous decrease in the pH of the unbuffered solution supports this explanation. Tied‐chain segments of macromolecules, a theory widely used in the study of mechanical strength of fibrous polymer may be the key to a comprehensive description of the degradation phenomenon of PGA.
Fixation of porous titanium implants in cortical bone enhanced by electrical stimulation
Authors: Colella S. M. , Miller A. G. , Stang R. G. , Stoebe T. G. , Spengler D. M.
Published: December 2004

The effect of in vivo electrical stimulation on the interfacial strength between porous titanium implants and cortical bone was studied in mongrel dogs. The interfacial shear strength of the stimulated implants was consistently greater than that of controls. No difference could be observed in the quality of bone ingrowth. The data suggest that the rate and quantity of bone ingrowth were enhanced by electrical stimulation.
Biocompatibility of echinoderm skeleton with mammalian cells in vitro: Preliminary evidence
Authors: Fontaine A. R. , Hall B. D.
Published: December 2004

The physical and chemical properties of echinoderm skeleton are reviewed. A method is described for preparing cell‐free, sterile echinoderm skeletal plates (ossicles) which were used as porous substrates for cell cultures. Ossicles of the starfish Pisaster ochraceus were evaluated as substrates for the culture of three mammalian cell lines. Each line grew vigorously on ossicles, and fibroblasts quickly infiltrated their porous microstructure. Echinoderm skeletal plates provide a simple, convenient alternative to coverslips and porous membranes for SEM or correlated SEM/TEM studies of cell behavior. More importantly, the preliminary evidence for biocompatibility presented suggests that native echinoderm skeleton has potential use as a biomaterial and, because of its microstructure and relative solubility; deserves evaluation as a kind of biodegradable ceramic.
Age‐hardening and tensile properties of low gold (10–14 kt.) alloys
Authors: Kusy R. P. , Leinfelder K. F.
Published: December 2004

The age‐hardening and tensile properties were determined for seven 10–14 kt. gold alloys, a conventional type II, and a sterling silver alloy. For the low‐gold alloys the heat hardening curves indicated that the maximum aging effects were attained after 30 min at 400°C. From tensile tests on either wire or dumbbell specimen configurations, Young's modulus (E), proportional limit (P.L.), ultimate tensile strength (U.T.S.), and elongation to break were measured for alloys in both the solution annealed (S) and the hardened (H) state. These stress‐strain data not only confirmed previous correlations noted for conventional gold alloys between either E, P.L., or U.T.S. and hardness and between U.T.S. and P.L., but also varied systematically with the Au/Cu ratios in the (H) state. Under identical heat treatment and tensile testing conditions, comparison of the manufacturers' cast samples with this laboratory's specimens showed that, while the E, P.L., and U.T.S. differed somewhat, the greatest change occurred in the elongation to break. Here after measuring the porosity of the different specimen configurations and analyzing the log10 elongation with VHN, the conclusion was clear: Specimen geometry markedly influenced the physical properties. On this basis the proposed dumbbell geometry is advocated over the wire specimen configuration currently cited in ADA Specification No. 5.
Corrosion fatigue of surgical stainless steel in synthetic physiological solution
Authors: Cahoon J. R. , Holte Richard N.
Published: December 2004

Fatigue tests conducted both in air and synthetic physiological solution show that the fatigue strength of surgical stainless steel in synthetic physiological solution is about 10% lower than the strength in air for a given endurance level. It is proposed that surgical stainless steel which is normally passive in physiological solution suffers corrosion fatigue because of susceptibility to crevice corrosion which occurs at extrusions and intrusions (crevices) on the surface thereby shortening the crack initiation time and the fatigue life.
Mechanical properties of model synthetic tendons
Authors: Kolařík J. , Migliaresi C. , Štol M. , Nicolais L.
Published: December 2004

Model synthetic tendons consisting of 20 vol % of texturized poly(ethylene terephthalate) fibers and of the water‐swollen poly(2‐hydroxyethyl methacrylate) matrix have the tensile modulus E = 1.5 ± 0.1 GPa, strength and strain‐at‐break σb = 85 ± 10 MPa and ϵb = 0.08 ± 0.02. The force required for breaking tendons with the diameters 2, 3, 4 mm is, respectively, 300, 500, and 960 N. By these properties model synthetic tendons closely imitate the properties of natural tendons. Long‐term (100 min) and repeated short‐term (30 times 1 min) creep shows that on loading model tendons lose some 10% of their stiffness, but that the whole deformation is reversible. The shape of the compliance vs. time dependence of synthetic tendons closely resembles the dependence determined for the parent fiber. The stiffness and strength of a tendon are given by those of the fiber bundle used; by varying fiber volume fraction, it is possible to adjust the required mechanical properties of tendons.
In vitro corrosion and tarnish characterization of typical dental gold compositions
Authors: Vaidyanathan T. K. , Prasad A.
Published: December 2004

Analysis of the anodic polarization and alternate immersion test response of 16 precious metal alloys with compositions similar to those of commercial dental golds indicate that alloys containing high (Ag + Cu) contents are likely to be more corrosion and tarnish prone. It also appears that the alloys containing high precious metals contents (Au, Pt, and Pd) are characterized by immunity or anodic film protection over a range of anodic overpotentials, indicating superior corrosion resistance.
Biochemical, histological, and ultrastructural assessments of pseudoneointimal linings derived from fibroblast‐seeded integrally textured polymeric surfaces
Authors: Szycher M. , Poirier V. , Franzblau C. , Faris B. , Snider R. , Toselli P. , Haudenschild C. C. , Bernhard W. F.
Published: December 2004

A new technique has been employed for producing Model 11 Biomer bladders with integrally textured blood‐contacting surfaces. For the past year, we have been routinely fabricating integrally textured polymeric surfaces from negative‐replica silicone molds, which are a high‐fidelity facsimile of conventionally flocked bladders. The objectives of this investigation are threefold: (1) To develop a blood‐contacting surface that promotes the formation of a stable pseudoneointimal lining; (2) to investigate means of accelerating replacement of initial fibrin coagulum by a collagenous lining; and (3) to characterize the resultant pseudoneointimal lining biochemically, histologically, and ultrastructurally. Systematic in vivo studies were undertaken to evaluate the new surface in terms of its ability to form a thin, stable, biologic lining. Control experiments were carried out to compare results with previous experience utilizing polyester fibril flocked surfaces. Additional studies were conducted to define the effects of cell seeding of integrally textured surfaces. A total of 16 experiments have been conducted to date; eight bladders were seeded with allogeneic fetal cells prior to implantation and eight bladders were unseeded, to serve as controls. In vivo trials of seeded surfaces have resulted in the formation of strong, cellular, and highly collagenous linings, with collagen contents varying between 31% and 65%. These linings contain viable cells and thus exhibit high cellular activity, as evidenced by postexplant cell culture techniques. This indicates that a living, viable pseudoneointima has been generated. On the other hand, control (nonseeded) linings do not produce significant amounts of collagen in their linings.
Biocompatibility of polymeric delivery systems for macromolecules
Authors: Langer Robert , Brem Henry , Tapper David
Published: December 2004

We previously reported the use of polymeric delivery systems capable of sustained release of substances with molecular weights up to 2 × 106. The current study examined the tissue compatibilities of these slow‐release agents and of other polymeric materials. To observe in vivo host responses to specific implants, tests were conducted in the rabbit cornea. The cornea as an implant site has several advantages compared to other organs including its clarity, avascularity, sensitivity, and convenient access to view. Corneas were examined using stereomicroscopy and histology. Two polymers suitable for sustained macromolecular release, poly(hydroxyethyl methacrylate), and alcohol‐washed ethylene‐vinyl acetate copolymer, were noninflammatory. Other polymers considered for sustained macromolecular release, such as polyacrylamide and poly(vinyl pyrrolidone), produced significant inflammation.
Dense alumina aged in vivo
Authors: Osterholm H. H. , Day D. E.
Published: December 2004

Auger electron spectroscopy was used to investigate the relative concentration of the calcium impurity at the external and fracture surfaces of a dense alumina after in vivo exposure for 6, 12, and 23 weeks. The Ca concentration at the external surface initially decreased, reached a minimum at 12 weeks, and increased thereafter. These results were compared with the flexural strength, which decreased nearly linearly from 6 to 23 weeks.
The ultrastructure of the interface between a glass ceramic and bone
Authors: Gross U. , Brandes J. , Strunz V. , Bab I. , Sela J.
Published: December 2004

The interface of alkali‐poor glass ceramic implanted in femora of male Sprague‐Dawley rats shows soft tissue, chondroid, osteoid, and bone in connection with the implant. The ultrastructure of the interface with soft tissue mainly exhibits a corrosion process, during which the dissolution of the crystalline phase of the glass ceramic precedes the dissolution of the glassy phase. Macrophages are involved in this process phagocytosing debris of the glassy phase and removing as well as dissolving the remainders of the glass ceramic. Under circumstances not yet fully understood, the corrosion stops, and ground substance like material is deposited, which can be, at least partially, mineralized. After the disappearance of macrophages, chondroblasts, and/or osteoblasts lay down collagen fibrils and ground substance in which matrix vesicles are discernible, representing initial foci of mineralization. Areas with bone connection display collagen fibers and deposits of apatite crystals in close relationship to the bulk glass ceramic as well as small particles mainly derived from the glassy phase of the implant, providing the micromorphological substrate for the shearing and tensile strength of the interface between glass ceramic and bone.
Physical characterization of microporous poly(2‐hydroxyethyl methacrylate) gels
Authors: Migliaresi C. , Nicodemo L. , Nicolais L. , Passerini P.
Published: December 2004

Poly(2‐hydroxyethyl methacrylate)‐(PHEMA) has been prepared by polymerizing in presence of different types of water‐soluble additives, at various amounts, which were removed by swelling in water. Mechanical properties of swollen samples have been measured and analyzed by using the classical theory of rubber elasticity. Water permeability measurements were also performed to detect the presence of micropores and to determine the type of water transport. It has been shown that it's possible, using different types and amounts of additives, to obtain a wide range of physical properties of swollen PHEMA as required for various biomedical applications.
A silver staining technique for investigating wear of restorative dental composites
Authors: Wu W. , Cobb E. N.
Published: December 2004

A silver staining technique was developed to demonstrate microdefects in dental restorative composites. Fine silver particles were preferentially introduced into the damaged region to provide optical contrast between the damaged and the undamaged regions. The amount of silver deposition determined with an electron probe microanalyzer, provided an indication of the extent of damage within the dental composites. Examples to demonstrate this technique were given with one clinically worn dental composite restoration and one in vitro worn composite sample.
Platelet adhesion onto sulfonated artificial red blood cells
Authors: Muramatsu Nobuhiro , Kondo Tamotsu
Published: December 2004

Rabbit hemolysate‐loaded microcapsules having sulfonic acid groups on their surface were prepared and rabbit platelet adhesion onto the sulfonated surface was examined kinetically. Rabbit platelets adhered more markedly onto the surface of a higher charge density than that of a lower one, indicating a trend similar to that found in the case of the surface having carboxyl groups. Moreover, the platelets were found to be stickier in the buffer solution than in the plasma, though the dependence of platelet adhesion in the buffer solution on the magnitude of surface charge of the sulfonated artificial red blood cells was still recognized.