bluuebunny/crossref_metadata_2025 huggingface dataset:
Biological evaluation of dental restorative materials—a comparison of different test methods
Authors: Wennberg A. , Mjör I. A. , Hensten‐Pettersen A.
Published: December 2004

Three restorative materials–two composite resins and zinc oxide‐eugenol cement–were subjected to three cytotoxicity tests–chromium release, millipore filter, and agar overlay–one implantation test, and a pulp study. In the cytotoxicity test the materials were evaluated freshly prepared and after storage at 37°C for 24 h. In the implant test polyethylene tubes holding freshly prepared materials were inserted subcutaneously into rats. After 30 and 90 days the tissue response at the end of the tube and at a window site along the side of the tube was assessed. In the pulp study the materials were placed in cavities prepared in newly erupted monkey teeth. After 7 and 78 days the reaction of the pulp tissue was studied. Comparison of the results from the cytotoxicity tests revealed a varying degree of correlation, indicating that the three tests were not interchangeable. When data from the pulp study were compared to those of the cytotoxicity tests and implantation test, the correlation was not as good. This emphasizes that the final biological evaluation of dental restorative materials still has to be carried out as pulp studies.
Preparation of a biocompatible albumin‐coated ion exchange resin for bilirubin removal from the blood of jaundiced newborns
Authors: Sideman S. , Mor L. , Brandes J. M. , Lupovitch S.
Published: December 2004

Removal of bilirubin by hemoperfusion with ion exchange resin particles is suggested to replace exchange transfusion of blood of jaundiced infants in some cases of unconjugated hyperbilirubinemia. The hemoperfusion system developed here consists of a packed bed of a macroreticular resin which is made biocompatible by a coating of a monomolecular layer of albumin. The choice of the appropriate ionic form of the resin and the proper albumin coating and crosslinking procedure assures a high bilirubin adsorption capacity and excellent blood compatibility of the resin. The albumin coated resin removes in vitro 80–90% of the bilirubin initially present in the plasma. The results encourage in vivo clinical studies.
Effect of surface texture on the soft tissue response to polymer implants
Authors: Taylor S. R. , Gibbons D. F.
Published: December 2004

Ion beam etching has provided a system which can produce a controllable surface morphology in the micron range without altering surface chemistry or surface energy. PTFE (polytetrafluoroethylene) develops a surface texture having conical projections with average dimensions: height = 12 μm, base width = 4 μm, tip radius = 0.1 μm. Smooth and textured PTFE disks (1 cm diam. × 250 μm thick) were implanted subcutaneously into the dorsum of Sprague‐Dawley rats for time periods of 1 and 3 days and 1,2,3,4, and 8 weeks. Smooth control samples consisted of untreated surfaces and surfaces that were exposed to an ion beam environment producing a smooth surface. All smooth surfaces behaved identically by both histochemical and histological methods. Consequently, the ion beam environment had no effect on the soft tissue response. Textured surfaces, however, demonstrated increased cell adhesion and increased succinic dehydrogenase and acid phosphatase staining in the interfacial cells. Interfacial cells consisted of foreign body giant cells and macrophages. These macrophages possessed increases in the cytoplasmic‐to‐nuclear ratio, number and interdigitation of filopodia, and vacuolization as demonstrated by TEM. The textured surfaces also influence the kinetics of fibrous capsule formation. At 8 weeks, capsules associated with textured interfaces were reduced in thickness by 30% when compared to smooth surfaces. The results of this investigation demonstrate that the surface texture of an implant is a critical variable in determining the soft tissue response to a material.
Development of a new orthopedic wire fatigue tester
Authors: Sander Thomas W. , Treharne Richard W. , Baswell Imogene , Oh Indong
Published: December 2004

Even though orthopedic wire is commonly used in orthopedic surgery, very little is known about its fatigue properties. This article describes the development of a simple, effective testing machine that simulates the in situ fatigue loading of orthopedic wire. A mathematical analysis has predicted the maximum stress that is generated in wires in the fatigue machine. The fatigue resistance of intact monofilament wires made from different materials was studied. It was found that F90 was more resistant than F562, which in turn was more resistant than F138, grade 2. Also studied was the effect of cold‐forming different notch sizes on the wire surface. It was found that even the slightest notch (1% of wire diameter) reduced the fatigue life by 63%.
A newly prepared surface‐treated oxystarch for removal of urea
Authors: Shimizu Toshimi , Fujishige Shoei
Published: December 2004

There is an urgent need to develop an efficient technique to remove urea from the blood or gastrointestinal tract of uremic patients. Activated charcoals have a low sorption capacity for urea although they effectively remove other uremic toxic substances. To provide an urea‐reactive adsorbent, a chemically modified oxystarch with albumin or gelatin has been prepared. Elemental analysis and Fourier transform infrared (FT‐IR) spectroscopic analysis demonstrate that the reaction of a small amount of protein (albumin or gelatin) with oxystarch has taken place possibly by chemical combination. The influence of the dialdehyde content of the oxystarch on urea sorption, its sorption isotherm, and the adsorption rates have been investigated. It was found that the swelling factor of the oxystarch is closely related to the sorption activity under physiological conditions (pH 7.2–7.4 at 37°C). Adsorption studies have shown that sorption capacity is increased by surface treatment and can reach 6–8.2 g urea/kg‐dried adsorbent (initial urea concentration was 70 mg/dL). The oxystarch had 49.2% of glucose unit oxidized and was surface treated with albumin. These results suggest that the newly prepared surface‐treated oxystarch would be utilized as an effective chemisorbent for urea removal under physiological conditions.
Surface properties determine bioadhesive outcomes: Methods and results
Authors: Baier R. E. , Meyer A. E. , Natiella J. R. , Natiella R. R. , Carter J. M.
Published: December 2004

This investigation developed experimental evidence for the influence of different surface energy states on tissue incorporation of biomedical materials. Implants of two smooth metals, each with three different surface energy states, were placed in the subdermal fascial plane of the backs of New Zealand White rabbits and were allowed healing times of 10 and 20 days. The implant surfaces were thoroughly characterized by physical‐chemical criteria prior to surgical placement and again following removal from the tissue capsules generated by the host animals. Quantitative histopathologic analysis, using standard morphometric criteria, of the adjacent tissues revealed up to a threefold increase of fibroblastic‐fibrocytic cells against the initially scrupulously cleaned, high‐surface‐energy materials. The cells were flattened and active, producing tenacious bonds through a thin pre‐adsorbed protein‐dominated “conditioning” film, that could be broken only by cohesive failure in the tissue itself. In contrast, the lower‐surface‐energy materials typical of standard dental implants were “walled off” by a cell‐poor, nonadhesive capsule with a fibrous interface separated from a thicker “conditioning” film by a lipid‐rich mucus zone. The advantages of proper surface treatment to favor the desired degree of biological adhesion are apparent.
Some aspects of macrophage behavior at the implant interface
Authors: Salthouse Thomas N.
Published: December 2004

The macrophage plays a pivotal role in both wound healing and cellular response to implants, including percutaneous devices. Within twenty‐four hours macrophages were found in close contact with the implant surface. Eventually fibroplasts and connective tissue proliferate, and finally the implant will be encapsulated. The presence of macrophages is essential for the activation of collagen synthesis by fibroplasts. Implant shape and surface can profoundly affect macrophage behavior. At rough implant surfaces macrophages with giant cells are present for many months with the possibility of chronic granulomatous reactions. Superior tissue compatibility should be associated with smooth, well contoured implants with no acute angles.
The influence of temperature and specimen size on the flexural properties of pmma bone cement
Authors: Brown S. A. , Bargar W. L.
Published: December 2004

A three‐stage investigation was undertaken to examine the influence of specimen size and polymerization environment on the flexural properties of PMMA. In the first stage, specimens were cut from large pieces of commercially cast acrylic (Lucite) and self‐curing dental acrylic. The material properties of the cast acrylic as calculated from the results of flexural testing were not influenced by specimen size in the range of 1 × 10 × 30 to 3 × 10 × 60 mm, whereas 1‐mm thick dental cement specimens had 12% (p < 0.001) higher stress and 24% (p < 0.001) higher strain to failure than 3‐mm specimens cut from the same sample. In the second stage, self‐curing dental cement and Simplex P bone cement were molded in different thicknesses. These experiments demonstrated that molding thin 1.6‐mm specimens resulted in increases of 14% (p < 0.001) in stress and 30% (p < 0.001) in strain to failure as compared with 3.2‐mm specimens, which were greater differences than those due to the specimen thickness effects alone. In the third stage, temperatures of cement were monitored during polymerization, and cements were molded at different temperatures. These results demonstrated that thicker cement samples reached higher temperatures and that cement samples polymerized at lower temperatures (21 versus 37°C) had 12% (p < 0.001) greater stress and 105% (p < 0.001) greater strain to failure.
The peroxidase antiperoxidase staining of factor VIII‐related antigen on cultured endothelial cells
Authors: Baughman Sally , Herring Malcolm , Glover John , Dilley Russell
Published: December 2004

To prevent the premature occlusion of vascular prostheses, endothelium is being cultured experimentally onto synthetic flow surfaces. A rapid method of identifying cultured endothelium on the prosthesis is valuable for determining the degree of fibroblast and smooth muscle cell contamination and to screen for endothelial cell transformation. Fluorescent Factor VIII related antigen (FVIII‐RA) staining has been used to identify cultured endothelium, but results in excessive staining of the underlying prosthesis, loss of morphologic detail, and deterioration of the FVIII‐RA antibody reaction with time. We have applied the peroxidase antiperoxidase (PAP) method of antigen staining to permit staining of FVIII‐RA and thereby to permit a sensitive and specific identification of human or canine endothelium with a concurrent analysis of morphologic detail.
The formation of stain on acrylic surfaces by the interaction of cationic antiseptic mouthwashes and tea
Authors: Addy M. , Moran J.
Published: December 2004

Clinical and in vitro studies have implicated dietary components as major aetiological factors in staining of teeth and acrylic materials associated with chlorhexidine use, a local side effect not unique to this antiseptic. These experiments studied the precipitation and surface staining reactions of the cationic antiseptics alexidine, cetyl pyridinium chloride (CPC), chlorhexidine, and hexetidine, with the beverage tea. All of the antiseptics precipitated a standard tea solution and for alexidine and chlorhexidine acetate and gluconate, this was at concentrations >100 μmol/L, for hexetidine >200 μmol/L, and for CPC >400 μmol/L. With the exception of CPC precipitation was reduced with decreasing pH and for chlorhexidine was inhibited below pH 3. The addition of polymethylmethacrylate (PMMA) to the antiseptic solutions increased the precipitation concentrations by an amount calculated to be adsorbed by polymer. Acrylic blocks treated with equimolar solutions of the antiseptics became progressively and significantly more stained by tea than control specimens over a 5‐day period. Alexidine induced significantly greater staining and hexetidine significantly less than the other antiseptics. Staining was pH dependent and significantly reduced as the pH decreased. Both stain and precipitates were insoluble in strong acids and alkalis. It is concluded that staining observed clinically may represent a precipitation reaction with the complexing of antiseptics with dietary chromogenic material.
Modification of polyetherurethane for biomedical application by radiation induced grafting. II. Water sorption, surface properties, and protein adsorption of grafted films
Authors: Jansen B. , Ellinghorst G.
Published: December 2004

A series of polyetherurethane films grafted by means of γ radiation with hydrophilic or reactive monomers (2‐hydroxyethyl methacrylate, 2,3‐epoxypropyl methacrylate, 2,3‐dihydroxypropyl methacrylate, and acrylamide) and partially chemically modified were subjected to various physico—chemical investigation methods involving water sorption, contact angle, and protein adsorption measurements. From contact angle data the interfacial free energy γsw between grafted films and water was calculated. It was found that the water uptake of grafted films increases with grafting yield or, in the case of grafted and afterwards chemically modified films, with reaction yield; the diffusion coefficient of water in the modified films also increases with grafting yield. Contact angle studies revealed all grafted films to have surfaces more hydrophilic than the ungrafted trunk polymer. The degree of hydrophilicity—especially of HEMA‐grafted films—strongly depends on grafting conditions. For some grafted samples with high surface hydrophilicity very low interfacial free energies approaching zero were measured. The study of the competitive adsorption of bovine serum albumin, γ‐globulin, and fibrinogen from a synthetic protein solution onto modified films showed that the adsorption of albumin increases markedly with increasing grafting yields, whereas the fibrinogen and γ‐globulin adsorption only slightly increases. A correlation between interfacial free energy and protein adsorption in the sense of the “minimum interfacial free energy hypothesis” was found only for samples with grafting yields below 5%. At higher grafting yields the increased surface area complicates the analysis.
Correlation between microstructure of AgPdAuCu alloy and changes in shape on aging
Authors: Asaoka Kenzo , Tsuji Koichiro , Kuwayama Norihiko
Published: December 2004

An investigation has been carried out to study changes in shape on aging in plastic deformed AgPdAuCu alloys. The changes in shape were measured in order to establish a relationship to the aging heat treatments. Their microstructure was observed in order to clarify this phenomenon at the same time. They were also investigated quantitatively using a feature analysis system. The changes in shape were interpreted as the shrinkage in volume resulting from the formation of the ordered phase. They were smaller at aging temperatures below 673 K. The change in microstructure was different at aging temperature between 573 and 773 K. These phenomena were due to the following: First, nodules which nucleated at the grain boundaries would have grown into the grains well before the formation of the ordered phase, and second, the shrinkage in volume would have been of a different kind that the ordered phase. Therefore aging treatments should be carried out at low temperature in order to minimize the changes in shape. Also, nodular growth should be inhibited in order to maximize the hardening in Ag‐rich alloys.
The influence of dentine on the in vitro cytotoxicity testing of dental restorative materials
Authors: Meryon S. D.
Published: December 2004

Few in vitro systems for testing dental restorative materials have taken into account the protection afforded by the residual dentine in vivo. In turn opinions differ as to whether an increase in residual dentine thickness increases this protection. In this study an increase in the depth of dentine powder beneath zinc oxide eugenol (ZOE) reduced its toxicity, while this was not the case with the glass ionomer cement. Compaction of the powder had no effect, suggesting that protection was due to binding of the toxicant to the dentine rather than it acting as a physical barrier. Protein was shown to be very important in moderating the cytotoxicity of ZOE. These results suggest that in vivo the irritancy of some materials may be related to the depth of residual dentine but not others. The effect of exposure period and volume of these materials on their cytotoxicity was also investigated. Increasing the volume of ZOE while retaining the same surface area increased the toxicity of ZOE, while with the glass ionomer it had no effect.
Correlation of tissue reaction to corrosion in osteosynthetic devices
Authors: French H. Graeme , Cook Stephen D. , Haddad Ray J.
Published: December 2004

This study evaluated the interaction of osteosynthetic plates to adjacent tissue. Eleven patients had 13 plates removed with simultaneous biopsies of the adjacent soft tissue. Four patients had pain localized to the area of the plate and 11 patients had routine removal or removal for fracture nonunion. Each plate was graded on a 0–5 point scale for the amount and severity of corrosion present at the screw—plate interface. The adjacent tissue was fixed in formalin and stained with hematoxylin and eosin. The tissue reaction was graded on a 0–5 point scale based on the inflammatory response. A positive correlation of corrosion and tissue reaction was found that was significant at p ≤ 0.005 in the assymptomatic group. The other good correlation showed that tissue reaction tends to decrease with time at p ≤ 0.005. There was no correlation of corrosion with tissue reaction in the symptomatic removal group. All patients with pain adjacent to the plates were relieved by implant removal. The findings suggest that stainless steel is minimally toxic to human tissue in most circumstances and that the toxic products are well tolerated. There was a significant group (4/11) that showed a different pattern of tissue response which did not appear to be toxic response. We do not recommend routine implant removal to prevent metal toxicity; however, there is a group of patients who have pain in the area of the implant that may be caused by an allergic reaction and is relieved by implant removal.
Removable partial denture design: A photoelastic study
Authors: Stewart B. L. , Edwards R. O.
Published: December 2004

Quantifiable frozen‐stress photoelastic techniques were used to analyze stresses induced in mandibular models by a conventional free‐end saddle removable partial denture. Four quasi‐anatomical mandibular models were constructed for processing, together with their respective calibration specimens, through identical time/temperature stress‐freezing cycles. After processing and slicing, an unloaded control model demonstrated some low‐order fringes adjacent to the coronal third of the abutment tooth roots, but was otherwise stress free. A lower bilateral free‐end saddle partial denture was constructed and fitted in turn to each of the remaining three models. Each denture/model combination was then loaded and processed through a stress‐freezing cycle. After processing, 6‐mm slices were cut from selected regions for analysis for the presence of stresses. Using a polariscope with circular polarized, monochromatic light, values for maximum shear stress were calculated at selected points in the slices taken from the three loaded models. Variations up to 28% of the mean were obtained for the three experimental models as compared with the consistent results for the material fringe values obtained from the calibration specimens. The study pointed out the problems involved in using photoelastic stress analysis on complicated anatomical models. The interpretation of the results from such studies should be approached with caution.
Materials, clinical and morphological evaluation of custom‐made bioreactive‐glass‐coated canine hip prostheses
Authors: Ducheyne P. , Martens M. , Burssens A.
Published: December 2004

Bioreactive‐glass‐coated hip prostheses were implanted in dogs for periods of time ranging from 3 to 17 months. The prostheses were tailor‐made for each animal through the use of standard radiographs. However, such a procedure does not necessarily yield a close apposition between the glass layer and bone. As a result, the initial stability of the component can be lost before bone bonding is established. Secondary to this phenomenon, the micromotion can lead to a continuous disruption of the top film on the glass despite the evidence of various reaction layers on the glass surface.
Morphological characteristics of tendon cells cultured on synthetic fibers
Authors: Ricci J. L. , Gona A. G. , Alexander H. , Parsons J. R.
Published: December 2004

Filamentous carbon is currently being used as an implant material for tendon and ligament repair in humans. This material acts as a scaffold for the organization of new fibrous tissue growth. Primary cultures of rat tendon fibroblast cells (1° RTF cells) were grown on carbon, Dacron, polyethylene and Nylon fibers in vitro. The morphological characteristics of these cells were examined. The process of cell migration from tendon explant to fiber substrate was similar for all four materials. Three morphological categories of cells were observed on these materials. (1) spherical dividing cells, (2) spindle‐shaped migrating cells, (3) sheath‐like migrating or stationary cells. The morphological characteristics and orientational behavior of cultured fibroblasts on these fiber materials were strongly influenced by the diameters of the fibers and by fiber surface characteristics such as longitudinal striations. The possible mechanisms of cell response to substrate geometric configuration are discussed along with the clinical significance of these experiments.
A calorimetric study of the interaction of synthetic phospholipid liposomes with vinyl monomers, acrylates and methacrylates
Authors: Fujisawa Seiichiro , Kadoma Yoshinori , Masuhara Eiichi
Published: December 2004

Mono‐, di‐, and trimethacrylates (monomers) are widely used in dentistry as restorative materials, adhesives, prosthetic devices, etc. It is known that the residual monomers released from the cured resin have been implicated in toxicological effects.1 In order to monitor the biological actions at the membrane level induced by monomers, we studied the changes in the phase transition temperature (T) and enthalpy (ΔH) of dipalmitoyl‐phosphatidyl‐choline liposomes induced by 37 different monomers using differential scanning calorimetry (DSC). The monomers that caused large changes in the T and ΔH were vinyl monomers; acrylates; monomethacrylates that contain hydroxy, carbonyl, amino and phenyl groups; dimethacrylates with short‐chain substituents; and aliphatic trimethacrylates. It is suggested that the changes in the T and ΔH values may be due not only to hydrophobic interactions, but also to interactions induced by the double bonds or the functional groups in the monomers. On the other hand, methacrylates with simple alkyl ester linkage and dimethacrylates with bisphenol A groups exhibited the smallest changes. The changes in the T and ΔH induced by highly hydrophobic methacrylates were small due to their slower interaction. These changes in transition properties of liposomes seem to be related to biological activities.
In vivo validation of a cell culture test for biocompatibility testing of urinary catheters
Authors: Graham D. T. , Mark G. E. , Pomeroy A. R. , Macarthur E. B.
Published: December 2004

Biocompatibility tests have been compared for their suitability as routine safety tests for urinary catheters. Latex catheters from five manufacturers were tested by each of the following four methods: (1) a cell culture cytotoxicity assay of catheter extracts, (2) intracutaneous injection of the extracts into rabbits, (3) intramuscular implant of catheter pieces into rabbits, (4) catheterization of sheep (mucous membrane irritation). The rabbit intracutaneous and intramuscular tests are both current pharmacopoeial methods for ascertaining the suitability of polymers for medical use. The four tests each showed a cell or tissue response ranging from no detectable change to severe damage, according to the catheter batch or brand, and they each identified the same samples as most toxic and least toxic. However, they differed in sensitivity. The sheep test and the cell culture assay discriminated between catheters of intermediate toxicity and ranked as toxic catheters not identified as such by the two pharmacopoeial tests. The sheep test most closely approximates clinical usage, but is impractical for routine use. The cell culture assay is a suitable alternative. It also has the advantages of a clearly defined endpoint, good sensitivity, reproducibility, speed, and reduced animal usage.
The initial stages of adsorption of plasma derived proteins on artificial surfaces in a controlled flow environment
Authors: Rudee M. L. , Price Todd M.
Published: December 2004

Surfaces of amorphous carbon, polystyrene, and polycarbonate were exposed to solutions of fibrinogen, a modified fibrinogen which lacked the alpha chain protuberance, and serum albumin. The results were studied by electron microscopy. The exposures occurred in a well characterized flow environment at a shear rate of 135/s. All three protein species formed a film when adsorbed to carbon films. When the proteins were adsorbed to polystyrene surfaces, formation of a network was observed. Polycarbonate surfaces adsorbed the proteins both as a network and as a continuous film. It was observed that the nature of the adsorption process depended upon the specific combination of molecule and material. For example, on carbon, individual fibrinogen molecules retain their trinodular structure and adsorb randomly until a monolayer forms. On polystyrene, the individual fibrinogen molecules appear as globules and a network forms before complete coverage occurs.
Roughness and thrombogenicity of the outer surfaces of intravascular catheters
Authors: Hecker J. F. , Scandrett L. A.
Published: December 2004

Thirty‐seven types of catheters made from plastics including silicone rubber, polyvinylchloride, polyethylene, and polyurethane were tested for thrombogenesis in the cephalic vein of sheep. The range in the mass of thrombus on the catheters at autopsy 9 days after insertion was 20‐fold. There was considerable variation when catheters made from the same types of plastic were compared, but polyethylene catheters tended to be more thrombogenic than other types. Scanning electron microscopy (SEM) revealed a variety of surfaces ranging from very smooth to very rough. Roughness was frequently associated with the presence of radioopaque particles which in several catheters were concentrated into radio‐opaque tracer strips. Within types of plastics, catheters with rougher surfaces were usually more thrombogenic than those with smooth surfaces.
The load carrying and fatigue properties of the stem–cement interface with smooth and porous coated femoral components
Authors: Manley M. T. , Stern L. S. , Gurtowski J.
Published: December 2004

Porous coated surfaces for fixation of total hip replacement are a current trend in clinical orthopedics. Such devices are designed to be fixed by ingrowth of bony tissue, although in the absence of FDA approval for biologic fixation, fixation with PMMA cement is recommended by the implant manufacturers. In order to characterize the mechanical properties of the microinterlocked stem–cement interface, we tested both porous coated and smooth femoral components in cement mantles of consistent overall geometry. Under conditions of increasing load the smooth stems demonstrated stepwise irreversible subsidence into the mantle. Axial and circumferential strains measured in the cement containment vessels with the smooth stems showed that stepwise increases in tensile hoop strain occurred concomitantly with the stepwise incidents of stem subsidence. When subjected to the same loading conditions, the porous coated stems did not undergo stepwise incidents of subsidence, and hoop strain generation was reduced. In addition, a twofold increase in the failure load of the stem–cement interface was measured with the porous coated stems. Fatigue loading for 107 loading cycles did not result in gross failure of either the microinterlocked or smooth interfaces. However, the data showed that during fatigue loading, stepwise subsidence of the smooth stems again occurred. The final subsidence magnitude of the smooth stem–cement interface at 107 loading cycles was six times greater than the value associated with the porous coated stem. Thus the porous coating of femoral stems was shown to dramatically improve the load carrying capability and fatigue characteristics of the stem–cement interface.
A new glass‐ceramic for bone replacement: Evaluation of its bonding to bone tissue
Authors: Nakamura Takashi , Yamamuro Takao , Higashi Shoichiro , Kokubo Tadashi , Itoo Setsuo
Published: December 2004

Glass powders (350 mesh) of the composition MgO, 4.6; CaO, 44.9; SiO, 34.2; PO, 16.3; CaF, 0.5 in weight ratio were compacted, heated to 1050°C at a rate of 5°C/ min and kept at 1050°C for 2 h. The resultant glass‐ceramic having oxyapatite, fluoroapatite, and wollastonite crystals showed high bending and compressive strengths of 157 and 1060 MPa, respectively. The biocompatibility and bonding ability of this new glass‐ceramic to the bone tissue was evaluated using rabbit tibial bones, and the failure load to break the bonding of several ceramics (the new glass‐ceramic, dense hydroxyapatite, 45S5 Bioglass, alumina‐ceramic) to bone tissues was measured. The new glass‐ceramic showed tight bonding to bone comparable with dense hydroxyapatite, and in 25 weeks its load was 70% of that of bone tissue.
Poly(O‐acyl hydroxy L‐proline) (II) wetting characteristics and blood clotting on surfaces of poly O‐acetyl, butyryl, hexanoyl, dodecanoyl, and benzoyl hydroxy L‐proline
Authors: Kawasaki Tadayoshi , Komai Takashi
Published: December 2004

Poly O‐acetyl, butyryl, hexanoyl, dodecanoyl, and benzoyl hydroxy L‐proline (poly[O‐acyl Hyp]s) were evaluated as materials for blood contact by means of contact angle and blood clotting time measurements. Critical surface tensions obtained from Zisman plots for all materials were 22–29 dyn/cm, suggesting that these materials may exhibit good blood compatibility. Dispersion and nondispersion force contributions to the surface tension were γ = 1.4, γ = 49.3 dyn/cm, (11.0, 16.2), (19.8, 3.8), (21.2, 4.6) and (14.1, 10.8) for the poly(O‐Acetyl, Butyryl, Hexanoyl, Dodecanoyl and Benzoyl Hyp) surfaces, respectively. The materials showed remarkable wetting differences that were dependent on the type of acyl group attached to Hyp.

The values of the dispersion and nondispersion components of the surface tension for poly(O‐hexanoyl Hyp) and poly(O‐dodecanoyl hyp) were very close to those obtained for glutaraldehyde‐treated umbilical cord vessels. The blood clotting times on the respective polymer surfaces, obtained by using the kinetic method, were normalized to those of control glass and siliconized glass surfaces. All the poly(O‐acyl Hyp)s surfaces showed longer clotting times than those of the poly(L‐proline) and glass surfaces. The surfaces of those polymers having longer aliphatic or aromatic acyl groups had longer clotting times than those of the polymers with relatively shorter groups.
Characterization of morphologic and mechanical properties of surgical mesh fabrics
Authors: Chu C. C. , Welch L.
Published: December 2004

The objective of this study is to use standard testing methods to characterize the currently available synthetic mesh fabrics in terms of their chemical, physical, mechanical, and morphologic properties. Three commonly used surgical mesh fabrics, Mersilene (Ethicon), Marlex (Davol), and Teflon (USCI), were used, and the tests reveal that they differ from one another chemically as well as configurationally. The experiment included an identification of the structure of the yarn and fabrics; a measurement of the porosity, pore size and shape; and a determination of tensile and bursting strength, flexural rigidity, and wrinkle recovery. A wide variation in structure and performance was observed among the three mesh fabrics. Mersilene mesh fabrics have the highest relative porosity, while Marlex and Teflon meshes have an equivalent, but lower value. Marlex meshes have the highest tensile and bursting strength followed by Teflon and Mersilene meshes. All three meshes have one common strength characteristic—a distinctive difference in tensile strength between the wale and course directions. Marlex mesh fabrics exhibit an immense flexural rigidity and poor wrinkle recovery, due mainly to the monofilament structure of the yarn. Mersilene and Teflon mesh fabrics have similar but considerably lower, flexural rigidity than Marlex. Thus, it is evident that the chemical nature of the constituent fibers, as well as the yarn and fabric structure, have a great effect on the performance of the resulting mesh fabrics. The availability of this characterization data can serve as the basis for a surgeon's selection of the most appropriate commercial surgical mesh fabric for each case, as well as to provide a foundation for the subsequent comparison of their in vivo performance.
Electrochemical behavor of aluminum in human plasma
Authors: Salvarezza R. C. , de Mele M. F. L. , Videla H. H. , Goñi F. R.
Published: December 2004

The electrochemical behavior of aluminum in isotonic saline solutions, citrated human plasma, and citrated human blood is studied using potentiostatic and potentiodynamic polarization techniques complemented with scanning electron microscopy (SEM) and dispersive x‐ray analysis. The effect of corrosion products on plasmatic proteins is investigated using electron microprobe analysis and immunoelectrophoresis analysis. Electrochemical data show a breakdown of the protective film on aluminium, due to the action of chloride, leading to the pitting of the metal. During pitting, the interaction of aluminium ion and the plasma proteins produces a nonadherent precipitate. Strong protein denaturation can be observed by immunoelectrophoresis of the precipitate suspended in physiologic solutions. The convenience of using organic fluids in addition to saline solutions to evaluate in vitro the behavior of metal for implants is suggested.
Glucose‐sensitive membranes containing glucose oxidase: Activity, swelling, and permeability studies
Authors: Kost Joseph , Horbett Thomas A. , Ratner Buddy D. , Singh Manindar
Published: December 2004

The development of membranes that swell in response to glucose is reported. The membranes may prove to be useful in glucose monitoring or glucose‐dependent insulin delivery. The polymers were synthesized by the radiation‐induced polymerization of frozen solutions containing hydroxyethyl methacrylate, N,N‐dimethylaminoethyl methacrylate, tetraethylene glycol dimethacrylate, ethylene glycol, water, and glucose oxidase. The polymers were hydrogels, with water contents in the range of 60–90%, depending on the pH or glucose concentration. Changes in swelling and permeability of the hydrogel were caused by exposure to glucose solutions. The gluconic acid formed by the glucose oxidase catalyzed oxidation of glucose in the membrane lowered the pH of the system and thus caused the changes in the membrane. The retention of enzyme activity by the membranes in vitro and in vivo is also reported. The large differences in properties among membranes made with different chemical formulations suggest that glucose‐sensitive membranes with performance characteristics needed for an artificial pancreas may be an achievable goal.
Percutaneous healing of clinical tympanic membrane implants
Authors: Powers Dennis L. , Henricks M. Lucile , Von Recum Andreas F.
Published: December 2004

Percutaneous healing is plagued by materials compatibility problems, epidermal reactions, and mechanical factors. To our knowledge, no studies have evaluated the effects of one of these factors while controlling the others. The tympanic membrane is an implant site where mechanical factors are minimized. Titanium has been shown to be a very histocompatible material, although no reports of the histology of percutaneous titanium implants exist. This study reports on aspects of the epidermal and connective tissue healing around titanium tympanic membrane implants that were explanted from human subjects. The lack of inflammation and the direct adherence of the tissues substantiate the materials compatibility and the absence of mechanical factors. Tissue healing patterns appear to reach an equilibrium which is suitable for the long‐term exixtence of the percutaneous device. This implant location provides a suitable model for studying the tissue reactions to various percutaneous materials.
Lysis time and FDP immunoprecipitation by soluble and immobilized urokinase
Authors: Senatore Fred , Bernath Fred
Published: December 2004

Urokinase (UK) was immobilized to the lumen of dacron‐reinforced fibrocollagenous tubes (UK‐FCT) using a glutaraldehyde entrapment process, in an effort to develop a fibrinolytic small diameter (i.e., 4 mm i.d.) vascular graft. Soluble and immobilized urokinase were evaluated for their ability to lyse synthetic clots made from purified physiologic substrates, α2 plasmin inhibitor (α2PI) mediated whole canine blood (WCB) and α2PI‐depleted WCB by measuring lysis time and fibrin degradation product (FDP) formation. Lysis times were orders of magnitude lower and FDP formation rates were orders of magnitude higher with synthetic clots compared with either α2‐mediated or α2‐depleted WCB clots as a substrate, using both soluble and immobilized UK. However, both soluble and immobilized UK catalyzed FDP formation at an enhanced rate for α2PI‐depleted WCB compared with the inhibitor‐mediated substrate. These results suggest that both soluble and immobilized UK behave similarly when treated with either standard clots, α2PI‐mediated WCB and α2PI‐depleted WCB as substrates and the use of urokinase‐bound fibrocollagenous tube may prove suitable as a fibrinolytic vascular prosthesis.
Release of corrosion products by F‐75 cobalt base alloy in the rat. II: Morbidity apparently associated with chromium releasein vivo: A 120‐day rat study
Authors: Wapner K. L. , Morris D. M. , Black J.
Published: December 2004

There is concern whetherin vivocorrosion of chromium–cobalt alloys releases ions containing trivalent [Cr(III)] or hexavalent [Cr(VI)] chromium. The question arises from indications that Cr(VI) is far more biologically active than Cr(III). Using a previously developed microsphere implant model, specimens of F‐75 chromium‐cobalt‐molybdenum alloy were implanted in rats for periods up to 120 days. Blood and urine were collected at intervals during the study. Significant postoperative serum and urine chromium concentration elevations were observed. In addition, weight gain inhibition, lung morbidity, and animal mortality, related to the implant surface area to animal body weight ratio (SA/BW), were observed. Comparison of measured chromium serum concentrations with those concentrations found by others to be biologically active in tissue culture studies strongly suggests the release of Cr(VI) in this study.
Glass transition temperatures of dental porcelains at high heating rates
Authors: Twiggs S. W. , Hashinger D. T. , Morena R. , Fairhurst C. W.
Published: December 2004

The glass transition temperature (Tg) of a dental porcelain is a factor in determining the magnitude of residual stresses introduced in a dental porcelain during cooling of a porcelain‐fused‐to‐metal prosthesis. Tg is known to vary with changes in heating or cooling rate. However, available commercial instrumentation does not permit Tg to be obtained at the very high cooling rates commensurate with actual dental laboratory practice. Tg values are reported here for a number of commercial dental porcelains and other materials. These data were obtained by the bending beam technique, employing a special low thermal‐mass furnace to permit rapid heating and cooling rates. Measurements were made at rates as high as 600°C/min. Coefficients of determination (r2) for 1/Tg vs. In (heating rate) were excellent. This relation is consistent with previously reported low rate Tg data obtained by a different technique.
Evaluation of anti‐inflammatory agents using a model of granuloma formation evoked by divinyl copolymer beads in the mouse lung
Authors: Coleman Sylvia E. , Hood C. Ian , Schoen Frederick J. , Rheinhardt Jeanette M.
Published: December 2004

We have developed and quantitated a reproducible standardized granulomatous inflammatory reaction using divinyl copolymer beads. Approximately 10000 gas sterilized beads (43–53 μm in diameter) are injected into the tail veins of mice and embolize to the lungs where they evoke granuloma formation which is maximal at 48 h. The anti‐inflammatory effects of both steroidal and nonsteroidal agents, namely, bacterial levan, hydrocortisone acetate, polyanetholsulfonate, indomethacin, acetylsalicylic acid, ellagic acid, and aminophylline were determined by comparing granuloma size in treated animals with those in untreated controls. Granulomas in paraffin sections were traced on the ground glass screen of a light microscope and the area of each granuloma measured with a digitizer‐computer programmed to prepare histograms and merge data from replicate experiments. Of the agents tested, the greatest reductions in granuloma size occurred after treatment with bacterial levan (71%), hydrocorticone (70%), polyanetholsulfonate (58%), and indomethacin (55%).
Mechanical effects on rates of hemolysis
Authors: Nakahara Toro , Yoshida Fumitake
Published: December 2004

Empirical studies were conducted on how rates of hemolysis were influenced by mechanical factors, such as shear, turbulence, agitation, pressure fluctuation, and bubbling, in five types of experimental apparatus: rotating cylinder, rotating disks, agitated vessel, pressure pulsator, and bubble columns. Our data indicate, at least qualitatively, that an important mechanical factor controlling rates of hemolysis in practical devices, in which blood does not flow in thin channels or capillaries, is the turbulent stress in the bulk blood, rather than the shear at the blood–solid interface.
Bacterial inhibition by electrical activation of percutaneous silver implants
Authors: Spadaro J. A. , Chase S. E. , Webster D. A.
Published: December 2004

Percutaneous silver wire implants were looped through the dorsal skin of rats and inoculated with Staphylococcus aureus to test the effect on bacteria in the tract. The silver was activated with four brief daily applications of anodic microcurrent. Contralateral 316L stainless steel implants, identically inoculated, served as controls. Cultures from the silver tracts showed a marked reduction or elimination of bacteria, which persisted for the 3‐week study period. In tracts with colonization established for 1 week, subsequent electrical activation of the silver also suppressed the bacteria. Inflammatory reactions at 3 weeks were mild at both the silver and stainless implants and no giant cells or toxicity were seen. This suggests that electrically activated silver may be useful in preventing or treating infection at percutaneous devices.
Perforated demineralized bone matrix: A new form of osteoinductive biomaterial
Authors: Gendler E.
Published: December 2004

This study was undertaken to evaluate a new osteoinductive material—perforated decalcified bone matrix (PDBM). Subcutaneous implantation of PDBM induces multiple centers of endochondral osteogenesis with subsequent resorption of bone matrix and its replacement by new bone. PDBM should therefore prove useful as a research model to study osteoinduction and in the clinical situation in orthopedic and reconstructive surgery for the filling of bone defects and stimulation of fracture healing.
The kinetics of baboon fibrinogen adsorption to polymers: In vitro and in vivo studies
Authors: Horbett T. A. , Cheng C. M. , Ratner B. D. , Hoffman A. S. , Hanson S. R.
Published: December 2004

Fibrinogen adsorption on polymers from blood may mediate or potentiate thrombosis because of its involvement in both the intrinsic clotting system and the formation of platelet aggregates. While the kinetics of fibrinogen adsorption from plasma in vitro have previously been found to be very different on polar and nonpolar surfaces [T. A Horbett, “The kinetics of adsorption of plasma proteins to a series of hydrophilic‐hydrophobic copolymers,” ACS Org. Coat. Plas. Chem., 40, 642–646 (1979)] the significance of this difference with respect to thrombogenesis in vivo has not been clarified. In this study, the kinetics of deposition of baboon 125I fibrinogen from plasma in vitro or from blood in vivo on a series of polymers was measured. The polymers chosen for this study had previously been found to have a large range in surface polarity and reactivity in the in vivo baboon shunt model. The kinetics of fibrinogen adsorption in vitro were observed to be of three types, depending on the polymer: (1) high initial adsorption decreasing to a lower steady state value; (2) constant throughout the time course; (3) low initial adsorption rising steadily to a plateau value. In vivo, fibrinogen deposition kinetics were of two types: (1) low, constant deposition throughout the time course, independent of heparinization; (2) low deposition initially followed by a second phase of greatly increased deposition (probably as fibrin) which was prevented or greatly decreased by heparinizing the animals. Polymers for which fibrinogen adsorption increased to a plateau in vitro were found to have a heparin inhibitable second phase of enhanced in vivo fibrinogen deposition. These polymers also have been found in previous studies to enhance the rate of platelet destruction when used as in vivo shunts on baboons. Conversely, most polymers with high initial in vitro fibrinogen adsorption followed by a decrease had low fibrinogen deposition behavior in vivo and were also minimally destructive of platelets. The adsorption kinetics of fibrinogen to polymers from blood in vivo and in vitro and the consumption of platelets in vivo induced by the polymers all vary with polymer polarity. More polar polymers had in vitro fibrinogen kinetics characterized by a rise to a plateau, in vivo fibrinogen deposition characterized by a second stage of great increase inhibitable by heparin, and enhanced platelet consumption. The correlation of three separate indicators of surface thrombogenicity with surface polarity suggests that more polar materials may be more thrombogenic because of an influence on the way in which fibrinogen interacts with these surfaces.