bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effect of age on the creep of a high‐copper amalgam
Authors: Mahler David B. , Nelson Lyle W. 
Published: December 2004

AbstractA previous study of the effect of final Hg content on the static creep of a single‐composition high‐Cu amalgam alloy showed a sudden increase or jump in creep at a specific Hg content, and the presence of the SnHg phase (γ2) at final Hg contents subsequent to this creep jump. This observation is consistent with the less‐than‐optimum clinical performance reported for this alloy. A repetition of these tests conducted on test specimens 3 months and 6 months of age showed the creep jump to shift to higher Hg contents. However, even at 6 months of age, the final Hg content to be expected in clinical restorations was still positioned after the initiation of the creep jump where a small amount of γ2 is known to be present.
Organic surface film contamination of Vitallium implants
Authors: Malcolm Carter J. , Flynn Harry E. , Meenaghan Michael A. , Natiella Joseph R. , Akers Charles K. , Baier Robert E. 
Published: December 2004

AbstractConventional finishing and polishing techniques used to prepare Vitallium subperiosteal dental implant castings were found to produce low energy surfaces as measured by critical surface tension. Standard metallographic preparation gave slightly higher values. Glow discharge cleaning of both types of polished surface gave much higher critical surface tension values. This suggests the presence of an organic film after surface polishing of the implant which may later affect tissue reaction, in particular attachment, as has been noticed in related animal studies.
Crevice and fretting corrosion of stainless‐steel plates and screws
Authors: Brown S. A. , Simpson J. P. 
Published: December 2004

AbstractMechanisms of corrosion at the areas of contact between screw heads and plate holes were investigated using electrochemical potential recording techniques. Static crevice corrosion was studied with plates and screws in isotonic and hypertonic saline solutions (0.9 to 7.2% NaCl). Fretting corrosion was studied in vitro with plates screwed to tubular bone analogs which were subjected to cyclic axial loads, and was studied in vivo with plates screwed on the tibia of sheep. Static tests showed that crevice corrosion does not occur in isotonic saline for periods up to one year, but can occur in hypertonic saline solutions. Dynamic loading tests demonstrated immediate potential changes which were related to the magnitude of the applied load, indicating fretting corrosion due to motion between screw head and plate, both in vitro and in vivo. A mechanism for screw‐plate relative motion is proposed. It is hypothesized that corrosion seen in clinically retrieved implants due to fretting corrosion which predisposes the contact area to crevice corrosion attack.
The influence of implant elastic modulus on the stress distribution around LTI carbon and aluminum oxide dental implants
Authors: Cook S. D. , Klawitter J. J. , Weinstein A. M. 
Published: December 2004

AbstractA three‐dimensional finite element analysis (FEA) has been used to determine the effect of implant elastic modulus on stresses in tissues around LTI carbon and aluminium oxide dental implants. The finite element model was constructed to represent a baboon mandible containing a blade type dental implant. A three unit fixed bridge was modeled connecting the dental implant to a natural molar. The results of the study indicate that stress levels of approximately a factor of 3 lower in the crestal region can be expected for aluminum oxide implants when compared to the LTI carbon implants. It was also observed that the use of LTI carbon and aluminium oxide dental implants as an abutment in a fixed bridge results in a reduction of stresses in tissues around the natural tooth when compared to normal physiological stress levels.
The role of the fibrous capsule in the function of implanted drug‐polymer sustained release systems
Authors: Anderson J. M. , Niven H. , Pelagalli J. , Olanoff L. S. , Jones R. D. 
Published: December 2004

AbstractNumerous studies have been carried out on drug‐polymer sustained release systems designed for implantation. The majority of these efforts have been directed toward determining the in‐vitro rate of drug release from specific systems or drug polymer combinations and the in‐vivo studies have attempted to utilize analysis of the blood serum and excretory products as a measure of the release rate and behavior. To gain a better understanding of the influence of the local tissue environment and implant site on release behavior, we have investigated the release behavior of a gentamicin‐silicone rubber system implanted in canines. Particular attention has been directed toward investigating the role that the fibrous capsule which eventually surrounds the implant plays in determining the rate and pattern of drug release. The drug burst effect was decreased by the use of a drug‐free silicone rubber membrane on the gentamicin‐silicone rod implant. Analysis for gentamicin in the tissue adjacent to the implant for periods up to four weeks indicated that the release rate was retarded by the development of the fibrous capsule. The temporal and spatial variations in gentamicin levels in the tissue surrounding the rod implants were determined. In addition, the influence of implant coating and gentamicin loading level in the implant on local tissue concentrations with time were also investigated. These studies provide evidence that the fibrous capsule surrounding a drug‐polymer sustained release implant may influence the release behavior of the drug in an avantageous or disadvantageous manner depending upon the desired function of the sustained release system.
A quantitative microassay for in‐vitro toxicity testing of biomaterials
Authors: Ulreich Judith B. , Chvapil Milos 
Published: December 2004

AbstractA quantitative tissue culture method is described for toxicity testing of biomaterials. The material to be evaluated, or in the case of insoluble materials—an extract of the material, is incubated on a monolayer of fibroblasts in 24 well culture plates. The activity of the fibroblasts is ascertained by measuring the rate of mitosis (3H‐thymidine incorporation), the synthesis of glycosaminoglycans (35SO incorporation) or production of total protein (3H‐tryptophan incorporation). By proper choice of label, the effect of the biomaterial on cellular proliferation or production of macromolecules or both may be assessed. Materials with a cytotoxic effect cause inhibition of incorporation of radioactive label in the above assays. The cell monolayers can also be inspected microscopically for evidence of cytotoxicity. The method is quantitative, simple, reproducible, rapid, and suitable for screening of a large number of samples.
Novel mode of contraception using polymeric hydrogels. I
Authors: Singh Harpal , Vasudevan Padma , Misro Manmohan , Ray Alok R. , Guha Sujoy K. 
Published: December 2004

AbstractA new method of fertility control has been proposed and tested. The technique involves the use of the polymer, which when injected into the vas deferens lowers the pH sufficiently so as to kill the spermatozoa passing through. The polymer provides an acidic environment for a prolonged time and slowly erodes. The fertility may be restored after complete solubility of the polymer itself over a period of time or by flushing it with a suitable solvent. This method of male contraception is nonsurgical, nonocclusive, and reversible.
Permeability of heparinized hydrophilic polymer (H‐RSD): Application to semipermeable membrane for microencapsulation of activated charcoal
Authors: Mori Yuichi , Nagaoka Shoji , Tanzawa Hiroshi , Kikuchi Tetsuya , Yamada Yosuke , Hagiwara Masaru , Idezuki Yasuo 
Published: December 2004

AbstractA series of heparinized hydrophilic polymers (H‐RSD) composed of a hydrophobic element, a nonionic hydrophilic element, a cationic element and ionically bound heparin was synthesized. The permeability of the H‐RSD polymers with various chemical compositions and water contents was investigated. From the studies on the permeability, it has been found that in order to maintain good permeability after heparinization, the nonionic hydrophilic element is necessary. In addition, the microencapsulation of activated charcoal granules using a H‐RSD polymer with a similar permeability to that of Cuprophan was examined. In vitro adsorption studies and in vivo direct hemoperfusion studies on the activated charcoal microencapsulated with the H‐RSD polymer, show that the H‐RSD coating prevents clot formation without loss of the absorption power of the activated charcoal.
Hemostatic and healing studies of sodium amylose succinate (IP760)
Authors: Jeffery Diane L. , Dressler Donald P. , Anderson James M. , Gallagher Michael J. 
Published: December 2004

AbstractAcute and chronic studies were performed in the canine model to evaluate a new topical hemostatic agent in terms of initial hemostatic capability and tissue/material interaction during the healing process. IP760, a porous amylose succinate material, was applied to large spenic surface wounds in six acute and twelve chronic animals. Microfibrillar collagen (Avitene) was used in twelve chronic animals for comparison. While the hemostatic capabilities of the two agents were comparable, marked differences were noted in the healing response. In the IP760‐treated wound sites the acute inflammatory response, granulation tissue infiltration with fibrosis and healing occurred earlier and in a more homogeneous manner than in the Avitene‐treated wound sites. Healing of the IP760‐treated wounds occurred concomitantly with the development of granulation tissue and fibrosis and the rapid resorption of the IP760.
Phase identification and incipient melting in a cast Co‐Cr surgical implant alloy
Authors: Kilner T. , Pilliar R. M. , Weatherly G. C. , Allibert C. 
Published: December 2004

AbstractPhase relationships in cast CoCr surgical implant alloys, heat treated at temperatures from 1180 to 1300°C, are reported. Interdendritic material was identified by selected area diffraction as a quaternary near eutectic mixture between sigma phase, M23C6, M7C3, and fcc Co. Incipient melting and subsequent resolidification of this near‐eutectic mixture accounts for observations of behavior at temperatures above 1235°C. At temperatures just below its melting point the interdendritic material initially breaks down to M23C6, which subsequently dissolves in the Co matrix.
The biocompatibility of polypyrrolidone in test implantation
Authors: Šprincl L. , Kušková M. , Roda J. , Králíček J. 
Published: December 2004

AbstractThe biological compatibility of polypyrrolidone was investigated using subcutaneous implantation in rats. Acute (10 days) and chronic (360 days after implantation) tissue reaction was characterized numerically and compared with poly(2‐hydroxyethyl methacrylate), used in the Drug Control Research Institute in Prague as a standard in the evaluation of polymers, for which good tolerance in the clinical practice has been demonstrated. Surface changes in the polymer were evaluated by using a scanning electron microscope.
The effect of pH on the in vitro degradation of poly(glycolide lactide) copolymer absorbable sutures
Authors: Chu C. C. 
Published: December 2004

AbstractThe pH effect on the hydrolytic degradation of Polyglactin 910 copolymer was studied in terms of the tensile properties of the suture specimens. The use of a cord/yarn grip, newly designed specifically for fibrous materials, eliminated the grip‐induced failure. Different degrees of hydrolytic degradation of this copolymer at 3 different pH levels were observed. The suture specimens exhibited the best retentions of breaking strength at the physiological pH of 7.44, while the specimens at pH = 10.09 showed the fastest loss of breaking strength. Thus, a maximum retention of tensile properties occurred around the pH level of 7.0, whereas smaller percentages of retention of tensile properties were observed at both acidic and strong alkaline solutions. This synthetic absorbable suture material exhibits the basic characteristic of hydrolysis which is catalyzed by both acid and base.
The effects of proteins on metallic corrosion
Authors: Clark G. C. F. , Williams D. F. 
Published: December 2004

AbstractThe corrosion of the pure metals aluminium, cobalt, copper, chromium, molybdenum, nickel, and titanium and of a cobalt‐chromium molybdenum casting alloy has been studied in buffered saline with and without the presence of the proteins serum albumin and fibrinogen. The corrosion of aluminium and titanium was unaffected by the protein. The corrosion rates of chromium and nickel showed a slight increase, while cobalt and copper dissolved to a very much greater extent in the presence of protein. However, with molybdenum the corrosion was inhibited by protein.
The education of the biomaterialist: Report of a survey, 1980–81
Authors: Black Jonathan 
Published: December 2004

AbstractBiomaterials as a class includes a wide variety of both artificial and natural materials. The discipline of Biomaterials must be recognized as the study of the materials aspects of both fabricated materials and natural tissues, as well as their interactions. Emerging disciplines give rise to academic establishments. A survey of 97 U.S. and Canadian universities reveals a wide range in institutional settings and course offerings in Biomaterials. Plans for faculty additions suggest that the field is still actively expanding.
The effect of oxidation of copoly(L‐alanine, L‐methionine) membranes on oxygen permeability and tensile properties
Authors: Aiba Sei‐ichi , Minoura Norihiko , Fujiwara Yukihiko 
Published: December 2004

AbstractThis study pertains to the development of poly(α‐amino acid) membranes which have potential as biomaterials. Copoly(L‐alanine, L‐methionine) membranes have been subjected to oxidation which produced a hydrophilic structure allowing the improvement of oxygen permeability. L‐Methionine residues in the copolymers were converted to methionine sulfoxide and/or sulfone groups by action of hydrogen peroxide in various reaction compositions. Water absorption, permeability to oxygen dissolved in water, and tensile strength of the modified membranes were changed with the extent of oxidation. The water absorption was found to increase with oxidation time from 10 to 300%. The oxidation time dependency on the oxygen permeability coincided with the increase in the water absorption. The permeability coefficients of oxidized membranes were of the order of 10−9 cm3 (STP) cm/cm2 s cm Hg, while those of unoxidized membranes were approximately 10−11. As expected, the tensile strengths of oxidized membranes were smaller than those of unoxidized ones. In addition, the effect of L‐alanine and L‐methionine residue composition on the membrane properties is discussed.
The viscosity of acrylic bone cements
Authors: Krause William R. , Miller Jo , Ng Philip 
Published: December 2004

AbstractThe viscosity of the acrylic bone cement used in total joint arthroplasty is an important material property for determination of the proper handling characteristics and interlock with bone. In this article the rheological properties of the three leading bone cements were determined over a three‐decade range of shear rates. In addition, four other cements were tested at a single shear rate. The results indicate that all the acrylic bone cements are non‐Newtonian, pseudoplastic materials with significant differences between them. It is shown that the viscosity increases at different rates with respect to increases in time. For the majority of cements there is a steady or increasing rate of viscosity change with time.
Considerations on manufacturing principles of a synthetic burn dressing: A review
Authors: Chvapil Milos 
Published: December 2004

AbstractThis review presents various considerations on the construction of a synthetic burn dressing, based mainly on collagen protein. Membranous wound covers are compared with sponge‐felt types, monocomponental with composite. The importance of collagen crosslinking agent and the nonextractibility of any component from the dressing material are discussed. According to the type of the burn the dressing should be used dry or wet, plain or medicated, and changed often to reduce substantially the presence of necrotic tissue, inflammatory cells of the granulation tissue, and bacterial contamination.
The evaluation of new dental resins prepared with polyfunctional methacrylate monomers
Authors: Suzuki Shiro , Nakabayashi Nobuo , Masuhara Eiichi 
Published: December 2004

AbstractThe combinations of several composite fillers and dimethacrylates for crown and bridge resins were investigated. The composite filler prepared from TMPT markedly improved the mechanical and physical properties of crown and bridge resins. The enhancement of the mechanical and physical properties is due to the highly crosslinked structure which is developed with the use of the reactive composite filler which copolymerizes with the matrix monomer. The combination of the 2.6E‐UDMA comonomer and the TMPT composite filler exhibited the maximum compressive strength, transverse strength, and Brinell hardness, and minimum abrasion loss and thermal expansion. This hard resin was superior to the resins currently available for clinical use.
Sulfonated poly(vinylidene fluoride) as a biomaterial: Immobilization of urokinase and biocompatibility
Authors: Aoshima R. , Kanda Y. , Takada A. , Yamashita A. 
Published: December 2004

AbstractThe adsorption of urokinase (UK) on sulfonated poly(vinylidene fluoride) (PVDF) films was examined. The amount of adsorbed UK on sulfonated PVDF films increased linearly with the degree of the ion exchange capacity (IEC) of sulfonated film. Moderately sulfonated PVDF film (IEC = 0.25 meq/g) adsorbed 3 IU/cm2 UK, and highly sulfonated film (IEC = 0.54 meq/g) adsorbed 5 IU/cm2 UK. All UK‐immobilized PVDF films were active for ten weeks. The presence of the sulfonated films in the culture of rat lymphocytes did not result in any change of their viability. The implant of the film (IEC > 0.48 meq/g) into the subcutaneous layer of rats resulted in the cell infiltration composed of lymphocytes and plasma cells or the blastogenesis within the surrounding tissues of the implant and the regional lymph nodes. On the contrary, the implant of the films (IEC < 0.27 meq/g) did not exert any visible changes, indicating that the lightly sulfonated films may be applicable in the sense of biocompatibility in vivo.
Polyphosphazenes: Effect of molecular motions on thrombogenesis
Authors: Reichert W. M. , Filisko F. E. , Barenberg S. A. 
Published: December 2004

AbstractThe effect and interrelationship between primary (segmental backbone) and secondary (side chain) molecular motions on thrombogenesis, independent of morphological order/disorder, crystallinity, and/or associated water is elucidated using an amorphous hydrophobic polymer of poly‐[(trifluoroethoxy) (fluoroalkoxy)phosphazene], PNF. The results indicate that thrombogenesis for an amorphous hydrophobic polymer is sensitive and dependent on the degrees and types of primary and secondary molecular motions at the polymer interface.
Rheological studies of the polymerization of elastomeric impression materials. I. Network structure of the set state
Authors: Cook Wayne D. 
Published: December 2004

AbstractAs part of the detailed study of the curing of a range of dental elastomeric impression materials, their chemistry was investigated. This information, the dependence of the stress relaxation modulus of the set material on the catalyst/base ratios, and the level of diluent were used to elucidate the network structure. Such information is required before the rheological behavior during cure can be understood. The clinical significance of the recommended catalyst/base ratio is discussed.
Application of immunoperoxidase method to electron microscopic observation of plasma protein on polymer surface
Authors: Noishiki Yasuharu 
Published: December 2004

AbstractThe immunoperoxidase technique was applied to observe the electron microscopic presence of human plasma protein on a polymer surface. Two types of polymer material, i.e., Dacron and a newly synthesized heparinized hydrophilic polymer (H‐RSD, Toray Industries, Inc.), showed different reactions to human plasma proteins. The hydrophobic Dacron showed a decreased affinity for plasma albumin, but a greater affinity for fibrinogen, α1‐lipo‐protein, and β‐lipoprotein when compared to H‐RSD. The thrombo‐resistant H‐RSD showed a relatively strong affinity for albumin, but in a spotty or focal manner. Most of the H‐RSD surface did not adsorb albumin. Fibrinogen adsorption was observed in areas smaller than albumin adsorption. The adsorption of fibrinogen appeared to occur through certain material. The α‐lipoprotein and β‐lipoprotein were not adsorbed on the H‐RSD. The immunoperoxidase method is a sensitive and useful technique in studying the interactions between plasma proteins and the surface of polymer materials.
Blood–materials interactions: The minimum interfacial free energy and the optimum polar/apolar ratio hypotheses
Authors: Coleman D. L. , Gregonis D. E. , Andrade J. D. 
Published: December 2004

AbstractNumerous hypotheses exist to explain observed blood–materials interactions. It is the purpose of this article to test two popular hypotheses, namely, the minimum interfacial free energy hypothesis and the optimum polar/apolar ratio hypothesis. Methacrylate polymers and copolymers were characterized using the captive bubble underwater contact angle method; bulk water content was determined by gravimetric methods; streaming potential measurements were made; and surface roughness and possible particulate contamination were evaluated by reflected light microscopy. In vitro blood tests include whole blood clotting time measurements on polymer‐coated tubes; centrifugal force platelet adhesion on polymer‐coated coverslips; and a measure of the partial thromboplastin time, Russell's viper venom time (Stypven time), and the prothrombin time of native whole blood exposed to polymer‐coated microscope slides. Results suggest that platelet adhesion correlates in the opposite direction of whole blood clotting time and partial thromboplastin time, emphasizing the need for a multiparameter approach to blood–materials testing. Based on these tests the minimum interfacial free energy hypothesis is not supported. In fact, the data suggest the opposite to be true. It is apparent that platelet adhesion can be a misleading indicator of blood compatibility. Neither hypotheses can explain the apparent conflict between the platelet adhesion data and the coagulation time data.
Analysis of retrieved implants: Crystallinity changes in ultrahigh molecular weight polyethylene
Authors: Grood Edward S. , Shastri Ranganath , Hopson Clark N. 
Published: December 2004

AbstractThe extent of in vivo induced structural alterations were evaluated in 13 retrieved implants ranging from two weeks' to seven years' implantation. A statistically signifiant difference in crystallinity was seen between weight‐bearing and non‐weight‐bearing region, regions of the implants. Further, in the weight‐bearing region, crystallinity was higher in components implanted for two or more years than in those implanted for less than one‐half year. These results were consistent with our prior in vitro study on the effects of sterilization and aging. Taken together, the data indicate that UHMW polyethylene is not a static material but is continually undergoing dynamic changes in vivo.