bluuebunny/crossref_metadata_2025_split huggingface dataset:
Corrosion currents of dental amalgams
Authors: Grajower Rafael , Greener Evan H. 
Published: December 2004

AbstractThe polarization resistance and anodic polarization curves of three amalgam types were determined in saline solution. Corrosion currents were determined by extrapolation of anodic Tafel slopes. A good correlation was found between corrosion currents and reciprocal polarization resistances, according to Ic = 0.02/PR.
An in vivo model for evaluating the response of pulp to various biomaterials
Authors: McClugage Sam G. , Holmstedt Jan O. V. , Malloy Randy B. 
Published: December 2004

AbstractAn in vivo model has been designed to study the acute response of exposed or unexposed dental pulp to the topical application of various biomaterials. This model permits sequential microscopic observations of the microvascular system of dental pulp before and after application of pulp capping agents, cementing agents, or cavity liners. The use of this experimental model provides useful information related to the tolerability of dental pulp to various biomaterials used in dentistry. Furthermore, this model serves as a useful supplement to more traditional long term methods for evaluating the biocompatability of dental materials.
Dynamic mechanical properties of amalgams
Authors: Kusy R. P. , Greenberg A. R. 
Published: December 2004

AbstractA recently developed dynamic mechanical analysis technique was utilized to determine the setting rates of dental amalgams. Via a compound parallel beam apparatus the dynamic mechanical properties of five amalgam materials were continuously measured at 37°C within ca. 7 min after the start of trituration. Over a 15 hr period results showed that the modulus of elasticity (Ea) increased from 1.2 × 1010 Pa to 6.5 × 1010 Pa—the latter generally approaching those values reported via ultrasonic techniques. Moduli results via compression tests on microspecimens (3 × 2 × 1 mm) paralleled previous reliable literature data, nominally yielding values for Ea of 2–3 × 1010 Pa. The extent of Ea scatter from both inter‐ and intrapreparer experiments appeared similar, although superior technique generally could be recognized by a systematic shift of the mean results to higher Ea's. In addition to modulus studies both compressive strengths (σmax) and their corresponding strains (ϵ) were measured on microspecimens at a strain rate (ϵ) of 0.031 min−1, with a significant increase being noted in σmax for the one material tested at over an order of magnitude increase in ϵ.
Thrombogenesis: An epitaxial phenomena. I
Authors: Barenberg S. A. , Anderson J. M. , Mauritz K. A. 
Published: December 2004

AbstractA semiempirical epitaxial model has been derived which correlates and interrelates the surface free energy, ultrastructural morphology, surface charge, surface chemistry, and surface molecular motions of a model triblock copolymer to thrombogenesis. This paper addresses the aspect of: (1) ultrastructure order versus disorder, (2) primary and secondary molecular motions, (3) surface and side chain chemistry, (4) thrombogenesis, and (5) the derived epitaxial model based on the above observations. This model can be extrapolated to include and predict the relative thrombogenic responses of various crystalline and semicrystalline polymeric substrates, i.e., aliphatic polyolefins, polyurethanes, and polypeptides.
A clinical experience with the NCGT graft
Authors: Reddy K. , Haque S. N. , Cohen L. , Sophie Z. , Feller J. , Stillman R. M. , Fitzgerald J. , Stanczewski B. , Sawyer P. N. 
Published: December 2004

AbstractA comparison of 130 grafts done in 101 patients included 47 veins, 25 Johnson & Johnson dialdehyde‐starch‐tanned collagen prostheses, and 58 NCGT grafts that had been followed for a 40‐month period. This study had documented the fact that in spite of frequent poor runoff, a useful result is provided by the NCGT graft apparently due in part to its built‐in nonthrombogenic structure providing a cumulative patency of 73%. The patency rate was even superior with venous bypasses. Therefore, we still feel that the autogenous vein provides the most useful bypass conduit available in vascular reconstruction. In situations where a vein could not be used or was not available the NCGT graft offers an equally useful nonthrombogenic surface to maintain prolonged patency. Thus, collagen appropriately modified can provide a useful prosthesis in vascular reconstruction.
Adsorption characteristics of plasma fibronectin in relationship to biological activity
Authors: Grinnell Frederick , Feld Marian K. 
Published: December 2004

AbstractWe studied the adsorption properties of plasma fibronectin (pFN) on wettable tissue culture (TC) dishes and nonwettable bacteriological (BAC‐T) dishes in relationship to its biological activity of promoting fibroblast spreading. The binding of pFN to the dish surfaces was found to be very tight and partially resistant to treatments with 1M NaOH, 2% SDS, 8M urea, or 6M guanidine HCl. Only the combination of trypsin (1 mg/ml) followed by 1M NaOH resulted in complete recovery of surface bound material. The amount of surface bound pFN did not directly correlate with its activity when comparing TC and BAC‐T dishes. At low concentrations, more pFN adsorbed onto the surfaces of BAC‐T dishes than TC dishes, but the adsorbed material was biologically less active on BAC‐T dishes. At high concentrations, pFN adsorbed similarly on both dish surfaces reaching a maximum level of 320 ng/cm2 or 4.4 X 1011 molecules/cm2. The possibility was considered that pFN unfolded into an inactive conformation when adsorbed on BAC‐T dishes at a low concentration but that at high concentrations, molecular packing requirements prevented unfolding. Evidence in favor of this hypothesis was the observation that addition of 50 μg/ml of serum albumin simultaneously with low pFN concentrations resulted in adsorption of pFN on BAC‐T dishes in an active conformation even though the amount of adsorbed pFN decreased. Competition experiments between pFN and other proteins were carried out, and it was found that pFN has a much higher affinity for BAC‐T or TC dish surfaces than albumin or fibrinogen. It was also found that mild heat denaturation of albumin increased its affinity for the surface by an order of magnitude.
Biodegradation of a poly‐(α‐amino acid) hydrogel. II. In vitro
Authors: Dickinson Helen R. , Hiltner Anne 
Published: December 2004

AbstractProteolytic enzymes have been employed in an in vitro model to simulate the in vivo degradation of a synthetic poly(amino acid) hydrogel. Trypsin and collagenase had no effect on crosslinked poly(2‐hydroxyethyl‐L‐glutamine) but pronase and papain dissolved the hydrogel. The initial effect of papain was to decrease the effective cross‐link density without producing soluble material. This effect was similar to that observed previously in vivo. Analysis of the papain digestion products showed that oligomers of degree of polymerization 4–9 were the chief products. The rate at which oligomers were formed increased with increasing crosslink density. This phenomenon was attributed to hydrophobic effects.
An evaluation of ion‐textured aluminum oxide dental implants
Authors: Weinstein A. M. , Cook S. D. , Klawitter J. J. , Weinberg L. A. , Zide M. 
Published: December 2004

AbstractA study was undertaken to evaluate the ion‐beam texturing of aluminum oxide as a means of providing a surface which will produce a biological prosthetic attachment. A wafflelike pattern of surface contours 150 × 75 × 35 μm deep was produced on cylindrical dental implants. The textured surfaces were compared to the as received surfaces in adult mongrel dogs. Implants were inserted into surgically modified healed extraction sites and were left in place for six months. Post‐sacrifice mechanical testing was used to quantify the displacement response of the implants.The clinical, radiographic and mechanical testing evaluations did not reveal any statistically significant differences in the performance of the dental implants. However, it was observed that anatomical site and mandibular geometry with respect to implant size play a significant role in affecting implant retention.
The tensile creep characteristics of dental amalgam. I. Stress dependence
Authors: Cruickshanks‐Boyd D. W. , Roswati N. 
Published: December 2004

AbstractEquipment is described which enables the determination of the creep behavior of small specimens of dental amalgam under tensile stresses. The apparatus has been used to measure the creep strain of both low and high copper dental amalgams at 34°C, in the stress range 9.4 to 38.8 MNm−2, for time periods of up to 24 h. Significant differences were found in the controlling creep mechanisms for the various amalgam types. Conventional amalgam displayed classical steady‐state creep. The high copper amalgams, however, were best represented by transient creep equations implying interference to the motion of dislocations by the presence of hardening precipitates.
Cu2O and CuCl2·3Cu(OH)2 corrosion products on copper rich dental amalgams
Authors: Marshall Sally J. , Lin Jiin‐Huey C. , Marshall Grayson W. 
Published: December 2004

AbstractIn addition to Sn‐rich corrosion products found in conventional amalgams, Cu‐rich amalgams also form Cu‐containing corrosion products. The nature of these Cu‐rich products was investigated by immersion of samples of 13 Cu‐rich amalgam systems in Ringer's solution for prolonged periods. SEM/EDS and x‐ray diffraction studies were used to identify the compounds formed and their morphology. Two products were identified: Cu2O, a red product, and CuCl2·3Cu(OH)2, a green product.
A fabric pouch for maintaining transducer and catheter terminations
Authors: McCutcheon Ernest P. , Evans Joyce M. , Wibel Franklin H. 
Published: December 2004

AbstractManagement of the chronically instrumented animal is improved by enclosing the terminations of catheters and transducer wires in a subcutaneous nylon velour pouch. Six or more days after implantation, an opening is made into the pouch by removing a portion of the overlying skin; subsequent healing processes provide a satisfactory bond. Thereafter the leads can be extracted and replaced without need for anesthesia or dissection. Results in 35 animals (26 dogs and 9 monkeys) for intervals up to four months showed fibrous encapsulation was complete in 28 and partial in 7, with no mortality or significant morbidity attributable solely to the presence of the pouch. Gross and microscopic tissue examination indicated a localized foreign body reaction in response to the nylon fibers. The technique is especially useful in experimental protocols for which continuous restraint is undesirable, such as the chronically instrumented primate periodically exposed to environmental stress.
Toxicity evaluation of a novel filler free silicone rubber biomaterial by cell culture techniques
Authors: Chawla Attar S. 
Published: December 2004

AbstractCytotoxicity of a novel filler free silicone rubber (FFSR) was evaluated by studying its effect on mouse L929 cells. Silastic and a laboratory rubber tubing (RT) were used as control materials. Three different experimental methods were used. In method A, after six days of cell culturing in the sample extracts, there were 95, 80, and 50% of control viable cells for FFSR, Silastic, and RT, respectively. Similarly, in method B, after six days of direct contact between samples and the cells, there were 80, 40, and 20% of control viable cells for FFSR, Silastic, and RT, respectively. For the Agar Overlay Test, method C, the cells under the FFSR samples were normal and healthy compared to those under Silastic and RT. From these studies it was concluded that FFSR had the least cytotoxicity of the three materials studied.
Long‐term in vivo studies of poly(2‐hydroxyethyl methacrylate)
Authors: Imai Yohji , Masuhara Eiichi 
Published: December 2004

AbstractPoly(hydroxyethyl methacrylate) (PHEMA) was implanted subcutaneously in rats, hamsters, and guinea pigs for up to 24, 23, and 13 months, respectively. The tissue response and tumorigenesis caused by PHEMA were compared among the three species of the animals. Thick fibrous capsule formation and tumor production were noted only in rats, while no tumorigenesis and thin fibrous capsule formation were observed in hamsters and guinea pigs.These results support our previous hypothesis that animals producing a thick and avascular capsule tend to develop tumors at the implant site. PHEMA retrieved was characterized by scanning electron microscopy and x‐ray energy dispersive analysis. Calcium and phosphorus were the main elements detected on the surface of PHEMA implants. PHEMA is suggested to be not suitable for long‐term implant material.
Enzymatic removal of formalin‐fixed tissues from polyester arteries, and its effect on physical properties of fibers
Authors: Needham D. K. , Buchanan D. R. , Gupta B. S. , Horton H. R. 
Published: December 2004

AbstractA method is presented that can be utilized for the removal of formalin‐fixed tissues from arterial grafts without. Affecting fiber material properties. Such a method could prove highly useful for studying the changes in the structure and properties of graft fiber as functions of important clinical variables. Information on what actually happens to the arterial graft material in situ with passage of time is greatly lacking in the current graft literature. The method proposed involves treatment of the formalin fixed fiber–tissue complex with an enzymatic preparation containing enzymes derived from the porcine pancreas (pancreatin) in solution with tris(hydroxymethyl) aminomethane buffer at pH 7.6. Studies with two different grafts—a Microknit Dacron Bifurcation from a clinical patient 10¼ years after implantation and stored in formalin for 11 months, and a Sauvage Filamentous Velour of Dacron from an animal 24 h after implantation and stored in formalin for nine months—showed that the treatment was highly effective in completely removing the tissues at concentrations of pancreatin as low as 2.5%. The same treatment given to the virgin yarns of grafts revealed no significant effects on tensile, dimensional, and morphological properties.
Polymer analogs of 3‐chloro‐4‐benzyloxyphenylacetic acid and their pharmacological activity
Authors: Hrabák F. , Grimová J. , Maturová E. , Kuchař M. 
Published: December 2004

AbstractPolymer analogs of 3‐chloro‐4‐benzyloxyphenylacetic acid (BPh) were prepared, representing esters of BPh with three polymer alcohols: poly(vinyl alcohol) (P‐I), poly(2‐hydroxyethyl methacrylate) (P‐II), and poly(2,3‐dihydroxypropyl methacrylate) (P‐III). Their anti‐inflammatory activity was determined by testing their inhibitory effect on the growth of edema in the hind legs of rats. The relative activities of the esters P‐I‐BPh and P‐II‐BPh with respect to that of BPh are 0.06 and 0.10, respectively. In the case of P‐III‐BPh the activity is stronger (0.37), probably owing to the easier release of BPh from P‐III‐BPh due to hydrolysis. No prolonged effect of BPh polymeric esters could be achieved.
In vivo and in vitro aging of orthopedic aluminas
Authors: Fahr A. , Brown R. F. , Day D. E. 
Published: December 2004

AbstractThe flexural strength, microstructure and relative Ca and Si concentration at the surface of two commercial orthopedic aluminas were studied before and after aging up to 52 weeks in simulated body fluids or in subcutaneous implantation in rodents. There was no significant reduction in flexural strength after aging, but there was evidence of Ca and Si dissolution from the external grain boundary surfaces, particularly for specimens aged in demineralized water. No change occurred in the Ca and Si concentrations within the specimen's bulk during either in vivo or in vitro aging.
A method for the prediction of protein adsorption on implant surfaces
Authors: Bagnall Robert David , Arundel Philip Anthony 
Published: December 2004

AbstractA simple method is described for predicting aspects of the adsorptive behavior of selected plasma proteins on a wide range of implant surfaces from a limited number of interfacial free energy measurements. Although the theoretical basis of the predictive treatment is open to debate, it is suggested that the method may be of value in the further understanding of implant biocompatibility.
In vitro electrochemical corrosion study of coupled surgical implant materials
Authors: Griffin Charles D. , Buchanan R. A. , Lemons J. E. 
Published: December 2004

AbstractThe objective of this study was to produce corrosion behavior data for each of the commonly used metallic alloys in surgical implants. In addition, by applying the known electrochemical corrosion theory, the study aims to predict the behavior of galvanic couples made of any two of the materials. From this predicted behavior, potentially useful couples that are not expected to show significantly increased corrosion rates were identified.
Influence of the suture diameter on the tensile strength of polypropylene monofilaments and its relationship to the USP specification
Authors: Kusy R. P. , Whitley J. Q. 
Published: December 2004

AbstractEthylene gas sterilized polypropylene monofilaments were tested in a straight pull as well as in a conventional knot pull tensile test. In either case an analysis of the results indicates that the occurrence of “surface steps” may explain the relationship between strength and suture diameter. The present investigation not only shows that the polypropylene specification could be established on a more fundamental basis (using 60% of the ultimate tensile strength as the generalized criterion) but also suggests that other sutures should be evaluated similarly.
Inhibition of surface induced coagulation by preadsorption of albumin‐heparin conjugates
Authors: Hennink W. E. , Kim S. W. , Feijen J. 
Published: December 2004

AbstractSurface coatings of the albumin‐heparin conjugates were developed to improve the blood compatibility of polymeric materials. Glass, PVC, Biomer and cellulose acetate were coated with albumin‐heparin conjugate and its adsorption and desorption behavior on glass in particular was studied using 3H and 51Cr radiolabeled conjugates. Precoated materials showed a significant prolongation of the Lee‐White clotting time as compared with noncoated ones. It was demonstrated that the prolonged clotting time for pretreated glass was due to surface bound conjugate. Prolonged recalcification times of plasma exposed to glass, Biomer, and PVC were obtained using albumin‐heparin conjugate precoated surfaces. Albumin‐heparin conjugates with high affinity for antithrombin III gave more prolonged clotting times as low affinity conjugates when used as coatings for glass. This indicates that the behaviour of heparin in preadsorbed conjugates resembles that of heparin in solution.
The electrical stimulation of bone using a filamentous carbon cathode
Authors: Zimmerman M. , Parsons J. R. , Alexander H. , Weiss A. B. 
Published: December 2004

AbstractFilamentous carbon fiber is an extremely compatible biomaterial. It does not corrode and elicits almost no foreign body response. In addition, this material is an efficient electrical conductor in vivo. These desirable characteristics suggest that carbon fiber may be of use as an electrode material for the stimulation of bone and/or soft tissue growth. This possibility has been investigated in a well established laboratory animal model. When used as a cathode material in conjunction with an implantable constant direct current device, carbon fiber was shown to be an effective electrode material for the stimulation of bone and fibrous tissue within the medullary canal of the tibia of the rabbit. Further, adjustment of current levels appear to allow some selectivity in terms of the amount and type of tissue produced. Currents in the 1 m̈A range produced a maximum amount of bone, whereas a 20 μA current produced a maximum amount of fibrous tissue. Intermediate current levels produced a proportional mix of bone and soft tissue.
Blood distribution of nickel, cobalt, and chromium following intramuscular injection into hamsters
Authors: Merritt K. , Brown S. A. , Sharkey N. A. 
Published: December 2004

AbstractIn vivo experiments were undertaken to study the transport of metal ions away from the intramuscular (IM) injection site and to study the binding of the metals to blood cells. Hamsters were injected intramuscularly with metal salts or with corrosion products generated by fretting corrosion of 316 LVM stainless steel or MP‐35N plates and screws. The animals were bled at 0 time, and 2, 4, 6, 24, 48, and 96 h after injection. The concentration of nickel, cobalt, and chromium in the serum, attached to red cells, and attached to white cells was determined. This study showed that metals are rapidly transported from the intramuscular site with high levels in the blood by 2 h. The level of metal in the blood varied considerably with nickel being transported in high concentration to the blood, chromium with a valence of 6+ being transported to the blood, and cobalt and chromium with a valence of 3+ being transported less to the blood. The highest amount of cell binding was observed with chromium 6+. Cobalt showed negligible binding to blood cells. When all the metal salts injected together were compared with the individual salts injected alone, there was no difference. This indicated that the each metal behaves independently of the presence of the others.
Assessment of tissue reactions to biomaterials: A model system using the foreign body response in the mouse lung to intravenously injected divinyl copolymer beads
Authors: Hood C. Ian , Schoen Frederick J. , Coleman Sylvia E. , Mickley Linda D. 
Published: December 2004

AbstractWe have developed a reproducible model of granuloma formation in the mouse lung using a narrow size range (45–53 μm) of divinyl benzene copolymer beads as a standard test material. Approximately 10,000 beads are given by intravenous injection into the tail veins of mice whence they embolize to the lung and incite granuloma formation. This delivery system eliminates the superimposed inflammatory reaction due to trauma that occurs when materials are directly implanted at the test site by surgical incision. Granuloma size was quantitated at intervals from 3 h to 6 weeks by tracing mid‐bead granuloma areas on the ground glass screen of a light microscope at a known magnification and measuring the areas with a digitizer interfaced with a microcomputer programmed to prepare histograms and to merge data from replicate experiments. At 3 h only a few polymorphonuclear leukocytes could be observed adhering to the beads. At 48 h, the time of maximum granuloma size (mean area = 750l μm2), the granulomas consisted of both polymorphonuclear and mononuclear leukocytes. After 6 weeks, the granulomas were smaller, composed predominantly of mononuclear leukocytes and had a mean area of 2893 m̈m2. This model system allows the analysis of a large number of measurements, is reproducible, and provides a useful method for comparing the hosts' inflammatory response to a variety of potential biomaterials, as well as for determining the effectiveness of anti‐inflammatory drugs.