Showing papers in "Journal of Biomedical Materials Research in 1982"
TL;DR: Scanning electron microscopic studies suggested that the monomers possess affinity with the hard tissue as indicated by the good adhesion provided by the interlocking at the tubules.
Abstract: The effectiveness of 4-methacryloxyethyl trimellitate anhydride (4-META) on the adhesion of an acrylic rod with etched dentine and enamel was studied. Etching of tooth substrates with a 10% citric acid-3% ferric chloride solution prior to the adhesion proved effective. Monomers with both hydrophobic and hydrophilic groups like 4-META promoted the infiltration of monomers into the hard tissue. The infiltrated monomers polymerized in situ and good adhesion with the tooth substrates took place. The tensile adhesive strength was 18 MPa on the etched dentine. Scanning electron microscopic studies suggested that the monomers possess affinity with the hard tissue. The good adhesion was not provided by the interlocking at the tubules as had been considered previously.
1,404 citations
TL;DR: 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.
Abstract: The 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.
238 citations
TL;DR: The mechanical tests indicated an increasing strength of tissue attachment with increasing implantation time and pore size range, which was found to be collagenized fibroconnective tissue.
Abstract: Twenty-four rectangular metal plates were fabricated with surface regions in three different pore size ranges (5-20 microns, 20-50 microns, 50-200 microns). The plates were implanted into the dorsal subcutaneous tissue of 12 adult mongrel dogs for periods of 4, 8, 12, and 16 weeks. After animal sacrifice, the fibrous tissue which adhered to the porous-surfaced regions of each plate was mechanically peeled off to give an indication of the strength of tissue attachment. The tissue was examined by both transmitted light and scanning electron microscopy. At each time period, the tissue that contacted the porous regions was found to be collagenized fibroconnective tissue. The mechanical tests indicated an increasing strength of tissue attachment with increasing implantation time and pore size range. The largest pore size range of approximately 50-200 microns produced a mean peel strength of attachment of 27.5 g/mm at the 16-week period.
205 citations
TL;DR: Test two popular hypotheses, namely, the minimum interfacial free energy hypothesis and the optimum polar/apolar ratio hypothesis, 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.
Abstract: Numerous 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.
143 citations
TL;DR: In this article, the authors used a prosthetic replacement of the canine stifle joint as an animal model and found that the fibrous tissue proved to be a very compliant, deformable material and to undergo very large strains with load.
Abstract: A long-term problem associated with total joint replacements is the formation of a fibrous tissue at the bone-cement interface which may compromise the fixation of the prosthesis. In this study, harvestable amounts of interfacial fibrous tissue were generated using a prosthetic replacement of the canine stifle joint as an animal model. The collected tissues were examined histologically and by uniaxial, unconfined compression tests. The fibrous tissue had a matlike structure. The heavy collagen fibers were distributed at random in sheets and the sheets themselves were layered to form a mat. Such a structure may be able to resist compressive stresses normal to the plane of the mat but is probably not well suited to resist shearing stresses. The fibrous tissue proved to be a very compliant, deformable material and to undergo very large strains with load. The stress-strain curve for the tissue was nonlinear and was characterized by large deformations at low loads. But with increasing loads, the material became stiffer, and at high loads, the stress-strain curve became linear with a short-term tangent modulus of 1.9 MPa at a stress level of 0.5 MPa and a compressive strain level of 50%. With regard to total joint replacement systems which consist of an outer bone shell followed by a thin layer of fibrous tissue, a mantle of PMMA cement and a central core of metal or UHMW polyethylene, the fibrous tissue is substantially more yielding and deformable than the other elements of the structure and may have a significant effect on the structural behavior of the system.
141 citations
TL;DR: 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 cell of the granulation tissue, and bacterial contamination.
Abstract: This 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 cell of the granulation tissue, and bacterial contamination.
114 citations
TL;DR: Interdendritic material was identified by selected area diffraction as a quaternary near eutectic mixture between sigma phase, M23C6, M7C3, and fcc Co.
Abstract: Phase relationships in cast Co--Cr surgical implant alloys, heat treated at temperatures from 1180 to 1300 degrees 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 degrees C. At temperatures just below its melting point the interdendritic material initially breaks down to M23C6, which subsequently dissolves in the Co matrix.
112 citations
TL;DR: The morphological observations on the surface changes of poly-(glycolic acid) sutures which have been exposed to various dosages of gamma irradiation and duration of immersion in a physiological saline buffer report the formation of surface cracks on the filaments.
Abstract: This article reports the morphological observations on the surface changes of poly-(glycolic acid) sutures which have been exposed to various dosages of gamma irradiation (0, 2.5, 5.0, 10, 20 and 40 Mrad) and duration of immersion (0, 7, 14, 28, 48, 60, and 90 days) in a physiological saline buffer. The most important gross morphological characteristics of PGA suture hydrolytic degradation is the formation of surface cracks on the filaments. The regularity of the surface cracks increased with an increase in the gamma irradiation and the duration of hydrolysis. Surface cracks were not observed in irradiated sutures that had not been subjected to hydrolytic degradation. The arrangement of the surface cracks, their orientation on the filaments, and the direction of crack propagation provide very useful information for depicting the mechanism of hydrolytic degradation in this class of fibrous material. The microfibrillar model of fiber structure has been used as the basis for the proposed degradation mechanism of PGA in vitro. It is believed that hydrolysis occurs initially in the amorphous regions sandwiched between two crystalline zones, as tie-chain segments, free chain ends, and chain folds in these regions degrade into fragments. As degradation proceeds, the size of the fragments reachesmore » the stage at which they can be dissolved into the buffer medium. This dissolution removes the fragments from the amorphous regions, and surface cracks appeared.« less
107 citations
TL;DR: The possibility that bone-implant adhesion might be improved by introducing molecules relevant to cell-substrate attachment into the biomaterial prior to implantation is raised.
Abstract: We have demonstrated that an established hamster cell line (NIL 8 M-2) will adhere to the bioceramic bioglass. The rate at which the NIL 8 M-2 cells assume a spread morphology on bioglass is density dependent and the morphology displayed by NIL 8 M-2 cells attached to bioglass is much more elongated than that displayed by NIL 8 M-2 cells attached to nonreactive glass. Precoating the bioglass with the plasma form of human fibronectin significantly reduces the density dependent nature of cell spreading. Coating the bioglass with fibronectin also reduces the time required for cell spreading and changes the morphology of the attached cells from an elongated to an extremely flattened shape. Our work raises the possibility that bone-implant adhesion might be improved by introducing molecules relevant to cell-substrate attachment into the biomaterial prior to implantation.
95 citations
TL;DR: 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.
Abstract: The 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.
86 citations
TL;DR: All the acrylic bone cements used in total joint arthroplasty are non-Newtonian, pseudoplastic materials with significant differences between them and it is shown that the viscosity increases at different rates with respect to increases in time.
Abstract: The 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.
TL;DR: It has been shown that an annealed thin film PMMA precoating, applied in a low-contact-angle form to surgical alloy surfaces devoid of weak boundary layers, satisfies the majority of the requirements during interface formation.
Abstract: It has been argued that various specific requirements based on known principles of good adhesion are not being met in the current procedures of formation of the implant–bone cement interface. It has been shown that an annealed thin film PMMA precoating, applied in a low-contact-angle form to surgical alloy surfaces devoid of weak boundary layers, satisfies the majority of the requirements during interface formation. Techniques for the application of the precoating have been developed for SS316LVM, Co-Cr-Mo, and Ti-6Al-4V based on fracture toughness and fatigue tests, and fractography of the interface. Implant surface preparation methods have been established to yield surfaces amenable to adhesive bonding. The composition of the coatings have been studied from the point of view of implant surface wetting, coating roughness and thickness, and interface strength. A biocompatible silane coupling agent (A-174), currently used in orthodontics, has been introduced to provide saline resistant interfaces. The final precoated metal–bone cement interfaces have demonstrated fracture toughnesses in excess of that of bone cement even after prolonged exposure to 37°C physiological saline. Fatigue tests have shown that the fatigue lives (6.5 MPa) of the precoated metal interfaces in saline are at least twice, and in one case several orders of magnitude greater than, that of the uncoated ones even when the latter are tested dry. Fractography of the interfaces show failures that are entirely cohesive in nature. For the UHMWPE (ultrahigh molecular weight polyethylene)-bone cement interface, similar improvement with precoating, however, could not be attained. Finally, the coated metal–bone cement interfaces have been tested as a function of some clinical variables such as cement type, joining time, clinical contamination, and sterilization procedure. Results show that coated metals exhibit a certain level of insensitivity to these variables and retain their performance under all conditions except after particular repeated sterilizations.
TL;DR: Some of the linear prepolymer, poly(methyl methacrylate) (PMMA), had been incorporated into the crosslinked polymer system, and the gel fraction of the auto-polymerized pour-type materials corresponded to the quantity of reacted monomers, whereas the conventional auto- polymerized materials took an intermediate position between pour type materials and heat-polymers.
Abstract: The purpose of this investigation was to determine residual monomers, the insoluble gel fraction, and singly reacted dimethacrylate monomers in heat-polymerized, auto-polymerized conventional and pour-type denture base materials. Residual monomers were determined by HPLC analysis of tetrahydrofuran extracts of denture base polymers. The gel fraction was determined by gravimetric analysis of the nonextractable portion. The pendant methacrylate groups in the gel fraction were determined by quantitative IR (infrared) spectrometry. It was demonstrated that the heat-polymerized materials had the lowest content of residual monomers. Generally, the content of pendant methacrylate groups in the gel was dependent on the initial quantity of crosslinking agent in the monomer liquids. The gel fractions of the heat-polymerized materials were larger than the quantity of reacted monomers and were also dependent on the quantity of crosslinking agent. These findings showed that some of the linear prepolymer, poly(methyl methacrylate) (PMMA), had been incorporated into the crosslinked polymer system. The gel fraction of the auto-polymerized pour-type materials corresponded to the quantity of reacted monomers, whereas the conventional auto-polymerized materials took an intermediate position between pour type materials and heat-polymerized materials in this respect.
TL;DR: The setting reaction of six dental materials has been studied by using a water dilatometer at 25 degrees and 37 degrees C to give reproducible values of the setting shrinkage and shows a clear physical picture of the entire setting process.
Abstract: The setting reaction of six dental materials has been studied by using a water dilatometer at 25 degrees and 37 degrees C. Where there is no water absorption during the test, the method gives reproducible values of the setting shrinkage and at the same time shows a clear physical picture of the entire setting process. This method is suitable for adaptation as a specification test for setting shrinkage and has good potential for being used as a supplementary or substitute test for initial and final set times.
TL;DR: The data indicate that UHMW polyethylene is not a static material but is continually dynamic changes in vivo, consistent with prior in vitro study on the effects of sterilization and aging.
Abstract: The 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
TL;DR: Radioimmunoassays of plasmas used in in vitro platelet tests and of buffers used in prostacyclin leakage studies established that these effects are not due to the release of prostacyClin from the respective immobilization substrates.
Abstract: Owing to the chemical instability of prostacyclin, the direct immobilization of this prostaglandin has not been successful. A new procedure is described for the preparation of immobilized prostacyclin based on the conversion of immobilized prostaglandin F2 alpha to immobilized prostaglandin I2-Materials thus prepared show dramatic antiplatelet effects with regard to platelet aggregation and platelet adhesion. Radioimmunoassays of plasmas used in in vitro platelet tests and of buffers used in prostacyclin leakage studies established that these effects are not due to the release of prostacyclin from the respective immobilization substrates.
TL;DR: Using unfilled resins as bonding agents between the composites and enamel resulted in increased bond strength with half of the Composites, and mechanical properties that were most highly correlated with bond strength to enamel were proportional limit and elastic modulus.
Abstract: The strength of bonding of dental composites to enamel was measured in shear. The compressive strength, proportional limit, elastic modulus, and tensile strength of the composites were measured for correlation with the bond strength. Conventional and microfilled composites with a range of filler concentrations were studied. The densities of the composites and their fillers and the concentrations of the fillers were determined. The mechanical properties that were most highly correlated with bond strength to enamel were proportional limit and elastic modulus. Tensile strength and filler concentration had lower correlation coefficients, and compressive strength was not correlated with bond strength. Using unfilled resins as bonding agents between the composites and enamel resulted in increased bond strength with half of the composites.
TL;DR: It is concluded that large compressive stresses cause structural damage at the leaflet attachment, which may explain the clinical observation that bioprosthetic leaflets detach or calcify in this region.
Abstract: During the normal functioning of aortic porcine bioprosthetic valves, the leaflets undergo complex configurational changes which can produce stresses large enough to damage the leaflets. Stress analyses of these valves in vivo have not been performed before. We investigated the behavior of aortic bioprostheses in vivo in calves by placing radiopaque markers on the valves and observing them under x-ray. Based upon the behavior of the leaflets, a method of stress analysis is proposed. Membrane stresses were associated with a pressure gradient across the leaflet and bending stresses with a change in the leaflet curvature. Total stresses were obtained by summation of the two stresses. A model of leaflet deformation at its attachment is proposed and the stresses determined. In diastole, the total stresses in the leaflet were tensile. In systole, the total stresses at the leaflet attachment were large and compressive on the aortic surface. Since the leaflet is unable to sustain compressive stresses, it is concluded that large compressive stresses cause structural damage at the leaflet attachment. This may explain the clinical observation that bioprosthetic leaflets detach or calcify in this region.
TL;DR: It is postulated that the hysteresis behavior exhibited by the passivated alloy is due to processes involving a breakdown of the pre-established passive film followed by a repassivation characteristic of the saline electrolyte.
Abstract: The objective of this investigation was to evaluate the in vitro and in vivo susceptibilities of a surgical cobalt-chromium-molybdenum alloy to localized corrosion. In vitro cyclic anodic polarization curves were generated for the cobalt alloy under various surface and electrolyte conditions. Surfaces of the test specimens were examined before and after each polarization experiment. In vivo analyses involved macroscopic and microscopic examinations of cobalt alloy surfaces on retrieved total hip prostheses. The electrolyte selected for the in vitro polarization study was 0.9% saline at a pH of 7.00 ± 0.05 and temperature of 37 ± 1°C in both aerated and deaerated conditions. Surface conditions for the cobalt alloys included nonpassivated and passivated treatments. Hysteresis behavior was exhibited by the passivated alloy but not by the nonpassivated alloy. According to the protection potential theory, hysteresis behavior indicates a material should be susceptible to pitting corrosion. Therefore, based on polarization curves and theory, the results of the present study indicated the cobalt alloy was susceptible to pitting corrosion when in the passivated condition but not when in the nonpassivated condition. Examination of the surfaces before and after each polarization curve revealed no evidence of pitting corrosion. Also, the examination of nonwear cobalt surfaces of total hip prostheses with implantation times up to 6 years revealed no features uniquely identified as the result of pitting corrosion. Therefore, it was hypothesized that certain conditions inherent in the electrochemical phase of this study had caused the development of hysteresis behavior for the passivated alloy, and this hysteresis behavior should not be associated with pitting corrosion as is normally taken to be the case by application of the protection potential theory. Instead, it is postulated that the hysteresis behavior exhibited by the passivated alloy is due to processes involving a breakdown of the pre-established passive film followed by a repassivation characteristic of the saline electrolyte.
TL;DR: Weibull analysis of the tensile tests indicated that monotonic fracture was governed more strongly by strain than stress, and the number of cycles to fatigue failure was more strongly controlled by strain amplitude than stress amplitude.
Abstract: Monotonic tensile tests and tension-compression fatigue tests were conducted of wet acrylic bone cement specimens at 37 degrees C. All testing was conducted in strain control at a strain rate of 0.02/s. Weibull analysis of the tensile tests indicated that monotonic fracture was governed more strongly by strain than stress. The number of cycles to fatigue failure was also more strongly controlled by strain amplitude than stress amplitude. Specimen porosity distribution played a major role in determining the tensile and fatigue strengths. The degree of data scatter suggests that Weibull analysis of fatigue data may be useful in developing design criteria for the surgical use of bone cement.
TL;DR: The results support the previous hypothesis that animals producing a thick and avascular capsule tend to develop tumors at the implant site and suggest PHEMA is suggested to be not suitable for long-term implant material.
Abstract: Poly(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.
TL;DR: The crystallinity of the apatites showed similar patterns of variation with the degree of fluoridation irrespective of carbonate content, and appear analogous to the complex pattern of the fluoridated hydroxyapatites previously reported.
Abstract: To study the effect of fluoride on the physicochemical properties of carbonate-containing apatites, two series of fluoridated CO3 apatites with various fluoride contents were synthesized at 80 degrees C and pH 74 The alpha-axis dimensions of these apatites decreased with the increase of both fluoride and carbonate contents The crystallinity of the apatites showed similar patterns of variation with the degree of fluoridation irrespective of carbonate content These patterns appear analogous to the complex pattern of the fluoridated hydroxyapatites previously reported In contrast to this unexpected crystallinity phenomena, the apparent solubility of fluoridated CO3 apatites in acetate buffer solutions at pH 40 and 60 and 37 degrees C decreased monotonically with increasing degree of fluoridation and approached that of fluoridated hydroxyapatites at high fluoride content Dissolution rate of fluoridated CO3 apatite pellets at pH 40 also showed a simple decrease with increasing degree of fluoridation and was extremely sensitive to acid at low fluoride content
TL;DR: Interposing dentine powder between the test cells and the material ameliorated the effects of all materials, possibly by the absorption of toxic components.
Abstract: A system is described for assessing the toxicity of freshly mixed restorative materials in vitro by measuring changes in the levels of beta-galactosidase and lactic dehydrogenase in both cultured cells and supernatants. The toxic effects of a zinc phosphate and silicate cement, a composite, and zinc oxide/eugenol were studied on two cell types, macrophages and fibroblasts, after 24 h exposure. Zinc oxide/eugenol, Silicap, and zinc phosphate were toxic to macrophages, in that order; Concise appeared to be nontoxic. Only zinc oxide/eugenol exerted significant effects on fibroblasts. Interposing dentine powder between the test cells and the material ameliorated the effects of all materials, possibly by the absorption of toxic components.
TL;DR: The present results indicate that the precoated hemiarthroplastic implants provide a firmer intramedullary fixation than the traditional, uncoated implants.
Abstract: In order to minimize the problems associated with implant fixation using acrylic bone cement, a new technique has been investigated. Canine hip prostheses were precoated with self-curing acrylic bone cement and implanted in random source dogs using the same cement for fixation, a precoated prosthesis on one side and an uncoated (control) on the other. After 1, 3, and 6 months, both femora were excised and sectioned for mechanical assessment of the interfaces among bone, cement, and implant. It was found that the precoated implants had much higher interfacial shear strengths than the uncoated ones (average 14.2 and 6.8 MPa for implant-cement interface; 2.0 and 1.2 MPa for the cement-bone interface for all implant periods). The precoated "old" cement and the "new" cement's interfacial shear strength was the strongest with an average of 15.1 MPa for all implant periods. The present results indicate that the precoated hemiarthroplastic implants provide a firmer intramedullary fixation than the traditional, uncoated implants.
LGC1
TL;DR: 13C NMR spectroscopy of the fluid cement pastes have shown that tartaric acid reacts more readily than the polyacid with the glass, and hence suppresses the premature gelation of the cement.
Abstract: D(+) tartaric acid is incorporated into glass–ionomer cements to control the setting properties. 13C NMR spectroscopy of the fluid cement pastes have shown that tartaric acid reacts more readily than the polyacid with the glass, and hence suppresses the premature gelation of the cement. As the cements set, the pH rises from ca. 1.25 to ca. 3 when tartaric acid is fully complexed. As the polyacid reacts the pH rises further to ca. 5.
TL;DR: In addition to Sn-rich corrosion products found in conventional amalgams, Cu-rich amalgams also form Cu-containing corrosion products, which were investigated by immersion of samples of 13 Cu- rich amalgam systems in Ringer's solution for prolonged periods.
Abstract: In 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.
TL;DR: A direct correlation was found between corrosion properties and cytotoxic response and the biological effect was assessed as cytotoxicity in vitro.
Abstract: Data from earlier investigation of Au-Cu-Ag ternary alloys indicate that there may be a relationship between an alloy's corrosion behavior and its biological effects. Corrosion properties were determined using standard potentio dynamic techniques and the biological effect was assessed as cytotoxicity in vitro. Linear mathematical methods were used to analyze the data and model the systems. A direct correlation was found between corrosion properties and cytotoxic response.
TL;DR: It is suggested that clinically important abrasive wear will not be a late complication of cardiac valve replacement with pyrolytic carbon prostheses.
Abstract: To assess abrasive wear of mechanical valve prostheses containing pyrolytic carbon components, we recovered at necropsy or surgery and analyzed by scanning electron microscopy and surface profilometry eight prostheses. Seven were implanted for 30–85 (mean 50 months). Valves included DeBakey aortic (2), DeBakey mitral (1), Beall mitral (2), Bjork–Shiley aortic (1), Cooley–Cutter mitral (1), and Lillehei–Kaster (L–K) tricuspid (1). All carbon occluders had undetectable wear. Carbon cage struts had a superficial burnish. Metallic struts had insignificant wear marks. In contrast, a Teflon Beall Model 104 valve implanted for 34 days and similarly analyzed had considerable material loss from the cage struts. This study suggests that clinically important abrasive wear will not be a late complication of cardiac valve replacement with pyrolytic carbon prostheses.
TL;DR: No malignant neoplasms developed at the test or control operation sites during the time periods for which the animals survived, compared with that from a previous study by Health, Freeman and Swanson, who observed sarcomas in rats at sites of intramuscular injection of cobalt-chromium-molybdenum particles suspended in horse serum.
Abstract: A study has been made of the sarcogenicity of particles of cobalt-chromium-molybdenum alloy. The particles were implanted as a dry powder into a surgical incision into the dorsal paraspinal muscle of adult female rats and guinea pigs. Two preparations were used. In one, the particles had a size range of 100-250 micrometers. This preparation was implanted into 51 Wistar rats. In the other, the particles had a size range of 0.5-50 micrometers, 85% being in the range 0.5-5 micrometers. This preparation was implanted into 61 Wistar rats, 53 hooded rats, and 46 Dunkin Hartley guinea pigs. Sham operations were carried out on a control group of 50 Wistar rats. No malignant neoplasms developed at the test or control operation sites during the time periods for which the animals survived. This negative finding contrasts with that from a previous study by Health, Freeman and Swanson, who observed sarcomas in rats at sites of intramuscular injection of cobalt-chromium-molybdenum particles suspended in horse serum. Possible explanations for this difference in results are discussed.
TL;DR: A three-dimensional finite element stress analysis has been used to investigate the influence that variations in the infrastructural geometry of a blade-type dental implant have on the stress distribution around LTI carbon and aluminum oxide implants.
Abstract: A three-dimensional finite element stress analysis has been used to investigate the influence that variations in the infrastructural geometry of a blade-type dental implant have on the stress distribution around LTI carbon and aluminum oxide implants. The finite element model was constructed based upon an analysis of serial sections of a retrieved implant specimen. In addition to the implant, the finite element model contained a three-unit fixed bridge connected to a natural molar with periodontal membrane. The removal of the bridge allowed for the study of freestanding implants and molar. Variations in the implant blade geometry were found to produce significant changes in the stress distributions around bridged and freestanding aluminum oxide implants. Very little effect, however, was observed around the LTI carbon implants. A comparison of the stresses around the freestanding molar and the stresses around the bridged and freestanding implants was made to determine the implant dessign that came closest to reproducing the stress state around the modeled molar. The LTI carbon system that best achieved this stress state was found to be a full-blade implant used in conjunction with a tooth as an abutment in a fixed bridge. The aluminum oxide system that best achieved this stress state was found to be of the post or short-blade design used as a freestanding implant.