bluuebunny/crossref_metadata_2025_split huggingface dataset:
Chemical and physical properties of collagen implants influence their fate in vivo as evaluated by light and confocal microscopy
Authors: Vardaxis N. J. , Ruijgrok J. M. , Rietveld D. C. , Marres E. M. , Boon M. E. 
Published: May 2005

AbstractPorcine collagen membranes having a rough and a smooth side were used for subcutaneous implantation studies in rats. Two tanning protocols were used for the membranes, a new one involving microwaving and glutaraldehyde treatment (NEWGA), and the other, a conventional method using glutaraldehyde treatment at room temperature (OLDGA). Untreated membranes (NONGA) were also implanted. Sections of the implants were examined by light microscopy and with the confocal laser scanning microscope focusing on neovascularization and incorporation of the implant. At 64 days, the smooth sides of NEWGA and OLDGA implants were not well incorporated, with scarring subjacent to the surface and dystrophic calcification of that side of the membrane. At the same time, the rough sides of the NEWGA and OLDGA were not calcified with a giant cell reaction around the porcine collagen. The best incorporation was found in the NONGA membranes with no dystrophic calcification, excellent neovascularization of all layers, and complete remodeling at day 64. After 5 months, the completely remodeled NONGA membrane still could be identified, and the NEWGA and OLDGA membranes were calcified with a giant cell reaction having a dense fibrous capsule. It is concluded that if cross‐linking is deemed necessary, the microwave cross‐linking method is advisable because in the early stages there is less reactive inflammation around it, and the implant surfaces should be rough with an open structure, making calcification of crosslinked collagen unlikely. © 1994 John Wiley & Sons, Inc.
Bonding of low‐fusing dental porcelain to commercially pure titanium
Authors: Könönen M. , Kivilahti J. 
Published: May 2005

AbstractThe objective of the investigation was to study the basic problems related to the firing of dental porcelain to commercially pure titanium. The firing of a low‐fusing porcelain to sandblasted or electrolytically polished titanium was carried out in an ordinary dental furnace. The interfacial regions between the ceramic coatings and titanium were analyzed using scanning acoustic microscopy (C‐SAM) and scanning electron microscopy (SEM) techniques. Thermal stresses in the joints were evaluated by means of a finite element model based on multilayer elastic strain analysis. The chemical reactions and their formation sequence at 750°C was predicted thermodynamically and observed experimentally both at 750 and 800°C. The C‐SAM results gave evidence that the integrity of the porcelain‐titanium joints are better in the sandblasted samples than in the elecropolished ones, where defects were larger. SEM analyses of the same samples confirmed the C‐SAM findings. Because the reaction layers are more continuous in the electropolished samples, cracks propagated more readily in these samples during the cooling procedure. Both thermodynamic calculations and experimental chemical analyses strongly indicate that the cause for the cracking of the reaction zone is thin layer of Ti (oxo) silicide and/or a relatively thick solid solution layer of Ti and oxygen. © 1994 John Wiley & Sons, Inc.
Transmission electron and high‐voltage electron microscopy of osteocyte cellular processes extending to the dental implant surface
Authors: Steflik D. E. , Sisk A. L. , Parr G. R. , Lake F. T. , Hanes P. J. , Berkery D. J. , Brewer P. 
Published: May 2005

AbstractExamination of the morphology of osteocytes within the bone supporting endosteal dental implants was performed using conventional transmission and high‐voltage transmission electron microscopy (HVEM). The in vivo dog model used 72 implants inserted into the premolar region of 18 experimental animals. Forty‐eight implants in 12 dogs were used as anterior abutments for fixed bridges for periods up to 12 months. The mineralized matrix of the supporting bone was either directly apposed to the implant surface or was separated from the implant by a narrow region of unmineralized matrix. Osteocytes were routinely observed to be closely associated with the bone‐implant interface, as well as at a distance from the implant. Osteocytes were found to extend cellular processes directly to the implant surface through canaliculi. The osteocyte processes contained microfilaments. The three‐dimensional capabilities of HVEM elucidated the nature of these cell processes at the point of exit from the osteocyte, as the processes extended through the mineralized matrix, and as the processes terminated at the implant interface. This report suggests that avenues of communication may exist between the implant and the osseous cells, providing intriguing hypotheses regarding biomechanical forces and osteogenesis at the implant interface. Furthermore, an electron‐dense deposit was observed upon the inner confines of the canalicular wall, upon the outer aspects of the osteocyte lacuna, and upon the outer aspect of the bone interfacing the implant. © 1994 John Wiley & Sons, Inc.
Healing of large segmental defects in rat femurs is aided by RhBMP‐2 in PLGA matrix
Authors: Lee S. C. , Shea M. , Battle M. A. , Kozitza K. , Ron E. , Turek T. , Schaub R. G. , Hayes W. C. 
Published: May 2005

AbstractRecombinant human bone morphogenetic protein‐ (rhBMP‐) can be used to enhance the repair of congenital or acquired bone pathologies when formulated in the appropriate carrier. Poly [D, L‐(lactide‐co‐glycolide)] (PLGA) has been shown to be an effective carrier of rhBMP‐. We investigated several particle sizes PLGA and several doses of rhBMP‐ in a rat orthotopic model. We also investigated the effects of a fibrinolytic inhibitory agent, epsilon aminocaproic acid (EACA), on the healing response. Our data indicate that higher doses of rhBMP‐ resulted in increased failure torque (408 ± 70 N‐mm or 60% of the intact value) and higher incidence of union (100%). The induced bone in femurs treated with the smaller particle size PLGA achieved the greatest torsional stiffness and strength. The presence of rhBMP‐ was necessary for new bone to form, but the presence of EACA did not change these results; the use of the PLGA carrier appeared to increase bone strength and stiffness. In fact, with higher doses of rhBMP‐ in PLGA, the stiffness of the new bone was equal to that of intact controls (64 ± 20 N‐mm/deg [intact femurs] versus 45 ± 10 N‐mm/degree [medium dose in small PLGA], 61 ± 17 N‐mm/degree [high dose in small PLGA], and 36 ± 11 N‐mm/degree [medium dose in large PLGA]; P > .05). In conclusion, PLGA implanted with rhBMP‐ effectively aided in healing large segmental defects in rat femurs. © 1994 John Wiley & Sons, Inc.
Adherent platelet morphology on adsorbed fibrinogen: Effects of protein incubation time and albumin addition
Authors: Sheppard J. I. , McClung W. G. , Feuerstein I. A. 
Published: May 2005

AbstractThe composition of the protein layer adsorbed to a polymer has been thought to be important for the adhesion of platelets. The state of activation of adherent platelets is an additional factor that may be a predictor of biocompatibility. Activation refers to the degree of change from discoid shape to any of several spread shapes. The conformation and orientation of adsorbed adhesive proteins, which interact with receptors on the membrane of platelets, such as fibrinogen, fibronectin, and von Willebrand factor, may also be important for platelet adhesion and activation. This work deals with the behaviour of fibrinogen adsorbed to PMMA alone, where the experimental variable was incubation time with the substrate, and with adsorbed fibrinogen mixed with albumin, where the experimental variable was the molar percent of fibrinogen in the adsorption solution. Shorter protein incubation times and increased albumin levels in the initial fibrinogen adsorption solution enhanced the percentages of activated platelet morphologies and increased adsorbed fibrinogen redistribution by the platelet. Lower concentrations of albumin in the initial adsorption solution enhanced platelet adhesion numbers; fibrinogen incubation time had no effect. Together, these factors can contribute to the biocompatibility of a biomaterial through their effect on platelet adhesion and activation. © 1994 John Wiley & Sons, Inc.
Long‐term durability of the interface in FRP composites after exposure to simulated physiologic saline environments
Authors: Meyer Matthew R. , Friedman Richard J. , Del Schutte H. , Latour Robert A. 
Published: May 2005

AbstractFiber/matrix interfacial bond strength significantly influences the mechanical behavior of fiber‐reinforced polymer (FRP) composites. Interfacial bond strength durability is therefore particularly important in the development of FRP composites for implant applications where diffused moisture may potentially weaken the material over time. In this study, the long‐term durability of interfacial bonding in carbon fiber/380 grade polyetheretherketone (C/PEEK) and carbon fiber/polysulfone (C/PSF) composites was investigated after exposure to hygrothermal environments. A single fiber pull‐out test was used to quantitatively determine the ultimate bond strength (UBS) of the samples following exposure. Samples were tested at three temperatures (37, 65, and 95°C) for six time periods (0–5000 h) and in two environments (dry and physiologic saline‐immersed). A mathematical model based on nth order chemical reaction kinetics was applied to describe the long‐term durability of the interface. The results of this study indicate that interfacial bond strengths in C/PSF and C/PEEK (380 grade) composites are significantly decreased by exposure to physiologic saline and are functions of both time and temperature. For each material, the kinetics of degradation analysis predicts further bond strength losses following initial saturation, which then stabilizes at temperature‐dependent equilibrium bond strength levels. © 1994 John Wiley & Sons, Inc.
Studies on two new radiopaque polymeric biomaterials
Authors: Kruft M. A. B. , Benzina A. , Bär F. , van Der Veen F. H. , Bastiaansen C. W. M. , Blezer R. , Lindhout T. , Koole L. H. 
Published: May 2005

AbstractTwo new polymeric materials (polymers A and B) containing covalently bound iodine were prepared. These polymers were evaluated with respect to their possible use as radiopaque implant biomaterials—that is, materials that are visible in a noninvasive manner using routine X‐ray absorption imaging techniques. Polymer A is a copolymer of methyl methacrylate (MMA) and 1 (80 and 20 mol%, respectively). Polymer B was prepared from MMA, 1, and 2‐hydroxyethyl methacrylate (HEMA) (mol ratio 65:20:15, respectively). Compound 1 was synthesized from 4‐io‐dophenol and methacryloyl chloride. The resulting polymers were characterized with GPC, DSC, NMR, and by measuring both the advancing and receding contact angles. Thrombogenicity of the polymers was determined by an in vitro thrombin generation test procedure. The maximum concentration of free thrombin was 76 ± 1 nM for polymer A, and 64 ± 3 nM for polymer B. The lag times (i.e., time onset of thrombin generation) were 392 seconds for polymer A and 553 seconds for polymer B. For PVC‐T, which is known as a passive material, a lag time of 583 seconds was found. This indicates that polymer B is comparable to PVCT, and more passive than polymer A. Polymer A exhibited minor activation of platelets. Polymer B did not induce platelet activation at all. The polymers exhibited, even as fibers with a diameter of ca. 0.3 mm, good radiopacity with routine imaging X‐ray techniques in the clinic. It is argued that polymers A and B—which actually represent a whole family of radiopaque polymeric biomaterials—exhibit promising properties with respect to applications as construction materials for a new generation of endovascular stents. © 1994 John Wiley & Sons, Inc.
Effect of Ca/P coating resorption and surgical fit on the bone/implant interface
Authors: Maxian Suzanne H. , Zawadsky Joseph P. , Dunn Michael G. 
Published: May 2005

AbstractThe effect of coating resorption on bone apposition and attachment strength to resorbable hydroxyapatite (HA), nonresorbable HA‐coated, and uncoated rough titanium implants was evaluated in interference‐ and noninterferencefit (gap of 2–3 mm) surgical models 2, 4, and 12 weeks postoperatively. Interference and noninterference fits showed differences in bone bridging. Bone apposition was circumferential around the implants in noninterference fit. Significantly greater bone apposition was seen to nonresorbable HA‐coated implants than uncoated and resorbable HA‐coated implants at 4 and 12 weeks. Only resorbable HA coatings showed significantly lower bone apposition for noninterference versus interference fit and from 4–12 weeks. At 2 weeks, strengths of bone attachment to resorbable HA‐coated implants were greater than the other implants, and decreased to lower values (not significant) than the nonresorbable HA‐coated implants at 4 and 12 weeks. Differences in push‐out shear strengths between interference‐ and noninterference‐fit surgical models were significant for uncoated implants at 4 weeks, but not for HA‐coated implants at any time period. Significant differences were seen between the three implant types only for the noninterference‐fit model, where the HA‐coated implants showed greater strengths than the uncoated implants (significant at 2 and 4 weeks). This study showed that presence of resorbable or nonresorbable HA coatings is beneficial when a gap of 2–3 mm is present between the implant and the bone. The resorbable HA‐coated implants showed greatest strengths at the early time period. At later time periods, resorbable HA‐coated implants showed lower bone apposition and attachment strengths than nonresorbable HA coatings. However, resorbable HA‐coated implants showed equivalent bone apposition and attachment to uncoated implants, suggesting that HA coating resorption and remodeling at the bone/implant interface can provide good osteoconduction and fixation. © 1994 John Wiley & Sons, Inc.
Dissolution/reprecipitation and protein adsorption studies of calcium phosphate coatings by FT‐IR/ATR techniques
Authors: Ong J. L. , Chittur K. K. , Lucas L. C. 
Published: May 2005

AbstractThe surfaces of bioactive Ca‐P ceramics immediately change when exposed to proteinaceous solutions. The dissolution behavior and protein interactions of these bioactive materials at the bone/implant interface need to be investigated to understand their material‐cellular interactions fully. In this study, FT‐IR/ATR techniques were used to study the in situ phosphate release kinetics of Ca‐P coatings. The net loss of phosphate molecules from coatings was slower in saline solutions compared with α‐MEM solutions. Coatings exposed to α‐MEM solutions containing fibronectin released phosphate molecules slower than coatings exposed to α‐MEM solutions containing albumin. Conformational changes in fibronectin and albumin adsorbed onto Ca‐P and uncoated germanium surfaces were also investigated using FT‐IR/ATR spectroscopy. Analysis of changes in the amide I bands indicated that there was a greater loss of β‐sheet structure in adsorbed fibronectin on Ca‐P coatings when compared with bare germanium surfaces. Although albumin did change its structure upon adsorption on both Ca‐P and germanium, unlike fibronectin, adsorbed albumin structure was similar on Ca‐P coatings and germanium. Furthermore, with time the conformation of adsorbed fibronectin and albumin appeared to be very stable on Ca‐P coatings, whereas albumin adsorbed to germanium exhibited an increase in ratio of α‐helix to βturn. © 1994 John Wiley & Sons, Inc.
Selective adhesion of platelets on a polyion complex composed of phospholipid polymers containing sulfonate groups and quarternary ammonium groups
Authors: Ishihara Kazuhiko , Inoue Hikaru , Kurita Kimio , Nakabayashi Nobuo 
Published: May 2005

AbstractWe investigated the effects of electrical charges on cellpolymer interactions of poly[2‐methacryloyloxyethyl phosphorylcholine(MPC)‐co‐n‐butyl methacrylate (BMA)] (PMB) having excellent blood compatibility, by copolymerizing anionic or cationic methacrylates with MPC and BMA. A polyion complex (PIC) composed of anionic and cationic MPC copolymers was also prepared. When the cell adhesion on these polymer surfaces from rabbit whole blood was evaluated, we observed a considerable reduction in cell adhesion on the MPC copolymers compared with that on poly(BMA), even when the MPC copolymer was electrically charged. On the other hand, many platelets selectively adhered to the PIC surface from whole blood, but the adherent platelets maintained a discoid shape. The amount of adenosine triphosphate (ATP) in platelets adherent on the PMB or the PIC from a platelet‐rich plasma (PRP) was more than 75% of that in the original PRP, which indicated that the activity of these platelets remained high. However, in the platelets adherent to poly(BMA), only a small amount of ATP remained. Protein adsorption on the polymer surface from human plasma was investigated using a goldcolloid‐labeled immunoassay against albumin γ‐globulin, and fibrinogen. Many of these proteins adsorbed on poly(BMA), whereas a small amount of protein was observed on the MPC copolymers that had an electrical charge. Albumin adsorption and suppression of γ‐globulin and fibrinogen adsorption were found on the PIC. Therefore, the introduction of electrical charges in the PMB did not have an adverse effect on cell adhesion and protein adsorption. The PIC composed of anionic and cationic MPC copolymers induced considerable adsorption of albumin and selective adhesion of platelets. Furthermore, the adherent platelets suppressed changes in their shapes and activity. © 1994 John Wiley & Sons, Inc.
In vitro hydroxyapatite deposition onto a film surface‐grafted with organophosphate polymer
Authors: Tretinnikov O. N. , Kato K. , Ikada Y. 
Published: May 2005

AbstractTo produce a bone‐bonding polymer surface that is capable of inducing deposition of a hydroxyapatite (HA) layer in the body fluid, an organophosphate polymer was covalently immobilized onto a high‐density polyethylene film by surface graft polymerization of a phosphate‐containing monomer. The grafted film was immersed in simulated physiologic solution (SPS). The chemical composition and structure of the formed apatite layer as well as its bonding strength to the polymer surface were investigated. To distinguish the effect of phosphate groups on the deposition of apatite layer from the simple calcium absorption by the anion, a comparative study was done using a polyethylene film with surface immobilized carboxylic groups. Calcium phosphate deposition was observed on all the materials investigated, but the kinetics, composition, deposit amount, and bonding strength of the new phase were found to be significantly different among the modified materials, depending on the density and chemical nature of the surface immobilized ionic groups. It was found that the polymeric materials modified by surface graft polymerization of a phosphate‐containing monomer produce a carbonated HA layer firmly bonded with the material upon immersion in SPS. Carboxyl groups in the grafted layer was not enough to activate bonding with the HA layer. © 1994 John Wiley & Sons, Inc.
Endothelial injury during extracorporeal circulation: Neutrophil–endothelium interaction induced by complement activation
Authors: Matsuda Takehisa , Itoh Satoshi , Anderson James 
Published: May 2005

AbstractThis study was designed to understand the physiologic intravascular and intradevice events at the cellular level following complement system activation during extracorporeal circulation. The addition of anaphylatoxin C5a or complement‐activated serum into neutrophil‐ or endothelial cell‐suspensions resulted in a dose‐dependent transmembrane stimulation that was assessed by an intracellular free calcium ion mobilization technique using a calcium‐sensitive photoprotein, aequorin. The adhesion and ruffle formation of neutrophils on endothelial cell monolayers were markedly enhanced when both cell types were treated with C5a or activated serum. The significance of complement activation on intravascular events during extracorporeal circulation is emphasized and discussed from the viewpoint of surface‐expressed adhesion molecules. © 1994 John Wiley & Sons, Inc.
Splenic response to silicon drain material following intraperitoneal implantation
Authors: Guo Weidun , Willén Roger , Liu Xiaoying , Odelius Rolf , Carlén Brigitta 
Published: May 2005

AbstractTo study the splenic response to intraperitoneal biomaterials, 100% silicon rubber drain fragments were intraperitoneally implanted in the rat. Four days after implantation, specimens of the spleen and implanted rubber fragment were retrieved and subjected to scanning electron microscopy (SEM) and energy dispersive X‐ray microanalysis (EDX). In SEM, macrophages with membrane fusion and cytoplasmic spreading were noted on the surfaces of implanted rubber fragments. Specimens of the spleen from animals with implants showed light 3–10‐μm structures that were not observed in those without implants. EDX revealed the presence of silicon both in the rubber fragment and in the spleen of the implanted animals. Both light microscopy and transmission electron microscopy showed a large number of particles inside giant cells of the spleen. The present study demonstrated an active transport of rubber fragments containing silicon from the peritoneal cavity to the spleen by adherent macrophages, reflecting a splenic response to intraperitoneal implantation of biomaterials. The modes of silicon rubber degradation and transportation remain to be elucidated. © 1994 John Wiley & Sons, Inc.
Drug release from a novel self‐setting bioactive glass bone cement containing cephalexin and its physicochemical properties
Authors: Otsuka Makoto , Matsuda Yoshihisa , Kokubo Tadashi , Yoshihara Satoru , Nakamura Takashi , Yamamuro Takao 
Published: May 2005

AbstractA novel device containing cephalexin as a model drug using a self‐setting bioactive cement based on CaOSiO2P2O5 glass was investigated. The device consisted of 95 wt/wt% glass powders and 5 wt/wt% cephalexin powder hardened within 5 min after mixing with a phosphate buffer. After setting, in vitro drug release from homogeneous orheterogeneous drug‐loaded cement pellets in a simulated body fluid (SBF) at pH 7.25 and 37°C continued for over 4 weeks. The hardened cement gradually formed low‐crystallinity hydroxyapatite with high bioactivity in hard bone tissue and reduced in volume by about 5% during dissolution testing in SBF. Consequently, 30% of the loaded drug was squeezed from the cement system at the initial stage of the drug release, and the remainder released more slowly. Because the heterogeneous system consisting of the cement and drug‐loaded pellet avoided the drug‐squeezing effect, it showed a longer drug release term than the homogeneous drug‐loaded cement. The heterogeneous system using the hardened cement after soaking in SBF at 37°C for 10 days showed very slow drug release at the initial stage because it completely avoided the drug‐squeezing effect, and the release was a zero‐order pattern. © 1995 John Wiley & Sons, Inc.