bluuebunny/crossref_metadata_2025 huggingface dataset:
Neocartilage after artificial cartilage repair in the rabbit: Histology and proteoglycan fragments in joint fluid
Authors: Messner Karola , Lohmander L. Stefan , Gillquist Jan
Published: May 2005

Repair of full‐thickness cartilage defects of the rabbit medial femoral condyle with artificial plugs and periosteal grafts was followed for 1 year. The morphological characteristics of the neocartilage after repair and the concentration of proteoglycan fragments in the joint fluid (CPFF) were evaluated. The CPFF showed only a weak correlation to the histological score of the neocartilage. Normal cartilage and subchondral bone did not develop with any of the repair alternatives. With a Dacron plug, neocartilage formation appeared earlier than with natural repair and was better than with periosteal grafting. Increased CPFFs were found in all specimens with repair at 3 months, probably reflecting the remaining effect of surgery. At 6 months, the CPFFs were again similar to those at the 3‐month evaluation. This was paralleled by a degeneration of the neocartilage. We conclude that Dacron plugs could serve as a scaffold for neocartilage formation. The CPFF reflected surgical trauma and late degeneration of neocartilage but did not indicate minor differences in quality between cartilage repair techniques, probably because of the limited size of the grafted defect. © 1993 John Wiley & Sons, Inc.
Kinetics of cell proliferation as a function of vascular graft material
Authors: Greisler Howard P. , Petsikas Dimitri , Lam Tina M. , Patel Narendra , Ellinger Joan , Cabusao Emma , Tattersall Charles W. , Kim Dae Un
Published: May 2005

Bioresorbable vascular grafts constructed for polyglactin 910 (PG910) and polydioxanone (PDS) and nonresorbable Dacron were interposed into the infrarenal abdominal aortas of New Zealand White rabbits. The prosthesis/tissue complexes were harvested after 2, 3, 4, 12, and 52 weeks. Seventeen, 9, and 1 h prior to sacrifice, animals received tritiated thymidine (0.5 mCi/kg/dose). All specimens were studied grossly and by light and transmission electron microscopy. Mitotic indices (MI's) were determined by autoradiography for inner capsule myofibroblasts at the proximal, mid, and distal segments of each prosthesis. There were no aortic‐related deaths. All grafts were patent with no aneurysmal dilatiation. At 4 weeks, PG910 resorption was evidenced by macrophage phagocytosis, less so in PDS while Dacron remained intact. At 12 weeks, the PG910 was completely resorbed while PDS resorption continued. The latter was completely resorbed by 52 weeks. There was no significant difference in MI's between proximal, mid, and distal regions for each graft type. The mitotic index paralleled the rate of prosthetic resorption in both PG910 and PDS groups, as high as 28.34 ± 23.21 in the former 3 weeks after implantation and significantly higher at 4 weeks (7.58 ± 2.02 and 7.50 ± 2.66, respectively) than at 52 weeks (0.72 ± 0.98 and 1.00 ± 0.22, respectively) in both groups. The mitotic index in the Dacron group never surpassed 1.22 ± 0.90.

We conclude that higher levels of early cell proliferation in bioresorbable grafts closely parallel the kinetics of prosthetic resorption. © 1993 John Wiley & Sons, Inc.
Effect of the tooth microstructure on the shear bond strength of a dental composite
Authors: Panighi M. , G'Sell C.
Published: May 2005

Plane human enamel and dentin surfaces were used for microstructural investigation and shear bond testing. The dental tissue microstructure was characterized through the surface topology, the concentration in mineral elements (determined by electron microprobe analysis), and the Vickers microhardness for the same dental tissue. The etched prismatic enamel presents a surface roughness of about 200% of the apparent area, while the intertubular surface fraction of the dentin is, on the average, equal to 75%. The calcium concentration lies between 23.2 and 37.8% of the enamel total mineral content, and 18.5 and 28.2% of the dentin. The microhardness varies from 205 to 378 Hv for the enamel and from 37 to 98 Hv for the dentin. Also, the shear bond strength to a chemosetting adhesive/composite system varies from 10.4 to 23.9 MPa for the enamel and from 0.0 to 5.0 MPa for the dentin. It is shown that the shear bond strength is strongly correlated to the microhardness through a simple linear equation valid for both enamel and dentin surfaces. In turn, the microhardness is correlated to the calcium concentrartion through two distinct linear relations. These correlations lead to the intrinsic dependence of the shear bond strength on the calcium concentration of the dental tissue, providing that corrections are applied to the bond strength data in order to take into consideration the effective solid area of the adherend and the polymerization retraction stress. Consequently, it is proposed that the adhesion mechanisms for the both enamel and the dentin are controlled, to a major extent, by the mineral content and the surface topology of the tooth. © 1993 John Wiley & Sons, Inc.
Mechanisms and structure of the bond between bone and hydroxyapatite ceramics
Authors: Bagambisa Frank B. , Joos Ulrich , Schilli Wilfried
Published: May 2005

Two assays were carried out to investigate the postulates that dissolution/reprecipitation phenomena and epitaxis are involved in the formation of the bond between sintered hydroxyapatite (HA) and bone. HA was exposed to a physiologic solution and the ions going into solution quantified using inductively coupled plasma (ICP) emission spectroscopy. The HA was retrieved and examined using scanning electron microscopy (SEM). In the second assay, HA was implanted into Alsatian femura. Following retrieval, specimens were prepared and studied with SEM, at magnifications usually reserved for transmission electron microscopy (TEM). In vitro the HA surface composition appeared to shift to the acidic (calcium‐deficient) direction. The HA surfaces in both assays underwent a dissolution/reprecipitation degradation of varying severity, forming a recrystallization layer of spherocrystallites. Two modes of bone bonding to implanted HA were identified: (1) bone tissue components bonded to HA via a recrystallization zone similar in structure to the reprecipitation layer in the corrosion assay, and (2) bone tissue components bonded directly to HA crystals with no morphologically discernible signs of dissolution embarrassment. The formation of the bone/HA bond seems to involve dissolution/reprecipitation phenomena. What is believed to be the first morphological evidence of epitaxial growth involvement in the formation of this bond is presented. © 1993 John Wiley & Sons, Inc.
Quantification of in vivo endothelial cell adhesion to vascular graft material
Authors: Wigod Mark D. , Klitzman Bruce
Published: May 2005

This study tests the hypothesis that denucleating vascular graft material and binding cell adhesion molecules increases endothelial attachment. Removal of gas nuclei (denucleation) increases the availabel surface area of biomaterials for modification and/or cell adhesion, while adhesion molecules provide specific attachment sites. Microvascular endothelial cells (MVEC) were isolated from fat, fluorescently labeled, and allowed to settle onto expaned polytetrafluoroethylene (ePTFE) vascular patches. Patch treatments included fibronectin alone (F), gas denucleation followed by fibronectin (D/F), denucleation followed by the surfactant tridodecylmethlammonium chloride (TDMAC) D/T), denucleation followed by TDMAC followed by fibronectin (D/T/F), or denucleation follwed by TDMAc followed by a synthetic polymer with numerous arginine‐glycine‐aspertic acid sequences (D/T/R). After 1 h of incubation, the 45 mm2 patch area covered with microvascular endothelial cells was assessed using comuter‐aided fluorescence microscopy. Initial graft coverage with D/T (26.2 ± 2.4mm2) and D/T/F (25.9 ± 2.1 mm2) was better than with f (16.8 ± 2.5 mm2) (P < .05). Patches were then exposed to a detachment stress and coverage was again measured. Following stress, coverage was greater with D/T (20.7 ± 3.4 mm2) and D/T/F (20.7 ± 2.0 mm2) than with D/T/R (8.4 ± 1.8 mm2) or F (3.6 ± 0.9 mm2 (P < .001). Percent retention of cells following stress was better with D/T and D/T/F than with D/T/R, D/F, or F (P < .0001). Scanning electron micrographs were consistent with the qualitative findings. The results indicate that IDMAC alone or with fibronectin increases adhesion of human microvascular endothelial cells to denucleated ePTFE. © 1993 John Wiley & Sons, Inc.
In vivo biostability and calcification‐resistance of surface‐modified PU‐PEO‐SO3
Authors: Han Dong Keun , Park Ki Dong , Jeong Seo Young , Kim Young Ha , Kim Un Young , Min Byoung Goo
Published: May 2005

To examine the biostability and calcification‐resistance of polyurethanes (PUs), the surface of PU was grafted with hydrophobic perfluorodecanoic acid (PFDA) (PU‐PFDA), hydrophilic polyethyleneoxide (PEO) (PU‐PEO1000), and further negatively charged sulfonate groups (PU‐PEO1000‐SO3). An in vivo animal test was conducted by subcutaneous implantation in rats during 2, 4 and 6 months. A scanning electron microscope study demonstrated that the degree of surface cracking on explanted PUs was increased in the following order: PU‐PFDA > PU > PU‐PEO1000 > PU‐PEO1000‐SO3. In the results of energy dispersive x‐ray analysis and inductively coupled plasma atomic emission spectrometry, the deposition of calcium was found abundantly, but that of phosphorus was hardly in existence in all implanted PUs, suggesting that this calcium compound is not a hydroxyapatite. The calcium contents, regardless of implantation time, were also increased in the same order (PU‐PFDA > PU > PU‐PEO1000 > PU‐PEO1000‐SO3). After 6 months implantation, no severe tissue reactions were observed and calcification almost occurred on polymer surfaces in all implants. Such superior biostability and anticalcification of PU‐PEO1000‐SO3 might be attributed to synergistic effects of its excellent surface smoothness, sulfonate acid (SO3−) groups, nonadhesive and mobile PEO, and the high hydrophilicity and enhanced blood compatibility. Therefore, PU‐PEO1000‐SO3 is promising as biostable and calcification‐resistant biomaterial. © 1993 John Wiley & Sons, Inc.
Effects of Na2HPO4 and NaH2PO4 on hydroxyapatite formation
Authors: Fulmer Mark T. , Brown Paul W.
Published: May 2005

Particulate solids CaHPO4 (DCP) and Ca4 (PO4)2O (TetCP) can react to form hydroxyapatite (HAp) under conditions which may be compatible with those in vivo. Effects of sodium phosphate solutions on the formation of calcium deficient HAp at 25°C by this reaction in dilute suspensions (liquid‐to‐solids ratio of 100) and at l/s = 1 were studied. An l/s ratio of one is not greatly different from that at which monolithic HAp forms. Solution chemistry results showed that the sodium phosphate used and its concentration strongly influenced the kinetics of HAp formation and the HAp composition. HAp formation occurred by the same mechanism in water and in the Na2HPO4 solutions investigated; however; HAp formation occurred more rapidly in Na2HPO4 solutions. DCP dissolution was congruent in these solutions and this delayed the overgrowth of DCP by HAp. Reaction in NaH2PO4 solutions resulted in the formation of CaHPO4 · 2H2O as an intermediate product. The final product formed in the NaH2PO4 solutions was affected by the l/s ratio used. CaHPO4 · 2H2O, not HAp, was the product formed from dilute suspension but it was not observed during reaction at l/s = 1.

Variations in solution were correlated with the formation of HAp and intermediate products, with the consumption of reactants, and with the heat evolution characteristics. The latter were determined by isothermal calorimetry. Calorimetric analysis of the reactions indicated increased heat evolution in sodium phosphate solutions and acceleration in HAp formation. This appears to be related to accelerated dissolution of CaHPO4, which was rate limiting. © 1993 John Wiley & Sons, Inc.
Hylan gel biomaterial: Dermal and immunologic compatibility
Authors: Larsen Nancy E. , Pollak Cynthia T. , Reiner Karen , Leshchiner Edward , Balazs Endre A.
Published: May 2005

Hylan, a hyaluronan derivative, was chemically crosslinked with divinyl sulfone to produce a water‐insoluble gel. This gel was fragmented into a gel slurry and evaluated for particle size, biocompatibility, and residence times in selected tissues. Hylan gels used in this study are made up of pseudoplastic, deformable gel particles with greater elasticity (at all frequencies) and greater viscosity (shear rates, 0.01 sec−1) than the water soluble hylan polymer.

Hylan gel was injected intradermally and subdermally in mice and was found to produce a minimal reaction at 24 h; thereafter (up to 7 weeks) there was no significant tissue reaction. Intradermal injection of [3H]‐hylan gel in guinea pigs revealed a minimal tissue reaction after 1 week, and measurement of radioactivity in the tissue at 1, 2, and 4 weeks revealed only a slight decrease in the total amount of injected radioactivity. The immunogenic activity of hylan gel was evaluated in rabbits; unmodified hylan gel, degraded hylan gel, and hylan gel ovalbumin conjugate were used to immunize rabbits. No antibody production to any hylan gel sample was detected, although control rabbits immunized with ovalbumin developed titers >400 of antiovalbumin antibodies by day 21, as measured by the passive cutaneous anaphylaxis assay (PCA). Last, serum from owl monkeys (Aotus trivirgatus) in which hylan gel had been placed intravitreally for up to 3 years contained no detectable anti‐hylan gel antibodies (PCA assay). Skin tests on these monkeys were also negative. © 1993 John Wiley & Sons, Inc.
Tissue response and in vivo degradation of selected polyhydroxyacids: Polylactides (PLA), poly(3‐hydroxybutyrate) (PHB), and poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) (PHB/VA)
Authors: Gogolewski S. , Jovanovic M. , Perren S. M. , Dillon J. G. , Hughes M. K.
Published: May 2005

The tissue response and in vivo molecular stability of injection‐molded polyhydroxyacids—polylactides (PLA), poly(3‐hydroxybutyrate) (PHB), and poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) (PHB/VA, 5–22% VA content)—were studied. Polymers were implanted subcutaneously in mice and extirpated at 1, 3, and 6 month in order to study tissue response and polymer degradation.

All polymers were well tolerated by the tissue. No acute inflammation, abscess formation, or tissue necrosis was observed in tissues adjacent to the implanted materials. Furthermore, no tissue reactivity or cellular mobilization was evident remote from the implant site. Mononuclear macrophages, proliferating fibroblasts, and mature vascularized fibrous capsules were typical of the tissue response. Degradation of the polymers was accompanied by an increase in collagen deposition. For the polylactide series, the inflammatory response after 1 month of implantation was less for materials containing the D‐unit in the polymer chain, whereas in the case of the polyhydroxybutyrate/valerates, the number of inflammatory cells increased with increasing content of the valerate unit in the polymer chain. Between 1–3 months, there was slightly more tissue response to the PHB and PHB/VA polymers than to PLA. This response is attributed to the presence of leachable impurities and a low molecular weight soluble component in the polyhydroxybutyrate/valerates. At 6 months, the extent of tissue reaction was similar for both types of polymers.

All polylactides degraded significantly (56–99%) by 6 months. For a poly(L‐lactide) series, degradation rate in vivo decreased with increasing initial molecular weight of the injection‐molded polymer. Several samples showed pronounced bimodal molecular weight distributions (MWD), which may be due to differences in degradation rate, resulting from variability in distribution of crystalline and amorphous regions within the samples. This may also be the result of two different mechanisms, i.e., nonenzymatic and enzymatic, which are involved in the degradation process, the latter being more extensive at the later stage of partially hydrolyzed polymer. The PHB and PHB/VA polymers degraded less (15–43%) than the polylactides following 6 months of implantation. Generally, the polymer with higher valerate content (19%, 22% degraded most. The decrease in molecular weight was accompanied by a narrowing of the MWD for PHB and copolymers; there was no evidence of a bimodal MWD, possibly indicating that the critical molecular weight that would permit enzyme/polymer interaction had not been reached. Weight loss during implantation ranged from 0–50% for the polylactides, whereas for the PHB polymers weight loss ranged from 0–1.6%. © 1993 John Wiley & Sons, Inc.
Bioactive glass promoted formation of nodules in periodontal‐ligament fibroblasts in vitro
Authors: Kubo Kohji , Kakimoto Takashi , Kanda Chieko , Tsukasa Nobuyuki , Uehara Mayumi , Izumi Yuichi , Kamada Tetsuro , Kaneko Norio , Sueda Takeshi
Published: May 2005

The effects of bioactive glass and vitamin D3 on cultured fibroblasts derived from periodontal‐ligament, with respect to their proliferation and alkaline‐phosphatase activity were studied. The cells were cultured with or without the bioactive glass and/or vitamin D3, then the number and alkaline‐sphosphatase activity of the cells were measured periodically until the 33rd day. Formation of mineralized deposits was assessed by staining with alizarin red and von Kossa staining techniques. Fewer fibroblasts grew when they were cultured in the presence of bioactive glass and/or vitamin D3 as compared to those cultures without them. Alkaline‐phosphatase activity was greater in the fibroblasts cultured with bioactive glass and vitamin D3 than in the cells grown without them. Mineralized deposits assessed by alizarin red and von Kossa staining techniques were observed microscopically around the fibroblasts cultured with bioactive glass and/or vitamin D3. A nodule visible after drying was evident only when both bioactive glass and vitamin D3 were present in culture. The results showed that although the bioactive glass and vitamin D3 decreased cell proliferation, they increased the alkaline‐phosphatase activity of the fibroblasts which formed a nodule, suggesting an effect which might be useful for implant materials. © 1993 John Wiley & Sons, Inc.
In vitro platelet interactions in whole human blood exposed to biomaterial surfaces: Insights on blood compatibility
Authors: Haycox Claire L. , Ratner Buddy D.
Published: May 2005

A short‐term in vitro test to study platelet interactions with biomaterials is described. Using fresh human blood and a modified Chandler loop system, β‐thromboglobulin release was measured. Also, adherent platelets were observed by using scanning electron microscopy (SEM) and a colorimetric stain specific for human platelet GPIIIa. Materials studied in these experiments were polyethylene (PE), Biomer, poly(vinyl alcohol) (PVA), and a polyurethane prepared with octadecyl pendant groups (ODCE). Four blood reactions were observed: (1) Platelets continually adhere and activate on the Biomer; (2) platelets initially adhere and activate but then spread to a thin, passivating film on the PE; (3) platelets do not adhere to the PVA surface but continually react with it upon contact; and (4) platelets neither adhere to nor activate on the ODCE surface. Reactions (2) and (4) are considered characteristic of blood‐compatible materials. © 1993 John Wiley & Sons, Inc.
Functional versus quantitative comparison of IL‐1β from monocytes/macrophages on biomedical polymers
Authors: Bonfield T. L. , Anderson J. M.
Published: May 2005

Studies utilizing a quantitative assay, radioimmunossay, and a biological activity assay, the murine thymocyte proliferation assay, to analyze IL‐1β cytokine production by monocytes/macrophages on biomedical polymers have been carried out. Results indicate that the quantitative analysis of IL‐1β on biomedical polymers and protein‐adsorbed biomedical polymers is not indicative of and does not correlate with the results of the biological activity assay. IL‐1β secreted from human monocytes/macrophages on Biomer, polydimethylsiloxane (PDMS), Dacron, polyethylene, expanded polytetrafluoroethylene, and control polystyrene with and without the preadsorption of physiological concentrations of human IgG, fibrinogen, and/or fibronectin was assayed. Quantitative levels of IL‐1β suggest a greater functional response than that observed in the biological thymocyte proliferation assay when the polymers were studied directly or preadsorbed with IgG. On the other hand, preadsorption with fibrinogen or fibronectin resulted in high functional activity for IL‐1β with low quantitative levels of IL‐1β. The lack of correlation between the functional and biological activity assays suggests the presence of other cytokines or antagonists which modulate the biological activity of IL‐1β. © 1993 John Wiley & Sons, Inc.
Macrophage/particle interactions: Effect of size, composition and surface area
Authors: Shanbhag Arun S. , Jacobs Joshua J. , Black Jonathan , Galante Jorge O. , Glant Tibor T.
Published: May 2005

Particulate wear‐debris are detected in histiocytes/macrophages of granulomatous tissues adjacent to loose joint prostheses. Such cell‐particle interactions have been simulated in vitro by challenging macrophages with particles dosed according to weight percent, volume percent, and number of particles. Each of these dosage methods has inherent shortcomings due to varying size and density of challenging particles of different compositions. In this study we challenged P388D1 macrophages with titania and polystyrene particles (> 2 μm), with dosage based on the ratio of the surface area of the particles to the surface area of the cells. The effect of size and composition on (1) the bone resorbing activity, (2) fibroblast proliferation, and (3) secretion of IL‐1 and PGE2 was determined.

Macrophage response to particulate debris appears to be dependent on particle size, composition, and dose as given by surface area ratio. P388D1 macrophages challenged with titania particles released IL‐1, but did not stimulate fibroblasts. Inhibition of macrophage DNA synthesis at higher surface area ratios suggests cell damage or death. Particle‐stimulated cells increased bone resorption up to 125% of controls but released only basal levels of PGE2.

Macrophages stimulated by wear particles are expected to synthesize numerous factors affecting events in the bone‐implant interface. Using the concept of surface area ratio allows us to study and compare such cellular responses to wear particles in a standardized manner. © 1994 John Wiley & Sons, Inc.
Human amnion collagen for soft tissue augmentation—biochemical characterizations and animal observations
Authors: Spira Melvin , Liu Bingci , Xu Zenglu , Harrell Randall , Chahadeh Hassen
Published: May 2005

As bovine collagen is currently being scrutinized as to its immunogenicity in clinical use, a human source collagen, human amnion collagen (HAC), has been developed in our laboratory as an injectable biomaterial for soft tissue augmentation. Pepsin‐extracted human amnion collagen was highly purified and reconstituted. Gamma irradiation was employed to ensure complete sterility and to produce cross‐linking in collagen chains to improve implant persistence without the use of chemical additives. The purity and characteristics of human amnion collagen were proven by amino acid assay, sodium dodecyl sulfate‐polyacrylamide gel electrophoresis, immune blotting, and collagenase digestion. Animal studies comparing both irradiated and nonirradiated amnion collagen to bovine collagen (Zyderm® and Zyplast®) were carried out in a rat model. Humoral immunity was evaluated by examining the sera for antibody reactivity towards the implanted human collagen by the ELISA test. Insignificant antibody levels against human amnion collagen were found. Animal observation revealed fibroplasia, vascular infiltration, and the development of adipocytes with the implant as well as a lack of inflammatory response following up to 12 months of implantation. The persistence rate of our human amnion collagen was equal to, or even longer than, that of both types of bovine collagen implants. © 1994 John Wiley & Sons, Inc.
Osteoclastic resorption of calcium phosphates is potentiated in postosteogenic culture conditions
Authors: de Bruijn J. D. , Bovell Y. P. , Davies J. E. , van Blitterswijk C. A.
Published: May 2005

Cell‐mediated resorption of densely sintered hydroxyapatite (HA1250), tricalcium phosphate (TCP), and 600° or 900°C calcined hydroxyapatite (HA600 and HA900, respectively), was investigated by using two culture systems. The first was an osteoclastic cell culture, and the second was a two‐stage culture that was composed of a bonelike tissue formation on the substrata in the first stage and its subsequent resorption by osteoclasts in the second stage. Neither of the materials showed resorption or surface alterations in the osteoclastic cell culture, except for some limited phagocytotic activity on HA600 and HA900. In the two‐stage culture, production of mineralized extracellular matrix was only observed on HA1250 and TCP, and its subsequent resorption by osteoclastlike cells was evident. Small and occasionally larger tartrate‐resistant acid phosphatase positive cells produced 20–150 μm diameter resorption pits in both the mineralized extracellular matrix on HA1250 and TCP and TCP and the surfaces of HA600 and HA900. Resorption of the mineralized extracellular matrix on TCP also resulted in degradation of the underlying ceramic surface, mainly initiating from intergrain boundaries, whereas the surface of HA1250 remained unaltered. The results of this study clearly demonstrate that osteoclastic resorption of calcium phosphates is potentiated in postosteogenic culture conditions. A possible role for bone matrix constituents in cell‐mediated resorption is hypothesized, whereas the occurrence of resorption seems to be mainly governed by the combined effects of material characteristics such as grain size and crystal structure. © 1994 John Wiley & Sons, Inc.
Electrochemical and XPS studies of titanium for biomaterial applications with respect to the effect of hydrogen peroxide
Authors: Pan J. , Thierry D. , Leygraf C.
Published: May 2005

Electrochemical measurements, x‐ray photoelectron spectroscopy, and scanning tunneling microscopy have been used to study the effect of hydrogen peroxide on the passivity of titanium in a phosphate‐buffered saline (PBS) solution. The results indicate that the passive film formed in the PBS solution—with and without addition of H2O2—may be described with a twolayer structure model. The inner layer has a structure close to TiO2 whereas the outer layer consists of hydroxylated compounds. The introduction of H2O2 in the PBS solution broadens the hydroxylate‐rich region, probably due to the formation of a Ti(IV)‐H2O2 complex. Furthermore, the presence of H2O2 results in enhanced dissolution of titanium and a rougher surface on a microscopic scale. Finally, a dark pigmentation (blue color) is observed when titanium has been exposed—for several weeks—to PBS with additions of H2O2. © 1994 John Wiley & Sons, Inc.
Interface reactions to PEO/PBT copolymers (polyactive®)after implantation in cortical bone
Authors: Radder A. M. , Leenders H. , van Blitterswijk C. A.
Published: May 2005

The bone reaction at the interface of a range of PEO/PBT copolymers (Polyactive®) after press‐fit implantation in the diaphyseal femur of 20 goats was investigated. The animals were sacrificed at 1, 4, 12, 26, and 52 weeks. Undecalcified histologic sections were prepared, evaluated qualitatively, and quantified with the aid of an image analysis system. The percentage of bone contact was determined morphometrically for all PEO/PBT proportions; for the 70/30 ratio, the percentage of calcification of the material surface and of bonebonding (defined as a continuum at the light microscopic level between calcification within the material surface and bone tissue) were also assessed.

PEO/PBT copolymers possess hydrogelic properties, and a direct relation has been established between water‐uptake and PEO content. The swelling behavior of all PEO/PBT substrates resulted in a high degree of bone contact (over 95%) at early stages. From the 12‐week survival time onward the 70/30 revealed higher percentages of bone contact (over 80%) when compared with the other ratios (60/40, 55/45, 40/60, and 30/70). This difference was statistically confirmed 1 year postoperatively. The materials with the higher PEO contents showed the highest amounts of calcification, which is reflected by the rate of bone‐bonding were not observed for 40/60 and 30/70 proportions.

The quantitative results confirmed the relation between PEO content, water‐uptake, calcification, and bone‐bonding. It was furthermore demonstrated that PEO/PBT copolymers initially establish a high degree of bone contact, whereas the bone‐bonding properties, especially of the 70/30, accomplish a long‐term implant fixation. © 1994 John Wiley & Sons, Inc.
Application of flow cytometry to determine the cytotoxicity of urethane dimethacrylate in human cells
Authors: Nassiri M. Reza , Hanks Carl T. , Cameron Mark J. , Strawn Susan E. , Craig Robert G.
Published: May 2005

The effects of an oligomer, urethane dimethacrylate (UDMA), on two human cell lines were studied using flow cytometry (FCM). Untreated and treated cultures of propidium iodine‐stained KB (epidermal oral carcinoma cells) and human foreskin fibroblas (HFF) cells were analyzed for cellular DNA content. Concentrations of 10 and 25 μM of UDMA slightly perturbed the KB cell cycle progression at 24 and 48 h of incubation. However, the effect of 50 μ M was more pronounced at the latter incubation time period. In cell growth experiments, the sublethal concentrations (10 and 25 μM) produced inhibition of KB cell growth rate at a moderate level, which resulted in the prolongation of cell population doubling time. Significant inhibition of cell growth occurred when 50 μM (lethal concentration) was used. Data obtained from the cell cycle perturbation analysis, evidenced by FCM, correlated with the extent of inhibition in KB cell growth rates. The effects of sublethal concentrations were reversible during a 24 h period of oligomer withdrawal from culture medium. In contrast, the effects of 50 μM were not reversible. In HFF cells the depletion of S phase in the cell cycle was the major effect of 50 μM of UDMA. It was concluded that FCM technology is an ideal and practical approach for studying the cytotoxicity of components of dental composites. © 1994 John Wiley & Sons, Inc.
Use of diphenylphosphorylazide for cross‐linking collagen‐based biomaterials
Authors: Petite H. , Frei V. , Huc A. , Herbage D.
Published: May 2005

Cross‐linking of collagen‐based biomaterials increases their strength and persistence in vivo. Recently, we described an efficient cross‐linking process via the formation of acyl azide groups on methylated carboxyl groups of collagen using hydrazine and nitrous acid (referred to here as the hydrazine method). In this report, we propose a simpler, faster way to prepare acyl azide groups and to cross‐link collagen‐based biomaterials, using diphenylphosphorylazide (DPPA) as a reagent. After determining the optimal conditions of cross‐linking with DPPA, we compared the efficiency of this protocol with that using hydrazine and with the classical glutaraldehyde treatment. In order to validate and quantitate the extent of reaction, the degree of crosslinking was determined by the measure of the free primary amino group content of the samples.

Treatment of native bovine pericardium with 0.5% DPPA for 24 h led to efficient cross‐linking, corresponding to a 50% decrease in the free primary amino group content of the sample and raising its thermal stability from 62.8 up to 81.3°C. In comparison, the thermal stabilities of glutaraldehydeor hydrazine‐treated pericardium were 85 ± 0.4°C and 83.4 ± 0.1°C. Similar decreases in free primary amino group content and increases in thermal stability were obtained for collagen films treated with DPPA, glutaraldehyde, or hydrazine. These results were corroborated by resistance to bacterial collagenase digestion: DPPA‐treated pericardium had a resistance to collagenase digestion similar to that of glutaraldehyde‐ or hydrazine‐treated pericardium. Residual DPPA content: the concentration of phosphorus in tissue treated with 0.5% DPPA was not significantly different from that of untreated tissue. Treatment by DPPA thus appears to be an efficient, rapid method for cross‐linking collagenbased biomaterials. © 1994 John Wiley & Sons, Inc.
Elutions of metal ions from dental casting alloys and their effect on calcium phosphate precipitation and transformation
Authors: Hidaka S. , Okamoto Y. , Abe K.
Published: May 2005

The elution characteristics of metal ions from dental casting alloys were studied in vitro. Large amounts of nickel (0.12–4.94 mg/cm2) and chromium (<0.01–0.63 mg/cm2) were solubilized from the surface of seven brands of nickel‐chromium alloy in either 1% lactic acid or 0.05% hydrochloric acid solutions. The elution of chromium from two brands of cobalt‐chromium alloys in both eluents was below the detection limit or less than 0.01 mg/cm2. The elution of tin, copper, and zinc from a gold‐palladium‐silver alloy in both eluents was below the detection limit or less than 0.01 and 0.04 mg/cm2. Some amounts of tin (0.19–1.92 mg/cm2) and zinc (0.56–1.73 mg/cm2) were eluted from a silver alloy in both eluents.

The effects of five eluting metal ions, i.e., nickel, chromium, tin, copper, and zinc, on the conversion of amorphous calcium phosphate (ACP) to hydroxyapatite (HAP) in vitro also were studied by a pH drop method. All divalent cations except for chromium decreased the rate of HAP transformation and elongated the induction time. Nickel had an inhibitory effect comparable to 1‐hydroxyethylidene‐1, 1‐bisphosphonate (HEBP) on the rate of HAP transformation. Tin, copper, and zinc inhibited similarly, but the inhibition was weaker than that by nickel. Chromium did not inhibit these reactions. © 1994 John Wiley & Sons, Inc.
Blood compatibility of sputter‐deposited alumina films
Authors: Yuhta Toshio , Kikuta Yukiaki , Mitamura Yoshiniori , Nakagane Kenichi , Murabayashi Shun , Nishimura Ikuya
Published: May 2005

The surface modification of metals by the application of blood compatible ceramics is one approach to developing durable and blood‐compatible materials. The blood compatibility of sputter‐deposited alumina films was investigated in vitro. The alumina films were prepared by reactive sputtering and conventional sputtering. Diffractometer studies of the alumina films indicate that the sputter‐deposited alumina films have amorphous structures. Electron spectroscopy chemical analysis studies of the alumina films indicate that the sputter‐deposited alumina films are nonstoichiometric (O/Al ratio of 1.15–1.66).

We examined the platelet reaction to the alumina films and the intrinsic coagulation factor XII activation by the alumina films. Medical grade segmented polyurethane was also tested. The alumina films experienced an adhesion of about 50% fewer platelets than the segmented polyurethane. Also, fewer platelet morphologic changes were observed on the alumina films than on the segmented polyurethan. Factor XII activation was less on the alumina films than on the segmented polyurethane. Surface modification by the sputter‐deposited alumina films is promising for developing blood‐compatible and durable materials. © 1994 John Wiley & Sons, Inc.
Hemocompatibility on graft copolymers composed of poly(2‐methacryloyloxyethyl phosphorylcholine) side chain and poly(n‐butyl methacrylate) backbone
Authors: Ishihara Kazuhiko , Tsuji Tsuyoshi , Kurosaki Toshikazu , Nakabayashi Nobuo
Published: May 2005

To improve the hemocompatibility on hydrophobic biomedical materials by a simple coating technique, graft copolymers composed of a hydrophilic side chain with phospholipid polar groups and a hydrophobic backbone were synthesized. The hydrophilic chain had phospholipid polar groups, poly[2‐methacryloyloxyethl phosphorylcholine (MPC)], and the hydrophobic backbone was poly[n‐butyl methacrylate (BMA)]. Because the graft copolymers obtained could dissolve in ethanol, they could be used as a coating material. When the poly(MPC‐graft‐BMA) membrane, the composition of the MPC units on the surface was maintained in the bulk graft copolymer even after immersion in water. Protein adsorption on the membrane coated with the graft copolymer from human plasma detected by a gold‐colloid labeled immunoassay was drastically decreased compared with that on glass and the original membrane. Moreover, blood cell adhesion, activation, and aggregation on the membrane after contact with human citrated whole blood were suppressed by the coating of the graft copolymer. These results clearly show that the poly(MPC‐graft‐BMA) is a suitable material for improving hemocompatibility on the biomedical devices because of its protein adsorption and cell adhesion resistant properties. © 1994 John Wiley & Sons, Inc.
Development of a pericardial acellular matrix biomaterial: Biochemical and mechanical effects of cell extraction
Authors: Courtman David W. , Pereira Christopher A. , Kashef Villa , McComb Donna , Lee J. Michael , Wilson Gregory J.
Published: May 2005

There is evidence to suggest that the cellular components of homografts and bioprosthetic xenografts may contribute to calcification or immunogenic reactions. A fourstep detergent and enzymatic extraction process has been developed to remove cellular components from bovine pericardial tissue. The process results in an acellular matrix material consisting primarily of elastin, insoluble collagen, and tightly bound glycosaminoglycans. Light and electron microscopy confirmed that nearly all cellular constituents are removed without ultrastructural evidence of damage to fibrous components. Collagen denaturation temperatures remained unaltered. Biochemical analysis confirmed the retention of collagen and elastin and some differential extraction of glycosaminoglycans. Low strain rate fracture testing and high strain rate viscoelastic characterization showed that, with the exception of slightly increased stress relaxation, the mechanical properties of the fresh tissue were preserved in the pericardial acellular matrix. Crosslinking of the material in glutaraldehyde or poly(glycidyl ether) produced mechanical changes consistent with the same treatments of fresh tissue. The pericardial acellular matrix is a promising approach to the production of biomaterials for heart valve or cardiovascular patching applications. © 1994 John Wiley & Sons, Inc.
Protein adsorption on low‐temperature isotropic carbon: I. Protein conformational change probed by differential scanning calorimetry
Authors: Feng L. , Andrade J. D.
Published: May 2005

This is the first of a set of articles on protein adsorption on low‐temperature isotropic carbon (LTIC), a reputed blood compatible material. Surface‐induced conformational changes of albumin, fibrinogen, and some small proteins were measured by differential scanning calorimetry (DSC) on LTIC powders and colloidal silica. The LTIC surface significantly alters the DSC response (denaturation?) in proteins studied in different buffer solutions. We use the term „denaturation”︁ to refer to altered protein behavior in the adsorbed state. Hydrophobic interactions between LTIC and the proteins are thought to be the major driving force. The presence of air at the water‐carbon interface seems to prevent the surface denaturation of fibrinogen. The silica surface greatly denatures albumin but only slightly denatures fibrinogen. Because LTIC is considered to be a nonthrombogenic material, but silica is considered to be a thrombogenic one, whether a surface denatures adsorbed proteins cannot be the sole criterion for its blood compatibility. The latter largely depends on what protein the surface denatures, and in what sequences. © 1994 John Wiley & Sons, Inc.
Fibroblast growth on polymer surfaces and biosynthesis of collagen
Authors: Tamada Yasushi , Ikada Yoshito
Published: May 2005

The growth and morphology of rat fibroblasts cultured on various polymer substrates, as well as their collagen biosynthesis, were studied. A clear difference in cell growth and cell morphology was observed among the substrates. The dependence of cell growth on the water contact angle of substrate was similar to that of the adhesion. Fibroblasts could proliferate at the highest rate and showed the highest‐ordered morphology when cultured on the substrate with a contact angle around 70°, which was also the most favorable for cell adhesion. The amount of collagen synthesized by total cells and of adsorption of the synthesized collagen to substrates were in good correlation with the cell growth dependence on the contact angle of substrate, whereas the collagen synthesis per cell was more active on the surfaces poor for cell growth than on the good ones. Cells on surfaces promoting active collagen synthesis had a round shape and clustered upon each other. The collagenimmobilized surface had nearly the highest cell adhesion, high cell proliferation, and high collagen adsorption among the substrates studied. In addition, the highest‐ordered morphology and no lag time for proliferation were observed for the collagen‐immobilized surface. These results indicate that the collagen‐immobilized substrate provides the most favorable surface for cell growth at the initial stage. © 1994 John Wiley & Sons, Inc.
Fracture toughness of single crystal alumina in air and a simulated body environment
Authors: Mitamura Yoshinori , Wang Youfu
Published: May 2005

The critical intensity factor KIC of a single crystal alumina (1100)‐plane in air and in a simulated body environment was measured. Based on these measurements, the estimated durability of a single crystal alumina disk in a ceramic heart valve was determined. Standard single‐edge notched beam specimens were prepared. The specimens were classified into three groups: (a) stored in air (n = 10), (b) immersed in Ringer's solution for 2 months (n = 11), and (c) immersed in Ringer' solution for 4 months (n = 6). KIC was 2.345 ± 0.072 MPam½ for specimens stored in air, 2.141 ± 0.147 in Ringer's solution for 2 months, and 2.005 ± 0.153 in Ringer's solution for 4 months. The KIC decreased for specimens stored in Ringer's solution (P < .01), but it did not differ significantly between 2 and 4 months. The decrease of KIC is the stress corrosion effect of Ringer's solution at the crack tip, and is not associated with an over all deterioration of strength. The stress intensity factor for possible cracks (length: 0.4 mm) in the single crystal alumina was calculated. Maximum stress was assumed 2.668 MPa ( = 40 × 500 mm Hg). The stress intensity factor calculated was far less than the KIC. The single crystal alumina disk can endure a static pressure of 500 mm Hg. © 1994 John Wiley & Sons, Inc.
The acoustic properties of normal and imbedded bovine bone as measured by acoustic microscopy
Authors: Zimmerman Mark C. , Prabhakar Avinash , Chokshi Biren V. , Budhwani Navin , Berndt Hubert
Published: May 2005

The acoustic impedance of bovine femoral cortical bone was measured with a scanning acoustic microscope used in the reflection mode. The bone was measured in the unimbeded state and after plastic imbedding. The acoustic impedance of the unimbedded specimens was also measured with a standard transmission ultrasonic technique. For the unimbedded bovine specimens there was a good correlation between the bulk transmission impedance and the reflection surface impedance (r2 = 0.976) and the values were 9.32 and 9.29 MRayls, respectively. Plastic imbedding produced a consistent and statistically significant increase in the acoustic impedance of the bone (9.71 MRayls). This experiment verified the use of acoustic microscopy as a quantitative materials analysis technique and it demonstrated the potential for material property analysis of imbedded bone. © 1994 John Wiley & Sons, Inc.
Effects of variation of prosthesis size on cement stress at the tip of a femoral implant
Authors: Lee I. Y. , Skinner H. B. , Keyak J. H.
Published: May 2005

With the resurgence of the use of bone cement in total hip arthroplasty, a renewed interest in techniques or designs that may reduce cement fixation failure has arisen. Analysis of the stresses at the tip of the prosthesis may suggest strategies to reduce loosening. This study analyzed stresses in the cement near the tip of a femoral component as a function of cement thickness, using a three‐dimensional finite element model. A section of an idealized circular femoral shaft with implanted prosthesis and cement was modeled with loading conditions representing the stance phase of gait. Increasing cement thickness from 2 to 5 mm by reducing the prosthesis diameter from 15 to 9 mm is predicted to reduce stress significantly in the cement mantle of a femoral implant. Peak tensile stresses are reduced 45%, whereas peak von Mises and shear stresses are reduced 40%. Such a reduction in stress can increase fatigue life by an order of magnitude. Peak interface tensile stresses occur on the medial side at the tip of the prosthesis in a transverse direction, indicating likelihood of failure due to debonding. The shear and tensile stresses predicted by our model greatly exceed the fatigue endurance limit values for both bulk cement and the cement‐prosthesis interface, indicating the likelihood of premature fatigue failure, even allowing for considerable uncertainty. These analytical results suggest that the surgeon should adopt a strategy of selecting a prosthesis that permits a 5‐mm cement mantle near the tip of the prosthesis. © 1994 John Wiley & Sons, Inc.
Antithrombogenicity of lumbrokinase‐immobilized polyurethane
Authors: Ryu Gyu Ha , Park Seonyang , Kim Miran , Han Dong Keun , Kim Young Ha , Min Byounggoo
Published: May 2005

Lumbrokinase is a potent fibrinolytic enzyme purified from the earthworm, Lumbricus rubellus. We immobilized 18 IU/cm2 of lumbrokinase to polyurethane using maleic anhydride methylvinyl ether copolymer (MAMEC) as an enzyme carrier, and the proteolytic and fibrinolytic activities of immobilized lumbrokinase were assayed. Immobilized lumbrokinase retained about 34% of its activity, compared with soluble lumbrokinase activity. Immobilized lumbrokinase showed stability against thermal inactivation and degradation and within a various pH range. The optimal pH of immobilized lumbrokinase shifted 1.0 pH unit upward compared with soluble enzyme. Upon exposure to the human whole blood, less amount of 125I‐fibrinogen was adsorbed to lumbrokinase‐immobilized surface than to the polyurethane control surface. The lumbrokinase‐immobilized surface showed less platelet adhesion than did the MAMEC‐grafted surface. At the early stage of platelet adhesion, the number of adhered platelets increased on the lumbrokinase‐immobilized surface with increasing time; yet, the platelet number drastically decreased on the lumbrokinase‐immobilized surface after 80 min incubation. This suggests that lumbrokinase‐immobilized polyurethane digested the adsorbed fibrinogen and inhibited platelet adhesion on the surface, probably by inhibiting fibrinogen adsorption to be highly antithrombogenic. Clinical applications of this material to artificial organs should be developed in the near future. © 1994 John Wiley & Sons, Inc.