bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effect of the tooth microstructure on the shear bond strength of a dental composite
Authors: Panighi M. , G'Sell C. 
Published: May 2005

AbstractPlane 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

AbstractTwo 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

AbstractThis 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

AbstractTo 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

AbstractParticulate 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

AbstractHylan, 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

AbstractThe 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

AbstractThe 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

AbstractA 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

AbstractStudies 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

AbstractParticulate 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

AbstractAs 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

AbstractCell‐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

AbstractElectrochemical 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.