bluuebunny/crossref_metadata_2025_split huggingface dataset:
Implantation study of a novel hydroxyapatite/collagen (HAp/col) composite into weight‐bearing sites of dogs
Authors: Itoh Soichiro , Kikuchi Masanori , Takakuda Kazuo , Nagaoka Katsuyoshi , Koyama Yoshihisa , Tanaka Junzo , Shinomiya Kenichi 
Published: September 2002

AbstractA hydroxyapatite/type I collagen (HAp/Col) composite, aligning hydroxyapatite nanocrystals along collagen molecules, has been prepared. The biocompatibility, osteoconductive activity, and efficacy as a carrier of rhBMP‐2 of this novel biomaterial implanted in the weight‐bearing site have been examined. The HAp/Col implants (15 mm in diameter and 20 mm in length) with a surface cross‐linked layer containing rhBMP‐2 (0 or 400 μg/ml) were implanted into bone defects of tibiae in three beagle dogs and fixed according to the Ilizarov method. As a control, bone defects of 20 mm in two beagle dogs did not receive implants, and the dogs were allowed to walk using an Ilizarov extraskeletal fixator. The specimens were removed from one dog in each group after 12 weeks. Also, the Ilizarov fixators in the rhBMP‐treated dogs were removed after 12 weeks, after which full weight bearing started. The specimens were further taken out after 18 and 24 weeks in the rhBMP‐treated and non‐rhBMP‐treated dogs, and after 24 weeks in the control group. The change of bone mineral density, as well as radiological and histological findings, suggest that the implants are able to induce bone remodeling units and are a superior carrier of rhBMP‐2 due to the stimulation of early callus and new bone formation. © 2002 Wiley Periodicals, Inc. J Biomed Mater Res (Appl Biomater) 63: 507–515, 2002
Characteristics and porcelain bond strength of (Ti,Al)N coating on dental alloys
Authors: Chung Kwok‐Hung , Duh Jeng‐Gong , Shin Daehwan , Cagna David R. , Cronin Robert J. 
Published: September 2002

AbstractThe effect of a novel titanium–aluminum nitride film, or (Ti,Al)N film, on the bond strength between a dental porcelain and two nickel‐based dental alloy substrates was investigated. A thin layer of (Ti,Al)N film was deposited on flat metal samples using a reactive radio‐frequency sputtering method. A uniform thickness of porcelain was applied to the film‐ coated metal samples. Metal–ceramic specimens were subjected to three‐point bending, and failure loads were recorded. Bond strengths between the porcelain and (Ti,Al)N‐coated metal alloys ranged from 159.0 ± 11.7 N to 278.0 ± 12.3 N. These values were significantly greater (p< 0.05) than bond strengths recorded for control samples that did not incorporate the (Ti,Al)N film. An electron probe microanalyzer with a line profile mode was used to characterize the interface between the (Ti,Al)N film and the porcelain. Results of this investigation suggest that the (Ti,Al)N film (1) increases the flexural bond strength between dental porcelain and nickel‐based alloy substrates by permitting elemental diffusion, (2) interferes with the surface oxide formation that characteristically originates from the nickel‐based metal alloy substrate, and (3) provides an appropriate oxide layer for porcelain application. © 2002 Wiley Periodicals, Inc. J Biomed Mater Res (Appl Biomater) 63: 516–521, 2002
Calcium phosphate/chitosan composite scaffolds for controlled in vitro antibiotic drug release
Authors: Zhang Yong , Zhang Miqin 
Published: September 2002

AbstractMacroporous chitosan scaffolds reinforced by β‐tricalcium phosphate (β‐TCP) and calcium phosphate invert glasses were fabricated using a thermally induced phase separation technique. These porous composite materials were specially designed as both a drug carrier for controlled drug release and a scaffold for bone regeneration. The controlled drug release of antibiotic gentamicin‐sulfate (GS) loaded scaffolds and morphology of osteosarcoma MG63 cells cultured on the scaffolds were studied. In comparison with the GS loaded pure chitosan scaffolds, the initial burst release of GS was decreased through incorporating calcium phosphate crystals and glasses into the scaffolds, and the sustained release for more than 3 weeks was achieved. The possible mechanisms for the controlled drug release were investigated by SEM, FTIR, and measurements of the pH values of the PBS solution during the drug release test. SEM micrographs showed no apparent morphological differences for osteoblastic cells grown on the pure chitosan scaffolds and those grown on composite scaffolds. The cells were attached and migrated on these scaffolds, and exhibited a biological appearance, suggesting a good cellular compatibility. © 2002 Wiley Periodicals, Inc. J Biomed Mater Res 62: 378–386, 2002
Characterization of implant materials in fetal bovine serum and sodium sulfate by electrochemical impedance spectroscopy. I. Mechanically polished samples
Authors: Contu F. , Elsener B. , Böhni H. 
Published: September 2002

AbstractElectrochemical impedance spectroscopy is used to monitor the long‐term stability (up to 150 days) of mechanically polished commercial pure titanium, Ti6Al4V, Ti6Al7Nb, and CoCrMo alloys in 0.1M sodium sulfate and fetal bovine serum. A capacitive spectrum in the frequency range from 10−3 to 105 Hz is always found and the impedance spectra can be fitted by a simple parallel RC circuit with a constant phase element. The open circuit potential observed in serum is always more cathodic and the polarization resistance (Rp) is higher than that recorded in sodium sulfate solutions. The observed variation of the equivalent capacitance in serum bovine suggests that an adsorption layer of organic molecules develops on the electrode surface and it is responsible for both the decrease in open circuit potential and the higher Rp, because it hinders the oxygen evolution reaction and the charge transfer responsible for the passive film dissolution (or growth). Among the alloys studied, Ti6Al4V displayed the highest steady‐state values of Rp both in serum and in sodium sulfate. © 2002 Wiley Periodicals, Inc. J Biomed Mater Res 62: 412–421, 2002
Human monocyte response to retrieved polymethylmethacrylate particles
Authors: Miyaguchi Masatsugu , Kobayashi Akio , Iwaki Hiroyoshi , Ohashi Hirotsugu , Kadoya Yoshinori , Yamano Yoshiki 
Published: September 2002

AbstractThe purpose of this study was to compare retrieved polymethylmethacrylate (PMMA) particles from failed total hip arthroplasties in terms of size, shape, and the response of human monocytes with commercially available particles. PMMA particles were isolated from peri‐implant tissues of five failed cemented total hip arthroplasties using tissue digestion and a sucrose density gradient technique. Prepolymerized cement powder and those from which barium sulfate had been removed were examined for comparison. After exposure of peripheral human monocytes to PMMA particles, tumor necrosis factor‐α and interleukin‐6 in medium were measured by using enzyme‐linked immunosorbent assays. Image analysis revealed that retrieved particles were larger (retrieved: 1.24 μm; prepolymerized cement powder: 0.83 μm; barium sulfate‐free powder: 0.87 μm) and were more irregular in shape and rougher than commercially available particles. Cytokine release was increased by all PMMA particle species. However, commercially available PMMA particles stimulated the release of necrosis factor‐α and interleukin‐6 more strongly than did retrieved particles at very high doses. The observed difference in monocyte response might be due to the volume of the challenged particles. Another possible reason for the difference might be alteration of the surface chemistry of particles in situ and the difference in surface morphology between them. © 2002 Wiley Periodicals, Inc. J Biomed Mater Res 62: 331–337, 2002
Gamma irradiation alters fatigue‐crack behavior and fracture toughness in 1900H and GUR 1050 UHMWPE
Authors: Cole Jantzen C. , Lemons Jack E. , Eberhardt Alan W. 
Published: September 2002

AbstractPitting and delamination remain causative factors of polyethylene failure in total knee replacement. Gamma irradiation induces cross linking in ultra‐high‐molecular‐weight polyethylene, which has been shown to improve wear resistance. Irradiation may reduce fracture toughness and fatigue strength, however, and the effects of irradiation are dependent upon the resin, processing technique, and radiation dose. The effects of varying levels of gamma irradiation (0, 33, 66, and 100 kGy) on the fracture toughness and fatigue‐crack resistance of UHMWPE, isostatically molded from 1900H and GUR 1050 resins, were examined. Paris law regressions were performed to quantify fatigue‐crack propagation rates as functions of change in stress intensity, and J‐integral methods were used to quantify the elastic–plastic fracture toughness. The results indicated that gamma irradiation reduced the resistance of both materials to fatigue‐crack growth, and that the reductions were radiation dosage and resin dependent. Irradiation at any level was detrimental to the fracture toughness of the 1900H specimens. Irradiation at 33 kGy increased fracture toughness for the GUR 1050 specimens, and substantial reductions were observed only at the highest irradiation level. Scanning electron microscopy of the fracture surface revealed diamond‐like fracture patterns of the nonirradiated specimens indicative of ductile, multilevel fracture. Pronounced striations were apparent on these fracture surfaces, oriented perpendicular to the direction of crack growth. The striations appeared as folds in surface layers of the GUR 1050 specimens. At the highest irradiation levels, the striations were nearly eliminated on the fracture surfaces of the 1900H specimens, and were markedly less severe for the GUR 1050. These results demonstrated that at higher irradiation levels the materials became more brittle in fatigue, with less ductile folding and tearing of the fracture surfaces. © 2002 Wiley Periodicals, Inc. J Biomed Mater Res (Appl Biomater) 63: 559–566, 2002
The peak‐amplitude method of vibration analysis for nondestructively studying the structural integrity of dental gypsum
Authors: Prombonas Anthony E. , Paralika Maria A. , Sotiriou Michael P. , Vlissidis Dimitris S. 
Published: September 2002

AbstractThe aim of this work was to estimate the internal friction of dental gypsum products by measuring their loss factor with the use of the peak‐amplitude method of vibration analysis. Cylindrical specimens for the measurement of compressive strength and rectangular specimens for the measurement of loss factor were constructed from plaster, dental stone, and high‐strength dental stone. The loss factor was measured by vibrating specimens up to their resonance frequency, where the peak‐amplitude method was applied. It was found that the peak‐amplitude method is a simple, quick, and reliable method for measuring the loss factor of dental gypsum products. Furthermore, it was also found that the drying process of these materials reduces their internal friction and hence lowers the loss factor, whereas the use of excess water in their formulation has the reverse result. The correlation between strength and loss factor was found to be strongly negative. The results of this study are in agreement with the results from research on the microstructure of dental gypsum. © 2002 Wiley Periodicals, Inc. J Biomed Mater Res (Appl Biomater) 63: 605–609, 2002
The electrochemical behavior of Ti‐6Al‐7Nb alloy with and without plasma‐sprayed hydroxyapatite coating in Hank's solution
Authors: Lavos‐Valereto I. C. , Costa I. , Wolynec S. 
Published: September 2002

AbstractThe electrochemical behavior of Ti‐6Al‐7Nb alloy with and without plasma‐sprayed hydroxyapatite (HA) coating was investigated in Hank's balanced salt solution at 37 °C. This behavior was evaluated by analyzing both corrosion potential variation with time curves and potentiodynamic polarization curves. The polarization curves were determined both in aerated and deaerated solutions. It was found that the corrosion potential of uncoated sample is always more noble than that of coated one. In aerated solutions the polarization curve of a coating‐free alloy presents a typical passive/transpassive behavior, which is absent in the HA‐coated alloy and in deaerated solution for both coated and uncoated conditions. In the latter polarization curves, the current density continuously increases with the increase of the potential. The corrosion rate determined from polarization curves is higher for HA‐coated alloys, but it still can be considered negligible (less than 1 μA/cm2). © 2002 Wiley Periodicals, Inc. J Biomed Mater Res (Appl Biomater) 63: 664–670, 2002
Adhesive phase separation at the dentin interface under wet bonding conditions
Authors: Spencer Paulette , Wang Yong 
Published: September 2002

AbstractUnder in vivo conditions, there is little control over the amount of water left on the tooth and, thus, there is the danger of leaving the dentin surface so wet that the bonding resin undergoes physical separation into hydrophobic and hydrophilic‐rich phases. The purpose of this study was to investigate phase separation in 2,2‐bis[4(2‐hydroxy‐3‐methacryloyloxy‐propyloxy)‐phenyl] propane (BisGMA)‐based adhesive using molecular microanalysis and to examine the effect of phase separation on the structural characteristics of the hybrid layer. Model BisGMA/HEMA (hydroxyethl methacrylate) mixtures with/without ethanol and commercial BisGMA‐based adhesive (Single Bond) were combined with water at concentrations from 0 to 50 vol%. Macrophase separation in the BisGMA/HEMA/water mixtures was detected using cloud point measurements. In parallel with these measurements, the BisGMA/HEMA and adhesive/water mixtures were cast as films and polymerized. Molecular structure was recorded from the distinct features in the phase‐separated adhesive using confocal Raman microspectroscopy (CRM). Human dentin specimens treated with Single Bond were analyzed with scanning electron microscopy (SEM) and CRM mapping across the dentin/adhesive interface. The model BisGMA/HEMA mixtures with ethanol and the commercial BisGMA‐based adhesive experienced phase separation at ∼25 vol% water. Raman spectra collected from the phase‐separated adhesive indicated that the composition of the particles and surrounding matrix material was primarily BisGMA and HEMA, respectively. Based on SEM analysis, there was substantial porosity at the adhesive interface with dentin. Micro‐Raman spectral analysis of the dentin/adhesive interface indicates that the contribution from the BisGMA component decreases by nearly 50% within the first micrometer. The morphologic results in corroboration with the spectroscopic data suggest that as a result of adhesive phase separation the hybrid layer is not an impervious 3‐dimensional collagen/polymer network but a porous web characterized by hydrophobic BisGMA‐rich particles distributed in a hydrophilic HEMA‐rich matrix. © 2002 Wiley Periodicals, Inc. J Biomed Mater Res 62: 447–456, 2002
Histological examination of β‐tricalcium phosphate graft in human femur
Authors: Ogose Akira , Hotta Tetsuo , Hatano Hiroshi , Kawashima Hiroyuki , Tokunaga Kunihiko , Endo Naoto , Umezu Hajime 
Published: September 2002

AbstractProminent osteoconductive activity and the biodegradable nature of beta tricalcium phosphate (β‐TCP) for bone grafts in animal experiments has been reported. A new type of β‐TCP has been manufactured at extraordinarily high purity and has been available as potent bone grafting substitute for clinical use. The histological features of grafted β‐TCP in human bone have been analyzed. A 33‐year‐old female with a bone tumor of the proximal femur underwent curettage and β‐TCP graft under the diagnosis of probable benign fibrous dysplasia. Four weeks later, the proximal femur, including the grafted β‐TCP was resected because of the final diagnosis of the curettaged materials was osteosarcoma. The resected specimen revealed abundant direct new bone apposition on β‐TCP. There was no cartilaginous tissue or enchondral ossification. Bone formation was more prominent in the periphery of the grafted area than in the center. There was a considerable number of osteoclast‐like giant cells surrounding the β‐TCP. This case illustrated that highly purified β‐TCP had prominent osteoconductive activity and biodegradable nature in human bone. © 2002 Wiley Periodicals, Inc. J Biomed Mater Res (Appl Biomater) 63: 601–604, 2002
Chitosan‐alginate PEC membrane as a wound dressing: Assessment of incisional wound healing
Authors: Wang Lishan , Khor Eugene , Wee Aileen , Lim Lee Yong 
Published: September 2002

AbstractFlexible, thin, transparent, novel chitosan‐alginate polyelectrolyte complex (PEC) membranes, cast from aqueous suspensions of chitosan‐alginate coacervates with CaCl2, were evaluated as potential wound‐dressing materials. MTT and NR assays suggested that the chitosan‐alginate PEC membranes and their aqueous extracts were nontoxic towards mouse and human fibroblast cells. Cell growth was also not hindered by co‐incubation with the membranes. Compared to conventional gauze dressing, the PEC membranes caused an accelerated healing of incision wounds in a rat model. Wounds closed at 14 days postoperatively, and histological observations showed mature epidermal architecture with keratinized surface of normal thickness and a subsided inflammation in the dermis. This was followed by an excellent remodeling phase with organized thicker collagen bundles and mature fibroblasts at 21 days postoperative. Control wounds continued to show signs of an active inflammatory phase under scab on Day 21. Closure rate and appearance of PEC membrane‐treated wounds were comparable with Opsite®‐treated wounds. On the basis of its biocompatibility and wound‐healing efficacy, the chitosan‐alginate PEC membrane can be considered for wound‐dressing applications. © 2002 Wiley Periodicals, Inc. J Biomed Mater Res (Appl Biomater) 63: 610–618, 2002
Cytotoxicity of ingredients of various dental materials and related compounds in L2‐ and A549 cells
Authors: Walther U. I. , Walther S. C. , Liebl B. , Reichl F. X. , Kehe K. , Nilius M. , Hickel R. 
Published: September 2002

AbstractVarious ingredients of dental materials and related compounds were tested for cytotoxicity in two alveolar epithelial cell lines (L2 and A549 cells). Release of lactate dehydrogenase (LDH) from cells was measured after incubation with the test substances for time intervals up to 48 h and expressed as percentage of total LDH content of lysed cells. Furthermore, the glutathione content of cells was determined in the nonmalignant L2 cells. Additionally, cell viability was assessed by microscopic examination. The highest cytotoxicity was observed with mercury compounds (methylmercuric chloride and mercury dichloride) in the range of 5–20 μmol/l. The composite components 2‐hydroxyethylmethacrylate (HEMA) and triethleneglycoldimethacrylate (TEGDMA) showed time‐ and concentration‐dependent effects of cytotoxicity at high concentrations (about 1–5 mmol/l). A time dependence for GSH decrease was mainly found for the composite components up to 12 h of cellular exposure. L2 cells were more sensitive to both mercury and composite compounds than A549 cells. Gold compounds (sodiumaurothiomalate and gold particles < 1.5 μm) did not produce any sign of toxic reactions. A time‐dependent increased toxicity in pulmonary cell lines was found for the composite components HEMA and TEGDMA, but not for mercury and gold compounds. © 2002 Wiley Periodicals, Inc. J Biomed Mater Res (Appl Biomater) 63: 643–649, 2002
The influence of system compliance and sample geometry on composite polymerization shrinkage stress
Authors: Laughlin Gayle A. , Williams John L. , Eick J. David 
Published: September 2002

AbstractThe objective of this study was to use finite‐element analysis to model tensilometer tests of polymerizing dental composites. A typical sample in polymerization shrinkage stress tests is shaped like a flat disk, that is, has a high aspect ratio (ratio of diameter to height). In the experimental literature it is implied that the induced stress state in the flat disk composite samples is uniaxial. Three published tensilometer tests of curing dental composite samples with similar high aspect ratios (varying from 3 to 5) were modeled, but with test configurations having low, intermediate and high relative compliance (a tenfold variation). With the use of linear elastic finite element analysis, an instantaneous volumetric shrinkage of 1% was applied to the composite via the thermal analogy and the following questions were addressed:

Does the numerically predicted state of stress in composite samples tested in this fashion differ substantially from the uniaxial stress state assumed in the experiments?
How do the numerically predicted stresses compare with the experimentally determined nominal stresses?
Does compliance of the mountings influence the numerically predicted stress state?

The finite‐element results predicted a complex triaxial stress state that was strongly influenced by the compliance of the mountings. For the low and intermediate system compliance the model overpredicted the polymerization contraction stress, as would be anticipated due to the inability of the model to account for viscoplastic flow. For high system compliance, the numerical and experimental stress values were in better agreement, mainly because the linear elastic mountings accounted for most of the measured system compliance. © 2002 Wiley Periodicals, Inc. J Biomed Mater Res (Appl Biomater) 63: 671–678, 2002
Morphological changes induced by extracellular matrix are correlated with maturation of rat small hepatocytes
Authors: Sugimoto Shinichi , Mitaka Toshihiro , Ikeda Shinichiro , Harada Keisuke , Ikai Iwao , Yamaoka Yoshio , Mochizuki Yohichi 
Published: September 2002

AbstractSmall hepatocytes (SHs), which are known to be hepatic progenitor cells, were isolated from an adult rat liver. SHs in a colony sometimes change their shape from small to large and from flat to rising/piled‐up. The aim of the present study is to clarify whether the alteration of cell shape is correlated with the maturation of SHs and whether extracellular matrix (ECM) can induce the morphological changes of SHs. We used liver‐enriched transcription factors (LETFs) such as hepatocyte nuclear factor (HNF) 4α, HNF6, CCAAT/enhancer binding proteins (C/EBP) α, and C/EBPβ, tryptophan 2,3‐dioxygenase (TO), and serine dehydratase (SDH) as markers of hepatic maturation. To enrich the number of SH colonies, the colonies were isolated from dishes and replated. Replated colonies proliferated and the average number of cells per colony was about five times larger at day 9 than at day 1. When the cells were treated with laminin, type IV collagen, a mixture of laminin and type IV collagen, Matrigel™ or collagen gel (CG), only the cells treated with Matrigel dramatically changed their shape within several days and had reduced growth activity, whereas the cells treated with other ECM did not. HNF4α, HNF6, C/EBPα, C/EBPβ, and TO were well expressed in the cells treated with Matrigel. Furthermore, addition of both glucagon and dexamethasone dramatically induced the expression of SDH mRNA and protein in the cells treated with Matrigel. In conclusion, morphological changes of SHs may be correlated with hepatic maturation and basement membrane (BM)‐like structure may induce the morphological changes of SHs. J. Cell. Biochem. 87: 16–28, 2002. © 2002 Wiley‐Liss, Inc.