bluuebunny/crossref_metadata_2025_split huggingface dataset:
The effects of tubule orientation on fatigue crack growth in dentin
Authors: Arola Dwayne D. , Rouland Joseph A. 
Published: September 2003

AbstractThe fracture of restored teeth is a significant obstacle to lifelong oral health. Recent studies suggest that fatigue cracks originate at flaws introduced during cavity preparation and that fatigue crack growth is a principle cause of restored tooth fractures. In this study, the rate of fatigue crack growth in bovine dentin was estimated under mode I cyclic loading. Double cantilever beam (DCB) specimens were obtained from bovine molars and subjected to high cycle fatigue loading (105 < N < 106). The fatigue crack growth rates were measured and used to estimate the crack growth exponent and coefficient according to the Paris Law. The average fatigue crack growth exponent was 4.7 ± 0.6 for crack growth parallel to the dentin tubules, which was significantly larger than 4.3 ± 0.5 for crack growth perpendicular to the tubules (t‐test, CI > 80%). Although the crack growth rates varied considerably, there was no significant dependence on tubule orientation or tubule density. However, specific features of the fracture surfaces and tendencies for crack curving away from the tubules suggested preferential fatigue crack growth perpendicular to the dentin tubules. Results from this study are being used to guide an experimental investigation of fatigue crack growth in human dentin. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res 67A: 78–86, 2003
Protein adsorption on mixtures of hydroxyl‐ and methyl‐terminated alkanethiols self‐assembled monolayers
Authors: Martins Ma Cristina L. , Ratner Buddy D. , Barbosa Mário A. 
Published: September 2003

AbstractThe effect of surface composition and wettability on the adsorption of human serum albumin (HSA) was studied. Self‐assembled monolayers (SAMs) containing mixtures of longer chain methyl‐ and shorter chain hydroxyl‐terminated alkanethiols on gold were used to produce a range of surfaces with different wettabilities and exposed functional groups. Different SAMs were characterized by X‐ray photoelectron spectroscopy, water contact angles, and Fourier transform infrared reflection absorption spectroscopy (IRAS). HSA adsorption onto the different SAMs was evaluated by contact angle measurements (wetting tension determinations), radiolabeling of proteins, and IRAS. Concerning HSA adsorption, all the techniques demonstrated higher HSA adsorption on more hydrophobic surfaces. The wetting tension measurements and IRAS suggested a gradual decrease of the HSA adsorption with increases of surface hydrophilicity. Radiolabeled albumin measurements also demonstrated a significant decrease of HSA adsorption on the pure hydroxyl‐terminated SAMs. However, no significant differences were detected between mixed and pure methyl‐terminated SAMs. Studies of HSA exchangeability with human fibrinogen have suggested that an ideal percentage of hydroxyl groups on the surface may increase albumin affinity without fibrinogen adsorption. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res 67A: 158–171, 2003
Hg2+ and Ni2+ alter induction of heat shock protein‐72 in THP‐1 human monocytes
Authors: Noda M. , Wataha J. C. , Lewis J. B. , Lockwood P. E. , Komatsu H. , Sano H. 
Published: September 2003

AbstractThe biological liabilities that result from the release of metal ions from biomedical alloys, particularly Ni2+ and Hg2+, continue to be a concern. Heat‐shock proteins (HSP) are a class of molecular chaperones that may be induced under conditions of cellular stress, including oxidative stress. Our hypothesis was that because Hg2+ and Ni2+ alter other cellular stress responses such as glutathione levels and cytokine secretion, these metal ions may alter HSP induction in monocytes, which are key cells in the response of tissues to biomedical alloys. THP‐1 monocytes were exposed to sublethal concentrations of Hg2+ or Ni2+ for 1 h with or without heat stress (43°C), then allowed to recover at 37°C for 2–6 h. HSP72 was measured using immunoblotting with phosphorimage quantification. Hg2+ exposures of 2–10 μmol/L induced HSP72 without heat stress. With heat stress, HSP72 levels were altered by Hg2+ versus heat stress alone. The response depended on the concentration of Hg2+ and the recovery time. Hg2+ at 10 μmol/L caused uniformly lower HSP72 levels. Ni2+ exposures of 20–100 μmol/L did not induce HSP72 without heat stress, but significantly altered heat‐induced HSP72 expression, with a significant increase in expression over heat alone at 40 and 100 μmol/L. Results from the current study support the hypothesis that these metal ions can, at concentrations relevant to those released from biomedical alloys, modulate HSP expression in human monocytes. The modulation of HSP expression indicates an early sign of cellular stress that may be important to the overall biological response to biomedical alloys containing and releasing these metal ions. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res 67A: 240–245, 2003
In vivo biocompatibility of three different chemical compositions of Ricinus communis polyurethane
Authors: Barros Valdemar M. R. , Rosa Adalberto L. , Beloti Márcio M. , Chierice Gilberto 
Published: September 2003

AbstractAlteration in the chemical composition of a biomaterial may be undertaken to improve its biological properties. The aim of this work was to evaluate the biocompatibility of three chemical compositions of Ricinus communis polyurethane (RCP): RCPp (pure RCP), RCP + CaCO3, and RCP +Ca3(PO4)2. RCP cylinders were surgically implanted in rabbit femurs. After 8, 12, and 16 weeks, the femurs were removed, fixed, sectioned, ground, and stained by Stevenel's blue/Alizarin red S for light microscopy and histomorphometry. The osseointegration and osseoconductivity were calculated by means of image analysis and the data were submitted to the Kruskal‐Wallis test followed by Dunn's test. Osseointegration was already completed after 8 weeks on RCP + Ca3(PO4)2 because similar values were found from week 8 to 16, whereas it showed a time‐dependent increase on RCPp and RCP +CaCO3. The osseointegration was greater on RCP + Ca3(PO4)2 in all periods when compared with RCPp, and after 8 and 12 weeks when compared with RCP + CaCO3. None of the RCP samples presented osseoconductivity. The present results showed that RCP blended with calcium phosphate improved the biocompatibility by both enhancing and accelerating its osseointegration. Based on the absence of osseoconductivity, RCP was considered to be a bioinert material. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res 67A: 235–239, 2003
Synthesis and physicochemical analysis of interpenetrating networks containing modified gelatin and poly(ethylene glycol) diacrylate
Authors: Burmania Jeanine A. , Martinez‐Diaz Gabriel J. , John Kao Weiyuan 
Published: September 2003

AbstractThe interrelated effects of gelatin modification, content, and poly(ethylene glycol) molecular weight on the melting temperature, surface hydrophilicity, tensile properties, swelling/degradation, and drug‐release kinetics of a novel interpenetrating network (IPN) system containing gelatin and poly(ethylene glycol) diacrylate were evaluated. Gelatin content had a large effect on the IPN melting temperature and ΔH. Modifying gelatin with ethylenediaminetetraacetic acid and/or monomethoxy poly(ethylene glycol) monoacetate ester as well as increasing poly(ethylene glycol) diacrylate molecular weight increased the surface hydrophilicity. Increasing the gelatin weight percent increased the IPN elasticity at room temperature. When buffer and elevated temperature were present in the testing environment, the elasticity of all IPNs tested decreased. IPNs showed an enhanced elasticity and strength when compared with glutaraldehyde‐fixed gelatin hydrogels. The extent of IPN swelling and degradation was increased by increasing the gelatin content or by modifying gelatin. The time to complete sample degradation was longer for IPNs when compared with gelatin crosslinked with glutaraldehyde. Modifications to the IPN system increased the maximum percent of chlorhexidine digluconate released from the IPNs. The rate of complete drug release was slower from IPNs than from glutaraldehyde‐fixed gelatin matrices. A wide range of IPN physicochemical properties was obtained through formulation changes and chemical modifications. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res 67A: 224–234, 2003
Val‐ala‐pro‐gly, an elastin‐derived non‐integrin ligand: Smooth muscle cell adhesion and specificity
Authors: Gobin Andrea S. , West Jennifer L. 
Published: September 2003

AbstractThe elastin‐derived peptide val‐ala‐pro‐gly (VAPG) may be useful as a biospecific cell adhesion ligand for smooth muscle cells. By grafting the peptide sequence into a hydrogel material, we were able to assess its effects on smooth muscle cell adhesion and spreading. These materials are photopolymerizable hydrogels based on acrylate‐terminated derivatives of polyethylene glycol (PEG). Because of their high PEG content, these materials are highly resistant to protein adsorption and cell adhesion. However, PEG diacrylate derivatives can be mixed with adhesive peptide‐modified PEG monoacrylate derivatives to facilitate cell adhesion. Following photopolymerization, PEG monoacrylate derivatives are grafted into the hydrogel network formed by the PEG diacrylate. This results in covalent immobilization of adhesive peptides to the hydrogel via a flexible linker chain. The resistance of PEG to protein adsorption makes it an ideal material for this model system since cell–material interactions are limited to biomolecules that are covalently incorporated into the material. In this case we were able to demonstrate that VAPG is specific for adhesion of smooth muscle cells. It also was shown that fibroblasts, endothelial cells, and platelets cannot adhere to VAPG. In addition, not only was smooth muscle cell adhesion dependent on ligand concentration, but also cell spreading increased with increasing ligand concentration. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res 67A: 255–259, 2003
Tissue engineered bone: Measurement of nutrient transport in three‐dimensional matrices
Authors: Botchwey Edward A. , Dupree Melissa A. , Pollack Solomon R. , Levine Elliot M. , Laurencin Cato T. 
Published: September 2003

AbstractThe classic paradigm for in vitro tissue engineering of bone involves the isolation and culture of donor osteoblasts or osteoprogenitor cells within three‐dimensional (3D) scaffold biomaterials under conditions that support tissue growth and mineralized osteoid formation. Our studies focus on the development and utilization of new dynamic culture technologies to provide adequate nutrient flux within 3D scaffolds to support ongoing tissue formation. In this study, we have developed a basic one‐dimensional (1D) model to characterize the efficiency of passive nutrient diffusion and transport flux to bone cells within 3D scaffolds under static and dynamic culture conditions. Internal fluid perfusion within modeled scaffolds increased rapidly with increasing pore volume and pore diameter to a maximum of approximately 1% of external fluid flow. In contrast, internal perfusion decreased significantly with increasing pore channel tortuosity. Calculations of associated nutrient flux indicate that static 3D culture and some inappropriately designed dynamic culture environments lead to regions of insufficient nutrient concentration to maintain cell viability, and can result in steep nutrient concentration gradients within the modeled constructs. These quantitative studies provide a basis for development of new dynamic culture methodologies to overcome the limitations of passive nutrient diffusion in 3D cell‐scaffold composite systems proposed for in vitro tissue engineering of bone. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res 67A: 357–367, 2003
Characterization of implant materials in fetal bovine serum and sodium sulfate by electrochemical impedance spectroscopy. II. Coarsely sandblasted samples
Authors: Contu F. , Elsener B. , Böhni H. 
Published: September 2003

AbstractElectrochemical impedance spectroscopy is used to investigate the corrosion resistance of coarsely sandblasted implant alloys, commercially pure titanium, Ti6Al4V, Ti6Al7Nb, and CoCrMo in 0.1M sodium sulfate and fetal bovine serum. Coarsely sandblasted samples have a heterogeneous surface constituted by a large number of protrusions and recessions. Impedance spectra collected in sodium sulfate present two time constants (maxima in the phase‐angle of the bode plot) associated with the total surface and with the tips, respectively. In bovine serum, the two maxima in the impedance spectra cannot be distinguished because of the formation of an adsorption layer of organic molecules, which causes a decrease in the values of both the total and tips' capacitances as well as an increase in the polarization resistance. Ti6Al4V and Ti6Al7Nb show the highest corrosion rate both in serum and in sodium sulfate. Based on the capacitance values obtained in sodium sulfate, the real surface area of the coarsely sandblasted electrodes has been estimated relative to mechanically polished surfaces. The values of the effective electrode area correlate with the mechanical properties of the samples: in fact, the softest electrode (commercially pure titanium) shows the largest effective electrode area, whereas the hardest material (CoCrMo alloy) shows the smallest surface area. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res 67A: 246–254, 2003
Patterning hydroxyapatite biocoating by electrophoretic deposition
Authors: Wang R. , Hu Y. X. 
Published: September 2003

AbstractPatterned bioceramic coatings may find potential applications in orthopedic implants and biosensors. In this study, various hydroxyapatite (HA) patterns were created on silicon and titanium substrates. Electrophoretic deposition technique was used together with surface patterning of the cathode specimen. When gold/palladium patterns (hexagons, spherical dots, etc.) were created on the cathode surface, HA colloidal particles in ethanol would preferentially deposit on the gold‐coated area and form patterns. When silicon, instead of gold, was evaporated onto a conducting cathode surface, HA mainly deposited on the exposed area of the substrate. Detailed mechanisms for forming HA patterns may involve local concentration of the electric field when a second metal is patterned on the cathode. The difference in electric field across the two metals on the cathode also enhances HA patterning through an electrohydrodynamic process. This study demonstrated the possibility and flexibility of electrophoretic deposition in patterning charged particles onto a substrate. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res 67A: 270–275, 2003
A centrifugation cell adhesion assay for high‐throughput screening of biomaterial surfaces
Authors: Reyes Catherine D. , García Andrés J. 
Published: September 2003

AbstractA quantitative analysis of cell adhesion is essential in understanding physiological phenomena and designing biomaterials, implant surfaces, and tissue‐engineering scaffolds. The most common cell adhesion assays used to evaluate biomaterial surfaces lack sensitivity and reproducibility and/or require specialized equipment and skill‐intensive operation. We describe a modified centrifugation cell adhesion assay that uses simple and convenient techniques with standard laboratory equipment and provides reliable, quantitative measurements of cell adhesion. This centrifugation assay applies controlled and uniform detachment forces to a large population of adherent cells, providing robust statistics for quantifying cell adhesion. The applicability of this system to the design and characterization of biomaterial surfaces is shown by evaluating cell adhesion on substrates using different coating proteins, cell types, seeding times, and relative centrifugal forces (RCF). Results verify that this centrifugation cell adhesion assay represents a simple, convenient, and standard method for high‐throughput characterization of a variety of biomaterial surfaces and conditions. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res 67A: 328–333, 2003
Defect initiation at subsurface grain boundary as a precursor of delamination in ultrahigh molecular weight polyethylene
Authors: Shibata Nobuyuki , Tomita Naohide , Onmori Naoki , Kato Koji , Ikeuchi Ken 
Published: September 2003

AbstractIn order to examine the initiation mechanism of delamination in ultrahigh molecular weight polyethylene (UHMWPE) knee components, a bi‐directional sliding fatigue test was performed for three types of UHMWPE specimens: nonirradiated, gamma‐irradiated (25 kGy) and gamma‐irradiated (25 kGy) with 0.1% vitamin E added. Sliding surfaces of post‐tested UHMWPE specimens were observed using an optical microscope and a scanning electron microscope. Also, surface roughness was measured at the sliding surfaces of UHMWPE specimens. Delamination was observed only in gamma‐irradiated specimens. A networked structure of surface asperity that resembled grain boundary was observed prior to delamination in gamma‐irradiated specimens. Surface roughness in the gamma‐irradiated specimens, higher than in any other specimen, showed a rapid increase prior to delamination. Detailed observation using an optical microscope and a scanning electron microscope showed microscopic crack initiation along subsurface grain boundaries in gamma‐irradiated specimens. These results suggest that subsurface crack initiation is a precursor of delamination and is accelerated by oxidative degradation due to gamma irradiation. Of the three types of specimens, UHMWPE with vitamin E added showed the lowest surface roughness values at all measuring points. The addition of vitamin E is effective in improving wear resistance and fatigue performance of UHMWPE. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res 67A: 276–284, 2003
Biology of alkali‐ and heat‐treated titanium implants
Authors: Nishiguchi Shigeru , Fujibayashi Shunsuke , Kim Hyun‐Min , Kokubo Tadashi , Nakamura Takashi 
Published: September 2003

AbstractIn cementless fixation systems, surface character is an important factor. Alkali and heat treatments of titanium metal have been shown to produce strong bonding to bone and a higher ongrowth rate. In this study we examined the effect of alkali and heat treatments on titanium rods in an intramedullary rabbit femur model, in regard to the cementless hip stem. The implant rods were 5 mm in diameter and 25 mm in length. Half of the implants were immersed in 5 mol/L sodium hydroxide solution and heated at 600°C for 1 h (AH implants), and the other half were untreated (CL implants). The rods were implanted into the distal femur of the rabbits; AH implants into the left femur and CL implants into the right. The bone‐implant interfaces were evaluated at 3, 6, and 12 weeks after implantation. Pull‐out tests showed that the AH implants had a significantly higher bonding strength to bone than the CL implants at each time point. As postoperative time elapsed, histological examination revealed that new bone formed on the surface of both types of implants, but significantly more bone made direct contact with the surface of the AH implants. At 12 weeks, approximately 56% of the whole surface of the AH implants was covered with the bone. In conclusion, alkali‐ and heat‐treated titanium offers strong bone bonding and a high affinity to bone as opposed to a conventional mechanical interlocking mechanism. Alkali and heat treatments of titanium may be suitable surface treatments for cementless joint replacement implants. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res 67A: 26–35, 2003
Optimization of bone engineering by means of growth factors in a three‐dimensional matrix
Authors: Arnold Ulrike , Schweitzer Sven , Lindenhayn Klaus , Perka Carsten 
Published: September 2003

AbstractThe direction and acceleration of differentiation by administering growth factors is one of the ways of optimizing bone engineering. The present study considered the influence of the growth factors factor XIII, TGF‐β1, and b‐FGF on the proliferation and osteogenic differentiation of porcine periosteal cells in a three‐dimensional carrier matrix (bead), consisting of a fibrin–alginate–hydroxyapatite composite. F XIII, TGF‐β1, and b‐FGF were added to the culture medium of monolayer culture and fibrin beads in different concentrations. The monolayer culture was assessed on the basis of cell counts, while DNA, osteocalcin, osteonectin, and collagen content and alkaline phosphatase activity were determined, and microscopic and immunohistologic evaluations were performed for the beads. In the monolayer, the addition of b‐FGF led to a significantly shorter time up to the confluence of the cells. In the bead, cell proliferation was accelerated by b‐FGF and TGF‐β1. With regard to alkaline phosphatase activity, factor XIII led to significantly higher values, while b‐FGF and TGF‐β1 resulted in lower activities. Osteocalcin content was significantly increased by the application of b‐FGF. For the osteonectin content the addition of growth factors did not produce any changes. The application of TGF‐β1 during the monolayer culture significantly increased the primary collagen content of the beads. The administration of different growth factors opens up new ways of optimizing cell growth in vitro and of directing the osteogenic differentiation of periosteal cells, without one universally applicable factor having been demonstrated. It will be the task of further studies to analyze the interaction of individual factors and the chronologic dependency of the action, on the way to in vitro bone generation. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res 67A: 260–269, 2003
Protein adsorption on titanium surfaces and their effect on osteoblast attachment
Authors: Yang Yunzhi , Cavin Renee , Ong Joo L 
Published: September 2003

AbstractThe objective of this study was to investigate the adsorption of albumin and fibronectin on titanium (Ti) surfaces and the effect of preadsorbed albumin and fibronectin on osteoblast attachment in vitro. Bovine serum albumin and bovine fibronectin were used in this study. Maximum adsorption of bovine serum albumin and fibronectin on Ti surfaces was observed to occur after 180‐min incubation. In the presence of preadsorbed proteins, osteoblast attachment on Ti surfaces was observed to be enhanced compared to control Ti surfaces. However, cell attachment was affected by the types of protein adsorbed. Preadsorbed albumin was observed to have no significant effect on the amount of osteoblast cells attached. In comparison to control Ti surface and Ti surfaces preadsorbed with albumin, Ti surfaces preadsorbed with fibronectin for 15 min was observed to significantly increase osteoblast cell attachment, whereas Ti surfaces preadsorbed with fibronectin for 180 min did not affect cell attachment. In addition, cell morphology of the attached cells on protein preadsorbed Ti surfaces was not affected by the type of protein used in this study. It was concluded from this study that the concentration of fibronection adsorbed on Ti surfaces was higher compared to albumin. In addition, it was also concluded that the concentration of fibronectin on Ti surfaces plays a role in governing cell attachment. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res 67A: 344–349, 2003