bluuebunny/crossref_metadata_2025_split huggingface dataset:
Thermal shock resistance of core reinforced all‐ceramic crown systems
Authors: Mora Gary P. , O'Brien William J. 
Published: May 2005

AbstractThe coefficient of thermal expansion of core and veneer porcelains for all ceramic crowns must be compatible to prevent formation of stresses during the firing cycles. The purpose of this study was to use a thermal shock test to evaluate the crazing resistance of six all‐ceramic crown systems. The systems tested were: Vita In‐Ceream®, Vita Hi‐Ceram®, Dicor™ veneered with Vitadur® N, magnesia core veneered with Ceramco® II, magnesia core veneered with Silhouette™, and magnesia core veneered with Vita VMK® 68. A maxillary central incisor was prepared with 1.0 mm axial and 1.5 mm incisal reduction. Refractory dies were prepared and crowns were fabricated using the manufactures recommendations. Six specimens of each system were placed inside a beaker in a furnace at 90°C. After 15 min heat soak, ice water was poured into the beaker through a funnel. The samples were dried in air, reheated, and inspected for crazing using light microscopy. If crazing was observed, this would constitute a failure at a temperature difference (ΔT) of 90°C. If no failure occurred, the test was repeated at increasing temperature increments of 10°C until failure. The crazing resistance of each system, expressed as the mean ΔT, was: > 200 (Hi‐Ceram®), 152 ± 19 (Dicor™ / Vitadur® N), 143 ± 5 (magnesia core/Vita VMK® 68), 122 ± 21 (magnesia core/Silhouette™), and 118 ± 10 (magnesia core/Ceramco® II) °C. All systems tested resisted crazing due to quenching in ice cold water from 100°C. Systems with lower coefficients of expansion showed significantly greater resistance to thermal shock using ANOVA. © 1994 John Wiley & Sons, Inc.
Microvascular endothelial cell sodding of ePTFE vascular grafts: Improved patency and stability of the cellular lining
Authors: Williams Stuart K. , Rose Deborah G. , Jarrell Bruce E. 
Published: May 2005

AbstractSmall diameter (<6 mm) synthetic vascular grafts fail at a clinically unacceptable rate due in large part to their inherent thrombogenicity. The development of a new cellular lining on synthetic vascular grafts would most likely improve the patency rates observed for these grafts in small diameter positions. We have evaluated the use of endothelial cell transplantation to accelerate the formation of a cell lining using microvascular endothelial cells derived from canine falciform ligament fat. This source of fat is histologically similar to human liposuction fat and was isolated using a collagenase digestion technique identical to methods used for human liposuction fat microvessel endothelial cell isolation. The isolated fat endothelial cells were sodded onto 4 mm ePTFE grafts using pressure to force the cells onto the luminal surface. This pressure sodding method permitted cell deposition in less then 3 min. Sodded and control (non—cell‐treated) grafts were implanted as interpositional paired grafts using end‐to‐end anastomoses in the carotid arteries of mixed breed dogs. Each dog therefore received a sodded graft on one side and a control graft on the contralateral side. After 12 weeks of implantation all control grafts were occluded while 86% of the cell‐sodded grafts remained patent. Statistical evaluation of the data revealed a significant improvement in patency of cell sodded grafts (McNemar's χ2 P =.02). Morphological evaluation of grafts explanted at 5, 12, 26, and 52 weeks following implantation revealed the presence of a cell lining on sodded grafts which remained stable for a period of at least one year. This new cell lining exhibited morphologic characteristics of a nonthrombogenic endothelial cell lining. The development of this new intima, evaluated 5 weeks–1 year after implantation, was not associated with a progressive intimal hyperplasia. From these data we conclude that microvessel endothelial cells derived from canine falciform ligament fat can be rapidly isolated using an operating room compatible method. Cell deposition on synthetic grafts is subsequently accelerated using a pressure sodding technique. A cellular lining forms on the inner surface and is associated with a statistically significant improvement in the function of sodded grafts in a canine carotid artery model. © 1994 John Wiley & Sons, Inc.
Confocal laser scanning microscopy (CLSM) for the study of collagen sponge microstructure
Authors: Hanthamrongwit M. , Grant M. H. , Wilkinson R. 
Published: May 2005

AbstractThis study uses confocal laser scanning microscopy (CLSM) to assess the microstructure of collagen sponges providing an accurate quantification of porosity under conditions similar to those experienced by cells growing on the sponges during culture. CLSM offers several advantages over scanning electron microscopy (SEM) and conventional optical microscopy for this kind of study, the most important of which is probably the absence of artifacts associated with the extensive preparation of samples required for the latter two methods. When the “pan‐side” surface of collagen sponges was studied, it was found that the pore sizes increased with increasing depth into the sponge. Collagen sponges frozen in a −70°C freezer had a more open structure than ones frozen on the stage of a tissue dryer. These different pore sizes are thought to reflect different freezing rates in the samples. © 1994 John Wiley & Sons, Inc.
Interfacial behavior of PEO/PBT copolymers (polyactive®) in a calvarial system: An in vitro study
Authors: Radder A. M. , Davies J. E. , Leenders H. , van Blitterswijk C. A. 
Published: May 2005

AbstractPolyactive®, a polyethylene oxide/ polybutylene terephthalate (PEO/PBT) copolymer, has been reported to display bone‐bonding behavior. Although a detailed description of the in vivo bone/ Polyactive® interface is available, the underlying bone‐bonding mechanism is still largelyunknown. In this in vitro study, a calvarial envelope method has been adopted to reproduce the in vivo bone‐bonding phenomenon and subsequently to obtain information on the biological effect of varying PEO/PBT segment ratios. The following PEO/PBT ratios were examined: 70/30, 60/40, 55/45, 40/60, and 30/70. Light microscopy (LM) and scanning (SEM), transmission (TEM), and backscatter electron microscopy (BSE), as well as X‐ray microanalysis (XRMA), were employed. Within the period of analysis (3 weeks), an intimate contact between mineralized deposition and the 70/30, 60/40, and, to a lesser extent, the 55/45 surface was observed. Calcified areas developed within the surface of these PEO/BPT proportions during the culture period. Needle‐shaped crystals from the mineralized tissue compartment and from calcified areas within the materials surface were intermingled at the interface, providing a morphologic continuity. A cellular layer was interposed with the mineralization front and the noncalcified 40/60 and 30/70 substrates. Apparently, the percentage of PEO is important for calcification within the near surface of the polymer. This relation is such that the highter the PEO content in PEO/PBT ratios, the more rapid the calcification is considered. The occurrence of material calcification is considered to be largely responsible for the subsequent interfacial interactions. The calvarial envelope culture method allows not only reproduction of the in vivo bone/Polyactive® interface, but also a relatively rapid differentiation within the range of PEO/PBT ratios. It was therefore concluded that this in vitrosystem is suitable for further studies toward a better understanding of the bone/Polyactive® interfacial composition and the underlying mechanisms. © 1994 John Wiley & Sons, Inc.
Calcium phosphate formation on sol‐gel‐derived bioactive glasses in vitro
Authors: Pereira M. M. , Clark A. E. , Hench L. L. 
Published: May 2005

AbstractWhen soluble salts are used in the sol‐gel processing of bioactive glasses, the resulting materials are not homogeneous. To produce homogeneous gel‐glasses, a sol‐gel method using all alkoxide precursors was developed. In this work the in vitro bioactivity of the new all‐alkoxide gel‐glasses is investigated. Three compositions in the system, CaOP2O5SiO2, were studied. Solid samples were soaked in Tris buffer and simulated body fluid (SBF), and the rate of formation of hydroxy carbonate apatite (HCA) on the surface of the glasses was measured by Fourier transform infrared spectroscopy. The solutions were analyzed before and after reaction by inductively coupled plasma. All compositions studied formed a hydroxy carbonate apatite (HCA) layer within 8 h in both test solutions. The HCA layer grew rapidly when SBF was used. © 1994 John Wiley & Sons, Inc.
In vitro chondrocyte collagen deposition within porous HDPE: Substrate microstructure and wettability effects
Authors: Livecchi A. B. , Tombes R. M. , LaBerge M. 
Published: May 2005

AbstractThe effects of microstructure and wettability of porous high density polyethylene (HDPE) substrates on chondrocyte collagen synthesis in vitro were assayed. Three size grades of hydrophilic and hydrophobic HDPE substrates with ranges of pore volumes of 40–60%, pore sizes of 115–335 μm, and surface areas per unit volumes of 7–20 mm2/mm3 were seeded with fetal bovine chondrocytes. After 7 days of incubation, the cells within all substrates remained spherical, and contained mainly type II collagen (as verified by type I and II collagen I‐ELISAs). After 21 days, the majority of cells had spread; however, the matrices still contained mainly type II collagen. The hydrophilic matrices contained significantly more type II collagen than the hydrophobic matrices at both 7 and 21 days, whereas the amount of type II collagen was not influenced by the pore attributes. A significantly higher percentage of type II collagen was also observed in all seeded porous substrates as compared with seeded polystyrene culture dishes, perhaps indicating that the three‐dimensional particular nature of the HDPE matrices enhanced the maintenance of phenotypically differentiated chondrocytes and entrapment of their extracellular matrix products. © 1994 John Wiley & Sons, Inc.
Resistance of hyaluronate coatings to hyaluronidase
Authors: Lowry Karen M. , Beavers Ellington M. 
Published: May 2005

AbstractMucopolysaccharides such as hyaluronic acid and its salts are essential components of new hydrophilic bilaminar coatings being developed in these laboratories. The polysaccharide top‐coat is covalently bonded by periodic urethane links to a substrate copolymer which in this study has been coated on polymethyl methacrylate slabs. Such coated slabs were exposed for up to 28 months to three levels of hyaluronidase in phosphate buffered saline at 37°C, the enzyme concentration ranging from that normally present in human serum to 60 times that level. The coating survived without damage. The rationale proposed is that the enzyme is unable to position its active site with the immobilized hyaluronate molecule and is therefore unable to catalyze the hydrolysis. © 1994 John Wiley & Sons, Inc.
Calcium phosphate plasma‐sprayed coatings and their stability: An in vivo study
Authors: Klein C. P. A. T. , Wolke J. G. C. , De Blieck‐Hogervorst J. M. A. , de Groot K. 
Published: May 2005

AbstractSeveral factors playing a possible role in determining coating stability and bone tissue response were studied in in vivo experiments. These factors involving the plasmaspray coating procedure were as follows: (1) plasmaspray powder port 2 or 6; (2) particle size distribution; (3) hydroxylapatite versus fluorapatite coatings; and (4) the effect of post‐heat treatment. Coating stability and bone tissue response were examined by measuring coating thickness, coating thickness, coating length, and bone apposition against the coatings. The result was that heat treatment influenced coating stability significantly. Also, bone formation was more intense. Fluorapatite proved to be more stable than hydroxylapatite, which was in agreement with our previous reports. © 1994 John Wiley & Sons, Inc.
Characterizations of titanium implant surfaces. III
Authors: Keller John C. , Stanford Clark M. , Wightman James P. , Draughn Robert A. , Zaharias Rebecca 
Published: May 2005

AbstractThere are several reports in the literature concerning the similarities and the differences between the oxide on cpTi and Ti‐6Al‐4V alloy; however, their biological sequelae are not entirely known. In this work, a series of surface characterization techniques were used in conjunction with short termin vitrobiological assays to assess the effects of materials selection (cpTi and Ti alloy) on osteoblast‐like cell responses. Surface analysis indicated that with the exception of oxide thickness, there were no significant differences in surface characteristics between the two implant materials. These results were reflected in the biological studies, where the levels of cell attachment and adaptation of the attached cells to the titanium surfaces were similar. These results are in general agreement with previousin vivostudies and continue to indicate that cpTi and Ti alloy are suitable, biologically compatible materials for fabrication of dental implants. © 1994 John Wiley & Sons, Inc.
Features of calcium phosphate plasma‐sprayed coatings: An in vitro study
Authors: Klein C. P. A. T. , Wolke J. G. C. , de Blieck‐Hogervorst J. M. A. , De Groot K. 
Published: May 2005

AbstractFactors involved with the plasma‐spray coating procedure, such as starting powder compound (fluorapatite, hydroxylapatite, magnesium‐whitlockite, or tetra‐calcium phosphate), powder particle distribution 1–45 or 1–125 (μm), powder port gun (port 2 or 6), and post–heat treatment of 1 h at 600°C, were examined for their effects on crystallinity and solubility/stability of the coating. From solubility tests, X‐ray diffractometry, and scanning microscopy studies, the solubility and crystallinity were found to be dependent on Ca/P ratio, particle distribution, and post‐heat treatment. The post‐heat treatment influenced the degree of both crystallinity and solubility. The plasma‐spray powder port factor for the hydroxylapatite coatings was not significant. Incubation in buffer of the coatings introduced precipitation at the surfaces of all non–heat‐treated coatings except fluorapatite. No precipitation could be observed in any of the heat‐treated coatings. © 1994 John Wiley & Sons, Inc.
Mutagenicity of dentin bonding agents
Authors: Schweikl H. , Schmalz G. , Bey B. 
Published: May 2005

AbstractAside from the considerable number of reports on the physical and chemical properties of dental bonding agents, information concerning their biologic effects is sparse. Three dentin bonding agents (Prisma Universal Bond, Pertac Universal Bond, and Syntac) and the ingredients methylmethacrylate, 2‐hydroxyethyl‐methacrylate, and glutaraldehyde were investigated in the Salmonella typhimurium mutagenicity test system using five different bacterial strains (TA97a, TA98, TA100, TA102, and TA104). The materials as well as the ingredients were eluted in both dimethyl sulfoxide and physiologic saline, and serially diluted eluates were used in the plate incorporation test. Pertac Universal Bond and Prisma Universal Bond did not elicit any mutagenic effects in any of the bacterial strains. In contrast, Syntac adhesive showed clear mutagenicity in S. typhimurium strain TA102. Dimethyl sulfoxide eluates, as well as physiologic saline eluates of the Syntac bonding agent, caused numbers of revertants that were about 6 times higher than control values. Reversion rates with other strains were moderately enhanced. Glutaraldehyde, an ingredient of Syntac adhesives, caused mutagenicity in a manner similar to Syntac adhesive eluates. Neither 2‐hydroxyethyl‐methacrylate nor methylmethacrylate monomer was found to be mutagenic over a broad concentration range. © 1994 John Wiley & Sons, Inc.
Evaluation of three new hydrocolloid dressings: Retention of dressing integrity and biodegradability of absorbent components attenuate inflammation
Authors: Chakravarthy Debashish , Rodway Nancy , Schmidt Steven , Smith Daniel , Evancho Michelle , Sims Rick 
Published: May 2005

AbstractResidues from hydrocolloid dressings (HCDs) that originate from matrix disintegration and nonbiodegradability of the absorbent components, may cause deep‐seated, unresolved inflammation in tissue that appears otherwise healed. The purpose of this study was to evaluate three new HCDs that were formulated with the goal of attenuating the inflammatory responses that may arise from HCD therapy. Two of the HCDs (A‐06 and A‐07) consisted of conventional absorbents dispersed in a new maceration resistant adhesive matrix. The same matrix, mixed with potentially biodegradable dextran microspheres, formed the third dressing (Dextran Bead Dressing [DBD]). In this pilot scale study these novel dressings were evaluated on full‐thickness dermal wounds on swine. Restore (Hollister) and DuoDERM CGF® (Convatec) dressings were used as controls. Wound healing was evaluated histomorphometrically. Pertinent histologic parameters were ranked from wound tissue that was harvested 18 days after wounding. Grossly visible dressing disintegration ranged from minimal (DBD) to servere (Restore). Disintegration of other dressings was moderate. The percentage of tissue sections exhibiting giant cells reflected, in parallel, the observed extent of dressing disintegration. Thirty‐eight percent of wounds dressed with DBD contained giant cells; 74 and 100% of wounds treated with Duo DERM CGF® and Restore, respectively, contained giant cells. DBD‐dressed wounds had relatively fewer chronic inflammatory cells than other dressings. These wounds were also characterized by a well‐organized collagen matrix and complete reepithelialization. The extent of wound closures was similar for all dressing types except Restore. Closure of Restore‐dressed wounds was delayed compared with closure with DBD and DuoDERM CGF® on all days of evaluation except one. A‐06 and A‐07 were comparable to DuoDERM CGF® in retention of dressing integrity and the elicited inflammatory tissue response. The DBD dressing appears to possess equivalent properties of typical HCDs while causing minimal tissue reactions. © 1994 John Wiley & Sons, Inc.
Biodegradation evaluation of polyether and polyester‐urethanes with oxidative and hydrolytic enzymes
Authors: Santerre J. P. , Labow R. S. , Duguay D. G. , Erfle D. , Adams G. A. 
Published: May 2005

AbstractEnzyme‐induced liberation of components from seven different radiolabeled polyurethanes was monitored by radiolabel counting of the incubation solutions and product isolation by high performance liquid chromatography (HPLC). The polyurethanes were selected to reflect variations in the hard‐segment chemistry, soft‐segment chemistry, soft‐segment chemistry, and polyurethane hydrophilicity resulting from combinations of hydrophobic/hydrophilic soft segments. All materials were characterized using electron spectroscopy for chemical analysis, differential scanning calorimetry, size exclusion chromatography, and Fourier transform infrared spectroscopy. The material surfaces were examined both before and after incubation with enzyme and control solutions using scanning electron microscopy. Biodegradation assays were carried out at 37°C using cholesterol esterase (CE) and horseradish peroxidase (HRP) under optimal pH conditions for each enzyme. The hydrolytic enzyme (CE) was effective in releasing degradation products that contained hard‐segment components from some of the polyurethanes. HPLC analysis of products for a polyesterurethane synthesized with toluene diisocyanate (TDI) suggested that the bulk of the incorporated radiolabeled TDI was still covalently bonded within the cleaved chain segments of the original polymer and was not released as pure toluene diamine (TDA). The data suggest that urethane linkages in the soft‐segment domains of phase separated polyetherurea‐urethanes may be more prone to cleavage by CE than are the urea/urethane groups in the hard‐segment domains. This could be related to the nature of the hard‐segment domain structures. The oxidative enzyme (HRP) was not able to induce liberation of radiolabeled segments from either the polyether or polyester‐based polyurethanes. © 1994 John Wiley & Sons, Inc.
Materials testing protocol for small joint prostheses
Authors: Savory Kevin M. , Hutchinson Douglas T. , Bloebaum Roy 
Published: May 2005

AbstractIn this article, a protocol for the evaluation of new materials for small joint prostheses is introduced. The testing methods employed in the protocol were developed by reviewing reported clinical failure modes and conditions found in vivo. The methods developed quantitatively evaluates the fatigue, fatigue crack propagation, and wear resistance properties of materials. For this study, a silicone elastomer similar to Dow Corning Silastic HP100, a radiation stable polypropylene, and a copolymer of polypropylene and ethylene propylene‐diene monomer (EPDM) are evaluated. None of the materials tested demonstrated the ideal properties that are sought in a self‐hinging joint prostheses. The silicone elastomer had excellent wear properties; however, cracks quickly propagated, causing catastrophic failure when fatigued. Conversely, the copolymer showed excellent fatigue crack propagation resistance and less than favorable wear properties. The polypropylene did not perform well in any evaluation. © 1994 John Wiley & Sons, Inc.
Detection of antibodies against corrosion products in patients after CoCr total joint replacements
Authors: Yang Jun , Merritt Katharine 
Published: May 2005

AbstractSensitivity to nickel, cobalt, and chromium is common among the general population. The identification of these sensitivities is generally by the detection of cell‐mediated immunity. Detection of humoral immunity to these metals has rarely been undertaken because suitable assays are not available. To further our knowledge about the systemic humoral immune system response to weak hapten‐systemic or allogeneic protein conjugates (corrosion and wear products of metallic orthopedic devices), a sensitive enzymelinked immunosorbent assay (ELISA) method for testing for antibody (humoral immunity) to metals was developed. Microtiter plates were coated with human serum albumin (HSA) or glutathione (GSH) and then conjugated with metal ions. Plates coated with HSA or GSH and without metal ions served as background controls. An indirect ELISA method was used to detect antibody binding. Patients bearing cobalt‐chromium alloy devices were considered to be the most likely candidates as sources of antibody to metal and were used to document the usefulness of the test. Specificity of the test was documented by inhibition studies with these metal ions in the ELISA assay. The serum samples of 10 patients were screened for the presence of Cr‐, Co‐, or Ni‐specific antibody at various periods up to 5.5 years after implantation of F‐75 cobalt alloy total joint replacements. All patients had implants that were functioning well. The pre‐ and postimplantation humoral immune profiles of patients were determined and compared with each preimplantation control and with a pooled normal serum sample. This study presents evidence that metalprotein complex‐specific antibodies can be detected. The clinical implications remain to be determined. © 1994 John Wiley & Sons, Inc.