bluuebunny/crossref_metadata_2025_split huggingface dataset:
Mineralization of alkaline phosphatase‐complexed collagenous implants in the rat: Relation with age, sex, and site of implantation
Authors: van den Bos T. , Beertsen W. 
Published: May 2005

AbstractThis study was designed to determine the effects of age, sex, and site of implantation on the extent of alkaline phosphatase‐complexed collagen sheets mineralization in the animal body. Collagen sheets were prepared from bovine dentin and cortical bone and complexed with varying amounts of intestinal alkaline phosphatase (ALP).1 Controls were without enzyme or with heat‐inactivated enzyme. Sheets were implanted subcutaneously over the skull and in the dorsolateral abdominal wall in 5‐ or 20‐ week‐old male and female Wistar rats. After 2–3 weeks the implants were removed and analyzed for phosphate and calcium content. Our findings have shown that alkaline phosphatase‐induced mineralization of collagenous implants is influenced to a considerable extent by age, sex, and site of implantation. Highest mineral influx was seen in the younger males. Implants in younger females and older males contained less mineral, whereas those installed in the older females were almost free of calcium phosphate deposits. Dentinal implants in the skull region contained more mineral than those in the abdominal wall. © 1994 John Wiley & Sons, Inc.
Correlations between orthogonal mechanical properties and density of trabecular bone: Use of different densitometric measures
Authors: Keyak J. H. , Lee I. Y. , Skinner H. B. 
Published: May 2005

AbstractTo compare the numerous modulus‐density and strengthdensity relations that have been found for human trabecular bone from the proximal tibia, correlations between various measures of density were sought. Hydrated and dry apparent density, ash density, and density from quantitative computed tomography (QCT) were determined for cubic trabecular specimens taken from the proximal portion of human tibiae, and correlations between these measures were found(r > 0.99, P <.001). Orthogonal moduli and strengths of the specimens were measured mechanically, and were significantly correlated with ash density according to power relations (r ≥ 0.85, P <.001). The strong correlation between density from QCT and ash density indicates that these measures can be used with nearly equal precision in estimating modulus and strength of tibial trabecular bone. Equations between mechanical properties and density reported in previous studies were converted to use a common density measure and, after considering the effects of specimen size, were in general agreement with results of the present study. © 1994 John Wiley & Sons, Inc.
Osteoclastic resorption of apatite formed on apatite‐ and wollastonite‐containing glass‐ceramic by a simulated body fluid
Authors: Yamada S. , Nakamura T. , Kokubo T. , Oka M. , Yamamuro T. 
Published: May 2005

AbstractWe immersed mirror‐polished apatite‐ and wollastonite‐containing glass‐ceramic (A‐W GC) disks in a simulated body fluid (SBF) for 5 days to form bonelike apatite on their surface. Neonatal rabbit bone cells were cultured on these on plain A‐W GC disks for 10, 24, and 48 h. We observed the substrates by scanning electron microscopy after treating them with pronase E plus EDTA to remove all cells except osteoclasts. Osteoclasts with a non‐motile appearance formed no lacunae on the plain A‐W GC, whereas on the bonelike apatite formed on A‐W GC by the SBF, actively moving osteoclasts made many tracklike resorption lacunae. These were evident even after 10 h of culture and became more extensive after longer culture periods. The bonelike apatite was therefore a more suitable medium than plain A‐W GC for maintaining osteoclast activity. This study demonstrated in vitro osteoclastic resorption of bonelike apatite formed on A‐W GC by an SBF. It suggests that the apatite layer, through which a surface‐active ceramic bonds to bone in vivo, can be resorbed by osteoclasts and subjected to bone remodeling. © 1994 John Wiley & Sons, Inc.
In vitro flexural fatigue limits of dental composites
Authors: Braem M. J. A. , Davidson C. L. , Lambrechts P. , Vanherle G. 
Published: May 2005

AbstractThe flexural fatigue test equipment developed was used to study the fatigue behavior of dental restorative composites, using a “staircase” approach. Three commercial composites were tested after dry and wet storage conditions. The findings indicate that the method is accurate and reliable, and that changes due to water sorption are clearly reflected: The flexural fatigue limit decreases after water sorption. From the present results it seems that under environmentally controlled conditions, the fatigue stress level above which the composites tested fail rapidly, and below which they survive. © 1994 John Wiley & Sons, Inc.
Mineralization and pH relationships in healing skeletal defects grafted with demineralized bone matrix
Authors: Chakkalakal D. A. , Mashoof A. A. , Novak J. , Strates B. S. , McGuire M. H. 
Published: May 2005

AbstractEarly studies had indicated that tissue repair is intially associated with a lower than normal serum pH that later becomes more alkaline. To determine how tissue pH may affect skeletal healing and mineralization, we used a rat skeletal repair model consisting of a long bone segmental defect grafted with acid‐demineralized bone matrix (DBM), a biomaterial possessing both osteoinductive and osteoconductive repair properties. In this study, femoral and tibial diaphyses from young adult Sprague Dawley rats were cut into cylinders approximately 0.5 cm in length, demineralized in acid, perforated to accommodate a needle‐type combination pH microelectrode, and grafted around a 0.3‐cm‐long diaphyseal fibula defect. The pH of repair tissues was recorded at various time intervals up to 28 days postgrafting. Healing and mineralization were monitored histologically and by the ash and calcium content of repair tissues. During the early healing phase, tissue pH was lower than normal serum pH, presumably because of an accumulation of acidic metabolites in tissue fluids. Subsequent pH increases to more alkaline values were accompanied by a rapid mineral deposition phase and a later phase characterized by a slow, gradual increase in tissue calcium content. The results of this study support previous observations suggesting that the pH of repair tissue fluids may play a regulatory role in the healing and mineralization of bone. © 1994 John Wiley & Sons, Inc.
Erosion of a new family of biodegradable polyanhydrides
Authors: Shieh L. , Tamada J. , Chen I. , Pang J. , Domb A. , Langer R. 
Published: May 2005

AbstractStudies investigating the erosion mechanism of the newly developed poly (fatty acid dimer: sebacic acid) polyanhydride (p:[FAD:SA]) are described. The overall erosion of different monomer compositions of p(FAD:SA) copolymers was examined to determine whether and to what extent copolymer properties affected polymer erosion. Increasing the hydrophobic monomer (FAD) content up to 50 wt% in the copolymer resulted in longer erosion, whereas further increases up to 70 wt% decreased the erosion period. Polymer crystallinity depended on copolymer FAD content. Copolymer degradation was studied by examining anhydride bond hydrolysis using infrared spectroscopy. Much faster hydrolysis was found in p(FAD:SA) 70:30 compared with more crystalline copolymers of higher SA content. Light microscopy indicates the presence of an erosion zone, a distinct area where mass loss occurs. This erosion zone moves from the outside toward the interior of the polymer matrix. It plays an important role in erosion because any water or monomer must diffuse through this eroded layer. © 1994 John Wiley & Sons, Inc.
Nanoapatite and organoapatite implants in bone: Histology and ultrastructure of the interface
Authors: Müller‐Mai C. M. , Stupp S. I. , Voigt C. , Gross U. 
Published: May 2005

AbstractThis article reports on the reaction of bone to a new family of nanocrystalline hydroxyapatite biomaterials with crystal sizes similar to those of human bone. Pure nanoapatite cylinders and organoapatite cylinders containing a synthetic nanopeptide were analyzed 28 days after implantation into the spongy bone of Chinchilla rabbits. The experimental techniques used for analysis were light microscopy, scanning electron microscopy, and transmission electron microscopy. Both implant types were well incorporated, and interface events were found to be similar to those observed on human bone surfaces with regard to resorption by osteoclast‐like cells and bone formation by osteoblasts. Different types of giant cells were observed resorbing the outermost surfaces of implants. There seemed to be both dissolution of the implant and particulate biodegradation leading to less dense implant regions near the interface, whereas the bulk of the implants remained denser. Transmission electron micrographs revealed that bone bonding occurred with and without an afibrillar intervening layer. Given the biologic reaction observed, these implant materials should be suitable for bone replacement and the organoapatite form could be useful for additional functions such as the release of drugs and optimized release of antibiotics, growth factors, or other substances. The organic component can also be used to control physical properties in a bony implantation bed. © 1995 John Wiley & Sons, Inc.
Comparison of bone‐implant interface shear strength of hydroxyapatite‐coated and alumina‐coated metal implants
Authors: Inadome T. , Hayashi K. , Nakashima Y. , Tsumura H. , Sugioka Y. 
Published: May 2005

AbstractWe performed a transcortical push‐out test to determine the effect of surface roughness of hydroxyapatite (HA)‐coated implants on bone‐implant shear strength in a canine model. Hydroxyapatite‐ and alumina‐coated SUS316L with the same surface roughness (roughness average: Ra = 5 μm) and HA‐coated Ti‐6Al‐4V (Ra = 8.4 μm), sintered HA (Ra = 0.9 μm), and dense alumina (Ra = 1.3 μm) were inserted into the dog's femur. The interface shear strength of the dense alumina was significantly lower than that of other implants at both 4 and 12 weeks after implantation. At 4 weeks after implantation, the interface shear strength of the alumina‐coated SUS316L was significantly lower than that of other implants (P < .05) except the dense alumina, but at 12 weeks, there was no significant difference between the implant types except the dense alumina. This indicates that the surface roughness of the HA coating affects the enhancement of the bone‐implant interface shear strength at the early period after implantation, and that a surface roughness of several micrometers does not influence the bond strength between bone and HA. A scanning electron microscopic study indicated that in almost all cases at 12 weeks, the failure site after push‐out testing was the coating‐substrate interface, not the coating‐bone interface. Therefore, protection of the coating‐substrate interface from direct shear loading is needed. © 1995 John Wiley & Sons, Inc.
Effect of particle size of metastable calcium phosphates on mechanical strength of a novel self‐setting bioactive calcium phosphate cement
Authors: Otsuka Makoto , Matsuda Yoshihisa , Suwa Yoshiko , Fox Jeffrey L. , Higuchi William I. 
Published: May 2005

AbstractResistance to compressive strength after setting of the calcium phosphate cement consisting of tetracalcium phosphate (TECP), dicalcium phosphate dihydrate (DCPD), and 40 wt/wt% of a synthetic hydroxyapatite (HAP) was tested. An equimolar mixture of the calcium phosphate powder containing DCPD (particle diameter [D] 0.52–3.33 μm) and TECP (D, 1.1–13.1 μm) transformed into HAP at 37°C, 100% RH after being mixed with 25 mM phosphoric acid. X‐ray diffraction suggested that the cement containing fine particles of DCPD and TECP completely transformed to HAP, but that mixtures containing larger particles did not. Because particle size of both DCPD and TECP affected the compressive strength of the cement, the crystal growth of HAP during cement formation depended on the specific surface area (Sw) of the raw materials. The crystallite size of transformed HAP was estimated based on X‐ray diffraction peaks at 25.8 and 32.8° attributable to the 002 and 300 planes. The crystallite size attributable to the 300 plane decreased with increasing Sw, but that attributable to the 002 plane showed no significant relationship. The compressive strength of the cement after hardening increased with an increase of its Sw. This suggested that the harder calcium phosphate cement was (derived) from the smaller particle size of the raw materials. © 1995 John Wiley & Sons, Inc.
Kinetic study of release of silicon compounds from polysiloxane tissue expanders
Authors: Raimondi M. L. , Sassara C. , Bellobono Ignazio Renato , Matturri L. 
Published: May 2005

AbstractThe release behavior of typical commercial tissue expanders has been examined by carrying out two kinds of experiments: (1) Determination of chemical nature and its modification after in vivo use by X‐ray photoelectron spectroscopy for chemical analysis. This study has been parallelled by scanning electron microscopy with associated energy dispersive X‐ray analysis of surface, as well as by silicon compounds analysis of tissues around implants. (2) Kinetic examination of silicon compounds released by the biomaterial in physiologic solution at 36 ± 0.3°C. Results of these investigations have shown independently that the starting material was not a filler‐free, pure polymer, but a composite, reinforced elastomer, with the reinforcing agent most seemingly represented by silicon dioxide. Release of latter, with a relatively fast kinetics, is compatible with data of the simulating laboratory runs in the physiologic solution. All these facts seem to rule out any hypothesis of a prevailing siloxane oligomer migration. The correlation of kinetic and physicochemical tests with the in vivo behavior is discussed. © 1995 John Wiley & Sons, Inc.
Crystal structure of the surface oxide layer on titanium and its changes arising from immersion
Authors: Effah E. A. B. , Bianco P. D. , Ducheyne P. 
Published: May 2005

AbstractThe passivating surface oxide on titanium is one of the elements considered in the explanation of the favorable biolgic response of this metal in implant applications. In the present study, transmission electron microscopy was used to identify the crystal structure and morphology of the oxide film on commercially pure titanium specimens befor and after immersion in simulated physiologic fluids. The results show that the oxide layer is composed mainly of anatase and rutile, both of which are tetragonal in structure. Although the simulated physiologic fluids did not induce an observable change in the crystal structure for the immersion times investigated, the results indicate an immersion‐induced change in microstructure from a finegrained to a coarser‐grained structure. The grain growth observed could be attributed to the growth of the native oxide crystals; however, it most likely results from the formation of a new oxide layer. The results also support oxide thickening as one of the processes associated with passive dissolution of titanium. © 1995 John Wiley & Sons, Inc.
Variation in contact guidance by human cells on a microstructured surface
Authors: Meyle J. , Gültig K. , Nisch W. 
Published: May 2005

AbstractContact guidance induced by the surface topography of the underlying substratum influences the interaction of tissue cells with implanted material. It was the aim of this study to compare the reaction of different human cells on the same surface microtexture. After staining with fluoresceinediacetate, the orientation of human fibroblasts, gingival keratinocytes, neutrophils, monocytes, and macrophages on a regular surface microstructure of 1 μm pitch and 1 μm depth was analyzed by fluorescence microscopy. Contact guidance could not be observed in the experiments with keratinocytes and neutrophils, but 100% of the fibroblasts and approximately 20% of the monocytes and macrophages reacted with alignment. After 2 h some of the macrophages extended long dendritic cellular processes parallel to the long axis of the microstructures. © 1995 John Wiley & Sons, Inc.
Simple technique for the preparation of silicone gel particles: The effect of silicone gel particles on oxidative responses of macrophages
Authors: Azizsoltani E. , Myrvik Q. N. , Foster L. A. , Giridhar G. , Gristina A. G. 
Published: May 2005

AbstractA simple technique was developed to prepare phagocytosable‐size particles from the silicone gel used in breast implants. Sonication of silicone gel (1 g) in 5 ml of 20 mM sodium phosphate buffer (pH 7.2) containing 1% (wt/vol) polyoxypropylene‐polyethylene block surfactant (F‐68 or F‐108) produced silicone gel particles ranging from 1–50 μm in diameter. Passage of the suspension through a series of filters yielded phagocytosable particles (1–5 μm in diameter) at a concentration of ca. 2 × 109 particles/ml. The particles remained as individual particles, did not coalesce to form large clumps, and were not pelleted by centrifugation (2000 × g, 20 min). They were not toxic for rabbit alveolar macrophages (AM) during 24 h of incubation at 37°C, did not elicit an oxidative burst from AM in vitro in a luminolenhanced chemiluminescent assay, and did not significantly increase the phorbol myristate acetate (PMA)‐elicited oxidative burst by AM. AM isolated from rabbits 2 days after the intravenous injection of silicone particles were not primed or activated (i.e., the AM did not show an enhanced oxidative burst when elicited with PMA in vitro). However, AM isolated from rabbits 2 days after intratracheal injection of the particles were primed but only exhibited a 4–6‐fold increase in the oxidative burst elicited with PMA. © 1995 John Wiley & Sons, Inc.
Effects of a structural change in collagen upon binding to conditioned dentin studied by 13C NMR
Authors: Nishiyama Norihiro , Asakura Tetsuo , Suzuki Kazuomi , Horie Kozo , Nemoto Kimiya 
Published: May 2005

AbstractTo develop a better adhesive functional monomer, it is imperative to understand the adhesion mechanisms of the resin to the dentin surface. Bond strength to the decalcified dentin surface pretreated with dentin primer, an aqueous ethanol solution of N‐methacryloyl glycine, increases by increasing the water content in the primer. The aqueous primer could increase the thickness of the hybrid layer. The structural change of dentinal collagen with NMαA was studied by using a model compound for collagen,—(1Pro‐2Pro‐3Gly)10—, by 13C nuclear magnetic resonance (NMR). The model compound was aggregated in ethanol but dissociated in water. It was found that NMαA effectively dissociated the aggregated model compound in water. The dissociation of decalcified dentin was essential to create a thick hybrid layer that could afford a higher bond strength to dentin. © 1995 John Wiley & Sons, Inc.
Studies on the tumor‐promoting activity of additives in biomaterials: Inhibition of metabolic cooperation by phenolic antioxidants involved in rubber materials
Authors: Tsuchiya Toshie , Fukuhara Kiyoshi , Hata Hideyo , Ikarashi Yoshiaki , Miyata Naoki , Katoh Fumitaka , Yamasaki Hiroshi , Nakamura Akitada 
Published: May 2005

AbstractFor the detection of tumor‐promoting activities of phenolic antioxidants, the inhibitory activities on the intercellular gap‐junctional communication were investigated using the V79 metabolic cooperation (MC) assay. Among eight antioxidants, 4,4′‐butylidene‐bis(3‐methyl‐6‐tert‐butyl‐phenol), 2,2′‐methylene‐bis(4‐methyl‐6‐tert‐butylphenol) (MBMBP), and styrenated phenol (SP) showed stronger inhibitory activities than lithocholic acid, which is known to be a tumor promotor. However, 4,4′‐thio‐bis(3‐methyl‐6‐tert‐butylphenol), Irganox 1010, and 1330 did not inhibit at any concentrations. When the single‐electron oxidation potentials were compared among antioxidants, the electrochemical ease estimated with the first oxidation potential was correlated with the cytotoxic potentials (r = 0.88), but not with the inhibitory activities in an MC assay. The tumor‐promoting activity of MBMBP was also investigated using an in vitro, two‐stage Balb/c 3T3 transformation assay. MBMBP did not show initiating activity, but significant promoting activity at concentrations of both 1 and 2.5 μg/ml were noted. These concentrations were close to the lowest effective inhibitory concentration (1.3 μg/ml) of MBMBP in an MC assay. In conclusion, there is a possibility that the phenolic antioxidants that show inhibitory activities in an MC assay contribute to the enhancement of tumor incidence induced by biomaterials. © 1995 John Wiley & Sons, Inc.
Role of glutaraldehyde in calcification of porcine heart valves: Comparing cusp and wall
Authors: Girardot Marie‐Nadia , Torrianni Mark , Dillehay Dirck , Girardot Jean‐Marie 
Published: May 2005

AbstractExperiments were performed to better understand the relationship between glutaraldehyde and calcification of bioprosthetic heart valves, using both the cusps and the wall of porcine aortic roots. The results of the first experiment, for which 3H‐labeled glutaraldehyde solutions were used, indicated that binding of glutaraldehyde in cusps and wall is concentration‐dependent, that the wall contains significantly less glutaraldehyde than the cusp, and that glutaraldehyde, which penetrates in the wall at similar rates from the intima and the adventitia, is homogeneously distributed throughout the wall after 7 days of fixation, except for the intima side, where it is significantly lower. The results of the second experiment, for which cusps and 1‐cm2 pieces of wall from glutaraldehyde‐fixed porcine aortic roots were implanted subdermally in young rats, indicated that for both types of tissue, calcification appears to first initiate predominantly in the cell nuclei before extending to the other structures. After 8 weeks of implantation, whereas the cusps were completely calcified, calcification of the wall was limited to two longitudinal bands 150–300 μm thick, located below the adventitia and intima surfaces. The results of the third experiment indicated that cusp calcification, which decreased significantly after a 12‐month storage period, was reset to high levels by reexposing the valves to glutaraldehyde at the end of the 12‐month storage period. Wall calcification remained constant under all tested conditions. The results suggest that the mechanism(s) of calcification in the wall and the cusp may be different, and that calcification may be relted to a particular molecular configuration resulting from exposure to glutaraldehyde. © 1995 John Wiley & Sons, Inc.
In vitro evaluation of cytotoxicity of diepoxy compounds used for biomaterial modification
Authors: Nishi Chika , Nakajima Naoki , Ikada Yoshito 
Published: May 2005

AbstractThe toxicity of various diepoxy compounds used for biomaterials crosslinking was investigated with a cell culture method and compared with an in vivo method. The neutral red uptake by cells was used to count the number of cells still alive after contact with the diepoxy compounds, because this method was more sensitive in cell counting than the other four methods studied in this work. The amount of neutral red taken up by cells depended strongly on the activity of cells in comparison with other methods; only small amounts of neutral red were taken up when cells were in a low activity state even if they were still alive. The in vitro toxicity of diepoxy compounds evaluated by the neutral red method revealed a good correlation with that found by the in vivo Draize test. The in vitro cytotoxicity to a cell line of L929 was closely related to that of primary culture cells of the normal rabbit cornea epidermal cell. The toxicity of diepoxy compounds was lower as their chain was longer, probably because of the lower chemical reactivity. All the diepoxy compounds investigated in this study exhibited lower cytotoxicity than formaldehyde, glutaraldehyde, and a water‐soluble carbodiimide. © 1995 John Wiley & Sons, Inc.