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At least 19 recordsLinked to original sources
PubMed1984

Metabolism of 7,12-dimethylbenz(a)anthracene by alveolar macrophages containing ingested ferric oxide, aluminum oxide or carbon particles.

Rat alveolar macrophages with ingested aluminum oxide (Al2O3), ferric oxide (Fe2O3) or carbon particles were incubated for 24 hours with 3H-7, 12-dimethylbenz(a)anthracene (DMBA). Essentially the same amounts and types of metabolites were produced by and released from macrophages with ingested Fe2O3 and Al2O3 particles. Smaller quantities of DMBA and its metabolites could be extracted with ethyl acetate from the culture media and cell lysates of macrophages with ingested carbon particles than from those with Fe2O3 and Al2O3 particles. Also, more of the intracellular radioactivity was associated with insoluble material in macrophages with ingested carbon than in those with the other two types of particles. The results suggest that the inability of Al2O3 to act as a co-carcinogenic carrier for polycyclic aromatic hydrocarbons (PAH) is not related to its effect on PAH metabolism. However, adsorption of PAH and their nonpolar metabolites to carbon may alter the exposure pattern of pulmonary tissues to PAH and their metabolites.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1976

Carcinogenicity of Benzo(a)pyrene and dusts in the hamster lung (instilled intratracheally with titanium oxide, aluminum oxide, carbon and ferric oxide).

The possible carcinogenic or fibrogenic effects of intratracheal instillation of a polycyclic hydrocarbon, benzo(a) pyrene (B(a)P), alone or in combination with several dusts - titanium dioxide (TiO2), aluminum oxide (Al2O3), carbon (C), and ferric oxide (Fe3O3) - were investigated in hamsters. When administered alone, the dusts induced interstitial cell proliferation, bronchial epithelial alterations and a few granulomatous changes in the pulmonary system, but no tumors. B(a)P alone induced only two tracheal papillomas. However, combined treatment with B(a)P and the dusts caused a number of tumors, dependent upon the dust used. B(a)P plus TiO2 in a small particle size (below 0.5mu) induced papillomas, squamous cell carcinomas and a few adenomas and adenocarcinomas of the larynx, trachea and lungs. These were morpholoigcally similar to neoplasms found after B(a)P and Fe2O3 treatment. B(a)P, combined with C or Al2O3, induced mainly laryngeal and tracheal papillomas. B(a)P- and C-treated hamsters also showed a few lung adenocarcinomas.

Adenocarcinoma↗
PubMed1983

The retention mechanics of LTI carbon, carbon-coated aluminum oxide, and uncoated aluminum oxide dental implants.

The in vitro mechanical behavior of identical geometry LTI carbon, carbon-coated aluminum oxide, and uncoated aluminum oxide blade-type dental implants has been evaluated using rosette type strain gauges and a LVDT system. The implants served as a distal abutment for a three-unit fixed prosthesis and functioned for a period of 2 years in female baboons. The comparison of the LTI carbon implants to the carbon-coated aluminum oxide implants allowed for a study of the effect of implant elastic modulus on the mechanical behavior, while the comparison of the carbon-coated and uncoated aluminum oxide implants allowed for a study of the effect of chemical composition at the tissue-implant interface. The results of the mechanical testing indicate that the implant displacement response of the LTI carbon implants was greater than that of the carbon-coated and uncoated aluminum oxide implants. Little difference in displacement response was observed for the carbon-coated and uncoated aluminum oxide implants. No clear trend in the strain response of the buccal mandibular bone was observed for the three implant systems. The greatest differences in strain response, however, was observed between the uncoated aluminum oxide implants and the LTI carbon and carbon-coated aluminum oxide implants.

Aluminum Oxide↗
PubMed1983

Quantitative histologic evaluation of LTI carbon, carbon-coated aluminum oxide and uncoated aluminum oxide dental implants.

The response of mandibular bone to identical geometry LTI carbon, carbon-coated aluminum oxide, and uncoated aluminum oxide blade-type dental implants in baboons for 2 years was evaluated using histologic, microradiographic, and scanning electron microscopic methods. In addition, a quantitative histologic analysis was performed identifying the type, amount, and distribution of tissue surrounding the dental implant systems. This is the final phase of a study investigating the effect of implant elastic modulus and implant surface chemical composition on the performance of dental implants. Previous studies have utilized clinical and radiographic evaluations, postretrieval mechanical testing, and finite element stress analysis to evaluate the dental implant performance. The results of the histologic study revealed a direct implant-bone interface with no intervening soft tissue in 16 of the 21 implants (76%). A fibrous tissue interface was observed in 5 of 21 implants (24%). Quantitative histologic results for the implants with a direct implant-bone interface showed statistically larger crestal cortical plates (p less than 0.05) and greater area fraction crestal cancellous bone (p less than 0.05) in the LTI carbon implant compared to the carbon-coated and uncoated aluminum oxide implants. The carbon-coated and uncoated aluminum oxide implants demonstrated statistically greater area fraction cancellous bone at the inferior region of the implant (p less than 0.05) and thinned and reduced crestal cortical plates when compared to the LTI carbon implants. The results indicate that significant stress shielding of the crestal bone had occurred with the rigid carbon-coated and uncoated aluminum oxide implants when compared to the LTI carbon implants which had a material elastic modulus similar to cortical bone. Based upon the histologic results, it appears that the LTI carbon implants with the direct implant-bone interface exhibited a greater potential for long-term successful performance compared to the aluminum oxide substrate implants.

Aluminum↗
PubMed2001

Proton binding by hydrous ferric oxide and aluminum oxide surfaces interpreted using fully optimized continuous pKa spectra.

A modified regularized least squares pKa spectrum approach is proposed to determine proton stability constants and concentrations for binding sites on hydrous ferric oxide (HFO) and aluminum oxide surfaces. Acid-base titration data are fit to a continuous binding site model for the system represented as a pKa spectrum. The modified parameter fitting method optimizes simultaneously for both smoothness of the pKa spectrum and goodness-of-fit, whereas other methods optimize for goodness-of-fit given a fixed smoothness factor. The modified method is tested with aluminum oxide and recovers values consistent with theoretical values. The regularized pKa spectrum method optimized for smoothness is applied to prepared samples of two types of HFO. The prepared HFO samples differ only in the total iron concentration of the parent solution. The resultant pKa distributions are compared to proton binding constants from MUSIC model results for crystalline iron oxides. The types of binding sites in the HFO sample are consistent with theoretical binding site stability constants for crystalline iron oxides. Overall, the prepared HFO samples have binding constants most consistent with values for lepidocrocite and goethite.

Aluminum Oxide↗
PubMed1997

Benzo[a]pyrene coated ferric oxide and aluminum oxide particles: uptake, metabolism and DNA binding in hamster pulmonary alveolar macrophages and tracheal epithelial cells in vitro.

Ferric oxide (Fe2O3) and aluminum oxide (Al2O3) particles are widely encountered in occupational settings. Benzo[a]pyrene (B[a]P), a well-characterized environmental carcinogen, is frequently adsorbed onto particles. It has been shown that B[a]P-coated Fe2O3 particles (B[a]P-Fe2O3) significantly increased lung tumors in the hamster in contrast to B[a]P-coated Al2O3 (B[a]P-Al2O3) or B[a]P alone. In order to determine the genotoxic effects of these particles on the metabolism of B[a]P, pulmonary alveolar macrophages (AM) from male Syrian golden hamsters were incubated with 5 microg (19.8 nmol) B[a]P-coated respirable size (99% < 5 microm) Fe2O3 and Al2O3 particles with loads from 0.5 to 2.0 mg. Intracellular uptake of B[a]P by AM at 24 h was higher with B[a]P-Fe2O3 than that of B[a]P alone (P < 0.05) or B[a]P-Al2O3 (P < 0.05). Total B[a]P metabolism was significantly greater in AM exposed to B[a]P-coated Fe2O3 at 1.0 and 1.5 mg than in the AM exposed to B[a]p-al2O3 (0.5, 1.0 and 1.5 mg) (P < 0.05) or B[a]P alone (P < 0.05). Similar significant differences for Fe2O3 relative to Al2O3 and B[a]P alone were also apparent for total dihydrodiols, quinones and phenolic metabolites. Co-administration of 5 microg alpha-naphthoflavone (alpha-NF, an inhibitor of cytochrome P-4501A1 and P-4501A2) and 10(-3) M cyclohexene oxide (CO, an inhibitor of epoxide hydrolase) significantly reduced B[a]P metabolism in B[a]P-Fe2O3 (P < 0.05) and B[a]P-Al2O3 (P < 0.05) treated groups relative to B[a]P alone. AM were co-cultured with hamster tracheal epithelial cells (HTE) and treated as described above for metabolism studies to assess the DNA binding of B[a]P metabolites in the target cells, using 32P-postlabeling techniques. Two adducts were observed that had chromatographic behavior similar to 7R,8S,9S-trihydroxy-10R-(N2-deoxyguanosyl-3'-phosphate)-7,8,9,10-t etrahydrobenzo[a]pyrene [(+)-anti-BPDE-dG, adduct 1, major adduct representing 70-80% of total adducts] and 7S,8R,9R-trihydroxy-10S-(N2-deoxyguanosyl-3'-phosphate)-7,8,9,10-t etrahydrobenzo[a]pyrene [(-)-anti-BPDE-dG, adduct 2, representing 20-30% of total adducts]. B[a]P-Fe2O3 treatment enhanced the levels of the two B[a]P-DNA adducts in the HTE compared with B[a]P-Al2O3 (P < 0.05) or B[a]P alone. The inhibitors alphaNF and CO significantly reduced total adduct levels in the HTE (P < 0.05) in the B[a]P and B[a]P-Fe2O3 treatments as well as adduct 1 and adduct 2 levels. Our data suggest that the cocarcinogenic effect of B[a]P-Fe2O3 relative to B[a]P-coated Al2O3 can be due to: (i) the enhancement of B[a]P metabolism in AM by Fe2O3 associated with the increased uptake of B[a]P; and (ii) augmentation of DNA adduct formation in epithelial cells.

Aluminum Oxide↗
PubMed2001

Mismatched wear couple zirconium oxide and aluminum oxide in total hip arthroplasty.

A patient complained about a squeaking noise in his total hip arthroplasty. Clinical evaluation revealed good function, and there were no signs of loosening on the radiograph. Physiotherapy did not alter this phenomenon, and ultimately a revision was performed 42 months after the first surgery. The analysis of the retrievals revealed that a zirconium oxide ceramic head had been paired with a monolithic alumina ceramic cup. The cup showed large deviations from an ideal sphere but minor wear signs. The head exhibited heavy local damage in the articulation zone. This damage might have been caused by the observed unsatisfactory fit between cup and ball, resulting in high stress concentrations and increased wear of the zirconium head. The characteristics of the zirconium and aluminum ceramics pairing might have worsened the process. The combination of implants used in this retrieved wear couple was never approved. To prevent such problems, components of different manufacturers should never be mixed and matched unless explicitly stated.

Aluminum Oxide↗
PubMed2005

Vanadium oxides on aluminum oxide supports. 1. Surface termination and reducibility of vanadia films on alpha-Al2O3(0001).

Using density functional theory and statistical thermodynamics, we obtained the phase diagram of thin VnOm films of varying thickness (approximately 2-6 A, 1-6 vanadium layers) supported on alpha-Al2O3(0001). Depending on the temperature, oxygen pressure, and vanadium concentration, films with different thickness and termination may form. In ultrahigh vacuum (UHV), at room temperature and for low vanadium concentrations, an ultrathin (1 x 1) O=V-terminated film is most stable. As more vanadium is supplied, the thickest possible films form. Their structures and terminations correspond to previous findings for the (0001) surface of bulk V2O3 [Kresse et al., Surf. Sci. 2004, 555, 118]. The presence of surface vanadyl (O=V) groups is a prevalent feature. They are stable up to at least 800 K in UHV. Vanadyl oxygen atoms induce a V(2p) core-level shift of about 2 eV on the surface V atoms. The reducibility of the supported films is characterized by the energy of oxygen defect formation. For the stable structures, the results vary between 4.11 and 3.59 eV per 1/2O2. In contrast, oxygen removal from the V2O5(001) surface is much easier (1.93 eV). This provides a possible explanation for the lower catalytic activity of vanadium oxides supported on alumina compared to that of crystalline vanadia particles.

Journal Article↗
PubMed2005

Vanadium oxides on aluminum oxide supports. 2. Structure, vibrational properties, and reducibility of V2O5 clusters on alpha-Al2O3(0001).

The structure, stability, and vibrational properties of isolated V2O5 clusters on the Al2O3(0001) surface have been studied by density functional theory and statistical thermodynamics. The most stable structure does not possess vanadyl oxygen atoms. The positions of the oxygen atoms are in registry with those of the alumina support, and both vanadium atoms occupy octahedral sites. Another structure with one vanadyl oxygen atom is only 0.12 eV less stable. Infrared spectra are calculated for the two structures. The highest frequency at 922 cm(-1) belongs to a V-O stretch in the V-O-Al interface bonds, which supports the assignment of such a mode to the band observed around 941 cm(-1) for vanadia particles on alumina. Removal of a bridging oxygen atom from the most stable cluster at the V-O-Al interface bond costs 2.79 eV. Removal of a (vanadyl) oxygen atom from a thin vanadia film on alpha-Al2O3 costs 1.3 eV more, but removal from a V2O5(001) single-crystal surface costs 0.9 eV less. Similar to the V2O5(001) surface, the facile reduction is due to substantial structure relaxations that involve formation of an additional V-O-V bond and yield a pair of V(IV)(d1) sites instead of a V(III)(d2)/V(V)(d0) pair.

Journal Article↗
PubMed2006

Cultivation of hepatoma cell line HepG2 on nanoporous aluminum oxide membranes.

Nanoporous aluminum oxide membranes were prepared by anodic oxidation of aluminum for application as novel cell culture substrates. Self-supporting as well as mechanically stabilized nanoporous membranes were produced from aluminum plates and micro-imprinted aluminum foils, respectively. Membranes of two different pore sizes (70 and 260 nm) were selected to investigate cellular interactions with such nanoporous substrates using cells of hepatoma cell line HepG2. The membranes express excellent cell-growth conditions. As shown by scanning electron microscopy investigations, the cells could easily adhere to the membranes and proliferate during a 4 day cell culture period. The cells exhibit normal morphology and were able to penetrate into pores with a diameter of 260 nm by small extensions (filopodia). On mechanically stabilized aluminum oxide membranes it was observed that the cells even adhere to the walls of the small cavities. It was demonstrated experimentally that the nanoporous aluminum oxide membranes are well suited as substrates in cell culture model systems for metabolic, pharmacological/toxicological research, tissue engineering and studies on pathogens as well as bioartificial liver systems.

Carcinoma, Hepatocellular↗
PubMed1993

Fractal dimension analysis of aluminum oxide particle for sandblasting dental use.

Aluminum oxide particles are commonly used as a sandblasting media, particularly in dentistry, for multiple purposes including divesting the casting investment materials and increasing effective surface area for enhancing the mechanical retention strengths of succeedingly applied fired porcelain or luting cements. Usually fine aluminum oxide particles are recycled within the sandblasting machine. Ceramics such as aluminum oxides are brittle, therefore, some portions of recycling aluminum oxide particles might be brittle fractured. If fractured sandblasting particles are involved in the recycling media, it might result in irregularity metallic materials surface as well as the recycling sandblasting media itself be contaminated. Hence, it is necessary from both clinical and practical reasons to monitor the particle conditions in terms of size/shape and effectiveness of sandblasting, so that sandblasting dental prostheses can be fabricated in optimum and acceptable conditions. In the present study, the effect of recycling aluminum oxide particles on the surface texture of metallic materials was evaluated by Fractal Dimension Analysis (FDA). Every week the alumina powder was sampled and analyzed for weight fraction and contaminants. Surface texture of sandblasted standard samples was also characterized by FDA. Results indicate very little change in particle size, while the fractal dimension increased. Fractal dimension analysis showed that the aluminum oxide particle as a sandblasting media should be replaced after 30 or 40 min of total accumulated operation time.

Air Pressure↗