Magnesium-enriched hydroxyapatite at immediate implants: a histomorphometric study in dogs

Aim To evaluate the influence of magnesium-enriched hydroxyapatite (MHA) (SintLife (R)) on bone contour preservation and osseointegration at implants placed immediately into extraction sockets. Material and methods In the mandibular pre-molar region, implants were installed immediately into extraction sockets of six Labrador dogs. MHA was placed at test sites, while the control sites did not receive augmentation materials. Implants were intended to heal in a submerged mode. After 4 months of healing, the animals were sacrificed, and ground sections were obtained for histomorphometric evaluation. Results After 4 months of healing, one control implant was not integrated leaving n=5 test and control implants for evaluation. Both at the test and the control sites, bone resorption occurred. While the most coronal bone-to-implant contact was similar between test and control sites, the alveolar bony crest outline was maintained to a higher degree at the buccal aspect of the test sites (loss: 0.7 mm) compared with the control sites (loss: 1.2 mm), even though this difference did not reach statistical significance. Conclusions The use of MHA to fill the defect around implants placed into the alveolus immediately after tooth extraction did not contribute significantly to the maintenance of the contours of the buccal alveolar bone crest. To cite this article:Caneva M, Botticelli D, Stellini E, Souza SLS, Salata LA, Lang NP. Magnesium-enriched hydroxyapatite at immediate implants: a histomorphometric study in dogs.Clin. Oral Impl. Res. 22, 2011; 512-517doi: 10.1111/j.1600-0501.2010.02040.x.

THE COMPTON-THICK SEYFERT 2 NUCLEUS OF NGC 3281: TORUS CONSTRAINTS FROM THE 9.7 mu m SILICATE ABSORPTION

We present mid-infrared (mid-IR) spectra of the Compton-thick Seyfert 2 galaxy NGC 3281, obtained with the Thermal-Region Camera Spectrograph at the Gemini-South telescope. The spectra present a very deep silicate absorption at 9.7 mu m, and [S IV] 10.5 mu m and [Ne II] 12.7 mu m ionic lines, but no evidence of polycyclic aromatic hydrocarbon emission. We find that the nuclear optical extinction is in the range 24 mag <= A(V) <= 83 mag. A temperature T = 300 K was found for the blackbody dust continuum component of the unresolved 65 pc nucleus and the region at 130 pc SE, while the region at 130 pc NW reveals a colder temperature (200 K). We describe the nuclear spectrum of NGC 3281 using a clumpy torus model that suggests that the nucleus of this galaxy hosts a dusty toroidal structure. According to this model, the ratio between the inner and outer radius of the torus in NGC 3281 is R(0)/R(d) = 20, with 14 clouds in the equatorial radius with optical depth of tau(V) = 40 mag. We would be looking in the direction of the torus equatorial radius (i = 60 degrees), which has outer radius of R(0) similar to 11 pc. The column density is N(H) approximate to 1.2 x 10(24) cm(-2) and the iron K alpha equivalent width (approximate to 0.5-1.2 keV) is used to check the torus geometry. Our findings indicate that the X-ray absorbing column density, which classifies NGC 3281 as a Compton-thick source, may also be responsible for the absorption at 9.7 mu m providing strong evidence that the silicate dust responsible for this absorption can be located in the active galactic nucleus torus.

The Determination of Total Hydrogen, Carbon, Nitrogen and Sulfur in Silicates, Silicate Rocks, Soils and Sediments

Determinations of the volatile elements carbon, hydrogen, sulfur and nitrogen in many geological RM, performed with the LECO CHN and SC analysers, are presented. The method allowed the determination of S in concentrations from a few % m/m to 0.001% m/m or less, of C from % m/m to 0.01% m/m and of H from % m/m to 0.004% m/m. Accuracy was usually better than the XRF method (for S). All obtained values passed the Sutarno-Steger test, which establishes that vertical bar(mean(analysed) - mean(certified))vertical bar/ S(certified) < 2, for the cases with an appropriate number of determinations (n > 10 for each element). It was possible to perform routine determination of C, H and S with the instrumentation, coupled with the determination of major and minor elements in geological materials. Determination of nitrogen could also be performed on an exploratory basis, with improvements in the method dependent on the future availability of more reference materials with reliable composition of this element.

Tryptophan photooxidation promoted by new hybrid materials prepared by condensation of naphthalene imides with silicate by the sol-gel process

Three novel hybrid organic/inorganic materials were synthesized from 4-substituted (NO(2), Br, H) 1,8-naphthalene imide-N-propyltriethoxysilane by the sol-gel process. These materials were obtained as a xerogel and partially characterized. The ability to photosensitize the oxidation and degradation of tryptophan indole ring by these materials was studied through photophysical and photochemical techniques. Although the derivatives containing Br and NO(2) as substituent do not cause efficient tryptophan photodamage, the hybrid material obtained from 1,8-naphthalic anhydride is very efficient to promote tryptophan photooxidation. By using laser flash photolysis it was possible to verify the presence of naphthalene imide transient radical species. The presence of oxygen causes an increase of the yield of radical formation. These results suggest that the mechanism of photodegradation of tryptophan occurs by type I, i.e. the transient radical (TrpH(center dot+)) formed by the direct reaction of the triplet state of the naphthalene imide moiety with tryptophan. Thus a inorganic-organic hybrid material that can be used to promote the oxidation of biomolecules was obtained. (C) 2009 Elsevier B.V. All rights reserved.

Ethanol steam reforming for production of hydrogen on magnesium aluminate-supported cobalt catalysts promoted by noble metals

The performance of noble metal (Pt, Ru, Ir)-promoted Co/MgAl(2)O(4) catalysts for the steam reforming of ethanol was investigated. The catalysts were characterized by energy-dispersive X-ray spectroscopy, Xray diffraction, UV-vis diffuse reflectance spectroscopy, temperature-programmed reduction, temperature-programmed oxidation and X-ray absorption near edge structure (XANES). The results showed that the formation of inactive cobalt aluminate was suppressed by the presence of a MgAl(2)O(4) spinel phase. The effects of the noble metals included a marked lowering of the reduction temperatures of the cobalt surface species interacting with the support. It was seen that the addition of noble metal stabilized the Co sites in the reduced state throughout the reaction. Catalytic performance was enhanced in the promoted catalysts, particularly CoRu/MgAl(2)O(4), which showed the highest selectivity for H(2) production. (C) 2009 Elsevier B.V. All rights reserved.

Temperature and common-ion effect on magnesium oxide (MgO) hydration

MgO based refractory castables draw wide technological interest because they have the versatility and installation advantages of monolithic refractories with intrinsic MgO properties, such as high refractoriness and resistance to basic slag corrosion. Nevertheless, MgO easily reacts with water to produce Mg(OH)(2), which is followed by a large volumetric expansion, limiting its application in refractory castables. In order to develop solutions to minimize this effect, a better understanding of the main variables involved in this reaction is required. In this work, the influence of temperature, as well as the impact of the chemical equilibrium shifting (known as the common-ion effect), on MgO hydration was evaluated. Ionic conductivity measurements at different temperatures showed that the MgO hydration reaction is accelerated with increasing temperature. Additionally, different compounds were added to evaluate their influence on the reaction rate. Among them, CaCl(2) delayed the reaction, whereas KOH showed an opposite behavior. MgCl(2) and MgSO(4) presented similar results and two other distinct effects, reaction delay and acceleration, which depended on their concentration in the suspensions. The results were evaluated by considering the kinetics and the thermodynamics of the reaction, and the mechanical damages in the samples that was caused by the hydration reaction. (C) 2009 Elsevier Ltd and Techna Group S.r.l. All rights reserved.