Effect of 0.4% stannous fluoride gel on Streptococci mutans in relation to elastomeric rings and steel ligatures in orthodontic patients

Background: Patients with fixed orthodontic appliances often experience an absolute increase in the number of Streptococci mutans colony-forming units (cfu). The aim of this investigation was to study the development of biofilm and S. mutans cfu in connection with stainless steel ligatures and elastomeric rings in orthodontic patients treated with and without 0.4% stannous fluoride gel (SFG). Material: Forty-seven patients were divided into 2 groups: those treated with 0.4% SFG for 4 minutes (experimental) and those without 0.4% SFG (control). In each patient, elastomeric rings were used for ligation on 1 side of the dental arch midline, and stainless steel ligatures were used on the opposite side. Saliva samples were collected before and after appliance placement. At 15 and 30 days after appliance placement, biofilm samples from the stainless steel ligatures and the elastomeric rings were collected and subjected to microbiologic procedures and scanning electron microscopy (SEM) analysis. Results: The numbers of S. mutans cfu in the saliva and biofilm were not statistically different between the teeth fitted with elastomeric rings and stainless steel ligatures, or between the experimental and control groups. SEM analysis showed biofilm formation on both ligature ties. Conclusions: Topical application of 0.4% SFG in orthodontic patients with elastomeric rings or stainless steel ligatures does not cause a significant decrease in S. mutans cfu in the saliva and biofilm. Copyright © 2005 by the American Association of Orthodontists.

Improvement of the chemical resistance of zirconium fluoride glasses coated with a Tiron (R) modified tin oxide layer prepared by the sol-gel process

In order to improve the chemical resistance of zirconium fluoride glass a protective transparent SnO2 layer was deposited by the solgel dip-coating process in the presence of Tiron (R) as particle surface modifier agent. After water immersion for different periods of time, both coated and non-coated fluoride glasses were analyzed by scanning electron microscopy, mass loss evaluation, infrared spectroscopy and X-ray photoelectron spectroscopy. In contrast to the effects occurring for non-coated glass, where the surface undergoes a rapid selective dissolution of the most soluble species, the results for the SnO2-coated glass showed that the filling of the film nanopores by dissolved glass material results in a hermetic barrier protecting the glass surface. The selective glass dissolution was confirmed by liquid chromatography measurements of the etching solution after each exposure time. (c) 2006 Elsevier B.V. All rights reserved.

Morphological evolution of tin oxide nanobelts after phase transition

This article reports a study of the thermal stability and morphological changes in tin oxide nanobelts grown in the orthorhombic SnO phase. The nanobelts were heat-treated in a differential scanning calorimetry (DSC) furnace at 800 degrees C for I It in argon, oxygen, or synthetic air atmospheres. The samples were then characterized by DSC, X-ray diffraction (XRD), high resolution transmission electron microscopy (HRTEM), and high resolution field emission scanning electron microscopy (FE-SEM). The results confirmed that the orthorhombic SnO phase is thermodynamically unstable, causing the belts to transform into the SnO2 phase when heat-treated. During the phase transition, if oxygen is available in the furnace atmosphere, nanofibers grow at the edge of nanobelts at about 50 degrees of the belts' growth direction, while particles grow on the belt surface in the absence of oxygen. Although the decomposition process reduces the nanobelt cell volume by 22%, most belts remain monocrystalline after the heat treatment. The results confirm that phase transition is a decomposition process, which explains the morphological changes in the belts based on metallic tin generated in the process.

Effect of tartrate content on aging and deposition condition of copper-tin electrodeposits from a non-cyanide acid bath

The effect of the presence of tartrate additive on the chemical stability of a Cu-Sn acid bath was evaluated. It was observed that this additive hinders decomposition of the Cu/Sn deposition bath with storage time, since the decrease in electrochemical efficiency was attenuated. In addition, it was observed that optimal galvanostatic deposition with or without tartrate occurs at approximately 11 mA cm(-2). However, in the presence of tartrate the deposition charge was lower, leading to lower energy consumption. SEM analysis showed that the tartrate added to the plating bath caused a marked change in the morphology of the Cu/Sn films obtained gal vanostatic ally. (C) 2002 Elsevier B.V. B.V. All rights reserved.

Influence of rare earth doping on the structural and catalytic properties of nanostructured tin oxide

Nanoparticles of tin oxide, doped with Ce and Y, were prepared using the polymeric precursor method. The structural variations of the tin oxide nanoparticles were characterized by means of nitrogen physisorption, carbon dioxide chemisorption, X-ray diffraction, and X-ray photoelectron spectroscopy. The synthesized samples, undoped and doped with the rare earths, were used to promote the ethanol steam reforming reaction. The SnO2-based nanoparticles were shown to be active catalysts for the ethanol steam reforming. The surface properties, such as surface area, basicity/base strength distribution, and catalytic activity/selectivity, were influenced by the rare earth doping of SnO2 and also by the annealing temperatures. Doping led to chemical and micro-structural variations at the surface of the SnO2 particles. Changes in the catalytic properties of the samples, such as selectivity toward ethylene, may be ascribed to different dopings and annealing temperatures.

The effect of Sb and Nb on the electrical conductivity of tin dioxide based ceramics

The electrical conductivity of Mn doped SnO2 systems prepared by an organic route (Pechini's method) has been investigated as a function of antimony and niobium concentration. The conductivity increases with the increase of both concentration ions, however, in a different manner. While the conductivity of niobium doped ceramics increases with the power of 1.6 for the entire range of concentrations studied (0.01-0.7 mol%), the conductivity of antimony doped ceramics increases with the power of 1.9 in the range 0.01-0.05 mol% of Sb; 3.7 in the range 0.05-0.30 mol% and 1.8 in the range 0.30-0.70 mol%. This behavior is attributed to the existence of two stable oxidation states for antimony: Sb3+ and Sb5+, while for niobium there is only one: Nb5+. The power of 3.7 for Sb would be related to the segregation of this ion on the grain boundary accompanied by an additional contribution coming from the substitution of Sn2+ by Sb3+ on the grain surface.

Effect of cerium (IV) ions on the anticorrosion properties of siloxane-poly(methyl methacrylate) based film applied on tin coated steel

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Electrochemical study of TEOS, TEOS/MPTS, MPTS/MMA and TEOS/MPTS/MMA films on tin coated steel in 3.5% NaCl solution

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Evaluation and Application of TS-FF-AAS System Using Ceramic Tube as Atomization Cell for Tin Determination in Canned Foods

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Stabilization of fluoroindate glasses by magnesium fluoride and other heavy metal fluorides

Their extended transparency in the IR makes them attractive for use as optical fibers for CO laser power delivery and optical amplification. This paper firstly describes the spectacular stabilizing effect of MgF2 on the binary system InF3-BaF2. The investigation of the InF3-BaF2-MgF2 system led to samples up to 5mm in thickness. Further optimization of this system was achieved by incorporation of limited amounts of other fluorides and resulted in increased resistence to devitrification. The second approach of this work was concerned to the investigation of the pseudo-ternary system InF3-GdF3-GaF3 at constant concentrations of ZnF2-SrF2-BaF2-NaF. Several compositions were studied in this system. The samples presented a better thermal stability when compared to other families of fluoride glasses. Therefore, these glasses seem to be very promising for the fabrication of special optical fibers. Thermal data are reported.

Sintering of tin oxide and its applications in electronics and processing of high purity optical glasses

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Growth kinetics of tin oxide nanocrystals in colloidal suspensions under hydrothermal conditions

Colloidal suspensions of tin oxide nanocrystals were synthesized at room temperature by the hydrolysis reaction of tin chloride (II), in an ethanolic solution. The coarsening kinetics of such nanocrystals was studied by submitting the as-prepared suspensions to hydrothermal treatments at temperatures of 100, 150 and 200 degrees C for periods between 60 and 12,000 min. Transmission electron microscopy (TEM) was used to characterize the samples (i.e. distribution of nanocrystal size, average particle radius and morphology). The results show that the usual Ostwald ripening coarsening mechanism does not fit well the experimental data, which is an indicative that this process is not significant for SnO2 nanocrystals, in the studied experimental conditions. The morphology evolution of the nanocrystals upon hydrothermal treatment indicates that growth by oriented attachment (OA) should be significant. A kinetic model that describes OA growth is successfully applied to fit the data. (c) 2006 Elsevier B.V. All rights reserved.

Comparison of metallic and ceramic tubes as atomization cells for tin determination by TS-FF-AAS

This work describes the development of an analytical procedure for on-line tin determination using thermospray flame furnace atomic absorption spectrometry (TS-FF-AAS). Two tubes were evaluated as atomization cells: a metallic tube (Ni-Cr, principal components composition: 73.95% Ni and 16.05% Cr) and a ceramic tube (99.8% Al2O3). The use of air as the carrier was made by employing a Rheodyne valve to inject the samples, allowing an analytical frequency of 90 h(-1) and avoiding sample dispersion. The carrier flow rate (air), sample volume injected, and acid concentration (HCl) were evaluated for the optimization of the TS-FF-AAS system. The sensitivity for 50 mL of analytical solution with TS-FF-AAS was 2 and 5 times higher (to metallic and ceramic tube, respectively) than using an acetylene-nitrous oxide flame with pneumatic aspiration (requiring a sample volume of approximately 20 times higher.

Sintering of tin oxide using zinc oxide as a densification aid

The physicochemical electronic characteristics of SnO2 render it useful in many technical applications, including ceramic varistors, stable electrodes used in electric glass-melting furnaces and electrometallurgy of aluminum, transparent windows and chemical sensors. The use of ZnO as a sintering aid was explored in this study to obtain SnO2 as a dense ceramic. Compacts were obtained by mechanical mixing of oxides, isostatic pressing at 210 MPa and sintering in situ inside a dilatometer at heating rates of 10degreesC/min. The grain size and microstructure were investigated by scanning and transmission electron microscopy (SEM/TEM). The phases and chemical composition were analyzed by energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD). The results indicated that ZnO acts as a densification aid for SnO2, improving its grain growth with additions of up to 2 mol%. ZnO forms a solid solution with SnO2 UP to 1 mol%, above which SnZnO3 precipitates in the grain boundary, potentially inhibiting shrinkage and grain growth. (C) 2004 Kluwer Academic Publishers