Effectiveness of a toothpaste with low fluoride content combined with trimetaphosphate on dental biofilm and enamel demineralization in situ

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Fluoride gel supplemented with sodium hexametaphosphate reduces enamel erosive wear in situ

This study evaluated the effect of fluoride gels, supplemented or not with sodium hexametaphosphate (HMP), on enamel erosive wear in situ. Twelve healthy volunteers wore palatal appliances containing four bovine enamel discs. Subjects were randomly allocated into four experimental phases (double-blind, crossover protocol) according to the gels: Placebo (no fluoride or HMP), 1% NaF, 2% NaF, and 1% NaF+9% HMP. Enamel discs were selected after polishing and surface hardness analysis, and treated only once with the respective gels prior to each experimental phase. Erosion (ERO) was performed by extra-oral immersion of the appliance in 0.05M citric acid, pH 3.2 (four times/day, five minutes each, 5 days). Additional abrasion (ERO+ABR) was produced on only two discs by toothbrushing with fluoridated dentifrice after ERO (four times/day, 30s, 5 days). The specimens were submitted to profilometry and hardness analysis. The results were analyzed by two-way ANOVA and the Student-Newman-Keuls test (p<0.05). The 1% NaF+9% HMP gel promoted significantly lower enamel wear for ERO compared to the other groups, being statistically lower than 1% NaF and Placebo for ERO+ABR. Similarly, the lowest values of integrated lesion area were found for 1% NaF+9% HMP and 2% NaF, respectively, for ERO and ERO+ABR. The addition of HMP to the 1% NaF gel promoted greater protective effect against ERO and ERO+ABR compared to the 1% NaF gel, achieving similar protective levels to those seen for the 2% NaF gel. Gel containing 1% NaF+9% HMP showed a high anti-erosive potential, being a safer alternative when compared to a conventional 2% NaF gel.

In vitro effect of low-fluoride toothpastes containing sodium trimetaphosphate on enamel erosion

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Effects of pH and fluoride concentration of dentifrices on fluoride levels in saliva, biofilm, and biofilm fluid in vivo

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

Fluoride concentrations of milk, infant formulae, and soy-based products commercially available in Brazil

To assess the fluoride (F) content in commercially available milk formulae in Brazil and to estimate the F intake in children from this source in the first year of life. Samples of cow's milk (n = 51), infant formulae (n = 15), powdered milk (n = 13), and soy-based products (n = 4) purchased in Araçatuba (Brazil) had their F content measured using an ion-specific electrode, after hexamethyldisiloxane-facilitated diffusion. Powdered milk and infant formulae were reconstituted with deionized water, while ready-to-drink products were analyzed without any dilution. Using average infant body masses and suggested volumes of formula consumption for infants 1-12 months of age, possible F ingestion per body mass was estimated. Data were analyzed by descriptive analysis. Mean F content ranged from 0.02 to 2.52 mg/L in all samples. None of the cow's milk provided F intake higher than 0.07 mg/kg. However, two infant formulae, one powdered milk, and one soy-milk led to a daily F intake above the suggested threshold for fluorosis when reconstituted with deionized water. Assuming reconstitution of products with tap water at 0.7 ppm F, two infant formulae, five powdered milk, and four soymilks led to daily F intake ranging from 0.108 to 0.851 mg/kg. The results suggest that the consumption of some brands of infant formulae, powdered milk, and soy-based milk in the first year of age could increase the risk of dental fluorosis, reinforcing the need for periodic surveillance of the F content of foods and beverages typically consumed by young children.

A quantitative analysis of the polarization reversal in the 73 mol % vinylidene fluoride-27 mol % trifluorethylene copolymer

We show that a time-dependent, effective-medium approximation essentially explains the time behavior of the polarization reversals obtained in doped copolymers of vinylidene fluoride and trifluorethylene at 60°C by Ieda, Fukada, and Wada [J. Appl. Phys. 64, 2026 (1988)], who attributed the observed effects to charge accumulation at the boundaries of the permanently polarized crystallites. Moreover, the results seem to indicate that some hindrance (perhaps of mechanical origin) opposes the action of the switching electric field.

Photocatalytic decomposition of rhodamine-b using scandium and silver-modified TiO2 powders

Semiconductor-mediated photocatalytic oxidation is an interesting method for water decontamination and a specially modified TiO2 is said to be a promising material. This study verified that the synthesis of 1wt%Ag modified-Sc0.01Ti0.99O1.995 powder samples prepared by Polymeric Precursor Method is capable of forming a mixture of anatase-rutile phase with high photocatalytic performance. This kind of material is found to have a lower bandgap compared to the TiO2-anatase commercial powders, which can be associated to an innovative hybrid modification. The simultaneous insertion of scandium in order to generate a p-type semiconductor and a metallic silver nanophase acting as an electron trapper demonstrated being capable of enhancing the degradation of rhodamine B compared to the commercial TiO2. In spite of the different thermal treatments or phase amounts, the hybrid modified powder samples showed higher photocatalytic activity than the commercial ones.

Preparation and characterization of PVDF/CaCO3 composites

The contribution of new materials, involving composites and blends, has been reaching the most varied fields of science, as much of the scientific as technological point of view. This is due to the man's needs in applications, especially in medicine areas. Thus, this work shows the preparation and characterization of poly(vinylidene fluoride) (PVDF) and calcium carbonate (CaCO3) Composite films in order to analyse the incorporation of CaCO3 in PVDF for future application in bony restoration and bony filling. The films were prepared by casting method, where the PVDF pellet shape was dissolved in dimethylacetamide (DMA) and in a separate container CaCO3/DMA emulsion was also made. Soon afterwards they were mixed in several proportions 100/00, 95/05, 85/15, 70/30 in weight and left to dry in greenhouse. Homogeneous and flexible films were obtained and structurally characterized by attenuated total reflection infrared spectroscopy (FT-IR/ATR), thermal analyses (DSC, TGA), X-ray diffractometry, optical and scanning electron microscopies. The results showed that the material was a composite with good thermal stability until around 400 degrees C, the crystallinity of PVDF was non-polar alpha-phase and the obtained films were porous, being these filled with CaCO3. (c) 2006 Elsevier B.V. All rights reserved.

Thermomechanical characterization of PVDF and P(VDF-TrFE) blends containing corn starch and natural rubber

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

Tailoring the Structural Properties of PVDF and P(VDF-TrFE) by Using Natural Polymers as Additives

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

Structural and electrochemical properties of LiCoO2 prepared by combustion synthesis

LiCoO2 powders were prepared by combustion synthesis, using metallic nitrates as the oxidant and metal sources and urea as fuel. A small amount of the LiCoO2 phase was obtained directly from the combustion reaction, however, a heat treatment was necessary for the phase crystallization. The heat treatment was performed at the temperature range from 400 up to 700 degreesC for 12 h. The powders were characterized by X-ray diffraction (XRD), X ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and specific surface area values were obtained by BET isotherms. Composite electrodes were prepared using a mixture of LiCoO2, carbon black and poly(vinylidene fluoride) (PVDF) in the 85:10:5% w/w ratio. The electrochemical behavior of these composites was evaluated in ethylene carbonate/dimethylcarbonate solution, using lithium perchlorate as supporting electrolyte. Cyclic voltammograms showed one reversible redox process at 4.0/3.85 V and one irreversible redox process at 3.3 V for the LiCoO2 obtained after a post-heat treatment at 400 and 500 degreesC.Raman spectroscopy showed the possible presence of LiCoO2 with cubic structure for the material obtained at 400 and 500 degreesC. This result is in agreement with X-ray data with structural refinement for the LiCoO2 powders obtained at different temperatures using the Rietveld method. Data from this method showed the coexistence of cubic LiCoO2 (spinel) and rhombohedral (layered) structures when LiCoO2 was obtained at lower temperatures (400 and 500 degreesC). The single rhombohedral structure for LiCoO2 was obtained after post-heat treatment at 600 degreesC. The maximum energy capacity in the first discharge was 136 mA g(-1) for the composite electrode based on LiCoO2 obtained after heat treatment at 700 degreesC. (C) 2002 Elsevier B.V. B.V. All rights reserved.

Selective activity of butyrylcholinesterase in serum by a chemiluminescent assay

In a previous study, we showed that purified commercial esterase activity can be detected in a chemiluminescent assay based on the hydrolysis of 2-methyl-1-propenylbenzoate (MPB) to 2-methyl-1-propenol, which is subsequently oxidized by the horseradish peroxidase (HRP)-H2O2 system. The purpose of this study was to verify the applicability of this assay to human serum. The existence of an esterase activity capable of hydrolysing MPB is indicated by the fact that the MPB-scruin-HRP-H2O2 System consumes oxygen and emits light. Both signals were abolished by prior serum heat inactivation and were preserved when serum was stored at less than or equal to4 degreesC. Addition of aliesterase inhibitors, such as fluoride ion and trichlorfon or the cholinesterase inhibitor eserine, totally prevents light emission. The butyrylcholinesterase-specific substrate benzoylcholine causes a delay in both O-2 uptake and light emission, while the specific acetylcholinesterase substrate, acetyl-beta -methylcholine, had practically no effect. Purified butyrylcholinesterase, but not acetylcholinesterase, triggered light emission. The finding that butyryleholinesterase is responsible for the hydrolysis of MPB in serum should serve as the basis for the development of a specific chemiluminescent assay for this enzyme. Copyright (C) 2001 John Wiley & Sons, Ltd.

Effects of calcium gluconate and PMSF in the treatment of acute intoxication of chicken by TOCP

To examine the efficacy of calcium gluconate (two doses of Ca-Glu 5 mg/kg i.v.) to alleviate the injurious effects of organophosphorus induced delayed neuropathy (OPIDN) in the presence or absence of phenylmethanesulfonyl fluoride (PMSF go mg/kg i.m.), 14 groups of four isabrown hens were used. To measure the lymphocyte neuropathy target esterase (LNTE)activity, groups receiving just distilled water (control), groups receiving just Tri-orto-cresyl phosphate (TOCP; 500 mg/kg p.o.) (Positive control), and other groups receiving TOCP and Ca-Glu or PMSF simultaneously or 12 hours later following intoxication by TOCP were used. They were sacrificed 12 and 24 hours after the administration of TOCP. To observe a 28-day time course of neurotoxicity scores and calcium plasma concentration, five groups were used. Regarding free Ca(2+)in the plasma, the positive control produced a characteristic profile time course up and down (luring 28 days, and some hens with maximum score of neurotoxicity in 28 days. The treatment, which prevented greater oscillation in free Ca(2+) in the plasma, presented a decrease in OPIDN in relation to the positive control. Twelve hours after the administration of TOCP, LNTE was 70-80% inhibited when compared with control, whereas the first decrease in the free Ca(2+) in the plasma was significantly different from the control only 24 hours after the administration of TOCP. In summary, the sooner the Ca-Glu is started, the less severe the neuropathy effects.

Synthesis, characterization and thermal studies of solid state 4-methylbenzylidenepyruvate of some trivalent metal ions

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

Conhecimento dos médicos pediatras e odontopediatras de Bauru e Marília a respeito de flúor

A proposta deste trabalho foi verificar o conhecimento dos médicos pediatras e odontopediatras, a respeito dos compostos fluoretados. Para tanto, foram visitados 91 médicos pediatras e 72 odontopediatras dos municípios de Bauru e Marília, que ao concordarem em participar da pesquisa receberam um questionário com 22 questões. O preenchimento e a devolução foram imediatos. Os dados obtidos foram analisados por meio de estatística descritiva, utilizando freqüências absolutas e relativas, representadas através de tabelas. Mediante a análise dos questionários, verificou-se que alguns polivitamínicos que contêm flúor são usualmente prescritos pelos médicos pediatras, ao passo que os géis, vernizes e soluções para bochecho são bastante empregados pelos odontopediatras. Não foi estabelecida relação entre o conhecimento e tempo de formado, a idade do profissional, a universidade de origem, a cidade em que trabalha e a área de atuação (particular, rede pública ou em ambos) desses profissionais. Os resultados obtidos sugerem que o conhecimento dos médicos pediatras e odontopediatras, das cidades de Bauru e de Marília, a respeito da presença de flúor em várias fontes de ingestão se mostrou insuficiente e, em algumas situações, preocupante, com relação à prevenção de fluorose dentária.