Evaluation of pH and Calcium Ion Release of Calcium Hydroxide Pastes Containing Different Substances

Introduction: The objective of this study was to evaluate the pH and calcium ion release of calcium hydroxide pastes associated with different substances. Methods: Forty acrylic teeth with simulated root canals were divided into 4 groups according to the substance associated to the calcium hydroxide paste: chlorhexidine (CHX) in 2 formulations (1% solution and 2% gel), Casearia sylvestris Sw extract, and propylene glycol (control). The teeth with pastes and sealed coronal accesses were immersed in 10 mL deionized water. After 10 minutes, 24 hours, 48 hours, and 7, 15, and 30 days, the teeth were removed to another container, and the liquid was analyzed. Calcium ion release was measured by atomic absorption spectrophotometry, and pH readings were made with a pH meter. Data were analyzed statistically by analysis of variance and Tukey test (alpha = 0.05). Results: Calcium analysis revealed significant differences (P < .05) for 1% CHX solution and 2% CHX gel at 10 minutes. After 24 hours, 2% CHX gel x Control and 2% CHX gel x 1% CHX solution differed significantly (P < .05). After 48 hours, there were significant differences (P < .05) for 2% CHX gel x Control and Extract x Control. No differences (P > .05) were observed among groups in the other periods. Regarding the pH, there were significant differences (P < .05) for 2% CHX gel x Control and 2% CHX gel x 1% CHX solution after 48 hours and for 2% CHX gel x Control after 15 days. In the other periods, no differences (P > .05) were observed among groups. Conclusions: All pastes behaved similarly in terms of pH and calcium ion release in the studied periods. (J Endod 2009;35:1274-1277)

Lead Deposition in Bovine Enamel during a pH-Cycling Regimen Simulating the Caries Process

Like fluoride, lead (Pb) accumulates on the enamel surface pre-eruptively, but it is not yet known whether it also deposits on enamel while dental caries is developing. This study evaluates Pb distribution in bovine enamel slabs submitted to a pH-cycling regimen simulating the caries process. The slabs were subjected to 8 cycles of de- and remineralizing conditions, and Pb (as acetate salt) was added to the de- and remineralized solutions at concentrations of 30 mu g/l (experimental group, E1) and 300 mu g/l (experimental group, E2). The control group (C) consisted of solutions to which Pb was not added. After the pH cycling, 100-mu m sections of the slabs were analyzed by polarizing microscopy, to observe the extent of caries-like lesions, and these sections were used for Pb estimation by Synchrotron radiation X-ray microfluorescence. Caries lesions were observed along all superficial enamel surfaces to an extent of 120 mu m. A Pb concentration gradient was observed in enamel, which decreased toward dentine. The highest Pb signals were observed for group E2, and the differences were statistically significant at enamel depths of 0 (C vs. E2; p = 0.029) and 50 mu m (C vs. E2 and E1 vs. E2; p = 0.029). In conclusion, this study suggests that if Pb is present in the oral environment, it may deposit in enamel during the caries process. Copyright (C) 2011 S. Karger AG, Basel

Determination of eutectic solidification mode in Sr-modified hypoeutectic Al-Si alloys by EBSD

The effect of eutectic modification by strontium on nucleation and growth of the eutectic in hypoeutectic Al-Si foundry alloys has been investigated by electron back-scattering diffraction (EBSD) mapping. Specimens were prepared from three hypoeutectic AlSi base alloys with 5, 7 and 10 mass%Si and with different strontium contents up to 740 ppm for modification of eutectic silicon. By comparing the orientation of the aluminium in the eutectic to that of the surrounding primary aluminium dendrites? the growth mode of the eutectic could be determined. The mapping results indicate that the eutectic grew from the primary phase in unmodified alloys. When the eutectic was modified by strontium, eutectic grains nucleated separately from the primary dendrites. However, in alloys with high strontium levels, the eutectic again grew from the primary phase. These observed effects of strontium additions on the eutectic solidification mode are independent of silicon content in the range between 5 and 10 mass%Si.

Do increases in xylem sap pH and/or ABA concentration mediate stomatal closure following nitrate deprivation?

Stomatal conductance (g(s)) of pepper (Capsicum annuum L.) plants decreased during the second photoperiod (day 2) after withholding nitrate (N). Stomatal closure of N-deprived plants was not associated with a decreased shoot water potential (Psi(shoot)); conversely Psi(shoot) was lower in N-supplied plants. N deprivation transiently (days 2 and 3) alkalized (0.2-0.3 pH units) xylem sap exuded from de-topped root systems under root pressure, and xylem sap expressed from excised shoots by pressurization. The ABA concentration of expressed sap increased 3-4-fold when measured on days 2 and 4. On day 2, leaves detached from N-deprived and N-supplied plants showed decreased transpiration rates when fed an alkaline (pH 7) artificial xylem (AX) solution, independent of the ABA concentration (10-100 nM) supplied. Thus changes in xylem sap composition following N deprivation can potentially close stomata. However, the lower transpiration rate of detached N-deprived leaves relative to N-supplied leaves shows that factors residing within N-deprived leaves also mediate stomatal closure, and that these factors assume greater importance as the duration of N deprivation increases.

Estudo comparativo do pH e do volume salivar em indivíduos com laringofaringite crônica por doença do refluxo gastroesofágica antes e após o tratamento

INTRODUÇÃO: A Doença do Refluxo Gastroesofágico (DRGE) é a doença digestiva mais prevalente da atualidade e, recentemente, tem sido implicada em uma gama de alterações do seguimento laringofaríngeo (RLF). No entanto, pouco se sabe dos mecanismos fisiopatológicos destas manifestações supraesofágicas da DRGE. Os achados clínicos contraditórios e recentes pesquisas sugerem haver deficiências na capacidade de defesa deste seguimento. Uma das principais responsáveis pela homeostase da mucosa oral e do trato digestivo é a saliva com seu conteúdo orgânico e inorgânico. Tanto alterações do pH quanto do volume salivar já foram correlacionados com os sintomas e sinais sugestivos da DRGE e RLF. Estudo recente de nossa autoria demonstra diminuição estatisticamente significante do pH salivar de indivíduos com RLF quando comparado a controles sem a doença. Outro estudo constatou correlação entre a redução do volume X pH da saliva em indivíduos com DRGE, estando esta redução diretamente relacionada aos níveis de pH esofágico constatados durante pH-metria esofágica de 24 horas. OBJETIVOS: Avaliar como se comportam o pH e volume da saliva em um mesmo indivíduo com DRGE e RLF antes e após o tratamento clínico. MATERIAL E MÉTODO: Vinte e três pacientes com RLF tiveram o pH e volume da saliva total testados antes e após receberem tratamento com droga bloqueadora de bomba de prótons durante 12 semanas. RESULTADOS: Houve uma diferença estatisticamente significante (p<0,001) entre o pH da saliva antes e após o tratamento, estando este maior após o controle clínico da doença. O volume de saliva no paciente tratado foi significativamente maior do que no paciente pré-tratamento (p=0.009). DISCUSSÃO: Os achados sugerem que o pH salivar é influenciado pela presença de refluxo gastroduodenal à região laringofaríngea. Caso estudos futuros com populações maiores realmente comprovem esta correlação, poderemos cogitar a possibilidade de usar a mensuração do pH salivar, que é feita de forma rápida e não invasiva, como um meio de diagnosticar e avaliar o comportamento e controle do Refluxo Laringofaríngeo.

Mantle source heterogeneity, magma generation and magmatic evolution at Terceira Island (Azoresarchipelago): Constraints from elemental and isotopic (Sr, Nd, Hf, and Pb) data

This work addresses the present-day (<100 ka) mantle heterogeneity in the Azores region through the study of two active volcanic systems from Terceira Island. Our study shows that mantle heterogeneities are detectable even when "coeval" volcanic systems (Santa Barbara and Fissural) erupted less than 10 km away. These volcanic systems, respectively, reflect the influence of the Terceira and D. Joao de Castro Bank end-members defined by Beier et at (2008) for the Terceira Rift Santa Barbara magmas are interpreted to be the result of mixing between a HIMU-type component, carried to the upper mantle by the Azores plume, and the regional depleted MORB magmas/source. Fissural lavas are characterized by higher Ba/Nb and Nb/U ratios and less radiogenic Pb-206/Pb-204, Nd-143/Nd-144 and Hf-176/Hf-177, requiring the small contribution of delaminated sub-continental lithospheric mantle residing in the upper mantle. Published noble gas data on lavas from both volcanic systems also indicate the presence of a relatively undegassed component, which is interpreted as inherited from a lower mantle reservoir sampled by the ascending Azores plume. As inferred from trace and major elements, melting began in the garnet stability field, while magma extraction occurred within the spinel zone. The intra-volcanic system's chemical heterogeneity is mainly explained by variable proportions of the above-mentioned local end-members and by crystal fractionation processes. (C) 2011 Elsevier By. All rights reserved.

Sr. Santo Cristo reúne cidadãos do mundo

Na qualidade de Diretora Regional das Comunidades, fomos responsável pela redação dos artigos e coordenação da página "Comunidades", integrada no jornal Açoriano Oriental, servindo a mesma para a divulgação das atividades realizadas pela Direção Regional Das Comunidades do Governo dos Açores.

O pórfiro dacítico de Valverde (Alcácer do Sal) idade Rb-Sr e suas implicações

The unexpected discovery of a small outcrop of igneous rock isolated within an extensive outcrop of Neogene and Quaternary sediments called for the attention of CEPUNL's researchers. The rock is a dacite whose Rb-Sr age (C. A. and M. H. C.) is 291 M. y. upper Carboniferous. Hence the dacite may be related to volcanism in the Santa Suzana tectonic basin.

A director’s approach to art and religion : o quadro, um musical da Paixão segundo o sr. João (The masterpiece, a musical of The passion according to John): trabalho de projecto

Trabalho de Projecto submetido à Escola Superior de Teatro e Cinema para cumprimento dos requisitos necessários à obtenção do grau de Mestre em Teatro - especialização em Encenação.

Chlorella sp. coagulation‐flocculation by inducing a modification on the pH broth medium

Dissertação apresentada à Faculdade de Ciências e Tecnologia da Universidade Nova de Lisboa para a obtenção do grau de Mestre em Bioenergia