Abstract To evaluate the release of bisphenol-A glycidyl methacrylate (BisGMA), triethylene glycol dimethacrylate (TEGDMA), bisphenol A (BPA), and phthalates of the composite resin used in the bonding of spurs applied in the treatment of children with anterior open bite and its effects on human keratinocytes. Methodology Saliva samples of 22 children were collected before spur attachment (baseline) and 30 minutes (min) and 24 hours (h) after spur bonding. Analysis was performed using high-performance liquid chromatography (HPLC) coupled to tandem mass spectrometry (HPLC–MS/MS) and gas chromatography coupled to mass spectrometry (GC–MS). Standardized resin increments were added to three different dilutions of the cell culture medium. Keratinocytes (HaCaT) were cultivated in the conditioned media and evaluated for cell viability (MTT) and cell scratch assay. Results The levels of BisGMA (1.74±0.27 μg/mL), TEGDMA (2.29±0.36 μg/mL), and BPA (3.264±0.88 μg/L) in the saliva after 30 min, in comparison to baseline (0±0 μg/mL, 0±0 μg/mL, and 1.15±0.21 μg/L, respectively), presented higher numbers. After 24 h, the levels of the monomers were similar to the baseline. Phthalates showed no significant difference among groups. HaCat cells showed increased viability and reduced cell migration over time after exposure to methacrylate-based resin composites. Conclusion Resin composites, used to attach spurs in children with anterior open bite during orthodontic treatment, release monomers after polymerization and can influence the behavior of human keratinocytes, even at very low concentrations. Orthodontists should be aware of the risks of the resinous compounds release and preventive procedures should be held to reduce patient exposure.

Abstract Banana characteristics could provide yeast growth and support the action of yeast to produce beverages. The effects of enzymatic treatment, centrifugation, commercial yeast and two selected strains of Saccharomyces cerevisiae were investigated using the fermented banana Terra. Volatile organic compounds (VOCs) were determined by solid phase microextraction using gas chromatography mass spectrometry. The results showed that the condition employing enzymatic treatment, centrifugation and wet commercial yeast provided maximum ethanol yield (86%) and effiency (98%). Twenty-two compounds of distinct chemical classes were analysed including alcohols, esters, acids and aldehydes. The concentrations of the VOCs differed depending on the fermentation condition and were more influenced by using different yeasts. The limits of detection and quantification ranged from 0.056 to 2.694 mg L–1 and 0.057 to 2.904 mg L–1 respectively. Among the most prevalent VOCs the higher alcohols ranged from 353 to 1017 mg per 100 mL of anhydrous alcohol. The fermented banana studied showed a composition similar to other fermented fruit pulps.

Os livros didáticos, pela disponibilidade e acesso, são uma fonte importante de pesquisa para o professor de Ensino Médio, ao selecionar conteúdos e preparar suas aulas. Na tentativa de se adaptarem às novas tendências educacionais, esses livros vêm inserindo textos e assuntos que discutem os problemas vivenciados pela sociedade em geral. Nos livros de Química, um assunto que se faz presente é o Efeito Estufa. Analisou-se, neste trabalho, o tratamento e o aprofundamento dado a esse tema. Uma visão muito simplista do fenômeno foi percebida e, por isso, algumas sugestões foram incorporadas neste trabalho.

Widely available textbooks are an important source of research for high school teachers for both content selection and class preparation. As an attempt to adapt to new educational trends, these textbooks have introduced texts and subjects relevant for the discussion of current problems of the modern society. In the chemistry textbooks the Greenhouse Effect is one of these subjects. The aim of this work is to analyze the elements and discussion given in the textbooks on this topic. It was observed in general a simplistic treatment given to greenhouse effect and in order to improve the texts analyzed some suggestions are made.

The sampling of volatile organic compounds using solid phase microextraction is reviewed and its principles are described. The development and application of solid phase microextraction in the sampling of VOCs are presented and discussed.

Solid-phase microextraction (SPME) has been applied to direct extraction of 11 organophosphorus pesticides in water using a 100 mm fiber polydimethylsiloxane. The method was evaluated with respect time of exposure, detection limits (LODs), linearity and precision. The detection limits (S/N = 3) depend of each pesticide and varie about ng/L levels. The linearity was satisfactory with coefficients of correlation usually greater than 0.993. The precision of the method was determined by extraction from 4.0 mg/L aqueous standard with coefficients of variation between 5.7 to 17.2%.

This paper describes a study about the causes for the dropout of chemistry undergraduate students at UFMG in the nineties. The students' social and economic profile was outlined. It was observed a correlation between family income and academic performance and between failure at the beginning of the course and the dropout, but it seems that family income doesn't affect markedly the dropout. The endogenous and exogenous causes contribute equally for the dropout. The authors suggest that the dropout could be significantly reduced if the endogenous causes such as large classes, inadequate curricula and programmes, poor teaching and the unapproachability on the part of the teachers were faced.