Effect of Cervitec (R) on mutans streptococci in plaque and on caries formation on occlusal fissures of erupting permanent molars

The aim of this study was to evaluate the effect of Cervitec(R) on the abundance of mutans streptococci (MS) in occlusal dental plaque and on 2-year caries increment of partly erupting first permanent molars. Sixteen healthy schoolchildren aged 6-8 years, with at least 2 sound contralateral partly erupted permanent molars, received diet counselling and daily parental supervised toothbrushing with a fluoride dentifrice. Stimulated saliva samples were collected at baseline and after 1 year to evaluate MS levels. In a split-mouth design, Cervitec varnish was applied to one of the teeth at baseline and after 3 and 6 months, while the other tooth in the same jaw was a control. At the 9-month follow-up the teeth were in occlusal contact. At this time, varnish was not applied. At 3 and 6 months after the first application of varnish a significant suppression of MS was observed in plaque. Caries investigations, performed at baseline and every 3 months during the 2 years after the start of the study, showed that all the teeth treated with the varnish were free of caries after 2 years, whereas 8/16 control teeth developed incipient caries. In conclusion, our results suggest that treatment with Cervitec reduces MS in plaque on erupting permanent molars and can lead to a significant decrease in caries incidence. Copyright (C) 2002 S. Karger AG, Basel.

Evaluation of Ir, Ru, and W as permanent modifiers for the simultaneous determination of As, Bi, Pb, Sb, and Se in natural water by electrothermal atomic absorption spectrometry

Iridium-, Ru-, and W-coated platforms were prepared by thermal treatment of the transversely heated graphite atomizer and investigated for the simultaneous determination of As, Bi, Pb, Sb, and Se in tap water by electrothermal atomic absorption spectrometry. The maximum pyrolysis temperature for As and Bi increased in a modifier sequence W < Ru < Ir. For Pb, Sb, and Se, this sequence was W < Ru, It. Calculated characteristic masses in the presence of It, Ru, and W were 35, 33, and 35 pg for As; 63, 51, and 52 pg for Bi; 50, 32, and 34 pg for Pb; 40, 35, and 31 pg for Sb; and 39, 39, and 93 pg for Se, respectively. Ruthenium was elected as the optimum modifier.Repeatability of the measurements was typically < 6%. Recoveries of As, Bi, Pb, Sb, and Se added to tap water samples varied from 79 to 109%. Accuracy was also checked by analysis of five certified reference materials (CRMs) from the National Institute of Standards and Technology (NIST1640 - Trace Elements in Natural Water; NIST 1643d Trace Elements in Water) and High Purity Standards (Trace Metals in Drinking Water Standards, lots #812708, #591107, and #710710). A paired t-test showed that the results for the CRMs were in agreement at the 95% confidence level with the certified values. The graphite tube lifetime was about 650 firings. multi-element determination is particularly challenging due to the necessity of carefully optimizing compromise conditions.Based on the considerations listed above, the aim of this paper was to evaluate the behavior of Ir, Ru, and W as permanent modifiers for the simultaneous determination of As, Bi, Pb, Sb, and Se. The performance of the proposed procedure was also verified after the ETAAS analysis of tap waters and reference materials.

2 PERMANENT LINEAR-CHAINS OF SEX-CHROMOSOMES IN NEOTERMES-FULVESCENS AND KARYOTYPES OF 2 OTHER NEOTROPICAL KALOTERMITIDAE SPECIES (INSECTA, ISOPTERA)

Meiosis and (or) mitosis of males and females of Cryptotermes brevis, Eucryptotermes wheeleri, and Neotermes fulvescens, all of them from the neotropical region, were analyzed. Cryptotermes brevis showed a similar karyotype to that obtained by other authors for specimens of the neartic and Australian regions (2n = 36 for females and 2n = 37 for males, with XX and XYY sex mechanisms, respectively). Eucryptotermes wheeleri, the only species that has been described in this genus, showed the lowest number of chromosomes reported for Isoptera (2n = 22) until now. The male meiosis of this species presents a linear chain of six sex chromosomes, three of them being X and three of them Y chromosomes. Neotermes fulvescens showed a diploid number of 40 for males and 42 for females and, in the first male meiosis, two linear chains of chromosomes, both related to sex. One of the chains, named A, presented nine chromosomes and the other, named B, seven chromosomes. Hypotheses to explain these mechanisms are formulated in this paper and putative ancestral relationships with other species of Kalotermitidae are presented.

Comparative ablation rate from a Er : YAG laser on enamel and dentin of primary and permanent teeth

This study was conducted to analyze the ablation rate and micromorphological aspects of microcavities in enamel and dentin of primary and permanent teeth using a Er:YAG laser system. Micromorphological evaluation has been performed in terms of permanent teeth; however, little information about Er: YAG laser interaction with primary teeth can be found in the literature. Because children have been the most beneficiary patients with laser therapy in our offices, it is extremely necessary to compare the effects of this kind of laser system on the enamel and dentin of permanent and primary teeth. In this study, we used eleven intact primary anterior exfoliated teeth and six extracted permanent molar teeth. We used a commercial laser system: a Er: YAG Twin Light laser system (Fotona Medical Lasers, Slovenia) at 2940 nm, changing average energy levels per pulse ( 100, 200, 300, and 400 mJ) producing 48 microcavities in enamel and dentin of primary and permanent teeth. Primary teeth are more easily ablated than are permanent teeth, when related to enamel or dentin. However, while this laser system is capable of slowly revealing the enamel's microstructure, in dentin only the lowest laser energies permit this kind of observation, more easily decomposing the original tissue aspect, when related to primary or permanent teeth. Statistically, the only different factor at the 5% level was an energy per pulse of 400 mJ, confirming the results found in SEM. Our results showed that dentin in both primary and permanent teeth is less resistant to Er: YAG laser ablation; this fact is easily observed under SEM observation and through the ablation rate evaluation.

Direct and simultaneous determination of As, Cu, and Pb in Brazilian sugar cane spirits by graphite furnace AAS using Tungsten permanent modifier with Co-injection of Pd/Mg(NO3)(2)

A method was developed using the multi-element graphite furnace atomic absorption spectrometry technique for the direct and simultaneous determination of As, Cu, and Pb in Brazilian sugar cane spirit (cachaqa) samples. Also employed was the end-capped transversely heated graphite atomizer (THGA) with platforms pre-treated with W permanent modifier and co-injection of Pd/Mg(NO3)(2). Pyrolysis and atomization temperature curves were established in a cachaqa medium (1+1; v/v) containing 0.2% (v/v) HNO3 and spiked with 20 mu g L-1 As and Pb and 200 mu g L-1 Cu. The effect of the concentration of major elements usually present in cachaqa matrices (Ca, Mg, Na, and K) and ethanol on the absorbance of As, Cu, and Pb was investigated. Analytical working solutions of As, Cu, and Pb were prepared in 10% (v/v) ethanol plus 5.0 mg L-1 Ca, Mg, Na, and K. Acidified to 0.2% (v/v) HNO3, these solutions were suitable to build calibration curves by matrix matching. The proposed method was applied to the simultaneous determination of As, Cu, and Pb in commercial sugar cane spirits. The characteristic mass for the simultaneous determination was 16 pg As, 119 pg Cu, and 28 pg Pb. The pretreated tube lifetime was about 450 firings. The limit of detection (LOD) was 0.6 mu g L-1 As, 9.2 mu g L-1 Cu, and 0.3 pig L-1 Pb. The found concentrations varied from 0.81 to 4.28 mu g L-1 As, 0.28 to 3.82 mg L-1 Cu and 0.82 to 518 mu g L-1 Pb. The recoveries of the spiked samples varied from 94-112% (As), 97-111% (Cu), and 95-101% (Pb). The relative standard deviation (n=12) was 6.9%, 7.4%, and 7.7% for As, Cu, and Pb, respectively, present in a sample at 0.87 mu g L-1, 0.81 mg L-1, and 38.9 mu g L-1 concentrations.

Development of a new epoxy resin for superconducting magnet impregnation

A novel epoxy resin system based on a low viscosity Bisphenol-A (DGEBA)/Bisphenol-F (DGEBF) blend has been investigated for use in tight-wound superconducting magnet impregnation. The principle is to decrease the Bisphenol-A resin system viscosity by adding the low viscosity Bisphenol-F resin. The rheological and mechanical properties of the blend system are compared to the pure Bisphenol-A resin and also to the Bisphenol-F resin both cured with acid anhydride. For the vacuum/pressure impregnation, both the pure Bisphenol-F resin system and DGEBA/DGEBF blend system can be applied without S-glass fabric between coil layers due to its higher rigidity at low temperature and good resistance to thermal shock. This resin system have been tested for impregnation of copper and NbTi wire wound coils whilst Bisphenol-A resin system have been used for testing Nb3Sn coil impregnation where S-glass braid is present as wire insulation.

Evaluation of Bi as internal standard to minimize matrix effects on the direct determination of Pb in vinegar by graphite furnace atomic absorption spectrometry using Ru permanent modifier with co-injection of Pd/Mg(NO3)(2)

Bismuth was evaluated as an internal standard for the direct determination of Pb in vinegar by graphite furnace atomic absorption spectrometry using Ru as a permanent modifier with co-injection of Pd/Mg(NO3)(2). The correlation coefficient of the graph plotted from the non-nalized absorbance signals of Bi versus Pb was r=0.989. Matrix effects were evaluated by analyzing the slope ratios between the analytical curve, and analytical curves obtained from Pb additions in red and white wine vinegar obtained from reference solutions prepared in 0.2% (v/v) HNO3, samples. The calculated ratios were around 1.04 and 1.02 for analytical curves established applying an internal standard and 1.3 and 1.5 for analvtical curves without. Analytical curves in the 2.5-15 pg L-1 Pb concentration interval were established using the ratio Pb absorbance to Bi absorbance versus analvte concentration, and typical linear correlations of r=0.999 were obtained. The proposed method was applied for direct determination of Pb in 18 commercial vinegar samples and the Pb concentration varied from 2.6 to 31 pg L-1. Results were in agreement at a 95% confidence level (paired t-test) with those obtained for digested samples. Recoveries of Pb added to vinegars varied from 96 to 108% with and from 72 to 86% without an internal standard. Two water standard reference materials diluted in vinegar sample were also analyzed and results were in agreement with certified values at a 95% confidence level. The characteristic mass was 40 pg Pb and the useful lifetime of the tube was around 1600 firings. The limit of detection was 0.3 mu g L-1 and the relative standard deviation was <= 3.8% and <= 8.3% (n = 12) for a sample containing, 10 mu L-1 Pb with and without internal standard, respectively. (C) 2007 Elsevier B.V. All rights reserved.

Direct determination of Al, As, Cu, Fe, Mn, and Ni in fuel ethanol by simultaneous GFAAS using integrated platforms pretreated with W-Rh permanent modifier together with Pd plus Mg modifier

A method is proposed for the simultaneous determination of Al, As, Cu, Fe, Mn, and Ni in fuel ethanol by electrothermal atomic absorption spectrometry (ETAAS) using W-Rh permanent modifier together with Pd(NO3)(2) + Mg(NO3)(2) conventional modifier. The integrated platform of a transversely heated graphite atomizer (THGA) was treated with tungsten, followed by rhodium, forming a deposit containing 250 mug W + 200 mug Rh. A 500-muL, volume of fuel ethanol was diluted with 500 muL, of 0.14 mol L-1 HNO3 in an autosampler cup of the spectrometer. Then, 20 muL, of the diluted ethanol was introduced into the pretreated graphite platform followed by the introduction of 5 mug Pd(NO3)(2) + 3 mug Mg(NO3)(2). The injection of this modifier was required to improve arsenic and iron recoveries in fuel ethanol. Calibrations were carried out using multi-element reference solutions prepared in diluted ethanol (1 + 1, v/v) acidified to 0. 14 mol L-1 HNO3. The pyrolysis and atomization temperatures of the heating program were 1200degreesC and 2200degreesC, respectively, which were obtained with multielement reference solutions in acidic diluted ethanol (1 + 1, v/v; 0. 14 mol L-1 HNO3). The characteristic masses for the simultaneous determination in ethanol fuel were 78 pg Al, 33 pg As, 10 pg Cu, 14 pg Fe, 7 pg Mn, and 24 pg Ni. The lifetime of the pretreated tube was about 700 firings. The detection limits (D.L.) were 1.9 mug L-1 Al, 2.9 mug L-1 As, 0.57 mug L-1.Cu, 1.3 mug L-1 Fe, 0.40 mug L-1 Mn, and 1.3 mug L-1 Ni. The relative standard deviations (n = 12) were 4%, 4%, 3%, 1.5%, 1.2%, and 2.2% for Al, As, Cu, Fe, Mn, and Ni, respectively. The recoveries of Al, As, Cu, Fe, Mn, and Ni added to the fuel ethanol samples varied from 81% to 95%, 80% to 98%, 97% to 109%, 85% to 107%, 98% to 106% and 97% to 103%, respectively. Accuracy was checked for the Al, As, Cu, Fe, Mn, and Ni determination in 10 samples purchased at a local gas station in Araraquara-SP City, Brazil. A paired t-test showed that at the 95% confidence level the results were in agreement with those obtained by single-element ETAAS.