Study of the chemical interaction between a high-viscosity glass ionomer cement and dentin

Objective: To investigate the chemical interactions between a high-viscosity glass ionomer cement (GIC) (KetacTM Molar Easymix, 3M ESPE, Seefeld, Bavaria, Germany) and human dentin. It was also analyzed the dynamics of GIC setting mechanism based on the time intervals required for the GIC and the GIC mixed with dentin to achieve stability. Material and Methods: Each constituent of GIC – powder (P) and liquid (L) – and powdered dentin (D), as well as the associations P+L, D+L, and P+L+D in the concentrations of 29%, 50%, 65%, 78%, 82%, and 92% of GIC were analyzed with Fourier transform infrared (FTIR) and Raman spectroscopy. Results: New optical absorption bands and/or Raman bands, which were not present in P, L, or D, were observed in the associations. The concentrations of 29% and 50% of GIC showed higher interaction, revealing that the amount of dentin influences the formation of new optical absorption or scattering bands. FTIR bands showed that the setting time to achieve bond stability was longer for the high-viscosity GIC (38±7 min) than for the sample with 29% of GIC (28±4 min). Conclusions: The analysis revealed the formation of new compounds or molecular rearrangements resulting from the chemical interactions between GIC and dentin. Moreover, this study provides an effective method to evaluate the dynamics of the setting mechanism of GICs

Curcumin–β-cyclodextrin inclusion complex: Stability, solubility, characterisation by FT-IR, FT-Raman, X-ray diffraction and photoacoustic spectroscopy, and food application

AbstractCurcumin was complexed with β-CD using co-precipitation, freeze-drying and solvent evaporation methods. Co-precipitation enabled complex formation, as indicated by the FT-IR and FT-Raman techniques via the shifts in the peaks that were assigned to the aromatic rings of curcumin. In addition, photoacoustic spectroscopy and X-ray diffraction, with the disappearance of the band related to aromatic rings, by Gaussian fitting, and modifications in the spectral lines, respectively, also suggested complex formation. The possible complexation had an efficiency of 74% and increased the solubility of the pure colourant 31-fold. Curcumin–β-CD complex exhibited a sunlight stability 18% higher than the pure colourant. This material was stable to pH variations and storage at −15 and 4°C. With an isothermal heating at 100 and 150°C for 2h, the material exhibited a colour retention of approximately 99%. The application of curcumin–β-CD complex in vanilla ice creams intensified the colour of the products and produced a great sensorial acceptance

Evaluation of the influence of light-curing units on the degree of conversion in depth of a bulk-fill resin

It is known that bulk-fill have been widely studied and used by dentists in the clinic. However, the use of light-curing units that do not have the ability to adequately light-cure these materials at the appropriate depth can affect their clinical perfor

In vitro evaluation of composite resin fluorescence after natural aging

Some composite resins contain luminophorous agents in order to reproduce tooth fluorescence. The objective of this study was to compare the fluorescence spectra emitted by composite resins with those of human enamel and dentin, and their emission behaviour after a 90-day natural aging period. Nine shades of the composite resins Z350XT/3M (XT), Opallis/FGM (OP) and Empress Direct/Ivoclar-Vivadent (ED) were analyzed. Five specimens (10.0 mm x 2.0mm) were fabricated for each shade. Enamel (5.0 mm x 0.30 mm) and dentin (5.0 mm x 1.0 mm) specimens were obtained from sound human third molars. Fluorescence spectra of human dentin and enamel as well as the composite specimens immediately after fabrication were measured at the excitation peaks of 375, 395 and 410 nm. To assess composite resin fluorescence intensity changes over time, measurements were conducted after 30, 60 and 90 days, at 395 nm. Differences in fluorescence intensity over time were analyzed with ANOVA and Tukey?s test (p<0.05). Fluorescence spectra baseline values of composites demonstrated no differences in intensity among the excitation peaks tested, with maximum emission found at the peak of 450 nm. Enamel and dentin spectra varied with different excitations, and the greater the excitation, the longer the wavelength in comparison to composite resins. After 90 days, XT presented an increase in fluorescence intensity, while OP and ED showed a reduction when compared with baseline values. Fluorescence intensity of composite resins changed during the period analyzed, with an emission behavior different from that of human enamel and dentin. The main changes occurred in the first 30 days

A short film (and CD-ROM) on the controversial notion of the concept of force

O presente trabalho ´e o resultado de um projeto (SPEC/PROIN- CAPES) paraa realiza¸c~ao de v´ıdeos (e CD-ROMs) de curta-metragem para o ensino de F´ısica no EnsinoM´edio e Superior. O v´ıdeo conta a hist´oria do conceito de for¸ca da no¸c~ao aristot´elica deantipresistase, `as no¸c~oes de impetus adquirido de Philopponus, Oresme e Buridan, at´e ano¸c~ao din^amica desenvolvida por Newton. O enredo foi desenvolvido e baseado sobre asconcep¸c~oes alternativas relacionadas `a fenomenologia da Mec^anica

Time-resolved fluctuation during the photochemical reaction of a photoreceptor protein: Phototropin1LOV2-linker

Although the relationship between structural fluctuations and reactions is important for elucidating reaction mechanisms, experimental data describing such fluctuations of reaction intermediates are sparse. In order to investigate structural fluctuations during a protein reaction, the compressibilities of intermediate species after photoexcitation of a phot1LOV2-linker, which is a typical LOV domain protein with the C-terminal linker including the J-α helix and used recently for optogenetics, were measured in the time-domain by the transient grating and transient lens methods with a high pressure optical cell. The yield of covalent bond formation between the chromophore and a Cys residue (S state formation) relative to that at 0.1 MPa decreased very slightly with increasing pressure. The fraction of the reactive species that yields the T state (linker-unfolded state) decreased almost proportionally with pressure (0.1-200 MPa) to about 65%. Interestingly, the volume change associated with the reaction was much more pressure sensitive. By combining these data, the compressibility changes for the short lived intermediate (S state) and the final product (T state) formation were determined. The compressibility of the S state was found to increase compared with the dark (D) state, and the compressibility decreased during the transition from the S state to the T state. The compressibility change is discussed in terms of cavities inside the protein. By comparing the crystal structures of the phot1LOV2-linker at dark and light states, we concluded that the cavity volumes between the LOV domain and the linker domain increase in the S state, which explains the enhanced compressibility

Análise dos produtos de NDVI dos sensores MODIS/Terra e VEGETATION/SPOT

This study aims to assess the Normalized Difference Vegetation Index (NDVI) estimated by Moderate Resolution Imaging Spectroradiometer (MODIS) aboard Terra Satellite and by VEGETATION sensor aboard Satellite pour l'Observation de la Terre (SPOT). The NDVI values of January 01, 2012 (rainy season in almost Brazil territory) and July 21, 2012 (dry season in central-western of Brazil) were used and a compatibilization was performed between MODIS and VEGETATION due to spatial and temporal differences, taking into consideration the acquisition geometry, the percentage of cloud cover, among others. Moreover, to evaluate the NDVI values we performed a random sampling of 100 points, weighted by the total area of each Brazilian biome. Thus, we sampled 49, 24, 13, 10, 2 and 2 points for the Amazon, Cerrado, Atlantic Forest, Caatinga, Pantanal and Pampa biomes, respectively. Initial results indicate that the main differences between NDVI products could be related to the algorithm used for removing pixels with cloud, since the image with the peak of clouds shows the highest differences in estimated values. The statistical analysis indicates a significant difference between the NDVI values estimated by VEGEGETATION/SPOT and by MODIS/Terra for the first 10 days of January 2012 (p> 0.05, t-student). During this period, the correlation between D10 and S10 NDVI products with MODIS data were approximately 67%. Also, in July 21, 2012, the products showed a good agreement between both data, with a correlation of approximately 90% (p> 0.05, t-student).Pages: 1480-148

Study of the chemical interaction between a high-viscosity glass ionomer cement and dentin

Abstract Objective To investigate the chemical interactions between a high-viscosity glass ionomer cement (GIC) (KetacTM Molar Easymix, 3M ESPE, Seefeld, Bavaria, Germany) and human dentin. It was also analyzed the dynamics of GIC setting mechanism based on the time intervals required for the GIC and the GIC mixed with dentin to achieve stability. Material and Methods Each constituent of GIC – powder (P) and liquid (L) – and powdered dentin (D), as well as the associations P+L, D+L, and P+L+D in the concentrations of 29%, 50%, 65%, 78%, 82%, and 92% of GIC were analyzed with Fourier transform infrared (FTIR) and Raman spectroscopy. Results New optical absorption bands and/or Raman bands, which were not present in P, L, or D, were observed in the associations. The concentrations of 29% and 50% of GIC showed higher interaction, revealing that the amount of dentin influences the formation of new optical absorption or scattering bands. FTIR bands showed that the setting time to achieve bond stability was longer for the high-viscosity GIC (38±7 min) than for the sample with 29% of GIC (28±4 min). Conclusions The analysis revealed the formation of new compounds or molecular rearrangements resulting from the chemical interactions between GIC and dentin. Moreover, this study provides an effective method to evaluate the dynamics of the setting mechanism of GICs