Effect of staining agents on color change of composites

Composite resins are materials that can present color changing when exposed to pigments. Objective: The aim of this study was to evaluate, in vitro, the color changing of composites after immersion in different substances for different periods. Material and methods: Two microhybrid composite resins: Charisma (Heraeus – Kulzer) and Opallis (FGM) were used. Red wine and acai pulp were also used as immersion medium. For this study, 32 specimens with 10 mm of diameter and 2 mm of thickness were used, divided into 4 groups: Group 1 – Opallis composite immersed in red wine solution; Group 2 – Opallis composite immersed in acai berry pulp solution; Group 3 – Charisma composite immersed in red wine solution; Group 4 – Charisma composite immersed in acai berry pulp solution. The specimens were evaluated in the following time periods: T0 – baseline, T1 – 24 hours, T2 – 48 hours, T3 – 72 hours and T4 – 96 hours. For the assessment of staining, a spectrophotometer for colorimetry was used (Color Guide 45 / 0, PCB 6807 BYK-Gardner Gerestsried GmBH, Germany), and the values obtained were transferred to a computer and recorded according to CIELAB system. Results: The data were evaluated using Kruskal- Wallis non-parametric tests with the following mean values for the immersion periods of 24, 48, 72 and 96 hours, respectively: G1 – 7.35, 7.84, 9.04,10.48; G2 – 2.92, 4.15, 4.30, 4.64; G3 – 3.14, 7.35, 8.13, 8.43, G4 – 4.49, 5.99, 6.92, 6.76. Conclusion: Red wine showed a higher tendency toward altering the composite color than acai berry pulp. In addition, no significant difference was found concerning to the behavior of the two composite resins. Concerning to the immersion time periods, significant differences were only observed among the groups in the 24 hour time period.

A study on X-ray irradiation of composite polyaniline LB films

Composite Langmuir-Blodgett (LB) films from polyaniline and cadmium stearate have been irradiated with ionizing X-rays for various exposure times. In the initial stages of X-ray irradiation the absorption peak at 580 nm of an as-deposited film was seen to decrease with a concomitant increase in the absorption in the long wavelength region (700-1100 nm). Upon prolonging the irradiation, the absorption maximum shifted to 800 nm with the LB film color changing to green, characteristic of acid doped polyaniline. The changes in the Fourier transform infrared (FTIR) spectra upon irradiation are also similar to those observed upon acid doping of polyaniline. When compared with acid doping, two major differences were observed for the LB films exposed to X-rays. First, the packing order of the cadmium stearate domains in the composite LB films - as observed by X-ray diffraction - is not affected by the X-ray irradiation. In addition, no significant increase in the DC conductivity was noted after the X-ray exposure whereas similar LB films have their conductivity increased by an order of magnitude upon acid doping. These differences may be explained by considering that the inter-domain contribution to the conductivity is increased by the acid doping because the insulating cadmium stearate domains are destroyed, which does not occur with the X-ray irradiation. (C) 1998 Elsevier B.V. S.A. All rights reserved.

First-void versus midstream urine culture for detection of Ureaplasma urealyticum in the urinary tract

Quantitative Ureaplasma urealyticum culture was performed on clean first-void and midstream urine to evaluate the presence of these mollicutes in the urinary tract. The results, expressed as color changing units (CCU), showed that 14 (63%) of the 22 Ureaplasma urealyticum positive patients yielded counts equal to or higher that 10(7) CCU/mL for both the initial and the middle urine specimens. No abnormal chemical or microscopic findings (protein content, leukocyte numbers) were observed. The occurrence of U. urealyticum in midstream urine samples, even when numbers are considered, may be no more than a guide to the presence of ureaplasmas in the urinary tract.

Production and preservation of fresh-cut 'Tommy Atkins' mango chunks

During the 1999/00 and 2000/01 seasons, sliced 'Tommy Atkins' mangoes were packaged with three different types of polymeric films; polypropylene (PP) cups, low-density polyethylene (LPDE) bags or polyethylene terephthalate (PET) clamshell trays, and stored at 3°C for 2 weeks. The mango chunks were evaluated for flavor, appearance, colour, total soluble solids (TSS), total titratable acidity (TTA), ascorbic acid (AA) contents, O2 and CO 2 concentration in the packages, as well as respiration. Shelf life based on visual appearance was 14 days, with the products showing good appearance and agreeable aroma. The TTA content in chunks packaged in PP cups or PET trays were reduced during the storage, and with the color changing from light yellow to dark yellow. The chunks respiration in PP cups or LPDE bags were 64.6 and 87.9 mL CO2.kg-1.h-1, and in PP cups or PET trays were 45.86 and 43.92 mL CO2.kg-1.h -1, respectively for 1999/00 and 2000/01 seasons. The percentages of O2 and CO2 in the packages were stabilized after 2-4 hours, and the atmosphere had 11-17% and 1-10% of them. The microbiological content was lower than the allowed. No differences were observed between the seasons, and the best packages were the cups.

Polímeros de coordenação de cobre (II) contendo ligantes nitrogenados lineares: caracterização e propriedades vapocrômicas

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Laboratory testes with quality data in Dentistry

In laboratory tests, just following the manufacturer’s instructions of materials or equipments may not be enough to obtain reliable data. Thus, intra and inter-examiners studies may be required. The aim of this study was to illustrate the application of the Intraclass Correlation Coefficient (r) in a study related to the color changing and hardness of composite resin conducted by two examiners. The color and hardness of 10 specimens of composite resin were evaluated by a colorimetric spectrophotometer and hardness tester, respectively, at two different times. Two trained examiners performed two measurements with an interval of one week. Specimens were stored in artificial saliva at 37±1ºC for 7 days. The Intraclass Correlation was used for analysis of intra and inter-examiner reproducibility. The intra-examiner reproducibility was 0.79, 0.44 and 0.76 for L, a and b color coordinates for the examiner 1 and 0.84, 0.23, 0.21 for examiner 2. For hardness, r-values were 0.00 and 0.23 for the examiner 1 and 2, respectively, showing unsatisfactory agreement on color and hardness evaluation for both examiners. It was noted that only the observation of protocol for use of equipment and examiners training were not sufficient to collect reliable information. Thus, adjustments in the experimental protocol were made and devices were produced to standardize the measurements. The reproducibility study was performed again. For examiner 1, values as 0.90, 0.59 and 0.79 were verified for L, a and b coordinates and, for examiner 2 were obtained values of 0.90, 0.75, 0.95. In relation to hardness, r-values of 0.75 and 0.71 were obtained for examiners 1 and 2, respectively. The inter-examiner reproducibility was 0.86, 0.87, 0.91 for L, a and b coordinates and 0.79 for hardness. It was concluded that intra and inter-examiner calibration is essential for obtaining quality measurements in laboratory tests.