Comparative clinical study of the effectiveness of different dental bleaching methods - two year follow-up

This study evaluated color change, stability, and tooth sensitivity in patients submitted to different bleaching techniques. Material and methods: In this study, 48 patients were divided into five groups. A half-mouth design was conducted to compare two in-office bleaching bleaching techniques (with and without light activation): G1: 35% hydrogen peroxide (HP) (Lase Peroxide - DMC Equipments, Sao Carlos, SP, Brazil) + hybrid light (HL) (LED/Diode Laser, Whitening Lase II DMC Equipments, Sao Carlos, SP, Brazil); G2: 35% HP; G3: 38% HP (X-traBoost - Ultradent, South Jordan UT, USA) + HL; G4: 38% HP; and G5: 15% carbamide peroxide (CP) (Opalescence PF - Ultradent, South Jordan UT, USA). For G1 and G3, HP was applied on the enamel surface for 3 consecutive applications activated by HL. Each application included 3x3' HL activations with 1' between each interval; for G2 and G4, HP was applied 3x15' with 15' between intervals; and for G5, 15% CP was applied for 120'/10 days at home. A spectrophotometer was used to measure color change before the treatment and after 24 h, 1 week, 1, 6, 12, 18 and 24 months. A VAS questionnaire was used to evaluate tooth sensitivity before the treatment, immediately following treatment, 24 h after and finally 1 week after. Results: Statistical analysis did not reveal any significant differences between in-office bleaching with or without HL activation related to effectiveness; nevertheless the time required was less with HL. Statistical differences were observed between the result after 24 h, 1 week and 1, 6, 12, 18 and 24 months (integroup). Immediately, in-office bleaching increased tooth sensitivity. The groups activated with HL required less application time with gel. Conclusion: All techniques and bleaching agents used were effective and demonstrated similar behaviors.

Metal binding selectivity of oxa-aza macrocyclic ligand: a DFT study of first- and second-row transition metal for four coordination systems

A detailed theoretical study of the 1,7,1l,17-tetraoxa-2,6,12,16-tetraaza-cycloeicosane ligand ([20]AneN(4)O(4)) coordinated to Fe2+, Co2+, Ni2+, Ru2+, Rh2+, and Pd2+ transition metal ions was carried out with the B3LYP method. Two different cases were performed: when nitrogen is the donor atom (1a (q) ) and also with the oxygen as the donor atom (1b (q) ). For all the cases performed in this study 1a (q) structures were always more stable than the 1b (q) ones. Considering each row is possible to see that the energy increases with the increase of the atomic number. The M2+ cation binding energies for the 1a (q) complexes increase with the following order: Fe2+ < Ru2+ < Co2+ < Ni2+ < Rh2+ < Pd2+.

ANATOMICAL AND FUNCTIONAL STUDY OF THE MEDIAL COLLATERAL LIGAMENT COMPLEX OF THE ELBOW

Objective: To carry out an anatomical study of the medial collateral ligament, an important elbow stabilizer in different degrees of elbow flexion-extension. Methods: Forty elbows were dissected in order to analyze the functional behavior of the anterior, posterior and transverse ligament bands during valgus stress maneuvers of the elbow in different degrees of flexion and extension. Two groups were determined; in the group GPA the posterior band of the ligament was sectioned initially, then the articular capsule and finally the anterior band; in group GAP this order was reversed. Results: Instability was observed in GPA only in the third stage, when there was a greater mean elbow's opening during the flexion (between 50 degrees and 70 degrees); in GAP the instability was present since the first stage; the degrees of flexion with greater instability were the same as in group GPA. Conclusion: The anterior band of the medial collateral ligament of the elbow is the most important stabilizer of the elbow valgus instability, and its principal action occurs between 50 degrees and 70 degrees of elbow flexion. Level of Evidence III, Diagnostic Studies Investigating a diagnostic test.

Comparative study of beta-carotene and microencapsulated beta-carotene: Evaluation of their genotoxic and antigenotoxic effects

beta-Carotene (BC) is one of the natural pigments that is most commonly added to food; however, the utilization of BC is limited due to its instability. Microencapsulation techniques are commonly used because they can protect the microencapsulated material from oxidization. Nevertheless, the properties of the encapsulated compounds must be studied. We compared the antigenotoxic potential of pure and microencapsulated beta-carotene (mBC) in Wistar rats. Two doses of BC or mBC (2.5 or 5.0 mg/kg) were administered by gavage over a period of 14 days. The final gavage was followed by an injection of doxorubicin (DXR). After 24 h the animals were euthanized. The micronucleus test results showed that when both mBC and DXR were given, only the higher dose was antigenotoxic. The results of the comet assay show that when given in association with DXR, mBC had protective effects in the liver. The differences between the results obtained with BC and mBC suggest that possibly the carotenoid biodisponibility was modified by the process of microencapsulation. In conclusion, mBC does not lose its protective properties, but higher doses must be used to observe antigenotoxic effects. This is the first time that the genotoxicity and antigenotoxicity of a microencapsulated compound was evaluated in vivo. (C) 2012 Elsevier Ltd. All rights reserved.

Study of CuO/CeO2 catalyst with for preferential CO oxidation reaction in hydrogen-rich feed (PROX-CO)

The CuO/CeO2 system was investigated as a catalyst for preferential CO oxidation reaction in hydrogen-rich feed (PROX-CO). The catalysts were prepared by deposition-precipitation (DEP) and co-precipitation (COP) methods and the catalytic performance reveals that the preparation method influences the properties of solids prepared, where a direct consequence is the difference in behavior of the catalysts in the PROX-CO reaction. A high specific area and a better dispersion of the metallic phase were obtained in the catalyst prepared by co-precipitation. The redox properties during the reaction were reported by measures of temperature programmed reduction (TPR), OSC measurements and X-ray absorption near edge structure (XANES-TPR) in situ showed the relationship between the preparation method, the physicochemical characteristics and redox properties in the PROX-CO reaction. By this means, the good dispersion of CuO and the best oxygen capacity are the response of the high performance of CuO/CeO2-COP catalysts for the PROX-CO reaction. Crown Copyright (c) 2012 Published by Elsevier B.V. All rights reserved.

Study of La2-xCaxCuO4 perovskites for the low temperature water gas shift reaction

The effects of small fractions of calcium (x = 0, 0.05, 0.1, 0.15, and 0.20) on the structure and the catalytic properties of La2-xCaxCuO4 peroviskites have been investigated. The samples have been synthesized using the co-precipitation method. Perovskite-type oxides were characterized by XRD, TPR, XPS, XANES, SEM, and TEM. Catalytic tests for the water gas shift reaction (WGSR) were carried out in a tubular reactor at 290 degrees C. All samples showed a well-defined perovskite structure with surface areas between 6 and 18 m(2) g(-1). The partial substitution of La by Ca enhanced the stability of the perovskites and increased their reduction temperature. All catalysts were actives for WGSR, and the best catalytic performance was obtained for the La1.85Ca0.15CuO4 catalyst, but the samples with 5 and 10% of Ca had the best TOF values for reaction. These results can be associated to promoter effect of calcium, the high surface area, and the reducible species Cu-0 and Cu1+. (C) 2011 Elsevier B.V. All rights reserved.

A theoretical study of SnF2+, SnCl2+, and SnO2+ and their experimental search

We present a detailed theoretical study of the stability of the gas-phase diatomic dications SnF2+, SnCl2+, and SnO2+ using ab initio computer calculations. The ground states of SnF2+, SnCl2+, and SnO2+ are thermodynamically stable, respectively, with dissociation energies of 0.45, 0.30, and 0.42 eV. Whereas SnF2+ dissociates into Sn2+ + F, the long range behaviour of the potential energy curves of SnCl2+ and SnO2+ is repulsive and wide barrier heights due to avoided crossing act as a kind of effective dissociation energy. Their equilibrium internuclear distances are 4.855, 5.201, and 4.852 a(0), respectively. The double ionisation energies (T-e) to form SnF2+, SnCl2+, and SnO2+ from their respective neutral parents are 25.87, 23.71, and 25.97 eV. We combine our theoretical work with the experimental results of a search for these doubly positively charged diatomic molecules in the gas phase. SnO2+ and SnF2+ have been observed for prolonged oxygen (O-16(-)) ion beam sputtering of a tin metal foil and of tin (II) fluoride (SnF2) powder, respectively, for ion flight times of about 10(-5) s through a magnetic-sector mass spectrometer. In addition, SnCl2+ has been detected for O-16(-) ion surface bombardment of stannous (tin (II)) chloride (SnCl2) powder. To our knowledge, SnF2+ is a novel gas-phase molecule, whereas SnCl2+ had been detected previously by electron-impact ionization mass spectrometry, and SnO2+ had been observed before by spark source mass spectrometry as well as by atom probe mass spectrometry. We are not aware of any previous theoretical studies of these molecular systems. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4758475]