Evaluation of the Bond Strength Between a Composite Resin and Enamel Submitted to Bleaching Treatment and Etched with Er:YAG Laser

Background: The use of laser irradiation for dental surface treatment may increase tooth-composite bond strength. Its use on bleached teeth may decrease the waiting time between bleaching and restorative procedures. Objective: This study aimed to evaluate the bond strength between a composite resin and bovine enamel bleached with 35% hydrogen peroxide and etched with Er:YAG laser. Materials and Methods: Thirty bovine teeth were randomly divided into six groups (n = 5): G1, unbleached and restored 24 h after storage in artificial saliva, etching with 35% phosphoric acid (PA) (control); G2, unbleached and restored 24 h after storage in artificial saliva, etching with Er:YAG laser and 35% PA; G3, bleached and restored immediately afterward, etching with 35% PA; G4, bleached and restored 24 h after bleaching, etching with 35% PA; G5, bleached and restored immediately afterward, etching with Er:YAG and 35% PA laser; G6, bleached and restored 24 h after bleaching, etching with Er:YAG laser and 35% PA. Bond strength was quantitatively evaluated by microtensile test (1.0 mm/min). Data were submitted to statistical analysis using ANOVA and Tukey tests (alpha - 0.05). Results: Bond strength values (MPa) were G1, 26.17 +/- 4.44; G2, 28.87 +/- 3.94; G3, 17.25 +/- 4.58; G4, 21.93 +/- 5.02; G5, 16.69 +/- 2.31; and G6, 29.06 +/- 8.31. There was no statistically significant difference among groups G1, G2, and G6 (p - 0.119), which presented higher bond strength than group G4, followed by groups G3 and G5. Conclusion: Er:YAG irradiation of bleached surfaces may favor bonding procedures when performed 24 h after bleaching.

Influence of pulse repetition rate on temperature rise and working time during composite filling removal with the Er : YAG laser

Objective: The purpose of this study was to assess the efficacy of Er:YAG laser energy for composite resin removal and the influence of pulse repetition rate on the thermal alterations occurring during laser ablation. Materials and Methods: Composite resin filling was placed in cavities (1.0 mm deep) prepared in bovine teeth and the specimens were randomly assigned to five groups according to the technique used for composite filling removal. In group I (controls), the restorations were removed using a high-speed diamond bur. In the other groups, the composite fillings were removed using an Er: YAG laser with different pulse repetition rates: group 2-2 Hz; group 3-4 Hz; group 4-6 Hz; and group 5-10 Hz. The time required for complete removal of the restorative material and the temperature changes were recorded. Results: Temperature rise during composite resin removal with the Er: YAG laser occurred in the substrate underneath the restoration and was directly proportional to the increase in pulse repetition rate. None of the groups had a temperature increase during composite filling removal of more than 5.6 degrees C, which is considered the critical point above which irreversible thermal damage to the pulp may result. Regarding the time for composite filling removal, all the laser-ablated groups (except for group 5 [10 Hz]) required more time than the control group for complete elimination of the material from the cavity walls. Conclusion: Under the tested conditions, Er: YAG laser irradiation was efficient for composite resin ablation and did not cause a temperature increase above the limit considered safe for the pulp. Among the tested pulse repetition rates, 6 Hz produced minimal temperature change compared to the control group (high-speed bur), and allowed composite filling removal within a time period that is acceptable for clinical conditions.

Imprinted gene expression in in vivo- and in vitro-produced bovine embryos and chorio-allantoic membranes

Cloning by nuclear transfer is often associated with poor results due to abnormal nuclear reprogramming of somatic donor cells and altered gene expression patterns. We investigated the expression patterns of imprinted genes IGF2 and IGF2R in 33- to 36-day bovine embryos and chorio-allantoic membranes derived from in vivo- and in vitro-produced embryos by somatic cell nuclear transfer (SCNT), parthenogenetic activation, and in vitro fertilization (IVF). There was a lower IGF2 expression rate in the SCNT (0.19) and parthenogenetic (0.02) groups when compared to in vivo and IVF embryos (2.01; P < 0.05). In the chorio-allantoic membranes, IGF2 showed a baseline expression pattern (P < 0.05) in parthenotes (0.001) when compared to in vivo, IVF (3.13), and SCNT (0.98) groups. IGF2R was less expressed (P < 0.05) in SCNT chorio-allantoic membranes (0.25) when compared to the in vivo group. The low expression of IGF2 in parthenogenetic embryos and chorio-allantoic membranes confirms its imprinted status in cattle. Alterations in the relative frequency of IGF2 and IGF2R transcripts were observed in SCNT-derived bovine embryos and chorioallantoic membranes, respectively, supporting the hypothesis that abnormalities in the expression of imprinted genes are causes of the low efficiency of SCNT procedures in this species.

Effects of polymorphisms of LHR and FSHR genes on sexual precocity in a Bos taurus x Bos indicus beef composite population

The purpose of the present research was to investigate the effects of polymorphisms of luteinizing hormone receptor (LHR) and follicle-stimulating hormone receptor (FSHR) genes, evaluated by polymerase chain reaction-restriction fragment length polymorphism in European-Zebu composite beef heifers from six different breed compositions. The polymorphism site analysis from digestion with HhaI and AluI restriction endonucleases allowed the genotype identification for LHR (TT, CT and CC) and FSHR (GG, CG and CC) genes. A high frequency of heterozygous animals was recorded in all breed compositions for both genes, except in two compositions for LHR. The probability of pregnancy (PP) at first breeding was used to evaluate the polymorphism effect on sexual precocity. The PP was analyzed as a binary trait, with a value of 1 (success) assigned to heifers that were diagnosed pregnant by rectal palpation and a value of 0 (failure) assigned to those that were not pregnant at that time. Heterozygous heifers showed a higher pregnancy rate (67 and 66% for LHR and FSHR genes, respectively), but no significant effects were observed for the genes studied (P=0.9188 and 0.8831 for LHR and FSHR, respectively) on the PP. These results do not justify the inclusion of LHR and FSHR restriction fragment length polymorphism markers in selection programs for sexual precocity in beef heifers. Nevertheless, these markers make possible the genotype characterization and may be used in additional studies to evaluate the genetic structure in other bovine populations.

Silica-based cationic bilayers as immunoadjuvants

Background: Silica particles cationized by dioctadecyldimethylammonium bromide (DODAB) bilayer were previously described. This work shows the efficiency of these particulates for antigen adsorption and presentation to the immune system and proves the concept that silica-based cationic bilayers exhibit better performance than alum regarding colloid stability and cellular immune responses for vaccine design. Results: Firstly, the silica/DODAB assembly was characterized at 1 mM NaCl, pH 6.3 or 5 mM Tris. HCl, pH 7.4 and 0.1 mg/ml silica over a range of DODAB concentrations (0.001-1 mM) by means of dynamic light scattering for particle sizing and zeta-potential analysis. 0.05 mM DODAB is enough to produce cationic bilayer-covered particles with good colloid stability. Secondly, conditions for maximal adsorption of bovine serum albumin (BSA) or a recombinant, heat-shock protein from Mycobacterium leprae (18 kDa-hsp) onto DODAB-covered or onto bare silica were determined. At maximal antigen adsorption, cellular immune responses in vivo from delayed-type hypersensitivity reactions determined by foot-pad swelling tests (DTH) and cytokines analysis evidenced the superior performance of the silica/DODAB adjuvant as compared to alum or antigens alone whereas humoral response from IgG in serum was equal to the one elicited by alum as adjuvant. Conclusion: Cationized silica is a biocompatible, inexpensive, easily prepared and possibly general immunoadjuvant for antigen presentation which displays higher colloid stability than alum, better performance regarding cellular immune responses and employs very low, micromolar doses of cationic and toxic synthetic lipid.

Phase transitions and spatially ordered counterion association in ionic-lipid membranes: A statistical model

We propose a statistical model to account for the gel-fluid anomalous phase transitions in charged bilayer- or lamellae-forming ionic lipids. The model Hamiltonian comprises effective attractive interactions to describe neutral-lipid membranes as well as the effect of electrostatic repulsions of the discrete ionic charges on the lipid headgroups. The latter can be counterion dissociated (charged) or counterion associated (neutral), while the lipid acyl chains may be in gel (low-temperature or high-lateral-pressure) or fluid (high-temperature or low-lateral-pressure) states. The system is modeled as a lattice gas with two distinct particle types-each one associated, respectively, with the polar-headgroup and the acyl-chain states-which can be mapped onto an Ashkin-Teller model with the inclusion of cubic terms. The model displays a rich thermodynamic behavior in terms of the chemical potential of counterions (related to added salt concentration) and lateral pressure. In particular, we show the existence of semidissociated thermodynamic phases related to the onset of charge order in the system. This type of order stems from spatially ordered counterion association to the lipid headgroups, in which charged and neutral lipids alternate in a checkerboard-like order. Within the mean-field approximation, we predict that the acyl-chain order-disorder transition is discontinuous, with the first-order line ending at a critical point, as in the neutral case. Moreover, the charge order gives rise to continuous transitions, with the associated second-order lines joining the aforementioned first-order line at critical end points. We explore the thermodynamic behavior of some physical quantities, like the specific heat at constant lateral pressure and the degree of ionization, associated with the fraction of charged lipid headgroups.

DNA-based ionic conducting membranes

Deoxyribonucleic acid based gel solid electrolytes were prepared and their electric properties were characterized. Their ionic conductivity is in the range of 10(-4)-10(-5) S/cm at room temperature and increases linearly in function of temperature, obeying an Arrhenius-like relationship. The present study, combined with the literature data, suggests that the electrical conduction mechanism in these membranes involve ion motion and/or charge hopping, promoted most likely by a significant interaction between the membrane components. The good conductivity results, as found here, together with the good transparency and good adhesion to the electrodes show that the DNA-based gel polymer electrolytes are very promising materials for application in various electrochromic devices. (C) 2011 American Institute of Physics. [doi: 10.1063/1.3610951]

Iridium(III)-surfactant complex immobilized in mesoporous silica via templated synthesis: a new route to optical materials

In this work we report the preparation of a new blue-emitting material based on the templated synthesis of mesoporous silica (MCM-41) using micellar solutions of the newly synthesized monocationic metallosurfactant complex bis[1-benzyl-4-(2,4-difluorophenyl)-1H-1,2,3-triazole](4,4'-diheptadecyl-2,2'- bipyridine)-iridium(III) chloride in hexadecyl-trimethyl-ammonium bromide (CTAB). Under ambient conditions, significant increases in excited state lifetime and quantum yield values (up to 45%), were obtained for the solid materials in comparison to the corresponding micellar solutions. Solid state (1)H and (19)F NMR spectroscopies were successfully employed for quantifying the luminophore content in terms of Ir-surfactant to CTAB and Ir-surfactant to silica ratios.

Enhancement of hematoporphyrin IX potential for photodynamic therapy by entrapment in silica nanospheres

The entrapment of hematoporphyrin IX (Hp IX) in silica by means of a microemulsion resulted in silica spheres of 33 +/- 6 nm. The small size, narrow size distribution and lack of aggregation maintain Hp IX silica nanospheres stable in aqueous solutions for long periods and permit a detailed study of the entrapped drug by different techniques. Hp IX entrapped in the silica matrix is accessed by oxygen and upon irradiation generates singlet oxygen which diffuses very efficiently to the outside solution. The Hp IX entrapped in the silica matrix is also reached by iron(II) ions, which causes quenching of the porphyrin fluorescence emission. The silica matrix also provides extra protection to the photosensitizer against interaction with BSA and ascorbic acid, which are known to cause suppression of singlet oxygen generation by the Hp IX free in solution. Therefore, the incorporation of Hp IX molecules into silica nanospheres increased the potential of the photosensitizer to perform photodynamic therapy.

Characterization of dynamic solid phase DNA extraction from blood with magnetically controlled silica beads

A novel solid phase extraction technique is described where DNA is bound and eluted from magnetic silica beads in a manner where efficiency is dependent on the magnetic manipulation of the beads and not on the flow of solution through a packed bed. The utility of this technique in the isolation of reasonably pure, PCR-amplifiable DNA from complex samples is shown by isolating DNA from whole human blood, and subsequently amplifying a fragment of the beta-globin gene. By effectively controlling the movement of the solid phase in the presence of a static sample, the issues associated with reproducibly packing a solid phase in a microchannel and maintaining consistent flow rates are eliminated. The technique described here is rapid, simple, and efficient, allowing for recovery of more than 60% of DNA from 0.6 mu L of blood at a concentration which is suitable for PCR amplification. In addition, the technique presented here requires inexpensive, common laboratory equipment, making it easily adopted for both clinical point-of-care applications and on-site forensic sample analysis.

Characterization of nickel-niobium composite electrocoatings

The electrodeposition of nickel based composites is been performed in order to improve properties of nickel layers, such as hardness, wear resistance, lubrication, corrosion resistance and catalytic activity. In the present work Nb powders (20 mu m average size) and Ni were codeposited on 1020 carbon steel by galvanostatic electrolysis of Watts bath, using 10, 20 and 40 mA/cm(2) cathodic current density and 240, 400 and 550 rpm electrolyte stirring rate. The morphology and texture of the coatings, Nb incorporated volume fraction, microhardness, adhesion to the substrate and corrosion behavior were evaluated. The Ni-Nb composite layers presented a rough morphology with randomly oriented Ni grains, whereas pure Ni coatings were smooth and showed highly preferred orientation in the [110] or [100] direction. The volume fraction of Nb in the composites determined by image analysis ranged from 8.5 to 19%. The 400 rpm stirring rate led to the highest Nb content (16 to 19016) for all current densities investigated The microhardness of the composite layers was higher than that of pure Ni coatings due to refining of Ni grains induced by incoporation of Nb particles. The adhesion of the coatings estimated qualitatively by bend test was found satisfactory. The Ni-Nb composites presented lower corrosion rate than Ni coatings in both 3% NaCl and 20% H2SO4 solutions.

Composite materials obtained from textile fiber residue

This article presents the use of fibers residue from textile industry to minimize environmental problems associated with material accumulation. Composite materials utilizing textile fiber residues and high density polyethylene were prepared. Effect of treatment with hot water on fibers to prepare composites was studied to provide an improvement in mechanical properties of these materials. This treatment on fibers was evaluated by X-ray diffraction and scanning electron microscopy techniques. Experimental results of mechanical properties indicated higher mechanical strength for treated fiber composites compared to the untreated fiber composites.

Immobilization and stabilization of microbial lipases by multipoint covalent attachment on aldehyde-resin affinity: Application of the biocatalysts in biodiesel synthesis

Microbial lipase preparations from Thermomyces lanuginosus (TLL) and Pseudomonas fluorescens (PFL) were immobilized by multipoint covalent attachment on Toyopearl AF-amino-650M resin and the most active and thermal stable derivatives used to catalyze the transesterificanon reaction of babassu and palm oils with ethanol in solvent-free media For this different activating agents mainly glutaraldehyde glycidol and epichlorohydrin were used and immobilization parameters were estimated based on the hydrolysis of olive oil emulsion and butyl butyrate synthesis ILL immobilized on glyoxyl-resin allowed obtaining derivatives with the highest hydrolytic activity (HA(der)) and thermal stability between 27 and 31 times more stable than the soluble lipase Although PFL derivatives were found to be less active and thermally stables similar formation of butyl butyrate concentrations were found for both ILL and PFL derivatives The highest conversion into biodiesel was found in the transesterification of palm oil catalyzed by both ILL and PFL glyoxyl-derivatives (c) 2010 Elsevier B V All rights reserved

Electrodeposition and characterization of Cu-Nb composite coatings

Copper coatings containing well-distributed Nb particles were obtained by co-electrodeposition in an acidic sulfate bath. Nb particle concentration in the bath was the most significant factor for the incorporation of Nb particles in copper, followed by stirring rate, whereas current density presented low significance. High Nb particle concentration and low stirring rate led to a higher incorporated Nb particle content. The microhardness of the composite layers was higher than that of pure copper deposits obtained under the same conditions due to copper matrix grain refinement and increased with the increase of both current density and incorporated Nb particle volume fraction. The corrosion resistance of Cu-Nb composites in 0.5 wt.% H(2)SO(4) solution at room temperature was higher than that of pure copper and increased with the increase of the Nb content. (C) 2010 Elsevier B.V. All rights reserved.

Enzymatic synthesis of monoglycerides by esterification reaction using Penicillium camembertii lipase immobilized on epoxy SiO(2)-PVA composite

Glycerol-fatty acid esterification has been conducted with lipase from Penicillium camembertii lipase immobilized on epoxy SiO(2)-PVA in solvent-free media, with the major product being 1-monoglyceride, a useful food emulsifier. For a given set of initial conditions, the influence of reaction was measured in terms of product formation and selectivity using different fatty acids as acyl donors. Results were found to be relatively dependent of the chain length of the fatty acids, showing high specificity for both myristic and palmytic acids attaining final mixture that fulfills the requirements established by the World Health Organization to be used as food emulsifiers. (C) 2010 Elsevier B.V. All rights reserved.