Background: The present study was conducted to evaluate the effects of different bleaching methods on the shear bond strength of orthodontic Sapphire brackets bonded to human premolars teeth using light cured composite resin and to determine the predominant site of bond failure. Materials and Methods: Thirty freshly extracted human premolars were selected and randomly divided into three groups (10 per group). These groups are: control (unbleached) group, hydrogen peroxide group (HP) 37.5% ; which is the in- office bleaching method group, carbamide peroxide group (CP) 16%; which is the at- home bleaching method group. After bleaching process was performed, all the teeth stored in distilled water in a sealed container at room temperature for 24 hours before bonding was initiated, then orthodontic brackets were bonded with a light cure composite resin, stored in distilled water at room temperature for another 24 hours before debonding then the brackets de-bonded and tested for shear bond strength using an Instron universal testing machine. For adhesive remnant index (ARI) the enamel surface and bracket base of each tooth were inspected under magnifying lens (20X) of a stereomicroscope. Results and Conclusions: Non-statistically significant differences of shear bond strengths were found between the control group and the bleached groups, the dental bleaching in both methods did not affect the SBS of Sapphire brackets. The mode of failure was mostly between the adhesive and the enamel and the bond failure between the bracket base and the adhesive were also observed. Keywords: Shear bond strength, tooth bleaching agents, orthodontic brackets, dental bonding.
Structure type and disorder have become important questions in catalyst design, with the most active catalysts often noted to be “disordered” or “amorphous” in nature. To quantify the effects of disorder and structure type systematically, a test set of manganese(III,IV) oxides was developed and their reactivity as oxidants and catalysts tested against three substrates: methylene blue, hydrogen peroxide, and water. We find that disorder destabilizes the materialsthermodynamically, making them stronger chemical oxidantsbut not necessarily better catalysts. For the disproportionation of H2O2 and the oxidative decomposition of methylene blue, MnOx-mediated direct oxidation competes with catalytically mediated oxidation, making the most
... Show MoreIn this study , the effect of an organic compound prepared as derivative of oxazepine tested on the activities of aspartate amino trasferase (AST) and alanin amino transferase (ALT). The kinetic study of such enzymes is in the presence of oxazepine derivative. The results revealed that the organic compound is a non competitive inhibitor for both enzymes. The Km value for AST is 1.3 × 10-3 M and Vmax for the uninhibited is 200 U/mL and for the inhibited is 111.1 U/mL while Km value for ALT is 2.5 × 10-3 M and Vmax are 89.66 U/mL and 56.77 U/mL for the uninhibited and inhibited enzyme respectively.
The compound [L] was produced in the current study through the reaction of 4-aminoacetophenon with 4-methoxyaniline in the cold, concentrated HCl with 10% NaNO2. Curcumin, several transition metal complexes (Ni (II), La (III), and Hg (II)), and compound [L] were combined in EtOH to create new complexes. UV-vis spectroscopy, FTIR, AA, TGA-DSC, conductivity, chloride content, and elemental analysis (CHNS) were used to describe the structure of produced complexes. Biological activities against fungi, S. aureus (G+), Pseudomonas (G-), E. coli (G-), and Proteus (G-) were demonstrated using complexes. Depending on the outcomes of the aforementioned methods, octahedral formulas were given as the geometrical structures for each created comp
... Show MoreIn this study new derivatives of O-[2-{''2-Substituted Aryl (''1,''3,''4 thiadiazolyl) ['3,'4-b]-'1,'2,'4- Triazolyl]-Ethyl]-p- chlorobenzald oxime (6-11)have been synthesized from the starting material p-chloro – E- benzaldoxime 1.Compound 2 was synthesized by the reaction of p-chloro – E- benzaldoxime with ethyl acrylate in basic medium. Refluxing compound 2 with hydrazine hydrate in ethanol absolute afforded 3. Derivative 4 was prepared by the reaction of 3 with carbon disulphide, treated of compound 4 with hydrazine hydrate gave 5. The derivatives (6-11) were prepared by the reaction of 5 with different substitutesof aromatic acids. The structures of these compounds were characterized from their melting points, infrared spectroscopy
... Show MoreThe complexes of the 2-hydroxy-4-Nitro phenyl piperonalidene with metal ions Cr(III), Ni(II), Pt(IV) and Zn(II) were prepared in ethanolic solution. These complexes were characterized by spectroscopic methods, conductivity, metal analyses and magnetic moment measurements. The nature of the complexes formed in ethanolic solution was study following the molar ratio method. From the spectral studies, monomer structures proposed for the nickel (II) and Zinc (II) complexes while dimeric structures for the chromium (III) and platinum (IV) were proposed. Octahedral geometry was suggested for all prepared complexes except zinc (II) has tetrahedral geometry, Structural geometries of these compounds were also suggested in gas phase by using
... Show MoreAccelerates operating managements in the facilities contemporary business environment toward redefining processes and strategies that you need to perform tasks of guaranteeing them continue in an environment performance dominated by economic globalization and the circumstances of uncertainty attempt the creation of a new structure through multiple pages seek to improve profitability and sustainable growth in performance in a climatefocuses on the development of institutional processes, reduce costs and achieve customer satisfaction to meet their demands and expectations are constantly changing. The research was presented structural matrix performance combines methodology Alsigma in order to improve customer satisfaction significantly bet
... Show MoreA theoretical calculation of the binding and excitation energies have been used at low – lying energies based on shell model and quantum theory. In this model, we evaluated the energies under assume Ni 28 56 30 as inert core with two nucleon extra, nucleons in the 2P3/2 , 1f 5/2 and 2P1/2 configuration. Modified Surface Delta Interaction (MSDI) and Reid's Potential (RP) theory for two body matrix elements are evaluated by using a Matlab program to calculate the energies of experimental and Reid single particle energies. Our results of the theoretical calculation have been compared with the experimental results, which show no good agreement with the experiment but have a good agreement wit
... Show MoreEthylenediamine was reacted in the first step with 2,5 – hexandion to produce the precursor [A] , then [A] was reacted with diethylmalonate to give the new tetradentate macrocyclic Ligand [H2L].This Ligand was reacted with some metal ions in ethanol to give a series of new metal complexes of the general formula [M(HnL)X]m ( where : M= CrIII , n = 0 , X= Cl2 , m= -1 ; M = MnII , FeII , NiII , CuII , n = 1 , X= Cl2 , m = -1 ; M = CoII , n = 0 , X = Cl , m = -1 ; M = PdII , n = 0 , X=0 , m = 0 ; M = CdII , n = 2 , X = 0 , m = +2 . All compounds were characterize
... Show MoreThis work represents the preparation of the starting material, 3-chloro-2-oxo-1,4-dithiacyclohexane (S) using a new method. This material was reacted with, 4-phenylthiosemicarbazide to give (H3NS3) as a tetradentate ligand H3L. New complex of rhenium (V) with this ligand of the formula [ReO(L)] was prepared. New complexes of the general formula [M(HL)] of this ligand when reacted with some metal ions where: M = Ni(II), Cu(II), Cd(II), Zn(II), Hg(II) have been reported. The ligand and the complexes were characterized by infrared, ultraviolet–visible, mass, 1H nuclear magnetic resonance and atomic absorption spectroscopic techniques and by (HPLC), elemental analysis, and electrical conductivity. The proposed structure for H3L with Re (V) i
... Show MoreThe research aims to shed light on the obstacles that hinder the use of taxpayers' commercial books covered by provisions of the amended commercial book-keeping system No. 2 of 1985 and ways to address these obstacles. On this basis, the main null hypothesis was formulated that there is no statistically significant relationship between the obstacles to the adoption of the commercial books and taxable income.
The research data were collected on the base of three applied case studies of registered taxpayers in the General Commission of Taxes, GCT, together with the use of a questionnaire distributed to a sample of taxpayers ( companies ). The collected data were analyzed, the result were presented and the hypothesis was
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