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50 results on '"Mohamed, Ahmed A. S."'

49. Synthesis and reactions of 3-hydrazino-2,7,8,9-tetrahydro-1Hbenzo[ 6',7']cyclohepta[1',2':4,5]pyrido[2,3-d]pyrimidin-1-one.

Author

Mohamed Ahmed, Mohamed S. and Farghaly, Thoraya A.

Subjects
*HYDRAZONES, *PHENYLHYDRAZINE, *PYRAZOLES, *RING formation (Chemistry), *HYDRAZINE, *ALDEHYDES, *ACETIC acid, *KETONES, *PYRIMIDINES
Abstract

3-Hydrazino-2,7,8,9-tetrahydro-1H-benzo [6′,7′]cyclohepta[1′,2′:4,5] pyrido[2,3-d] pyrimidin-1-one (5) was prepared in good yield by reaction of 3 or 4 with hydrazine hydrate under reflux. Reaction of compound 5 with different aldehydes in acetic acid gave the corresponding hydrazono derivatives 7. Cyclization of the latter compounds with bromine in acetic acid afforded a series of novel pentacyclic compounds namely, 5,6,7,11-tetrahydro-15H-benzo[ 6″',7″']cyclohepta[1″',2″:4′,5′]pyrido[2′,3′-d][1,2,4] triazolo[4,3-a]pyrimidin-15-ones (11af). In addition, reaction of compound 5 with β-diketones and a-diketone were investigated. The structures of the so formed compounds were confirmed by elemental and spectral analyses (¹H NMR, 13C NMR, IR and MS). [ABSTRACT FROM AUTHOR]

Published
2009

50. Evaluation of the remineralizing effect of the chicken eggshell paste after removal of the fixed orthodontic appliance: An in vitro study.

Author

Fathy Abo-Elmahasen MM, Shaaban AM, Elsaharty M, Mohamed AAS, Assadawy MI, and El Sayed IS

Abstract

Background: Demineralization of the enamel surface, which appears as white spot lesions during and after removal of the fixed orthodontic appliance, is the most common disadvantage of the orthodontic treatment course. Using the remineralizing agents during and after orthodontic treatment helps to avoid those enamel defects., Objective: The present study aims to assess the remineralizing effect of the chicken eggshell powder on the demineralized enamel surfaces after debonding the orthodontic bracket system., Materials and Methods: The current study was performed on 80 prepared premolar crowns embedded into acrylic molds. The samples were prepared to receive routine steps of the bonding process for the bracket system. The paste of the chicken eggshell powder was added to the samples after the debonding process. Scanning electron microscopy (SEM) and energy-dispersive X-ray (EDX) were used to evaluate the remineralization effect of the chicken eggshell powder. Also, the Vickers microhardness tester was used to assess the enamel surface microhardness., Results: It was found that the mean value of the Ca/P ratio for the samples before bonding of the orthodontic bracket system was (4.17 ± 2.2). This value significantly decreased to (2 ± 1.3) after debonding of the orthodontic bracket system and then showed a significant increase to (4.79 ± 2.65) after remineralization. These results were assured by the values of the Vickers microhardness tester., Conclusion: The chicken eggshell powder has an excellent remineralization effect for the demineralized enamel surface after debonding the orthodontic enamel surface., Competing Interests: There are no conflicts of interest., (Copyright: © 2024 Journal of Orthodontic Science.)

Published
2024
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