351 results on '"Souza, Rodrigo O. A."'
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152. ChemInform Abstract: Copper‐Free Sonogashira Reaction Using Gold Nanoparticles Supported on Ce2O3, Nb2O5 and SiO2 under Microwave Irradiation.
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de Souza, Rodrigo O. M. A., primary, Bittar, Mariana S., additional, Mendes, Laiza V. P., additional, da Silva, Carla Michele F., additional, Teixeira da Silva, Victor, additional, and Antunes, O. A. C., additional more...
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- 2008
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153. ChemInform Abstract: Morita—Baylis—Hillman Reaction in Water/Ionic Liquids under Microwave Irradiation.
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de Souza, Rodrigo O. M. A., primary, de Souza, Andrea L. F., additional, Fernandez, Tatiana L., additional, Silva, Aires C., additional, Pereira, Vera L. P., additional, Esteves, Pierre M., additional, Vasconcellos, Mario L. A. A., additional, and Antunes, Octavio A. C., additional more...
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- 2008
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154. Resin Bonding to Root Canal Dentin: Effect of the Application of an Experimental Hydrophobic Resin Coating after an All-in-one Adhesive
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Bottino, Marco Antonio, primary, Lombardo, Geraido H. L., additional, Souza, Rodrigo O. A., additional, Michida, Silvia M. A, additional, de Melo, Renata Marques, additional, and Valendro, Luiz Felipe, additional more...
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- 2008
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155. Hexamethylenetetramine-Ionic Liquids Catalyzed Baylis—Hillman Reactions.
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de Souza, Rodrigo O. M. A., primary, Fregadolli, Pedro H., additional, Goncalves, Karen M., additional, Sequeira, Lucia C., additional, Pereira, Vera L. P., additional, Filho, Lucio C., additional, Esteves, Pierre M., additional, Vasconcellos, Mario L. A. A., additional, and Antunes, Octavio A. C., additional more...
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- 2007
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156. Enhanced production of fructose ester by biocatalyzed continuous flow process.
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Sutili, Felipe K., Ruela, Halliny S., De O. Nogueira, Daniel, Leal, Ivana C. R., Miranda, Leandro S. M., and De Souza, Rodrigo O. M. A.
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PHOSPHOFRUCTOKINASES ,FRUCTOSE intolerance ,CATALYSIS ,CATALYSTS ,CHEMICAL reactions ,CHEMICAL synthesis ,CHEMICAL processes ,CHEMICAL engineering - Abstract
Background: Fatty acid sugar esters are non-toxic, odorless, non-irritanting surfactants. They can be synthesized by renewable resources and are completely biodegradable in aerobic and anaerobic conditions. Their application has been expanded in innumerous areas including pharmaceuticals, cosmetics, detergents and food industry. Lipase-catalyzed esterification have been investigated as a potential substitute to the traditional chemical, demanding milder reaction conditions, allowing better reaction control and providing higher-quality products. So, the lipase catalyzed sugar ester synthesis becomes an interesting strategy for producing biodegradable, non- ionic surfactants. The main disadvantage of this protocol is the poor solubility of substrates and long reaction time required for performed the esterification reaction with moderated to good yields. Results: Here in, we report the enzymatic esterification of steric hindered fructose derivative with free fatty acids derived from palm oil refining process (RePO) under continuous flow conditions at concentrations up to 0.5 M, increasing the productivity up to 100 mg. min
-1 .g immob. enzyme-1 . Conclusions: The immobilized commercial enzyme from Rhizomucor miehei generated the best performance between the catalysts tested. [ABSTRACT FROM AUTHOR] more...- Published
- 2015
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157. Allenediazonium ions and their protonation chemistry: a DFT study
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de Souza, Rodrigo O. M. A., primary, Esteves, Pierre M., additional, and Laali, Kenneth K., additional
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- 2006
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158. Modelagem para o dimensionamento de microtubos em irrigação localizada
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Souza, Rodrigo O. R. de M., primary and Botrel, Tarlei A., additional
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- 2004
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159. SYNTHESIS OF 4-ACYL-1H-1,2,3-TRIAZOLIC NUCLEOSIDES
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Cunha, Anna C., primary, Pereira, Letícia O. R., additional, de Souza, Rodrigo O. P., additional, de Souza, Maria Cecília B. V., additional, and Ferreira, Vitor F., additional
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- 2001
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160. ChemInform Abstract: A Two‐Step Synthesis of 1,2,3‐Substituted Pyrroles.
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Cunha, Anna C., primary, Pereira, Leticia O. R., additional, de Souza, Rodrigo O. P., additional, de Souza, Maria Cecilia B. V., additional, and Ferreira, Vitor F., additional
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- 2000
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161. A Two Step Synthesis of 1,2,3-Substituted Pyrroles
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Cunha, Anna C., primary, Pereira, Leticia O.R., additional, de Souza, Rodrigo O. P., additional, de Souza, Maria Cecilia B. V., additional, and Ferreira, Vitor F., additional
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- 2000
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162. Influence of air-particle deposition protocols on the surface topography and adhesion of resin cement to zirconia.
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Sarmento, Hugo R., Campos, Fernanda, Sousa, Rafael S., Machado, Joao P. B., Souza, Rodrigo O. A., Bottino, Marco A., and Özcan, Mutlu
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SEDIMENTATION & deposition ,SURFACE topography ,ADHESION ,ZIRCONIUM oxide ,ALUMINUM oxide ,SCANNING electron microscopy ,SHEAR strength ,YTTRIA stabilized zirconium oxide - Abstract
Objectives. This study evaluated the influence of air-particle abrasion protocols on the surface roughness (SR) of zirconia and the shear bond strength (SBS) of dual-polymerized resin cement to this ceramic. Materials and methods. Sintered zirconia blocks ( n = 115) (Lava, 3M ESPE) were embedded in acrylic resin and polished. The specimens were divided according to the 'particle type' (Al: 110 µm Al
2 O3 ; Si: 110 µm SiO2 ) and 'pressure' factors (2.5 or 3.5 bar) ( n = 3 per group): (a) Control (no air-abrasion); (b) Al2.5; (c) Si2.5; (d) Al3.5; (e) Si3.5. SR (Ra) was measured 3-times from each specimen after 20 s of air-abrasion (distance: 10 mm) using a digital optical profilometer. Surface topography was evaluated under SEM analyses. For the SBS test, 'particle type', 'pressure' and 'thermocycling' (TC) factors were considered ( n = 10; n = 10 per group): Control (no air-abrasion); Al2.5; Si2.5; Al3.5; Si3.5; ControlTC ; Al2.5TC ; Si2.5TC ; Al3.5TC ; Si3.5TC . After silane application, resin cement (Panavia F2.0) was bonded and polymerized. Specimens were thermocycled (6.000 cycles, 5-55°C) and subjected to SBS (1 mm/min). Data were analyzed using ANOVA, Tukey's and Dunnett tests (5%). Results. 'Particle' ( p = 0.0001) and 'pressure' ( p = 0.0001) factors significantly affected the SR. All protocols significantly increased the SR (Al2.5: 0.45 ± 0.02; Si2.5: 0.39 ± 0.01; Al3.5: 0.80 ± 0.01; Si3.5: 0.64 ± 0.01 µm) compared to the control group (0.16 ± 0.01 µm). For SBS, only 'particle' factor significantly affected the results ( p = 0.015). The SiO2 groups presented significantly higher SBS results than Al2 O3 (Al2.5: 4.78 ± 1.86; Si2.5: 7.17 ± 2.62; Al3.5: 4.97 ± 3.74; Si3.5: 9.14 ± 4.09 MPa) and the control group (3.67 ± 3.0 MPa). All TC specimens presented spontaneous debondings. SEM analysis showed that Al2 O3 created damage in zirconia in the form of grooves, different from those observed with SiO2 groups. Conclusions. Air-abrasion with 110 µm Al2 O3 resulted in higher roughness, but air-abrasion protocols with SiO2 promoted better adhesion. [ABSTRACT FROM AUTHOR] more...- Published
- 2014
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163. Lipase-Catalyzed Monostearin Synthesis under Continuous Flow Conditions.
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Junior, Ivaldo I., Flores, Marcela C., Sutili, Felipe K., Leite, Selma G. F., de M. Miranda, Leandro S., Leal, Ivana C. R., and de Souza, Rodrigo O. M. A.
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- 2012
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164. Copper-Free Sonogashira Reaction Using Gold Nanoparticles Supported on Ce2O3, Nb2O5 and SiO2 under Microwave Irradiation.
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de Souza, Rodrigo O., Bittar, Mariana S., Mendes, Laiza V., da Silva, Carla Michele, da Silva, Victor Teixeira, and Antunes, O. A.
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GOLD nanoparticles , *SONOGASHIRA reaction , *COPPER catalysts , *COUPLING reactions (Chemistry) , *ACETYLENE , *IRRADIATION - Abstract
In the present communication we wish to report a copper-free Sonogashira reaction catalyzed by gold-supported catalysts under microwave irradiation. Aryl and alkyl acetylenes were used and good yields were obtained with short reaction times when DMF was used as solvent. Three different supported gold catalysts were used and Au/SiO2 gave the best result for both aryl and alkyl acetylenes. [ABSTRACT FROM AUTHOR] more...
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- 2008
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165. Baylis–Hillman adducts with molluscicidal activity against Biomphalaria glabrata.
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Vasconcellos, Mário L. A. A., Silva, Tania M. S., Camara, Celso A., Martins, Rodrigo M., Lacerda, Kelly M., Lopes, Horacimone M., Pereira, Vera L. P., de Souza, Rodrigo O. M. A., and Crespo, Lívia T. C. more...
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EXPERIENTIAL research ,BIOMPHALARIA ,BIOMPHALARIA glabrata ,SNAILS ,MOLLUSKS ,GASTROPODA ,SCHISTOSOMIASIS ,ORGANIC compounds - Abstract
The molluscicidal activities often Baylis-Hillman adducts against Biomphalaria glabrata (Say) snails, the intermediate host of schistosomiasis, have been determined. Nine of these compounds showed significant molluscicidal activity against B. glabrata, falling below the threshold of 100 μg ml
-1 set for potential molluscicidal activity by the World Health Organisation. Among these compounds, 3-hydroxy-2-methylene-3-(4-nitrophenyl)propanenitrile had the highest activity, with LC50 = 6.64 μg ml-1 . [ABSTRACT FROM AUTHOR] more...- Published
- 2006
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166. Continuous Flow Synthesis of Hexyl Laurate Using Immobilized Thermomyces Lanuginosus Lipase from Residual Babassu Mesocarp.
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S. Lira, Regiane K., Nascimento, Marcelo A., Lima, Marcelo T., Georgii, Ana Débora N. P., Leão, Raquel A. C., Souza, Rodrigo O. M. A., Wojcieszak, Robert, Leite, Selma G. F., and Ivaldo, Itabaiana Jr
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ENZYMES , *FLOW chemistry , *LIGNOCELLULOSE , *WASTE recycling , *THERAPEUTIC immobilization , *LIPASES - Abstract
Brazil has one of the greatest biodiversities on the planet, where various crops play a strategic role in the country's economy. Among the highly appreciated biomasses is babassu, whose oil extraction generates residual babassu mesocarp (BM), which still needs new strategies for valorization. This work aimed to use BM as a support for the immobilization of
Thermomyces lanuginosus lipase (TLL) in an 8.83 mL packed‐bed reactor, followed by its application as a biocatalyst for the synthesis of hexyl laurate in an integrated process. Initially, the percolation of a solution containing 5 mg of TLL at 25 °C and flows ranging from 1.767 to 0.074 mL min−1 was investigated, where at the lowest flow rate tested (residence time of 2 h), it was possible to obtain an immobilized derivative with hydrolytic activity of 504.7 U g−1 and 31.7 % of recovered activity. Subsequent studies of treatment with n‐hexane, as well as the effect of temperature on the immobilization process, were able to improve the activities of the final biocatalyst BM‐TLLF, achieving a final hydrolysis activity of 7023 U g−1 and esterification activity of 430 U ⋅ g−1 against 142 U g−1 and 113.5 U g−1 respectively presented by the commercial TLIM biocatalyst. Desorption studies showed that the TL IM has 18 mg of protein per gram of support, compared to 4.92 mg presented by BM‐TLL. Both biocatalysts were applied to synthesize hexyl laurate, achieving 98 % conversion at 40 °C within 2 h. Notably, BM‐TLLF displayed exceptional recyclability, maintaining catalytic efficiency over 12 cycles. This reflects a productivity of 180 mg of product ⋅ h−1 U−1 of the enzyme, surpassing 46 mg h−1 U−1 obtained for TLIM. These results demonstrate the efficacy of continuous flow technology in creating a competitive and integrated process offering an exciting alternative for the valorization of residual lignocellulosic biomass. [ABSTRACT FROM AUTHOR] more...- Published
- 2024
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167. Use of renewable raw materials for biocatalytic continuous flow process
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Souza, Rodrigo O., Itabaiana, Ivaldo I., Miranda, Leandro S., Sutili, Felipe K., Ruela, H. S., and IVANA LEAL
168. Analysis of Tooth Enamel After Excessive Bleaching: A Study Using Scanning Electron Microscopy and Energy Dispersive X-ray Spectroscopy
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Souza, Rodrigo O. A., Lombardo, Geraldo H. L., Pereira, Sarina M. B., Zamboni, Sandra C., Marcia Carneiro Valera, Araujo, Maria A. M., Ozcan, Mutlu, Federal University of Paraíba, Universidade Estadual Paulista (UNESP), University of Zürich, and Clinic for Fixed and Removable Prosthodontics and Dental Materials Science more...
- Abstract
Made available in DSpace on 2022-04-28T21:00:31Z (GMT). No. of bitstreams: 0 Previous issue date: 2010-01-01 This study assessed alterations on bovine enamel after excessive bleaching. Coronal portions of bovine teeth (n = 30) were sectioned and divided into three groups (n = 10 per group). The coronal parts were further cut incisocervically into two halves. While one half received no bleaching (control), the other half was subjected to either one (group 1), three (group 2), or five bleaching sessions (group 3) with 35% hydrogen peroxide. The enamel surfaces were then analyzed using scanning electron microscopy and energy dispersive x-ray spectroscopy (EDS). Excessive bleaching affected the surface morphology and chemistry of the bovine enamel. EDS analysis showed the highest decrease in calcium ion percentages in groups 2 and 3 when compared to their nonbleached halves. Oxygen and phosphorus percentages were comparable on both the control and bleached enamel, regardless of the number of bleaching sessions. Consecutive bleaching sessions with 35% hydrogen peroxide may lead to morphologic and specific elemental changes when performed in a short period of time. Calcium ion percentages may decrease when this bleaching agent is used for more than one session. © 2010 by Quintessence Publishing Co Inc. Department of Restorative Dentistry Division of Prosthodontics Federal University of Paraíba, João Pessoa São Jose dos Campos Dental School São Paulo State University (UNESP), São José dos Campos Department of Restorative Dentistry São Jose dos Campos Dental School UNESP, São José dos Campos Department of Dental Materials and Prosthodontics São Jose dos Campos Dental School UNESP, São José dos Campos Center for Dental and Oral Medicine University of Zürich Dental Materials Unit Clinic for Fixed and Removable Prosthodontics and Dental Materials Science, Zürich São Jose dos Campos Dental School São Paulo State University (UNESP), São José dos Campos Department of Restorative Dentistry São Jose dos Campos Dental School UNESP, São José dos Campos Department of Dental Materials and Prosthodontics São Jose dos Campos Dental School UNESP, São José dos Campos more...
169. An Efficient Green Protocol for the Preparation of Acetoacetamides and Application of the Methodology to a One-Pot Synthesis of Biginelli Dihydropyrimidines. Expansion of Dihydropyrimidine Topological Chemical Space.
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Gama, Fernando H. S., de Souza, Rodrigo O. M. A., and Garden, Simon J.
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ACETAMIDE , *PYRIMIDINE synthesis , *DIOXINS - Abstract
The title acetoacetamides are obtained from various amine derivatives and dioxin-4-one by conventional and microwave-assisted heating. It is shown that the conventional heating gives better yields compared to the microwave heating, but the latter is not optimized. The acetoacetamides are utilized for the three-component one-pot synthesis of novel Biginelli dihydropyrimidine derivatives without purification. [ABSTRACT FROM AUTHOR] more...
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- 2016
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170. Combination of the Suzuki–Miyaura Cross‐Coupling Reaction with Engineered Transaminases.
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Dawood, Ayad W. H., Bassut, Jonathan, De souza, Rodrigo O. M. A., and Bornscheuer, Uwe T.
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COUPLING reactions (Chemistry) kinetics , *ORGANIC synthesis , *BIOCATALYSIS , *ALANINE aminotransferase , *ENANTIOMERS analysis - Abstract
The combination of enzymatic and chemical reaction steps is one important area of research in organic synthesis, preferentially as cascade reactions in one‐pot to improve total conversion and achieve high operational stability. Here, the combination of the Suzuki–Miyaura reaction is described to synthesize biaryl compounds followed by a transamination reaction. Careful optimization of the reaction conditions required for the chemo‐ and biocatalysis reaction enabled an efficient two‐step‐one‐pot reaction yielding the final chiral amines with excellent optical purity (>99 % ee) in up to 84 % total conversion. Key to the success was the protein engineering of the amine transaminases from Asperguillus fumigatus (4CHI‐TA) where single alanine mutations increased the conversion up to 2.3‐fold. Finally, the transfer to a continuous flow system after immobilization of the best 4CHI‐TA variant is demonstrated. The combination of amine transaminase (ATA) activity and the Suzuki–Miyaura cross‐coupling reaction in a two‐step‐one‐pot fashion is presented. The biaryl amines were obtained with high conversion and excellent enantiomeric excess (99 % ee) using isopropylamine as the amine donor after engineering of the transaminase from Asperguillus fumigatus. [ABSTRACT FROM AUTHOR] more...
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- 2018
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171. Asymmetric Synthesis of Chiral Halogenated Amines using Amine Transaminases.
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Dawood, Ayad W. H., Bornscheuer, Uwe T., and de Souza, Rodrigo O. M. A.
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AMINES , *AMINOTRANSFERASES , *ENZYMES , *KETONES , *ASPERGILLUS fumigatus , *ISOPROPYLAMINE , *DEHYDROGENASES - Abstract
Abstract: Amine transaminases (ATAs) are versatile and industrially relevant biocatalysts that catalyze the transfer of an amine group from a donor to an acceptor molecule. Asymmetric synthesis from a prochiral ketone is the most preferred route to the desired amine product, as it is obtainable in a theoretical yield of 100 %. In addition to the requirement of active and enantioselective ATAs, the choice of a suitable amine donor is also important to save costs and to avoid additional enzymes to shift the equilibrium and/or to recycle the cofactors. In this work, we identified suitable (
R )‐ and (S )‐ATAs fromAspergillus fumigatus andSilicibacter pomeroyi , respectively, to afford a set of halogen‐substituted derivatives of brominated or chlorinated 1‐phenyl‐2‐propanamine, 4‐phenylbutan‐2‐amine, and 1‐(3‐pyridinyl)ethanamine. Optimization of the donor–acceptor ratio enabled application of isopropylamine as an amine donor, which resulted in high conversions and amines with 73–99 %ee . [ABSTRACT FROM AUTHOR] more...- Published
- 2018
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172. ChemInform Abstract: The Morita-Baylis-Hillman Reaction in Aqueous-Organic Solvent System.
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de Souza, Rodrigo O. M. A., Pereira, Vera L. P., Esteves, Pierre M., and Vasconcellos, Mario L. A. A.
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- 2009
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173. ChemInform Abstract: Copper-Free Sonogashira Reaction Using Gold Nanoparticles Supported on Ce2O3, Nb2O5 and SiO2 under Microwave Irradiation.
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de Souza, Rodrigo O. M. A., Bittar, Mariana S., Mendes, Laiza V. P., da Silva, Carla Michele F., Teixeira da Silva, Victor, and Antunes, O. A. C.
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- 2008
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174. ChemInform Abstract: Synthesis of 4-Acyl-1H-1,2,3-triazolic Nucleosides.
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Cunha, Anna C., Pereira, Leticia O. R., de Souza, Rodrigo O. P., de Souza, Maria Cecilia B. V., and Ferreira, Vitor F.
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- 2002
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175. ChemInform Abstract: Copper‐Free Sonogashira Reaction Using Gold Nanoparticles Supported on Ce2O3, Nb2O5and SiO2under Microwave Irradiation.
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de Souza, Rodrigo O. M. A., Bittar, Mariana S., Mendes, Laiza V. P., da Silva, Carla Michele F., Teixeira da Silva, Victor, and Antunes, O. A. C.
- Abstract
ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option. more...
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- 2008
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176. α‐Ketobutyrate Production under Continuous‐Flow Conditions Catalyzed by Immobilized L‐Methionine γ‐Lyase.
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Jorge, Jessica M., de M. Silva, Marcus V., Brêda, Gabriela C., de Souza, Camilla P., Leão, Raquel A. C., Almeida, Rodrigo V., Bornscheuer, Uwe T., and de Souza, Rodrigo O. M. A.
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SULFUR amino acids , *COFACTORS (Biochemistry) , *WASTE recycling , *CYSTEINE , *ENZYMES , *CANCER cells , *ENCAPSULATION (Catalysis) - Abstract
l‐Methionine γ‐lyase (MGL) is a PLP‐dependent enzyme which catalyzes the α, γ‐elimination reaction in sulfur containing amino acids, such as L‐methionine and L‐cysteine. Its major applications are on metabolic restriction of methionine to cancer cells, food industry (cheese flavor) and for the synthesis of d and l‐homoalanine. Herein, we present the immobilization and use of this new immobilized biocatalyst under batch and continuous‐flow conditions. The best optimized continuous‐flow condition allowed 89 % conversion in 30 min of residence time with good recyclability of the biocatalyst. [ABSTRACT FROM AUTHOR] more...
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- 2022
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177. Oxidation of Benzene Catalyzed by 2,2′-Bipyridine and 1,10-Phenantroline Cu(II) Complexes.
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Detoni, Chaline, Carvalho, Nakédia, De Souza, Rodrigo O. M. A., Aranda, Donato A. G., and Antunes, O. A. C.
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OXIDATION , *BENZENE , *PHENOL , *BIPYRIDINE , *HYDROGEN peroxide , *CATALYSTS - Abstract
The use of mononuclear Cu(II) 2,2′-bipyridine and 1,10-phenantroline complexes as catalysts in the oxidation of benzene, using hydrogen peroxide and tert-butyl hydroperoxide as oxidant in CH3CN/H2O solution is presented. The reactions were carried out at 25 and at 50 °C. The complexes [Cu(bipy)3]Cl2 · 6H2O ( 1), [Cu(bipy)2Cl]Cl · 5H2O ( 2), [Cu(bipy)Cl2] ( 3), [Cu(phen)3]Cl2 · 7H2O ( 4), [Cu(phen)2Cl]Cl · 5H2O ( 5), [Cu(phen)Cl2] ( 6) were able to oxidize benzene into phenol, hydroquinone and p-benzoquinone. Highest conversion (22%) was obtained using [Cu(Phen)Cl2] ( 6) as catalyst. [ABSTRACT FROM AUTHOR] more...
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- 2009
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178. Continuous flow synthesis of the lamivudine precursor L-Menthyl Glyoxylate.
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Azevedo, Lais S. D., Aguillon, Anderson R., Lima, Marcelo T., Leão, Raquel A. C., and de Souza, Rodrigo O. M. A.
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LAMIVUDINE , *MALEIC anhydride , *FUMARATES , *OZONE generators , *OZONOLYSIS , *TENOFOVIR - Abstract
Lamivudine (3TC) is a drug in the antiretroviral class used to treat AIDS / HIV. Featuring two chiral centers, 3TC has two pairs of diastereomers, of which cis - (−) is the first option, as it has biological activity and is not cytotoxic. Due to the great demand for this compound, several synthetic routes were developed for its production. Among them, the enantioselective synthesis of lamivudine from L-menthyl-glyoxylate, which uses L-menthol as a chiral auxiliary, stands out. L-menthyl-glyoxylate is obtained by reacting menthol with some carboxyl derivatives, such as glyoxyl acid, maleic anhydride and fumaric acid. The present work aims to produce this basic component (L-menthyl glyoxylate) using alternative batch and continuous flow methodologies. The synthesis was carried out in two ways: a) from the esterification of menthol with maleic anhydride followed by ozonolysis of dimenthyl maleate and hydration; and b) starting from the esterification of menthol with fumaric acid to synthesize dimenthyl fumarate, followed by ozone and hydration. For all stages, conversions and selectivity above 90% were observed. The ozonolysis of dimenthyl maleate was transposed to continuous flow conditions resulting in conversion and selectivity above 99%. Thus, the work allowed the development of an alternative process to synthesize L-menthyl-glyoxylate, from the use of domestic ozone generator for the reaction of ozonolysis. [ABSTRACT FROM AUTHOR] more...
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- 2022
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179. Cannabidiol Discovery and Synthesis—a Target‐Oriented Analysis in Drug Production Processes.
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Aguillón, Anderson R., Leão, Raquel A. C., Miranda, Leandro S. M., and Souza, Rodrigo O. M. A.
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DRUG analysis , *CANNABIDIOL , *MANUFACTURING processes , *CANNABINOIDS , *SYNTHETIC marijuana - Abstract
The current state of evidence and recommendations for cannabidiol (CBD) and its health effects change the legal landscape and aim to destigmatize its phytotherapeutic research. Recently, some countries have included CBD as an antiepileptic product for compassionate use in children with refractory epilepsy. The growing demand for CBD has led to the need for high‐purity cannabinoids on the emerging market. The discovery and development of approaches toward CBD synthesis have arisen from the successful extraction of Cannabis plants for cannabinoid fermentation in brewer's yeast. To understand different contributions to the design and enhancement of the synthesis of CBD and its key intermediates, a detailed analysis of the history behind cannabinoid compounds and their optimization is provided herein. [ABSTRACT FROM AUTHOR] more...
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- 2021
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180. Enzyme Immobilization in Covalent Organic Frameworks: Strategies and Applications in Biocatalysis.
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Oliveira, Felipe L., S. França, Alexandre, Castro, Aline Machado, Alves de Souza, Rodrigo O. M., Esteves, Pierre M., and Gonçalves, Raoni Schroeder B.
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ENCAPSULATION (Catalysis) , *ENZYMES , *NANOPOROUS materials , *HETEROGENEOUS catalysis - Abstract
The development of efficient catalytic systems is a fundamental aspect for the straightforward production of chemicals. During the last years, covalent organic frameworks (COFs) emerged as an exciting class of organic nanoporous materials. Due to their pre‐designable structure, they can be prepared with distinct physicochemical characteristics, specific pore sizes, and tunable functional groups. Moreover, associated with their stability in different media, these materials are considered promising supports for enzyme immobilization. Herein, it is highlighted the recent literature of enzyme immobilization in COFs, the main immobilization strategies, and the catalytic applications of these composites. [ABSTRACT FROM AUTHOR] more...
- Published
- 2020
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181. Enzyme‐Decorated Covalent Organic Frameworks as Nanoporous Platforms for Heterogeneous Biocatalysis.
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Oliveira, Felipe L., Souza, Stefania P., Bassut, Jonathan, Álvarez, Heiddy M., Garcia‐Basabe, Yunier, Alves de Souza, Rodrigo O. M., Esteves, Pierre M., and Gonçalves, Raoni S. B.
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HETEROGENEOUS catalysis , *PHYSISORPTION , *OLEIC acid , *LIPASES , *THERMAL stability , *FUNCTIONAL groups , *ENZYMES , *BIOCATALYSIS - Abstract
Sustainability in chemistry heavily relies on heterogeneous catalysis. Enzymes, the main catalyst for biochemical reactions in nature, are an elegant choice to catalyze reactions due to their high activity and selectivity, although they usually suffer from lack of robustness. To overcome this drawback, enzyme‐decorated nanoporous heterogeneous catalysts were developed. Three different approaches for Candida antarctica lipase B (CAL‐B) immobilization on a covalent organic framework (PPF‐2) were employed: physical adsorption on the surface, covalent attachment of the enzyme in functional groups on the surface and covalent attachment into a linker added post‐synthesis. The influence of the immobilization strategy on the enzyme uptake, specific activity, thermal stability, and the possibility of its use through multiple cycles was explored. High specific activities were observed for PPF‐2‐supported CAL‐B in the esterification of oleic acid with ethanol, ranging from 58 to 283 U mg−1, which was 2.6 to 12.7 times greater than the observed for the commercial Novozyme 435. [ABSTRACT FROM AUTHOR] more...
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- 2019
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182. From Immobilization to Catalyst Use: A Complete Continuous‐Flow Approach Towards the Use of Immobilized Organocatalysts.
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Oliveira, Pedro H. R., S. Santos, Bruno M., Leão, Raquel A. C., Miranda, Leandro S. M., San Gil, Rosane A. S., Souza, Rodrigo O. M. A., and Finelli, Fernanda G.
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CATALYST poisoning , *FLOW chemistry , *HETEROGENEOUS catalysts , *CATALYSTS , *CHEMICAL industry , *CONTINUOUS flow reactors - Abstract
The combination of chiral supported‐organocatalysts and flow chemistry promotes the sustainable production of enantioenriched compounds providing a very powerful tool for chemical and pharmaceutical industries. However, the rapid deactivation of these catalysts in heterogeneous asymmetric reactions has been limiting the expansion of the area. In this work we report for the first time the advantages of synthesizing, immobilizing, and using a silica‐supported organocatalyst under a complete continuous‐flow approach, showing the impact of this method on the morphology, structure and lifetime of the organocatalyst. The first generation MacMillan's organocatalyst was prepared from L‐phenylalanine and immobilized in silica through a carbamate linkage under batch and continuous‐flow conditions. We also evaluated the performance of both batch and continuous‐flow organocatalysts in the Diels‐Alder reaction for proof of concept. [ABSTRACT FROM AUTHOR] more...
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- 2019
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183. Isopropylamine as Amine Donor in Transaminase‐Catalyzed Reactions: Better Acceptance through Reaction and Enzyme Engineering.
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Dawood, Ayad W. H., Weiß, Martin S., Schulz, Christian, Bornscheuer, Uwe T., Pavlidis, Ioannis V., Iding, Hans, and de Souza, Rodrigo O. M. A.
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ISOPROPYLAMINE , *AMINES , *AMINOTRANSFERASES , *HYDROGEN-ion concentration , *CARBOXYL group - Abstract
Abstract: Amine transaminases (ATA) have now become frequently used biocatalysts in chemo‐enzymatic syntheses including industrial applications. They catalyze the transfer of an amine group from a donor to an acceptor leading to an amine product with high enantiopurity. Hence, they represent an environmentally benign alternative for waste intensive chemical amine synthesis. Isopropylamine (IPA) is probably one of the most favored amine donors since it is cheap and achiral, but nevertheless there is no consistency in literature concerning reaction conditions when IPA is best to be used. At the same time there is still a poor understanding which structural properties in ATA are responsible for IPA acceptance. Herein, we demonstrate, on the basis of the 3FCR enzyme scaffold, a substantial improvement in catalytic activity towards IPA as the amine donor. The asymmetric synthesis of industrial relevant amines was used as model reaction. A systematic investigation of the pH‐value as well as concentration effects using common benchmark substrates and several ATA indicates the necessity of a substrate‐ and ATA‐dependent reaction engineering. [ABSTRACT FROM AUTHOR] more...
- Published
- 2018
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184. Continuous‐Flow Synthesis of (R)‐Propylene Carbonate: An Important Intermediate in the Synthesis of Tenofovir.
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Suveges, Nicolas S., Rodriguez, Anderson A., Diederichs, Carla C., de Souza, Stefania P., Leão, Raquel A. C., Miranda, Leandro S. M., Horta, Bruno A. C., Pedraza, Sérgio F., de Carvalho, Otavio V., Pais, Karla C., Terra, José H. C., and de Souza, Rodrigo O. M. A. more...
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CHEMICAL synthesis , *PROPENE , *TENOFOVIR , *GLYCERIN , *CHEMICAL reactions - Abstract
(R)‐Propylene carbonate is an important intermediate in the synthesis of tenofovir pro‐drugs such as tenofovir alafenamide fumarate (TAF) and tenofovir diisoproyl fumarate (TDF). Independent of the pro‐drug type, tenofovir presents a chiral secondary hydroxy derivative, which can be obtained directly from (R)‐propylene carbonate. Herein, we report our chemo‐enzymatic continuous‐flow strategy towards (R)‐propylene carbonate starting from a very cheap and renewable raw material, glycerol. We were able to synthesize (R)‐propylene carbonate in seven continuous‐flow steps, starting from glycerol, in good‐to‐excellent yields (66–93 %) and excellent selectivity (E > 200). [ABSTRACT FROM AUTHOR] more...
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- 2018
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185. Computer Modeling Explains the Structural Reasons for the Difference in Reactivity of Amine Transaminases Regarding Prochiral Methylketones.
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Teixeira, Iris S., Farias, André B., Horta, Bruno A. C., Milagre, Humberto M. S., de Souza, Rodrigo O. M. A., Bornscheuer, Uwe T., and Milagre, Cintia D. F.
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AMINATION , *COMPUTER simulation , *AMINOTRANSFERASES , *ENANTIOMERIC purity , *AMINES - Abstract
Amine transaminases (ATAs) are pyridoxal-5′-phosphate (PLP)-dependent enzymes that catalyze the transfer of an amino group from an amino donor to an aldehyde and/or ketone. In the past decade, the enzymatic reductive amination of prochiral ketones catalyzed by ATAs has attracted the attention of researchers, and more traditional chemical routes were replaced by enzymatic ones in industrial manufacturing. In the present work, the influence of the presence of an α,β-unsaturated system in a methylketone model substrate was investigated, using a set of five wild-type ATAs, the (R)-selective from Aspergillus terreus (Atr-TA) and Mycobacterium vanbaalenii (Mva-TA), the (S)-selective from Chromobacterium violaceum (Cvi-TA), Ruegeria pomeroyi (Rpo-TA), V. fluvialis (Vfl-TA) and an engineered variant of V. fluvialis (ATA-256 from Codexis). The high conversion rate (80 to 99%) and optical purity (78 to 99% ee) of both (R)- and (S)-ATAs for the substrate 1-phenyl-3-butanone, using isopropylamine (IPA) as an amino donor, were observed. However, the double bond in the α,β-position of 4-phenylbut-3-en-2-one dramatically reduced wild-type ATA reactivity, leading to conversions of <10% (without affecting the enantioselectivity). In contrast, the commercially engineered V. fluvialis variant, ATA-256, still enabled an 87% conversion, yielding a corresponding amine with >99% ee. Computational docking simulations showed the differences in orientation and intermolecular interactions in the active sites, providing insights to rationalize the observed experimental results. [ABSTRACT FROM AUTHOR] more...
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- 2022
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186. Fracture Strength, Failure Types, and Weibull Characteristics of Three-Unit Zirconia Fixed Dental Prostheses After Cyclic Loading: Effects of Veneering and Air-Abrasion Protocols
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Rodrigo Othávio de Assunção e Souza, Mutlu Özcan, Marco Antonio Bottino, Fernanda Campos, University of Zurich, and Souza, Rodrigo O A
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Dental Stress Analysis ,Materials science ,Surface Properties ,610 Medicine & health ,02 engineering and technology ,Composite Resins ,01 natural sciences ,10068 Clinic of Reconstructive Dentistry ,Dental Materials ,Flexural strength ,Tensile Strength ,Materials Testing ,0103 physical sciences ,Cyclic loading ,Cubic zirconia ,Dental Restoration Failure ,Composite material ,Weibull distribution ,010302 applied physics ,3504 Oral Surgery ,Weibull modulus ,021001 nanoscience & nanotechnology ,Air Abrasion, Dental ,Dental Veneers ,Dental Prosthesis Design ,Air abrasion ,Periodontics ,Zirconium ,Oral Surgery ,0210 nano-technology ,3506 Periodontics - Abstract
The required connector dimension for zirconia fixed dental prostheses (FDPs) may be a clinical limitation due to limited space in the occlusogingival direction. Using no veneering in the gingival regions of the pontics and connectors may solve this problem. This study evaluated the mechanical durability of zirconia FDPs with and without veneering in the gingival area of the connectors and pontics and subsequent air abrasion of this region with different protocols. Models were made of resin abutments (diameter = 6 or 8 mm, height = 6 mm, 6 degrees convergence) and embedded in polyurethane resin (distance = 11 mm). Zirconia frameworks were milled and randomly distributed by veneering (veneering of the entire framework [VEN] or no veneering at gingival regions of the pontic and connector [NVEN]) and by air-abrasion (Al₂O₃/SiO₂, 30 μm; or 45 μm Al₂O₃. FDPs were adhesively cemented and subjected to mechanical cycling (1,200,000 cycles, 200 N, 4 Hz, with water cooling). Specimens were tested until fracture (1 mm/min), and failure modes were classified. Data (N) were subjected to one-way analysis of variance in two sets, Tukey test (α = .05) and Weibull analysis. While veneering did not significantly affect the results (VEN: 1,958 ± 299 N; NVEN: 1,788 ± 152 N; P = .094), air abrasion did (P = .006), with the worst results for the groups conditioned with 45 μm Al₂O₃ (SiO₂: 1,748 ± 273 N; Al₂O₃: 1,512 ± 174 N). The NVEN group demonstrated the highest Weibull modulus (12.8) compared with the other groups (5.3-7.2). Fractures commonly initiated from the gingival side of the connector. Veneering of the gingival region of the connectors and pontics in zirconia FDPs did not diminish the fracture strength, but air-abrasion of this area with 45 μm Al₂O₃ decreased the results. more...
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- 2016
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187. Frontispiece: Cannabidiol Discovery and Synthesis—a Target‐Oriented Analysis in Drug Production Processes.
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Aguillón, Anderson R., Leão, Raquel A. C., Miranda, Leandro S. M., and Souza, Rodrigo O. M. A.
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CANNABIDIOL , *MANUFACTURING processes , *DRUG analysis , *CANNABINOIDS , *NATURAL products - Abstract
Frontispiece: Cannabidiol Discovery and Synthesis - a Target-Oriented Analysis in Drug Production Processes Keywords: cannabinoids; drug discovery; natural products; phytotherapeutic research; synthesis design EN cannabinoids drug discovery natural products phytotherapeutic research synthesis design 1 1 1 04/09/21 20210326 NES 210326 B The discovery and development b of approaches toward the synthesis of cannabidiol (CBD), which has an increasing meaning as a medicine, have arisen from the successful extraction of I Cannabis i plants for cannabinoid fermentation in brewer's yeast. Cannabinoids, drug discovery, natural products, phytotherapeutic research, synthesis design. [Extracted from the article] more...
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- 2021
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188. Influence of the postpolymerization type and time on the flexural strength and dimensional stability of 3D printed interim resins.
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Silva NR, Moreira FGG, Cabral ABC, Bottino MA, Marinho RMM, and Souza ROA
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- Materials Testing, Analysis of Variance, Water, Printing, Three-Dimensional, Surface Properties, Flexural Strength, Stereolithography
- Abstract
Statement of Problem: The mechanical strength of 3-dimensionally (3D) printed interim resins is unclear but influenced by printing parameters. Evidence regarding standardization of the postpolymerization type and time for 3D printed interim resins is sparse., Purpose: The purpose of this in vitro study was to evaluate the influence of postpolymerization type and time on flexural strength and dimensional stability of 3D printed resins for interim restorations., Material and Methods: A total of 288 bars were 3D printed (Form 2; Formlabs, stereolithography-SLA, 50 µm, 30 degrees), (25×2×2 mm; International Organization for Standardization-ISO 4049:2019) abraded and randomly divided into 9 groups (n=30) according to postpolymerization (Ultraviolet device-UV; Microwave with water-MWA; Microwave without water-MW) and time (15, 20, and 30 minutes for UV; and 5, 8, and 10 minutes for MW and MWA). Each bar was then measured with digital calipers at 11 points for length, thickness, and width before and after postpolymerization to analyze dimensional stability. The flexural strength was then measured (σ; 980.6 N, 1 mm/minute) and the fractured surfaces were analyzed with scanning electron microscopy. The σ (MPa) data were evaluated by using a 2-way analysis of variance (ANOVA) and the Tukey honestly significant difference (HSD) pairwise comparisons test (α=.05). Dimensional stability data (mm) were analyzed by using the Kruskal-Wallis test and Dwass-Steel-Critchlow-Fligner multiple comparisons. The Weibull analysis was performed with σ data., Results: The 2-way ANOVA revealed that all factors and their interaction were significant for σ (P<.001). The UV groups presented the highest σ values, being statistically higher than all MW and MWA groups. The Weibull analysis revealed that postpolymerization UV groups found the highest values regarding the characteristic strength, although the MW 8-minute group (13.71) found the highest value for the Weibull modulus. Furthermore, the Kruskal-Wallis test revealed that only the postpolymerization factor was significant for dimensional stability (P<.001). The postpolymerization microwave groups found greater expansion variations at all times, with the MW 8-minute group (0.78 ±0.54) presenting the greatest variation in dimensional stability., Conclusions: UV was determined to be the most suitable type of postpolymerization for interim printed resin among the postpolymerization methods, regardless of the application time. The postpolymerization MW groups found greater variations in dimensional stability., (Copyright © 2023 Editorial Council for The Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.) more...
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- 2023
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189. The Effect of a 10-MDP-Based Dentin Adhesive as Alternative for Bonding to Implant Abutment Materials.
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Carvalho PCK, Almeida CCMS, Souza ROA, and Tango RN
- Abstract
Bonding to different dental restorative materials is challenging. This study aimed to evaluate the effect of a 10-MDP-based dentin adhesive on the shear bond strength (SBS) of self-adhesive resin cement (RC) to implant abutment materials. One hundred and twenty specimens were obtained from zirconia (ZO), cobalt-chromium alloy (CoCr), and commercially pure titanium (Ti), which were treated as follows (n = 10): control group-non-treated (CG), 10-MDP-based dentin adhesive (SB), light-cured SB (SB-LC), and zirconia primer (ZP). Blocks of RC were buildup and, after 24 h, were tested for bond strength. Data of SBS (MPa) were submitted to two-way ANOVA and Tukey test (α = 0.05). There was no difference in SBS among materials for CG and ZP, higher SBS were recorded for Ti SB and Ti SB-LC compared to ZO upon the same surface treatments. For the comparisons among treatments, SB-LC showed the highest SBS for CoCr. For ZO and Ti, higher SBS were recorded with SB and SB-LC. No cohesive failures were observed. It was concluded that the surface treatment with 10-MDP-based materials increased the bond strength of the resin cement to abutment materials, which showed to be material dependent. more...
- Published
- 2022
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190. Short communication: Influence of retainer configuration and loading direction on the stress distribution of lithium disilicate resin-bonded fixed dental prostheses: 3D finite element analysis.
- Author
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Dal Piva AMO, Tribst JPM, Saavedra GSFA, Souza ROA, de Melo RM, Borges ALS, and Özcan M
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- Computer Simulation, Cuspid physiology, Finite Element Analysis, Humans, Incisor physiology, Mandible physiology, Materials Testing, Maxilla, Prognosis, Shear Strength, Stress, Mechanical, Tensile Strength, Tooth physiology, Dental Porcelain chemistry, Dental Prosthesis, Dental Stress Analysis methods, Imaging, Three-Dimensional methods, Orthodontic Appliances, Fixed, Resins, Synthetic
- Abstract
The present study elucidates the mechanical performance of different designs of resin-bonded fixed dental prostheses made of lithium disilicate simulating masticatory loads of anterior or canine guidance. A three-dimensional model of maxilla was constructed containing central incisor and canine teeth, with edentulous space of the lateral incisor. Three designs of prosthesis were created: retained in central incisor (1-I), retained in canine (1-C) and fixed in both teeth (2-IC). The computational analysis was performed for load in canine and central incisor separately (100N, 45°). The tensile and shear stresses were calculated for the resin-bonded fixed dental prosthesis, bonding surface of each retainer and cement layer using 3D finite element analysis. The 20 highest stress values were analyzed using two-way ANOVA and post-hoc Tukey test, all with α = 5%. The computational analysis showed that 2-retainer resin-bonded fixed dental prosthesis presented the worst prognosis regardless of the mandibular movement. ANOVA showed that Mandibular movement*Retainer interaction influenced on the tensile and shear stresses values (p < 0.01). Higher stresses were observed in the connector region for all groups (13-82.2 MPa; 11-70.2 MPa). In order to reduce the stress concentration in the resin-bonded fixed dental prosthesis and the retainer made of lithium disilicate, the occlusion may serve as the selection criteria of the unitary abutment for better sustainability., (Copyright © 2019. Published by Elsevier Ltd.) more...
- Published
- 2019
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191. Monoclinic phase transformation and mechanical durability of zirconia ceramic after fatigue and autoclave aging.
- Author
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Mota YA, Cotes C, Carvalho RF, Machado JPB, Leite FPP, Souza ROA, and Özcan M
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- Hot Temperature, Pressure, Ceramics chemistry, Stress, Mechanical, Zirconium chemistry
- Abstract
Objectives: This study evaluated the influence of two aging procedures on the biaxial flexural strength of yttria-stabilized tetragonal zirconia ceramics., Material and Methods: Disc-shaped zirconia specimens and (ZE: E.max ZirCAD, Ivoclar; ZT: Zirkon Translucent, Zirkonzahn) (N = 80) (∅:12 mm; thickness:1.2 mm, ISO 6872) were prepared and randomly divided into four groups (n = 10 per group) according to the aging procedures: C: Control, no aging; M: mechanical cycling (2 × 10
6 cycles/3.8 Hz/200 N); AUT: Aging in autoclave at 134°C, 2 bar for 24 h; AUT + M: Autoclave aging followed by mechanical cycling. After aging, the transformed monoclinic zirconia (%) were evaluated using X-ray diffraction and surface roughness was measured using atomic force microscopy. The average grain size was measured by scanning electron microscopy and the specimens were submitted to biaxial flexural strength testing (1 mm/min, 1000 kgf in water). Data (MPa) were statistically analyzed using 2-way analysis of variance and Tukey's test (α = 0.05)., Results: Aging procedures significantly affected (p = 0.000) the flexural strength data but the effect of zirconia type was not significant (p = 0.657). AUTZT (936.4 ± 120.9b ) and AUT + MZE (867.2 ± 49.3b ) groups presented significantly higher values (p < 0.05) of flexural strength than those of the control groups (CZT : 716.5 ± 185.7a ; CZE : 779.9 ± 114a ) (Tukey's test). The monoclinic phase percentage (%) was higher for AUTZE (71), AUTZT (66), AUT + MZE (71), and AUT + MZM (66) compared to the C groups (ZE:0; ZT:0). Surface roughness (µm) was higher for AUTZE (0.09), AUTZT (0.08), AUT + MZE (0.09 µm), and AUT + MZT (0.09 µm) than those of other groups., Conclusions: Regardless of the zirconia type, autoclave aging alone or with mechanical aging increased the flexure strength but also induced higher transformation from tetragonal to monoclinic phase in both zirconia materials tested. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 105B: 1972-1977, 2017., (© 2016 Wiley Periodicals, Inc.) more...- Published
- 2017
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192. Durability and Weibull Characteristics of Lithium Disilicate Crowns Bonded on Abutments with Knife-Edge and Large Chamfer Finish Lines after Cyclic Loading.
- Author
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Cortellini D, Canale A, Souza RO, Campos F, Lima JC, and Özcan M
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- Ceramics, Dental Restoration Failure, Materials Testing, Crowns, Dental Porcelain, Dental Stress Analysis
- Abstract
Purpose: The aim of this study was to evaluate the durability of lithium disilicate crowns bonded on abutments prepared with two types of finish lines after long-term cyclic loading., Materials and Methods: Pressed lithium disilicate all-ceramic molar crowns were bonded (Variolink II) to epoxy abutments (height: 5.5 mm, Ø: 7.5 mm, conicity: 6°) (N = 20) with either knife-edge (KE) or large chamfer (LC) finish lines. Each assembly was submitted to cyclic loading (1,200,000×; 200 N; 1 Hz) in water and then tested until fracture in a universal testing machine (1 mm/min). Failure types were classified and further evaluated under stereomicroscope and SEM. The data (N) were analyzed using one-way ANOVA. Weibull distribution values including the Weibull modulus (m), characteristic strength (0), probability of failure at 5% (0.05), 1% (0.01), and correlation coefficient were calculated., Results: Type of finish line did not significantly influence the mean fracture strength of pressed ceramic crowns (KE: 1655 ± 353 N; LC: 1618 ± 263 N) (p = 0.7898). Weibull distribution presented lower shape value (m) of KE (m = 5.48; CI: 3.5 to 8.6) compared to LC (m = 7.68; CI: 5.2 to 11.3). Characteristic strengths (0) (KE: 1784.9 N; LC: 1712.1 N) were higher than probability of failure at 5% (0.05) (KE: 1038.1 N; LC: 1163.4 N) followed by 1% (0.01) (KE: 771 N; LC: 941.1 N), with a correlation coefficient of 0.966 for KE and 0.924 for LC. Type V failures (severe fracture of the crown and/or tooth) were more common in both groups. SEM findings showed that fractures occurred mainly from the cement/ceramic interface at the occlusal side of the crowns., Conclusion: Lithium disilicate ceramic crowns bonded onto abutment teeth with KE preparation resulted in similar fracture strength to those bonded on abutments with LC finish line., Clinical Significance: Pressed lithium disilicate ceramic crowns may not require invasive finish line preparations since finish line type did not impair the strength after aging conditions., (© 2015 by the American College of Prosthodontists.) more...
- Published
- 2015
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193. Effects of aging procedures on the topographic surface, structural stability, and mechanical strength of a ZrO2-based dental ceramic.
- Author
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Cotes C, Arata A, Melo RM, Bottino MA, Machado JP, and Souza RO
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- Algorithms, Crystallography, Imaging, Three-Dimensional methods, Materials Testing, Pliability, Random Allocation, Stress, Mechanical, Surface Properties, Temperature, Time Factors, Water chemistry, X-Ray Diffraction, Ceramics chemistry, Dental Materials chemistry, Yttrium chemistry, Zirconium chemistry
- Abstract
Objective: To determine the effects of different aging methods on the degradation and flexural strength of yttria-stabilized tetragonal zirconia (Y-TZP) METHODS: Sixty disc-shaped specimens (∅, 12mm; thickness, 1.6mm) of zirconia (Vita InCeram 2000 YZ Cubes, VITA Zahnfabrik) were prepared (ISO 6872) and randomly divided into five groups, according to the aging procedures (n=10): (C) control; (M) mechanical cycling (15,000,000 cycles/3.8Hz/200N); (T) thermal cycling (6,000 cycles/5-55°C/30s); (TM) thermomechanical cycling (1,200,000 cycles/3.8Hz/200N with temperature range from 5°C to 55°C for 60s each); (AUT) 12h in autoclave at 134°C/2bars; and (STO) storage in distilled water (37°C/400 days). After the aging procedures, the monoclinic phase percentages were evaluated by X-ray diffraction (XRD), and topographic surface analysis was performed by 3D profilometry. The specimens were then subjected to biaxial flexure testing (1mm/min, load 100kgf, in water). The biaxial flexural strength data (MPa) were analyzed by 1-way ANOVA and Tukey's test (α=0.05). The data for monoclinic phase percentage and profilometry (Ra) were analyzed by Kruskal-Wallis and Dunn's tests., Results: ANOVA revealed that flexural strength was affected by the aging procedures (p=0.002). The M (781.6MPa) and TM (771.3MPa) groups presented lower values of flexural strength than did C (955MPa), AUT (955.8MPa), T (960.8MPa) and STO (910.4MPa). The monoclinic phase percentage was significantly higher only for STO (12.22%) and AUT (29.97%) when compared with that of the control group (Kruskal-Wallis test, p=0.004). In addition, the surface roughnesses were similar among the groups (p=0.165)., Significance: Water storage for 400 days and autoclave aging procedures induced higher phase transformation from tetragonal to monoclinic; however, they did not affect the flexural strength of Y-TZP ceramic, which decreased only after mechanical and thermomechanical cycling., (Copyright © 2014 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.) more...
- Published
- 2014
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194. Effects of thickness, processing technique, and cooling rate protocol on the flexural strength of a bilayer ceramic system.
- Author
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Lima JM, Souza AC, Anami LC, Bottino MA, Melo RM, and Souza RO
- Subjects
- Materials Testing, Ceramics, Cold Temperature
- Abstract
Objective: To determine whether the thickness, processing technique, and cooling protocol of veneer ceramic influence the flexural strength of a bilayer ceramic system., Materials and Methods: Sixty-four bar-shaped specimens (20mm×4mm×1mm) of yttria-stabilized tetragonal zirconia (Vita In-Ceram YZ, Vita) were fabricated (ISO 6872) and randomly divided into 8 groups (n=8) according to the factors "processing technique" (P - PM9 and V - VM9), "thickness" (1mm and 3mm), and "cooling protocol" (S - slow and F - fast). The veneer ceramics were applied only over one side of the bar-shaped specimens. All specimens were mechanically cycled (2×10(6) cycles, 84N, 3.4Hz, in water), with the veneer ceramic under tension. Then, the specimens were tested in 4-point bending (1mm/min, load 100kgf, in water), also with the veneer ceramic under tension, and the maximum load was recorded at first sign of fracture. The flexural strength (σ) was calculated, and the mode of failure was determined by stereomicroscopy (30×). The data (MPa) were analyzed statistically by 3-way ANOVA and Tukey's test (α=0.05)., Results: ANOVA revealed that the factor "thickness" (p=0.0001) was statistically significant, unlike the factors "processing technique" (p=0.6025) and "cooling protocol" (p=0.4199). The predominant mode of failure was cracking., Significance: The thickness of the veneer ceramic has an influence on the mechanical strength of the bilayer ceramic system, regardless of processing technique and cooling protocol of the veneer ceramic., (Copyright © 2013 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.) more...
- Published
- 2013
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195. Air-particle abrasion on zirconia ceramic using different protocols: effects on biaxial flexural strength after cyclic loading, phase transformation and surface topography.
- Author
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Souza RO, Valandro LF, Melo RM, Machado JP, Bottino MA, and Ozcan M
- Subjects
- Hot Temperature, Pressure, Surface Properties, Air, Ceramics chemistry, Mechanical Phenomena, Phase Transition, Zirconium chemistry
- Abstract
This study evaluated the effect of different air-particle abrasion protocols on the biaxial flexural strength and structural stability of zirconia ceramics. Zirconia ceramic specimens (ISO 6872) (Lava, 3M ESPE) were obtained (N=336). The specimens (N=118, n=20 per group) were randomly assigned to one of the air-abrasion protocols: Gr1: Control (as-sintered); Gr2: 50 µm Al2O3 (2.5 bar); Gr3: 50 µm Al2O3 (3.5 bar); Gr4: 110 µm Al2O3(2.5 bar); Gr5: 110 µm Al2O3 (3.5 bar); Gr6: 30 µm SiO2 (2.5 bar) (CoJet); Gr7: 30 µm SiO2(3.5 bar); Gr8: 110 µm SiO2 (2.5 bar) (Rocatec Plus); and Gr9: 110 µm SiO2 (3.5 bar) (duration: 20 s, distance: 10 mm). While half of the specimens were tested immediately, the other half was subjected to cyclic loading in water (100,000 cycles; 50 N, 4 Hz, 37 °°C) prior to biaxial flexural strength test (ISO 6872). Phase transformation (t→m), relative amount of transformed monoclinic zirconia (FM), transformed zone depth (TZD) and surface roughness were measured. Particle type (p=0.2746), pressure (p=0.5084) and cyclic loading (p=0.1610) did not influence the flexural strength. Except for the air-abraded group with 110 µm Al2O3 at 3.5 bar, all air-abrasion protocols increased the biaxial flexural strength (MPa) (Controlnon-aged: 1,030 ± 153, Controlaged: 1,138 ± 138; Experimentalnon-aged: 1,307 ± 184-1,554 ± 124; Experimentalaged: 1,308 ± 118-1,451 ± 135) in both non-aged and aged conditions, respectively. Surface roughness (Ra) was the highest with 110 µm Al2O3(0.84 µm. FM values ranged from 0% to 27.21%, higher value for the Rocatec Plus (110 µm SiO2) and 110 µm Al2O3 groups at 3.5 bar pressure. TZD ranged between 0 and 1.43 µm, with the highest values for Rocatec Plus and 110 µm Al2O3 groups at 3.5 bar pressure., (Copyright © 2013 Elsevier Ltd. All rights reserved.) more...
- Published
- 2013
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196. Effect of air-particle abrasion protocols on the biaxial flexural strength, surface characteristics and phase transformation of zirconia after cyclic loading.
- Author
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Ozcan M, Melo RM, Souza RO, Machado JP, Felipe Valandro L, and Botttino MA
- Subjects
- Air, Dental Stress Analysis methods, Elastic Modulus, Hardness, Materials Testing, Phase Transition, Stress, Mechanical, Surface Properties, Tensile Strength, Dental Etching methods, Dental Materials chemistry, Silicon Dioxide chemistry, Zirconium chemistry
- Abstract
This study evaluated the effect of air-particle abrasion protocols on the biaxial flexural strength, surface characteristics and phase transformation of zirconia after cyclic loading. Disc-shaped zirconia specimens (Ø: 15mm, thickness: 1.2mm) (N=32) were submitted to one of the air-particle abrasion protocols (n=8 per group): (a) 50μm Al2O3 particles, (b) 110μm Al2O3 particles coated with silica (Rocatec Plus), (c) 30μm Al2O3 particles coated with silica (CoJet Sand) for 20s at 2.8bar pressure. Control group received no air-abrasion. All specimens were initially cyclic loaded (×20,000, 50N, 1Hz) in water at 37°C and then subjected to biaxial flexural strength testing where the conditioned surface was under tension. Zirconia surfaces were characterized and roughness was measured with 3D surface profilometer. Phase transformation from tetragonal to monoclinic was determined by Raman spectroscopy. The relative amount of transformed monoclinic zirconia (FM) and transformed zone depth (TZD) were measured using XRD. The data (MPa) were analyzed using ANOVA, Tukey's tests and Weibull modulus (m) were calculated for each group (95% CI). The biaxial flexural strength (MPa) of CoJet treated group (1266.3±158(A)) was not significantly different than that of Rocatec Plus group (1179±216.4(A,B)) but was significantly higher than the other groups (Control: 942.3±74.6(C); 50μm Al2O3: 915.2±185.7(B,C)). Weibull modulus was higher for control (m=13.79) than those of other groups (m=4.95, m=5.64, m=9.13 for group a, b and c, respectively). Surface roughness (Ra) was the highest with 50μm Al2O3 (0.261μm) than those of other groups (0.15-0.195μm). After all air-abrasion protocols, FM increased (15.02%-19.25%) compared to control group (11.12%). TZD also showed increase after air-abrasion protocols (0.83-1.07μm) compared to control group (0.59μm). Air-abrasion protocols increased the roughness and monoclinic phase but in turn abrasion with 30μm Al2O3 particles coated with silica has increased the biaxial flexural strength of the tested zirconia., (Copyright © 2013 Elsevier Ltd. All rights reserved.) more...
- Published
- 2013
- Full Text
- View/download PDF
197. Influence of acid-etching and ceramic primers on the repair of a glass ceramic.
- Author
-
Queiroz JR, Souza RO, Nogueira Junior L Jr, Ozcan M, and Bottino MA
- Subjects
- Aluminum Silicates chemistry, Composite Resins chemistry, Dental Bonding, Dental Polishing methods, Dental Porcelain chemistry, Dental Prosthesis Repair, Dental Stress Analysis instrumentation, Humans, Hydrofluoric Acid chemistry, Materials Testing, Methacrylates chemistry, Microscopy, Electron, Scanning, Potassium Compounds chemistry, Resin Cements chemistry, Silanes chemistry, Stress, Mechanical, Surface Properties, Temperature, Tensile Strength, Thiones chemistry, Time Factors, Triazines chemistry, Water chemistry, Acid Etching, Dental methods, Ceramics chemistry, Dental Materials chemistry
- Abstract
The objective of this study was to evaluate the influence of different primers on the microtensile bond strength (μTBS) between a feldspathic ceramic and two composites. Forty blocks (6.0 x 6.0 x 5.0 mm³) were prepared from Vita Mark II . After polishing, they were randomly divided into 10 groups according to the surface treatment: Group 1, hydrofluoric acid 10% (HF) + silane; Group 2, CoJet + silane; Group 3, HF + Metal/Zirconia Primer; Group 4, HF + Clearfil Primer; Group 5, HF + Alloy Primer; Group 6, HF + V-Primer; Group 7, Metal/Zirconia Primer; Group 8, Clearfil Primer; Group 9, Alloy Primer; Group 10, V-Primer. After each surface treatment, an adhesive was applied and one of two composite resins was incrementally built up. The sticks obtained from each block (bonded area: 1.0 mm² ± 0.2 mm) were stored in distilled water at 37 degrees C for 30 days and submitted to thermocycling (7,000 cycles; 5 degrees C/55 degrees C ± 1 degree C). The μTBS test was carried out using a universal testing machine (1.0 mm/min). Data were analyzed using ANOVA and a Tukey test (a = 0.05). The surface treatments significantly affected the results (P < 0.05); no difference was observed between the composites (P > 0.05). The bond strength means (MPa) were as follows: Group 1a = 29.6; Group 1b = 33.7; Group 2a = 28.9; Group 2b = 27.1; Group 3a = 13.8; Group 3b = 14.9; Group 4a = 18.6; Group 4b = 19.4; Group 5a = 15.3; Group 5b = 16.5; Group 6a = 11; Group 6b = 18; Groups 7a to 10b = 0. While the use of primers alone was not sufficient for adequate bond strengths to feldspathic ceramic, HF etching followed by any silane delivered higher bond strength. more...
- Published
- 2012
198. Analysis of tooth enamel after excessive bleaching: a study using scanning electron microscopy and energy dispersive x-ray spectroscopy.
- Author
-
Souza RO, Lombardo GH, Pereira SM, Zamboni SC, Valera MC, Araujo MA, and Ozcan M
- Subjects
- Animals, Calcium analysis, Cattle, Microscopy, Electron, Scanning, Spectrometry, X-Ray Emission, Dental Enamel drug effects, Hydrogen Peroxide adverse effects, Oxidants adverse effects, Tooth Bleaching adverse effects
- Abstract
This study assessed alterations on bovine enamel after excessive bleaching. Coronal portions of bovine teeth (n = 30) were sectioned and divided into three groups (n = 10 per group). The coronal parts were further cut incisocervically into two halves. While one half received no bleaching (control), the other half was subjected to either one (group 1), three (group 2), or five bleaching sessions (group 3) with 35% hydrogen peroxide. The enamel surfaces were then analyzed using scanning electron microscopy and energy dispersive x-ray spectroscopy (EDS). Excessive bleaching affected the surface morphology and chemistry of the bovine enamel. EDS analysis showed the highest decrease in calcium ion percentages in groups 2 and 3 when compared to their nonbleached halves. Oxygen and phosphorus percentages were comparable on both the control and bleached enamel, regardless of the number of bleaching sessions. Consecutive bleaching sessions with 35% hydrogen peroxide may lead to morphologic and specific elemental changes when performed in a short period of time. Calcium ion percentages may decrease when this bleaching agent is used for more than one session. Int J Prosthodontics 2010;23:29-32. more...
- Published
- 2010
199. Effect of different polymerization devices on the degree of conversion and the physical properties of an indirect resin composite.
- Author
-
Souza RO, Ozcan M, Mesquita AM, De Melo RM, Galhano GA, Bottino MA, and Pavanelli CA
- Subjects
- Equipment Design, Hardness Tests, Materials Testing, Composite Resins, Polymerization
- Abstract
Polymerization of indirect resin composites (IRC) is carried out in the 'laboratories using special photo-polymerization devices to achieve a higher degree of conversion (DC). Such devices present variation in chambers and light output which may have consequences on the chemical and physical properties of IRCs. This study evaluated the effect of different polymerization devices on the flexural strength, Vickers microhardness and DC of an IRC. Specimens were prepared from an IRC material, Sinfony (3M ESPE), using special molds for flexural strength test (N=30) (25 x 2 x 2 mm, ISO 4049), Vickers microhardness test (N=30) (5 x 4 mm) and for DC (N=30) utilizing Micro-raman Spectroscopy. All specimens were submitted to initial polymerization with a Visio Alpha unit (3M ESPE) and then randomly divided into three groups (n=10/ group). Specimens in Group 1 (control) received additional polymerizations using a Visio Beta Vario device (3M ESPE), and those in Group 2 and Group 3 using Powerlux (EDG) and Strobolux (EDG) devices, respectively. DC and mechanical tests were then conducted. For the mechanical tests, the data were analyzed using ANOVA and Tukey's tests (p < 0.05) and for DC, one-way ANOVA was used. Polymerization in Strobolux (Group 3) resulted in significantly lower flexural strength (MPa) values (134 +/- 27) compared to Visio Beta Vario (165 +/- 20) (Group 1) (p < 0.05). The lowest microhardness values (Kg/mm2) were obtained in Group 3 (30 +/- 1) (p < 0.05). DC was similar in all groups (75 +/- 1, 91 +/- 5, 85 +/- 7% for Visio Beta Vario, Powerlux and Strobolux, respectively) (p = 0.1205). The type of polymerization device may affect the flexural strength and Vickers hardness of the IRC tested. DC also seems to be affected by the type of polymerization device but the results were not significant. more...
- Published
- 2010
200. A comparison of the film thickness of two adhesive luting agents and the effect of thermocycling on their microTBs to feldspathic ceramic.
- Author
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Pereira PC, Castilho AA, Souza RO, Passos SP, Takahashi FE, and Bottino MA
- Subjects
- Temperature, Ceramics, Dental Bonding, Dental Cements, Materials Testing
- Abstract
The aim of the present study was to evaluate the effect of thermocycling (TC) on the microtensile bond strength (microTBS) of two luting agents to feldspathic ceramic and to measure their film thickness (FT). For the microTBS test, sixteen blocks (6.4 x 6.4 x 4.8 mm) were fabricated using a feldspathic ceramic, etched with 10% hydrofluoric acid, rinsed and treated with the silane agent. The ceramic blocks were divided into two groups (n= 8): Gr1: dual-cured resin cement and Gr2: flowable resin. The luting agents were applied on the treated surfaces. Microsticks (1 +/-0. 1mm2) were prepared and stored under two conditions: dry, specimens immediately submitted to the microTBS test, and TC (6,000 cycles; 5 degrees C-55 degrees C). The microTBS was evaluated using a universal testing machine (1 mm/min). The microTBS data (MPa) were submitted to two-way ANOVA and Tukey' test (5%). For the FT test (ISO 4049), 0.05 ml of each luting agent (n=8) was pressed between two Mylar-covered glass plates (150 N) for 180 seconds and light polymerized. FT was measured using a digital paquimeter (Model 727-2001). The data (mm) were submitted to one-way ANOVA. The luting cement did not influence the microTBS results (p= 0.4467). Higher microtensile bond values were found after TC (20.5 +/- 8.6 MPa) compared to the dry condition (13.9 +/- 4. 7MPa), for both luting agents. The luting agents presented similar film thicknesses: Gr1- 0.052 +/- 0.016 mm; Gr2-0.041 +/- 0.003 mm. The luting agents presented similar film thickness and microTBS values, in dry and TC conditions and TC increased the bond strength regardless of the luting agent. more...
- Published
- 2009
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