Magister Scientiae Dentium - MSc(Dent) / Restorative systems classified as polyacid modified composite resins, or compomers, have appeared on the market. An example of this is Dyract AP. Dyract AP must be used with the Prime & Bond NT bonding system. Prime & Bond NT can be applied without any form of prior etching, or it can be applied after application of Non Rinse Conditioner, or it can be applied after etching with 36% phosphoric acid. The purpose of the study was to determine the qualitative microleakage of Dyract AP and its bonding systems, as well as the influence of saliva contamination there of. Freshly extracted, non-carious, human premolars were randomly divided into 8 groups of 18 teeth each. Apiseetomies coated with Polivar varnish and restored with amalgam were performed on all teeth. Class V type cavities of 3 mm diameter and 1,5 mm depth were prepared on the CEJ junction on the buccal side of all teeth. Dyract AP restorations were placed using the bonding procedures indicated: Group 1: P&B NT (Prime & Bond NT); group 2: acid (36% phosphoric acid) + P&B NT; group 3: NRC (Non Rinse Conditioner) + P&B NT; group 4: P&B NT + Saliva; group 5: acid + Saliva + P&B NT; group 6: acid + P&B NT + Saliva; group 7: NRC + Saliva + P&B NT; group 8: NRC + P&B NT + Saliva. Restorations were finished with Sof-Lex discs. After 24 hours storage in distilled water the teeth were removed and coated with two layers of nail varnish, except for 1 mm around the restorations. The teeth were then thermocycled in a 0.5% basic fuchsin solution for 500 complete cycles between 8°C and 50°C, with a dwell time of 15 seconds.

Indiana University-Purdue University Indianapolis (IUPUI) / BACKGROUND: Phosphoric acid treatment has been reported to be relevant for zirconia cleaning after contamination. However, its interaction with different primers is not well known and needs to be investigated. OBJECTIVES: To compare the shear bond strengths (SBS) of resin cement to Y-TZP after phosphoric acid pretreatment and different chemical conditioning protocols, and to test the durability of SBSs after long term storage and thermal cycling conditions. To investigate the effect of phosphoric acid 75 on the surface roughness of a yttrium-stabilized tetragonal zirconia polycrystal ceramic (Y-TZP). METHODS: Sixty bars of zirconia (30 X 5 X 2 mm) were polished and glued to acrylic tubes. Each bar received 3 different surface treatments (control, phosphoric acid and air-abrasion). The bars were randomly assigned into five groups according to different primers applied (No primer, Clearfil ceramic primer, Monobond Plus, Z-prime plus and AZ primer). After that, resin cement was mixed, injected into a mold, and light cured. The specimens were tested in shear on a universal testing machine. Half of the specimens were tested after 24 h water storage and the other half were tested after 90 days of water storage and thermocycling. Non-contact profilometer was used to assess the effect of the three surface pretreatments on surface roughness of zirconia. Mode of failure and surface roughness were evaluated with SEM. Statistical analyses were conducted with mixed-model ANOVA and chi-square tests. RESULTS: The results indicated that Monobond Plus primer showed higher SBS after phosphoric acid treatment compared to other primers used. SBS of all air abrasion groups were higher than phosphoric acid groups. Long term water storage and thermocycling led to a statistically significant decrease in SBS for all groups except Monobond Plus, Z-prime plus and AZ primer after air abrasion treatment. Surface roughness measurements showed no significant differences among the surface treatments. CONCLUSION: Monobond Plus provided the highest SBS to zirconia after phosphoric acid treatment. The findings suggest that the air abrasion is the best surface treatment after contamination of zirconia surface. Monobond Plus, Z-prime plus and AZ primer showed durable SBS after air abrasion treatment and aging process.

No description available.

This report is an examination of the practical design of a phosphoric acid production facility wet scrubber. It includes a brief background of the Florida Phosphate Industry, in addition to the rules and regulations affecting the emission of fluoride contaminates. The theoretical aspects of a packed absorption tower is discussed prior to the actual design of a cross-flow wet scrubber of the type typically found in the Florida Phosphate Industry.

Ces travaux de thèse avaient pour objectif la synthèse asymétrique d’hétérocycles énantioenrichis par des méthodes à hautes valeurs ajoutées. Pour cela des catalyseurs ont été employés dans des réactions de cycloaddition. D’une part, l’organocatalyse asymétrique permet d’utiliser un matériel chiral peu coûteux en faible quantité pour générer des produits chiraux, d’autre part, les réactions de cycloadditions permettent une économie d’atome certaine et la création de plusieurs liaisons en une réaction.La première partie de cette thèse concerne des réactions de cycloadditions d’aza-Diels-Alder à demande inverse en électrons. Ces travaux mettent en jeu des 1-Azadiènes et des énecarbamates pour générer des tétrahydropyridines possédant 3 centres stéréogènes contigus.Les produits ont été obtenus sous la forme d’un seul diastéréomère avec de bons rendements et de bons excès énantiomérique. La modification des substrats sur diverses positions a été possible sans influencer l’efficacité de la réaction.Dans la seconde partie, une réaction de cycloaddition entre des quinones et des énecarbamates a été étudiée. L’utilisation d’un acide phosphorique à squelette SPINOL s’est révélée très efficaces, menant à des 2,3-Dihydrobenzofuranes optiquement actifs. Les produits sont isolés avec d’excellents rendements et excès énantiomériques, mais des ratios diastéréomériques faibles. Ces derniers peuvent être améliorés en engageant des énethiocarbamates.Une cascade réactionnelle peut aussi être effectuée en formant la quinone in situ à l’aide d’un réactif hypervalent iodé. L’étendue de notre cycloaddition ainsi que sa variante initié par du PIDA est conséquente mais reste encore à améliorer. Différentes hydroquinones seront ainsi évaluées. Les cycloadduits seront ultérieurement transformés de manière à valoriser cette méthodologie. Les configurations relatives et absolues des centres asymétriques formés seront déterminées avec précision par cliché de diffraction des rayons X. Ces pistes sont en cours d’étude et de réalisation au laboratoire.Enfin, la dernière partie concerne une réaction de cycloaddition 1,3-Dipolaire entre des nitrones et des énecarbamates. Si l’utilisation d’un acide phosphorique ne s’est pas révélée efficace, l’utilisation d’un phosphate de cuivre est en revanche convaincante. Initialement, la réaction a montré d’excellents résultats, malheureusement non reproductibles. Une optimisation rigoureuse a été nécessaire pour obtenir des résultats satisfaisants. Cette réaction nécessite une évaluation de son étendue vis-À-Vis des énecarbamates. Des transformations sont également envisagées pour valoriser cette méthodologie. / This thesis works were aimed the asymmetric synthesis of optically pure heterocycles by high added value methodology. On one hand, the asymmetric organocatalysis allows using an inexpensive chiral materials in small quantities to generate chiral products, on the other hand, the cycloaddition reactions allow atom economy and the creation of several bonds in one reaction.The first part of this thesis concerns inverse electron demand aza-Diels-Alder cycloaddition reaction. These works involve 1-Azadienes and enecarbamates to generate tetrahydropyridines with three contiguous stereocenters.The products were obtained as a single diastereomer in good yields and good enantiomeric excess. The modification of substrates at various positions was possible without influencing the efficiency of the reaction.In the second part, a cycloaddition reaction between quinones and enecarbamates was studied. The use of a backbone SPINOL phosphoric acid proved to be very effective, leading to optically active 2,3-Dihydrobenzofurans. The products are isolated in excellent yields and enantiomeric excesses, but low diastereomeric ratios. These can be improved by engaging enethiocarbamates.A cascade reaction may also be carried out by forming the quinone in situ with a hypervalent iodine reagent. The scope of our cycloaddition and its variant initiated by PIDA is substantial but still needs to be improved. Different hydroquinones will thus be evaluated. The cycloadducts will later be transformed to develop this methodology.The last part concerns a 1,3-Dipolar cycloaddition reaction between nitrones and enecarbamates. If the use of a phosphoric acid has not proved effective, using a copper phosphate is convincing. Initially, the reaction shown excellent results, unfortunately not reproducible. A rigorous optimization was necessary to obtain satisfactory results. This reaction requires an assessment of its extent. Transformations are also envisaged to enhance the methodology.

Carbonyl allylation and propargylation reactions have been an important tool for the stereocontrolled formation of carbon-carbon bonds for synthetic chemists. The chiral homoallylic and homopropargylic alcohols obtained from these reactions serve as versatile intermediates for the synthesis of natural and pharmaceutical products. Over the past three decades and continuing on, various synthetic groups around the globe have directed their research towards the efficient synthesis of these chiral moieties. In spite extensive research, asymmetric allylation and propargylation reactions remain an enduring challenge in organic chemistry. Chapter 1 of this thesis describes the first phosphoric acid catalyzed asymmetric allylboration of aldehydes. We found that the BINOL-derived phosphoric acids can efficiently catalyze the allylation reaction under specific conditions. Homoallylic alcohols were obtained in high yields and enantioselectivities from a wide variety of substrates. The optimized conditions were also found to be effective towards crotylboration of aldehydes. Chapter 2 describes the extension of the Br[o/]nsted acid catalyzed allylboration methodology to the propargylation of aldehydes. Homopropargylic alcohols were obtained with high selectivities with TRIP-PA as the catalyst. Synthesis of various important synthetic scaffolds from these chiral alcohols is also presented. The mechanistic insights studied by research groups of Kendall Houk and Jonathan Goodman have been outlined in chapter 3. These studies show that the major isomer is formed via a transition state involving the hydrogen bonding interaction between the hydroxyl group of the catalyst and the pseudoaxial oxygen of the boronate, with a stabilizing interaction of the phosphoryl oxygen to the formyl hydrogen. These insights helped us in developing new and highly efficient boronates that are described in the next chapter.

Chiral molecules as with biological activity are plentiful in nature and the chemical literature; however they represent a smaller portion of the pharmaceutical drug market. As asymmetric methodologies grow more powerful, the tools are becoming available to synthesize chiral molecules in an enantioselective and efficient manner. Recent breakthroughs in our understanding of phosphoric acid now allow for Lewis acid catalysis via pairing with alkaline earth metals. Using alkaline earth metals with chiral phosphates is an emerging approach to asymmetric methodology, but already has an influential record. The development of new conditions for the phosphoric acid-catalyzed highly enantioselective ring-opening of meso-aziridines with a series of functionalized aromatic thiol nucleophiles is described in this thesis. This methodology utilizes commercially available aromatic thiols, a series of meso-aziridines, and a catalytic amount of VAPOL calcium phosphate to explore the substrate scope of this highly enantioselective reaction. Additionally, the development of new conditions for a catalytic asymmetric aza-Darzens aziridine synthesis mediated by a vaulted biphenanthrol (VAPOL) magnesium phosphate salt is described in this thesis. Using simple substrates, this methodology explores the scope and reactivity of a new magnesium catalyst for an aziridination reaction capable of building chirality and complexity simultaneously.

Thesis - Amsterdam.

Orientador: Rosehelene Marotta de Araújo / Banca: Silvio José Mauro / Banca: Maria Amélia Maximo de Araujo / Resumo: A finalidade deste trabalho foi verificar a passagem do ácido fosfórico em diferentes concentrações em dentina profunda, situado a 0,3mm da câmara pulpar, e observar as• alterações morfológicas da dentina pelo MEV. Setenta e dois corpos de prova, molares e pré-molares humanos hígidos, foram utilizados para este trabalho onde foi exposta a dentina oclusal. Através da máquina especialmente elaborada para o corte dos dentes, foi cortada a dentina deixando-a com espessura de 0,3 mm acima do corno pulpar. Os dentes foram aleatoriamente divididos em seis grupos de dez dentes cada: grupo 1 - controle ( sem tratamento ácido); grupo 2- ácido fosfórico a 10% sem sílica; grupo 3- ácido fosfórico a 32% sem sílica; grupo 4 - ácido fosfórico à 35% com sílica; grupo 5 - ácido fosfórico a 3 7% sem sílica e grupo 6 - ácido fosfórico a 50% líquido. Foi alojado na câmara pulpar dos corpos de prova, um papel de tornassol que atapetasse toda esta câmara, a fim de que quando aplicado o ácido fosfórico nas suas diferentes concentrações, pudéssemos avaliar a passagem mesmo. Cada concentração do ácido foi aplicada por quinze segundos e lavadas com spray água/ar. Observamos que: a) não houve a passagem do ácido fosfórico através da dentina com as diferentes concentrações estudadas; b) o ácido fosfórico a 10% sem sílica em corte transversal,demonstrou abertura parcial dos túbulos dentinários; c) o ácido fosfórico a 32% sem sílica, 35% com sílica, 37% sem sílica e 50% líquido demonstraram alterações morfológicas semelhantes; d) houve remoção preferencial da dentina peritubular; e) a sílica contida no ácido fosfórico a 35% não foi totalmente removida após abundantes lavagens / Abstract: The purpose of this study was to verify acid penetration of phosphoric acid at variable concentrations, into deep dentin, located at 0,3 mm from the pulp chamber, and a.tso observe dentin morphological changes with S.E.M. Occlusal dentin of human sound molars and premolars was exposed totaling 72 specimens. A special designed device was used to section teeth, obtaining 0.3 mm of remaining dentin over pulp horns. Teeth were randomly assigned to six groups with ten teeth each: group 1 - Control (no acid conditioning); group 2 - 10 % phosphoric acid: group 3 - 32 % phosphoric acid; group 4 - 35 % phosphoric acid with silica; group 5 - 37 % phosphoric acid; group 6 - 50 % phosphoric acid solution. A pH indicating paper was placed on pulp chamber walls in order to verify acid penetration of acid etchants. Each etchant was applied for 15 seconds, spray rinsed and air dried Conclusions: a) no acid penetration occurred through dentin; b) dentin tubules were partially open in crosscut 10 % phosphoric acid specimens; c) similar morphological changes were found for 50 % solution, 37 %, 35 % and 32 % phosphoric acid groups; d) most structural removal occurred at peritubular dentin; e) silica from 35% acid gel was not completely removed from dentin surface after thorough rinsing. / Mestre

Made available in DSpace on 2015-01-26T13:21:25Z (GMT). No. of bitstreams: 0 Previous issue date: 1997-03-04Bitstream added on 2015-01-26T13:30:30Z : No. of bitstreams: 1 000036234.pdf: 4116221 bytes, checksum: 868e565d3f58d838039c7a0ba8c15bda (MD5) / A finalidade deste trabalho foi verificar a passagem do ácido fosfórico em diferentes concentrações em dentina profunda, situado a 0,3mm da câmara pulpar, e observar as• alterações morfológicas da dentina pelo MEV. Setenta e dois corpos de prova, molares e pré-molares humanos hígidos, foram utilizados para este trabalho onde foi exposta a dentina oclusal. Através da máquina especialmente elaborada para o corte dos dentes, foi cortada a dentina deixando-a com espessura de 0,3 mm acima do corno pulpar. Os dentes foram aleatoriamente divididos em seis grupos de dez dentes cada: grupo 1 - controle ( sem tratamento ácido); grupo 2- ácido fosfórico a 10% sem sílica; grupo 3- ácido fosfórico a 32% sem sílica; grupo 4 - ácido fosfórico à 35% com sílica; grupo 5 – ácido fosfórico a 3 7% sem sílica e grupo 6 - ácido fosfórico a 50% líquido. Foi alojado na câmara pulpar dos corpos de prova, um papel de tornassol que atapetasse toda esta câmara, a fim de que quando aplicado o ácido fosfórico nas suas diferentes concentrações, pudéssemos avaliar a passagem mesmo. Cada concentração do ácido foi aplicada por quinze segundos e lavadas com spray água/ar. Observamos que: a) não houve a passagem do ácido fosfórico através da dentina com as diferentes concentrações estudadas; b) o ácido fosfórico a 10% sem sílica em corte transversal,demonstrou abertura parcial dos túbulos dentinários; c) o ácido fosfórico a 32% sem sílica, 35% com sílica, 37% sem sílica e 50% líquido demonstraram alterações morfológicas semelhantes; d) houve remoção preferencial da dentina peritubular; e) a sílica contida no ácido fosfórico a 35% não foi totalmente removida após abundantes lavagens / The purpose of this study was to verify acid penetration of phosphoric acid at variable concentrations, into deep dentin, located at 0,3 mm from the pulp chamber, and a.tso observe dentin morphological changes with S.E.M. Occlusal dentin of human sound molars and premolars was exposed totaling 72 specimens. A special designed device was used to section teeth, obtaining 0.3 mm of remaining dentin over pulp horns. Teeth were randomly assigned to six groups with ten teeth each: group 1 - Control (no acid conditioning); group 2 - 10 % phosphoric acid: group 3 - 32 % phosphoric acid; group 4 - 35 % phosphoric acid with silica; group 5 - 37 % phosphoric acid; group 6 - 50 % phosphoric acid solution. A pH indicating paper was placed on pulp chamber walls in order to verify acid penetration of acid etchants. Each etchant was applied for 15 seconds, spray rinsed and air dried Conclusions: a) no acid penetration occurred through dentin; b) dentin tubules were partially open in crosscut 10 % phosphoric acid specimens; c) similar morphological changes were found for 50 % solution, 37 %, 35 % and 32 % phosphoric acid groups; d) most structural removal occurred at peritubular dentin; e) silica from 35% acid gel was not completely removed from dentin surface after thorough rinsing.