Esta tese de doutorado fundamentou-se na preparação e caracterização de suspensões de nanocápsulas contendo quercetina (QUE) e metoxicinamato de octila (MCO), como componente do núcleo central destes sistemas. As suspensões foram preparadas pelo método de deposição interfacial do polímero pré-formado e foram posteriormente caracterizadas através da determinação dos teores totais de QUE e MCO, das taxas de associação da QUE e do MCO às nanocápsulas, dos diâmetros médios de partículas e polidispersões, dos potenciais zeta e análises morfológicas. Avaliou-se neste estudo, a influência do tipo de tesioativo utilizado (Span 60® ou Epikuron 170®) sobre as características físico-químicas das suspensões de nanocápsulas. As formulações foram estudadas quanto a sua estabilidade frente à radiação UVA, durante um período de exposição de 15 dias. As suspensões apresentaram tamanhos de partícula inferiores a 500 nm e taxas de encapsulação próximas a 90 % para a QUE e MCO. Este teste permitiu verificar que as nanocápsulas são sistemas capazes de proteger parcialmente as substâncias nela associadas contra a fotodegradação. As formulações preparadas com Span 60® foram mais efetivas na proteção contra a fotodegradação tanto da QUE, quanto do MCO, no entanto, evidenciou-se que a presença destas duas substâncias contribuiu para a proteção de ambas. Os testes para avaliação do potencial antioxidante das nanocápsulas contendo QUE e MCO foram conduzidos em células de levedura de Saccharomyces cerevisiae durante um período de 35 h, com coletas em tempos específicos. Os resultados demonstraram que a presença das suspensões de nanocápsulas, contendo ambas as substâncias associadas, foi capaz de minimizar a mortalidade das células de levedura em presença do agente estressor. Além disso, foi possível perceber que este efeito de proteção se manteve ao final das 35 h comprovando a eficiência destes sistemas na liberação lenta de substâncias. As suspensões de nanocápsulas foram associadas a um gel hidrofílico e, após, foram aplicadas sobre a superfície cutânea para avaliação dos perfis de liberação do MCO após 3 e 6 h de incubação. Testes in vitro utilizando células de Franz, foram realizados para avaliar a liberação do MCO a partir das nanocápsulas. Para este experimento utilizou-se acetonitrila como solvente, devido sua capacidade de solubilizar o polímero permitindo estimar a quantidade total de MCO em cada camada da pele. Com a finalidade de avaliar a quantidade de MCO liberado por difusão das nanocápsulas nas diferentes camadas da pele com o passar do tempo (MCO livre) utilizou-se o miristato de isopropila como solvente, pois o mesmo não é capaz de solubilizar o polímero, mas solubiliza o MCO. Os resultados obtidos neste estudo demonstraram que o MCO permanece acumulado nas camadas mais superficiais da pele, sendo a epiderme a principal barreira para a passagem deste filtro pela pele. Após aplicação e transcorrido os tempos de estudo não foi possível recuperar MCO na derme e também no líquido receptor. A utilização do miristato de isopropila permitiu demonstrar que a liberação do MCO foi diferente dependendo das camadas da pele. Setenta e oito por cento de MCO foi liberado após 6 h na superfície cutânea e cerca de 40 % no estrato córneo, sendo que este percentual diminuiu em torno de 20 % nas camadas mais profundas da pele. Os resultados permitiram inferir que a liberação do MCO difere entre a superfície da pele e as demais camadas. / This work has been based on the development and characterization of nanocapsules containing quercetin (QUE) and octyl metoxycinnamate (OMC), used as oil core of these systems. The nanocapsule suspensions were prepared by interfacial deposition of preformed polymer. The suspensions were characterized in terms of QUE and OMC contents and associated drug (QUE) within the nanoparticles, morphology, pH, mean size and polydispersity, as well as the zeta potentials. The influence of the type of surfactant (Span 60® e Epikuron 170®) on the physicochemical characteristics of suspensions was evaluated. The stability of the different formulations was evaluated under UVA radiation for 15 days. The aim of this test was to evaluate the nanocapsules ability in protecting the loaded substances against the photodegradation. The nanocapsules presented particle sizes lower than 500 nm, negative zeta potential values and QUE and OMC total contents about 90 %. The encapsulation efficiencies for QUE were 100 %. After 15 days, the formulations prepared with Span 60® and QUE/OMC showed more than 80 % of QUE content. The formulation prepared exclusively with QUE showed a content of QUE around 50 %. The totality of OMC degraded in solution, while OMC remained around 15 % stable in the nanocapsules prepared with Span 60® and QUE. After UVA exposure, QUE and OMC concentrations remained higher for the nanocapsules than for the solutions. Furthermore, the nanoencapsulation of QUE and OMC, using Span 60® improved their photostability. The antioxidant properties of the QUE-loaded nanocapsule suspensions were also evaluated and for this test Saccharomyces cerevisiae cells were used during 35 h of incubation. QUE and OMC nanocapsule suspensions showed an important in vivo antioxidant activity against the damages caused by a stressor agent that lasted for 35 h. The longer bioactivity of those nanocapsules was probably related to the slowly release of the QUE. The nanocapsule suspensions were incorporated in gel or emulsion (O/W) formulations. OMC release profiles from nanocapsules were evaluated for 3 and 6 h. In vitro measurements using static Franz diffusion cells were performed to examine the release behavior of OMC from the nanocapsules. It was used acetonitrile as solvent because it is capable to dissolve the polymer shell of nanocapsules and the sunscreen. This method gave an estimation of the total amount of OMC (encapsulated and released) in each skin layer. A new skin treatment was used, which preserved the polymer shell of the particles. Isopropyl myristate was chosen as solvent because it is not able to solubilize the polymer but it is capable to solubilize OMC released from nanocapsules. These results demonstrated that the OMC accumulated in the upper skin layers. The viable epidermis seemed to be the limiting barrier for the progression of nanocapsules penetration in the skin. Independently of the skin treatment, the same amount of OMC was recovered in the dermis and no OMC was detected in the receptor compartment indicating the absence of nanocapsules in both compartments. Moreover, the use of isopropyl miristate showed that the OMC release was different depending on the skin level. Whereas 78 % of OMC was released after 6 h at the surface of the skin and around 40 % in the stratum corneum, this percentage decreased to 20 % in the deeper skin layers. It can be thus concluded that the OMC release profile is different between the surface and the viable skin.

<p>  </p> <p>Actinide complexes have been targeted for their potential in group transfer applications. The study of these metals, such as thorium and uranium, is essential to better understand the reactions these metals are capable of facilitating.  Hydrotris(pyrazolyl)borates such as hydrotris(3,5-dimethylpyrazolyl)-borate (Tp*) and hydrotris(pyrazolyl)-borate (Tp) are superbulky, scorpionate ligands that have previously been used to synthesize novel uranium complexes and probe the reactivity of these materials. Similar thorium analogs have also been synthesized, but their reactivity has yet to be explored in great depth. Tp*ThCl3(THF) and Tp2ThCl2 have been reproduced and investigated as possible starting materials for such reactivity studies. While the former was found to be largely unreactive, the latter presents promising reactivity for the synthesis of thorium-element multiple bonds, and a novel thorium imido, Tp2Th(NDipp)(THF), has been synthesized and characterized using this scaffold. </p> <p><br></p> <p>The reactivity of a uranium tetrakis(imido), [U(NDipp)4][K2], has also been investigated to probe the prospect of group transfer reactions for potential catalysis applications in the future. An isocyanate, PhNCO, was reacted with this compound; the observed product showed that group transfer was incomplete, and a four-membered metallocycle product is likely formed instead. The synthesis of a novel thorium tris(imido) has also been targeted, and preliminary results are outlined. </p>

No description available.

No description available.

Yes / Corneal ulcers, a leading cause of blindness in the developing world are treated inappropriately without prior microbiology assessment because of issues related to availability or cost of accessing these services. In this work we aimed to develop a device for identifying the presence of Gram-positive or Gram-negative bacteria or fungi that can be used by someone without the need for a microbiology laboratory. Working with branched poly (N-isopropyl acrylamide) (PNIPAM) tagged with Vancomycin, Polymyxin B, or Amphotericin B to bind Gram-positive bacteria, Gram-negative bacteria and fungi respectively, grafted onto a single hydrogel we demonstrated specific binding of the organisms. The limit of detection of the microbes by these polymers was between 10 and 4 organisms per high power field (100X) for bacteria and fungi binding polymers respectively. Using ex vivo and animal cornea infection models infected with bacteria, fungi or both we than demonstrated that the triple functionalised hydrogel could pick up all 3 organisms after being in place for 30 min. To confirm the presence of bacteria and fungi we used conventional microbiology techniques and fluorescently labelled ligands or dyes. While we need to develop an easy-to-use either a colorimetric or an imaging system to detect the fluorescent signals, this study presents for the first time a simple to use hydrogel system, which can be applied to infected eyes and specifically binds different classes of infecting agents within a short space of time. Ultimately this diagnostic system will not require trained microbiologists for its use and will be used at the point-of-care. / We gratefully acknowledge support for this research by the Well- come Trust which provided funding for Shivshetty, Swift and Pinnock (Grant 0998800/B/12/Z).

Polymers which are sensitive towards external physical, chemical and electrical stimuli are termed as ‘intelligent materials’ and are widely used in medical and engineering applications. Presently, polymers which can undergo a physical change when heat is applied at a certain temperature (cloud point) in water are well-studied for this property in areas of separation chemistry, gene and drug delivery and as surface modifiers. One example of such a polymer is the poly (N-isopropylacrylamide) PNIPAAM, where it is dissolved well in water below 32 oC, while by increasing the temperature further leads to its precipitation. In this work, an alternative polymer poly (2-(2-methoxy ethoxy)ethyl methacrylate-co- oligo(ethylene glycol) methacrylate) (P(MEO2MA-co-OEGMA)) is studied due to its biocompatibility and the ability to vary its cloud points in water. When a layer of temperature responsive polymer was attached to a single continuous porous piece of silica-based material known as a monolith, the thermoresponsive characteristic was transferred to the column surfaces. The hybrid material was demonstrated to act as a simple temperature ‘switch’ in the separation of a mixture of five steroids under water. Different analytes were observed to be separated under varying column temperatures. Furthermore, more complex biochemical compounds such as proteins were also tested for separation. The importance of this work is attributed to separation processes utilizing environmentally friendly conditions, since harsh chemical environments conventionally used to resolve biocompounds could cause their biological activities to be rendered inactive. / Polymere, welche empfindlich gegenüber externen physikalischen, chemischen und elektrischen Einflüssen sind, werden „intelligente Materialien“ genannt. Diese werden weitverbreitet in medizinischen und technischen Anwendungen eingesetzt. Auf diesem Gebiet ausführlich erforschte Materialien sind Polymere, welche durch Hitze bei einer bestimmten Temperatur (Trübungspunkt) eine physikalische Veränderung eingehen können, genannt thermoresponsive Polymere. Eingesetzt werden diese z.B. in chromatographischen Trennverfahren, in Gen- und Wirkstofftransport Vorgängen und zur Oberflächenmodifikation. Ein Beispiel für so ein Polymer ist das poly(N-isopropylacrylamide) PNIPAAM, welches unter 32 °C in Wasser gelöst vorliegt und mit Erhöhung der Temperatur als Niederschlag ausfällt. In dieser Arbeit wurde ein alternatives Polymer, das poly(2-(2-methoxyethoxy)ethylmethacrylate-co-oligo(ethyleneglycol) methacrylate) (P(MEO2MA-co-OEGMA)), untersucht, in Bezug auf Biokompatibilität und der Änderung des Trübungspunktes in Wasser. Wenn eine Schicht eines temperaturempfindlichen Polymers auf einen Monolithen (einteiliger, poröser und auf Silika-basierendes Material) aufgebracht wird, werden die thermoresponsiven Eigenschaften auf die Oberfläche dieses Monolithen übertragen. Der Monolith dient hier als Säule in einer HPLC-Anlage. Es wurde gezeigt, dass das Hybrid-Material als einfacher „Temperaturschalter“ in der Trennung von fünf verschiedenen Steroiden in Wasser agieren kann. Untersucht wurde die Separation verschiedener Analyten mit dem Variieren der Säulentemperatur. Zusätzlich wurden mehr komplexe biochemische Stoffe, wie Proteine, getestet. Die Bedeutung dieser Arbeit ist zurückzuführen auf Separationsprozesse, welche umweltfreundlichen Bedingungen nutzen, da die rauen chemischen Bedingungen in konventionellen Separationsprozessen die biologische Inaktivität der Verbindungen zur Folge haben können. Der zweite Teil der Arbeit beschäftigte sich mit der Entwicklung eines alternativen Trägermaterials als Ersatz zu den Silika-basierende Trennungssäulen. Kohlenstoffmaterialien sind aufgrund ihrer ausgezeichneten mechanischen Härte und chemischen Stabilität eine vielversprechend Alternative. Die Synthese von Kohlenstoffkugeln als Trägermaterial kann als „grüner“ Prozess in meiner Arbeit angesehen werden, da milde Synthesebedingungen in purem Wasser verwendet wurden. Die Leistungsfähigkeit des Materials wurde mit einer Serie von Separationsreaktionen gezeigt.

In the latest years, many studies especially on characterization and synthesis of polyoxazolines have been made. During these studies, new polyoxazolines such as poly(2-isopropyl-2-oxazoline) (PIPOX), poly(2-(3-butenyl)-2-oxazoline) (PBOX) and modified PBOX were synthesized. However, there has been no investigation on their thermal characteristics such as thermal stability and thermal degradation products. In this study, thermal degradation characteristics, thermal degradation products and thermal stability of PIPOX, PBOX and modified PBOX polymers PBOX-Perf, PBOX-Thiop, PBOX-Sug, PBOX-SP and PBOX-TP were investigated. In this study mercaptans 1H,1H,2H,2H-perfluoro-octanethiol, 3-mercapto-1,2 propanediol, thio-&beta / -D-glucose derivative and their mixture were used in PBOX modifications. The effect of modification of PBOX with different mercaptans on thermal characteristics was also analyzed. For the PIPOX, formations of protonated monomer and oligomers from dimer to heptamer were observed. However, when the isopropyl group changes with 3-butenyl group, protonated oligomers up to trimer were observed because the crosslinking formed during the polymerization of unsaturated butenyl inhibited the production of oligomers. In addition to this, thermal degradation at lower temperatures was observed. The change in thermal stability and thermal degradation products were observed as a result of modification of PBOX with different mercaptans. Unlike PBOX-Sug thermal degradation started at very low temperatures for PBOX-Thiop and PBOX-Perf. This degradation observed at lower temperatures disappeared for PBOX-SP and PBOX-TP. For PBOX-Perf, PBOX-Sug and PBOX- Thiop, decomposition of side chains at low temperatures and decomposition of the main chain at high temperatures were observed. Although the same thermal degradation behavior for PBOX-TP and PBOX-Thiop was expected, since PBOX-TP was obtained as a result of modification of PBOX with high amounts of mercaptan used in PBOX-Thiop and small amounts of mercaptan used in the PBOX-Perf, the results show that neither PBOX-Thiop nor PBOX-Perf thermal degradation behavior are dominant. This is also valid for PBOX-SP. PBOX-SP has higher thermal stability when compared to PBOX-Sug.

Esta investigação objetivou a eficácia antimicrobiana de agentes desinfetantes utilizados na desinfecção dos instrumentos endodônticos, durante o período transoperatório do tratamento endodôntico. A atividade antimicrobiana dos desinfetantes álcool isopropílico, acetona e ácido peracético (PAA) foi avaliada sobre microrganismos planctônicos através de teste de contato (time kill assay), utilizando inóculo de 9,9 X 109 a 1,2 X 1012 unidades formadoras de colônia (UFC) e por determinação da concentração bactericida mínima (CBM), usando inóculo de aproximadamente 106 UFC. Os agentes químicos também foram avaliados sobre Enterococcus faecalis (E. faecalis) ATCC 29212 cultivada em matriz de dentina (ex vivo) visando a formação de biofilme. O biofilme (organismos sésseis) microbiano foi removido com limas tipo Kerr (LK), até as lâminas estarem visualmente preenchidas. As LK contaminadas foram usadas como carreadores (logo após a contaminação ou secas dentro de uma câmara de fluxo laminar por 10 minutos). As LK carreadoras foram imersas em álcool isopropílico ou acetona ambos a 80%, ou em Ácido peracético 2%, por 30 ou 60 segundos. As limas foram posteriormente colocadas em tubos de ensaio contendo caldo Enterococcosel para observar o crescimento dos enterococos viáveis. Depois, os experimentos in vivo foram realizados com LK contaminadas por material necrótico pulpar da região cervical de dentes indicados para tratamento endodôntico. As LK contaminadas foram imersas, por 30 ou 60 segundos, em 80% de acetona ou 80% de álcool isopropílico ou 2% de PAA. As limas foram então inoculadas em tubos de ensaio contendo meio tioglicolato. Os organismos que cresceram, foram identificados após o tratamento com PAA. A corrosão mediada pelos agentes químicos também foi testada, após a incubação de LK de aço inoxidável e de NiTi por 60 minutos, medindo o peso das LK antes e depois da imersão e por microscopia eletrônica de varredura (MEV). Todos os agentes químicos foram capazes de eliminar ou reduzir a viabilidade das bactérias de espécies planctônicas Gram-negativas e Gram-positivas, embora a atividade dos produtos químicos sobre E. faecalis sésseis em testes de carreadores de LK demonstrou que o álcool isopropílico ou acetona foram incapazes de eliminar a contaminação bacteriana, especialmente, quando as limas foram secas previamente à exposição aos produtos químicos, por 15 ou 30 segundos. O PAA demonstrou a melhor atividade antimicrobiana e eliminou a viabilidade das células sésseis E. faecalis de ambas as limas endodônticas tipo K úmidas ou secas, após exposição por 15 segundos (100% de eliminação). Os experimentos desenvolvidos in vivo demonstraram que o PAA foi o agente mais eficaz (p<0,05), capaz de eliminar a viabilidade dos organismos em 92% das LK imersas depois de 60 segundos, quando comparado com acetona (64%) ou com álcool isopropílico (50%). O crescimento microbiano após o contato com o PAA demonstrou que somente o grupo dos Lactobacillus sp foi resistente a essa substância química. Os agentes químicos não demonstraram ser corrosivos, após a imersão por 1 hora, tanto por pesagem quanto por MEV. Foi observado que o PAA foi o agente mais eficaz para ser utilizado como desinfetante de instrumentos, durante o período transoperatório do tratamento endodôntico. / This investigation aimed to evaluate the antimicrobial efficacy of disinfectant agents used to maintain the disinfection of endodontic instruments during the transoperatory period in endodontic treatment. The antimicrobial activity of disinfectants isopropyl alcohol, acetone and peracetic acid were evaluated upon planktonic micro-organisms by time kill assay (contact test) using inoculums from 9,9 X 109 to 1,2 X 1012 colony forming units (CFU) and determination of minimal bactericidal concentration (MBC), using inoculums of 106 CFU. Chemical agents were also evaluated upon Enterococcus faecalis (E. faecalis) ATCC 29212 strain grown on matrix dentin (ex vivo) for biofilm formation. Biofilm (sessile organisms) were removed with Kerr files until the blades were visually filled and contaminated K files used as carriers (shortly after contamination or dried inside a flow chamber for 10 minutes). K files carriers were immersed in 80% isopropyl alcohol, 80% acetone or in 2% peracetic acid for 30 or 60 seconds. The files were subsequently dispensed into test tubes containing Enterococcosel broth to observe the growth of viable enterococci. Thereafter, in vivo experiments were performed with K files contaminated with pulp necrotic material from cervical region of teeth indicated to endodontic treatment. The contaminated K files were immersed for 30 or 60 seconds in 80% acetone, 80% isopropyl alcohol and 2% peracetic acid. The files were then inoculated into test tubes containing tioglycolate medium. The organisms that grew after peracetic acid treatment were identified. The corrosion mediated by the chemical agents was also tested after incubation of stainless steel and NiTi K files for 60 minutes, by measuring the weight of K-files before and after immersion, and by scanning electron microscopy (SEM). All chemical agents were capable to eliminate or reduce bacterial viability of planktonic Gram-negative and Gram-positive species, though the activity of chemicals upon sessile E. faecalis in K-file carrier tests demonstrated that isopropyl alcohol or acetone were incapable to eliminate bacterial contamination, especially when the files were dried previously to the exposition to the chemicals for 15 or 30 seconds. Peracetic acid demonstrated the best antimicrobial activity, and eliminated the viability of sessile E. faecalis cells from both wet and dried K-endodontic files after exposition for 15 seconds (100% elimination). The experiments developed in vivo demonstrated that peracetic acid was the most effective agent (p<0,05), capable of eliminating the viability of organisms in 92% of K files immersed after 60 seconds, when compared to acetone (64%) or isopropyl alcohol (50%). The microbial grown after contact with peracetic acid demonstrated that only Lactobacillus sp group was resistant to this chemical. The chemical agents demonstrated to be non-corrosive after immersion for 1 hour, by both weighing and SEM. The results indicated that peracetic acid was the most effective agent to be used as disinfectant of instruments during transoperatory period of endodontic treatment.

Esta investigação objetivou a eficácia antimicrobiana de agentes desinfetantes utilizados na desinfecção dos instrumentos endodônticos, durante o período transoperatório do tratamento endodôntico. A atividade antimicrobiana dos desinfetantes álcool isopropílico, acetona e ácido peracético (PAA) foi avaliada sobre microrganismos planctônicos através de teste de contato (time kill assay), utilizando inóculo de 9,9 X 109 a 1,2 X 1012 unidades formadoras de colônia (UFC) e por determinação da concentração bactericida mínima (CBM), usando inóculo de aproximadamente 106 UFC. Os agentes químicos também foram avaliados sobre Enterococcus faecalis (E. faecalis) ATCC 29212 cultivada em matriz de dentina (ex vivo) visando a formação de biofilme. O biofilme (organismos sésseis) microbiano foi removido com limas tipo Kerr (LK), até as lâminas estarem visualmente preenchidas. As LK contaminadas foram usadas como carreadores (logo após a contaminação ou secas dentro de uma câmara de fluxo laminar por 10 minutos). As LK carreadoras foram imersas em álcool isopropílico ou acetona ambos a 80%, ou em Ácido peracético 2%, por 30 ou 60 segundos. As limas foram posteriormente colocadas em tubos de ensaio contendo caldo Enterococcosel para observar o crescimento dos enterococos viáveis. Depois, os experimentos in vivo foram realizados com LK contaminadas por material necrótico pulpar da região cervical de dentes indicados para tratamento endodôntico. As LK contaminadas foram imersas, por 30 ou 60 segundos, em 80% de acetona ou 80% de álcool isopropílico ou 2% de PAA. As limas foram então inoculadas em tubos de ensaio contendo meio tioglicolato. Os organismos que cresceram, foram identificados após o tratamento com PAA. A corrosão mediada pelos agentes químicos também foi testada, após a incubação de LK de aço inoxidável e de NiTi por 60 minutos, medindo o peso das LK antes e depois da imersão e por microscopia eletrônica de varredura (MEV). Todos os agentes químicos foram capazes de eliminar ou reduzir a viabilidade das bactérias de espécies planctônicas Gram-negativas e Gram-positivas, embora a atividade dos produtos químicos sobre E. faecalis sésseis em testes de carreadores de LK demonstrou que o álcool isopropílico ou acetona foram incapazes de eliminar a contaminação bacteriana, especialmente, quando as limas foram secas previamente à exposição aos produtos químicos, por 15 ou 30 segundos. O PAA demonstrou a melhor atividade antimicrobiana e eliminou a viabilidade das células sésseis E. faecalis de ambas as limas endodônticas tipo K úmidas ou secas, após exposição por 15 segundos (100% de eliminação). Os experimentos desenvolvidos in vivo demonstraram que o PAA foi o agente mais eficaz (p<0,05), capaz de eliminar a viabilidade dos organismos em 92% das LK imersas depois de 60 segundos, quando comparado com acetona (64%) ou com álcool isopropílico (50%). O crescimento microbiano após o contato com o PAA demonstrou que somente o grupo dos Lactobacillus sp foi resistente a essa substância química. Os agentes químicos não demonstraram ser corrosivos, após a imersão por 1 hora, tanto por pesagem quanto por MEV. Foi observado que o PAA foi o agente mais eficaz para ser utilizado como desinfetante de instrumentos, durante o período transoperatório do tratamento endodôntico. / This investigation aimed to evaluate the antimicrobial efficacy of disinfectant agents used to maintain the disinfection of endodontic instruments during the transoperatory period in endodontic treatment. The antimicrobial activity of disinfectants isopropyl alcohol, acetone and peracetic acid were evaluated upon planktonic micro-organisms by time kill assay (contact test) using inoculums from 9,9 X 109 to 1,2 X 1012 colony forming units (CFU) and determination of minimal bactericidal concentration (MBC), using inoculums of 106 CFU. Chemical agents were also evaluated upon Enterococcus faecalis (E. faecalis) ATCC 29212 strain grown on matrix dentin (ex vivo) for biofilm formation. Biofilm (sessile organisms) were removed with Kerr files until the blades were visually filled and contaminated K files used as carriers (shortly after contamination or dried inside a flow chamber for 10 minutes). K files carriers were immersed in 80% isopropyl alcohol, 80% acetone or in 2% peracetic acid for 30 or 60 seconds. The files were subsequently dispensed into test tubes containing Enterococcosel broth to observe the growth of viable enterococci. Thereafter, in vivo experiments were performed with K files contaminated with pulp necrotic material from cervical region of teeth indicated to endodontic treatment. The contaminated K files were immersed for 30 or 60 seconds in 80% acetone, 80% isopropyl alcohol and 2% peracetic acid. The files were then inoculated into test tubes containing tioglycolate medium. The organisms that grew after peracetic acid treatment were identified. The corrosion mediated by the chemical agents was also tested after incubation of stainless steel and NiTi K files for 60 minutes, by measuring the weight of K-files before and after immersion, and by scanning electron microscopy (SEM). All chemical agents were capable to eliminate or reduce bacterial viability of planktonic Gram-negative and Gram-positive species, though the activity of chemicals upon sessile E. faecalis in K-file carrier tests demonstrated that isopropyl alcohol or acetone were incapable to eliminate bacterial contamination, especially when the files were dried previously to the exposition to the chemicals for 15 or 30 seconds. Peracetic acid demonstrated the best antimicrobial activity, and eliminated the viability of sessile E. faecalis cells from both wet and dried K-endodontic files after exposition for 15 seconds (100% elimination). The experiments developed in vivo demonstrated that peracetic acid was the most effective agent (p<0,05), capable of eliminating the viability of organisms in 92% of K files immersed after 60 seconds, when compared to acetone (64%) or isopropyl alcohol (50%). The microbial grown after contact with peracetic acid demonstrated that only Lactobacillus sp group was resistant to this chemical. The chemical agents demonstrated to be non-corrosive after immersion for 1 hour, by both weighing and SEM. The results indicated that peracetic acid was the most effective agent to be used as disinfectant of instruments during transoperatory period of endodontic treatment.

Objetivo: Comparar in vitro la resistencia adhesiva a dentina de tres sistemas adhesivos universales con y sin aplicación de una sustancia neutralizadora de la capa inhibida de oxígeno. Materiales y métodos: La muestra estuvo conformada por 90 dientes bovinos, distribuidos aleatoriamente en 6 grupos (n=15): G1-Ambar™ Universal, G2-Tetric® N-bond, G3-Scotchbond™ Universal sin aplicación de sustancia inhibidora: alcohol Isopropílico y G4-Ambar™ Universal, G5-Tetric® N-bond, G6-Scotchbond™ Universal con aplicación de sustancia inhibidora. Los procedimientos adhesivos se realizaron según las indicaciones de cada fabricante y los procedimientos restauradores con cilindros (matrices tipo Tygon 4 x 2 mm) de resina compuesta Filtek™ Z350XT-A2. Las muestras fueron almacenadas en una estufa a 37°C (+/- 5°C) por 24 horas. Se evaluó la resistencia al cizallamiento a dentina en una máquina de ensayos universal Instrom (velocidad 0.5 mm/min/500N). Los resultados fueron analizados mediante estadística descriptiva (Media y desviación estándar) e inferencial (U Mann Whitney, Kruskal Wallis). Resultados: La media y desviación estándar registrada para los grupos con y sin aplicación de alcohol Isopropílico fue; Ambar™ Universal (13.7±5.7) (14.0±5.2), Tetric® N-Bond Universal (16.5±7.2) (14.2±3.9) y Scotchbond™ Universal (13.6±4.5) (18.3±7.5) respectivamente. No se encontraron diferencias estadísticamente significativas en la resistencia adhesiva a dentina de los adhesivos universales con (p=0.528) y sin (p=0.193) aplicación de la sustancia neutralizadora. Conclusión: Los valores de resistencia adhesiva a dentina de los sistemas adhesivos universales con y sin aplicación de alcohol Isopropílico como sustancia neutralizadora de la capa inhibida de oxígeno no presentaron diferencias estadísticamente significativas. / Objective: Compare in vitro bond strength to dentin of three universal adhesive systems with and without application of an oxygen-inhibited layer neutralizing substance. Materials and methods: The sample was composed by 90 bovine teeth, randomly distributed in 6 groups (n=15): G1-Ambar™ Universal, G2-Tetric® N-bond, G3-Scotchbond™ Universal without application of inhibiting substance: Isopropyl alcohol and G4-Ambar™ Universal, G5-Tetric® N-bond, G6-Scotchbond™ Universal with application of inhibiting substance. Then, the adhesive phase was made according to each group and restorative procedures with composite resin Filtek™ Z350XT-A2, according to the manufacturer´s instructions. It was made of tygon composite resin (4 x 2 mm). The samples were stored in an incubator at 37°C (+/- 5°C) for 24 hours. Subsequently, dentin shear strength was evaluated on an Instrom universal testing machine (speed 0.5 mm/min/500N load). The results were analyzed using descriptive (mean and standard deviation) and inferential (U Mann Whitney, Kruskal Wallis) statistics. Results: Mean and standard deviation registered for the groups with and without application of Isopropyl alcohol was; Ambar™ Universal (13.7±5.7) (14.0±5.2), Tetric® N-Bond Universal (16.5±7.2) (14.2±3.9) and Scotchbond™ Universal (13.6±4.5) (18.3±7.5) respectively. No found statistical significant differences between bond strength in dentin of the universal adhesives with (p=0.528) and without (p=0.193) application of the neutralizing substance. Conclusion: The values of bond strength in dentin of the universal adhesive systems with and without application of Isopropyl alcohol as neutralizing substance of the oxygen inhibited layer did not show statistically significant differences. / Tesis