Avaliação da resistência de união da resina composta ao esmalte desmineralizado submetido à remineralização e infiltração resinosa de lesão de cárie

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Influence of Ozone Gas and Ozonated Water Application to Dentin and Bonded Interfaces on Resin-Dentin Bond Strength

Purpose: To assess the influence of ozone gas and ozonated water application to prepared cavity and bonded interfaces on the resin/dentin bond strength of two-step etch-and-rinse adhesive systems (Adper Single Bond 2 [SB2] and XP-Bond [XP]). Materials and Methods: Sixty extracted human third molars were sectioned perpendicularly to their long axes to expose flat occlusal dentin surfaces. In experiment 1, dentin was treated with ozone before the bonding procedure, while in experiment 2, ozone was applied to resin/dentin bonded interfaces. In experiment 1, dentin surfaces were treated either with ozone gas (2100 ppm), ozonated water (3.5 ppm), or distilled water for 120 s, and then bonded with SB2 or XP according to manufacturers' instructions. Hybrid composite buildups were incrementally constructed and the teeth were sectioned into resin-dentin sticks (0.8 mm(2)). In experiment 2, dentin surfaces were first bonded with SB2 or XP, composite buildups were constructed, and bonded sticks obtained. The sticks were treated with ozone as previously described. Bonded sticks were tested under tensile stress at 1 mm/min. Silver nitrate impregnation along the resin/dentin interfaces was also evaluated under SEM. Results: Two-way ANOVA (adhesive and ozone treatment) detected no significant effect for the cross-product interaction and the main factors in the two experiments (p > 0.05), which was confirmed by the photomicrographs. Conclusion: Ozone gas and ozonated water used before the bonding procedure or on resin/dentin bonded interfaces have no deleterious effects on the bond strengths and interfaces.

Degradation of the resin-dentin bonds after simulated and inhibited cariogenic challenge in an in situ model

The aim of this study was to evaluate the resindentin bonds of two simplified etch-and-rinse adhesive after simulated cariogenic and inhibited cariogenic challenge in situ. Dental cavities (4 mm wide, 4 mm long, and 1.5 mm deep) were prepared in 60 bovine teeth with enamel margins. Restorations were bonded with either adhesive Adper Single Bond 2 (3MESPE) or Optibond Solo Plus (Kerr). Forty restorations were included in an intra-oral palatal appliance that was used for 10 adult volunteers while the remaining 20 dental blocks were not submitted to any cariogenic challenge [NC group] and tested immediately. For the simulated cariogenic challenge [C+DA], each volunteer dropped 20% sucrose solution onto all blocks four times a day during 14 days and distilled water twice a day. In the inhibited cariogenic challenge group [C + FA], the same procedure was done, but slurry of fluoride dentifrice (1.100 ppm) was applied instead of water. The restored bovine blocks were sectioned to obtain a slice for cross-sectional Vickers microhardness evaluation and resindentin bonded sticks (0.8 mm2) for resindentin microtensile evaluation. Data were evaluated by two-way ANOVA and Tukey's tests (a = 0.05). Statistically lower microhardness values and degradation of the resindentin bonds were only found in the C + DW group for both adhesives. The in situ model seems to be a suitable short-term methodology to investigate the degradation of the resindentin bonds under a more realistic condition. (c) 2012 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 100B: 14661471, 2012.

Bond strength of adhesives to dentin contaminated with smoker's saliva.

The purpose of this study was to determine the effects of contamination with smoker's and non-smoker's saliva on the bond strength of resin composite to superficial dentin using different adhesive systems. The interfacial structure between the resin and dentin was evaluated for each treatment using environmental scanning electron microscopy (ESEM). Freshly extracted human molars were ground with 600-grit SiC paper to expose the superficial dentin. Adhesives [One-Up-Bond-F-Plus (OUFP) and Adper-Prompt-L-Pop (APLP)] and resin composite (TPHSpectrum) were bonded to the dentin (n = 8/group, 180 total specimens) under five surface conditions: control (adhesive applied following manufacturers' instructions); saliva, then 5-s air dry, then adhesive; adhesive, saliva, 5-s air dry; adhesive, saliva, 5-s water rinse, 5-s air dry (ASW group); and adhesive, saliva, 5-s water rinse, 5-s air dry, reapply adhesive (ASWA group). After storage in water at 37 degrees C for 24 h, the specimens were debonded under tension at a speed of 0.5 mm/min. ESEM photomicrographs of the dentin/adhesive interfaces were taken. Mean bond strength ranged from 8.1 to 24.1 MPa. Fisher's protected least significant difference (P = 0.05) intervals for critical adhesive, saliva, and surface condition differences were 1.3, 1.3, and 2.1 MPa, respectively. There were no significant differences in bond strength to dentin between contamination by smoker's and nonsmoker's saliva, but bond strengths were significantly different between adhesive systems, with OUFP twice as strong as APLP under almost all conditions. After adhesive application and contamination with either smoker's or nonsmoker's saliva followed by washing and reapplication of the adhesive (ASWA group), the bond strength of both adhesive systems was the same as that of the control group.

Resistencia adhesiva de dos agentes de fijación a base de resinas

Los agentes de fijación a base de resina autoacondicionantes - autoadhesivos (SE/SA) fueron desarrollados con el objetivo de simplificar la técnica de cementado a un solo paso, ahorrando tiempo y errores por parte del operador. El objetivo de este trabajo fue evaluar si dicha simplificación influye negativamente sobre los valores adhesivos tal como sucediera en los sistemas adhesivos a esmalte y dentina autoacondicionantes. Se confeccionaron 20 probetas de dentina en las cuales se cementaron probetas de resina compuesta: 10 muestras fueron cementadas con un cemento de grabado total (TE) y 10 con un cemento SE/SA y conservadas a 37 ºC y 100 % de humedad hasta su ensayo mecánico. Los resultados observados muestran una disminución en la resistencia adhesiva de los cementos SE/SA. Esto se explica por la menor traba micro mecánica generada por la presencia del barro dentinario y por el menor coeficiente de penetración de los monómeros modificados en estos cementos comparados con los cementos de resinas convencionales.

SU-8-Based Microchips for Capillary Electrophoresis and Electrospray Ionization Mass Spectrometry

Miniaturization of analytical instrumentation is attracting growing interest in response to the explosive demand for rapid, yet sensitive analytical methods and low-cost, highly automated instruments for pharmaceutical and bioanalyses and environmental monitoring. Microfabrication technology in particular, has enabled fabrication of low-cost microdevices with a high degree of integrated functions, such as sample preparation, chemical reaction, separation, and detection, on a single microchip. These miniaturized total chemical analysis systems (microTAS or lab-on-a-chip) can also be arrayed for parallel analyses in order to accelerate the sample throughput. Other motivations include reduced sample consumption and waste production as well as increased speed of analysis. One of the most promising hyphenated techniques in analytical chemistry is the combination of a microfluidic separation chip and mass spectrometer (MS). In this work, the emerging polymer microfabrication techniques, ultraviolet lithography in particular, were exploited to develop a capillary electrophoresis (CE) separation chip which incorporates a monolithically integrated electrospray ionization (ESI) emitter for efficient coupling with MS. An epoxy photoresist SU-8 was adopted as structural material and characterized with respect to its physicochemical properties relevant to chip-based CE and ESI/MS, namely surface charge, surface interactions, heat transfer, and solvent compatibility. As a result, SU-8 was found to be a favorable material to substitute for the more commonly used glass and silicon in microfluidic applications. In addition, an infrared (IR) thermography was introduced as direct, non-intrusive method to examine the heat transfer and thermal gradients during microchip-CE. The IR data was validated through numerical modeling. The analytical performance of SU-8-based microchips was established for qualitative and quantitative CE-ESI/MS analysis of small drug compounds, peptides, and proteins. The CE separation efficiency was found to be similar to that of commercial glass microchips and conventional CE systems. Typical analysis times were only 30-90 s per sample indicating feasibility for high-throughput analysis. Moreover, a mass detection limit at the low-attomole level, as low as 10E+5 molecules, was achieved utilizing MS detection. The SU-8 microchips developed in this work could also be mass produced at low cost and with nearly identical performance from chip to chip. Until this work, the attempts to combine CE separation with ESI in a chip-based system, amenable to batch fabrication and capable of high, reproducible analytical performance, have not been successful. Thus, the CE-ESI chip developed in this work is a substantial step toward lab-on-a-chip technology.

Influência da associação de catalisadores químicos na cimentação de pinos pré-fabricados de fibra de vidro

O objetivo deste estudo foi avaliar a Influência da associação de catalisadores químicos junto a diferentes sistemas adesivos autocondicionantes e cimentos resinosos de dupla polimerização, na cimentação de pinos pré-fabricados de fibra de vidro, quanto a sua resistência ao cisalhamento por extrusão - push out, seu grau de conversão e nanoinfiltração. Foram utilizadas trinta raízes bovinas extraídas, que tiveram seus canais obturados com guta-percha termoplastificada, divididas em três grupos: G1 - Adper SE Plus /Rely X ARC; G2- Adper SE Plus / Catalisador Scotchbond + Rely X ARC ; G3- Clearfil SE Bond / ED Primer + Panavia F. Após a cimentação dos pinos foram obtidas fatias das raízes, com 1mm de espessura, dos terços cervical (C), médio (M) e apical (A). O ensaio de resistência ao cisalhamento por extrusão foi realizado em máquina de ensaio universal EMIC D500 com carga de 100KN à velocidade de 1,0 mm/min, até o deslocamento do pino. Os dados obtidos no ensaio foram tabulados e submetidos à análise estatística. A análise de variância a dois critérios mostrou que apenas os fatores grupo e profundidade foram significativos, não sendo significativa a sua interação. O resultado do teste de Tukey (ρ≥0,05), para o fator grupo, mostrou que a menor média de resistência ao cisalhamento por extrusão foi obtida pelo grupo 3, que apresentou diferença estatística significativa para os grupos 1 e 2 que não diferiram entre si. Para o fator Profundidade a maior média foi obtida no terço cervical que apresentou diferença estatística significativa para os terços médio e apical que não diferiram entre si: A análise do grau de conversão foi feita após vinte e quatro horas e os fatores estudados foram os cimentos resinosos Panavia F e Rely X ARC e os catalisadores químicos ED Primer e Catalisador Scotchbond, na forma incorporada ou aplicada superficialmente aos cimentos, formando 10 grupos experimentais. Para o grau de conversão, o teste de Tukey mostrou que o catalisador químico não aumentou o grau de conversão do RelyX ARC, já para o Panavia F, este aumentou significativamente seu grau de conversão. Quanto a análise em MEV da nanoinfiltração para o fator grupo, o resultado do teste de Tukey (ρ≥0,05) mostrou que a maior média foi obtida pelo grupo 3 que apresentou diferença estatística significativa para os grupos 1 e 2, que não diferiram entre si. Para o fator Profundidade a maior média foi obtida no terço apical que apresentou diferença estatística significativa para o terço cervical, que não diferiu do terço médio. Conclusões: 1- A associação de catalisadores químicos não aumentou a resistência ao cisalhamento por extrusão dos pinos de fibra de vidro. 2- O cimento Panavia F é dependente de catalisador aumentar o grau de conversão. 3- A associação de catalisadores químicos não foi capaz de alterar o padrão da camada híbrida, representado pela nanoinfiltração. 4- A nanoinfiltração está associada inversamente ao grau de conversão dos sistemas de cimentação, o que contribui negativamente para a resistência adesiva de pinos de fibra de vidro.

Avaliação das fendas marginais em restaurações de resina composta com variação de alguns determinanates clínicos

O objetivo deste estudo foi comparar, por meio de mensuração das fendas na interface dentina - restauração de resina composta com utilização de algumas variáveis: fotoativação com lâmpada halógena e com LED; utilização de resina microhíbrida com partículas nanométricas Filtek Z350 ou sem estas partículas Filtek Z250; variação do sistema adesivo (Adper Single Bond 2 ou Adper Scotchbond Multi Purpose); variação da temperatura da resina composta; uso de dessensibilizante dentinário ou não; remoção do colágeno da dentina ou não e variação da intensidade de luz na fotoativação. Foram utilizados 70 molares humanos recém-extraídos, com cavidades circulares na dentina superficial de cada face proximal, foram divididos em 10 amostras para cada variável citada acima. Os dentes foram devidamente restaurados, seguindo as instruções dos fabricantes, para todos os grupos e mantidos em estufa bacteriológica por um período de 7 dias, após este período, foram polidos e as réplicas de resina epoxídica foram confeccionadas a partir de uma moldagem com silicone por adição, as mesmas foram levadas ao MEV, para a análise. As fendas foram mensuradas com o auxílio do software UTHSCSA Image tool e os dados foram submetidos à análise estatística pelo teste t de Student para a obtenção dos resultados. Com base nos resultados obtidos pode-se concluir que: os menores valores de fendas marginais foram obtidos quando da utilização de luz halógena (t=3,246 e p= 0,02) e com variação da intensidade desta luz (t= - 8,808 e p= 0,00). Os menores valores relativos de fendas, mas sem diferença estatística significante, foram encontrados, também, quando a resina Filtek Z350 foi comparada com a resina Filtek Z250 (t=-0,426 e p= 0,672) e quando o adesivo Adper Scotchbond Multi Purpose foi comparado com o Sistema Adper Single Bond 2 (t= 0,883 e p= 0,382). Os maiores valores de fendas marginais foram obtidos com a resina Filtek Z350 préaquecida a 60oC (t= -3,961 e p=0,000); com o uso de dessensibilizante dentinário (t=-3,062 e p=0,004) e com a remoção do colágeno pelo hipoclorito de sódio (t= -8,808 e p= 0,000).

The influence of substrate nucleation on HVPE-grown GaN thick films - art. no. 684105

Thick GaN films were grown on sapphire in a home-made vertical HVPE reactor. Effect of nucleation treatments on the properties of GaN films was investigated, including the nitridation of sapphire, low temperature GaN buffer and MOCVD-template. Various material characterization techniques, including AFM, SEM, XRD, CL and PL have been used to assess these GaN epitaxial films. It was found that the surface of sapphire after high temperature nitridation was flat and showed high density nucleation centers. In addition, smooth Ga-polarity surface of epitaxial layer can be obtained on the nitridation sapphire placed in air for several days due to polarity inversion. This may be caused by the atoms re-arrangement because of oxidation. The roughness of N-polarity film was caused by the huge inverted taper domains, which can penetrate up to the surface. The low temperature GaN buffer gown at 650 degrees C is favorable for subsequent epitaxial film, which had narrow FWHM of 307 arcsec. The epitaxial growth on MOCVD-template directly came into quasi-2D growth mode due to enough nucleation centers, and high quality GaN films were acquired with the values of the FWHM of 141 arcsec for (002) reflections. After etching in boiled KOH, that the total etch-pit density was only 5 x 106 cm(-2) illustrated high quality of the thick film on template. The photoluminescence spectrum of GaN film on the MOCVD-template showed the narrowest line-width of the band edge emission in comparison with other two growth modes.

Estabilidade de sistemas comutados com reset parcial

A presente tese é dedicada ao estudo da estabilidade de sistemas definidos por famílias finitas de sistemas lineares invariantes e por regras de comutação que coordenam a comutação entre eles. Assumimos que, em cada instante de tempo onde ocorre comutação, a trajectória do estado do sistema possa sofrer um "salto" desencadeado pela aplicação de um reset. Estes sistemas são, neste trabalho, designados por sistemas comutados com reset. Os resets podem ser de dois tipos - totais ou parciais, dependendo se a totalidade ou apenas uma parte das componentes do estado está disponível para reset. Neste sentido, distinguimos sistemas comutados com reset (total) e sistemas comutados com reset parcial. Analisamos a estabilidade dos dois tipos de sistemas comutados referidos à luz da teoria de Lyapunov e sob duas perspectivas; por um lado determinamos sob que condições um sistema comutado com reset é estável e por outro, identificamos resets que, quando aplicados, asseguram a estabilidade do sistema. Neste último ponto, a escolha dos resets adequados a aplicar pode por si só revelar-se insuficiente para obter estabilidade, especialmente se apenas parte das componentes do estado estiver disponível para reset (caso de reset parcial).

Étude des mécanismes moléculaires influençant la variation de phase des adhésines P, F1651 et CS31A présentes chez des souches d'Escherichia coli pathogènes.

F1651, les pili Pap et l’antigène CS31A associé aux antigènes de surface K88 sont tout trois des membres de la famille de type P des facteurs d’adhérence jouant un rôle prépondérant lors de l’établissement d’une maladie causée par des souches Escherichia coli pathogènes, en particulier des souches d’E. coli pathogènes extra-intestinales (ExPEC, Extra-intestinal pathogenic E. coli). Leur expression est sous le contrôle d’un mécanisme de régulation transcriptionnel dépendant de l’état de méthylation de l’ADN, résultant dans l’existence de deux populations définies, l’une exprimant l’adhésine (population ON) et l’autre ne l’exprimant pas (population OFF). Malgré de fortes identités de séquences, ces trois systèmes diffèrent l’un de l’autre, principalement par le pourcentage de cellules ON rencontrées. Ainsi, quand CS31A est systématiquement orienté vers un état considéré comme OFF, F1651 présente une phase ON particulièrement élevée et Pap montre deux états OFF et ON bien distincts, selon le phénotype de départ. La protéine régulatrice sensible à la leucine (Lrp, Leucine-responsive regulatory protein) joue un rôle essentiel dans la réversibilité de ce phénomène épigénétique et il est supposé que les différences de séquences au niveau de la région régulatrice modifient la localisation à ces sites de fixation de Lrp; ce qui résulte, en final, aux différences de phase existant entre CS31A, F1651 et Pap.À l’aide de divers techniques parmi lesquelles l’utilisation de gènes rapporteurs, mutagénèses dirigées et d’analyse des interactions ADN-protéines in vitro, nous montrons dans ce présent projet que la phase OFF prédominante chez CS31A est principalement due à une faible interaction de Lrp avec la région distale de l’opéron clp, et que la présence d’un homologue du régulateur local PapI joue un rôle également clef dans la production de CS31A. Dans le cas de F1651, nous montrons dans cette étude que le taux élevé de cellules en phase ON est dû à une altération dans le maintien de Lrp sur les sites répresseurs 1-3. Ceci est dû à la présence de deux nucléotides spécifiques, situé de part et d’autre du site répresseur 1, qui défavorisent la fixation de Lrp sur ce site précis. Tout comme dans le cas de CS31A, la formation d’un complexe, activateur ou répresseur de la phase ON, dépend également de l’action de du régulatuer local FooI, qui favorise alors le déplacement de Lrp des sites répresseurs 1-3 vers les sites activateurs 4-6.

Influence of pulse repetition rate of Er : YAG laser and dentin depth on tensile bond strength of dentin-resin interface

The study evaluated the in vitro influence of pulse-repetition rate of Er:YAG laser and dentin depth on tensile bond strength of dentin-resin interface. Dentin surfaces of buccal or lingual surfaces from human third molars were submitted to tensile test in different depths (superficial, 1.0 and 1.5 mm) of the same dental area, using the same sample. Surface treatments were acid conditioning solely (control) and Er:YAG laser irradiation (80 mJ) followed by acid conditioning, with different pulse-repetition rates (1, 2, 3, or 4 Hz). Single bond/Z-250 system was used. The samples were stored in distilled water at 37 degrees C for 24 h, and then the first test (superficial dentine) was performed. The bond failures were analyzed. Following, the specimens were identified, grounded until 1.0- and 1.5-mm depths, submitted again to the treatments and to the second and, after that, to third-bond tests on a similar procedure and failure analysis. ANOVA and Tukey test demonstrated a significant difference (p < 0.001) for treatment and treatment X depth interaction (p < 0.05). The tested depths did not show influence (p > 0.05) on the bond strength of dentin-resin interface. It may be concluded that Er:YAG laser with 1, 2, 3, or 4 Hz combined with acid conditioning did not increase the resin tensile bond strength to dentin, regardless of dentin depth. (C) 2007 Wiley Periodicals, Inc.

Effect of blood contamination on the shear bond strength at resin/dentin interface in primary teeth

Purpose: To assess in vitro the shear bond strength at the resin/dentin interface in primary teeth after contamination with fresh human blood. Methods: 75 crowns of primary molars were embedded in acrylic resin and mechanically ground to expose a flat dentin surface. The specimens were randomly assigned to five groups (n=15), according to the surface treatment. Group I (control) had no blood contamination. The other groups were blood-contaminated and subjected to different post-contamination protocols: in Group 2, the surfaces were rinsed with water; in Group 3, the surfaces were air-dried; in Group 4, the surfaces were rinsed and air-dried; and in Group 5, no post-contamination treatment was done. In all groups, a 3-mm dentin bonding site was demarcated, Single Bond adhesive system was applied and resin composite cylinders were bonded. After 24 hours in distilled water, shear bond strength was tested at a crosshead speed of 0.5 mm/minute. Results: Means (in MPa) were: Group 1: 7.1 (+/- 4.2); Group 2: 4.0 (+/- 1.8); Group 3: 0.9 (+/- 0.7); Group 4: 3.9 (+/- 2.2) and Group 5: 1.3 (+/- 1.5). Data were analyzed statistically by the Kruskal-Wallis test at 5% significance level. Groups 2 and 4 were similar to each other (P > 0.05) and both ware similar to Group 1 (P > 0.05). These groups (2, 3 and 4) had statistically significantly higher bond strengths than Groups 3 and 5 (P < 0.05). Blood contamination negatively affected the shear bond strength to primary tooth dentin. Among the blood-contaminated groups, water-rinsed specimens had higher bond strengths than those that were exclusively air-dried or not submitted to any post-contamination protocol before adhesive application.

Adhesion to Er : YAG laser-prepared dentin after long-term water storage and thermocycling

This in vitro study evaluated the microtensile bond strength of a resin composite to Er:YAG-prepared dentin after long-term storage and thermocycling. Eighty bovine incisors were selected and their roots removed. The crowns were ground to expose superficial dentin. The samples were randomly divided according to cavity preparation method (I-Er:YAG laser and II-carbide bur). Subsequently, an etch & rinse adhesive system was applied and the samples were restored with a resin composite. The samples were subdivided according to time of water storage (WS)/number of thermocycles (TC) performed: A) 24 hours WS/no TC; B) 7 days WS/500 TC; C) 1 month WS/2,000 TC; D) 6 months WS/12,000 TC. The teeth were sectioned in sticks with a cross-sectional area of 1.0-mm(2), which were loaded in tension in a universal testing machine. The data were subjected to two-way ANOVA, Scheffe and Fisher`s tests at a 5% level. In general, the bur-prepared group displayed higher microtensile bond strength values than the laser-treated group. Based on one-month water storage and 2,000 thermocycles, the performance of the tested adhesive system to Er:YAG-laser irradiated dentin was negatively affected (Group IC), while adhesion of the bur-prepared group decreased only within six months of water storage combined with 12,000 thermocycles (Group IID). It may be concluded that adhesion to the Er:YAG laser cavity preparation was more affected by the methods used for simulating degradation of the adhesive interface.

Long-term nano-mechanical properties of biomodified dentin-resin interface components

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)