Avaliação da microdureza de resinas compostas submetidas a quatro tecnicas de fotoativação

Orientador: Luiz Andre Freire PimentaDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Odontologia de PiracicabaMestrad

Comportamento dos sistemas adesivos com fluor frente ao desafio cariogenico

Orientador: Giselle Maria Marchi BaronTese (doutorado) - Universidade Estadual de Campinas, Faculdade de Odontologia de PiracicabaResumo: O objetivo deste estudo foi avaliar o comportamento de sistemas adesivos com e sem flúor frente à indução química dinâmica (ciclagem de pH) de cárie secundária , por meio dos testes de microtração, análise da profundidade da lesão de cárie e quantificação da liberação de flúor. Foram utilizadas 80 coroas de incisivos bovinos, as quais tiveram a dentina vestibular exposta. Sobre essa dentina, foram confeccionados blocos de restaurações utilizando quatro sistemas adesivos (n=20), sendo dois sem flúor (Single Bond e Clearfil SE Bond), e dois com flúor (Optibond Solo Plus e Clearfil Protect Bond), além do compósito resinoso Filtek Z250. Após a confecção das restaurações, metade dos corpos-de-prova foi submetida à indução química de cárie e a outra metade foi considerada controle. Foram realizados sete cortes seriados, com espessura de aproximadamente 1 mm, para obtenção de seis fatias, nas quais foram confeccionadas constrições na interface de união de forma a obter-se uma área de, aproximadamente, 1 mm2. Em seguida, isolou-se as amostras com verniz para unha mantendo-se uma área de, aproximadamente, 4 mm2 de dentina exposta ao redor da interface de união. Esses espécimes foram submetidos à ciclagem de pH durante 4 dias, sendo 4 horas em solução desmineralizadora (DES) e 20 horas diárias imersas em solução remineralizadora (RE). Após a ciclagem, quatro espécimes de cada corpo-de-prova, assim como os espécimes dos grupos controles, foram submetidos ao ensaio de microtração, a uma velocidade de 0,5 mm/min até o momento da fratura. Após o ensaio, as duas porções fraturadas de cada espécime foram avaliadas em MEV para análise dos padrões de fratura. Os dois espécimes restantes dos corpos-de-prova ciclados foram avaliados quanto à profundidade de lesão formada em Microscópio de Luz Polarizada, nas distâncias de 5, 10 e 25µm a partir da interface de união. A concentração de íons flúor nas soluções DES-RE foi quantificada utilizando eletrodo específico calibrado com soluções preparadas com TISAB III. Os dados obtidos na resistência à microtração (MPa) e na avaliação da profundidade da lesão (µm) foram submetidos à Análise de Variância e ao Teste Tukey (a=5%). Para resistência à microtração, independente do sistema adesivo testado, não foi verificada diferença significativa entre os espécimes do grupo controle. Após a ciclagem, foi observada uma redução nos valores de resistência de união significativa para todos os adesivos, mantendo-se, no entanto a ausência de diferença significativa entre os adesivos. Em relação à profundidade de cárie, houve apenas diferença significativa entre os adesivos na distância de 5µm, na qual o adesivo com flúor Optibond Solo Plus apresentou menor lesão. Para a quantificação de flúor, encontrou-se concentração de flúor abaixo de 0,03 ppm, ou seja, abaixo da curva de sensibilidade do eletrodo. Pode-se concluir que a cárie secundária reduziu a resistência de união das restaurações e o flúor presente nos sistemas adesivos não se mostrou efetivo na manutenção dos valores de resistência de união e redução da profundidade da lesão após indução de cárie secundáriaAbstract: The aim of this study was to investigate the behavior of fluoride-free and fluoride-containing adhesive systems subject to dynamic chemical induction of secondary caries, by means of the microtensile bond strength test, establishment of carious lesion depth and the amount of fluoride-ion release from each adhesive system. Eighty extracted bovine incisors were ground flat to expose the labial dentine surface. The Filtek Z250 composite resin and four adhesives systems, two fluoride-free (Single Bond and Clearfil SE Bond) and two-fluoride containing adhesive systems (Optibond Solo Plus and Clearfil Protect Bond), were used for the construction of bulk restorations (n=20) over the flat dentin surfaces. After bonding, half of the specimens were subjected to carious chemical induction and the other half was the control group. The specimens were serially sectioned into 6 slabs with approximately 1.0 mm width that were trimmed to a 1 mm2 cross-sectional area at the bonded interface. Nail varnish was used to cover the dentin surface, leaving an area of 4 mm2 around the bonded interface. The specimens were, then, subject to 4-day chemical cycling, comprising immersion on remineralising (RE) and demineralising (DES) solutions for, respectively, 20 hours and 4 hours per day. Microtensile bond strength test of 4 specimens from both the chemical cycling and control groups were performed using a universal testing machine at a crosshead speed of 0.5 mm/min until fracture. SEM observations of the fracture surfaces were perform to evaluate the fracture pattern of the specimens. Polarized Light Microscope was used for the establishment of carious lesion deepness at 5, 10 and 25µm from the bonded interface of the remaining two specimens subject to the chemical challenge. A specific electrode calibrated with solutions prepared with TISAB III was used to determine the amount of fluoride-ion release present in the DES-RE solutions. Data of mean bond strengths (MPa) and carious lesion depth (µm) were analyzed with ANOVA and Tukey test (a=5%). For the microtensile bond strength, regardless the adhesive system tested; there was no statistic significant difference between the specimens of control group. It was observed a significant reduction on the bond strength values for all adhesives systems after chemical cycling; however, there was no difference between the tested materials. For the deepness of carious lesion, a significant difference between the adhesive systems was only detected at the 5µm-distance, in which Optibond Solo Plus fluoride-containing adhesive system showed the smallest lesion formation. An amount of fluoride-ion release of less than 0.03 ppm (under the detection limit of the electrode) present on the DES-RE solutions was found. It could be concluded that the secondary carious reduced the restorations bond strength and the amount of fluoride-ion present at the adhesive systems was not effective in preserve the bond strength values after caries chemical induction as well as in the reduction of carious lesion deepnessDoutoradoDentísticaDoutor em Clínica Odontológic

The effect of light-curing source and mode on microtensile bond strength to bovine dentin

PURPOSE: The purpose of this study was to evaluate the effects of different light-curing techniques on the microtensile bond strength of hybrid and packable resin composite to dentin. The null hypotheses were that different light-curing techniques do not affect the adhesion of resin composites to tooth structure and that different resin composites do not have a similar bond to dentin. MATERIALS AND METHODS: One hundred four box-shaped buccal preparations were made and dentin/enamel adhesive was applied according to the manufacturer's instructions (Single Bond 3M ESPE). A hybrid resin composite (Filtek Z250, A2, 3M ESPE) or a packable resin composite (Solitaire 2, A2, Heraeus Kulzer) were inserted in bulk and polymerized using one of these techniques (n = 13): (a) Soft-start (SS) using a halogen lamp (QTH); (b) LED low intensity; (c) Plasma arc (PAC) curing for 6 s for packable resin composite and 3 s for the hybrid resin composite; (d) Conventional (C) QTH curing for 40 s. Afterwards, specimens were thermocycled 1,000 times between 5 degrees C and 55 degrees C in tap water, and were sectioned into beams with a rectangular cross-sectional area of approximately 1 mm2. Microtensile bond strength testing was performed using a universal testing machine at a crosshead speed of 0.5 mm/min. RESULTS: Bond strength means +/- (SD) in MPa were: Filtek Z250: SSQTH = 17.9 (5.4); LED = 17.9 (6.4); PAC = 16.8 (6.8); CQTH = 16.1 (4.6). Solitaire 2: SSQTH = 12.4 (6.4); LED = 15.5 (4.3); PAC = 16.2 (4.4); CQTH = 13.8 (5.7). The data were structured in a split-plot design and analyzed by a two-way ANOVA and Tukey's tests (alpha = 0.05). CONCLUSION: The light-curing method did not significantly affect bond strengths. However, the bond strengths of the packable resin composite were significantly lower than those of the hybrid resin composite for all polymerization techniques, suggesting that the restorative material itself might be a more critical factor in adhesion than the curing method

Isotretinoin: action on mice tooth germs and palate

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Evaluation of marginal microleakage in Class II cavities: Effect of microhybrid, flowable, and compactable resins

Objective: The goal of the present study was to evaluate the microleakage on the cementum/dentin and enamel surfaces in Class II restorations, using different kinds of resin composite (microhybrid, flowable, and compactable). Method and materials: Forty human caries-free molars were extracted and selected. Eighty Class II standardized cavities were made in the cervical wall at the cementoenamel junction (CEJ) and at the mesial and distal surfaces. The teeth were divided into four groups: G1 - adhesive system + microhybrid resin composite Z100; G2 - adhesive system + compactable resin composite Prodigy Condensable; G3 - adhesive system + flowable resin composite Revolution + Z100 resin composite; G4 - adhesive system + Revolution fluid resin + compactable resin composite Prodigy Condensable. The adhesive system used in this study was Scotchbond Multi-Purpose Plus. The specimens were thermocycled in baths of 5°C and 55°C for 1,000 cycles and immersed in 50% silver nitrate solution. The specimens then were sectioned and evaluated on degree of dye penetration. Results: The results were evaluated using the nonparametric Kruskall-Wallis test, which showed a statistically significant difference between groups G1 and G4, G2 and G4, and G3 and G4. Conclusions: None of the materials was able to eliminate the marginal microleakage at the cervical wall; the application of a low-viscosity resin composite combined with a compactable resin composite significantly decreased the microleakage

Effect Of Different Light-curing Devices And Aging Procedures On Composite Knoop Microhardness.

The aim of this study was to evaluate the effect of light-curing devices (Halogen/HAL, Light Emitting Diodes/LED, Argon Laser/LAS and Plasma Arc/PAC) and aging procedures (Mechanical Cycling/MC, Thermal Cycling/TC, Storage/S, MC+TC and MC+TC+S) on the micro-hardness of bottom/B and top/T surfaces of 2-mm-high composite resin cylinders. The Knoop microhardness test (25 g, 20 s) on both B and T was performed before and after each aging procedure. For B and T, before aging procedures, PAC showed reduced polymerization effectiveness when compared with HAL. In the T, after TC, PAC and LAS had also showed reduced polymerization effectiveness when compared to HAL and LED. For all light-curing devices, MC+TC+S and S affected the Knoop microhardness values. In the B, no difference could be observed among the aging procedures for PAC. From all light-curing units, PAC may have rendered composites of reduced quality and the storage aging procedures were the most harmful to the polymer hardness.23473-

Effect of different light-curing devices and aging procedures on composite knoop microhardness

The aim of this study was to evaluate the effect of light-curing devices (Halogen/HAL, Light Emitting Diodes/LED, Argon Laser/LAS and Plasma Arc/PAC) and aging procedures (Mechanical Cycling/MC, Thermal Cycling/TC, Storage/S, MC+TC and MC+TC+S) on the micro-hardness of bottom/B and top/T surfaces of 2-mm-high composite resin cylinders. The Knoop microhardness test (25 g, 20 s) on both B and T was performed before and after each aging procedure. For B and T, before aging procedures, PAC showed reduced polymerization effectiveness when compared with HAL. In the T, after TC, PAC and LAS had also showed reduced polymerization effectiveness when compared to HAL and LED. For all light-curing devices, MC+TC+S and S affected the Knoop microhardness values. In the B, no difference could be observed among the aging procedures for PAC. From all light-curing units, PAC may have rendered composites of reduced quality and the storage aging procedures were the most harmful to the polymer hardness