Effect of surface conditioning methods on the microtensile bond strength of resin composite to composite after aging conditions

Objectives. This study evaluated the effect of two different surface conditioning methods on the repair bond strength of a bis-GMA-adduct/bis-EMA/TEGDMA based resin composite after three aging conditions.Methods. Thirty-six composite resin blocks (Esthet X, Dentsply) were prepared (5 mm x 6 mm x 6 mm) and randomly assigned into three groups for aging process: (a) immersion in citric acid (pH 3.0 at 37 degrees C, 1 week) (CA); (b) boiling in water for 8h (BW) and (c) thermocycling (x5000, 5-55 degrees C, dwell time: 30s) (TC). After aging, the blocks were assigned to one of the following surface conditioning methods: (1) silica coating (30 mu m SiOx) (CoJet, 3M ESPE) + silane (ESPE-Sil) (CJ), (2) phosphoric acid + adhesive resin (Single Bond, 3M ESPE) (PA). Resin composite (Esthet.X (R)) was bonded to the conditioned substrates incrementally and light polymerized. The experimental groups formed were as follows: Gr1:CA + PA; Gr2:CA + CJ Gr3:BW + PA; Gr4: BW + CJ; Gr5:TC + PA; Gr6: TC + CJ. The specimens were sectioned in two axes (x and y) with a diamond disc under coolant irrigation in order to obtain non-trimmed bar specimens (sticks, 10 mm x 1 mm x 1 mm) with 1 mm(2) of bonding area. The microtensile test was accomplished in a universal testing machine (crosshead speed: 0.5 mm min(-1)).Results. The means and standard deviations of bond strength (MPa +/- S.D.) per group were as follows: Gr1: 25.5 +/- 10.3; Gr2: 46.3 +/- 10.1; Gr3: 21.7 +/- 7.1; Gr4: 52.3 +/- 15.1; GrS: 16.1 +/- 5.1; Gr6, 49.6 +/- 13.5. The silica coated groups showed significantly higher mean bond values after all three aging conditions (p < 0.0001) (two-way ANOVA and Tukey tests, alpha = 0.05). The interaction effect revealed significant influence of TC aging on both silica coated and acid etched groups compared to the other aging methods (p < 0.032). Citric acid was the least aggressive aging medium.Significance. Chairside silica coating and silanization provided higher resin-resin bond strength values compared to acid etching with phosphoric acid followed by adhesive resin applications. Thermocycling the composite substrates resulted in the lowest repair bond strength compared to citric acid challenge or boiling in water. (C) 2006 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

Fluorescence probe study of the interaction between acrylic acid-co-ethyl methacrylate copolymers and sodium dodecylsulfate

The interaction between sodium dodecylsulfate (SDS) and acrylic acid (AA)-ethyl methacrylate (EMA) copolymers has been investigated using steady state fluorescence and conductimetric measurements to assess the effect of the polymer composition on the aggregation process. Micropolarity studies using the ratio between the emission intensities of the vibronic bands of pyrene (I-1/I-3) and the shift of the fluorescence emission of pyrene-3-carboxaldehyde show, that the interaction of SDS with AA-EMA copolymers occurs at surfactant concentrations smaller than that observed for the pure surfactant in water and depends on the copolymer composition. The increase of ethyl methacrylate in the copolymers lowers the critical aggregation concentration (CAC) due to the larger hydrophobic character of the polymer backbone. The formation of aggregates on the macromolecule is induced mainly, by hydrophobic interactions, but the process is also influenced by the ionic strength due to the counter-ions of the polyelectrolyte.

Lignoids; flavonoids and polyketides of Virola surinamensis

From the seeds of Virola surinamensis, which were collected near Altamira and near Maraba, Para State, Brazil, the following substances were isolated by chromatographic techniques: two dibenzylbutanediol lignans, dihydrocubebin and the new dihydrocubebin monolaurate, two furofuran lignans, sesamin and asarinin, three dibenzylbutyrolactol lignans, cubebin, β-O- methylcubebin and α-O-methylcubebin, one dibenzylbutyrolactone lignan, hinokinin, one aryltetralin neolignan, galbulin, two tetrahydrofuran neolignans, galgravin and the new 4'-hydroxy-3'-methoxy-3,4-methylenedioxy- 8.8',7.O.7'-neolignan, one flavone, tithonine, one isoflavone, irisolidone, and two new polyketides, 3-hydroxy-1-(15-phenylpentadecanoyl)-2,6- cyclohexanedione and 1-(5-phenylpentanoyl)-2,6-cyclohexanedione. Different chemical constitutions of the fruits from the two localities were observed.

Responsabilidad social corporativa en América Latina: una visión empresarial

Incluye Bibliografía

Expenditures, investment and financing for sustainable development in Trinidad and Tobago

Includes bibliography

Avaliação da atividade antiulcerogênica dos extratos e frações das folhas de Mouriri elliptica Mart. (Melastomataceae) e Byrsonima basiloba A. Juss. (Malpighiaceae)

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Estimativas de parâmetros genéticos para características de crescimento e de carcaça em ovinos de corte

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Análise modal de uma estrutura do tipo viga utilizando materiais piezelétricos (PVDF) como sensores

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)