Estudo de propriedades da resina acrílica termoativada por energia de micro-ondas frente às variações nos procedimentos de inclusão

On heat cured acrylic resins by microwaves energy the action of electromagnetic waves on methylmethacrylate promote the polymerization process. However, part of this energy is absorbed by the gypsum present in the flask and the function of this gypsum is to maintain the characteristics of specimen, nevertheless is unknown in the literature as the amount of water present in this gypsum affects the characteristics of acrylic resin. The proposal of this study was verified if dried gypsum influenced in some properties of the acrylic resins thermally activated by microwaves: presence of porosity, microhardness, roughness, flexural strength and dimensional change. Two different types of acrylic resin for complete denture were utilized: Lucitone 550 e Vipi-Wave and groups were formed: Lucitone 550, polymerization by microwave energy without gypsum treatment; Lucitone 550, polymerization by microwave energy with pretreatment gypsum; Vipi-Wave by microwave energy without gypsum treatment; Vipi Wave, polymerization by microwave energy with pretreatment gypsum; Lucitone 550 control group polymerization in hot water bath. For both situations were performed analysis of microhardness and porosity three different metallic shaped specimens were formed with followed dimensions: 2,0x2,0x2,0cm (8cm3); 2,0x2,0x1,0 (4cm3) e 2,0x2,0x0,5 (2cm3). Standardized wax specimens was used to prepare groups (n=9) and included in glass fiber flasks. The gypsum dry was made by microwave oven cycle (10min and 600W) and then the flasks were maintained in dry oven during two hours. Polymerizations of specimens were made and then polished. Wax patterns #7 obtained from the metal were embedded in plastic flask and following the processes of pressing and polymerization of the resin according to established groups. To evaluate the flexural strength, specimens 65mm x 10mm x 3.0mm from metallic patterns in bar format were made. ...

Self-assembly in aqueous solution of amphiphilic graft copolymers from oxidized carboxymethylcellulose

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

lmmittance electroanalysis in diagnostics

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

Capacitance spectroscopy and density functional theory

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

Efficiency comparison of hyperbranched polymers as toughening agents for a one-part epoxy resin

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

Relationship between composition and organizational levels of nanostructured systems formed by Oleth 10 and PPG-5-Ceteth-20 for potential drug delivery

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

Investigation of photoinduced electrical properties in the heterojunction TiO2/SnO2

TiO2/SnO2 thin films heterostructures were grown by the sol-gel dip-coating technique. It was found that the crystalline structure of TiO2 depends on the annealing temperature and the substrate type. TiO2 films deposited on glass substrate, submitted to thermal annealing until 550 degrees C, present anatase structure, whereas films deposited on quartz substrate transform to rutile structure when thermally annealed at 1100 degrees C. When structured as rutile, this oxide semiconductor has very close lattice parameters to those of SnO2, making easier the heterostructure assembling. The electrical properties of TiO2/SnO2 heterostructure were evaluated as function of temperature and excitation with different light sources. The temperature dependence of conductivity is dominated by a deep level with energy coincident with the second ionization level of oxygen vacancies in SnO2, suggesting the dominant role of the most external layer material (SnO2) to the electrical transport properties. The fourth harmonic of a Nd:YAG laser line (4.65 eV) seems to excite the most external layer whereas a InGaN LED (2.75 eV) seems to excite electrons from the ground state of a quantized interfacial channel as well as intrabandgap states of the TiO2 layer.

Influência do agente de união na resistência ao cisalhamento da interface titânio/polímero de vidro

There is little information regarding bond strengths of polyglass to metal alloys. This study evaluated the influence of bonding system on shear bond strength of a composite resin (Artglass/Heraeus Kulzer) to cast titanium (Ti). Twenty metallic structures (4mm in diameter, 5mm thick) of titanium grade I were cast shaped and abraded with 250mm aluminum oxide and separated into two groups. For each group was applied one bonding system (Siloc or Retention Flow) before opaque and dentin polymer superposition. This procedure was managed using teflon matrices. They were manipulated and polymerized according to the manufacturer's recommendations. The samples were stored in distilled water for 24 hours at 37º and thermocycled (5º and 55ºC/500 cycles). Shear bond strength tests were performed by using an Instron Universal testing machine at a crosshead speed of 5mm/min. Results were analyzed statistically with one-way ANOVA (a=0,5) and they indicated that the Retention Flow system was statistically better than Siloc (20.74 MPa and 11.65 MPa , respectively). It was possible to conclude that the bonding agent influenced the adhesion between polymer and cast titanium.

Durable bonds at the adhesive/dentin interface: an impossible mission or simply a moving target?

Composite restorations have higher failure rates, more recurrent caries and increased frequency of replacement as compared to dental amalgam. Penetration of bacterial enzymes, oral fluids, and bacteria into the crevices between the tooth and composite undermines the restoration and leads to recurrent decay and failure. The gingival margin of composite restora tions is particularly vulnerable to decay and at this margin, the adhesive and its seal to dentin provides the primary barrier between the prepared tooth and the environment. The intent of this article is to examine physico-chemical factors that affect the integrity and durability of the adhesive/dentin interfacial bond; and to explore how these factors act synergistically with mechanical forces to undermine the composite restoration. The article will examine the various avenues that have been pursued to address these problems and it will explore how alterations in material chemistry could address the detrimental impact of physico-chemical stresses on the bond formed at the adhesive/dentin interface.

Structural and functional evidence for membrane docking and disruption sites on phospholipase A2-like proteins revealed by complexation with the inhibitor suramin

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

Modificação de nanopartículas de óxido de ferro por dextranas

A modificação de nanopartículas de óxido de ferro tem sido motivo de diversos estudos devido ao grande potencial em aplicações tecnológicas, em especial a área biomédica, pela aliança das propriedades magnéticas dos óxidos com a funcionalidade que a dextrana confere a esse material. O presente trabalho tem como objetivo sintetizar e caracterizar o sistema óxido de ferro/dextranas. O óxido de ferro foi obtido pela reação de co-precipitação de sais de ferro (II) e ferro (III) - na razão molar 1:2 - com hidróxido de sódio e a modificação das partículas magnéticas se deu por dois métodos: (I) a co-precipitação na presença de dextrana e carboximetil dextrana e (II) a co-precipitação seguida da modificação. Para modificação proposta pelo método (II) se fez necessário enxertar a dextrana em ácido acrílico, utilizando o íon Ce(IV) como iniciador da reação de polimerização. Nessa etapa se averiguou a concentração de iniciador ótima para a síntese e, através da técnica de espectroscopia de infravermelho, se pode confirmar a eficiência do enxerto. A concentração 0,3% de íon Ce(IV) apresentou melhor distribuição de tamanho, obtidos por análises de microscopia eletrônica de varredura e espalhamento de luz dinâmico, sendo escolhida para síntese junto a partícula magnética. A difratometria de raio X permitiu determinar a formação de estrutura cristalina da magnetita e maghemita, que são muito parecidas entre si, porém os espectros de infravermelho apontaram desdobramentos da ligação Fe - O característica da maghemita. A relação Fe2+/ Fe3+ obtida por espectrofotometria também resultou em oxidação. A estabilidade coloidal dos sistemas foi avaliada através de medidas de potencial zeta. A modificação da partícula magnética com carboximetil dextrana foi equivalente para os dois métodos empregados, entretanto a modificação com ...

Filmes híbridos PMMA-siloxano modificados com nanotubos de carbono para proteção de materiais metálicos contra corrosão

Using the sol-gel process, organic-inorganic hybrid coatings were synthesized by incorporation of different concentrations of functionalized carbon nanotubes, to improve their mechanical strength and thermal resistance without changing its passivation character. The siloxane-PMMA hybrids were prepared by radical polymerization of methyl methacrylate (MMA) with 3-methacryloxipropiltrimethoxisilane (MPTS) using the thermal initiator benzoyl peroxide (BPO), followed by acid catalyzed hydrolysis and condensation of tetraethoxysilane (TEOS). The analysis of pristine and functionalized carbon nanotubes was carried out using Scanning Electron Microscopy, X-ray Photoelectron Spectroscopy and Raman Spectroscopy. Structural analysis of hybrids was performed by Nuclear Magnetic Resonance, Atomic Force Microscopy and Raman Spectroscopy. For analysis of mechanical strength and thermal stability were performed mechanical compression tests and thermogravimetric analysis, respectively. Electrochemical Impedance Spectroscopy was used to evaluate the corrosion resistance in saline environment. The results showed an effective functionalization of carbon nanotubes with carboxyl groups and conservation of its structure. The hybrids showed high siloxane network connectivity and roughness of approximately 0.3 nm. The incorporation of carbon nanotubes in the hybrid matrix did not change significantly their thermal stability. Samples containing carbon nanotubes exhibit good corrosion resistance (on the order of MΩ in saline environment), but the lack of complete dispersion of carbon nanotubes in the hybrid, resulted in a loss of mechanical and corrosion resistance compared to hybrid matrix.

Influência do tratamento clareador e envelhecimento induzido sobre o brilho, cor, dureza e rugosidade superficial de resinas compostas

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Predição de vida em fadiga de compósitos estruturais baseado em análises dinâmico-mecânicas

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

Bone regeneration in surgically created deffects filled with autogenous bone: epifluorescence microscopy analysis in rats

Although the search for the ideal bone substitute has been the focus of a large number of studies, autogenous bone is still the gold standard for the filling of defects caused by pathologies and traumas, and mainly, for alveolar ridge reconstruction, allowing the titanium implants installation. OBJECTIVES: The aim of this study was to evaluate the dynamics of autogenous bone graft incorporation process to surgically created defects in rat calvaria, using epifluorescence microscopy. MATERIAL AND METHODS: Five adult male rats weighing 200-300 g were used. The animals received two 5-mm-diameter bone defects bilaterally in each parietal bone with a trephine bur under general anesthesia. Two groups of defects were formed: a control group (n=5), in which the defects were filled with blood clot, and a graft group (n=5), in which the defects were filled with autogenous bone block, removed from the contralateral defect. The fluorochromes calcein and alizarin were applied at the 7th and 30th postoperative days, respectively. The animals were killed at 35 days. RESULTS: The mineralization process was more intense in the graft group (32.09%) and occurred mainly between 7 and 30 days, the period labeled by calcein (24.66%). CONCLUSIONS: The fluorochromes showed to be appropriate to label mineralization areas. The interfacial areas between fluorochrome labels are important sources of information about the bone regeneration dynamics.