Laboratory evaluation of the physicochemical properties of a new root canal sealer based on Copaifera multijuga oil-resin

Aim To compare a new root canal sealer based on Copaifera multijuga oil-resin (Biosealer) using three other established sealers (Sealer 26 (R), Endofill (R) and AH plus (R)) in terms of their physicochemical properties. Methodology The study was carried out according to the requirements of Specification Number 57 of the American Dental Association (ADA) and consisted of the following tests: setting time, flow, film thickness, dimensional stability, radiopacity and solubility/disintegration. Data were analysed statistically using anova and Tukey`s test for multiple comparisons. The significance level was set at 5% for all analyses. Results Sealer 26 (R) and AH Plus (R) had the longest setting time (P < 0.05). All materials presented flow in with the ADA`s guidelines. Regarding film thick-ness, Sealer 26 (R) did not have a satisfactory performance, as it had a higher mean value than the maximum allowed by the ADA (0.05 mm), being significantly different from the other materials (P < 0.05), which had mean values for film thickness in accordance with the ADA`s recommendations. Regarding the solubility and disintegration, only Endofill (R) did not meet the ADA`s specifications and presented the worst results of all materials (P < 0.05). Sealer 26 (R) presented the greatest dimensional changes and differed significantly from all other sealers (P < 0.05). Biosealer had the lowest radiopacity values and was significantly different from the other sealers (P < 0.05). Conclusion The experimental sealer based on Copaifera multijuga oil-resin presented satisfactory results in the physicochemical tests required by the ADA.

Influence of Post and Resin Cement on Stress Distribution of Maxillary Central Incisors Restored with Direct Resin Composite

The current study evaluated the influence of two endodontic post systems and the elastic modulus and film thickness of resin cement on stress distribution in a maxillary central incisor (MCI) restored with direct resin composite using finite element analysis (FEA). A three-dimensional model of an MCI with a coronary fracture and supporting structures was performed. A static chewing pressure of 2.16 N/mm(2) was applied to two areas on the palatal surface of the composite restoration. Zirconia ceramic (ZC) and glass fiber (GF) posts were considered. The stress distribution was analyzed in the post, dentin and cement layer when ZC and GF posts were fixed to the root canals using resin cements of different elastic moduli (7.0 and 18.6 GPa) and different layer thicknesses (70 and 200 mu m). The different post materials presented a significant influence on stress distribution with lesser stress concentration when using the GF post. The higher elastic modulus cement created higher stress levels within itself. The cement thicknesses did not present significant changes.

Structural characterization of supported nanocrystalline ZnO thin films prepared by dip-coating

Nanocrystalline ZnO thin films prepared by the sol-gel dip-coating technique were characterized by grazing incidence X-ray diffraction (GIXD), atomic force microscopy (AFM), X-ray reflectivity (XR) and grazing incidence small-angle X-ray scattering (GISAXS). The structures of several thin films subjected to (i) isochronous annealing at 350, 450 and 550 degrees C, and (ii) isothermal annealing at 450 degrees C during different time periods, were characterized. The studied thin films are composed of ZnO nanocrystals as revealed by analysing several GIXD patterns, from which their average sizes were determined. Thin film thickness and roughness were determined from quantitative analyses of AFM images and XR patterns. The analysis of XR patterns also yielded the average density of the studied films. Our GISAXS study indicates that the studied ZnO thin films contain nanopores with an ellipsoidal shape, and flattened along the direction normal to the substrate surface. The thin film annealed at the highest temperature, T = 550 degrees C, exhibits higher density and lower thickness and nanoporosity volume fraction, than those annealed at 350 and 450 degrees C. These results indicate that thermal annealing at the highest temperature (550 degrees C) induces a noticeable compaction effect on the structure of the studied thin films. (C) 2011 Elsevier B.V. All rights reserved.

Immobilization of liposomes in nanostructured layer-by-layer films containing dendrimers

Artificial vesicles or liposomes composed of lipid bilayers have been widely exploited as building blocks for artificial membranes, in attempts to mimic membrane interaction with drugs and proteins and to investigate drug delivery processes. In this study we report on the immobilization of liposomes of 1,2-dipalmitoyi-sn-Glycero-3-[Phospho-rac-(1-glycerol)] (Sodium Salt) (DPPG) in layer-by-layer (LbL) films, alternated with poly (amidoamine) G4 (PAMAM) dendrimer layers. The average size of the liposomes in solution was 120 nm as determined by dynamic light scattering, with their spherical shape being inferred from scanning electron microscopy (SEM) in cast films. LbL films containing up to 20 PAMAM/DPPG bilayers were assembled onto glass and/or silicon wafer substrates. The growth of the multilayers was achieved by alternately immersing the substrates into the PAMAM and DPPG solutions for 5 and 10 min, respectively. The formation of PAMAM/DPPG liposome multilayers and its ability to interact with BSA were confirmed by Fourier transform infrared spectroscopy (FTIR). The structural features and film thickness were obtained using X-ray diffraction and surface plasmon resonance (SPR). (c) 2007 Elsevier B.V. All rights reserved.

Characteristics of thin cellulose ester films spin-coated from acetone and ethyl acetate solutions

Spin-coated films of cellulose acetate (CA), cellulose acetate propionate (CAP), cellulose acetate butyrate (CAB) and carboxymethylcellulose acetate butyrate (CMCAB) have been characterized by ellipsometry, atomic force microscopy (AFM) and contact angle measurements. The films were spin-coated onto silicon wafers, a polar surface. Mean thickness values were determined by means of ellipsometry and AFM as a function of polymer concentration in solutions prepared either in acetone or in ethyl acetate (EA), both are good solvents for the cellulose esters. The results were discussed in the light of solvent evaporation rate and interaction energy between substrate and solvent. The effects of annealing and type of cellulose ester on film thickness, film morphology, surface roughness and surface wettability were also investigated.

Studies on the kinetics of ascorbate oxidation at a ruthenium oxide hexacyanoferrate modified electrode towards the detection at microenvironments

The electrocatalytic oxidation of ascorbate on a ruthenium oxide hexacyanoferrate (RuOHCF) glassy carbon (GC) modified electrode was investigated at pH 6.9 by using rotating disc electrode (RDE) voltammetry. The influence of the systematic variation of rotation rate, film thickness, ascorbate concentration and the electrode potential indicated that the rate of cross-chemical reaction between Ru(III) centres immobilized into the film and ascorbate controls the overall process. The kinetic regime may be classified as a Sk `` mechanism and the second order rate constant for the surface electrocatalytic reaction was found to be 1.56 x 10(-3) mol(-1) L-1 s(-1) cm. A carbon fibre microelectrode modified with the RuOHCF film was successfully used as an amperometric sensor to monitor the ascorbate diffusion in a simulated microenvironment experiment. (C) 2008 Elsevier B.V. All rights reserved.

Physical Vapor Deposited Thin Films of Lignins Extracted from Sugar Cane Bagasse: Morphology, Electrical Properties, and Sensing Applications

The concern related to the environmental degradation and to the exhaustion of natural resources has induced the research on biodegradable materials obtained from renewable sources, which involves fundamental properties and general application. In this context, we have fabricated thin films of lignins, which were extracted from sugar cane bagasse via modified organosolv process using ethanol as organic solvent. The films were made using the vacuum thermal evaporation technique (PVD, physical vapor deposition) grown up to 120 nm. The main objective was to explore basic properties such as electrical and surface morphology and the sensing performance of these lignins as transducers. The PVD film growth was monitored via ultraviolet-visible (UV-vis) absorption spectroscopy and quartz crystal microbalance, revealing a linear relationship between absorbance and film thickness. The 120 nm lignin PVD film morphology presented small aggregates spread all over the film surface on the nanometer scale (atomic force microscopy, AFM) and homogeneous on the micrometer scale (optical microscopy). The PVD films were deposited onto Au interdigitated electrode (IDE) for both electrical characterization and sensing experiments. In the case of electrical characterization, current versus voltage (I vs V) dc measurements were carried out for the Au IDE coated with 120 nm lignin PVD film, leading to a conductivity of 3.6 x 10(-10) S/m. Using impedance spectroscopy, also for the Au IDE coated with the 120 nm lignin PVD film, dielectric constant of 8.0, tan delta of 3.9 x 10(-3)) and conductivity of 1.75 x 10(-9) S/m were calculated at 1 kHz. As a proof-of-principle, the application of these lignins as transducers in sensing devices was monitored by both impedance spectroscopy (capacitance vs frequency) and I versus time dc measurements toward aniline vapor (saturated atmosphere). The electrical responses showed that the sensing units are sensible to aniline vapor with the process being reversible. AFM images conducted directly onto the sensing units (Au IDE coated with 120 nm lignin PVD film) before and after the sensing experiments showed a decrease in the PVD film roughness from 5.8 to 3.2 nm after exposing to aniline.

Estimation of the thickness and the optical parameters of several stacked thin films using optimization

The reverse engineering problem addressed in the present research consists of estimating the thicknesses and the optical constants of two thin films deposited on a transparent substrate using only transmittance data through the whole stack. No functional dispersion relation assumptions are made on the complex refractive index. Instead, minimal physical constraints are employed, as in previous works of some of the authors where only one film was considered in the retrieval algorithm. To our knowledge this is the first report on the retrieval of the optical constants and the thickness of multiple film structures using only transmittance data that does not make use of dispersion relations. The same methodology may be used if the available data correspond to normal reflectance. The software used in this work is freely available through the PUMA Project web page (http://www.ime.usp.br/similar to egbirgin/puma/). (C) 2008 Optical Society of America

Polymer toughening using residue of recycled windshields: PVB film as impact modifier

In this work, poly(vinyl butyral) (PVB) film originated from the mechanical separation of windshields was tested as all impact modifier of Polyamide-6 (PA-6). The changes undergone by PVB film during the recycling process and the blend manufacturing were evaluated by thermal analyses, infrared spectroscopy and loss oil ignition. Blends of PA-6/original PVB film and PA-6/recovered PVB film were obtained in concentrations ranging from 90/10 to 60/40. The mechanical properties of the blends were investigated and explained in light of the blends morphologies, which in turns were correlated to the changes undergone by the PVB film during the recycling process. The original film presented a plasticizer content of 33 wt.%, which decreased to as low as 20 wt.%, after the recycling and blend preparation processes. The PA-6/PVB film blends presented lower values of tensile strength and Young`s modulus than Polyamide-6, but all blends presented a dramatic increase in their toughness, with a special feature for the 40 wt.%(, blend, which resulted in a super toughened material (impact strength exceeding 500 J/m). Similar results were obtained with recovered PVB film and super tough blends were also obtained. The use of recovered PVB resulted in a smaller improvement of the impact strength due to the loss of plasticizer undergone during the recycling process. The morphological observations showed that if the interparticle distance is smaller than around 0.2 mu m (critical value), the notched Izod impact strength values increase considerably and the fracture surface of blends exhibit characteristics of tough failure. (C) 2007 Elsevier Ltd. All rights reserved.

TiAlN coatings deposited by triode magnetron sputtering varying the bias voltage

TiAlN films were deposited on AISI O1 tool steel using a triode magnetron sputtering system. The bias voltage effect on the composition, thickness, crystallography, microstructure, hardness and adhesion strength was investigated. The coatings thickness and elemental composition analyses were carried out using scanning electron microscopy (SEM) together with energy dispersive X-ray (EDS). The re-sputtering effect due to the high-energy ions bombardment on the film surface influenced the coatings thickness. The films crystallography was investigated using X-ray diffraction characterization. The X-ray diffraction (XRD) data show that TiAlN coatings were crystallized in the cubic NaCl B1 structure, with orientations in the {111}, {200} {220} and {311} crystallographic planes. The surface morphology (roughness and grain size) of TiAlN coatings was investigated by atomic force microscopy (AFM). By increasing the substrate bias voltage from -40 to -150 V, hardness decreased from 32 GPa to 19 GPa. Scratch tester was used for measuring the critical loads and for measuring the adhesion. (C) 2011 Elsevier B. V. All rights reserved.

Direct comparison of the bond strength results of the different test methods: A critical literature review

Objective. The goal of this paper is to undertake a literature search collecting all dentin bond strength data obtained for six adhesives with four tests ( shear, microshear, tensile and microtensile) and to critically analyze the results with respect to average bond strength, coefficient of variation, mode of failure and product ranking. Method. A PubMed search was carried out for the years between 1998 and 2009 identifying publications on bond strength measurements of resin composite to dentin using four tests: shear, tensile, microshear and microtensile. The six adhesive resins were selected covering three step systems ( OptiBond FL, Scotch Bond Multi-Purpose Plus), two-step (Prime & Bond NT, Single Bond, Clear. l SE Bond) and one step (Adper Prompt L Pop). Results. Pooling results from 147 references showed an ongoing high scatter in the bond strength data regardless which adhesive and which bond test was used. Coefficients of variation remained high (20-50%) even with the microbond test. The reported modes of failure for all tests still included high number of cohesive failures. The ranking seemed to be dependant on the test used. Significance. The scatter in dentin bond strength data remains regardless which test is used confirming Finite Element Analysis predicting non-uniform stress distributions due to a number of geometrical, loading, material properties and specimens preparation variables. This reopens the question whether, an interfacial fracture mechanics approach to analyze the dentin - adhesive bond is not more appropriate for obtaining better agreement among dentin bond related papers. (C) 2009 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

Healing of critical-size cranial defects in guinea pigs using a bovine bone-derived resorbable membrane

Purpose: To investigate the healing of critical-size cranial bone defects (9-mm-diameter) in guinea pigs treated with a bovine bone-derived resorbable membrane. Materials and Methods: A sample of 42 guinea pigs was divided into test (n = 20), control (n = 20), and standard (n = 2) groups. A full-thickness trephine defect was made in the fronto-parietal bone of each animal. In the test group, the internal and external openings of the defect were each closed with a separate membrane, and the space between them was filled with blood clot and a central spacer. In the control group, the defect was filled only with the blood clot and spacer. At 1, 3, 6, and 9 months later, the calvarias (5 per period) for both the test and control groups were collected, fixed, radiographed, and histologically processed. The Standard-group animals were sacrificed immediately after surgery and used to determine the initial size of defect radiographically. The areas of defects in the radiographs were measured with image-analysis software and were compared between groups and periods by multiple regression analysis with the Bonferroni correction. Results: At 1 and 3 months, newly formed woven bone was histologically observed in both test and control groups. Radiographically, this new bone occupied an average of 32% of the defect area at 1 month and 60% at 3 months in the test group. In the control group, 21% of the defect was filled at 1 month and 39% at 3 months. However, the differences between treatments were not statistically significant (P > .05). At 6 and 9 months, a significant increase in newly formed lamellar bone was seen histologically in both groups. Radiographically, for the test group, the new bone occupied an average of 82% of the defect area at 6 months and 96% at 9 months. For the control group, new bone composed an average of 45% of the defect area at 6 months and 40% at 9 months. The differences between the test and control groups were statistically significant at 6 and 9 months (P < .05). Complete or almost complete filling of the defect was observed in several cases. Conclusion: It was concluded that the bovine bone-derived membrane is highly biocompatible and is able to promote good healing of critical-size defects in calvaria of guinea pig.

Reappraisal of the effective elastic thickness for the sub-Andes using 3-D finite element flexural modelling, gravity and geological constraints

P>Estimates of effective elastic thickness (T(e)) for the western portion of the South American Plate using, independently, forward flexural modelling and coherence analysis, suggest different thermomechanical properties for the same continental lithosphere. We present a review of these T(e) estimates and carry out a critical reappraisal using a common methodology of 3-D finite element method to solve a differential equation for the bending of a thin elastic plate. The finite element flexural model incorporates lateral variations of T(e) and the Andes topography as the load. Three T(e) maps for the entire Andes were analysed: Stewart & Watts (1997), Tassara et al. (2007) and Perez-Gussinye et al. (2007). The predicted flexural deformation obtained for each T(e) map was compared with the depth to the base of the foreland basin sequence. Likewise, the gravity effect of flexurally induced crust-mantle deformation was compared with the observed Bouguer gravity. T(e) estimates using forward flexural modelling by Stewart & Watts (1997) better predict the geological and gravity data for most of the Andean system, particularly in the Central Andes, where T(e) ranges from greater than 70 km in the sub-Andes to less than 15 km under the Andes Cordillera. The misfit between the calculated and observed foreland basin subsidence and the gravity anomaly for the Maranon basin in Peru and the Bermejo basin in Argentina, regardless of the assumed T(e) map, may be due to a dynamic topography component associated with the shallow subduction of the Nazca Plate beneath the Andes at these latitudes.

Thickness and Annealing Temperature Effects on the Optical Properties and Surface Morphology of Layer-by-Layer Poly(p-phenyline vinylene) plus Dodecylbenzenesulfonate Films

The fabrication of controlled molecular architectures is essential for organic devices, as is the case of emission of polarized light for the information industry. In this study, we show that optimized conditions can be established to allow layer-by-layer (LbL) films of poly(p-phenylene vinylene) (PPV)+dodecylbenzenesulfonate (DBS) to be obtained with anisotropic properties. Films with five layers and converted at 110 degrees C had a dichroic ratio delta = 2.3 and order parameter r = 34%, as indicated in optical spectroscopy and emission ellipsometry data. This anisotropy was decreased with the number of layers deposited, with delta = 1.0 for a 75-layer LbL PPV + DBS film. The analysis with atomic force microscopy showed the formation of polymer clusters in a random growth process with the normalized height distribution being represented by a Gaussian function. In spite of this randomness in film growth, the self-covariance function pointed to a correlation between clusters, especially for thick films. In summary, the LbL method may be exploited to obtain both anisotropic films with polarized emission and regular, nanostructured surfaces. (c) 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 49: 206-213, 2011

Reprodutibilidade das mensurações da espessura das tábuas ósseas na tomografia computadorizada Cone-Beam utilizando diferentes protocolos de aquisição de imagem

INTRODUÇÃO: quanto menor a dimensão do voxel, maior a nitidez da imagem de tomografia computadorizada Cone-Beam (TCCB), porém, maior a dose de radiação emitida. OBJETIVOS: avaliar e comparar a reprodutibilidade da mensuração da espessura das tábuas ósseas vestibular e lingual em imagens de TCCB, utilizando diferentes protocolos de aquisição de imagem com variação da dimensão do voxel. MÉTODOS: exames de TCCB foram tomados de 12 mandíbulas humanas secas, com dimensão do voxel de 0,2; 0,3 e 0,4mm, no aparelho i-CAT Cone-Beam 3-D Dental Imaging System. No software i-CAT Viewer, foi mensurada a espessura das tábuas ósseas vestibular e lingual, em um corte axial passando 12mm acima do forame mentoniano do lado direito. A reprodutibilidade intraexaminador foi avaliada por meio da aplicação do teste t pareado. Para a comparação interexaminadores, foi utilizado o teste t independente. Os resultados foram considerados com o nível de significância de 5%. RESULTADOS: observou-se uma excelente reprodutibilidade interexaminadores para os três protocolos avaliados. A reprodutibilidade intraexaminadores foi muito boa, com exceção de algumas regiões dos dentes anteriores, que mostraram diferenças estatisticamente significativas, independentemente da dimensão do voxel. CONCLUSÃO: a mensuração da espessura das tábuas ósseas vestibular e lingual em imagens de TCCB mostrou boa precisão para exames obtidos com voxel de 0,2; 0,3 ou 0,4mm. A reprodutibilidade das mensurações na região anterior da mandíbula foi mais crítica do que na região posterior.