Surface roughness of packable composite resins polished with various systems

Purpose: The aim of this study was to evaluate the surface roughness of four packable composite resins, SureFil™ (Dentsply, Petrópolis, Rio de Janeiro, Brazil), Prodigy Condensable™ (Kerr Co., Orange, CA, USA), Filtek P60™ (3M do Brasil, São Paulo, Brazil), and ALERT® (Jeneric/Pentron, Inc., Wallingford, CT, USA) and one microhybrid composite resin (Filtek Z250™, 3M do Brasil) after polishing with four finishing systems. Materials and Methods: Twenty specimens were made of each material (5 mm in diameter and 4 mm high) and were analyzed with a profilometer (Perthometer® S8P, Perthen, Mahr, Germany) to measure the mean surface roughness (Ra). The specimens were then divided into four groups according to the polishing system: group 1 - Sof-Lex™ (3M do Brasil), group 2 - Enhance™ (Dentsply), group 3 - Composite Finishing Kit (KG Sorensen, Barueri, São Paulo, Brazil), and group 4 - Jiffy Polisher Cups® (Ultradent Products, Inc., South Jordan, UT, USA). The specimens were polished and then evaluated for Ra, and the data were subjected to analysis of variance, analysis of covariance, and Tukey's test (p = .05). Results: The mean Ra of SureFil polished with Sof-Lex was significantly lower than that of KG points. Prodigy Condensable polished with Enhance showed a significantly less rough surface than when polished with Sof-Lex. Filtek P60 did not exhibit a significant difference with the various polishing systems. For ALERT the lowest mean Ra was obtained with Sof-Lex and the highest mean Ra with KG points. Regarding Filtek Z250, polishing with KG and Jiffy points resulted in a significantly lower mean Ra than when polished with Enhance. Conclusions: Packable composite resins display variable roughness depending on the polishing system used; the Sof-Lex disks and Jiffy points resulted in the best Ra values for the majority of the materials tested.

The effect of adhesive and flowable composite on postoperative sensitivity: 2-Week results

Objective: To measure 2-week postoperative sensitivity in Class II composite restorations placed with a self-etching adhesive (Clearfil SE Bond) or a total-etch adhesive (Prime&Bond NT) with or without a flowable composite as cervical increment. Method and materials: Upon approval by the University of Guarulhos Committee on Human Subjects, 100 restorations were inserted in 46 patients who required Class II restorations in their molars and premolars. Enamel and dentin walls were conditioned with a self-etching primer (for Clearfil SE Bond) or etched with 34% phosphoric acid (for Prime&Bond NT). A 1- to 2-mm-thick increment of a flowable composite (Filtek Flow) was used in the proximal box in 50% of the restorations of each adhesive. Preparations were restored with a packable composite (Surefil). The restorations were evaluated preoperatively and 2 weeks postoperatively for sensitivity to cold, air, and masticatory forces using a visual analog scale. Marginal integrity of the accessible margins was also evaluated. Statistical analysis used a mixed linear model with subject as a random effect. Results: Ninety-eight teeth from 44 subjects were observed at 2 weeks. The type of adhesive and use of flowable composite had no significant effects or interaction for any of the four outcomes of interest, ie, change from baseline to 2 weeks in sensitivity and response time for the cold or air stimulus. For the air stimulus, the overall average change from baseline was not significant for either sensitivity or response time. For the cold stimulus, the overall average change from baseline was significant for both sensitivity and response time. No case of sensitivity to masticatory forces was observed. Conclusion: No differences in postoperative sensitivity were observed between a self-etch adhesive and a total-etch adhesive at 2 weeks. The use of flowable composite did not decrease postoperative sensitivity.

Piezoelectric composite film for acoustic emission detection

The continuous technological advances require materials with properties that conventional material cannot display. Material property combinations are being the focus to the development of composite materials, which are considered a multiphase material that exhibits properties of the constituent phases. One interesting material to be studied as sensing material is the composite made of ferroelectric ceramic and polymeric matrix as a two-phases composite material. In that case, the combinations properties intended are the high piezo and pyroelectric activities of the dense ceramic with the impact resistance, flexibility, formability and low densities of the polymer. Using the piezoelectric property of the composite film, it can be used to detect acoustic emission (AE), which is a transient elastic wave generated by sudden deformation in materials under stress. AE can be applied for evaluating the health of structures in a nondestructive way and without any lapse of time. The preliminary result indicates that the composite Pz34/PEEK can be used as sensing material for nondestructive evaluation. ©2009 IEEE.

Comportamento mecânico de material compósito de matriz poliéster reforçado por sistema híbrido fibras naturais e resíduos da indústria madeireira

Neste trabalho, materiais compósitos de matriz poliéster reforçados por fibras curtas de sisal, por resíduo de madeira e por sistema híbrido sisal/resíduo de madeira, dispostos aleatoriamente foram produzidos, utilizando-se o menor nível possível de processamento tecnológico nas etapas produtivas, com vistas a se produzir um compósito tecnicamente viável a pequenos produtores. A matriz de poliéster utilizada foi a tereftálica pré-acelerada com naftenato de cobalto e curada a temperatura ambiente com peróxido de metil-etil-cetona (MEK) em diferentes proporções em relação à resina, 0,33%, 1,66%, 3,33% e 5,00% em volume, de forma a se avaliar a influência deste nas propriedades mecânicas. As fibras de sisal foram cortadas manualmente nos comprimentos de 5, 10 e 15mm e utilizadas da maneira como adquiridas, sem tratamento superficial. O resíduo de madeira utilizado foi o pó de lixadeira da madeira maçaranduba. Os compósitos foram fabricados por moldagem manual, sem pressão e a temperatura ambiente. Foram fabricados corpos de prova de matriz pura, compósitos reforçados por sisal, variando-se o comprimento das fibras, compósitos reforçados por pó de maçaranduba e compósitos de reforço híbrido, sisal/pó de madeira, em diferentes proporções entre os constituintes. As propriedades mecânicas foram avaliadas por ensaios de tração e impacto charpy e as superfícies de fratura geradas foram avaliadas por microscopia eletrônica de varredura de modo a se correlacionar os aspectos de fratura com as propriedades mecânicas. Foi determinada a massa específica de cada série de corpos de prova fabricada, bem como a fração volumétrica dos reforços nos compósitos. Os resultados demonstraram que com o aumento do comprimento da fibra de sisal a resistência à tração e ao impacto dos compósitos foi incrementada, alcançando, o compósito com fibras de sisal de 15 mm, o melhor desempenho mecânico dentre as séries testadas. Por outro lado, a heterogeneidade granulométrica do pó de maçaranduba teve efeito negativo sobre as propriedades mecânicas dos compósitos. Os compósitos híbridos sisal/pó de madeira com maior teor de fibras, alcançaram 80% do desempenho obtido para os compósitos de fibras de sisal.

Fabricação e caracterização de material compósito de resina poliéster reforçada por tecido de fibra de tururi extraído da palmeira de ubuçu (Manicaria saccifera)

Neste trabalho é apresentada a fabricação e caracterização de um material compósito de matriz polimérica reforçada por fibras naturais. A matriz é um poliéster teraftélica insaturada préacelerada obtida comercialmente como Denverpoly 754 e o agente de cura utilizado foi o peróxido de Mek (Butanox M- 50), na proporção de 0,33 % , em volume. A fibra natural usada foi o tururi, obtida da região do Marajó, município de Muaná. O tecido de fibra de tururi foi submetido a dois tipos de abertura no sentido transversal, de [50 e 100]%, em relação a uma largura original. A fabricação do material compósito foi através do método da laminação manual (hand lay up), seguido de uma pressão controlada através de pesos previamente quantificados. Características físicas, mecânicas e microscópicas foram obtidas para a fibra e o material compósito, obtendo-se resistência a tração, massa específica, gramatura do tecido, fração mássica e imagens microscópicas antes e depois do ensaio de tração para o tecido da fibra e ensaio de tração depois do ensaio de tração para o material compósito. O tecido de tururi apresentou resistência a tração de 29,95 MPa (sem abertura), 12,27 MPa (abertura de 50 %) e 9,38 MPa (abertura de 100 %). A abertura provoca a diminuição da resistência à tração do tecido de tururi. A gramatura do tecido diminuiu com a abertura do tecido. A fração mássica do tecido do compósito foi de 14,39 % (sem abertura), 9,35 % (abertura de 50 %) e 7,19 % (abertura de 100 %). A resistência a tração do compósito foi de 35,76 MPa (sem abertura), 19,01 MPa (50 % de abertura) e 16,8 MPa (100 % de abertura). A resistência mecânica apresentou valores aproximados aos encontrados na literatura para materiais compósitos reforçados por fibras naturais. As imagens obtidas em microscopia eletrônica de varredura corroboraram com as propriedades mecânicas obtidas para cada situação do material e fibras.

Adhesive bonding of resin composite to various titanium surfaces using diferente metal conditioners and a surface modification system

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

An innovative material based on natural rubber and leather tannery waste to be applied as antistatic flooring

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

Bamboo as sustainable material used in design and civil construction: species, management, characterization and applications

The use of bamboo as construction and raw material for producing products can be considered a feasible alternative to the abusive use of steel, concrete and oil byproducts. Its use can also reduce the pressure on the use of wood from native and planted forests. Although there are thousands of bamboo species spread about the world and Brazil itself has hundreds of native species, the use and basic knowledge of its characteristics and applications are still little known and little disseminated. This paper's main objective is to introduce the species, the management phases, the physical and mechanical characteristics and the experiences in using bamboo in design and civil construction as per the Bamboo Project implemented at UNESP, Bauru campus since 1994. The results are divided into: a) Field activities - description of the technological species of interest, production chain flows, types of preservative treatments and clump management practices for the development, adaptation and production of different species of culms; b) Lab experiments - physical and mechanical characterization of culms processed as laminated strips and as composite material (glue laminated bamboo – glubam); c) Uses in projects - experiences with natural bamboo and glubam in design, architecture and civil construction projects. In the final remarks, the study aims to demonstrate, through practical and laboratory results, the material's multi-functionality and the feasibility in using bamboo as a sustainable material.

Theoretical models to predict the mechanical behavior of thick composite tubes

This paper shows theoretical models (analytical formulations) to predict the mechanical behavior of thick composite tubes and how some parameters can influence this behavior. Thus, firstly, it was developed the analytical formulations for a pressurized tube made of composite material with a single thick ply and only one lamination angle. For this case, the stress distribution and the displacement fields are investigated as function of different lamination angles and reinforcement volume fractions. The results obtained by the theoretical model are physic consistent and coherent with the literature information. After that, the previous formulations are extended in order to predict the mechanical behavior of a thick laminated tube. Both analytical formulations are implemented as a computational tool via Matlab code. The results obtained by the computational tool are compared to the finite element analyses, and the stress distribution is considered coherent. Moreover, the engineering computational tool is used to perform failure analysis, using different types of failure criteria, which identifies the damaged ply and the mode of failure.

Influence of beveling and ultrasound application on marginal adaptation of box-only Class II (slot) resin composite restorations

A laboratory study was performed to assess the influence of beveling the margins of cavities and the effects on marginal adaptation of the application of ultrasound during setting and initial light curing. After minimal access cavities had been prepared with an 80 microm diamond bur, 80 box-only Class II cavities were prepared mesially and distally in 40 extracted human molars using four different oscillating diamond coated instruments: (A) a U-shaped PCS insert as the non-beveled control (EMS), (B) Bevelshape (Intensiv), (C) SonicSys (KaVo) and (D) SuperPrep (KaVo). In groups B-D, the time taken for additional bevel finishing was measured. The cavities were filled with a hybrid composite material in three increments. Ultrasound was also applied to one cavity per tooth before and during initial light curing (10 seconds). The specimens were subjected to thermomechanical stress in a computer-controlled masticator device. Marginal quality was assessed by scanning electron microscopy and the results were compared statistically. The additional time required for finishing was B > D > C (p < or = 0.05). In all groups, thermomechanical loading resulted in a decrease in marginal quality. Beveling resulted in higher values for "continuous" margins compared with that of the unbeveled controls. The latter showed better marginal quality at the axial walls when ultrasound was used. Beveling seems essential for good marginal adaptation but requires more preparation time. The use of ultrasonic vibrations may improve the marginal quality of unbeveled fillings and warrants further investigation.

[The stamp technique for direct composite restoration]

The indications for direct resin composite restorations are nowadays extended due to the development of modern resin materials with improved material properties. However, there are still some difficulties regarding handling of resin composite material, especially in large restorations. The reconstruction of a functional and individual occlusion is difficult to achieve with direct application techniques. The aim of the present publication was to introduce a new "stamp"-technique for placing large composite restorations. The procedure of this "stamp"-technique is presented by three typical indications: large single-tooth restoration, occlusal rehabilitation of a compromised occlusal surface due to erosions and direct fibre-reinforced fixed partial denture. A step-by-step description of the technique and clinical figures illustrates the method. Large single-tooth restorations can be built-up with individual, two- piece silicone stamps. Large occlusal abrasive and/or erosive defects can be restored by copying the wax-up from the dental technician using the "stamp"-technique. Even fiber-reinforced resin-bonded fixed partial dentures can be formed with this intraoral technique with more precision and within a shorter treatment time. The presented "stamp"-technique facilitates the placement of large restoration with composite and can be recommended for the clinical use.

Mode II fracture energy in the adhesive bonding of dissimilar substrates: carbon fibre composite to aluminium joints

The end-notched flexure (ENF) test calculates the value of mode II fracture energy in adhesive bonding between the substrates of same nature. Traditional methods of calculating fracture energy in the ENF test are not suitable in cases where the thickness of the adhesive is non-negligible compared with adherent thicknesses. To address this issue, a specific methodology for calculating mode II fracture energy has been proposed in this paper. To illustrate the applicability of the proposed method, the fracture energy was calculated by the ENF test for adhesive bonds between aluminium and a composite material, which considered two different types of adhesive (epoxy and polyurethane) and various surface treatments. The proposed calculation model provides higher values of fracture energy than those obtained from the simplified models that consider the adhesive thickness to be zero, supporting the conclusion that the calculation of mode II fracture energy for adhesives with non-negligible thickness relative to their adherents should be based on mathematical models, such as the method proposed in this paper, that incorporate the influence of this thickness.

Polyolefin fibre-reinforced concrete : from material behaviour to numerical and design considerations

La presente Tesis proporciona una gran cantidad de información con respecto al uso de un nuevo y avanzado material polimérico (con base de poliolefina) especialmente adecuada para ser usada en forma de fibras como adición en el hormigón. Se han empleado fibras de aproximadamente 1 mm de diámetro, longitudes entre 48 y 60 mm y una superficie corrugada. Las prometedoras propiedades de este material (baja densidad, bajo coste, buen comportamiento resistente y gran estabilidad química) justifican el interés en desarrollar el esfuerzo de investigación requerido para demostrar las ventajas de su uso en aplicaciones prácticas. La mayor parte de la investigación se ha realizado usando hormigón autocompactante como matriz, ya que este material es óptimo para el relleno de los encofrados del hormigón, aunque también se ha empleado hormigón normal vibrado con el fin de comparar algunas propiedades. Además, el importante desarrollo del hormigón reforzado con fibras en los últimos años, tanto en investigación como en aplicaciones prácticas, también es muestra del gran interés que los resultados y consideraciones de diseño que esta Tesis pueden tener. El material compuesto resultante, Hormigón Reforzado con Fibras de Poliolefina (HRFP o PFRC por sus siglas inglesas) ha sido exhaustivamente ensayado y estudiado en muchos aspectos. Los resultados permiten establecer cómo conseguidos los objetivos buscados: -Se han cuantificado las propiedades mecánicas del PFRC con el fin de demostrar su buen comportamiento en la fase fisurada de elementos estructurales sometidos a tensiones de tracción. -Contrastar los resultados obtenidos con las bases propuestas en la normativa existente y evaluar las posibilidades para el uso del PFRC con fin estructural para sustituir el armado tradicional con barras de acero corrugado para determinadas aplicaciones. -Se han desarrollado herramientas de cálculo con el fin de evaluar la capacidad del PFRC para sustituir al hormigón armado con las barras habituales de acero. -En base a la gran cantidad de ensayos experimentales y a alguna aplicación real en la construcción, se han podido establecer recomendaciones y consejos de diseño para que elementos de este material puedan ser proyectados y construidos con total fiabilidad. Se presentan, además, resultados prometedores en una nueva línea de trabajo en el campo del hormigón reforzado con fibras combinando dos tipologías de fibras. Se combinaron fibras de poliolefina con fibras de acero como refuerzo del mismo hormigón autocompactante detectándose sinergias que podrían ser la base del uso futuro de esta tecnología de hormigón. This thesis provides a significant amount of information on the use of a new advanced polymer (polyolefin-based) especially suitable in the form of fibres to be added to concrete. At the time of writing, there is a noteworthy lack of research and knowledge about use as a randomly distributed element to reinforce concrete. Fibres with an approximate 1 mm diameter, length of 48-60 mm, an embossed surface and improved mechanical properties are employed. The promising properties of the polyolefin material (low density, inexpensive, and with good strength behaviour and high chemical stability) justify the research effort involved and demonstrate the advantages for practical purposes. While most of the research has used self-compacting concrete, given that this type of matrix material is optimum in filling the concrete formwork, for comparison purposes standard vibration compacted mixes have also been used. In addition, the interest in fibre-reinforced concrete technology, in both research and application, support the significant interest in the results and considerations provided by the thesis. The resulting composite material, polyolefin fibre reinforced concrete (PFRC) has been extensively tested and studied. The results have allowed the following objectives to be met: -Assessment of the mechanical properties of PFRC in order to demonstrate the good performance in the post-cracking strength for structural elements subjected to tensile stresses. -- Assessment of the results in contrast with the existing structural codes, regulations and test methods. The evaluation of the potential of PFRC to meet the requirements and replace traditional steel-bar reinforcement applications. -Development of numerical tools designed to evaluate the capability of PFRC to substitute, either partially or totally, standard steel reinforcing bars either alone or in conjunction with steel fibres. -Provision, based on the large amount of experimental work and real applications, of a series of guidelines and recommendations for the practical and reliable design and use of PFRC. Furthermore, the thesis also reports promising results about an innovative line in the field of fibre-reinforced concrete: the design of a fibre cocktail to reinforce the concrete by using two types of fibres simultaneously. Polyolefin fibres were combined with steel fibres in self-compacting concrete, identifying synergies that could serve as the base in the future use of fibre-reinforced concrete technology.

In vivo biocompatibility evaluation of composite polymeric materials for use in a novel artificial heart valve

A novel trileaflet polymer valve is a composite design of a biostable polymer poly(styrene-isobutylene-styrene) (SIBS) with a reinforcement polyethylene terephthalate (PET) fabric. Surface roughness and hydrophilicity vary with fabrication methods and influence leaflet biocompatibility. The purpose of this study was to investigate the biocompatibility of this composite material using both small animal (nonfunctional mode) and large animal (functional mode) models. Composite samples were manufactured using dip coating and solvent casting with different coating thickness (251μm and 50μm). Sample's surface was characterized through qualitative SEM observation and quantitative surface roughness analysis. A novel rat abdominal aorta model was developed to test the composite samples in a similar pulsatile flow condition as its intended use. The sample's tissue response was characterized by histological examination. Among the samples tested, the 25μm solvent-cast sample exhibited the smoothest surface and best biocompatibility in terms of tissue capsulation thickness, and was chosen as the method for fabrication of the SIBS valve. Phosphocholine was used to create a hydrophilic surface on selected composite samples, which resulted in improved blood compatibility. Four SIBS valves (two with phosphocholine modification) were implanted into sheep. Echocardiography, blood chemistry, and system pathology were conducted to evaluate the valve's performance and biocompatibility. No adverse response was identified following implantation. The average survival time was 76 days, and one sheep with the phosphocholine modified valve passed the FDA minimum requirement of 140 days with approximately 20 million cycles of valve activity. The explanted valves were observed under the aid of a dissection microscope, and evaluated via histology, SEM and X-ray. Surface cracks and calcified tissue deposition were found on the leaflets. In conclusion, we demonstrated the applicability of using a new rat abdominal aorta model for biocompatibility assessment of polymeric materials. A smooth and complete coating surface is essential for the biocompatibility of PET/SIBS composite, and surface modification using phosphocholine improves blood compatibility. Extrinsic calcification was identified on the leaflets and was associated with regions of surface cracks.

Improved electrochemical performance of Sr2Fe1.5Mo0.4Nb0.1O6-δ -Sm0.2Ce0.8O2-δ composite cathodes by a one-pot method for intermediate temperature solid oxide fuel cells

In this paper, Sr₂Fe_1.5Mo_0.4Nb_0.1O_6-δ (SFMNb)-xSm_0.2Ce_0.8O_2-δ (SDC) (x = 0, 20, 30, 40, 50 wt%) composite cathode materials were synthesized by a one-pot combustion method to improve the electrochemical performance of SFMNb cathode for intermediate temperature solid oxide fuel cells (IT-SOFCs). The fabrication of composite cathodes by adding SDC to SFMNb is conducive to providing extended electrochemical reaction zones for oxygen reduction reactions (ORR). X-ray diffraction (XRD) demonstrates that SFMNb is chemically compatible with SDC electrolytes at temperature up to 1100 °C. Scanning electron microscope (SEM) indicates that the SFMNb-SDC composite cathodes have a porous network nanostructure as well as the single phase SFMNb. The conductivity and thermal expansion coefficient of the composite cathodes decrease with the increased content of SDC, while the electrochemical impedance spectra (EIS) exhibits that SFMNb-40SDC composite cathode has optimal electrochemical performance with low polarization resistance (R_p) on the La_0.9Sr_0.1Ga_0.8Mg_0.2O₃ electrolyte. The R_p of the SFMNb-40SDC composite cathode is about 0.047 Ω cm² at 800 °C in air. A single cell with SFMNb-40SDC cathode also displays favorable discharge performance, whose maximum power density is 1.22 W cm^-2 at 800 °C. All results indicate that SFMNb-40SDC composite material is a promising cathode candidate for IT-SOFCs.