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This study investigated the antibacterial activity, bond strength to dentin (SBS), and ultra-morphology of the polymer–dentin interface of experimental adhesive systems doped with pyrogallol (PY), which is a ubiquitous phenolic moiety that is present in flavonoids and polyphenols. A universal adhesive containing 4-META and 10-MDP was used in this study. PY behaves as an antioxidant and anti-cancerogenic agent and it was incorporated into the adhesive at different concentrations (0.5 and 1 wt.%). The antibacterial activity and SBS were analyzed and the results were statistically analyzed. The ultra-morphology of the polymer–dentin interface was assessed using scanning electron microscopy (SEM). At 24 h, a lower antibacterial activity was observed for the control adhesive compared to those with 0.5% and 1% PY. No difference was seen in SBS between the three groups at 24 h. After 6 months, the SBS of the 0.5% PY adhesive was significantly lower than the other tested adhesives. The specimens created with 1% PY adhesive presented a higher bond strength at six months compared with that found at 24 h. No morphological differences were found at the polymer–dentin interfaces of the tested adhesives. Pyrogallol may be incorporated into modern universal adhesive systems to preserve the polymer–dentin bonding interface and confer a certain degree of antibacterial activity.

Polyurethane foam is widely used in such areas as the automotive industry and sport, and in the field of packaging because of its low stiffness, high compressibility and its ability to absorb strain energy. The quasi-static behaviours of polyurethane foam are highly nonlinear and elastic. This paper demonstrates that the nonlinear elastic mechanical behaviour of compressible polyurethane foam during the loading and unloading quasi-static compression tests can be described by applying Ogden's modified model. The experimental data from a uniaxial compression of three types of polyurethane foam in three different strain rates are used for parameter identification. A nonlinear optimization method helps to ensure that the parameters are satisfied with stability conditions. Thanks to the optimized parameter results, the numerical simulations agree with the experimental data. Finally, the errors between the model results and the experimental results are analyzed and the unloading phases are discussed in detail.

Flexible polyurethane foam is widely used in numerous applications such as seats and mattresses, due to its low stiffness and its ability to absorb deformation energy. The main objective of this article is to model the quasi-static mechanical behavior of three types of polyurethane foam in large deformation and to compare these three foams with three proposed models. The uniaxial compression/ decompression tests at three different strain rates were performed. The test results show that the three foams present different plateau stresses, maximum stresses, and abilities to absorb energy. Moreover, polyurethane foam also presents a nonlinear hyperelastic behavior and a viscoelastic behavior in large deformation. Three viscohyperelastic models which include a hyperelastic component and a memory component are proposed to model these behaviors. Model parameters were identified using the experimental data and a proper identification method. These models were validated on these three types of foam with the aim to present comparison results. The comparison results show that Ogden's viscoelastic model best agrees with the experimental results. POLYM. ENG. SCI., 55:1795SCI., 55: -1804SCI., 55: , 2015

. Quasi-static behavior identification of polyurethane foam using a memory integer model and the difference-forces method. Journal of Cellular Plastics, SAGE Publications, 2011, pp.447-465 ABSTRACT: Flexible polyurethane (PU) foam is widely used in numerous comfort applications such as automotive seat cushions and mattresses. It would be interesting to design a mechanical model which describes the behaviour of this material in a series of test conditions. The present study is devoted to the modelling of the quasi-static behaviour of polyurethane foam using a memory integer model. Polyurethane foam undergoing large compressive deformation exhibits highly nonlinear elasticity and a viscoelastic behaviour. The memory integer model describes the nonlinearity in a polynomial function and the viscoelasticity through a convolution function. Uni-axial compression tests help to identify the mechanical parameters of the model. The difference between the force responses of foam in load and unload phases constitute the base element of the method used in this paper. Numerous precautions are taken into account to obtain accurate results which verify the thermodynamic conditions. Finally, the reliability as well as the limits of the memory integer model are discussed.

The aim of the present in vitro study was to evaluate specific mechanical and physicochemical properties of two calcium silicate based sealers, (AH Plus Bioceramic “AHPB”; Well-Root ST “WRST”), and a conventional resin sealer (AH Plus “AHP”). These aims were accomplished by assessing the porosity, pH, compression strength, roughness, wettability and cell attachment of the tested materials. The results were compared statistically using the one-way ANOVA test. Higher pH values were obtained in both AHPB and WRST compared to AHP at 3, 24 and 72 h (p < 0.05). A greater level of porosity and wettability was detected for both AHPB and WRST compared to the resin sealer AHP (p < 0.05). Evident cell growth characterized by elongated morphology was observed on the surface of AHPB and WRST, while only a thin layer of cells was seen on the surface of AHP. A significant lower compression strength and modulus were obtained in the specimens created using AHPB compared to those made with AHP and WRST (p < 0.05). The removal of calcium silicates may be quite tricky during endodontic retreatment. In conclusion, considering the limitations of the present in vitro study, both calcium silicate sealers demonstrated good physicochemical properties. However, the lower compression strength and modulus of AHPB may facilitate its removal and make the retreatment procedures considerably easier.

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