Background and Aims: When composite resin polymerizes, shrinkage stresses tend to produce gaps at the tooth/ restoration interfaces. Surface sealants may reduce or avoid problems related to the marginal interface. The aim of this study was to evaluate the effect of two different surface sealants (Fortify and Optiguard) on the microleakage of class V resin composite restorations.Materials and Methods: Twenty three sound noncarious molars were collected. Totally, 45 Class V cavities with the occlusal margins in enamel and cervical margins in cementum were prepared in both buccal and lingual surfaces. The specimens were randomly assigned in three groups (15 cavities in each group) and then restored with a resin composite. After the finishing and polishing procedures, the restorations in each group were covered with a specific surface sealant, except for the control samples, which were not sealed. After placing restorations, the specimens were thermocycled and then immersed in a 50% silver nitrate solution (tracer agent) for four hours, sectioned longitudinally and analyzed for leakage using a stereomicroscope in a blind manner. The marginal microleakage was evaluated at the occlusal and cervical interfaces and compared among the three groups using the Kruskall-Wallis and the Mann-Whitney U tests.Results: Microleakage was found in all groups at both occlusal and cervical margins. Significantly greater leakage was observed at the cervical margins compared to the enamel margins of the material groups (P=0.005).There was no statistically significant difference among the groups at occlusal margins (P=0.66). In the cervical region, Fortify showed improved results and statistically presented the lowest degree of microleakage (P=0.003).Conclusion: The used sealant materials presented different rates of effectiveness and Fortify decreased marginal microleakage significantly.

In this study, the effects of the surface condition of rebar on its capacitance are investigated. Five rebars with different surface conditions were prepared. The results of ac-impedance experiments on these rebars in saturated calcium hydroxide solution were fitted into an equivalent circuit program. Parameters such as n and Y0 for Constant Phase Element (CPE), dependent on surface condition, were determined. The frequency dependence of impedance was also compared for rebars with different surface conditions.

In this paper, by applying the non-classical symmetry method, nonclassical symmetries of the Kodryashov-Sinleschikov (K-S) and modified Korteweg-de Vries-Zaharov-Kuznetsov (mKdV-ZK) equations are obtained. Apart from classical symmetries, this theory can be effective in finding a few other solutions for a system of PDEs and ODEs. Also, non-classical symmetries of a system of PDEs can be applied to reduce the number of independent variables. By adding the invariance surface condition to the assumed equations and applying the classical symmetry method for them, non-classical symmetries are calculated. Finally, some of the group invariant solutions and the similarity reduced equations associated to non-classical symmetry are obtained.

In this paper, the aim is to find the nearest trapezoidal fuzzy number to a given fuzzy number which preserves the convex combination of support and core intervals of that fuzzy number. This allows the decision maker to select the preferred approximation of a fuzzy number from a class of trapezoidal approximations. Nowadays, the fuzzy concepts are widely used in many real-world engineering applications, such as population models, control chaotic systems, economics and finance, artificial intelligence, computer science, expert systems, management science, operations research, pattern recognition, robotics and others. Because of the existence of fuzzy parameters, computational complexity is the cost of fuzzy system and this matter has captured the attention of researchers for introducing methods and decreasing this cost. In general, most of the fuzzy-based algorithms use a defuzzification process that maps a fuzzy parameter into a crisp one. Obviously, in most cases, too much important information is lost by converting fuzzy sets into a set of real numbers. It seems that we should accept some criteria and apply a framework for constructing a defuzzyfication process. Van Leekwijck et al. in [21] presented a set of criteria for defuzzification strategies and classified the most widely used defuzzification techniques into different groups and they examined the prototypes of each group with respect to the defuzzification criteria.