Introduction: Considering the importance of microleakage in posterior composite restorations for recurrent caries and pulpitis in formerly repaired teeth, this study aimed to evaluate and compare the microleakage rate of class II composite restorations in two methods: Open sandwich and Snowplow. Materials and Methods: In this study, a total of 64 premolar teeth with a class II cavity whose margins were extended 1 mm below dentin and cement joint were prepared and divided into two groups. In the first group, a layer of 1 mm thick resinmodified glass ionomer (RMGI Fuji II LC) was placed on the gingival floor and cured. The cavity was then etched with phosphoric acid gel, washed, and a bonding agent was applied. Then resin composite (Z250 3M ESPE) was incrementally applied in the cavities. In the second group, the cavity preparation was performed in the same way as that in group A. Afterward, 1 mm thick flowable composite (Filtek Z350 3M) was placed on the gingival floor, without curing. A layer of 1 mm thick resin composite was then added and packed. Both layers were then cured at once. The prepared teeth underwent 3000 times thermocycling and were placed in methylene blue for 72 h for evaluation of microleakage rate. The teeth were then cut mesiodistally. The samples of both groups were examined under a stereomicroscope, and the mean microleakage in both groups was compared using the Mann-Whitney test. Results: In the first group, based on the degree of dye penetration, the average amount of microleakage was observed in 10. 66% of the samples. In the second group, the average amount of microleakage was 5. 25%, using the Snowplow technique. Moreover, in the Open sandwich technique, dye penetration level in 34. 4%, 12. 5%, 34. 4%, and 18. 8% of samples was zero, one, two, and three, respectively. Moreover, in the Snowplow group, dye penetration level in 46. 9%, 25%, 25%, and 3. 1% of samples was zero, one, two, and three, respectively. The level of significance was set at 0. 05. Conclusion: Based on the obtained results, Snowplow and Open sandwich techniques are not effective for complete elimination of the microleakage of posterior composite restorations. The rate of microleakage in tooth restoration interface in class II restorations using the Snow-plow technique was more compared to the Open sandwich technique.

Introduction: Adaptation of posterior composites to dental walls has been questioned for various reasons and polymerization shrinkage is one example. Thus, the present study investigated microleakage ocurring from different class II composite restorations techniques. Materials & Methods: In this in-vitro study class II cavities with cervical margins 1 mm below the CEJ (Cementoenamel junction) were prepared in 64 extracted human premolars. The teeth were randomly divided into two groups. Group 1 (open sandwich): Glass ionomer was injected on the floor of the cavity and the rest of the cavity was restored using composite resin using incremental technique. Group 2 (Snowplow) one layer of flowable composite was placed in the bottom of the cavity and was co-cured with the first layer of composite resin. The rest of the cavity was restored the same as group 1. To evaluate the microleakage, the specimens were thermocycled for up to 3000 cycles and immersed in 1% methylene blue solution for 72 hours. Then they were sectioned mesiodistally and evaluated under a stereomicroscope. Data were analyzed via MannWhitney and Fishers exact test and p value < 0. 05 was considered significant. Results: The mean value for microleakage in group 1 (795. 74 ±,494. 04 mμ, ) was lower than group 2 (972. 99 ±,457. 8 mμ, ), but the results were not statistically significant (p value = 0. 117). Conclusion: It appears that microleakage in both open sandwich technique and Snowplow technique did not portray statistical significance, so both of them can be used.

The aim of this study was to determine the microleakage at the cervical margin of the class II composite resin syntac with and without a cervical amalgam base and to compare microleakage restoration at the occlusal margins of restorations and interface of amalgam and composite. 68 extracted sound permanent premolar were used. 68 class II slot cavities were prepared in these teeth. The teeth were randomly divided into four groups, and restored as follows; Group A: Amalgam (Cinalux) + Syntac (bonding agent) + composite (Tetric) (sandwich technique) Group B: Amalgam (Luxalloy) + syntac +composite (tetric) (Sandwich technique). Group C: Syntac + composite (Control 1). Group D: Amalgam (Cinalux) (Control 2). Then the teeth were thermocycled, and immersed in the fuchsion. Marginal leakage was assessed by the degree of dye penetration on sections of the restored teeth, under stereomicroscope at 7.5 maginification. For analysis of data non parametric statistic tests (Kruskal-wallis and Mann withney-u) were used. Although marginal leakage was not completely eliminated, Sandwich technique exhibited significantly less leakage at the cervical margins than conventional method (Syntac / Tetric composite) and also there was no significant difference between Cinallux and Luxalloy amalgams, at the cervical and occlusal margins.

Protective steel doors are widely used in buildings due to their high resistance against the impact loads. However, its heavy weight has been always considered as a major drawback for these doors. In this paper, a new optimized stiffened impact-protective steel door incorporating sandwich panel with aluminum foam core (OSSA) is examined. This door consists of two face sheets, main and secondary stiffeners, and aluminum foam as the inner core. In order to optimize the door, at first the rigidity and weight functions of the stiffened steel door were extracted. Then an optimal door weighing 42% less than the primary door was obtained. Due to the high energy absorption capacity of the combined foam core and stiffened steel door structure, the use of aluminum foam core in the optimized steel door was proposed. By doing numerical analysis, and depending on the thickness of the face sheet of OSSA, 20 to 32% reduction in the maximum displacement was observed. The results also showed that, with 67% increase in the peak overpressure, OSSA has kept almost the same maximum displacement as that of the steel door without an aluminum foam. In other words, by using aluminum foam core in the optimized stiffened door, the door will resist 67% more impact load.

After offering an overview of some of the main themes of Popper’s political thought, the paper argues that his account faces two problems relating to institutions. The first is that while Popper stresses the ‘rational unity of mankind’, and the potential for any of us to furnish criticisms of public policy, it is not clear what institutional means currently exist for this to enable this to take place. Second, Popper has stressed the conjectural character of even our best theories. However, at any point, some theories will have fared better in the face of criticism than others, and they may give us important information about constraints on our actions. At the same time, as ordinary citizens we may not be in a good position to understand the theories in question, let alone appraise the state of the specialised discussion of them. There is, it is suggested, a case for thinking of ways to institutionally entrench such fallible theories, especially in the current setting in which social media play an important role

In this paper, the response of simply supported flexible core sandwich beam with piezoelectric patch, under uniform harmonic loading with and without the control is analyzed. Sandwich beam is modeled using three-layer sandwich beam theory. Governing equations of motion are obtained using Hamilton’ s principle, based on Euler– Bernoulli beam theory for face-sheets and linear displacement field theory for soft core. By defining suitable state variables in time domain and using Galerkin’ s method, the state space equations of system are derived from governing equations of motion. Controller is designed using LQR technique. Dynamic response and frequency response of beam in open and closed loop configuration are obtained and the effect of flexible core on the control of dynamic response is investigated. The obtained results show that the controller can play an important role toward damping out the vibration of the sandwich beam. Also, it is shown that the %18 difference between vibration amplitudes of top and bottom face sheets, because of the flexibility of the core, affects the position of piezo actuator and sensor.

Introduction: Microleakage has always been a problem in restorative dentistry. To decrease microleakage, different restorative techniques and materials have been recommended. The purpose of this study was to evaluate micro leakage of the composite restoration in deciduous anterior teeth using the open sandwich technique by two different liners. Materials & Methods: This cross-sectional experimental study was conducted at Khorasgan University in 2019. A total of sixty intact deciduous canine teeth were divided into 3 groups of 20. At the buccal surface of the specimens, the Class V cavity was extracted at 1 mm below the CEJ (Cementoenamel junction) and in groups 1 and 2, ionoseal liner and Fuji II ionomer glass were placed at the buccal floor. Cavities were restored with Z250 composite resin. In group 3 which served as the control, restorations was perfromed without liners. All samples are prepared for establishment after dying in methylene blue 0. 5% solution. The buccal lingual incisions with a thickness of 1 mm were inspected under stereo microscope for micro leakage. A total of 5 samples were extracted from each group via random sampling to examine the marginal compliance under SEM (Scanning electron microscope). The intergroup comparisons were made using the chi-square and Kruskal-Wallis tests. Besides, intra-group comparisons were performed using the Mann-Whitney U test. All statistical procedures were performed at a significance level of less than 0. 05 (p value < 0. 05) using Gpower software. Results: The outcome of this study showed that microleakage of gingival margin in open sandwich techniques with ionoseal and Fuji II (group 1, 2) was significantly higher than in control group (p value = 0. 033). but in comparison between group 1, 2 there was no significant difference (p value = 0. 795). In SEM evaluation there was no significant difference in gingival microleakage (p value = 0. 232). Conclusion: Use of two liners: Ionoseal and Fuji II in Class V cavities restored by opensandwich technique in deciduce anterior teeth can reduce gingival microleakage.

One may say that The Open Society and Its Enemies (OS) offered in 1945 the first complete elaboration of the general approach proposed by Karl Popper, namely his ‘critical rationalism’, a bold generalization of the fallibilist falsificationism in the domain of the empirical sciences masterly proposed in Logik der Forschung (1934). The political content of The OS has been critically discussed. Nevertheless, not all people insist on the equally important moral dimension of the book, giving it its unity, I submit. Without morality, no critical discussion, no reason, no open society, let us say in a nutshell. I would argue that according to Popper, a strictly Christian morality of love would not be the appropriate emotional companion of critical rationalism, but that the less demanding moral emotion of sympathy or compassion is perhaps necessary to give it its force against violence. I give some support to this line of argument. In my view, Popper proposed a somewhat unarticulated critical rationalist ‘emotivism’ of sorts. The emotion of compassion is necessary for triggering our moral decisions and values, which are the ultimate basis of the choice for a reason against violence.