ABSTRACT Purpose: the aim of this in vitro study was to compare the marginal gap and internal fitness between single crowns and the crowns within three-unit bridges of zirconium fabricated by CAD-CAM system. Materials and methods: A standard model from ivoclar company was used as a pattern to simulate three-units bridge (upper first molar and upper first premolar) as abutments used to fabricate stone models, eight single crowns for premolar and eight of three units bridges. Crowns and bridges fabricated by CAD-CAM system were cemented on their respective stone models then sectioned at the mid-point buccolingaully and misiodistaly and examined under stereomicroscope. Result: the marginal gap in premolar crowns and premolar within bridge were within the acceptable value 120µm, one –way ANOVA showed that there was significant differences in the internal gaps among the areas. Independent t- Test showed there was significant differences between the premolar crowns and premolar crowns within bridges in marginal opening and cusp tip (lingually and distally) Conclusion: the marginal and internal gaps were in the bridge higher than those in the crowns. The areas of sloped surfaces such as chamfer area, occlusal area and cusp tip had high gap values in comparison with areas of flat surfaces such as axial wall and when the surface area of abutment increased, the marginal and internal gaps of abutment was increase.
Based on the streamer growth model, the streamer discharge propagation was simulated in aid of finite element technique. That was done within two non- mixed dielectric liquids (Normal-Hexane and Acetone) located between two electrodes in pin - plane configuration. The output results show that, the path of the streamer was affected by the interface between the two liquids; the streamer path crosses this interface under some conditions such as the permittivity of the liquids and the distance between this interface and the tip of the pin. Under other conditions, the streamer path grows along the interface. The results were assisted by the development of the potential and the electric field distributions with the growth of the streamer propa
... Show MoreSummary: The study focused on the role of the educational counselor in schools, as an integral part of the educational system that faces multiple challenges and difficulties. In this context, the counselor’s role becomes crucial in attempting to reduce or eliminate such difficulties, in addition to guiding students in an appropriate manner. Methodes: The study employed a descriptive field approach, using interviews and direct observation as tools to examine the actual role performed by school counselors. Results: The study concluded with several key findings, most notably the numerous challenges faced by counselors, including students’ negative behaviors, school dropouts, and the limited administrative support for counselors’ work. Fu
... Show MoreIn this paper, we studied the spark corona discharge in tap and distillited waters. The results show the shape of cone that generated on the tip of capillary tube is different with conductivity of liquids. The blue glow appears at the end of capillary tube and the drop extends into a cone. In addition, the conducitivity is affected on the relationship between the appearance of the blue glow discharge with the applied voltage. The size of the cone decreases with an increase in applied voltage. The cone diameter at the base of capillary tube oscillates with period approximately 1 Sec. this oscillates in the cone diameters is due to the change distance between the liquid electrode and the surface of liquid. The intensity of spark corona dis
... Show MoreThe aim of this research is to construct an educational program in light of the theory of behavioral cognitive and its impact on the development of the efficient response to students affected by crises (centers of your right to education). To achieve the objectives of the research, two scales were developed by the researcher in addition to two equivalent hypotheses were formulated. The scale contains (26) items divided into five fields; for its validity and reliability were derived based on the measure of efficient response, an educational program based on the theory of behavioral cognition. The test and the educational program were applied to a sample of (60) students from the centers of your right to education, divided into experimenta
... Show MoreHeat transfer performance of two horizontal parallel plates subjected to discrete heating from the upper plate is studied and analyzed under the condition of different gap size between the heating elements with water as the working fluid. The investigation includes the variation of Reynolds number and the heat flux along with the position of the heating elements to discover the effect of different boundary conditions on the gap size variation. Results show that gap size between the heating elements has a crucial impact on the heat transfer process inside the channel, when the gap size increased a remarkable enhancement is achieved. This result is also confirmed with the investigated range of Reynolds number and the heating value. Results al
... Show MoreCharacterized the Middle East has geographic, economic, and geostrategic peculiarities, but it suffers from many problems, such as disagreement over what it means as a concept, or what it represents of a geographic extension. The question is related to the ambiguity surrounding the concept of the Middle East? The purpose of its launch? As it relates to its geostrategic, economic, and geo-cultural importance? And manifestations of this importance? And to what extent he retained his value in the strategies of the major powers? Research hypotheses:
-The multiplicity of concepts for the Middle East region, with international political and Geostrategic interests.- The geostrategic value of the Middle East has made it a focal point for
... Show MoreThis research focuses on the contemporary geostrategic transformations that afflicted the countries of the Middle East, with a focus on the countries of the Arab East, after the collapse of the system of international relations, and the emergence of the unipolar system led by the United States of America. After the events of September 11 and the events that followed, especially the occupation of Iraq in 2003, the study area witnessed a group of geopolitical variables and the emergence of dangerous phenomena that threatened the state structure in the countries of the Middle East; the most notably are the phenomenon of terrorism, cross-border armed groups, sectarian polarization, the phenomenon of migration and the internal and the externa
... Show MoreCollapsible soil has a metastable structure that experiences a large reduction in volume or collapse when wetting. The characteristics of collapsible soil contribute to different problems for infrastructures constructed on its such as cracks and excessive settlement found in buildings, railways channels, bridges, and roads. This paper aims to provide an art review on collapse soil behavior all over the world, type of collapse soil, identification of collapse potential, and factors that affect collapsibility soil. As urban grow in several parts of the world, the collapsible soil will have more get to the water. As a result, there will be an increase in the number of wetting collapse problems, so it's very important to com
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