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    MICROLEAKAGE OF ENDODONTICALLY TREATED TEETH RESTORED WITH 3 DIFFERENT ADHESIVE SYSTEMS AND 4 DIFFERENT FIBER-REINFORCED POSTS
    (Mosby-Elsevier, 2012) Basaran, Emine Goncu; Ayna, Emrah; Halifeoglu, Meral
    Statement of problem. Despite recent advances in adhesive dentistry, fiber-reinforced post/resin cement/dentin adhesive combinations are not able to prevent microleakage. While studies have examined microleakage in endodontically treated teeth restored with posts and cores, microleakage among post and adhesive systems remains a concern. Purpose. This study compared the sealing properties of 4 adhesively luted post systems: glass fiber, quartz-glass fiber, zirconia-glass fiber and polyethylene fiber posts. Material and methods. Forty-eight permanent maxillary central incisors were divided into 4 groups (n=12). Post space was prepared and each post was adhesively luted with 1 of 3 systems: a 1-stage self-etch, a 2-stage total-etch, and a 3-stage total-etch adhesive. The specimens were separately immersed in freshly prepared 2% methylene blue solution for 1 week. The cleaned specimens were then embedded in autopolymerizing acrylic resin. The teeth were horizontally sectioned into apical, middle, and coronal portions. An occlusal view of each section was digitally photographed with a stereomicroscope. The methylene blue-infiltrated surface for each specimen was measured and data were collected with software. Dye penetration was estimated as the ratio of the methylene blue-infiltrated surface to the total dentin surface. Nonparametric data were analyzed with the Kruskal-Wallis test (alpha=.05). The Mann-Whitney U-test was used to compute multiple pairwise comparisons that identified differences among groups. Dentin-luting agent and post interfaces were evaluated with a scanning electron microscope. Results. Significant differences in adhesive and post systems were observed in all sectioned regions (P<.05). There were significant differences between the apical and coronal sections of each post type, and between the following pairs: middle versus coronal sections of zirconia-glass fiber and glass fiber posts and apical versus middle sections of quartz-glass fiber and polyethylene fiber posts (P<.05). No significant differences were found among post types. The variables of middle section and 3-stage adhesive produced significant differences in microleakage between the following post pairs: zirconia-glass fiber versus quartz-glass fiber, zirconia-glass fiber versus polyethylene fiber, and quartz-glass fiber versus polyethylene fiber (P<.05). Conclusions. The 3-stage adhesive and zirconia-glass fiber posts demonstrated the least microleakage. (J Prosthet Dent 2012;107:239-251)
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    Out-of-plane seismic failure assessment of spandrel walls in long-span masonry stone arch bridges using cohesive interface
    (Techno-Press, 2020) Bayraktar, Alemdar; Hokelekli, Emin; Halifeoglu, Meral; Halifeoglu, Zulfikar; Ashour, Ashraf
    The main structural elements of historical masonry arch bridges are arches, spandrel walls, piers and foundations. The most vulnerable structural elements of masonry arch bridges under transverse seismic loads, particularly in the case of out-of-plane actions, are spandrel wall. The vulnerability of spandrel walls under transverse loads increases with the increasing of their length and height. This paper computationally investigates the out-of-plane nonlinear seismic response of spandrel walls of long-span and high masonry stone arch bridges. The Malabadi Bridge with a main arch span of 40.86m and rise of 23.45m built in 1147 in Diyarbakir, Turkey, is selected as an example. The Concrete Damage Plasticity (CDP) material model adjusted to masonry structures, and cohesive interface interaction between the infill and the spandrel walls and the arch are considered in the 3D finite element model of the selected bridge. Firstly, mode shapes with and without cohesive interfaces are evaluated, and then out-of-plane seismic failure responses of the spandrel walls with and without the cohesive interfaces are determined and compared with respect to the displacements, strains and stresses.
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    Restoration and refunction problems of Diyarbakir traditional houses
    (Elsevier France-Editions Scientifiques Medicales Elsevier, 2013) Halifeoglu, Meral; Gokcay, Gokce
    The traditional urban texture of Diyarbakir is founded in the city walls. The traditional Diyarbakir houses have their own architectural properties, which are shaped with the effect of family structure, economical structure, cultural interaction, city walls, climate, geological structure and building materials. They also take an important place in the cultural heritage context due to their distinctive architectural characteristics. These independent houses that are isolated from the outside are located in a court. The traditional Diyarbakir houses, which are designed as summer, winter and spring places regarding to the effect of climatic factors, are generally formed of a basement, ground floor and the first floor. The basement is the area where the fuel (wood and coal) and foods for winter are stored. The service and living spaces are found at the ground and first floors. The wide entrances (ivans) and the rooms with their sliced, flat arched, quadrangular windows with columns are the building elements, which give movement and richness to the courtyard. While the walls built by basalt stones, the authentic flat roofs of the houses are covered by earthen materials. During the recent years, restoration works are conducted on monumental buildings and traditional houses in Diyarbakir by some state institutions and organizations, and, private enterprises, which enable them to be utilized in today's needs assessment. The most of the traditional houses offer a wide range of usage possibilities take an important place among them. The authentic textures of many of those houses have been destroyed due to the renovation works since 1960s. In these works, mostly additional floor and space constructions conducted by the owners. Deterioration and degeneration of the structures of the houses have increased because of the lack of proper control mechanism and incompetence of the technical staffs, working in this field. A few traditional houses have been restored to reuse with a new public functions by the Ministry of Culture and Tourism, governorship, municipality, non-governmental organizations and individuals. While restoring these houses, same of the wrong implementations have been damaged the authentic texture. As a result of the inspections that have been performed, it has been seen that the new function is directly related with the destruction that may occur. It is understood that the authentic values and cultural persistence are preserved when the functions not forced the original design, comfort level and construction techniques of the houses. Annexes, renovation and modifications destroy the authentic plan of the houses are limited in restoration works conducted by the Ministry and governorship; whereas, needs were taken into consideration during works performed by individuals and non-governmental organizations. Besides, the architectural building elements were also had renovation rather than conservation. (C) 2013 Elsevier Masson SAS. All rights reserved.