Background: Poly-ether-ether-ketone(PEEK) has been introduced to many dental fields. Recently it was tested as a retainer wire‎ following orthodontic treatment. This study aimed to investigate the effect of changing the bonding spot size and location on the performance of PEEK retainer wires. Methods: A biomechanical study involving four three-dimensional finite element models was performed. The basic model was with a 0.8 mm cylindrical cross-section PEEK wire, bonded at the center of the lingual surface of the mandibular incisors with 4 mm in diameter composite spots. Two other models were designed with 3 mm and 5 mm composite sizes. The last model was created with the composite bonding spot of the canine away from the center of the crown, closer to the lateral incisor. The linear displacement of the teeth, strains of the periodontal ligament, and stresses in PEEK wire and composite were evaluated. The data was numerically produced with color coded display by the software. Selected values were tabulated and compared among models. Results: The amount of linear displacement and strain was very low. Stresses in the wire and composite were affected by the size and position of the composite bonding spot. The safe limits were identified at 235 MPa for PEEK and 100 MPa for composite. The basic model had a von Mises stress in the PEEK wire of 122.09 MPa, and a maximum principal stress in the composite of 99.779 MPa. Both stresses were within the safe limits, which means a lower risk of failure in PEEK and composite. All other models had stresses that exceeded the safe limit of the composite. The 3 mm composite model was the only one that developed stresses in the wire more than the safe limits of PEEK. Conclusions: Within the limitations of this study, bonding PEEK wires with 4 mm bonding spots to the clinical crown center provided the best mechanical performance of the wires and spots; otherwise, the mechanical properties of the wire and composite would be affected and, therefore, might affect the retention process. Keywords: Retention, PEEK, Finite element analysis
The design processes in general and the design system in particular need to be studied and knowledge. Based on this vision, we find the need for constant research on the design processes, and the subject of the techniques of the designs of the covers of children magazines did not have the view of the researchers to make them the subject of study, For the subject of this research, the problem of research is determined according to the following question:
- What are the methods used in designing children magazine covers in Iraq?
Through this research we seek to find solutions to this question as well as it will serve the cognitive side of a modern study and development of a broader understanding of the subject. Through four
... Show MoreThe monitoring weld quality is increasingly important because great financial savings are possible because of it, and this especially happens in manufacturing where defective welds lead to losses in production and necessitate time consuming and expensive repair. This research deals with the monitoring and controllability of the fusion arc welding process using Artificial Neural Network (ANN) model. The effect of weld parameters on the weld quality was studied by implementing the experimental results obtained from welding a non-Galvanized steel plate ASTM BN 1323 of 6 mm thickness in different weld parameters (current, voltage, and travel speed) monitored by electronic systems that are followed by destructive (Tensile and Bending) and non
... Show MoreThis study deals with Aphid predators of the genus Coccinella L. recognized in different
regions of the world. They have been arranged systematically according to Korschefsky’s
catalogue (1931). The list includes sites of study and the reference (works) that consider
Coccinellids as predator. The study has revealed that there are thirteen Aphid predator species
belonging to the genus Coccinella L. in different places of the world, although there might be
other species that were not recorded by this work.
Abstract: The term extremism refers to the distance from moderation, excess and hyperbole, and it is a relative term that varies from one society to another, according to the prevailing traditions, values and culture, as the problem of extremism is one of the main issues that contemporary societies are concerned with is a phenomenon that has its roots in the intellectual formation of societies. By knowing the concept of extremism, we can identify the reasons that contributed to the existence of extremism as a phenomenon, on the one hand; on the other hand, to clarify the role of women in combating extremism and developing effective solutions to reduce this phenomenon. As women play a major role in society, starting from the family to educa
... Show MoreABSTRACT Studying the positive and negative effects resulted from the industrial projects and laying down the comprehensive planning bases to the urban development projects which insure retaining the social, economic and environmental development, taking in to consternation the time factor within the planning process which is considered the most important factor that determine the extent of the efficient selection to the site and not interpenetrate in the industrial activities and efficiency and calculating its future expansions away from the residential areas. It is more favorable to plan the industrial areas of apparent pollution outside the bounds of the basic plan to limit the negative effects on the environment and providing
... Show Moreفي بداية الستينيات ظهرت شبكة الإنترنت لاستعمالها في أغراض غير تجارية ، ثم تطورت بشكل مذهل خلال السنوات الأخيرة، فبعد أن كانت مجرد شبكة صغيرة أصبحت الآن تضم ملايين المستخدمين حول العالم ، وتحولت من مجرد شبكة بحث أكاديمي إلى بيئة متكاملة للاستثمار والعمل والإنتاج والإعلام والحصول على المعلومات .
وفي بداية تأسيس الشبكة لم يكن ثمة اهتمام بمسائل الأمن بقدر ما كان الاهتمام ببنائها وتوسيع نش
... Show MoreThis work aims to introduce the concepts of left and right derivations in an AT-algebra and discuss some interesting theorems of these concepts. Also, a fuzzy derivation of an AT-subalgebra, a fuzzy right (left) derivation ideal, a fuzzy derivation of AT-subalgebra, and a fuzzy right (left) derivation ideal are studied. Finally, a level derivation of AT-algebras is defined and some propositions are achieved.
The arts global digital marketing activity is one of the most prominent manifestations of the contemporary transformation in the circulation of cultural products, and that this event has become a new knowledge event that deserves to be a framework for the problem of our current research, while this phenomenon is growing and developing to compete with the traditional marketing of art through galleries, exhibitions, auctions and museums. It is still the preserve of certain civilized and knowledge environments, and from here this research comes with the aim of shedding light on the mechanisms of digitizing the contemporary art market that have been linked to the two variables of the growing idea of indirect marketing through the intermediar
... Show MoreThis research aims to investigate the approaches adopted by Iraqi newspapers in addressing the COVID-19 pandemic crisis. Employing a descriptive methodology and survey technique, the study conducts content analysis on articles published in three prominent newspapers: Al-Sabah, Al-Mada, and Tareeq Al-Shaab. A multi-stage sampling method was employed, encompassing 260 issues of the aforementioned newspapers. Data collection involved the use of a content analysis questionnaire, with the "How it was said?" method utilized to determine analysis categories.
The results showed that Al-Sabah newspaper adopted a positive approach in addressing COVID-19-related topics, while Al-Mada newspaper remained neutral, and Tare