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
النشاطات العلمية لفرع الفكر السياسي
Elegy is one of the foundations of the Arab poetic heritage, and it is one of the main sections of poetry. Man has found in him his desire to express his innermost self at an hour filled with pain, and an outlet from which his anguish and grief come out in an expressive form that liberates tears and reproaches death.
Lamentation is an evolving purpose that grows with the growth of society and life and records the change that takes place in every stage of history. It is an important result of the poet's collision with life and events.
That is why I chose the lamentation poetry of Hafiz Ibrahim, due to the importance of this art to him, and it is the art in which he excelled the poets of his time.
I have divided this research into
This study is based on the basic idea: that human communication does not stop at the limits of words spoken, but extends to include the movements of the body and its members, such as the face, hand, eye, hearing, touch, taste, sensation and the public body.
The human movements represented by polarization, frowns, tattoos, and movements are all auxiliary tools that reach meanings and affect others greatly.
Perhaps their importance is also in their ability to translate what is going on in the soul, and to show it to the outside body members, without the control of the human in many cases, it is thus an important factor in the process of human communication.
The purpose of this study is to show the senses of the senses in the
Biomimicry, as a way of thinking to go back to nature for inspiration, has its impact on many contemporary technological achievements. Some of them are used to design and construct kinetic facades in architecture, because of the importance role of facades in reducing sun radiation, that enter the building through using shading systems and components. In light of this, research problem is determined: "Do technologies which are inspired by biomimicry effect shading in kinetic facades through its characteristics in materials and the mechanics. So the research identifies its goal as: "To identify the types of kinetic facades in buildings and their characteristics as materials and shading mechanism associated with the b
... Show MoreA survey of fish species in the Iraqi marine waters was carried out for the period from November 2014 to March 2018. The list included 214 species representing 75 families.
The family Carangidae dominated the marine fishes in Iraq, which was represented by 24 species, followed by Haemulidae with 11 species, and then Serranidae and Sparidae with nine species for each, while 34 families contained a single species only.
This research is based on the study of a group of Quranic verses that share a certain part, and these verses are verses of righteousness, and the word righteousness has been mentioned in the Holy Qur’an eight times, and the number of verses in this word was six verses, in four walls, all of which are from the civil fence which is the cow and was There are five words of righteousness contained in them, and the family of Imran is one word, and the table is one word, and the argument is one word. This study adopts the method of analytical interpretation of the Quranic text is a term that means statement and clarification in a way that the researcher produces to divide a Quranic text into its elements that are involved in its formation and
... Show MoreThree plant species were picked randomly and their alcoholic extracts have been screened to know their effects on the phagocytic capability and intracellular killing of yeast by human peripheral macrophages. Macrophage cultures were incubated with different concentration of each plant extract: for 15 min., 30 min .and 45 min. The phagocytes activity in Iresine herbstii extract was significantly (p?0.05) increased with increasing dose and time of incubation. In Mentha piperita extract, increasing in dose and time of incubation leads to elevate phagocytic capbility, especially in the dose of 20% and 25% of plant extract, perhaps because the antimicrobial and antiviral activities of this plant, as well as strong antioxidant and antitumor act
... Show MoreIn order to get an idea about things closely, we should look at the role of social discipline
in the building of society from civilization cultural viewpoint. The real weigh of the societal
opinion is not measured by the number of its population or its area but the real value lies in its
civilization cultural accumulative experience inherited by the generations, which determine its
distinguished character. That is based upon the social construction in which the methods of
socialization and political, economic, cultural and religious stability and enhance the national
and ethical character of self-realization.
In this research, we try to give an analysis for the obstacles in political economic and
religious social
Historical concepts are among the concepts that are difficult to present to the pre-school child except by using modern techniques, as well as the difficulty of making visits to all historical monuments and going back to antiquity and the lack of studies in this area, therefore, we need an attractive medium that children love which is able to convey some abstract concepts that are difficult to teach to children using traditional methods, and among these activities that the kindergarten provides to children are the stories through which they develop their linguistic wealth, consolidate their religious and spiritual inclinations, refine their correct morals, and form their proper attitudes, knowledge and life concepts.
The
... Show More