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 research aims to verifying the tax exemptions granted in accordance with the Iraqi tax legislations, showing their suitability for basic tax rules, and identifying their role to reduce the tax evasion phenomenon and the negative effects resulting therefrom, which arerepresented by a decrease in the proceeds of tax revenue and therefore leadings to a reduction of public revenues of the state. Also, the research tries to identify the ways to reduce cases of tax evasion due to their reflection positively on the public budgetof the state. The data of the research was collected through two models of questionnaires distributed to a sample of taxpayers from some professions and a sample of the tax administration staff. The research has reac
... Show MoreThe research seeks to know the social loafing of kindergarten teachers and their relation to personality traits. In order to achieve the research objectives, the researcher constructed the social loafing scale, which she applied to kindergarten teachers. The scale consists of (22) paragraphs. It has good credibility and stability. The coefficient of stability (85.0) was the retest method and (81.0) Alpha Cronbach equation. In addition, the researcher has adopted (Raymond Cattel) personality traits scale, which has been adapted to the Arab environment (Abdel Rahman and Abu Abada,1998), The scale consists of (39) paragraphs, and enjoys the apparent honesty. The measure of social loafing and the measure of personality traits was applied to
... Show MoreZora Neale Hurston's (1891-1960) is an outstanding African American
novelist, playwright, autobiographer and essayists. Her work is considered as an
important part of the African American and Harlem Literature.**** It represents a
milestone and a keystone in the African-American literary canon because it breaks
from the style of the previous works and makes a beginning of a new style. Hurston
shifts from the black works that stick to racial themes and sheds the light on new
aspects and themes in blacks' life especially on feminist themes. Her exceptional fame
culminates in her novel Their Eyes Were Watching God (1937). 1
Their Eyes Were Watching God examines with a great deal of artistry
the struggle of a black
The paper aims to build a model that supports organizational sustainability by analyzing the correlations and revealing the impact between the two main variables (entrepreneurial leadership) with its dimensions of proactive outlook, risk, and creativity (Van Zyl & Mathur-Helm, 2007), and (organizational sustainability) with its economic, environmental, and societal dimensions (Hansmann et al., 2012). As well as identifying the level of awareness and informing managers in the General Company for the Automotive and Equipment Industry, of the theoretical implications and performance, and its vital importance to society and the surrounding ecological environment, and drawing attention to that and improving performance, and indicatin
... Show MoreThe purpose of this study was to determine the impact of added soy protein humidifier concentration of different ratios of bovine Alberkr mix that was to bring the old chicken shop pure beef in five ratios
Summary This research, entitled (Distinguishing Voice Features of Qalqales Voices and their Expressive Values in the Holy Quran), aims to shed light on five of the voices that are characterized by strength and intensity, whose pronunciation requires loud vocal tone, great effort and semantic dimensions.The research consists of two topics .in the first topic. We talked about the voices of Alqalqal , their definition, their degrees, their ranks, and the opinions of scholars about them.
In the second topic, titled Expressive Values for Weak Voices in the Holy Qur’an, we talked about the relationship between sound and meaning, and we clarified in it the expressive values of Qalqa
... Show MoreBackground: Indeterminate colitis (IC), a term
originated by pathologists to characterize confounding
histopathlogic appearance of resected mucosa, has
become catch phrase for cases in which diagnostic
criteria at all levels elude classification as Crohn's
disease (CD) or ulcerative colitis (UC).
OBJECTIVES: evaluate the prevalence of pANCA
expression in the sera and its isotypes.
Patients and methods: PATIENTS GROUP
consisted of 60 patients (40 males and 20 females)
with indeterminate colitis and their age range was (19-
84 years). CONTROL GROUP consisted of 30 (15
males and 15 females) healthy volunteers and their
age range was (20- 66 years).
Antineutrophil cytoplasmic ( pANCA and cANCA)
te
Morphological and histoarchitecture aspects on the cerebrum of (barn owl) were made
to find outthe cerebrum size, design and the description of cerebral region components at the
light microscopic level by using Haematoxylin – Eosin and periodic acid schift (PAS)
stain methods. The result of the morphological aspects revealed that the cerebrum was large
and an obtuse triangle in shape, its surface had a slight furrow. Sagittal sections revealed
the location, arrangement and size of pallial and subpallial cerebral divisions. The result of
the microscopic examinations indicated that the large and massive hyperpallium (wulst) was
thick,hypertrophied wired, and multilaminate structure reflect their wider ste
The environmental cost management focus on continuous improvement of processes and the various activities of the organization in order to improve the environmental performance by producing an environmentally friendly products lead to a competitive advantage for the organization and supports the activities of their sustainability.
The study was carried out in Bagel cement factory, one of the pioneer projects in Yemen in manufacturing field, The study found the need to develop a separate section for environmental management in order to put plans and environmental policies and the introduction of a special division in the Department of costs cares about Management practices cost and measure environmental costs, also give solu
... Show MoreGenotypic detection of some Antibiotics Resistant genes by using polymerase chain reaction (PCR). (20) Isolates of Acinetobacter baumannii that showed resistance to (Ceftaxim, Cefotaxim, Cefepim and Imipenim) were selected. The results showed that 20 isolates of A. baumannii possess the bla-OXA23 like gene, and that all isolates possess this gene with a percentage (100%). With molecular weight 605 bp. The current study showed that A. baumannii isolates carry 100% bla-OXA51like gene when studied with (20) isolates that are resistant to antibiotics (Imipenim Ceftazidime, Cifepime, Cifexime) that belong to this group of β-lactame with molecular weight 382 bp. Gene exp
... Show More