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
In the present study, an attempt has been to develop a new water quality index (WQI) method that depends on the Iraqi specifications for drinking water (IQS 417, 2009) to assess the validity of the Euphrates River for drinking by classifying the quality of the river water at different stations along its entire reach inside the Iraqi lands. The proposed classifications by this method are: Excellent, Good, Acceptable, Poor, and Very poor. Eight water quality parameters have been selected to represent the quality of the river water these are: Ion Hydrogen Concentration (pH), Calcium (Ca), Magnesium (Mg), Sodium (Na), Chloride (Cl), Sulphate (SO_4), Nitrate (NO_3), and Total Dissolved Solids (TDS). The variation of the water quality p
... Show MoreIn this research study the synodic month for the moon and their
relationship with the mean anomaly for the moon orbit and date A.D
and for long periods of time (100 years), we was design a computer
program that calculates the period of synodic months, and the
coordinates of the moon at the moment of the new moon with high
accuracy. During the 100 year, there are 1236 period of synodic
months.
We found that the when New Moon occurs near perigee (mean
anomaly = 0°), the length of the synodic month at a minimum.
Similarly, when New Moon occurs near apogee (mean anomaly =
180°), the length of the synodic month reaches a maximum. The
shortest synodic month on 2053 /1/ 16 and lasted (29.27436) days.
The lo
The objective of this study is to enable the role of modern and advanced computerized information systems. The model or mechanism should be developed by collecting the necessary information about the taxpayers and the sources of the taxpayers' income, on the basis of which the accuracy of the inventory process will be adopted. In addition to studies related to computerized information systems and showing their importance to the tax institution. To achieve the objectives of the study and to answer its questions, the researcher relied on collecting data and information on the subject on the literature and previous studies The secondary sources, which also formed the theoretical framework of the study, were obtained either as a practical fr
... Show Moreمدة تولي رئاسة السلطة في الفكر السياسي الاسلامي المعاصر
The purpose of this research is to highlight the nature of the relationship between the mental abilities of decision makers and strategic orientation . The intellectual capacity of decision-makers is the cornerstone for the implementation of all the tasks and duties of the Organization and constitutes the most important of its capabilities. As a result of the sharp changes in the environment in which it operates, this organization must accurately define its strategic directions to ensure its
survival and continuity. The problem of field research was to answer a fundamental question: Is the Iraqi director aware of how to employ mental abilities in strategic direc
... Show MoreThe researcher aims to detect the emotive equanimity in kindergartens teachers,also to uncover the anxiousness in children of kindergartens,then to detect the relationship between them,then to choose the simple random way which is about(180) teachers and children,when the twore searchers made two tools to measure the emotive equanimity and the anxiety for both teachers and children,statistical methods had been used include:(pearsons correlation coefficient,t-test for one sample,t-test for two independent samples are individuals).the researcher led to multiple results:
1-the teacher has an emotive equanimity.
2-children has no anxiousness.
Background: Post-extraction alveolar ridge resorption is unavoidable phenomenon ending with insufficient ridge width. Measuring the physical dimensions of the available bone before implant surgery is an important aspect of diagnosis and treatment planning. Bone height can be calculated from radiographs, while bucco-lingual ridge width can be measured by conventional tomography, CT scanning and ridge mapping.
Radiographic techniques have certain disadvantages. Therefore the ridge mapping technique was used as an option for determining alveolar ridge width.
The purpose of this study was to compare the validity of alveolar ridge width measurements obtained with ridge mapping technique before surgical flap reflection against
... Show MoreThe paper shows how to estimate the three parameters of the generalized exponential Rayleigh distribution by utilizing the three estimation methods, namely, the moment employing estimation method (MEM), ordinary least squares estimation method (OLSEM), and maximum entropy estimation method (MEEM). The simulation technique is used for all these estimation methods to find the parameters for the generalized exponential Rayleigh distribution. In order to find the best method, we use the mean squares error criterion. Finally, in order to extract the experimental results, one of object oriented programming languages visual basic. net was used
The research risk of flooding on six water basins located in the eastern part of the western plateau, reached total area of the basin (22,998.9 km 2), has reached all the Basin area (basin to time 7056.1 km2 basin by 3585 km 2, Bath Alheiazi 6404 km 2, Abu beasts 544.1 km2 basin Abu Shannan 144.6 km 2, Bath Valley Faraj 5265.1 km 2), where it was specifically spatial degree of this risk by studying some of the hydrological basin transactions directly related to operations spate runoff study area and the occurrence of flood risks on the surface of ponds.
This study aims at recognizing the levels of comprehension of the students of basic schools to the concepts of mathematical geometric and discovering the existing of the differences among students in the level of understanding of the concepts of mathematical geometrical which is due to the change of gender.
The sample of the study is the students of Basic schools, eight level in the basic school of Erbil city, particularly 7-8-and 9 levels in the academic year 2013-2014. The sample consists of 444 students in both genders238 males and 206 females.
The tool of the study is test sheet included 20 items of multiple choice. The items are valid since are given to a jury of expert
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