Background: One common undesirable side effect of orthodontic treatment with fixed appliances is the development of incipient caries lesions around brackets, particularly in patients with poor oral hygiene. Different methods have been used to prevent demineralization; the recent effort to improve the resistance against the demineralization is by the application of lasers. Materials and method: Thirty human premolars extracted for orthodontic purposes were used to test the effect of two energy level of ER-YAG laser on enamel resistance to demineralization. The brackets were bonded on the teeth and all the labial surface excluding 2 mm area gingival to the brackets were painted with acid resistance varnish. Three groups were generated. The first group was the control group (A), with no treatment was performed. In group II (B)and groups III (C); teeth were irradiated by ER-YAG laser of 200, 60 mj energy respectively. All the teeth were individually subjected to acid challenge cycle for 30 days. After debonding longitudinal sections were taken and examined under stereomicroscope. The enamel demineralization evaluation was done by taking the average of three depths at the centre of the artificial lesion. Also the enamel surface was classified by an experienced investigator according to acid etch pattern. Comparisons of the average depth values of the groups were performed with ANOVA and LSD tests. The statistical significance level was set at p ≤ 0.05. Results: The results revealed that average lesion depth was significantly deeper at the control group than the laser groups, and its significantly deeper in group (B) 200 mj than in group (C) 60 mj, enamel surfaces showed deeper pits and craters than in control group. Conclusions: the decrease in artificial caries lesion depth associated with use of the two laser energy level support the ER-YAG laser as a tool to increase enamel resistance to demineralization and white spot lesion prevention. Key words: Demineralization, ER-YAG, laser.
Wars represent one of the most serious threats to the world order; It is considered a violation of international laws and norms, and humanitarian principles. From this point comes the study of the importance of the topic entitled (The Future of the Russian-Ukrainian war and the extent of its Reflection on the security of Eastern European countries after the year 2022). This study is based on reviewing future possibilities (scenarios) of war. The Russian-Ukrainian war, which was launched by the Russian government led by Russian President Vladimir Putin in February 2022, is still ongoing at the time of writing this research. This chapter includes three possibilities (scenarios). The first possibility deals with the development of the war t
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The political system in Indonesia, since gaining independence from the Dutch colonialism on the seventeenth of August 1945, has gone through long stages. The Indonesian constitution stipulated that the country is based on a democracy. In 1956 the first free elections were held in Indonesia, and President Sukarno announced the adoption of the directed democratic system Then, during the era of President Suharto, the state entered a phase called democracy based on the Five Pancasila principles, which is a false democracy because it served the interests of Suharto, who in his long reign had political and economic corruption leading up to 1998, when the Indonesian people revolted, and the government of Soeharto was overthrown
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Frictional heat is generated when the clutch starts to engag. As a result of this operation the surface temperature is increased rapidly due to the difference in speed between the driving and driven parts. The influence of the thickness of frictional facing on the distribution of the contact pressure of the multi-disc clutches has been investigated using a numerical approach (the finite element method). The analysis of contact problem has been carried out for a multiple disc dry clutch (piston, clutch discs, separators and pressure plate). The results present the distribution of the contact pressure on all tShe surfaces of friction discs that existed in the friction clutch system. Axisymmetric finite element models have been developed to ac
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The techniques of contemporary Iraqi painting and their reflection on the productions of students of art education is an important subject in the field of painting at the theoretical and practical levels in academic study, whether theoretical or practical. Al-Iraqi is one of the arts with historical roots and a distinguished position among other artistic genres. Painting has received a sufficient level of development through the use of various contemporary techniques to advance it for the better.
The methodological framework included the problem of research and the need for it, and then the importance of research came in shedding light on the techniques of contemporary Iraqi painting, and the impact of these techniques on the producti
The influence of fear on the dynamics of harvested prey-predator model with intra-specific competition is suggested and studied, where the fear effect from the predation causes decreases of growth rate of prey. We suppose that the predator attacks the prey under the Holling type IV functional response. he existence of the solution is investigated and the bounded-ness of the solution is studied too. In addition, the dynamical behavior of the system is established locally and globally. Furthermore, the persistence conditions are investigated. Finally, numerical analysis of the system is carried out.
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There are Islamic sources and books that deal with the different doctrinal and differential framework of the Islamic religion with a monistic approach, describing them with embarrassing jurisprudential titles such as: excommunication and expiation, and epithets that carry the characteristics of hatred and rejection, in addition to removing them from the sect and religion, and the reason for that is that the doctrine (A) or (b) considers itself the doctrine that represents only the Islamic religion, and other doctrines are misguided and disbelieving. the reasons behind this - besides the attempt to establish doctrinal and fiqih rooting in claiming truth and escaping from within the foundational differential doctrinal system – is the pol
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Objectives: To determine the effectiveness of physical education program on the domains of the university
students attitudes of physical activity and health, physical activity and mental health, physical activity and nutrition
toward physical fitness.
Methodology: A quasi-experimental design is carried out throughout the present study with the application of
test-retest approach through the period from February 3rd 2013 to June 30th 2013. The study is conducted on
purposive sample of(40) Undergraduate Students at the College of Science University of Baghdad . The sample is
Consisted of (20) males and (20) females. Questionnaire of two main parts, Personal and demographic
information and students' attitudes about phys
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