Background: evaluate the effects of three different intracoronal bleaching agents on the shear bond strengths (SBS) and failure site of stainless steel and monocrystalline (sapphire) orthodontic brackets bonded to endodontically treated teeth using light cured orthodontic adhesive in vitro. Materials and methods: Eighty extracted sound human upper first premolars were selected, endondontically treated and randomly divided equally (according to the type of the brackets used) into two main groups (n = 40 per group). Each main group were subdivided (according to the bleaching agent used) into four subgroups 10 teeth each; as following : control (un bleached) group, hydrogen peroxide group (Hp) 35%, carbamide peroxide group (CP) 37% group and sodium perborate (SP) group . The bleaching process was applied three times (4 days intervals) sequentially and the bleached teeth were stored in artificial saliva four weeks before bonding. Orthodontic brackets were bonded with a light cure composite resin and cured with LED light. After passing 24 hours of bonding procedure, the brackets were debonded by a Tinius-Olsen universal testing machine, to measure the shear bond strength. After debonding, each bracket base and the corresponding tooth surface were examined using a stereomicroscope and their Adhesive Remnant Index (ARI) was recorded. Results: The ANOVA test showed that the SBS of stainless brackets was significantly reduced by intracorornal bleaching agents. Furthermore, LSD showed no significant difference in SBS between the three types of bleaching agents used in stainless steel group. Whilst for sapphire group, the results The ANOVA test showed no significant difference in SBS between the bleached groups and the control group. Chi-square comparison no significant difference in failure site between bleached and control groups in both brackets types used. Conclusion: The effect of intracoronal bleaching on SBS was reduced SBS of stainless steel and not for sapphire. However, the intracoronal bleaching had no effect on the failure site of orthodontic brackets used.
Summary of the research Family violence, its causes and effects on society (women and children). Search Goal: The current research aims to identify: 1. Causes of family and social violence (for children and women). 2. How to process. research importance : Domestic violence is a major and devastating problem that has a negative and direct impact on children in particular and women or mothers in general. The problem of domestic violence is linked to many factors and individual, social, economic, psychological and environmental variables, which makes one theory that claims to be inaccurate. It is difficult to understand the nature of family violence without linking it to some of the concepts related to it. The negative effects that may lead
... Show MoreThis research involves studying the mechanical properties and corrosion behavior of “low carbon steel” (0.077wt% C) before and after welding using Arc, MIG and TIG welding. The mechanical properties include testing of microhardness, tensile strength, the results indicate that microhardness of TIG, MIG welding is more than arc welding, while tensile strength in arc welding more than TIG and MIG.
The corrosion behavior of low carbon weldments was performed by potentiostat at scan rate 3mV.sec-1 in 3.5% NaCl to show the polarization resistance and calculate the corrosion rate from data of linear polarization by “Tafel extrapolation method”. The results indicate that the TIG welding increase the corrosion current d
... Show MoreThe present study deals with the optimum design of self supporting steel communication towers. A special technique is used to represent the tower as an equivalent hollow tapered beam with variable cross section. Then this method is employed to find the best layout of the tower among prespecified configurations. The formulation of the problem is applied to four types of tower layout
with K and X brace, with equal and unequal panels. The objective function is the total weight of the tower. The variables are the base and the top dimensions, the number of panels for the tower and member's cross section areas. The formulations of design constraints are based on the requirements of EIA and ANSI codes for allowable stresses in the members
GH and IGF-2 were examined histologically in the present study on adult hens to learn more about the organs’ responses to GH and IGF-2. Cardiac protein synthesis is stimulated by GH and IGF-2, according to microscopic examination. The recent research found a considerable amount of adipose tissue in the cardiac muscle bundles, which is linked to the metabolic process. In addition, GH and IGF-2 were shown to promote protein synthesis and mitosis in liver and gizzard tissues, according to the research. In addition, the apoptosis, regeneration, and secretory activity of gizzard glands are increased by the aforementioned hormones.
Wellbore instability and sand production onset modeling are very affected by Sonic Shear Wave Time (SSW). In any field, SSW is not available for all wells due to the high cost of measuring. Many authors developed empirical correlations using information from selected worldwide fields for SSW prediction. Recently, researchers have used different Artificial Intelligence methods for estimating SSW. Three existing empirical correlations of Carroll, Freund, and Brocher are used to estimate SSW in this paper, while a fourth new empirical correlation is established. For comparing with the empirical correlation results, another study's Artificial Neural Network (ANN) was used. The same data t
... Show MoreA novel welded demountable shear connector for sustainable steel-concrete composite structures is proposed. The proposed connector consists of a grout-filled steel tube bolted to a compatible partially threaded stud, which is welded on a steel section. This connector allows for an easy deconstruction at the end of the service life of a building, promoting the reuse of both the concrete slabs and the steel sections. This paper presents the experimental evaluation of the structural behavior of the proposed connector using a horizontal pushout test arrangement. The effects of various parameters, including the tube thickness, the presence of grout infill, and the concrete slab compressive strength, were assessed. A nonlinear finite element mode
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The current research aims to construct a scale for the nine types of students’ personality according to Rob Fitzel model. To do this, (162) items were formed that present the nine types of personality with (18) items for each type. To test the validity of the scale, a sample of (584) students of Al-Mustansrya University were chosen. The data of their responses was analyzed by using factor analysis. The findings explored (9) factors as one factor for each type of personality with (12) items for each one. Then, the reliability of the scale was found by using the test-retest method and Alfa Cronbach method.
An experimental and numerical study was carried out to investigate the heat transfer by natural convection in a three dimensional annulus enclosure filled with porous media (silica sand) between two inclined concentric cylinders with (and without) annular fins attached to the inner cylinder under steady state condition. The experiments were carried out for a range of modified Rayleigh number (0.2 ≤Ra*≤ 11) and extended to Ra*=500 for numerical study and for annulus inclination angle of (δ = 0˚, 30˚, 60˚ and 90˚). The numerical study was to give the governing equation under assumptions that used Darcy law and Boussinesq’s approximation and then it was solved numerically using finite difference approximation. It was found that t
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Statistical control charts are widely used in industry for process and measurement control . in this paper we study the use of markov chain approach in calculating the average run length (ARL) of cumulative sum (Cusum) control chart for defect the shifts in the mean of process , and exponentially weighted moving average (EWMA) control charts for defect the shifts for process mean and , the standard deviation . Also ,we used the EWMA charts based on the logarithm of the sample variance for monitoring a process standard deviation when the observations (products are selected from al_mamun factory ) are identically and independently distributed (iid) from normal distribution in continuous manufacturing .