ABSTRACT Background: Color changes that are detectable to human eye can affect the esthetic appearance of ceramic veneers. The purpose of this study was to evaluate and compare the effect of artificial accelerated aging on the color of ceramic veneers cemented with different resin cements. Materials and Methods: Sixty discs were prepared with 0.5 mm thickness, 30 discs made from IPS e.max press (Ivoclar Vivadent) and 30 discs were made from VITA Enamic (VITA Zahnfabrik). The discs were cemented with three resin cements: Variolink Veneer MV 0 shade (Ivoclar Vivadent), Rely X veneer Translucent shade (3M ESPE) and NX3 Nexus Clear shade (Kerr Corporation) with 0.1 mm thickness. The spectrophotometer Easyshade Advance was used to measure the color parameters (Lightness, axis a* of chroma and axis b*of chroma) immediately after cementation, after 150 and 300 hours of aging. The specimens were subjected to artificial accelerated aging in Accelerated Weathering Tester. Color change greater than 3.3 was considered unacceptable. One-way ANOVA, paired t-tests and Bonferroni adjusted t-test were used for statistical analysis (p <0.05). Results: Artificial aging caused high significant color change in both ceramic types, but there were non-significant difference in color change among the three resin cements used. The color change was between1.997-14.8 after 150 hours and it was between 2.179-15.68 after 300 hours. The color change of e.max discs after aging were within acceptable limit<3.3 whereas Vita Enamic specimens had shown unacceptable color change >3.3 after aging. Conclusions: The majority of color change after aging related to veneering materials while resin cement have only slight effect on color change after aging. IPS e.max had shown an acceptable color change after aging, so it is suitable for fabrication of restorations in esthetic zone while Vita Enamic should not be used in esthetic zone since it has poor color stability according to the results of this study.
In this study, experimental mortar combinations with 1% micro steel fibers, were examined to create geopolymer mortars. To test the effect of the fibers on the mortar's resistance, the geopolymer mortar was designed with various proportions of more environmentally friendly materials fly ash and slag. The percentage of fly ash by weight was 50, 60, and 70% of the slag. The best results were obtained when a 50:50 ratio of fly ash and slag were mixed with 1% micro steel fibers. The results showed that the mixtures containing fibers performed better in the considered tests (toughness index, ductility index, and resilience index). In the impact resistance test, the mixture contained 50% fly ash by weight of the slag with a temperature of
... Show MoreThis study aims to recognize the most common thinking styles and level of the need for cognitive university students , the relation between thinking styles and the need for cognitive, and there are differences according to gender .The sample consists of (250) males and females university students for the academic year (2013-2014), and the researcher uses two scales;" thinking styles scale (Harison &Bramson, 1986), and the need for cognitive scale" (Cacioppo, Petty & Kao , 1996).
The results show that there is difference in the range of the prevalence of the thinking styles among university students , the scientific thinking style is the most common , the students have got the arrange level of the need for cognitive , and there
A kindergarten teacher is one of the most important elements in the educational process, since she is totally relied upon in kindergartens. Therefore, she could have basic and healthy characteristics to improve the educational process by directing the child towards a perfect growing upEducating and raising up a child should be an organized process that makes desirable changes in the child’s behavior in order to improve different sides of his personality, such as his appearance side, his mental side, and his social side.
This research aims at:
1- Measuring the scientific brilliance in kindergarten teachers.
2- Investigating the statistical significant differences of the scientific brilliance among kindergarten teachers in accor
The current study aims at identifying:
1-The intellectual stress of counselors according to gender variable (male, female ).
2-The five major factors of the Counselor's Personality.
3- The relationship between intellectual stress and the five major factors of the councilors' personality and according to gender variable (male, female ).
4-The significant differences in the relationship between intellectual stress and the five major factors of the councilors' personality and according to gender variable (male, female ).
The sample of the study includes (260) counselors (130 male
... Show MoreVerbs in German and Arabic are of two types: active and passive. Passive voice is a grammatical voice construction that is found in many languages. Out of grammatical perspective, each main verb has a form in the active and one in the passive known as a "genus verbi" (type of verb). In passive voice, both in German and in Arabic, the focus is on the action itself or on the result of the action; often the perpetrator is not mentioned. In German, to conjugate verbs in the passive voice, you must know the forms of werden (to become). German uses werden + the past participle and states it at the end of a sentence. In Arabic,
... Show MoreThis paper investigates the experimental response of composite reinforced concrete with GFRP and steel I-sections under limited cycles of repeated load. The practical work included testing four beams. A reference beam, two composite beams with pultruded GFRP I-sections, and a composite beam with a steel I-beam were subjected to repeated loading. The repeated loading test started by loading gradually up to a maximum of 75% of the ultimate static failure load for five loading and unloading cycles. After that, the specimens were reloaded gradually until failure. All test specimens were tested under a three-point load. Experimental results showed that the ductility index increased for the composite beams relative to the reference specim
... Show MoreABSTRACT A simple, accurate, sensitive, and low-cost technique was advanced to measure the optical spectrum to the determination of lansoprazole in pure form and dosage forms. The method relies on the oxidation of the reagent 2,4-dinitrophenylhydrazine (2,4-DNPHz) with potassium periodate (KIO4) and coupling with the Lansoprazole (LPZ) in the alkaline medium to form a stable with reddish-brown colored dye with a maximum greatest absorption at 484.5 nm. The reaction is carefully completed when optimizing the variable affecting it. The concentration range from 1-30 μg/mL obegs Beer’s law and the molar absorptivity value of (13260.132) L/mol.cm. Detection limit was (0.1266 μg/mL) and Sandell’s sensitivity value ( 0.0278) μg/cm2. The met
... Show MoreIn this paper has been one study of autoregressive generalized conditional heteroscedasticity models existence of the seasonal component, for the purpose applied to the daily financial data at high frequency is characterized by Heteroscedasticity seasonal conditional, it has been depending on Multiplicative seasonal Generalized Autoregressive Conditional Heteroscedastic Models Which is symbolized by the Acronym (SGARCH) , which has proven effective expression of seasonal phenomenon as opposed to the usual GARCH models. The summarizing of the research work studying the daily data for the price of the dinar exchange rate against the dollar, has been used autocorrelation function to detect seasonal first, then was diagnosed wi
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