الفهرس 
Colour Stability and Microhardness of Ormocer Based and Nanohybrid Resin Composites With and Without Acidic Challenge: An In vitro Study
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Abstract
Resin composites are most commonly used because of their excellent mechanical and aesthetic properties, but the problem is consumption of acidic beverages can cause discoloration and softening of these materials, so questions have been raised about the effect of these beverages on the recently developed new restorative resin material. A total of 60 composite discs were used in this study, they were prepared in a Teflon mold (6x2 mm) and cured using Elipar light cure through a 1mm glass slide, then they were divided into 2 groups according to the type of the resin composite; ormocer and nanohybrid. They were further divided into 3 subgroups according to the immersion media; cola, orange juice and artificial saliva. Color measurement was carried out using the Easy vita shade and microhardness measurement was carried out using Vicker{u2019}s microhardness tester. The disks were stored in staining solutions for three hours per day in an incubator for 15 days and rinsed under tap wate. Results: Regarding the effect of different immersion media on mean {u2206}E: Cola has the highest mean {u2206}E on both the ormocer and nanohybrid resin composites (7.30±2.24), (4.53±1.03) respectively, which is statistically significant than the mean {u2206}E of orange 4.84±1.03, 3.24± 0.48 at p{u2264}0.0001. Also the mean {u2206}E of orange is statistically significant than the mean {u2206}E of the artificial saliva on both the ormocer and nanohybrid resin composites 2.78±0.86, 2.21± 0.72 respectively at p{u2264}0.0001