الفهرس 
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Abstract
Summary and Conclusions
This study was conducted to evaluate the effect of the thickness of the surface layer (0.25, 0.50, 0.75 and 1 mm) applied over two different shades of opaque resin composite on a shade correction of a standard O3TN shade.
A total of 40 composite discs of 10 mm diameter and 2.5 mm thickness were prepared. The specimens were divided according to two factors: the opaque shades (O2 and O4) and the thickness of the translucent layer (0.25, 0.5, 0.75 & 1mm) (n=5). Additional five specimens (O3/TN) were added and served as control group, from which Delta E, Delta L and translucent parameter were compared. One composite brand was used; Amaris esthetic resin composite system (VOCO GmbH, Germany) and measurements were done using spectrophotometer.
The results of this study showed that all thicknesses of O2/TD and the 0.25mm thickness of O4/TL were at or below the acceptability threshold of ∆E value (∆E ≤ 3.3). All other O4/TL shades results were above the acceptable threshold. Shade correction using lighter opaque is less sensitive to surface layer thickness changes compared to dark shade
Conclusions
Under the limitation of this study, the following conclusions could be suggested:
1- The thickness of the translucent superficial layer of Amaris restorative material should be taken into consideration on correction of darker opaque shade.
2- Shade correction of lighter opaque shade was less sensitive to the changes in superficial layer thickness.
3- For correction of darker opaque shade, only a surface layer of 0.25 mm thickness was recommended.