الفهرس 
AcknowledgementOnly 14 pages are availabe for public view
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Abstract
This study designed to evaluate the effect of resin cement shades and thickness of zirconia reinforced lithium silicate (Vita Suprinity) on the optical properties using dark background and compared to lithium disilicate glass ceramics (IPS E.max CAD). A total of 56 Vita Suprinity (n=28) and IPS E.max CAD (n=28) plates were sectioned under water irrigation with a precision cutting machine IsoMet 4000 into rectangular plates with a dimensions (12 x 14 mm) two thicknesses 1.0 and 1.5 mm, then a digital caliper was used to check that the specimen’s thickness. Either types of ceramic plates were crystallized and glazed according to manufacturing instructions. Also a 56 composite plates with a dimensions (12 x 14 mm) and 2 mm thickness, were made from C3 shade using an especially designed teflon mold. A 56 cement plates with a dimensions (12 X 14 mm), 0.2 thickness and 2 shades yellow (n=28) and transparent shade (n=28) were constructed using especially designed split mold. All samples (56 samples) divided into to two main tested groups according to ceramic material type, group (1): (28 Samples) Zirconia reinforced lithium silicate (Vita Suprinity) (S) and, group (2): (28 Samples) Lithium disilicate (IPS E.max CAD) (E) each group was further divided into two subgroups according thickness of each ceramic plate, subgroup: 1.0 mm thickness, subgroup: 1.5 mm thickness, each subgroup was subdivided into two divisions according to cement shade into division T: transparent cement shade, division Y: yellow cement shade. The ceramic plates of each materials and thicknesses were optically connected with DROP of distilled water to either two cement shades plates and the dark background. L*, a* and b* parameters of ceramic-composite assembly and ceramic-cement-composite assembly were measured for all tested groups and the color change (ΔE) and were calculated through the following equations
ΔE* = (L*0 - L*w)2 + (a*0 - a*w)2 + (b*0 - b*w)2
Where
ΔE*: color change
0: ceramic-composite assembly without cement
w: ceramic- cement – composite assembly :