الفهرس 
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Abstract
This study was conducted to determine the effect of home and office bleaching agents on color and surface roughness of different thicknesses of hybrid resin ceramics.
Forty disc shaped samples were fabricated (20 sample of each ceramic material. Samples of Vita Enamic were represented in group I whereas samples of Lava Ultimate were represented in group II.
According to thickness samples of each group was divided into two subgroups; subgroup T1 & subgroup T1* representing 1 mm thick discs and subgroup T2 & subgroup T2* representing 1.5 mm thick discs (10 samples each). Samples of each subgroup was divided into two classes according to the used bleaching technique; home (carbamide peroxide) and office (hydrogen peroxide) that were represented in class T1CP, T1HP, T2CP, T2HP & T1*CP, T1*HP, T2*CP, T2*HP (5 samples each).
Samples were obtained from CAD/CAM blocks cut with a water-cooled diamond at speed 200-5000rpm in 50rpm increments using a linear precision saw machine (Isomet 4000, Buehler, Illinois, USA).Samples of both materials were finished and polished using vita Enamic Technical Kit. After that all samples were cleaned by ultrasonic cleaner.
Surface roughness of the samples of both tested materials was measured before treatment with bleaching agents using a tactile profilometer (Surftest SJ 201, Mitutoyo, Tokyo, Japan). The measured roughness parameter Ra was recorded and served as base line (total numbers of forty samples).
Color measurements were done using a portable spectrophotometer (VITA Easyshade Advance 4.0, Vita Zahnfabrik, Bad Säckingen, Germany) for all the samples before treatment with bleaching agents and served as base line (total numbers of forty samples).