الفهرس 
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Abstract
The aim of this in-vitro study was to assess the effect of the surface finish protocol of pressed zirconia reinforced lithium silicate ceramics on the surface roughness & color stability under
different pH oral media. Methodology: thirty surfaces (n=30) of pressed zirconia reinforced lithium silicate samples were tested, samples were fabricated and divided into two main groups (n=15) according to surface finish protocol; glazed group and polished group. Then, The samples of each group were further subdivided
into three subgroups according to the media tested (n=5): Artificial saliva, coffee, carbonatedorange juice. A cylinder of 10 mm diameter and 6.5 mm thickness was designed using Exocad software. five cylinders were milled from Cad wax blank, then the cylinders were invested for wax burnout procedure. afterwards, pressing of zirconia reinforced lithium silicate ingots were made. Each ceramic cylinder was cut into three discs with 1.5 mm thickness using isomet 4000. All the discs were finished
with fine grit diamond stone on both sides according to manufacturer instructions, a marginal notch
with a diamond stone was made on the side that will receive polishing to be able to differentiate between the polished and the glazed sides. Then, discs were glazed on one side and polished on the other side resulting in 15 glazed and 15 polished surfaces.
vii Standardized polishing of the discs was made on a dental surveyor. The surface roughness was measured using optical profilometer quantitatively and with scanning electron microscope
qualitatively and color was measured using spectrophotometer. afterwards, the discs were immersed in the aging solutions for 12 days simulating 1 year in-vivo. then, the surface roughness and color stability were remeasured after aging. The results were analyzed using Graph Pad Instat (Graph Pad, Inc.,USA) software for windows. A value of P < 0.05 was considered statistically
significant. After homogeneity of variance and normal distribution of errors had been confirmed, oneway ANOVA was done for comparison between groups followed by Tukey’s pairwise if showed
significant. Paired t-test was performed between paired surface finish groups. Also, two-way ANOVA was done to detect total effect of each variable (surface finish and immersion solution).