الفهرس 
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Abstract
This study was conducted to investigate the effect of resin composite material type, different finishing tools and different beverages on the color stability of two resin composite materials Filtek Bulkfill and Filtek Z250XT(3M). A total of 60 resin composite discs of 10 mm diameter were used in this study. 30 specimens of each resin composite type which further divided into 3 groups(n=10) according to the finishing tool used. Each finishing group is further divided into two subgroups cola and coffee(n=5) with a total of 12 subgroups(n=5).The color of the specimens of each subgroup was measured before immersion in each beverage(baseline) and after one month.
VITA Easyshade Advance 4.0 was used for color measurement of the specimens. The Clarke’s formula20 of ΔE*ab = [(Δ L*) 2 + (Δ a*) 2 + (Δ b*) 2]1/2 was applied to calculate ΔE. A ΔE*ab of 3.3 units was utilized as the acceptability threshold beyond which color mismatch between two specimens is considered.51
Results of color measurements showed that ΔE was affected by both the finishing tool used and the beverage type. Coffee showed unacceptable color changes within all tested groups whereas Cola showed slight perceptible color change. Control groups cured against Mylar strip showed the least color change whereas groups finished with SofLex discs and fine diamond finishing stone with optionestep polisher showed higher color change. No statistically significant difference was found between the two tested resin composite materials on ΔE values.
Under the limitations of this study, these conclusions could be suggested:
1. The finishing/polishing methods and different beverages were significant factors that influenced the color change of resin composite.
2. Coffee produced significant color changes in the composite resin and was considered a strong staining agent.
3. The Mylar strip promoted the greatest color stability than the other finishing and polishing methods tested.
4. The highest color change value was obtained for the specimens finished by Soflex discs.
5. The type of resin composite material was not a significant factor regarding the susceptibility to discoloration with the tested beverages.