الفهرس 
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Abstract
The purpose of this study is to investigate the effect of different stains on Omnichroma nano filled composite resin restorations compared to a conventional nano hybrid composite resin restorations. Materials and methods: Human sound sixty intact upper premolars previously extracted for periodontal or orthodontic reasons were selected for this study. Each tooth was fixed with sticky wax to the base of a plastic cylinder filled with selfcuring acrylic resin 2mm below the cement-enamel junction. The primary color of teeth was recorded using Vita Easy shade V, shade A2 was selected. A trapezoidal class V cavity was prepared on the buccal surface of each tooth using fissure carbide bur in a high speed hand piece with air water spray, cavities had a width of 4 mm occlusally and 3 mm gingivally and 3 mm occluso cervically .The cervical margins were located 2 mm coronal to cementoenamel junction .All cavities were 2mm in depth, a 45 degree bevel was placed on the occlusal and gingival walls of the cavity. Teeth were randomly divided into 2 groups (n=30) according to the type of restorative material used: group I: cavities were restored with Omnichroma composite resin. group II: cavities were restored with Tetric Evoceram composite resin. All specimens were incubated at 37oC, 100% humidity in artificial saliva for 24 hours, then were subjected to 500 thermo cycles between 5oC and 55oC, 30 sec dwell time and a transfer time of 15 sec, to represent clinical service of 6 months. The color of teeth and restorations (base line data) was recorded by Vita Easy shade V. Each group was randomly subdivided into three sub-groups (n=10 specimens) according to the immersion solution (stain): Sub-group (A): Artificial saliva solution was prepared. Sub-group (B): coffee solution was рreрared by mixing 3.6 g of coffee powder in 300 ml of boiling water (Nescafe Classic, Nestle, Indonesia). Sub-group (C): Tea solution was prepared by immersing 5 pre-packaged doses of tea powder into 500 mL of boiling distilled water for 10 min. Each immersion solution was poured into a strainer. Specimens were incubated in the solutions for 48 hours at 37°C. All specimens were washed using distilled water for 30 sec after removal from stains and dried by using blotting paper. Color measurements were performed using Vita easy shade V dental device. All data was collected, tabulated and statistical analysis using independent T-test and performed by Statistical Package for Social Science (SPSS version 26). Results: The statistical comparison performed between (ΔE) values at baseline between groups revealed that there was no significant difference between both tested groups neither at teeth with p-value (0.914), nor at the restorations with p value (0.172). Comparison within each group showing that there was no significant difference in ΔE neither at group I (Omnichroma) with p-value(0.718) nor at group II (Tetric Evocerm) with pvalue (0.275) .This was also expected since all restorations were carefully selected to adapt the shade of all restored teeth. Statistical analysis of (ΔE) after 48 hours immersion in saliva (subgroup A) of group I (Omnichroma) versus group II (Tetric Evoceram) regarding both teeth surfaces and composite restorations. It was observed that there was no significant difference between both tested groups neither at the teeth with p-value (0.972) nor between restorations with p value (0.335). In addition no significant difference of ΔE was observed comparing teeth versus composite neither at group I (Omnichroma) with p-value(0.660) nor at group II (Tetric Evocerm) with p-value (0.560) indicating that the saliva didn’t affect the color of teeth or restorations significantly after 48 hours immersion at both tested groups. Regarding statistical analysis of ΔE after 48 hours immersion in coffee (subgroup B) between group I (Omnichroma) versus group II(Tetric Evoceram) regarding both teeth and restorations. It was noticed that there was no significant difference between both tested groups at teeth with pvalue (0.647) ,but there was a significant difference of ΔE at the composite with p value (0.001) indicating higher ΔE mean values of Tetric Evoceram (𝑋 ̅=3.98) compared to Omnichroma ( 𝑋 ̅ =2.39), comparing teeth versus composite within each group .No significant difference of ΔE was recorded at group I (Omnichroma) with p-value(0.370) on the other hand there was a significance difference of ΔE at group II (Tetric Evocerm) with p-value (0.027) . Moving to immersion in tea (subgroup c) for 48 hours, independent ttest was used to compare mean values of (ΔE) between group I (Omnichroma) versus group II (Tetric Evoceram) regarding both teeth and restorations. It was observed that there was no significant difference between both tested groups at tooth with p-value (0.610), on the other hand a significant difference between the restorations with p value (0.004) was recorded. Another comparison was performed between teeth versus composite within each tested group showing no significant difference within group I (Omnichroma) with p-value (0.576), while a significance difference was recorded within group II (Tetric Evocerm) with p-value (0.004). All immersion solutions were analysed, a comparison was performed using ANOVA test regardless the type of composite resin tested .A significant difference in ΔE was recorded between the three immersion solutions with p value (0.000) .whenever a significant difference was recorded, Tukey`s test was performed. This led to fetch out which immersion solution was responsible for significant difference. It was found that the responsibility fell on the 48 hours immersion in saliva. All collected data for tested specimens were analysed to conclude the difference in color of teeth and composites of both groups between baseline and after 48 hours immersion in different solutions, recording a statistical significant difference for teeth of group I and group II with P value (P=0.006, 0.001) respectively, also for composites a statistical significant difference for group I and group II with P value (P=0.033, 0.000) respectively. The (ΔE) between both tested groups regardless the immersion solution was analysed. A significant difference was recorded with p value of 0.006 using T-test.