Measurement Of Color Stability Of Compomer Restorative Materials J. Manhart*, J.M. Powers, R. Hickel (Dept. Of Restorative Dentistry, LMU-University, Munich, Germany) Color stability is a crucial property of esthetic restorative materials. The aim of this study was to measure the color stability of compomers and a hybrid composite (control group) subjected to different staining solutions. Eight materials (Compomers: Compoglass F/Vivadent; Dyract/Dentsply; Dyract AP/Dentsply; F2000/3M; Hytac/Espe; Luxat/DMG; PrimaFlow/DMG; Hybrid composite: Tetric Ceram/Vivadent) with 5 replications each were investigated. 120 specimens (2 mm thickness, 10 mm diameter) were prepared in a PTFE mold between two microscopic glass slides and covered with a Mylar matrix before light-curing to ensure a smooth surface and avoid an oxygen-inhibited layer. All specimens were cured from both sides for 40 s with a light-curing unit (Optilux 400) with a 13 mm diameter tip. Specimens were stored for 24 h in an incubator at 37°C and 100% relative humidity before the baseline color data were measured with a reflection spectrophotometer (Color-Eye 7000) against a white background with spectral reflectance included. The CIE L*a*b* color system was used relative to standard illuminant A. The specimens were then immersed in the staining solutions (distilled water as control; red wine as hydrophilic colorant; sesame oil as hydrophobic colorant) for 8 weeks and measured again. Color differences (ΔE*) between baseline and 8-week staining were calculated from values of CIE L*a*b* according to the equation: ΔE* = [ (L*o-L*i)2 + (a*o-a*i)2 + (b*o-b*i)2 ]1/2. Mean values and standard deviations are listed in the table. Data were analyzed by two-way ANOVA and post hoc Tukey tests (a = 0,05). Superscript letters indicate statistically homogeneous subsets.     Water (control) - a Red wine - c Sesame oil - b Compoglass F (C) b,c 1,31 (0,29) 1,74 (0,36) 1,23 (0,12) Dyract (D) b,c 0,52 (0,13) 2,12 (0,66) 1,53 (0,36) Dyract AP (Y) c 0,80 (0,09) 2,73 (0,13) 1,62 (0,31) F2000 (F) c 0,38 (0,06) 3,39 (1,59) 1,42 (0,21) Hytac (H) a,b,c 0,87 (0,34) 1,64 (0,45) 1,23 (0,18) Luxat (L) a,b 0,53 (0,11) 1,30 (0,34) 1,01 (0,27) PrimaFlow (P) a 0,80 (0,22) 0,99 (0,18) 0,65 (0,38) Tetric Ceram (T) a,b 1,23 (0,15) 1,23 (0,47) 1,07 (0,04)   Statistical analysis revealed significant differences among the various materials as well as among the staining solutions. The staining potential of the colorants increased as follows: dist. water < sesame oil < red wine. Only F2000 stained with red wine exhibited a visually perceptible color change (ΔE*>3,3). All other materials demonstrated a high degree of color stability in spite of the extensive staining period of 8 weeks.