This study was designed to evaluate the effect of water absorption of three resin based composite materials on their color stability Methods: using scanning spectrophotometer. A total of 45 disc samples were constructed from microhybrid resin composite, polyacid modified resin composite and giomer. It should be mentioned that the selected shade is A2. Then inserted in water for water absorption test. Using five different drink [mouth rinse (37•C) (Chlorohexidine containing mouthwash), tea,

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... e, red wine and de-ionized water (37•C)] with no exposure to a light source (neutral sample). Three specimens from each restorative material were made for each type of drink. All the color testing were carried out according to the CIE-L * a * b * -color system whereby L * indicates the brightness of a color, a * describes the red-green content and b * the yellow-blue content.