In Vitro Staining of Nanocomposites Exposed to a Cola Beverage

The objective of this in vitro study was to assess the color change of resin nanocomposites exposed to a cola beverage at different times. Seventy-five cylinders (10 mm x 2 mm) were prepared from each of 4 resin-based composite materials, 3 nanocomposites (Filtek Supreme, Tetric EvoCeram, Premise) and 1 microhybrid (Filtek Z250), to give a total of 300 specimens. Specimens in each group were divided into 5 subgroups (n=15) and immersed in Coca Cola Classic beverage (Coca Cola Co., Atlanta, GA, USA). Color was measured at time 0 (subgroup 1) and after 24 hrs (subgroup 2), 48 hrs (subgroup 3), 1 wk (subgroup 4), and 2 wks (subgroup 5) by using a spectrophotometer (Color Eye 7000, Gretag Macbeth LLC, New Windsor, NY, USA). The mean color change (ΔEab*) for each material subgroup was calculated at each time interval. Data were analyzed using 2-way ANOVA, with the level for statistical significance set at α=0.05. Significant color differences were observed among all materials at all time periods, in particular after 2 weeks (P<0.05). Values reported after 2 weeks for the nanocomposites were clinically unacceptable (ΔE >3.3). Filtek Z250 showed the least color change among the materials at different times. Based on the results, it can be concluded that a microhybrid resin composite showed the least color change and remained clinically acceptable after continuous exposure to a cola beverage.