evaluation of the effect of different herbal tea on discoloration of different kinds of composite

objectives: the aim of this study was to evaluate the effect of six herbal teas on the color stability of two types of nanohybrid and one microhybrid resin composite.  materials and methods: 70 disc-shaped specimens, 210 in total (7*2mm), were fabricated from each of the following materials in metal mould : tetric n ceram, grandio, gradia direct anterior. specimens were stored in distilled water at 37°c for 24 hours in an incubator for completion of polymerization. after baseline evaluation (l*, a*, b*cielab scale), the specimens were divided into seven subgroups, according to the test and control storage solutions (n=10). randomly selected specimens from each material were immersed in 20 ml of the test solutions (borago, green, hibiscus, thyme, black and lemon verbena teas) at 37˚c for 24 hours and 48 hours. solutions were refreshed every 24 hours. all samples were polished using soflex discs with medium, fine, superfine grit after storage in herbal teas. specimens color was measured in 24, 48 hours and after polishing. the collected data was statistically analyzed using two-way analysis of variance with repeated measure and tukey’s hsd at a significance level of 0.05. results: all samples displayed color changes after immersion in the herbal teas. hibiscus tea induced the highest level of discoloration after 24 hours immersion in all three composites. black tea induced highest level of discoloration in (grandio δe=7.44). hibiscus tea and thyme tea induced highest level of discoloration in (tetric n ceram δe=11.) and (gradia direct δe=14.11), respectively, after 48 hours immersion. the least discoloration was found with borage tea in 24 and 48 hours. after re-polishing the color change was reduced. grandio showed the greatest color reduction in black tea. color improvement of tetric n ceram was better than gradia direct. conclusion: all tested restorative materials showed a color shift after immersion in herbal teas, which tetric n ceram displayed the highest color change in hibiscus tea and borago tea induced lowest discoloration on grandio after 24 h immersion. thyme tea induced the highest level of discoloration on gradia direct and least discoloration was found in borago tea on grandio after 48 hours immersion.