Statement of the problem:The effects of vital bleaching agents on color properties of dental tissues and direct restorative materials are well documented.However, there is a lack of information about the effects of these agents on low-fusing dental ceramics. Objective:The aim of the present study is the in vitro evaluation of the effects of two vital bleaching agents on the color features of three different dental ceramic materials.Materials & Methods: 60 sample discs of two different feldspathic ceramics and a full ceramic system were fabricated 12mm in diameter according to the manufacturers' instructions.The 1st feldspathic group was designated as C (n=20), the 2nd V (n=20), and the full ceramic group F (n=20).Prior to bleaching, L*a*b* values of each glazed sample were measured using a colorimeter.Each sample group was divided in two for the bleaching in two different derivations.Whereas the subgroups exposed to 10% carbamide peroxide were designated CR, VR, and FR; subgroups exposed to 16% carbamide peroxide were entitled CN, VN, and FN.Following bleaching, color measurements were repeated.Descriptive analysis of all data, consisting L*a*b*, ΔL*, Δa*, Δb*, and ΔE values of the two measurements, were performed.Obtained results were statistically analyzed with Kruskal-Wallis test.Results: Comparisons revealed no significant difference between the ΔL*, Δa*, Δb* values of the 6 groups.Also no significance was found between the ΔE results of the FR, FN and VN, VR groups (P = 0.1, P = 0.3).However, there was a significant difference between the ΔE values of the groups CN and CR (P = 0.001). Conclusion:Vital bleaching agents have the potential to alter the color features of ceramic materials.