Objective: Compare three color measures using data from the same group of people. Typically in bleaching studies, color is measured using value-ordered shade guides and electronic devices. Color change is reported in tabs and De*ab units. For small color differences, De 2000 may be more accurate. Methods: After giving written informed consent, 20 people used a placebo bleaching gel for two weeks. Using a value-ordered shade guide (Vita Classical, Vident) and a reflectance spectrophotometer (Easyshade, Vident), the six maxillary anteriors were measured pre-operatively and at one, two and four weeks. L*a*b* were recorded and color change calculated, CIE De* ab. After conversion to L*C*H*, CIE De 2000 was calculated. Shade tabs were numbered from one (C4) to 16 (B1), and tab change calculated as Tab# at evaluation minus preop Tab#. Results: One, two and four week tab-changes were one, two and zero respectively. At two weeks the change was significant (p = 0.005). CIE De* ab and De 2000 demonstrated no significant color change (p = 0.38 and p = 0.68). For L*C*H* data, DL*, DC* and DH* were not significant. For L*a*b*, Db* was significant at four weeks and Da* at two and four weeks (p < 0.05). All tests were RM ANOVA on Ranks. Conclusion: For De* ab and L*a*b* changes in the three components of color are not consistent with the overall finding. For De 2000 and L*C*H*, the component changes support the overall finding. Color change results from the active ingredient and transient tooth drying caused by the gel. After cessation of bleaching, color change regresses. The finding of an observable color difference during bleaching but not overall is consistent with the biologic process. The shade guide data reflects these changes while the spectrophotometry data do not. This study was supported by Ultradent Products, Inc.

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