Influence of tea on intrinsic colour of previously bleached enamel.

Aim of the study was to evaluate the influence of tea applied at various time intervals after bleaching of enamel on intrinsic tooth colour. Ninety bovine specimens were distributed among six groups (A-F, n=15). The samples of group A-D were bleached with the 10% carbamide peroxide (CP) gel VivaStyle for 8 h, followed by storing in artificial saliva for the remaining period of the day. The specimens were removed from the saliva at different intervals (A: 0 min, B: 60 min, C: 240 min) and immersed in freshly prepared black tea for 10 min. Group D (bleaching, no tea), E (no bleaching, but tea) and F (no bleaching, no tea) served as controls. These procedures were repeated for 8 days. Colour was measured at baseline, after each day, and after final cleaning using the CIELab-system. Then Deltab (initial b-value - final reading), DeltaL, and composite colour (DeltaE) were statistically analysed. External bleaching (A-D) led to a distinct whitening effect with lower Deltab- (=reduction in yellow) and higher DeltaL-values (=increase in brightness) compared with controls. The Deltab- and DeltaL-values of the samples A-C were not significantly different from the samples which were bleached only. No significant difference was observed comparing specimens of group A-C. It is concluded that application of tea directly after bleaching with 10% CP does not significantly effect the outcome of a bleaching treatment irrespective of the time interval elapsed between the bleaching procedure and the contact of the tooth surface with tea.