[In vitro tests of internal tooth whitening agents on colored solutions do not replace tests on teeth]

Two in vitro tests for the assessment of whitening agents were evaluated. A simple, reproducible and cost-effective model using coloured solutions was compared to a tooth model. The following bleaching agents were investigated: 1) Sodium perborate tetrahydrate/30% H2O2, 2) sodium perborate tetrahydrate/3% H2O2, 3) thermocatalytic procedure with 30% H2O2 and 4) Opal-escence Endo. In the model using coloured solutions, the light absorption of the solutions was assessed one and 24 hours after application of the whitening agents. In discoloured teeth, whitening agents were placed in a simulated access cavity. In groups 1, 2, and 4, the agents were left in the cavity for three days, whereas in group 3 the substance was applied three times for 30 seconds. Bleaching processes were repeated three times. All bleaching agents proved effective in the model with coloured solutions, as well as in the tooth model. The effect was most pronounced after the first bleaching step. The results showed, however, that the simplified experiment with coloured solutions cannot replace the tooth model.