Effect of bleaching on vital discoloured teeth--a colorimetric evaluation in three patients.

Vital bleaching is considered effective for reduction of tooth discolouration. This evaluation was to measure colour changes before and after bleaching of vital tetracycline-discoloured teeth in three patients. Vital bleaching of their anterior maxillary teeth was performed five times at weekly intervals. Tooth colour was measured with a small-area colorimeter before, immediately and two, four and six months after bleaching. The results were expressed in the CIE L*a*b* colour system. The L* value, a lightness variable, increased after bleaching. The a* value changed only negligibly, but the b* value decreased after bleaching showing changes in the tooth colour from yellow to blue. The colour differences before treatment and six months after bleaching was visually perceivable.