Figure 5. External in-office bleaching of teeth #11 and #21 in a 52-year-old woman. (A) Both teeth had become discolored in the mesial part after restoration of small Class II cavities with composite resin material 20 years previously. This is a known side-effect of some of the first-introduced composite materials. Replacement of the restorations with a new composite material did not remove the discoloration located in the surrounding dentin and enamel. (B) The result after external in-office bleaching with 35% hydrogen peroxide and heat (from two light-curing units) twice and for 30 min each with an interval of one week. Although the restorations were not removed during treatment, an acceptable result was obtained. (C) The result 4 yrs after bleaching. Only slight relapse was visible. (D) 8 yrs after bleaching. A moderate recurrence of discoloration is visible, but the patient did not need re-treatment.