If we are whitening something, it shows reconciliation. It can also mean that we appear to be good and innocent.
Dream dictionary: Whiten dream meanings
Teeth in dream represents parents or best friends. Teeth at the front, children or relatives of the nearest kin. Upper teeth indicates male, lower females. The right tooth represents the father, the left one the mother. The large teeth symbolizes distant relatives. Have teeth more beautiful or whiter than usual ones, implies joy, health, prosperity, friendship, good news of relatives. Have them of such a size that impede speaking or eating, denotes family quarrels, lawsuits for inheritance. Polish and whiten the teeth, money counted out to next of kin. Have a tooth larger than the others, affliction on account of parent. Tooth spoiled or gone, means loss of relatives or friends, explained in the foregoing manner. Merely loose, sickness or affliction of a relative or friend.