From Longman Dictionary of Contemporary Englishwhitenwhit‧en /ˈwaɪtn/ verb [intransitive, transitive] CCto become more white, or to make something do this This stuff is supposed to whiten your teeth.→ See Verb table
Examples from the Corpus
whiten• I looked at Jack and saw him whiten.• Already frost was whitening every wrinkle of her sleeve.• Makeup began to whiten his lapels like droppings on a statue.• Jack's knuckles whitened on his glass.• Palomar students periodically hike to the top of the peak to whiten the letter.• Outside, a light snow had begun to fall, whitening the streets with downy flakes.• It whitened the terrace beyond with a clear, unbroken glare.• He wore a white dhoti and his body was whitened with ash. 