1) Change of color 2) Changing to a lighter color 3) Claim for many a toothpaste 4) Lightening 
• (n.) The act or process of making or becoming white. • (n.) That which is used to render white; whiting. • (p. pr. & vb. n.) of Whiten
The process of lightening discolored or stained teeth. Treatment can be in-office or at-home.
Process of removing the bran layer of grain during milling.
Whit'en·ing noun 1. The act or process of making or becoming white. 2. That which is used to render white; whiting. [ R.] Whitening stone , 
[n] - changing to a lighter color
lightening noun changing to a lighter color
People with stained or dull teeth will benefit from whitening systems should be individually fitted and monitored by your cosmetic dentist. a safe, effective means to whiten stained, discoloured or dull teeth.