The Max White Overnight White Whitening Serum by Colgate can remove tooth discoloration from the last 15 years*. The patented serum can be easily applied to the teeth with the precise applicator. During sleep, the whitening serum forms a transparent film on the teeth, which can be removed the next morning with the toothbrush. On top, the formula is gentle to the enamel and dries quickly. *After 3 weeks of continuous use, discoloration that has been stored in the enamel over time.