The process by which teeth darken after whitening procedures. If you’ve used a light-activated system, there is a mild relapse within the first 1 or 2 weeks, as your teeth go from a brighter white to a more stable and sustainable color. With tray bleaching systems, the bleaching process is slower, so the relapse, too, is less dramatic–with teeth settling into a sustainable whiteness after two or three weeks. Regardless of which whitening process you use, however, normal wear and tear will eventually cause teeth to stain. Some foods and beverages, and of course smoking, produce pigments that are absorbed by your teeth. So even after whitening treatments, your teeth will absorb these stains and you will need touch-up treatments every year or two to maintain them at their brightest white.