Whitening can improve your smile up to 8 shades. Zoom Whitening chairside bleaching will lighten your teeth by up to 12 shades. Depending on the amount of staining you have on your teeth, the number of treatments required will vary. This involves applying a protective gel to your teeth and gums, then using a special light to activate the bleaching agent. With proper care, whiter teeth can last for up to five years.