Answer : Whitening is any process that will make teeth appear whiter. This can be achieved in two ways. Bleaching products can bleach the tooth, which means that it actually changes the natural tooth color. Bleaching products contain peroxide(s) that help remove deep (intrinsic) and surface (extrinsic) stains. By contrast, non-bleaching whitening products contain agents that work through physical or chemical action to help remove surface stains only. The most commonly observed side effects are tooth sensitivity and occasional irritation of the soft tissue. There are two approaches to whiten your smile: In-office bleaching and at-home bleaching.