Tooth whitening is done to correct the discoloration of a tooth. When we talk about discoloration of a tooth, we mean to say that the color of a tooth has changed from its normal white color to light yellow, yellow, light brown to dark brown or from light grey to dark grey or to complete black. The discoloration may be of one tooth or all the teeth may be discolored. Discoloration of a tooth is caused by several factors. It may be due to deposition of external stains over the surfaces of a tooth or it may be because of the internal position of certain chemicals into the teeth structure at molecular level during the period when teeth were being formed in the mother’s womb.