Tooth discoloration generally falls into two categories.
Extrinsic stains develop on the surface of the enamel and are often caused by coffee, tea, wine, tobacco, dark-colored foods, and inadequate brushing.
Intrinsic stains occur deeper within the tooth and may result from aging, medications, trauma, or excessive fluoride exposure during childhood.
Most at-home whitening methods primarily target extrinsic stains, which explains why some people see noticeable improvements while others experience little change.
