There are two types of tooth discoloration, depending on what causes them, namely: Extrinsic and Intrinsic stains. Extrinsic stains occur on the outer layer of a tooth, the enamel. When teeth surfaces are not smooth due to lack of proper oral hygiene or brushing technique, the enamel walls become rough and invite stains from such substances as coffee, tea, cola, nicotine and the like.

Intrinsic stains are found underneath the enamel in the dentin – the second covering layer of a tooth. There are dentins that by nature are yellowish in color. Intrinsic stains are usually caused by smoking, defects in the anatomy of a tooth, or occur as side effects from antibiotics that were taken during the developmental stage of tooth formation. Generally, as we get older, teeth become more yellowish due to the thinning of the enamel layer.