Tooth Whitening Sumamry This lesson is intended to give an overview of the causes of tooth discolouration, aspects to consider when undertaking tooth whitening and what is involved. Causes of tooth discolouration (1) Tooth discolouration has a wide variety of causes. These can be split into: Intrinsic, extrinsic and internalised causes. These will briefly be discussed below but the reader is advised to refer to the 3 rd party references (1) for further details on each of the causes. Intrinsic causes: ReviseDental.com