Our teeth become stained and discoloured over time for a number of reasons. Smoking does not do them any favours and nor does drinking tea and coffee, cola and red wine and eating highly coloured foods such as curries. All this good living contributes to the dulling or staining of the porous enamel which covers our teeth.

Some tooth whitening products contain high levels of silica which can scratch the enamel and damage the tooth surface and others have added detergent which removes some of the stain, but can taste a little bit like soap.