Teeth discolouration is when the enamel (the hard, outer surface of the tooth) or the dentine (the layer below the enamel) becomes discoloured. Something as simple as food and drink may cause stains to appear on the teeth.
For stained or discoloured teeth, bleaching can lighten teeth that have not responded to professionally cleaning. It is a safe procedure when done by a qualified dentist. Bleaching may not be appropriate in people who have oral symptoms of some disease.