The combination of intrinsic colour and the presence of extrinsic stains on the tooth surface influence the colour and thus the overall appearance of teeth. The scattering of light and absorption within enamel and dentine determine the intrinsic colour of teeth and because the enamel is relatively translucent, the dentinal properties can play a major role in determining the overall tooth colour. On the other hand, extrinsic stain and colour is the result of coloured regions that have formed within the acquired pellicle on the enamel surface and can be influenced by lifestyle behaviours or habits. For example, dietary intake of tannin-rich foods, poor tooth brushing technique, tobacco products, and exposure to iron salts and chlorhexidine can darken the colour of a tooth.