There are two factors causing tooth discoloration- internal factor and external factor.
Habitual smoking or drinking of dark-coloured beverages, such as tea or coffee, result in the food colours being adsorbed onto the tooth surfaces.
The dentist will use:
Do not smoke and avoid drinking dark-coloured beverages to minimize food colours being adsorbed.
Teeth has not been cleaned thoroughly, and the accumulated dental plaque contained bacteria or fungi that can produce colour and formed green and orange stains.
Dentist will perform scaling to remove accumulated dental plaque and stains.
Brush every morning and before bed at night, and use dental floss to remove dental plaque to keep the teeth white.
The dentist removes the tooth decay, and then puts on a filling.
The pulp becomes necrotic because of tooth trauma or tooth decay, and the tooth will appear greyish-black.
Endodontic treatment must be done to treat the discoloured tooth which has pulp necrosis.
Disturbance during the development of tooth
If a deciduous tooth is so decayed that the pulp is exposed, the bacteria, via the apex of the tooth, will cause an infection in the vicinity of the developing permanent successor. This will disturb the development of the enamel of the permanent tooth, resulting in the formation of brownish-yellow patches.