-  Tetracycline administration during pregnancy can lead to  discoloration of teeth as the tooth erupts 
   in the newborn.  Depending on the severity, discoloration can range from  yellow -orange in mild 
   cases and bluish gray in the most severe cases.
-  Flurosis is a condition seen in places with increased  fluoride content in the drinking water. Beyond a
   certain level, fluoride can cause yellow staining of teeth.
-  High fever due to childhood infections can lead to areas of poor calcification within the teeth 
   resulting in the appearance of prominent white spots.
 
Extrinsic stains can be classified based on color of the stain into:
- Brown stains: It is caused by a thin translucent, bacteria free layer covering the teeth. It is seen in
   individuals who do not brush their teeth adequately, or in  those who use toothpaste with 
   inadequate  action.
- Tobacco stains: Dark brown or black surface accompanied by brown discoloration of the tooth 
  substance is seen. These stains results from coal tar combustion present in the tobacco and also 
  due to the diffusion of tobacco juices into the substance of the teeth.
- Green stains: Green to greenish yellow stains, sometimes of considerable thickness is seen in 
  children. It is usually seen in upper anterior teeth and has been attributed to florescent bacteria and 
  fungi.
- Orange stains : Occurs in front teeth, and is caused by color producing bacteria.