Intrinsic stain of tooth enamel may result from ingestion of excessive amounts of fluoride or prolonged systemic tetracycline administration during critical periods of tooth development. Fluoride is a compound that contains fluorine, a natural element. Fluorosis is associated with excessive fluoride ingestion during enamel formation. It is commonly seen as a mild discoloration in the presentation of a white lacy intrinsic stain, and is permanent.
Discoloration does not occur from limited tetracycline use (such as from a 7-10 day course of the drug). Crown formation of permanent teeth is usually complete at age 8, after which tetracycline use will not result in discoloration of enamel.
Extrinsic stain is usually an accumulation of materials on the enamel surface from foods, medications, or microorganisms. Iron drops cause a black to grey discoloration that is easily removed by the dental professional. Other metal sulfides may also give a similar appearance.