Leukoplakia is a condition in which thick, hard, white patches that cannot be wiped off form inside the mouth. Leukoplakia is commonly caused by irritation, such as from rubbing of a rough tooth or poorly fitting denture, or from smoking or using smokeless tobacco.
Leukoplakia may clear up if the source of the irritation is removed, by fixing the tooth or denture or stopping tobacco use. It may take several weeks or even months for the leukoplakia to go away completely.
In some cases, leukoplakia can be an early sign of cancer of the mouth.
WebMD Medical Reference from Healthwise