Tooth discoloration like a green tooth can occur under many circumstances. Most often these stains are considered extrinsic, meaning they only affect the enamel and appear after the tooth develops. Causes of extrinsic discoloration include food and beverage consumption, tobacco use and tooth wear. In addition, not having an adequate oral hygiene routine may make the enamel more susceptible to staining. An intrinsic stain occurs when the internal part of the tooth, called the dentin, becomes discolored, most commonly during tooth development.
If you notice your tooth change color, see your dentist to determine the possible causes and treatment options.