Cause of discoloration ? smoking, coffee, tea, drugs, aging, staining food (wine, blueberry, etc) genetics. Advice deep cleaning, polishing along with whitening (bleaching) procedures and / or artificial enamel. Use snowdent tooth paste for whitening until then. Apply snowdent paste on the teeth. Wait for 10 to 15 min .then brush your teeth with the same paste. Applying it overnight for better results.