Tori are extraneous bones that form in either the upper or lower jaw. They develop largely due to environmental conditions (for example local irritation), an uneven bite (misaligned teeth), or grinding your teeth. 

For most cases, the tori are benign and can be left untreated. However, when a patient needs to have upper or lower dentures/partial dentures, the tori will have to be surgically removed. Tori may also be removed to prevent the accumulation of plaque and periodontal pockets so as to allow easier access of toothbrush for good oral hygiene.

Once the tori are removed, they rarely come back.