Wisdom teeth are the third set of molars located in the very back of the mouth. They are the last teeth to grow in, usually between the ages of 17 and 21.
In many people, wisdom teeth are unable to grow in normally. The teeth either become stuck under the gum or are only able to partially break through the gum. Dentists call these teeth impacted. Wisdom teeth usually become impacted because the jaw doesn't have enough space for all the teeth that are growing in, or because the tooth comes in at the wrong angle and bumps into the tooth in front of it. Impacted wisdom teeth are fairly common. Although some people never have any trouble with them, impacted wisdom teeth can cause problems. An impacted wisdom tooth can sometimes trap food, plaque, and other debris in the soft tissue around it, leading to swelling, gum tenderness, cavities, and bad breath.