A tooth is considered impacted if it fails to erupt through the gums, or erupts only partially by the expected age. Wisdom teeth or the third molars are the last teeth to come out or erupt. There is one wisdom tooth on each side of the jaw. They usually erupt after the person is 16 years old, most commonly between the age of 16-20 years. As these are the last permanent teeth to erupt they often cause problem and can become impacted. Wisdom tooth may get impacted if the space left in the mouth is not adequate to accommodate them when they erupt.
At times they may become impacted if it turns to one side, gets tilted or is positioned erroneously in the jaw.
An impacted tooth may cause no problems or may become painful when it tries to erupt. The pain can radiate or may be felt in nearby teeth or the ear on the same side. A partially erupted tooth can cause other problems like gum swelling, tooth decay, change in bite (the way the teeth come together), and an infection (pericoronitis) due to collection of food and other debris under the gum. Impacted tooth can cause formation of a follicular (dentigerous) cyst as well. This can injure nearby teeth and even destroy the nearby bone.