Because wisdom teeth are the last teeth to come through, often there is not enough room for them. An impacted Wisdom tooth is one that cannot fully erupt. This can result in food trapping and repeated infections.
To remove an impacted tooth, a flap of gum is raised and some bone is removed to gain access to the submerged tooth. The crown (top) of the tooth is then carefully removed and the roots are then separated. This allows the tooth to be removed in sections causing minimal damage to the surrounding bone and gum. The gum is then replaced and heals naturally.
More information on Wisdom Teeth