When wisdom teeth are prevented from erupting into the mouth properly, they are referred to as being impacted. Teeth that have not erupted are not necessarily impacted. It may be that it is still too early in someone's dental development, and if time passes they might grow in properly. 

A dentist must examine a patient's mouth and his or her X-rays to determine if the teeth are impacted or will not grow in properly. Impacted teeth may cause problems, such as infection, decay of adjacent teeth, gum disease or formation of a cyst (fluid-filled sac) or tumor from the follicle, which is the tissue that formed the crown of the tooth. Many dentists recommend removal of impacted wisdom teeth to prevent potential problems.