Despite the fact that permanent teeth are expected to last a lifetime, there are several reasons why some teeth have to be extracted. One of the common reasons is when a tooth is damaged too much, either by trauma or decay or fracture. Other reasons are:
Severe overlap: The orthodontist will order extractions when there is not enough room for all the teeth.
Severe periodontal disease causing the loss of most of the tissue supporting the tooth.
Wisdom teeth are often extracted because the jaws are too small to accommodate them. Thus, they cannot completely come out in the mouth and remain partially covered by the gum. Food and bacteria can get trapped under this layer of gum tissue and cause infection. We generally choose to extract wisdom teeth before age 25 because bone healing is optimal and less chance of complications.
More serious problems can develop from impacted teeth (completely buried in bone) such as infections, damage to other teeth and bone, or the formation of cysts.