025 – Impacted Tooth

Impacted tooth is a tooth that is completely or partially unerupted and is blocked from other tooth, bone or soft tissue so that its eruption is unlikely.

The gradual evolutionary reduction of human jaws has resulted in jaws are too small to accommodate their teeth.  The third molar  (wisdom tooth) is the last tooth to erupt and so it may likely become either impacted or displaced if there is inadequate space for it within the dental arch.

Thus impacted third molars are frequently encountered in routine dental practice and one of the most commonly performed oral surgical procedures.


Many factors govern the decision to advise the removal of an impacted third molar especially the lower third molar.  Here are some reasons that indicate one for surgically removal of the impacted third molar.



Pericoronitis is inflammation of the soft tissues surrounding the crown of a partially erupted tooth. Recurrent pericoronitis is the commonest indication for the surgically removal of impacted lower third molar.



Dental caries

Food may easily get trapped between the impacted third molar and the second molar and one may find it difficult to keep it clean. The resulting retention of food debris and plaque may cause dental caries involving either the occlusal surface of the third molar or the distal surface of the second molar or in both teeth.

Periodontal disease

The third molar being situated so far behind in the mouth, one may find impossible to keep clean. High incidence of periodontal pocketing distal to the second molar has been observed among those with impacted third molar.


Presence of pathological lesion

Dentigerous cysts and tumors may be observed in some patients with embedded third molars, although they are relatively rare. A dentigerous cyst is a pathological cavity lined by epithelium and filled with fluid contents surrounding the crown of an unerupted tooth.


Trauma to opposing gums, cheeks, tongue

If a third molar erupts out of the normal alignment of teeth, it may cause trauma to the opposing gums, cheeks or tongue.


Late lower anterior crowding

The lower third molar is the last tooth to erupt, its growth may cause slight push the other teeth into a forward direction. As a result, the presence of lower impacted third molar is believed may result in late crowding of the lower incisor.


Classification of impacted third molar

Angulation of tooth

  • Vertical


  • Mesioangular

  • Horizontal


  • Distoangular


  • Buccoangular
  • Linguoangular
  • Inverted

Following is a case report of surgically removal of impacted lower right third molar.

A 29-year-old lady came complaining of repeated swelling of the gum surrounding the crown of impacted lower right third molar for the past few months. Intraoral examination showed the gum surrounding the crown of lower right third molar slightly inflamed and the tooth was vertically impacted.


A panaromic image was taken on the same day (shown below).

After discussing with this patient, she decided to remove the tooth. Local anesthetic was given to numb the area where the tooth would be removed. Once the tooth was numb, the gum tissue over the tooth was opened to expose the whole crown of the tooth. Sometimes any bone that is covering the tooth may need to remove but not in this case. The tooth was later removed by using an elevator.

The wound was cleaned and closed with stitches.

Medications were then prescribed and postoperative instruction was given to her. One week later she came back for removal of stitches and review.

Prepared by

Dr Lim Ming Chau