Characteristics:

a) Commonest cyst of the alveolus.

b) Unilocular cyst arising in connection with normally erupted but chronically infected and decayed or pulpless tooth.

Aetiology:

Gross pathology:

a) Unilocular cyst with the apex of related tooth attached to outer wall of cyst.

b) Lining of the cysts: Stratified squamous epithelium.

c) Content: Usually sterile on culture with cholesterol crystals.

Clinical features:

1. Predominantly adults.
2. Slowly and painlessly enlarging swelling over a long period.
3. Site: Common in upper incisors, canine and premolar region.
4. Can give rise to localized expansion of jaw.
5. Egg shell crackling in advanced stage.
6. Associated with caries tooth.
7. Cyst of upper jaw tend to extend to maxillary sinus and inferior meatus and may present with nasal discharge.

Radiological feature:

1. Unilocular oval or circular radiolucent area in relation to the root of tooth.
2. Translucent area may have a thin rim of sclerosed bone.

Treatment:

Surgical:
Total excision of the cyst is done by intraoral approach. A transverse incision is made over the mucoperiosteum at the maximum point of concavity. Membrane in the epithelial lining as a whole should be scooped out together with the related tooth. No pathological membrane must be left behind as it has ameloblastomatous potential.