Dentigerous or Odontogenic Eruption Cysts in Jaws
Dentigerous cysts and other problems of non-eruption of teeth are relatively common (Verstraete FJM et al: JAVMA (2011): 239; 1470-1476), especially in Boxers and other breeds with similarly shaped skulls - such as Mastiffs. Mostly these cysts are associated with various unerupted teeth. Most commonly we see them associated with "missing" first premolar teeth and often involve considerable loss of bone in the rostral mandible or maxilla. Adjacent teeth also lose their bone support - including the canines.
A dentigerous cyst will usually be identified in association with a "missing" tooth and a soft fluid filled swelling that the owner may see a build up and rupture a clear fluid from time to time. There does not appear to be pain associated with them in the early stages.
The lesion is usually an expansion cysts filled with serum. Radiographs will quickly identify the location of the tooth and size of the cyst. There is often no indication from the dog that there is any problem.
Our practice policy is always to radiograph all "missing" teeth unless there is a known reason for their absence. Missing teeth are often not actually missing - just not visible. When missing teeth are actually present within the jaw bones they frequently cause considerable local pathology.
These images show a "missing" right mandibular premolar 1. The radiograph proves the tooth is embedded tooth and also shows the extent of the cyst & bone loss. Note the loss of bone to the distal aspect of the canine root.
We normally see these cases at 4 - 5 years of age at which point the cyst size can be extremely large. A secondary consequence of the loss of bone is that adjacent teeth often lose their attachment and are no longer anchored in bone.
Treatment requires surgical incision into the cyst, removal of the unerupted tooth and any other non-attached teeth. The secretory lining must then be removed before placement of a bone autograft or allograft. The graft is usually very well tolerated and will allow the cyst deficit to fill with new bone to resume normal strength.
The cyst is opened surgically and the unattached teeth removed along with the secretory lining. An allograft of demineralised bone matrix and cancellous bone is placed to stimulate induction of new bone into the area.
Since most breeds that suffer from dentigerous cysts are brachycephalic head shapes with the lower jaw in front of the upper, this resumption of strength is important to ensure no pathological jaw fractures over time.
The wound immediately post op and the healed wound one week later.
Radiograph pre and post op showing unattached teeth and placement of osteoallograft. Right image shows new bone colonisation four months later. Note the improvement of attachment to the canine tooth root and the formation of a new periodontal ligament.
It is clear from studies that a variety of odontogenic cysts can form in the jaw of a dog. The majority form in brachycephalic head shapes and crowding of teeth may play a part. The second most common cyst type has been termed canine odontogenic parakeratinised cyst (COPC) by Verstraete 2011 to reflect the histological findings. Submission of all removed material for histopathology is advised to ensure accurate diagnosis and prognosis.