Also known as: Pseudocysts — Three year-old bumps


Eruption cysts are bony enlargements that can be observed in juvenile horses on the ventral aspect of the mandible and on the dorsolateral apect of the maxilla. In Thoroughbreds they usually arise in the mandible, and they are often in the maxilla in ponies.

They usually occur during eruption of the permanent premolars between 3-4 years of age.

The bumps are thought to be caused by the osseous and vascular changes occurring during root formation and permanent tooth eruption.

Vertical impaction due to excessive angulation or pressure from adjacent teeth has been presented as one of the causes of the bumps, however eruption cysts are usually self-limiting within 1-2 years and are only of cosmetic importance.

Clinical Signs

In general, eruption cysts are not noticed on the maxilla because of the overlying soft tissue.

Several swellings can usually be felt at the same time on the ventral aspect of the mandible. They should be of similar size and should not be painful or hot.


Clinical signs and signalment of the affected horse are usually sufficient for a diagnosis to be made.

If the bumps are painful or hot, this signifies a true impaction or infection and should be dealt with appropriately.

Radiography can be performed to evaluate the teeth and skull:

Eruption cysts appear as smooth-bordered, periapical lucencies with sclerotic margins. The developing cheek tooth will have a wide periodontal space, and there may still be the remnants of their deciduous precursors (caps).


No treatment is necessary and the cysts usually regress over 1-2 years.

Eruption Cysts Learning Resources
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Dixon, P. (2002) The gross, histological and ultrastructural anatomy of equine teeth and their relationship to disease IVIS Publication

McGorum, B. (2007) Equine respiratory medicine and surgery Elsevier Health Sciences

Linkous, M. (2006) Dental Conditions Affective the Juvenile Performance Horse (2-5 years) IVIS Proceedings

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