A four-month-old rabbit with an obvious dental abnormality is shown.
Question
Answer
Article
What is the condition shown, and what is the most likely aetiology in this case?
Incisor malocclusion.
Given the age of the animal, the most likely aetiology is that of a congenital conformational problem, resulting in an excessive length of the mandible relative to the maxilla. This is often referred to as mandibular prognathism, although the actual defect lies in the shortening of the maxilla and is therefore perhaps more correctly described as maxillary brachygnathism (all these terms being borrowed from human dentistry).
Unopposed growth and eruption of the mandibular incisors leads to obvious forward protrusion, while the lack of labial occlusal pressure results in a permanent straightening of the tooth.
However, the greater curvature of the maxillary incisors, maintained by contact of the labial surfaces with the mandible, causes them to curl caudally into the oral cavity and eventually into the hard palate.
The condition has been shown to be an inherited, autosomal, recessive trait, especially in Dwarf and Lop breeds, in particular the Netherland Dwarf. However, all breeds can be affected. Given the hereditary nature of the condition, the rabbit should be neutered or not bred from and any siblings or progeny should be examined.
Alternative aetiologies include
dental trauma,
inappropriate trimming and
acquired malocclusion, the latter being unlikely given the age.
Management of the condition involves trimming the teeth using a high-speed burr.
In cases of congenital malocclusion (and long-standing acquired cases with straightening of the mandibular incisors), this must be done repeatedly, perhaps as often as every 4–6 weeks, as the teeth can never be brought back into occlusion.
However, with care this procedure can be achieved without an anaesthetic.
The use of nail clippers is contraindicated as this will result in longitudinal fractures, pulp exposure and concussive trauma to the apical germinal tissues.
A permanent solution is extraction. Each surgically loosened tooth is finally pushed into the alveolus before extraction in order to destroy the germinal tissues at the apex. Failure to do so completely may result in the continued growth of an abnormal tooth, as it will fracture below the gingival margin at the time of surgery.
The owner should be warned of this possibility at the outset.
Radiography should be performed preoperatively to assess the extent of dental disease.
