September 2007
Dr Gerhard Steenkamp

A 3 year-old rabbit is presented with overgrown incisors as shown.

a) What are the causes for over erupted incisors in rabbits?
b) What is the treatment of choice for over erupted incisors?
c) What are the dangers in using nail clippers or side cutters to trim incisor teeth?

Memo

a) The three most common causes for rabbit incisor malocclusion are hereditary skeletal or dental anomalies, dietary related or through trauma.  Heritable (skeletal malocclusion) is common in the dwarf breeds of rabbits.  These patients usually present at a much earlier age with signs of malocclusion. 

The normal diet for rabbits is grass which leads to continuous wear of the teeth (approximately 3mm per week).  With commercial rabbit foods (as with horses) very little wear of the teeth is evident.  All teeth in rabbits are elodont (continuously growing).  Since the premolars and molars are not worn away sufficiently on these commercial diets, they will elongate and force the jaws apart.  As the jaws are forced apart the normal occlusion of the incisors are lost and malocclusion of the incisors occur. 

With trauma to the elodont tooth displacement of the continuously erupting tooth germ will result in a tooth growing in an abnormal direction.  This results in malocclusion with abnormal wear.

b) Over erupted incisors should never be treated on its own.  Understanding the implication of diet in these animals a three pronged approach is needed;

1. Correct the diet.  Grass should constitute 80% or more of a rabbit’s diet.

2. Inspect the premolar and molar teeth for elongation or enamel spikes and correct these first.

3. Amputate the incisors using a dental drill unit only!  The amputation should be done at the correct angles in order for the incisors to have a normal occlusion after the treatment.  Should the pulp be exposed as in the accompanying picture, suitable pulp treatment should be done.

In cases where the malocclusion can not be corrected, the teeth should be surgically removed through a specialised procedure which will be discussed in a later issue.

c) Cutting of incisors using nail clippers or a side cutter is both ethically and scientifically unacceptable.  Due to the structural features of dentin and enamel of teeth, it is inherently very hard and brittle.  By applying forces with instruments such as these to a tooth, it will shatter instead of being cut in a predictable manner.  The shattering of these teeth is uncontrollable and can lead to fractures extending into the root with possible pulp exposure.  Apart from pain and tooth loss due to the pulp exposure, the aim of sectioning these teeth is to correct the occlusion and by shattering the structure in many pieces, this will not be achieved