Anatomy and physiology
Rabbits have 6 incisors (4 upper and 2 lower). The 2 first incisors are large and oppose the lower incisors. The 2 second
upper incisors are called 'peg teeth' and are located just caudal to the first incisors. The incisors are relatively long
compared with the cheek teeth. The incisors have a beveled cutting edge with both the upper and lower incisors being sharp
on the rostral aspect. When the mouth is closed, the lower incisors rest on the peg teeth caudal to the upper incisors. Rabbits
use the sharp edges of the incisors to cut off grasses. The roots of the incisors are dramatically curved and very long. They
are deep to the roots of the cheek teeth and extend very caudally in the mandible and maxilla.
The cheek teeth consist of the molars and premolars. Rabbits have 3 upper premolars and 3 upper molars and 2 lower premolars
and 3 lower molars. There is a lot of action during chewing between the upper and lower cheek teeth grinding fibrous grasses.
They move in a rotary manner going both side-to-side and cranial to caudal. This crushes the grasses that the rabbit has cut
off with the incisor.
All of the teeth of rabbits grow continuously and do not overgrow because they are worn down by the opposing teeth. They depend
on mastication to wear the crowns. New crown is produced below the gingival surface and continually pushed up into the oral
cavity. Wild rabbits spend most of the day eating dry grasses, providing the necessary wear on the teeth crowns. Dental crown
reduction is not necessary in normal rabbits. Overgrowth occurs if the rabbit does not wear the crowns sufficiently. Additionally,
if the crowns are not worn adequately, root ankylosis occurs. The crown is stopped from moving and the root begins to grow
into bone.
It seems likely that most rabbit dental problems are related to inadequate amounts of long fiber in the diet. Many rabbits
are fed a pelleted diet composed of finely ground alfalfa easily crushed by rabbits. Dry grasses must be ground up before
they are swallowed and this grinds the crowns allowing the root to push new crown up keeping the teeth and roots healthy.
Presenting complaint
Anorexia is a common presenting complaint and dental disease should be considered in any rabbit that presents for anorexia.
Rabbits with dental disease are considered to be in pain and do not swallow as much as they normally would. They often have
wet fur around the muzzle and ventral cervical fur. Ocular discharge is a presenting complaint that should make the clinician
think of dental disease. The upper cheek teeth roots are close to the nasolacrimal duct. If ankylosis occurs, the roots grow
away from the mouth and compresses or invades the nasolacrimal duct. Tears no longer drain properly and epiphora results.
The discharge may be clear or may contain white, flocculent material. It seems that if the root tip is infected and breaks
into the nasolacrimal duct, it causes the discharge to be more purulent in nature. Some rabbits will present for overt malocclusion
of the incisor teeth. Many rabbits with primary cheek teeth disease present for incisor malocclusion which is actually secondary
to abnormal cheek teeth. Do not just trim the incisors without investigating the cheek teeth. If the cheek teeth crowns overgrow,
the mouth no longer closes properly which affects the occlusion of the incisors.
