Many people think of rabbits as rodents, but they are lagomorphs. Both rodents and lagomorphs have open-rooted teeth (continuously growing throughout life). Rabbits have incisors (front teeth) which are easily visualized and a good set of molars in the back of the mouth for grinding and chewing that are not readily visible. Unlike rodents, however, lagomorphs have two small, tube-shaped incisors (peg teeth) behind the large upper incisors. Since the teeth continuously grow, the upper teeth must meet the lower teeth in order to allow for proper wearing of the teeth, thus preventing overgrowth. All teeth must meet and wear at the same rate as they are growing, or problems will arise.
"Lagomorphs have two small, tube-shaped incisors (peg teeth) behind the large upper incisors."
Malocclusion (imperfect positioning or meeting of the teeth when the jaws are closed), improper growth or wear patterns, and overgrowth of the incisors and/or molars can occur. Overgrown points or sharp spikes may cut and badly damage the tongue, cheeks or gums. In the case of overgrown lower molars, they may form a bridge over and entrap the tongue. Overgrown molars can change the way the incisors meet and therefore affect normal wearing. Misshapen incisors and malocclusion of the incisors will sometimes cause these front teeth to protrude out of the mouth, grow at an angle to each other, curl back into the mouth, curl sideways or take on other problematic positions. All this can lead to infections in the mouth, difficulty eating, drooling, pawing at the mouth, problems grooming and loss of weight. Teeth normally grow at a rate of approximately 1 cm each month and in the case of an unopposed incisor, growth can be as much as 1 mm per day.
Why do these teeth grow abnormally?
The cause of tooth elongation, malocclusion (not meeting properly) or improper growth and wear rates is likely multifactorial. A significant contributing factor is not providing a diet with enough roughage to promote normal wear of the teeth. Malocclusion may also have a hereditary or congenital component especially in young, dwarf or lop-eared rabbits. Severe dental disease or infections of the tooth roots will lead to improper growth (and hence improper wear) or changes to the shape and texture of the tooth (like curling, bending or twisting). Trauma or fractures of the teeth (particularly the front incisors) may change the way a tooth grows, as it may be misaligned and not meet its apposing tooth.
What can be done about this?
It is imperative that your rabbit is on a proper diet so that it chews its food well and wears down its teeth in the process. Overgrown incisors should be shortened or trimmed; this usually needs to be done regularly as the teeth continue growing. Veterinarians used to clip rabbits' teeth with nail clippers but occasionally this damaged the teeth or gums. These days, most veterinarians that regularly treat rabbits use dental burrs on dental drills to file down the incisors, often under anesthesia. Treating poorly aligned molar teeth can be more challenging, but filing rather than clipping is considered optimal today. If a particular rabbit is having recurrent dental problems, one long-term solution is to remove the affected upper and lower incisors or the affected molars. This procedure may be simple or complex, depending on the tooth, its location in the mouth and its condition. Although it sounds drastic, it is without doubt the best long-term solution to the problem if chronic overgrowth occurs.
"Overgrown incisors should be shortened or trimmed"
Following tooth filing or extractions, it is very important to get the rabbit eating immediately, to promote appropriate wearing of the existing teeth and to keep the gastrointestinal tract functioning properly.
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