Many people think of rabbits as rodents, but they are grouped in the classification of animals called lagomorphs, a group that includes rabbits, hares, and pikas. Both rodents and lagomorphs have open-rooted teeth that continuously grow throughout life, a condition called aradicular hypsodont.
Rabbits and rodents both have easily visible front teeth (incisors) plus premolars and molars in the back of the mouth, called cheek teeth, for grinding and chewing. Unlike rodents, however, lagomorphs have two small, tube-shaped incisors, called peg teeth, which are located behind the large upper incisors.
Since the teeth continuously grow, they must also continuously be worn down, to prevent overgrown teeth and abnormal wear. The upper teeth must meet the lower teeth to allow for proper wearing of tooth surfaces, preventing overgrowth.
What types of dental problems might occur?
Malocclusion (imperfect positioning of the teeth when the jaws are closed) occurs routinely in many rabbits, causing improper tooth wear and overgrowth of the incisors, premolars or molars. For example, see the elongated lower right cheek teeth growing over the tongue in the image on the right.
Overgrown points or sharp spikes on the edges of teeth may cut and badly damage the tongue, cheeks, or gums. Overgrown lower cheek teeth may form a bridge over the tongue and cause tongue entrapment, as in the image to the right.
Overgrown molars may hit each other in the back of the mouth, preventing the front of the mouth from closing completely and causing incisors to not wear down properly, creating overgrowth or abnormal wear. As the molars continue to grow and are not worn down, they become impacted in the upper and lower jaws, like impacted wisdom teeth in people. All of this can lead to pain when chewing, the development of sores and/or abscesses in the mouth, difficulty eating, drooling, pawing at the mouth, problems grooming, and weight loss.
Misshapen incisors and malocclusion of the incisors will sometimes cause the front teeth to protrude out of the mouth (see image to the right), grow at an angle to each other, curl back into the mouth, curl sideways, or take on other problematic positions.
Rabbit teeth normally grow at a rate of approximately 1 cm each month, and if incisors do not meet properly (unopposed incisor), they could grow as much as 1 mm per day.
Why do these teeth grow abnormally?
There are many causes of tooth elongation, malocclusion, and improper growth and wear rates. A significant contributing factor is a diet lacking enough roughage or fiber to promote normal tooth wear.
Wild rabbits grind down their teeth by chewing constantly on grass, roots, and ground cover. Pet rabbits may eat some hay, but they often eat a larger percentage of crumbly rabbit pellets that do not help wear down the teeth. Some pet rabbits do not eat hay at all. Although rabbit pellets may contain Timothy hay, it is not in a long strand form, which is necessary for proper cheek teeth grinding.
Malocclusion may also have a hereditary or congenital component, especially in dwarf or lop-eared rabbits. These breeds are overrepresented when it comes to dental disease in rabbits. We cannot prevent the hereditary cause of dental malformation, except by stopping breeder pairs that produce babies with bad teeth from breeding again. Teeth braces are not an option for rabbits.
There are also theories that indoor rabbits’ teeth form improperly due to a lack of calcium. Indoor rabbits are not exposed to ultraviolet light, which is required to form vitamin D in the skin, which in turn enables absorption of calcium from the diet. Therefore, genetics, environment, and diet can all contribute to dental disease.
What can be done about abnormal tooth growth in rabbits?
To minimize dental problems, feed your rabbit a diet that includes high-fiber hay, with smaller amounts of pellets and fresh produce, so that they chew their food properly and wear their teeth down as they eat. For adult rabbits, the recommendation is ¼ cup of Timothy-based rabbit pellets per 5 pounds of body weight, once a day, and free-choice Timothy hay, orchard grass or botanical hay every day. Never feed rabbits grains, seeds, or cookies.
Rabbits with dental problems need regular veterinary care. Skull X-rays are highly recommended to assess the positioning of all the teeth and potential tooth erosion or abscessation that cannot be seen with the naked eye. Overgrown incisors should be shortened by a veterinarian familiar with rabbits.
Dental examinations and teeth trimming should occur every 4-12 weeks, as the teeth continue growing. Using nail clippers or wire cutters is never recommended, as trimming teeth this way often fractures the teeth, which may cause eventual abscessation of the teeth or gums. Proper teeth trimming requires general anesthesia or injectable sedation, and a rotary tool to trim the abnormal sections of the affected teeth.
"Treating poorly aligned molar teeth can be challenging but is part of routine care."
Treating poorly aligned molar teeth can be challenging but is part of routine care. If a rabbit has recurrent dental problems, one long-term solution is to remove the affected upper and/or lower incisors or the affected cheek teeth to prevent the need for repeated teeth filing. This procedure may be simple or complex, depending on the number of teeth affected, their location in the mouth, and whether infection is present. Although teeth extraction sounds drastic, it is the best long-term solution if chronic overgrowth occurs, and is the only solution if teeth are infected and their roots are abscessed.
Following tooth filing or extractions, it is important to get the rabbit eating immediately, to promote appropriate wearing of the teeth and to keep the gastrointestinal tract functioning properly. If your rabbit is not eating, your veterinarian will teach you to syringe-feed a commercially available powdered formula mixed with water. In many cases, they will send home oral anti-inflammatory medications to help with pain and, if abscesses are noted, will prescribe antibiotics. Annual veterinary check-ups are crucial for all rabbits to identify any developing dental problems and prevent them from progressing.