Anyone that has a dog or cat probably knows that dental care is very important. Most companion animal veterinarians will explain to owners how necessary it is to have their pets teeth brushed periodically at home, and once plaque and tarter accumulate, the pet should undergo routine dental prophylaxis on a regular schedule (usually under general anesthesia, as it is difficult to get pets to cooperate to rinse and spit!) Have you ever wondered why you haven't been asked to brush your rabbit's teeth or have dentals cleanings performed?
This is because rabbits possess a completely different kind of tooth than of those belonging to cats and dogs. The teeth of dogs and cats, like those of their owners, start out with baby teeth, also called deciduous teeth (because the fall out). They are replaced by permanent teeth that should then last for the life of the pet or person. That is why dental care is so important as those teeth must last for the life of the pet.
With rabbits, the teeth continue to grow for the life of the pet, so they are constantly being worn down and the teeth are being renewed. This type of tooth is called open-rooted, meaning that it is continually growing. It is for this reason that the teeth do not need to be brushed.
Let's learn a bit about bunny oral anatomy so that we will be able to understand what is important about rabbit oral hygiene. On each side of the mouth, rabbits have two upper and one lower incisor, no canine teeth (the long pointy dog and cat teeth), three upper and two lower premolars and three upper and lower molars. Rabbit teeth are curved and the anterior incisors of both the upper and lower jaws are modified to form a chisel-like cutting organ. The incisors are permanently sharp from gnawing. Enamel is only present on the front surface of the teeth, and the back surface is composed of dentin, which is softer than enamel. For this reason, the front surface wears down more slowly.
There is a space where no teeth are present between the incisors and the cheek teeth. This area is called the diastema (Madonna has a diastema gap between her front teeth).
Malocclusion and overgrowth occurs most often with the front incisors, which can grow 10 to 12 centimeters per year throughout the rabbit's life. There is a second set of incisors, behind the upper front incisors, and these may also overgrow. The premolars and molars are called cheek teeth, and these may also overgrow from malocclusion.
The muscles of the jaw extend both forward and backward. The mandible is able to move forward, backward and vertically, but less so from side to side because of the unique anatomy of the temporomandibular joint (TMJ), which is longitudinally elongated and therefore restricts lateral movement.
Rabbit teeth and oral muscles are perfectly designed for consuming the necessary roughage that should constitute the bulk of the rabbit diet, hay. While wild rabbits prefer to seek out and eat tender shoots and succulent plant parts as the major portion of the diet, they are also highly adaptable to a high-roughage diet. I'm sure you have noticed that your pet rabbit spends a lot of time eating and chewing, and that is great for keeping the teeth properly worn down, as long as the rabbit's teeth are in proper alignment. Rabbits chew their food thoroughly with highly organized tongue movements and up to 120 jaw movements per minute. That's a lot of chewing!
Rabbits should not be offered unlimited pellets, even if they are the types of pellets that are lower in calcium (timothy hay or other lower calcium grass hays which are lower in calcium than alfalfa), as this tends to promote obesity and chronically soft stools. However, if pellets are restricted, this may lead to fur-pulling, barbering or gnawing at inappropriate items, such as carpeting, furniture, shoes, books or even electrical wires. Boredom and destructive behavior can be avoided by providing the rabbit with timothy hay, fresh grasses and appropriate vegetables. It is also a good idea to offer pet rabbits suitable items for chewing and gnawing, such as safe wood and chew toys designed for rabbits.
So, what can go wrong with rabbit teeth? The most common problem is tooth overgrowth from poor alignment, also called malocclusion. The causes of malocclusion are usually multifactorial, and can include infectious, genetic and traumatic causes. The chewing action of the rabbit is both vertical and horizontal which provides a grinding type of action that keeps the occlusal (the opposing surfaces of the teeth that meet normally) surfaces evenly worn. If the mandible (lower jaw) is too short or too narrow, this will result in the misalignment of the teeth. Once teeth are misaligned, they will no longer grind down correctly. Misalignment of a single tooth is often the result of an infection in a tooth root or from trauma to the tooth. If one tooth becomes misaligned, it can throw off the entire bite, or it might just affect the opposing tooth.
Malocclusion of the incisors is most common in the smaller or dwarf breeds of rabbit. It usually will be apparent early on, as the owner notices that the front teeth are overgrown. If this is not discovered in time, the rabbit with malocclusion may suffer from weight loss or more severe problems from the inability to consume adequate quantities of food. If a rabbit is unable to eat for any length of time, it may quickly develop a very serious condition called hepatic lipidosis.
Malocclusion may also occur in the cheek teeth (premolars or molars). Since these teeth are in the back of the mouth and very tricky to visualize, problems occurring in these teeth are more difficult to diagnose. The only abnormality that an owner of a rabbit with molar malocclusion may notice is weight loss or the inability to eat. A bright and healthy rabbit that appears interested in food and acts hungry but will not eat often will have molar malocclusion. Another sign of molar malocclusion is the rabbit that begins to eat food and then drops the food from its mouth. The cheek teeth that overgrow often have very painful points that pinch or abrade the cheek tissue or tongue.
Whenever a rabbit is presented for a physical examination, this should always include a thorough oral examination, including looking at the incisors and cheek teeth. While it is quite simple for a veterinarian (and owner) to visualize the incisors, as they are front and center, special tools are required to get a good look at the cheek teeth. An otoscope, small vaginal speculum or fiber-optics endoscope may be necessary to clearly visualize the back teeth because the mouth of the rabbit does not open very wide. Some rabbits do not tolerate this examination without struggling, and these patients may require sedation or general anesthesia in order to visualize the cheek teeth.
If teeth are overgrowing due to malocclusion, it is possible to trim long incisors with a dental drill or side-nosed cutters. It is best to not trim teeth with nail trimmers, which is likely to split the tooth longitudinally. If a tooth splits, this predisposed it to infection of the root. Nail trimmers may also leave a cut tooth with ragged surfaces. Because the teeth of the rabbit aren't structured like yours or mine, cutting them is not painful, as long as the tooth isn't split down to the root. It is possible to cut the incisors of most rabbits without any sedation or anesthesia. Using side-nosed cutters, it might be possible to teach owners how to trim teeth at home, although they need to be aware of the risk of splitting a tooth. This would need to be something that is discussed and agreed upon by both the owner and rabbit veterinarian.
The best way to trim incisors is with the use of a high-speed dental drill, which is performed in a veterinary hospital. However, this does require sedation or general anesthesia, due to the risk of injuring the tongue or fragile oral tissue, should the patient move during the procedure. Either way the teeth are trimmed, it is usually necessary to trim the incisors every four to eight weeks.
Malocclusion of the cheek teeth, once diagnosed, requires tranquilization or general anesthesia for corrective dentistry. The sharp overgrown edges can and do cause very painful punctures and lacerations of the tongue or inside of the cheek (also called buccal mucosa). A dental drill or tool used for cutting bone is necessary to correct overgrown cheek teeth. Trimming the teeth properly can be very difficult, working in the small oral cavity, while trying to prevent injury to the gums, tongue or mucosa. As with overgrown incisors, the cheek teeth that are overgrowing must be trimmed periodically, usually ever four to eight weeks.
While it is possible to trim overgrown teeth periodically, which can be very stressful to the rabbit, it is recommended that the maloccluded teeth be permanently extracted. It is a good idea to first radiograph (x-ray) the jaws and teeth to uncover any abnormalities prior to extracting teeth. If malocclusion has occurred as a result of a tooth root abscess, antibiotics should be administered prior to performing the procedure. Teeth are extracted under general anesthesia. Lower incisors are removed first, then the apposing top incisor is also removed, as if one is left, with no tooth to grind against it, it will surely overgrow. Cheek teeth are much more difficult to extract.
If a portion of a tooth breaks off, leaving a broken piece of tooth root in the jaw, this can regenerate a tooth. It often takes about six to eight weeks for a new tooth to erupt. If this occurs, removal can again be attempted once the tooth has grown to a size making it suitable for excision. Sometimes, if the root is damaged, the tooth may grow back at an unusual angle or in an unusual shape.
After surgery to extract teeth, open sockets are flushed with antiseptic, or the roots may be cultured if bacterial infection is suspected. Antibiotics are usually administered after extraction, and this may be based on the results of bacterial culture and sensitivity. If there is infection in the tooth root or there is an abscess, antibiotics may need to be administered for six to eight weeks after excision. Since this can be quite painful, it is usual for pain medication to be prescribed for up to five days after the procedure.
Abscesses may occur in the teeth, most commonly in the cheek teeth. These infections may occur for several reasons. If a tooth has split longitudinally, food or bacteria may invade into the fractured tooth. Infections may also occur if food becomes impacted alongside a tooth, allowing bacteria to grow along the gum line. Bacterial contamination of oral lesions can result in a tooth abscess. Abscesses often result in the socket around the tooth becoming infected with bacteria, and can progress to osteomyelitis, a secondary infection of the bone, which is very dangerous and difficult to treat.
Regardless of the cause, tooth abscesses are always a very serious medical condition. One or multiple teeth may be affected and the secondary infection of the bones of the jaw is extremely serious. Because a cure is not likely, the prognosis is guarded and owners must be aware that treatment will require a significant investment in their time, money and emotions. Treatment involves aggressive removal of infected tissue, and extraction of the affected tooth or teeth. Depending on the bacteria involved and the extent of the infection, the open sockets may be irrigated daily, or the area may be packed with antibiotic-impregnated methylmethacrylate beads. Systemic antibiotics must be administered for weeks or longer, and this increases the risk of the rabbit developing gastrointestinal problems due to the killing off of "good" bacteria in the gut. Aggressive wound management and systemic antibiotics, or packing the sockets with antibiotic-impregnated beads may result in complete healing in some rabbits, and others will do well as long as they are being maintained on antibiotics. In other cases, the rabbit will continue to decline, fighting infection in the teeth and jaw for its lifetime, in spite of excellent care. In some cases, the rabbit veterinarian may elect to pack the sockets with calcium hydroxide, a dental preparation. This paste remains in the sockets for a week, then it is either replaced or the socket will be cleaned out and left open and then the wound is treated by irrigation.
For the healthy rabbit with good occlusion of the teeth, there is very little that the rabbit owner need do to in the way of oral hygiene. Make sure that you provide your rabbit with some hay, in addition to pellets, and also offer appropriate wood or other rabbit toys that it may chew on. Chewing helps to keep the teeth properly aligned and ground down. If you notice that your bunny chews on the cage wire or food bowls, it might be in need of something more appropriate to direct its chewing behavior to.
Examine your rabbit's teeth and oral cavity during your periodic grooming sessions and make note of any overgrown teeth, or abnormal bumps in the mouth area. Pay attention to your rabbit's eating habits and bring your bunny in to see your rabbit vet if you notice a change in food consumption or if you notice any slobbering, drooling or food falling out of the mouth. Make sure that you take your pet in for routine periodic examinations that include a thorough examination of the oral cavity and you will be doing all that you can to ensure good oral hygiene in your bunny.
Copyright © 2006 Margaret A. Wissman, D.V.M., D.A.B.V.P.
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