Dental problems are the most common cause of disease in pet rabbits in the UK. Most problems are caused due to an improper diet causing tooth overgrowth. Many problems can be resolved by dental treatment under general anaesthetic, however repeat procedures may be necessary to keep the teeth correctly aligned and the rabbit’s mouth comfortable and pain-free.
This article will give pet owners a greater understanding of rabbit dental disease, including causes of dental problems, clinical signs and treatment options.
Introduction to rabbit dental health
Rabbits belong to the order of animals called lagomorphs. They have two large upper and two lower incisor teeth with two much smaller “peg” teeth sitting just behind the upper incisors. The incisors are used to graze longer particles of food such as grass stems which are then passed back in the mouth towards the cheek teeth. Rabbits have six upper and four lower premolars and six upper and lower molars which are collectively referred to as the cheek teeth. The cheek teeth are used to break down fibrous components of food in a characteristic side-to-side grinding and slicing action. The roots of lagomorphs’ teeth grow continuously throughout an animal’s life, and the crown of the tooth which is visible above the gum line is constantly worn down by the chewing motions during feeding.
Diet and dental disorders
A rabbit’s natural diet would be composed mainly of grasses and the younger stems of shrubs. These are very fibrous food sources which require much chewing before being swallowed. Many captive rabbit diets contain a mixture of seeds, fruits and leaves which provide a good source of energy for the rabbit in the form of sugar. Unfortunately these foods require much less chewing and therefore cannot always grind down the teeth at the same rate as the tooth roots are growing. When the chewing surfaces of the upper and lower teeth no longer grind against each other due to misalignment, this is referred to as dental malocclusion. Rabbits need lots of fibre in their diet to keep the stomach and intestines moving digested food along at a healthy rate. Rabbits produce both hard and soft droppings. The soft droppings are referred to as caecotrophes and a healthy rabbit should eat these droppings which contain many nutrients only absorbed from the intestines by digesting the food a second time. Commercial rabbit foods can occasionally cause problems such as dental disorders, obesity and gastrointestinal disease if used inappropriately without a good source of fibre such as hay or grass also available.
Malocclusion of the incisors
The incisor teeth can become maloccluded (misaligned), and this is thought to happen in one of the following ways (Harcourt-Brown, 1995):
1) Trauma to the teeth such as trimming the teeth with nail clippers or by chewing on wire in the hutch
2) Infection of the roots of the incisor teeth
3) Trauma to the head
4) Previous misalignment of the cheek teeth leading to malocclusion of the incisor teeth
5) Congenital i.e. misalignment since birth
Malocclusion of the cheek teeth
When a rabbit’s cheek teeth are not worn down at the same rate as the root is growing, the teeth try and relieve the pressure by either continuing to grow at an angle in the mouth or pressing against other structures within the jaw. When cheek teeth start to grow at an angle, the upper and lower teeth are not longer fully interlocked when grinding down food particles. This is malocclusion and can lead to sharp and painful points called spurs forming on the outer surface of the teeth which are no longer b eing ground down by the opposing teeth. These can rub against the inside of the cheeks or against the tongue, causing irritation and injuries such as painful mouth ulcers. These spurs can also act as a lever during the grinding action of the jaws, causing teeth to loosen within their socket.
If the cheek teeth cannot continue growing into the mouth, they will start to invade the tissue surrounding them. The upper cheek teeth will press on the structures above the mouth such as the eye socket or the nasolacrimal duct, also referred to as the tear duct, which drains the watery secretions from the eye and deposits them just inside the nostril. The lower cheek teeth may start to press on the lower jaw bone and can be felt as bony lumps underneath the jaw.
One of the major problems with overgrown cheek teeth is the strain that is placed on the muscles involved with chewing actions. The overgrown teeth significantly restrict movement in the mouth and this lack of action can cause softening of the bones which form the jaw. The lack of movement subsequently prevents the rabbit from grinding down the surface of the teeth, therefore exacerbating the original problem.
The periodontal tissue refers to the structures which surround the teeth and hold them in place such as ligaments and bone. When there is dental disease, the periodontal tissue is placed under increased strain and may become inflamed or infected. Due to the continual growth of lagomorphs’ teeth, the pulp cavity in the centre of the tooth remains open, increasing the likelihood of infection.
Clinical signs of dental disease in rabbits
· Weight loss
· Decreased food intake, especially the more fibrous components of the diet (such as hay or grass)
· Reduced number and size of droppings
· Difficulty chewing
· Halitosis (bad breath)
· Overflow of tears onto the face (epiphora) due to pressure on the eye socket or nasolacrimal duct
· Excessive salivation (ptyalism)
· Nasal discharge or noisy breathing
· Matted coat
· “Clagged vent” – a build up of soft faeces around the anus
· Constant washing of the face
· Swellings around the head and neck
Diagnosis of dental disease
1. Clinical signs are usually a good indicator of dental disease in rabbits, however there are some other very serious diseases which appear similar in presentation (see “Gut stasis” below)
2. Some vets will attempt to look in the rabbit’s mouth whilst conscious using an otoscope; a device commonly used to examine the ear canal in animals and humans. This can highlight problems such as hairballs (trichobezoars) in the mouth, or severe ulceration and damage to the cheeks or tongue. Some rabbits object to having the otoscope placed in their mouth, particularly if painful, therefore the temperament of the rabbit; severity of the condition and the availability of trained personnel to handle the rabbit must be taken into account when deciding whether to perform this procedure. Vets sometimes find that turning a rabbit on its back may calm it enough to examine the mouth more thoroughly.
3. In order to perform a more detailed examination of the mouth, the rabbit may be anaesthetised and the mouth held open with specialised equipment in order to get a clearer image.
4. X-rays (radiographs) can be used to check the alignment of the teeth, as well as to look for tooth root infections and a decrease in bone density or fractures.
Treatment of dental disease
It is very important that your rabbit receives the correct treatment for dental disease. Overgrown teeth and spurs can be very painful for your rabbit and they may avoid eating certain foods due to the discomfort. Your vet can recommend the best treatment for your rabbit. This can range from preventative action with the correct diet to dental surgery to extract teeth or correct the alignment of teeth within the mouth.
The aim of dental treatment is to preserve the tooth and prevent tooth overgrowth by restoring natural alignment. Some rabbits may need tooth extractions, and many rabbits need repeat dental treatments throughout their life to control and prevent return of malocclusion. Rabbits need to be placed under general anaesthesia to carry out most dental procedures.
The main treatment of incisor overgrowth is to saw the excess tooth away using specialised dental equipment. In some cases, your vet may decide to extract the incisor teeth at an early stage to preserve the correct alignment of the more important cheek teeth. This is less likely to be required if the cheek teeth are already maloccluded as removing the incisor teeth will have little impact on already misaligned cheek teeth. Occasionally it is not possible to remove the complete tooth root and therefore the tooth may grow back at a later stage.
Cheek teeth malocclusion is frequently managed with monthly or six-weekly prophylactic (preventative) dental treatments. The cheek teeth overgrowths will be worn down using specialised dental equipment and any sharp spurs removed. This will make the rabbit more comfortable and enable normal chewing motions.
Whilst under general anaesthetic, your rabbits may require some of the following: analgesics (pain relief), intravenous fluids and drugs to help keep the guts moving and healthy (prokinetics e.g. metaclopramide in the UK).
If your rabbit is suffering with discharge from the eyes, the tear ducts may need flushing by introducing a small length of tubing into the opening of the duct by the eyelid. The tear duct is then flushed with sterile saline and depending on the severity of the inflammation and infection; the rabbit may need antibiotic eye ointment to be applied at home.
Once your rabbit returns home after a dental operation, it is important to encourage them to eat. You may need to slice very thin strips of vegetables which your rabbit can easily chew and always provide a good quality source of fresh hay or grass. Some rabbits may require a specialised liquid diet which is easy for them to swallow for the first few days after surgery.
Your rabbit may also need a course of antibiotics and it is very important that the whole course is finished to avoid dental infection. Common antibiotics used in the UK include enrofloxacin (Baytril) drops or procaine penicillin and oxytetracycline injections. If there is a deep bone infection, your rabbit may need to stay on antibiotics for a long time, in severe, extreme cases for the rest of its life. There are few licensed drugs for rabbits so many medications are used “off-license” which means the drugs company responsible for producing the drug have not fully tested its effects in rabbits. This doesn’t necessarily mean the drugs are dangerous for your pet as most will have been used countless times in other rabbits with no side effects. Most vets will ask you to sign a form to say you understand that the medications used are unlicensed in rabbits and that you have given permission for their use.
Once your rabbit has suffered from dental problems, there is a high chance they will need repeat treatments in order to keep their teeth in the correct alignment and to control any sharp spurs or overgrowths. It is essential to maintain a careful watch on your rabbit for either return of their original signs of dental disease or for any of the signs listed above.
Rabbits frequently suffer from abscesses, particul arly in their lower jaw. It is very difficult to fully resolve these infections as the abscess usually invades deeply into the soft tissues and bone. The rabbit’s immune system will promote scarring around the site of the abscess to help prevent further spread of infection however this scarring can also hinder the antibiotics from reaching the site of infection.
Treatment of dental abscesses commonly involves surgically removing the infected tissue under general anaesthetic. Even with surgical treatment, nearly all rabbits will need a course of antibiotics to prevent the abscess from recurring. Some vets will perform a culture and sensitivity test on the bacteria present, which helps to determine which antibiotics will be effective against the bacteria in your rabbit’s mouth. These tests usually take a few days to process so your vet might start your rabbit on the most appropriate antibiotic in the situation and later change antibiotics depending on results of the culture and sensitivity test.
Prevention of overgrown teeth
The most effective way to prevent tooth overgrowth is to feed your rabbit a diet rich in hard, chewable food. Fresh hay or grass should be the main source of food although supplementary feeding with a complete rabbit food can provide a good source of energy and nutrients for your rabbit. Your vet should be able to recommend a good complete rabbit food for your pet and advise you on how much food to give your rabbit. Timothy hay is the best type of hay to feed your rabbit, and remember never to give rabbits lawn mower cuttings as a source of food. Some rabbits enjoy chewing on edible tree branches, but always make sure the branches come from either apple or pear trees as many trees can contain substances toxic to rabbits.
Gut stasis, or ileus, is a very serious condition in pet rabbits which, if not treated, can be fatal. Some of the symptoms of ileus can be similar to dental disease however if your rabbit either stops eating or passing faeces completely; has severe liquid faeces or starts to eat only paper/cardboard/wood etc. (known as “pica”) this may be a sign of ileus or gastric obstruction.
If your rabbit suffers from any of these signs, please call your vet as soon possible and they can advise you on whether you need to bring your rabbit to the practice immediately for emergency treatment or make an appointment to see your rabbit later that day. Your vet may want to stabilise your rabbit and investigate the problem further before the condition deteriorates.
Implications of having a rabbit with dental disease
Many rabbits will suffer from dental disease during their lifetime. It is the most commonly diagnosed problem in pet rabbits (Mullen, 2006). The cost of dental treatment can be high, and the fact that many rabbits will require repeated treatments needs to be taken into account when considering costs.
If an owner is willing to dedicate time every day to checking their rabbit for signs of dental disease and taking action to correct any problems early on in the stage of disease, many rabbits can live happily for years with dental problems. An educated, motivated owner is crucial in managing these cases and often prevention with a suitable diet and close monitoring is much easier than trying to cure the problem once it has started.