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Common Illnesses

Unmasking Rabbit Dental Disease
From Dr. Cathy Chan

Introduction:

Dental disease is a common presentation of domesticated rabbits. Many research studies estimate that up to 100% of all domesticated rabbits experience dental disease at various stages of their lives. It is interesting to note that in wild rabbits, dental disease is virtually unknown. This is important in understanding how acquired dental disease occurs in the house rabbit. There are 5 different stages of dental disease, ranging from normal dentition to severe disease which includes infection and destruction of the bones surrounding the teeth. Abscess formation and sepsis can occur in severe stages and these rabbits have extremely poor quality of life, not to mention the risk of sepsis and death.

Normal Dentition:

Rabbits have 28 teeth in total and this is often a surprise to rabbit owners. Because of the skull structure, only the front teeth are visible but disease can occur in both the front teeth and cheek teeth. Rabbits have 6 teeth in the front. There are 2 upper incisors and 2 lower incisors. There are 2 smaller teeth known as peg teeth which are located just behind the 2 upper incisors. These peg teeth differentiates rabbits and rodents. Rodents (rats, mice, guinea pigs) do not have these peg teeth.

The ‘cheek’ teeth are present at the back of the mouth. There are 6 teeth on each side of the upper dental arcade (3 pre-molars and 3 molars). There are 5 teeth on each side of the lower dental arcade (2 pre-molars and 3 molars). There is a wide space between the incisors and the cheek teeth. The cheek teeth lie from the level of the eye and are lined up to the back of the jaw.

All teeth should line up accordingly and oppose each other to create a shearing action. The rabbit uses the front incisor as a cutting tool and the cheek teeth act as a grinding surface for hard fibrous food material.

Rabbit teeth are known as elodont teeth. This means that the teeth grow continuously. Rabbit teeth grow approximately 2mm every day, therefore, constant shearing and shaping need to take place with a good abrasive diet. This occurs naturally during feeding and grazing.

When to Know your Rabbit has Dental Disease – Clinical Signs:

After understanding the location of all the 28 teeth, it is then easy to understand how dental disease can present in many different ways. Often, rabbits present with signs that you might think have no relation to the teeth, however due to the nature of rabbit teeth and the location, clinical signs are very varied. Not only are the top visible teeth continuously growing, tooth roots embedded in the gum and jaw can also grow in the opposite direction. Most owners often notice if the incisors teeth are diseased, however, diseased cheek teeth are often un-noticed.

Common presenting signs:
- Visibly fractured or crooked incisors
- Fur wrapped around incisor teeth.
- Presence of pus or discharge around teeth.
- Abscess formation (lumps palpated along lower jaw and along upper cheek area)
- Excessive salivation (wet chin, wet/saliva stained front paws, slobbers)
- Inappetance, reluctance to eat fibrous foods (hay etc.)
- Loss of body condition or body weight.
- Bad breath (from oral ulcers)
- Discharge from the nose
- Lack of grooming and a poor coat
- Excessive tearing and eye discharge
- Oral pain
- Lethargy

How does Dental Disease Occur?

There are certain breeds of rabbits that appear to develop dental disease more frequently. Dwarf lop eared breeds appear to have more dental disease than the more common domestic rabbit. Congenital incisor disease is very rare and majority of dental disease in the house rabbits is acquired (developed in the rabbits’ lifetime). Acquired dental disease is believed to occur from a variety of factors; however 2 mechanisms listed below are believed to be common factors.

The Importance of Diet –

Rabbits are selective feeders. If given choices, they often choose to eat what they are accustomed to eating, or the foods which taste better. Foods high in fibre often have poorer palatability. If given a choice of rabbit mixes, rabbits will often pick out foods high in carbohydrates, high in simple sugars and high in fat, these foods are often extremely low in fibre. Thus they will select foods like grain, nuts, and cereal over more fibrous foods like hay. Indigestible fibre and size of the food play a big role in aiding digestion and the abrasive nature aids in the maintenance of the continuously growing cheek teeth. Rabbit mixes and pellets should not be the main component of a rabbit’s daily diet. It is constantly being reinforced that a rabbit’s health and dentition is directly dependent on their diet. Unlimited hay should be provided and the house rabbit should be allowed to graze freely on the hay. A house rabbit’s main diet needs to be fresh leafy vegetables; one cup of fresh vegetables per kilogram twice daily. Pellets and mixes should be fed as treats and should only make up at most 5% of the rabbit’s diet. Diet is also related to the next mechanism of dental disease.

Metabolic Bone Disease -

Metabolic bone disease is a condition seen in almost all house rabbits with dental disease. This disease is similar to osteoporosis in humans where there is a lack of calcium in all bones. The actual disease is complex and many factors are involved. The three most important elements involved in metabolic bone disease is calcium, vitamin D and the parathyroid hormone. These 3 factors work closely to maintain the body’s calcium levels. Bone act as a storage point for calcium and phosphorus, when blood calcium is low, the body retrieves calcium from bone in order to keep blood calcium normal. It has been shown previously that dietary calcium needs to be no less than 0.44% in order for blood calcium to remain normal in rabbits. Rabbits eating a diet with less than 0.44% calcium (as in most rabbit mixes) will have low levels of calcium in the blood.

Exposure to sunlight is crucial for vitamin D synthesis. Vitamin D is essential for absorption of calcium in the gut. Animals with low blood calcium often compensate by producing vitamin D (with exposure to sunlight) and thus absorbing calcium in the gut. This is assisted by the parathyroid hormone.

Imagine a house rabbit that is restricted from sunlight and consumes a diet lacking in calcium (rabbit mix). This rabbit is then unable to maintain calcium levels and the body as a last resort, obtains calcium from bones. This causes bone to weaken. When bone surrounding and supporting teeth are weakened, dental disease arises. Teeth contain calcium as well and by a similar mechanism, teeth are also weakened.

Metabolic bone disease is probably the main reason house rabbits develop dental disease so frequently. Wild rabbits have adequate exposure to sunlight and have free access to grazing; hence acquired dental disease is not seen in wild rabbits at all.

Diagnosis of Dental Disease

When clinical signs are first noted, rabbits should be brought to a veterinarian immediately. Early treatment of dental disease is required in order to reduce pain and further deterioration. It is inhumane to leave dental disease untreated. Dental disease in the rabbit must be treated aggressively as it can lead to an extremely debilitated animal, not to mention a very painful pet.

Full assessment of the teeth requires a complete oral examination, not just of the front incisors but also of the back cheek teeth. This can be achieved in an animal with a light source and an otoscope. This method only allows visualisation of the crowns of the teeth.

Radiography (x-rays) of the skull under sedation is essential for a full dental assessment. This enables visualisation of all the tooth roots and the structures surrounding the teeth. It can aid in identification of diseased teeth which are involved in abscesses. It can also aid in determining the tooth root involved in eye infections and excessive tearing. Bone infections can also be identified.

Treatment of Dental Disease

There are several ways to treating dental disease in rabbits. Your veterinarian will provide appropriate treatment and advice for each animal. The following are guidelines and should not be applied to all cases. All cases have to be treated on an individual basis.

Diseased incisor teeth are often crooked and turned outwards. Trimming of incisors are often required to maintain the cutting surface. The roots of the incisors extend backwards, due to the location of the upper incisors, many rabbits with incisor disease will present first with excess tearing and eye infections. Frequent incisor trimming is needed but can cause more problems in the long term.

Trimming with dog and cat nail clippers or cutters with the rabbit awake can lead to many problems. The use of pet nail clippers for the trimming of teeth is not recommended. Even in the experienced dentist, small hairline fractures can occur during trimming which can worsen teeth, especially if the rabbit moves during trimming. If the pulp cavity is exposed and bleeding occurs, this pulp exposure can lead to infection within the tooth and subsequent abscess formation. Small fractures can extend deeper into the root which can destroy the area of tooth formation.

Ideally trimming should be performed in a lightly sedated or anaesthetized animal where the pre-molar and molar teeth can be examined at the same time. Spurs (sharp knife like edges) of the check teeth can also be filed at this time. The best tool for trimming of teeth is an electric dental burr. Severely diseased incisors should be extracted. Rabbits do not need incisors to grind or chew. Furthermore, if the incisors are diseased, they are no longer functioning. The presence of diseased incisors act as areas of infection and the sharp edges cause soft tissue damage and oral ulcers. Extractions of these incisors often result in the best quality of life for these rabbits.

Abscesses of the cheek teeth, present as lumps on the lower or upper jaw are more complicated diseases to treat. Surgical removal of the abscess as a whole is required. The abscess capsule needs to be removed as well. Once the abscess has been removed, the inciting tooth needs to be extracted, even if it is still firmly attached. Ideally the wound should be left open and filled with antibiotics. Common treatments of the open wound include antibiotic beads, antibiotic swabs/sponges, gels, ointments and manuka honey. Management of open wounds are difficult and time consuming, however it is likely the most appropriate treatment. Rabbits also require systemic antibiotics and pain relief is essential in all dental disease patients. It is crucial to keep all dental patients eating well through their disease course. These patients are at high risk of developing gut stasis due to the pain experienced from surgery or from dental disease.

Other clinical signs need to be treated appropriately by your veterinarian, however it is crucial to address the underlying issue of dental disease promptly as many rabbits may not present with obvious dental disease.

Conclusion

Given that dental disease is extremely common, it is likely that many rabbit owners will have to go through this with their beloved pets.

Preventative measures that can be undertaken:
- Providing a diet high in fibre.
- Unlimited access to grazing grass hay.
- Avoiding rabbit mixes, grain or cereal as a main diet
- Providing sunlight, unrestricted exercise and outdoor access for at least 4 hours a day
- Limiting rabbit pellets which are low in calcium
- Offering a wide variety of fresh vegetables
- Permitting grazing of abrasive weeds or natural grasses if available.

Remember that all advice should be undertaken after consultation with your veterinarian caring for your pet.

This article is not intended as a strict guideline or protocol as all cases are different.

Contributed by Cathy Chan BVSc (hons)

 

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