| 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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