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by Frances Harcourt-Brown
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Frances Harcourt‐Brown BVSc FRCVS, RCVS Recognised Specialist in Rabbit Medicine and Surgery
Dental disease- what happens to the teeth
Frances Harcourt‐Brown BVSc FRCVS, RCVS Recognised Specialist in Rabbit Medicine and Surgery
Causes of dental disease:1. Hereditary malocclusion
• Only affects incisors• Known genetic problem• Caused by skull abnormalities-
usually shortened maxilla• More common in Dwarf breeds• Evident from an early age• Structure of teeth is good• Accounts for approximately 5%
of cases of dental disease in my practice
Frances Harcourt‐Brown BVSc FRCVS, RCVS Recognised Specialist in Rabbit Medicine and Surgery
• Usually result of fall, being trodden on or pulling at cage bars
• Fractured jaws may present as sudden anorexia and incisor malocclusion
• Accounts for <2% of cases of dental disease in my practice
Causes of dental disease:2. Trauma
Normal
Frances Harcourt‐Brown BVSc FRCVS, RCVS Recognised Specialist in Rabbit Medicine and Surgery
Causes of dental disease:3: Tumours
• Range of tumours• Odontomas linked with
advanced dental disease
• Account for <2% of cases of dental disease in my practice
Frances Harcourt‐Brown BVSc FRCVS, RCVS Recognised Specialist in Rabbit Medicine and Surgery
4:Progressive syndrome of acquired dental disease (PSADD)• Characterised by progressive
changes in shape, structure and position of the teeth
• Adult onset malocclusion is part of syndrome
• Doesn’t occur in wild rabbits or pet rabbits that eat a lot of hay and/or grass
• Seldom reported in lab rabbits • Accounts for <90% of cases of
dental disease in my practice
Frances Harcourt‐Brown BVSc FRCVS, RCVS Recognised Specialist in Rabbit Medicine and Surgery
Features of PSADD
• Thin bone• Loss of enamel on the teeth• Change in hardness of teeth• Apical elongation so roots
grow back through jaw• Change in shape of teeth so
they don’t meet properly• Crown loss• Jaw abscesses• Eye problems
Beginning
End
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Frances Harcourt‐Brown BVSc FRCVS, RCVS Recognised Specialist in Rabbit Medicine and Surgery
Innervation of teeth
Illustration from:
Atlas d'anatomie du lapin. (Barone, R and others,1973)
Nerve supply to mandibular cheek teeth is encased in a bony canal
Frances Harcourt‐Brown BVSc FRCVS, RCVS Recognised Specialist in Rabbit Medicine and Surgery
PSADD:Early abnormalities
Apical elongation is first change to take place.
• Palpable swellings along ventral border of mandible
• Horizontal ridges on upper incisors • Uneven wear of cheek teeth
Frances Harcourt‐Brown BVSc FRCVS, RCVS Recognised Specialist in Rabbit Medicine and Surgery
Apical elongation and reluctance to eat hay• Elongated roots impinge
on nerves and cause pain when chewing hard foods.
• So- not eating hay is result not cause of dental disease
Normal Apical elongation
Not wanting to eat hay is first sign of problems
Frances Harcourt‐Brown BVSc FRCVS, RCVS Recognised Specialist in Rabbit Medicine and Surgery
Path of the tear duct (nasolacrimal duct)
Frances Harcourt‐Brown BVSc FRCVS, RCVS Recognised Specialist in Rabbit Medicine and Surgery
Nasal section of the nasolacrimal duct
Frances Harcourt‐Brown BVSc FRCVS, RCVS Recognised Specialist in Rabbit Medicine and Surgery
Proximity of nasolacrimal duct with upper incisor
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Frances Harcourt‐Brown BVSc FRCVS, RCVS Recognised Specialist in Rabbit Medicine and Surgery
Apical elongation and runny eyes
Elongation of the apex of the upper incisor blocks the tear duct so tears flow down the face
Frances Harcourt‐Brown BVSc FRCVS, RCVS Recognised Specialist in Rabbit Medicine and Surgery
How can you tell if a rabbit has good teeth without looking in its mouth?
• Does it eat hay?• Is the enamel on incisors smooth and
shiny?• Are the eyes clear from any discharge?• Are there any lumps along the
mandible?
Frances Harcourt‐Brown BVSc FRCVS, RCVS Recognised Specialist in Rabbit Medicine and Surgery
• Alveolar bone loss leads to widening of periodontal space
• Teeth loosen so position within socket can change
• Shape of teeth affected by chewing forces on loose teeth supported by weakened bone
Next changes: Alterations in shape and position of the teeth
Frances Harcourt‐Brown BVSc FRCVS, RCVS Recognised Specialist in Rabbit Medicine and Surgery
Normal Early
Moderate Overgrown
Malocclusion develops
Result of changes in shape and position of teeth
Frances Harcourt‐Brown BVSc FRCVS, RCVS Recognised Specialist in Rabbit Medicine and Surgery
Cheek teeth malocclusion
Stage where there are the most obvious clinical signs due to soft tissue damage
Wild rabbit Cheek teeth malocclusion
Spurs develop on cheek teeth
Frances Harcourt‐Brown BVSc FRCVS, RCVS Recognised Specialist in Rabbit Medicine and Surgery
• Pulp cavities close• The teeth stop growing• Sensation is lost
Further progression of PSADD
4
Frances Harcourt‐Brown BVSc FRCVS, RCVS Recognised Specialist in Rabbit Medicine and Surgery
Clinical improvement
• Rabbits condition may start to improve- no longer needs dentistry may be interpreted as response to treatment
• Teeth remain as non-growing but functional ‘stumps’
Changes are not synchronised in all teeth
Frances Harcourt‐Brown BVSc FRCVS, RCVS Recognised Specialist in Rabbit Medicine and Surgery
Crown breakage
• Usually just below gum• Crown is loose which
makes eating uncomfortable
• Not malocclusion• Owners may think dental
problems have started again
Frances Harcourt‐Brown BVSc FRCVS, RCVS Recognised Specialist in Rabbit Medicine and Surgery
Eventual tooth loss
• Disintegration/breakage of crowns• Resorption of roots• Or dystrophic calcification and ankylosis
Frances Harcourt‐Brown BVSc FRCVS, RCVS Recognised Specialist in Rabbit Medicine and Surgery
End-stage dental disease
• Few or no functional teeth• Thin bone• May be calcification which affects bone and teeth so they are indistinguishable
• Benign tooth tumours can occur
Frances Harcourt‐Brown BVSc FRCVS, RCVS Recognised Specialist in Rabbit Medicine and Surgery
Rabbits with end-stage dental disease
• Endstage means endpoint of dental disease
• Not end of rabbit• Can live on soft food • Often high calorie • Rabbits can become obese
with few signs of dental disease
Same rabbit
Normal
Endstage
Frances Harcourt‐Brown BVSc FRCVS, RCVS Recognised Specialist in Rabbit Medicine and Surgery
Obesity and dental disease
• Bananas• Apples• Grated carrot• Softened excel• Toast• Digestive biscuits• ???? Normal
5
Frances Harcourt‐Brown BVSc FRCVS, RCVS Recognised Specialist in Rabbit Medicine and Surgery
Complications of dental disease
• Abscesses• Eye infections• Can occur at any stage of dental disease• More common in later stages
Frances Harcourt‐Brown BVSc FRCVS, RCVS Recognised Specialist in Rabbit Medicine and Surgery
Dacryocystitis
• Infection of lacrimal sac• Eyelids glued together• Pus in contact with surface of eye
• Corneal lesions are very painful
• Usually need local or even general anaesthesia to see what is happening
Frances Harcourt‐Brown BVSc FRCVS, RCVS Recognised Specialist in Rabbit Medicine and Surgery
Duct is usually blocked at apex of upper incisor
Frances Harcourt‐Brown BVSc FRCVS, RCVS Recognised Specialist in Rabbit Medicine and Surgery
Some cases will spontaneously resolve
• Erosion of bone gives alternative drainage route
• Signs can resolve if duct erodes into nose
• Flushing can help
Sagitally sectioned skull
Frances Harcourt‐Brown BVSc FRCVS, RCVS Recognised Specialist in Rabbit Medicine and Surgery
Flushing tear ducts
Frances Harcourt‐Brown BVSc FRCVS, RCVS Recognised Specialist in Rabbit Medicine and Surgery
Additional treatment
• May need to clip fur and treat skin on face
• Can use eye ointment for skin and eye
• Not easy to cure every case• Recurrent• Easiest solution is to provide
a bonded companion can help keep face clean
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Frances Harcourt‐Brown BVSc FRCVS, RCVS Recognised Specialist in Rabbit Medicine and Surgery
Easiest remedy
Picture courtesy of Richard SaundersFrom BSAVA Manual of Rabbit, Surgery, Dentistry and Imaging
Frances Harcourt‐Brown BVSc FRCVS, RCVS Recognised Specialist in Rabbit Medicine and Surgery
Dental abscesses
Can be peri-apical or from puncture wounds
Frances Harcourt‐Brown BVSc FRCVS, RCVS Recognised Specialist in Rabbit Medicine and Surgery
Cause of PSADD
Many ideas: TMJ abnormalities, pulling at cage bars, genetics, infection etc.
Two main theories are:1. Inadequate dental wear2. Metabolic bone disease
Agreement that it is linked with incorrect diet
Frances Harcourt‐Brown BVSc FRCVS, RCVS Recognised Specialist in Rabbit Medicine and Surgery
‘Inadequate dental wear'
• Idea is that teeth are not worn down and become too long
• Pressure between upper and lower teeth arrest growth
• Eventually causes negative growth (intrusion) so apices grow back through jaw
Frances Harcourt‐Brown BVSc FRCVS, RCVS Recognised Specialist in Rabbit Medicine and Surgery
Problems with inadequate dental wear theory • No evidence
• Visibly thin bone in affected rabbits
• Doesn’t account for loss of enamel
• Apical elongation is the first change to take place
• Occurs in teeth with no resting occlusal pressure
• Rabbits can wear teeth down in absence of food
Frances Harcourt‐Brown BVSc FRCVS, RCVS Recognised Specialist in Rabbit Medicine and Surgery
Proposed sequence of events
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Frances Harcourt‐Brown BVSc FRCVS, RCVS Recognised Specialist in Rabbit Medicine and Surgery
Burgess poster
Frances Harcourt‐Brown BVSc FRCVS, RCVS Recognised Specialist in Rabbit Medicine and Surgery
Metabolic bone disease theory
• Insufficient dietary calcium results in weak teeth and bones
• Not enough bone to support the teeth
• Not enough calcium to support continual growth of new dental tissue
• Vitamin D deficiency and Ca:P imbalances can make it worse
Frances Harcourt‐Brown BVSc FRCVS, RCVS Recognised Specialist in Rabbit Medicine and Surgery
Metabolic bone disease theory
Dental disease
Normal• Insufficient dietary calcium results in weak teeth and bones
• Not enough bone to support the teeth
• Not enough calcium to support continual growth of new dental tissue
• Vitamin D deficiency and Ca:P imbalances can make it worse
Frances Harcourt‐Brown BVSc FRCVS, RCVS Recognised Specialist in Rabbit Medicine and Surgery
Calcium requirement is high in rabbits
• Breed prolifically
• Large litters
• Mated as soon as they have give birth
• Can be pregnant and lactating at same time
• Rabbit milk has 3-5 times amount of calcium than cow’s milk
Frances Harcourt‐Brown BVSc FRCVS, RCVS Recognised Specialist in Rabbit Medicine and Surgery
Calcium demand for continually growing teeth• Rate of tooth growth is about 2mm per week
• 28 teeth so 28x2= ~5cm new tooth each week
• Requires large amount of calcium (and phosphorus)
Frances Harcourt‐Brown BVSc FRCVS, RCVS Recognised Specialist in Rabbit Medicine and Surgery
Calcium metabolism in rabbits
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Frances Harcourt‐Brown BVSc FRCVS, RCVS Recognised Specialist in Rabbit Medicine and Surgery
• In rabbits (? and many other herbivores) passive diffusion is main mechanism of calcium uptake
• Amount absorbed depends on how much is in gut rather than how much is needed
• Way of meeting high calcium demand
• Do have a vitamin D requirement as well
Efficient intestinal absorption
Frances Harcourt‐Brown BVSc FRCVS, RCVS Recognised Specialist in Rabbit Medicine and Surgery
Effects of husbandry
• Vitamin D increases calcium absorption from gut
• Important if calcium deficiency is present
• Vitamin D has many other effects• Can overdose with supplements• Easier to allow rabbit to lie in sun• Or make sure it has a balanced
diet
Frances Harcourt‐Brown BVSc FRCVS, RCVS Recognised Specialist in Rabbit Medicine and Surgery
Muesli mixes
• Cheap, convenient and available• Well marketed and advertised• Formulated from data tables• Analysis of whole mix should be
balanced• Analysis of individual ingredients
isn’t• Vitamin and mineral supplement
added to pellet or extrusions
Cause of dental problems
Frances Harcourt‐Brown BVSc FRCVS, RCVS Recognised Specialist in Rabbit Medicine and Surgery
Calcium content of ingredients
Food Calcium (Dry matter analysis)
Alfalfa 1.5%
Barley 0.07%
Beans 0.14%`
Pellets/ extrusions ???? (0.5‐1%)
Maize (sweetcorn) 0.04%
Oats 0.03%
Peas 0.12%
Wheat 0.16%
Calcium requirement for optimum bone density 0.6‐1%
Frances Harcourt‐Brown BVSc FRCVS, RCVS Recognised Specialist in Rabbit Medicine and Surgery
Selective feeding
• Rabbits select out favourite ingredients such as peas and maize
• Owners like to leave a full bowl with rabbit all the time
• Throw away discarded food-which is often part with calcium in it and leave rabbit with calcium and vitamin D deficient D diet
Frances Harcourt‐Brown BVSc FRCVS, RCVS Recognised Specialist in Rabbit Medicine and Surgery
Weaning rabbits on to muesli mixes
• Animals are most susceptible to MBD when they are growing
• Weaning rabbits on to muesli mixes means that dental problems may start before rabbit goes to new home
• Dominant siblings are most at risk
9
Frances Harcourt‐Brown BVSc FRCVS, RCVS Recognised Specialist in Rabbit Medicine and Surgery
Current thinking
• PSADD is probably a mixture of weakened bone and chewing forces
• Definitely linked with muesli mixes• Less common in rabbits that eat a lot of hay/grass• ? Less common than 10 years ago
Frances Harcourt‐Brown BVSc FRCVS, RCVS Recognised Specialist in Rabbit Medicine and Surgery
Why does it matter what cause is?
• Doesn’t matter when it comes to prevention- no muesli mixes and plenty of hay/veg, grass etc
• Important when it comes to treatment
• No need to shorten crowns to ‘take pressure off roots’ if it is due to MBD
• Just accept that affected rabbits can’t eat hay and normal occlusion will never be restored
Dental disease
NormalNormal
Dental disease
Frances Harcourt‐Brown BVSc FRCVS, RCVS Recognised Specialist in Rabbit Medicine and Surgery
Treatment of dental disease
• Every case is different• No easy rules to fix every
case• All vets are different• General anaesthesia is
needed to look at cheek teeth properly
• Radiography can help decision making
Frances Harcourt‐Brown BVSc FRCVS, RCVS Recognised Specialist in Rabbit Medicine and Surgery
Options for incisor malocclusion1. Clip2. Burr or cut with power
tools3. Extract4. Leave alone5. (Euthanasia)Depends on reason for malocclusion and state of individual teeth
Frances Harcourt‐Brown BVSc FRCVS, RCVS Recognised Specialist in Rabbit Medicine and Surgery
For example
6 month old rabbit with congenital malocclusion
Mature rabbit with advanced dental disease
Frances Harcourt‐Brown BVSc FRCVS, RCVS Recognised Specialist in Rabbit Medicine and Surgery
Radiography can help with decision making
Difficult to extract ankylosed teethIf in doubt, burr or cut and reassess later
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Frances Harcourt‐Brown BVSc FRCVS, RCVS Recognised Specialist in Rabbit Medicine and Surgery
Treatment of cheek teeth malocclusion
Controversial
Normal
Dental disease
Frances Harcourt‐Brown BVSc FRCVS, RCVS Recognised Specialist in Rabbit Medicine and Surgery
? Remove crowns or spurs
• Reduce height of crowns with burrs-NOT clippers
• Appropriate treatment if crowns are believed to be long
• Just remove spurs-can be done with burrs or molar ‘cutters’
• Appropriate if teeth are believed to be misshapen or mialigned
Frances Harcourt‐Brown BVSc FRCVS, RCVS Recognised Specialist in Rabbit Medicine and Surgery
Burring v clipping cheek teeth
Video courtesy of Evert-Jan De Boer Video courtesy of
Frances Harcourt-Brown
Frances Harcourt‐Brown BVSc FRCVS, RCVS Recognised Specialist in Rabbit Medicine and Surgery
Trimming teeth with molar cutters
• ? Old fashioned• Not as scary as using power
tools• Reputed to shatter teeth (it
doesn’t) • Can’t reshape teeth (can’t
restore normal shape anyway)• Doesn’t take pressure off roots
(is there pressure?)• Leaves teeth in occlusion to
eat with• Safe
Frances Harcourt‐Brown BVSc FRCVS, RCVS Recognised Specialist in Rabbit Medicine and Surgery
Abscess from incisor clipping Normal
• Either instrument can cause harm if used badly• Exposure of pulp cavity can allow infection to
track down tooth
Shortening teeth can cause abscesses
Frances Harcourt‐Brown BVSc FRCVS, RCVS Recognised Specialist in Rabbit Medicine and Surgery
Excessive burring can cause problems
Abscesses from burring Normal
• Burrs can also slip off teeth and cause soft tissue damage
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Frances Harcourt‐Brown BVSc FRCVS, RCVS Recognised Specialist in Rabbit Medicine and Surgery
Pulling off loose crowns
• Usually just below gum• Crown is loose which makes
eating uncomfortable• Not malocclusion• Loose crown can be pulled
off• Won’t regrow• Not total extraction
Frances Harcourt‐Brown BVSc FRCVS, RCVS Recognised Specialist in Rabbit Medicine and Surgery
• Roots resorb or calcify• Crowns break off• Need to preserve any crowns
that are functional• Don’t need extensive dentistry• Check for loose crowns• Diet is important
Treatment of advanced dental disease
Frances Harcourt‐Brown BVSc FRCVS, RCVS Recognised Specialist in Rabbit Medicine and Surgery
The end