3 dental disease what happens to the teeth

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Frances Harcourt‐Brown BVSc FRCVS, RCVS Recognised Specialist in Rabbit Medicine and Surgery

Dental disease- what happens to the teeth


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


• 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


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


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


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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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


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


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


Path of the tear duct (nasolacrimal duct)


Nasal section of the nasolacrimal duct


Proximity of nasolacrimal duct with upper incisor

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Apical elongation and runny eyes

Elongation of the apex of the upper incisor blocks the tear duct so tears flow down the face


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?


• 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


Normal Early

Moderate Overgrown

Malocclusion develops

Result of changes in shape and position of teeth


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


• Pulp cavities close• The teeth stop growing• Sensation is lost

Further progression of PSADD

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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


Crown breakage

• Usually just below gum• Crown is loose which

makes eating uncomfortable

• Not malocclusion• Owners may think dental

problems have started again


Eventual tooth loss

• Disintegration/breakage of crowns• Resorption of roots• Or dystrophic calcification and ankylosis


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


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


Obesity and dental disease

• Bananas• Apples• Grated carrot• Softened excel• Toast• Digestive biscuits• ???? Normal

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Complications of dental disease

• Abscesses• Eye infections• Can occur at any stage of dental disease• More common in later stages


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


Duct is usually blocked at apex of upper incisor


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


Flushing tear ducts


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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Easiest remedy

Picture courtesy of Richard SaundersFrom BSAVA Manual of Rabbit, Surgery, Dentistry and Imaging


Dental abscesses

Can be peri-apical or from puncture wounds


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


‘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


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


Proposed sequence of events

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Burgess poster


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


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


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


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)


Calcium metabolism in rabbits

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• 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


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


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


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%


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


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

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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


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


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


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


For example

6 month old rabbit with congenital malocclusion

Mature rabbit with advanced dental disease


Radiography can help with decision making

Difficult to extract ankylosed teethIf in doubt, burr or cut and reassess later

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Treatment of cheek teeth malocclusion

Controversial

Normal

Dental disease


? 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


Burring v clipping cheek teeth

Video courtesy of Evert-Jan De Boer Video courtesy of

Frances Harcourt-Brown


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


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


Excessive burring can cause problems

Abscesses from burring Normal

• Burrs can also slip off teeth and cause soft tissue damage

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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


• 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


The end

3 dental disease what happens to the teeth

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