3 dental disease what happens to the teeth by The All Ears Podcast

Dental disease- what happens to the teeth

Causes of dental disease: 1. Hereditary malocclusion • Only affects incisors • Known genetic problem • Caused by skull abnormalitiesusually 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

Causes of dental disease: 2. Trauma • Usually result of fall, being trodden on or pulling at cage bars • Fractured jaws may present as sudden anorexia and incisor malocclusion

Normal

• Accounts 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

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

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

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

PSADD: Early abnormalities

Innervation of teeth

• Palpable swellings along ventral border of mandible • Horizontal ridges on upper incisors • Uneven wear of cheek teeth

Illustration from:

Nerve supply to mandibular cheek teeth is encased in a bony canal

Atlas d'anatomie du lapin. (Barone, R and others,1973) Frances Harcourt‐Brown BVSc FRCVS, RCVS Recognised Specialist in Rabbit Medicine and Surgery

Apical elongation is first change to take place. Frances Harcourt‐Brown BVSc FRCVS, RCVS Recognised Specialist in Rabbit Medicine and Surgery

Apical elongation and reluctance to eat hay

Path of the tear duct (nasolacrimal duct)

• Elongated roots impinge on nerves and cause pain when chewing hard foods. • So- not eating hay is result not cause of dental disease Not wanting to eat hay is first sign of problems

Normal

Apical elongation

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

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?

Apical elongation and runny eyes

• 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?

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

Next changes: Alterations in shape and position of the teeth • Alveolar bone loss leads to widening of periodontal space

Malocclusion develops Normal

• Teeth loosen so position within socket can change

Early

Result of changes in shape and position of teeth

• Shape of teeth affected by chewing forces on loose teeth supported by weakened bone

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

Overgrown

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

Further progression of PSADD

Cheek teeth malocclusion Spurs develop on cheek teeth

Wild rabbit

Stage where there are the most obvious clinical signs due to soft tissue damage

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

Cheek teeth malocclusion

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

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

Clinical improvement

Crown breakage

• Rabbits condition may start to improve- no longer needs dentistry may be interpreted as response to treatment

• Usually just below gum

• Teeth remain as non-growing but functional ‘stumps’

• Not malocclusion

• Crown is loose which makes eating uncomfortable • Owners may think dental problems have started again

Changes are not synchronised in all teeth

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

Eventual tooth loss

End-stage dental disease

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

• 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 • • • • •

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

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 Normal

Endstage

Same rabbit

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 • ????

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

Duct is usually blocked at apex of upper incisor

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

Some cases will spontaneously resolve • Erosion of bone gives alternative drainage route • Signs can resolve if duct erodes into nose • Flushing can help

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

Flushing tear ducts

Sagitally sectioned skull

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

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

Easiest remedy

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

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 wear 2. Metabolic bone disease

Agreement that it is linked with incorrect diet Frances Harcourt‐Brown BVSc FRCVS, RCVS Recognised Specialist in Rabbit Medicine and Surgery

Problems with inadequate dental wear theory

Dental abscesses

Can be peri-apical or from puncture wounds

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

Proposed sequence of events

• 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

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

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

Normal

Calcium requirement is high in rabbits • Breed prolifically • Large litters • Mated as soon as they have give birth

Dental disease

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

Calcium demand for continually growing teeth

• 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 metabolism in rabbits

• 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

Efficient intestinal absorption • 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 Frances Harcourt‐Brown BVSc FRCVS, RCVS Recognised Specialist in Rabbit Medicine and Surgery

Muesli mixes

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

Calcium content of ingredients

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 • • • •

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 foodwhich 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

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%

Cause of dental problems Frances Harcourt‐Brown BVSc FRCVS, RCVS Recognised Specialist in Rabbit Medicine and Surgery

Food

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

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

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

For example

6 month old rabbit with congenital malocclusion

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

Normal Normal

Dental disease Dental disease

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

Options for incisor malocclusion 1. Clip 2. Burr or cut with power tools 3. Extract 4. Leave alone 5. (Euthanasia) Depends on reason for malocclusion and state of individual teeth

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

Radiography can help with decision making

Mature rabbit with advanced dental disease

Difficult to extract ankylosed teeth If in doubt, burr or cut and reassess later Frances Harcourt‐Brown BVSc FRCVS, RCVS Recognised Specialist in Rabbit Medicine and Surgery

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

Treatment of cheek teeth malocclusion

? Remove crowns or spurs

Normal

Dental disease

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

• Reduce height of crowns with burrsNOT clippers • Appropriate treatment if crowns are believed to be long

• Just remove spurscan 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

Trimming teeth with molar cutters

Burring v clipping cheek teeth

• ? Old fashioned • Not as scary as using power tools • Reputed to shatter teeth (it doesn’t) • Can’t reshape teeth (can’t

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

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

Shortening teeth can cause abscesses

Excessive burring can cause problems Abscesses from burring

Abscess from incisor clipping

Normal

• Either instrument can cause harm if used badly • Exposure of pulp cavity can allow infection to track down tooth

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

•

Burrs can also slip off teeth and cause soft tissue damage

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

Treatment of advanced dental disease • 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

• Not total extraction

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

The end

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