Causes of dental disease: 1. Hereditary malocclusion. Causes of dental disease: 2. Trauma

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1 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 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 Accounts for <2% of cases of dental disease in my practice 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 1

2 Innervation of teeth PSADD: Early abnormalities Palpable swellings along ventral border of mandible Horizontal ridges on upper incisors Uneven wear of cheek 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 Apical elongation is first change to take place. 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 Path of the tear duct (nasolacrimal duct) Not wanting to eat hay is first sign of problems Apical elongation Nasal section of the nasolacrimal duct Proximity of nasolacrimal duct with upper incisor 2

3 Apical elongation and runny eyes 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? Elongation of the apex of the upper incisor blocks the tear duct so tears flow down the face Next changes: Alterations in shape and position of the teeth 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 Malocclusion develops Early Result of changes in shape and position of teeth Moderate Overgrown Cheek teeth malocclusion Further progression of PSADD Spurs develop on cheek teeth Wild rabbit Stage where there are the most obvious clinical signs due to soft tissue damage Cheek teeth malocclusion Pulp cavities close The teeth stop growing Sensation is lost 3

4 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 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 Rabbits with end-stage dental disease Obesity and 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 Endstage Same rabbit Bananas Apples Grated carrot Softened excel Toast Digestive biscuits???? 4

5 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 5

6 Easiest remedy Dental abscesses Picture courtesy of Richard Saunders From BSAVA Manual of Rabbit, Surgery, Dentistry and Imaging 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 wear 2. 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 6

7 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 Calcium requirement is high in rabbits 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 Dental disease 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 7

8 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 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 foodwhich 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 8

9 Current thinking Why does it matter what cause is? 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 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 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 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 For example Radiography can help with decision making 6 month old rabbit with congenital malocclusion Mature rabbit with advanced dental disease Difficult to extract ankylosed teeth If in doubt, burr or cut and reassess later 9

10 Treatment of cheek teeth malocclusion? Remove crowns or spurs Controversial Dental disease Reduce height of crowns with burrs- NOT 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 Burring v clipping cheek teeth Trimming teeth with molar cutters Video courtesy of Evert-Jan De Boer Video courtesy of Frances Harcourt-Brown? 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 Shortening teeth can cause abscesses Excessive burring can cause problems Abscess from incisor clipping Abscesses from burring Either instrument can cause harm if used badly Exposure of pulp cavity can allow infection to track down tooth Burrs can also slip off teeth and cause soft tissue damage 10

11 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 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 The end 11