1. Veterinary dental nursing procedures
TYPES OF DENTITION

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3. Function of teeth Defence Acquiring food Holding food
Picking up
Catching
Killing
Holding food
Breaking down food
Cutting (shearing)
Crushing (grinding)
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4. Evolution of teeth From skin From fish scales?
All vertebrates have evolved from toothed ancestors (except Agnatha)
PHYLOGENY OF THE TEETH
This is the evolutionary development of the teeth.
Smith (1960 ) stated that teeth are thought to be derived from modified denticles found on the scales of early fish. All vertebrates (except the Agnatha ) either possess teeth or have evolved from toothed ancestors.
Evolutionary trends in dentition may be classified into at least 6 characteristics :
tooth location
anchorage
number
form
number of replacement sets
cycles of replacement
LOCATION OF TEETH
The trend has been toward limitation of the area of tooth dispersal. In fish teeth are found on most palatal and jaw bones. In modern mammals the teeth are restricted to mandible, premaxialla and maxialla.
ANCHORAGE
In most vertebrates the teeth are directly anchored to the skeletal system.
Pleurodont where the teeth are attached along the lingual surface of the jaw, eg sharks.
Aerodont where the teeth are attached to the crest of the jaw.
Thecodont where the teeth are attached in a socket with a projecting crown.
NUMBER OF TEETH
Primitive vertebrates were polyodont and the evolutionary trend has been to oligodonty. Toothless vertebrates became toothless by either loss in number of teeth or by progressive reduction in the size of each tooth. For example, groups such as birds, turtles, and some anurans result from reduction in tooth size as evidenced by presence of teeth in the embyos of these groups.
Aphyodonty –no teeth erupt ,for example armadillos and anteaters.
TOOTH FORM
Homodonty –the primitive condition ,with teeth of a uniform, conical appearance.
Heterodonty – the appearance of 2 or more teeth types in a single individual. The teeth may be modified for crushing (bunodont ), grinding (selenodont, lophodont ), slashing (canine ), shearing ( secodont), poison conducting.
Most toothed non-mammalian vertebrates are essentially homodont, although crocodilians are heterodont to a degree . Mammals are the only fully heterodont vertebrates.
NUMBER OF TEETH RELACEMENT SETS
Polyphyodont – primitive vertebrates were characterised with continual replacement of teeth eg sharks
Oligophyodont – several sets of temporary teeth before a final set of permanent teeth eg crocodiles
Biphyodont – 2 sets of teeth eg cat /dogs/humans ( In all mammals molars are permanent teeth. Premolars may be deciduous )
Monophyodont – 1 set of teeth eg moles
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5. Shark teeth – new rows
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6. In the mammalian embryo
Bud forms in oral mucosa
First completely buried then resurfaces
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7. Evolutionary classifications
tooth location
anchorage
number
form
number of replacement sets
cycles of replacement
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8. Tooth location Fish Mammals on most jaw/palate bones
Premaxilla-Maxilla
Mandible
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9. Tooth location Side of jaw (pleurodont) Crest of jaw (aerodont)
eg sharks
Crest of jaw (aerodont)
Tooth socket (thecodont)
attached in a socket with a projecting crown
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10. Number of teeth Many (polyodont) – primitive vertebrates
Several (oligodont) – trends towards this. Toothless vertebrates became toothless by either loss in number of teeth or by progressive reduction in the size of each tooth. For example, groups such as birds, turtles, and some anurans result from reduction in tooth size as evidenced by presence of teeth in the embryos of these groups.
None (aphyodonty) – no teeth erupt, e.g. armadillos and anteaters.
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11. Tooth Variation Single shape (homodonty)
The primitive condition ,with teeth of a uniform, conical appearance
Most non-mammalian vertebrates (Crocodilians have some variation)
2 or More shapes (heterodonty)
The teeth may be modified for crushing (bunodont), grinding (selenodont, lophodont ), slashing (canine), shearing (secodont), poison conducting. Mammals
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12. No. of Sets of Teeth per Lifetime
Many
primitive vertebrates were characterised with continual replacement of teeth eg sharks (polyphyodont)
Several
several sets of temporary teeth before a final set of permanent teeth eg crocodiles (oligophyodont)
Two
eg cat /dogs/humans (In all mammals molars are by definition permanent teeth. Premolars may be deciduous) (biphyodont)
One
eg moles (monophyodont)
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13. How to make a tooth last For carnivores – short crown
brachydont shape
For herbivores – long crown
hypsodont shape
Either
Continual growth, or
Slow growth & slow eruption (horse)
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14. Closed & Open Roots
Closed Open
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15. Open & Closed Roots Open root = continued growth
Enamel extends all way into socket (elodont)
Closed root = ceased growth
Enamel extends only over crown
Closed slowly with continued eruption throughout life
Long crown but shortens as tooth worn down and erupts
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16. Closed Roots (e.g. cat, dog, man)
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17. Open Roots (rabbit)
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18. Replacement patterns Vertical Horizontal e.g. horse e.g. elephant
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19. Elephant
Horizontal replacement
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20. Horse
Vertical replacement
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21. Snakes 5888H - Veterinary Dental Nursing
CONSTRICTOR SNAKES e.g. boas (Boidae), phythons (Pythonidae), and rat snakes (Colubridae)
Non-venomous snakes, kill their prey by suffocation
Generally no fangs
Numerous small backward curving teeth
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22. Snakes 5888H - Veterinary Dental Nursing
HOLLOW-FANGED SNAKES e.g. vipers (Viperidae), adders, mambas & cobras (Elapidae)
Poisonous snakes
Venomous fangs at anterior of jaw
Most poisonous snakes
Fangs are hollow and resemble hypodermic needles
Each fang is connected to the venom gland by a narrow tube
The two main types of hollow-fanged snakes, the vipers and elapids, differ in that vipers have long moveable front fangs. The fangs are folded backward in a sheath on the roof of the mouth when not being used, and are erected when the snake strikes. Elapids in contrast have short front fangs, which stay fixed.
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23. Snakes 5888H - Veterinary Dental Nursing
GROOVE-FANGED SNAKES e.g. boomslang (Colubridae).
Poisonous snakes
Venomous fangs at posterior of the jaw
Generally less dangerous as venom is released more slowly
Fangs are grooved
Venom runs down groove into bite wound
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24. Upper Pads
Sheep & Cattle
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25. The End
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