Veterinary dental nursing procedures TYPES OF DENTITION

5888H - Veterinary Dental Nursing

Function of teeth Defence Acquiring food Holding food Picking up Catching Killing Holding food Breaking down food Cutting (shearing) Crushing (grinding) 5888H - Veterinary Dental Nursing

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 5888H - Veterinary Dental Nursing

Shark teeth – new rows 5888H - Veterinary Dental Nursing

In the mammalian embryo Bud forms in oral mucosa First completely buried then resurfaces 5888H - Veterinary Dental Nursing

Evolutionary classifications tooth location anchorage number form number of replacement sets cycles of replacement 5888H - Veterinary Dental Nursing

Tooth location Fish Mammals on most jaw/palate bones Premaxilla-Maxilla Mandible 5888H - Veterinary Dental Nursing

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 5888H - Veterinary Dental Nursing

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. 5888H - Veterinary Dental Nursing

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 5888H - Veterinary Dental Nursing

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) 5888H - Veterinary Dental Nursing

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) 5888H - Veterinary Dental Nursing

Closed & Open Roots Closed Open 5888H - Veterinary Dental Nursing

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 5888H - Veterinary Dental Nursing

Closed Roots (e.g. cat, dog, man) 5888H - Veterinary Dental Nursing

Open Roots (rabbit) 5888H - Veterinary Dental Nursing

Replacement patterns Vertical Horizontal e.g. horse e.g. elephant 5888H - Veterinary Dental Nursing

Elephant Horizontal replacement 5888H - Veterinary Dental Nursing

Horse Vertical replacement 5888H - Veterinary Dental Nursing

Snakes 5888H - Veterinary Dental Nursing http://d-mis-web.ana.bris.ac.uk/calnet/snakeskele/page5.htm 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 5888H - Veterinary Dental Nursing

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. 5888H - Veterinary Dental Nursing

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 5888H - Veterinary Dental Nursing

Upper Pads Sheep & Cattle 5888H - Veterinary Dental Nursing

The End 5888H - Veterinary Dental Nursing