Comparative Dental Anatomy

The horse is a herbivore, what types of dental adaptations do they have to reflect this diet?

• Highly abrasive diet, requiring premolars to be enlarged, matching the molars

  • Provides a continuous grinding surface at roughly the same level

• High, durable crowns

  • Show hypsodont: gradual extrusion of tooth

  • Hypsodont teeth are a characteristic of horses, meaning they have long crowns and short roots, and their teeth continue to erupt throughout their lives

  • Delayed root formation, continued eruption after teeth come into wear (~5 years)

• Large gap between incisors and premolars

  • Interdental space in equine medicine

Why does equine enamel have multiple folds?

• Increases area of abrasive surface

• Alternating dental tissues (enamel, dentine, cementum)

  • Rasp like functions

  • Different patterns in different teeth

What is the equine dental formula?

Temporary Dentition

• Upper - 3-0-3

• Lower - 3-0-3

Permanent Dentition

• Upper - 3-1-3(4)-3

  • Sometimes 4, is the first upper premolar (AKA wolf tooth, often fails to develope)

  • If present, almost always upper jaw only

• Lower - 3-1-3-3

**Canines are rudimentary, often do not erupt in females

**Decidious teeth similar to permanent (But smaller), incisors have obvious neck

What are the main features of the equine incisors (01-03)?

• Arranged in continuous arch

• Infundibulum overlaps with the pulp cavity

• Cement centre to infundibulum with a small cavity

  • Called the cup

• As wear increases, secondary dentine forms before pulp exposed (Shows as dental star as tooth is worn down)

What are the main features of the equine canine teeth?

• Rudimentary

• Frequently not seen in females, may be seen in males

• Found in diastema

• “Icebergs” - reserved crown portion of tooth much larger than exposed tooth

What are the main features of the first equine premolar (05) “wolf tooth”?

• First premolar (wolf tooth)

• Can be absent or vestigial

• Usually confined to the upper jaw

• May cause problems with bit if overly large, displaced or damaged

What are the main features of the equine cheek teeth (06-11)?

• 2nd - 4th premolars and molars

• 2nd premolar (06) and 3rd molar (11) more triangular in occlusal surface

  • Other teeth are more rectangular

• Upper cheek teeth are…

  • Wider

  • More complex enamel folding pattern creating infundibula

• Occlusion

  • Upper teeth more buccal to lower teeth

  • Meet two of opposing arcades

What are the main features of the equine upper cheek tooth roots?

• Upper 4th premolar and molars

• Roots in maxillary sinuses

• Exact location depends on age

• Risk of infection spreading to sinus

What are the main features of ruminant dentition?

• No upper incisor or canine teeth, replaced by dental pad

• Lower canines appear as “4th incisor”

• Large diastema

• 6 Cheek Teeth, upper and lower

  • Complex enamel cusps

• Hypsodont, with delayed root closure

What is the ruminant dental formula?

• Temporary similar to permanent

• Deciduous premolars larger and more complicated, initially greater contribution to mastication

Temporary

• Upper - 0-0-3

• Lower 3-1-3

Permanent

• Upper - 0-0-3-3

• Lower - 3-1-3-3

What are the main features of the dental pad?

• Crescent shaped with keratinized surface, contains incisive papilla

• Compliant on compression

• Grazing

  • Grass drawn in by tongue, severed by lower incisors against pad

What are the main features of the ruminant incisors?

• Three incisors and canine

• Wide, asymmetric spatulate crown

• Narrow root

• Increased exposure of dentine with age

• Old animals - only narrow root may remain

How can we age sheep by their incisors?

Roughly 2 adult teeth per year

• Count number of adult incisors, divide by two = rough age

What are the main features of ruminant cheek teeth?

• No first premolar

• Increase in size from cranial to caudal

• Crescentic enamel cusps arranged along line of teeth

  • One pair in premolars

  • Two pairs in molars

What are the main features of porcine dentition?

• Most complete set of teeth in domestic animals

• Upper incisors curved, lower incisors straight

• Curved canine teeth

  • Tusks

  • Roots remain open, with continued growth in boars

  • Roots close around 2 years old in sows

What is the porcine dental formula?

• Piglets born with 8 teeth (Later grow temporary)

  • Temporary 3rd incisors and canines (needle teeth)

• Cheek teeth increases in size caudally

• Molars massive with irregular occlusal surface

Temporary Dentition

• Upper - 3-1-3

• Lower - 3-1-3

Permanent

• Upper - 3-1-4-3

• Lower - 3-1-4-3