Dentistry Recap

Types of teeth

diphyodont - two sets of teeth

Brachydont

• Deciduous + permanent teeth

• Permanent teeth erupt and stop growing

• Short crowned, deep rooted

  • periodontal ligament (taut collagen fiber bundles) anchors cementum to jaw alveolar bone

  • odontoblasts (from dental papilla - neural crest derived) produce dentine

  • amelioblasts (from inner layer of enamel organ) produce enamel - disappear upon eruption

  • crown: dentine → enamel

  • root: pulp cavity→ odontoblast layer → dentine → cementum

  • nerves and blood vessels in pulp cavity

  • cemento-enamel junction where root meets crown

Hypsodont

• Radicular

  • 2 sets - second set erupts and grows continuously

  • Closed root = finite amount of growth

  • Complex infoldings of cementum, enamel, dentine

    • Peripheral and central cementum

    • Peripheral and central enamel

    • Dentine divides peripheral + central enamel

    • Infundibulum between central cementum

• Aradicular

  • erupt continuously, no true root

Horse teeth key facts

• 5 years

  • central cementum + infundibulum

• 10 years

  • wear exposes pulp cavity (nerves + blood recede)

  • secondary dentine filling in pulp cavity

  • infundibulum basically nonexistent (mark)

• 13 years

  • central enamel + cementum → dental star

• Upper/lower enamel ring structures are complementary

• Older animals → more acute angle in incisor occlusion plane

Monophyodont animals

some rodents e.g. rats

Rabbits

Horse

• labial cervical root maintains stem cell reservoir

• gives rise to teeth below the gum line

Mammal juvenile vs mammal adult

• diphyodonts

Formation of adult tooth 

• primordium of permanent tooth forms = buds off enamel organ (dental bud = orginal invagination of mesenchyne)

• teeth (in general) formed from neural crest mesenchyme which originate underneath oral epithlium

• therefore arises from dental lamina remnant of oral epithelium 

Forces of eruption

1. Resorption or remodelling of baby tooth → creates pathway

2. Hydrostatic pressure → pushes tooth tip into mouth

3. Periodontal ligament → upwards eruptive force

Dog dental formulae

• Symmetrical - do one half of mouth only

• Brachycephaly - rostrocaudal compression - fused roots, missing cheek teeth

• Adult dog - 42 teeth

• More teeth on lower jaw

• I (3/3) - 1 root

• C (1/1) - 1 root

• P

  • Deciduous (3/3)

  • Adult (4/4) → +1

• M - adult only (2/3)

• Carnassials → UP4 + LM1

P1 - always 1 root

Lower jaw onwards - 2 roots

Explaining the upper jaw:

2 rooted teeth

• UP2, UP3, LM1-3

3 rooted teeth

• UP4, UM1, UM2

Cat dental formulae

• 30 teeth

• More teeth on upper jaw

• I (3/3) - 1 root

• C (1/1) - 1 root

• P (3/2)

• M - adult only (1/1)

Rabbit dental formulae

• 28 teeth

• More teeth on upper jaw

• No canines

• Large diastema after incisors

  • Therefore skip teeth 3-5 (1C, 2P)

• Can clip incisors - aradicular (no root, very deep pulp cavity)

• I (2/1)

• P (3/2)

• M (3/3)

Horse dental formula

• Tend to be even top/bottom

• Some horses can have wolf teeth

  • tiny premolar after canine position

• Male horses - sometimes canines

Different options

Female - no wolf

333/333

• if wolf increase bold number

Male - can have canines

3(1)33/3(1)33

Tridan dental system

• splits mouth into clockwise quadrants

• UR = 1 → LR = 4 

Quadrant is first number

Upper 1&2

Lower 3&4

central incisor = 01

• rabbits have 2/1 incisors - all others have 3

canines = 04

wolf tooth = 05 (sometimes missing in horse, always missing in a cat)

premolars = 05 - 08 (dogs have 4)

molars = 09 onwards

Aging sheep - measure adult incisors

0 adult pairs → lamb <1

1 adult pairs → 1-2

2 adult pairs → 2-3

3 adult pairs → 3-4

4 adult pairs → >4

Ruminants - lower incisors do not erupt continuously but Ps and Ms do!

• upper incisors REPLACES - fibrous dental pad

Pig

• incisors project rostrally

• canines = continuously erupting tusks (both male and female)