Module 1.1 Dental Anatomy

Question 0

Do the shapes of dental arcades change between different species?

Answer 0

Yes

Question 1

What are the two dental arcades?

Answer 1

Mandible (lower jaw)

Incisive & maxillary bones (upper jaw)

Question 2

How can dental arcades be helpful in speciation or tracing evolutionary ancestors of a species?

Answer 2

There will be an obvious similarity in the dental arcade for animals of the same species. There will be obvious transition in the dental arcade for the evolutionary ancestors of a species, up until the modern dental arcade.

Question 3

What are the four main kinds of teeth and their abreviations?

Answer 3

Incisors (I), Canine (C), Premolar (P) and Molar (M)

Question 4

What is a Diastema? What animals commonly have it and between which teeth?

Answer 4

It’s an abnormal space between teeth.

Farm animals usually have a Diastema between their incisors and cheek teeth in each arch.

Question 5

What is Quidding?

Answer 5

When an animal cannot grip food properly when eating and appears to dribble out pieces of food.

Question 6

What is an abnormal Diastema in horses? What can it cause?

Answer 6

A gap in the teeth other than the gap between incisors and cheek teeth. Causes packing of putrefying material, infection & tissue destruction. Inflammation then spreads to adjacent teeth, causing their erosion & eventual loss. Main cause of oral discomfort, quidding & weight loss.

Question 7

What are Heterodonty teeth?

Answer 7

various types of teeth that are specialised for different aspects of prehension & mastication

Question 8

What are Diphyodont teeth?

Answer 8

A set of deciduous teeth that fall out & are replaced by permanent teeth

Question 9

Which animals have Diphyodont teeth? What are they useful for?

Answer 9

All domestic animals. Useful for rough ageing an animal as eruption time is fairly consistent within a species (some variation occurs, it’s not a science)

Question 10

What are the properties of the four kinds of teeth in carnivores?

Answer 10

Incisors short, pointed & prong-like → used for grasping & shredding

Canines are greatly elongated & dagger-like for stabbing, tearing & killing prey

Molars (carnassials) flattened & triangular with jagged edges

Question 11

What are the properties of the four different kinds of teeth in herbivores? What does it depend on?

Answer 11

Depends on their particular food type.

Incisors broad: flattened & spade-like

Canines: may be small as in horses, prominent as in hippos, pigs & some primates or absent altogether

Molars: in general, squared & flattened on top to provide grinding surface. Cannot vertically slide past one another in shearing/slicing motion, but do horizontally slide across one another to crush & grind

Question 12

What is the name of the socket of bone that the tooth is attached to?

Answer 12

Alveolus

Question 13

What is the name of the connective tissue/ligament that attaches the tooth to the Alveolus (tooth socket in jaw)?

Answer 13

Periodontium (periodontal ligament/membreane)

Question 14

What is the name of the part of tooth that is visible above the mucous membrane of the gum?

Answer 14

Crown

Question 15

What are the properties of a brachyodont tooth?

Answer 15

short crown separated from root by distinct neck

Human teeth

Question 16

What are the properties of a Hypsodont tooth?

Answer 16

Teeth with no discernible neck
Continue to grow in length after erupting
Equine incisors & cheek teeth

Question 17

What mineralised substance makes up the majority of the tooth?

Answer 17

Dentin

Question 18

What is dentin composed of?

Answer 18

Inorganic calcium hydroxyapatite 70%

Organic component in type I and type V collagen

Question 19

Where is the dental cavity located?

Answer 19

In the centre of the dentin

Question 20

What composes the dental pulp?

Answer 20

capillaries, nerves, lymphatics & loose

connective tissue

Question 21

What is the role of the dental pulp?

Answer 21

Nourishes dentin

Question 22

Where is enamel located?

Answer 22

Superficial to dentin
Covers nearly entire hypsodont tooth except short
region of tooth‟s root
Only crowns of brachyodont teeth covered with enamel

Question 23

What is enamel comprised of?

Answer 23

98% hydroxyapatite, 2% keratin

Question 24

How is enamel made? Is it continuously made?

Answer 24

Enamel proteins & tooth minerals secreted by polarised cells called ameloblasts during secretory stage of enamel formation (amelogenesis)

Enamel irreplaceable as ameloblasts lost following formation of the tooth
Exception being tusks (canine teeth) of pigs

Question 25

What is the structure of enamel?

Answer 25

Extremely long & parallel organised hydroxyapatite crystals organised in bundles called prisms. Rows of enamel prisms are often organised perpendicular to each other.

Question 26

How does enamel on Hypsodont teeth differ from enamel on brachyodont teeth?

Answer 26

Hypsodont teeth enamel thrown into prominent folds on grinding surfaces (of these teeth), where they form:
Crests (cristae enameli)
Cups (infundibulum [single]/ infundibula [plural])  Funnel-like centre

Question 27

What is cementum?

Answer 27

Layer of tough, yellowish, bone-like tissue covering root of tooth

Question 28

What comprises cementum?

Answer 28

Made up of lamellae oriented parallel to surface of tooth with cementocytes occupying lacunae (spaces)

65% mineral, 35% organic matter & H2O

Question 29

Where is cementum located?

Answer 29

Covers external surface prior to eruption, fills infundibulum
Extends from root to cover crown of hypsodont
tooth
Covers only root of brachyodont tooth

Question 30

What is the function of dentin and cementum layers?

Answer 30

absorb shock & prevents enamel from chipping & cracking

Question 31

What is the purpose of layered dental substances?

Answer 31

Layering of dental substances protects enamel, enabling exposed edges to act as self-sharpening blades to shred roughage

Question 32

Describe incisors locations and uses

Answer 32

Front of mouth

Used for cutting or clipping

Question 33

Describe canines uses

Answer 33

For puncturing or holding

Question 34

Describe premolars locations and uses

Answer 34

Crushing or grinding food

Collective term = cheek teeth or molariform teeth

Question 35

What are sectorial teeth?

Answer 35

Teeth modified so that ridges on opposing teeth slice by one another to cut tissue
In the order Carnivora, upper 4th premolar & lower 1st molar form carnassial
Specialised sectorial teeth that slice against each other like scissors to cut sinew & muscle

Question 36

What are some other animals with specialised teeth?

Answer 36

Tusks (elephants and walruses)

Question 37

Do all mammals have teeth?

Answer 37

No, anteaters and baleen whales don’t

Question 38

How are sloths different with regards to teeth?

Answer 38

Have no incisors - tears off leaves with its tough lips
Chews with its rear, peg-like teeth
Unlike most leaf-eating mammals it lacks many deeply rooted, hard, enamel-covered grinding teeth
Has comparatively few teeth
18 compared to 32 in most deer
Teeth lack enamel & wear easily
Teeth grow slowly throughout life
No change of teeth from milk to permanent dentition

Question 39

How is the diet of the horses ancestor (Hyracotherium) different to that of the modern horse, and how has that changed the anatomy of the horses teeth?

Answer 39

Hyracotherium Consumed diet of succulent plants that caused little dental wear on its short crowned (brachyodont) teeth

Modern horse eats Cellulose and abrasive silicate foods, creating more dental wear. Horses evolved to have Hypsodont teeth which were long and constantly erupted to combat the wear on their teeth

Question 40

What happened to equine teeth over the evolution from their ancestors, the Eohippus, to modern horses?

Answer 40

incisors widened, premolars altered to molars, & molars became very high- crowned with highly complex folding of
enamel

Question 41

What is the collective term for equine molars and premolars?

Answer 41

Cheek teeth

Question 42

How many incisors does a horse have in each arcade?

Answer 42

6, total 12.

Question 43

What is the difference between equine deciduous teeth and permanent teeth?

Answer 43

Deciduous teeth: whiter, smaller, have constricted neck, no infundibulum

Permanent teeth: larger, yellowish (cementum), no identifiable neck, distinct vertical ridges

Question 44

What does a horse use its incisors for?

Answer 44

Nipping and tearing foliage

Defence

Question 45

How does the angle of a horses incisors change as it ages?

Answer 45

changes from almost vertical in young horses towards horizontal in old horses

Question 46

Do canine teeth form in both male and female horses?

Answer 46

Yes, but often fail to erupt in mares

Question 47

How many canine teeth do male horses normally have? When and where do they erupt?

Answer 47

4

4-6 years of age in the interdental space (space between incisors and premolars)

Question 48

Do horses have wolf teeth?

Answer 48

Yes, thir first premolar in all 4 arcades, rudimentary teeth

Question 49

How many cheek teeth in total does a horse have?

Answer 49

24, 12 premolars and 12 molars

Question 50

What differences are there between a horses mandibular and maxillary cheek teeth?

Answer 50

Maxillary much wider & more complicated folding of

enamel

Question 51

What special feature do horse cheek teeth have in their structure?

Answer 51

Fusion of cusps in ridges (lophs)

Question 52

In young horses, do all their cheek teeth exist fully errupted?

Answer 52

No, only small part of each cheek tooth visible, as most of crown lies developed but unerupted below gum. Teeth continue to erupt, maintaining intraoral height even as they are worn down by a diet of coarse forage

Question 53

What does ‘floating the teeth’ in horses refer to?

Answer 53

Filing down of sharp elongated ridges on the cheek teeth in horses. They are prone to developing these and they may cause discomfort and infections if not cared for.