Module 1.1 Dental Anatomy Flashcards
Do the shapes of dental arcades change between different species?
Yes
What are the two dental arcades?
Mandible (lower jaw)
Incisive & maxillary bones (upper jaw)
How can dental arcades be helpful in speciation or tracing evolutionary ancestors of a species?
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.
What are the four main kinds of teeth and their abreviations?
Incisors (I), Canine (C), Premolar (P) and Molar (M)
What is a Diastema? What animals commonly have it and between which teeth?
It’s an abnormal space between teeth.
Farm animals usually have a Diastema between their incisors and cheek teeth in each arch.
What is Quidding?
When an animal cannot grip food properly when eating and appears to dribble out pieces of food.
What is an abnormal Diastema in horses? What can it cause?
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.
What are Heterodonty teeth?
various types of teeth that are specialised for different aspects of prehension & mastication
What are Diphyodont teeth?
A set of deciduous teeth that fall out & are replaced by permanent teeth
Which animals have Diphyodont teeth? What are they useful for?
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)
What are the properties of the four kinds of teeth in carnivores?
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
What are the properties of the four different kinds of teeth in herbivores? What does it depend on?
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
What is the name of the socket of bone that the tooth is attached to?
Alveolus
What is the name of the connective tissue/ligament that attaches the tooth to the Alveolus (tooth socket in jaw)?
Periodontium (periodontal ligament/membreane)
What is the name of the part of tooth that is visible above the mucous membrane of the gum?
Crown
What are the properties of a brachyodont tooth?
short crown separated from root by distinct neck
Human teeth
What are the properties of a Hypsodont tooth?
Teeth with no discernible neck
Continue to grow in length after erupting
Equine incisors & cheek teeth
What mineralised substance makes up the majority of the tooth?
Dentin
What is dentin composed of?
Inorganic calcium hydroxyapatite 70%
Organic component in type I and type V collagen
Where is the dental cavity located?
In the centre of the dentin
What composes the dental pulp?
capillaries, nerves, lymphatics & loose
connective tissue
What is the role of the dental pulp?
Nourishes dentin
Where is enamel located?
Superficial to dentin
Covers nearly entire hypsodont tooth except short
region of tooth‟s root
Only crowns of brachyodont teeth covered with enamel
What is enamel comprised of?
98% hydroxyapatite, 2% keratin
How is enamel made? Is it continuously made?
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
What is the structure of enamel?
Extremely long & parallel organised hydroxyapatite crystals organised in bundles called prisms. Rows of enamel prisms are often organised perpendicular to each other.
How does enamel on Hypsodont teeth differ from enamel on brachyodont teeth?
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
What is cementum?
Layer of tough, yellowish, bone-like tissue covering root of tooth
What comprises cementum?
Made up of lamellae oriented parallel to surface of tooth with cementocytes occupying lacunae (spaces)
65% mineral, 35% organic matter & H2O
Where is cementum located?
Covers external surface prior to eruption, fills infundibulum
Extends from root to cover crown of hypsodont
tooth
Covers only root of brachyodont tooth
What is the function of dentin and cementum layers?
absorb shock & prevents enamel from chipping & cracking
What is the purpose of layered dental substances?
Layering of dental substances protects enamel, enabling exposed edges to act as self-sharpening blades to shred roughage
Describe incisors locations and uses
Front of mouth
Used for cutting or clipping
Describe canines uses
For puncturing or holding
Describe premolars locations and uses
Crushing or grinding food
Collective term = cheek teeth or molariform teeth
What are sectorial teeth?
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
What are some other animals with specialised teeth?
Tusks (elephants and walruses)
Do all mammals have teeth?
No, anteaters and baleen whales don’t
How are sloths different with regards to teeth?
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
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?
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
What happened to equine teeth over the evolution from their ancestors, the Eohippus, to modern horses?
incisors widened, premolars altered to molars, & molars became very high- crowned with highly complex folding of
enamel
What is the collective term for equine molars and premolars?
Cheek teeth
How many incisors does a horse have in each arcade?
6, total 12.
What is the difference between equine deciduous teeth and permanent teeth?
Deciduous teeth: whiter, smaller, have constricted neck, no infundibulum
Permanent teeth: larger, yellowish (cementum), no identifiable neck, distinct vertical ridges
What does a horse use its incisors for?
Nipping and tearing foliage
Defence
How does the angle of a horses incisors change as it ages?
changes from almost vertical in young horses towards horizontal in old horses
Do canine teeth form in both male and female horses?
Yes, but often fail to erupt in mares
How many canine teeth do male horses normally have? When and where do they erupt?
4
4-6 years of age in the interdental space (space between incisors and premolars)
Do horses have wolf teeth?
Yes, thir first premolar in all 4 arcades, rudimentary teeth
How many cheek teeth in total does a horse have?
24, 12 premolars and 12 molars
What differences are there between a horses mandibular and maxillary cheek teeth?
Maxillary much wider & more complicated folding of
enamel
What special feature do horse cheek teeth have in their structure?
Fusion of cusps in ridges (lophs)
In young horses, do all their cheek teeth exist fully errupted?
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
What does ‘floating the teeth’ in horses refer to?
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.
