Teeth and Mastication Flashcards
What is the role of the incisors
nibbling
grooming
cutting
What is the role of the canines
grasping
fighting/defence
stabbing
toxin injection
what is the role of the premolars and molars
depends on diet
crushing
shearing
gripping
grinding
What extra teeth do snakes have?
Pteryoid teeth
Labial/buccal meaning
lateral/cheek side
Lingual meaning
medial side of mandibular teeth
Palatal meaning
medial side of maxillary teeth
mesial meaning
rostral side
distal meaning (teeth)
caudal side
occlusal meaning
meeting surface of teeth
cusps meaning
raised parts of occlusal surface
furcation meaning
where roots come together
coronal meaning
towards tip of crown
apical meaning
towards root
Homodont definition and species examples
All teeth similar
e.g., reptiles, fish, amphibians
Heterodont meaning and species examples
Teeth dissimilar
e.g., mammals, some reptiles
Monophyodont meaning and species examples
Adult set of teeth only
e.g., rodents, marsupials
Polyphyodont meaning and species examples
Teeth continuously replaced
e.g., reptiles, fish, kangaroos, elephants
Diphyodont meaning
Two sets of teeth
Zalambdodont tooth meaning
3 cusps, single largest lingually
Dilambdodont tooth meaning
W-shaped occlusal surface
Bunodont tooth meaning
rounded crowns, often quadrate
Lophodont tooth meaning
cusps as folded ridges
Selenodont tooth meaning
cusps as crescents
Secodont tooth meaning
cutting edges/shearing
e.g., carnivore carnassials
loxodont tooth meaning
highly folded cusps to form a rasp
Hypsodont tooth meaning
High crowns
Most of tooth hidden in jaw bone
Brachydont tooth meaning
low crowns
half visible, half in jaw
Anelodont tooth meaning
erupt to fixed height, not growing or erupting continuously
radicular tooth meaning
closed root
Elondont tooth meaning
open root - grows continuously
How to carnivores chew?
Moves jaw sideways to engage carnassial teeth
Close jaw to shear/crush
How do omnivores chew?
combined crush/grind action
How do herbivores chew?
close jaw on herbage
move jaw sideways whilst held closed -> grinds plant material
What muscles are used to move jaw sideways
pteryoideus muscles
what muscles are used to close the jaw
masseter and temporalis muscles
How are carnivore and herbivore skulls adapted for their diet?
Longer vertical ramus radius gives more even occlusion in herbivores
Shorter vertical ramus radius produced scissor-action in carnivores
Diastema definition
gap between incisors and cheek teeth
The gingiva is a mucoperiosteum. What does this mean?
the oral mucosa is firmly attached to the underlying periosteum
Describe the components of the crown of the tooth
Visible/supragingival part
Enamel: hard, smooth
Dentine: hard, tubules
Cusps
Pulp cavity
Describe the components of the root of the tooth
Cementum
Dentine
Root canal
Apex-apical delta
Single and multi rooted
What happens to pulp as the animal ages?
It is gradually replaced by secondary dentine
Describe the composition of enamel
97% hydroxyapatite
Acellular
No collagen (special support proteins instead)
Enamel Ca is in equilibrium with salivary Ca
Dissolved in acid
Only on crown
No repair possible
Describe the composition of dentine
Odontoblasts produce dentine tubules
cytoplasmic processes within dentinal tubules
Describe primary, secondary and tertiary dentine
Primary:
- most of dentine
- formed as tooth grows
- mineralized collagen
Secondary:
- grows slowly on daily basis
- forms after eruption
- makes pulp smaller
Tertiary:
- reaction to damage
- irregular structure
- helps to fill in damage
Label this tooth
Describe the pulp cavity
Contains blood vessels, lymph, nerves
Location of secondary dentine deposition (pulp narrows with age)
Closed apex when finished erupting
Open apex for continually growing teeth
Apical delta - many small canals at apex
Describe the function of cementum
Similar to bone
Attachment for periodontal fibres
Completely covers herbivore teeth
What is a closed root?
Root apex closed off - does not grow once formed
Can erupt slowly and continuously e.g., horses, cattle
Or teeth can erupt to a fixed height e.g., carnivores and omnivores
What is an open root?
Root apex is open - continuously growing elodont
Teeth grows and erupts continuously
e.g., rodents and many lagomorphs
What is the periodontium?
The supportive structures of the tooth
What are the components of the periodonteum?
Alveolar bone (lamina dura)
Periodontal ligament
Cementum
Gingiva
Label the periodontium (3,6,7,8)
3 = cementum
6 = periodontal ligament
7 = alveolar bone/lamina dura
8 = gingiva
Describe the structure and composition of gingiva
Squamous epithelium
Dense fibrous layer
Closely bound to periosteum
Reflects at cemento-enamel junction (CEJ) to form a pocket (the gingival sulcus)
What is the clincal relevance of the gingival sulcus?
Site for food debris to be trapped
Site where inflammation starts (gingivitis)
Describe the composition and function of the periodontal ligament
Series of angles collagen fibres
Supports the tooth
Shock absorber
Spreads load into whole socket
Describe the process of tooth development
- Lines of epithelial cells condense along the jaw margins and invaginate to from a dental bud
- the epithelial cells become ameloblasts and form the enamel organ
- the dental bud in-folds to form a dental cap under which neural crest-derived mesenchyme form a dental papilla
- the mesenchymal cells become odontoblasts and form dentine
- mesenchyme around the bud forms a vascular dental sac/follicle
- the inner layer of the follicle forms cementoblasts and form cementum
- the outer layer of the follicle form osteoblasts which form the alveolar bone
What is the enamel organ made up of?
Stellate reticulum
Ameloblasts (inner enamel epithelium)
Outer enamel epithelium
What happens to the enamel once the tooth has erupted?
The enamel dies and is no longer produced (this leaves behind hard enamel)
How does the adult tooth remove the deciduous tooth?
It crushes the pulp of the deciduous tooth to cut off blood supply so it ‘dies’
Why is correct eruption important?
If eruption goes wrong then tooth impaction can occur (new tooth becomes jammed by permanent teeth), this can impact the animals ability to eat
Describe tooth eruption in horses
Teeth erupt as they grow
Roots close later in life
Teeth continue to erupt throughout life
Describe tooth eruption in carnivores
Teeth erupt as they finish growing
Teeth erupt to a certain height then stop
What is the clinical relevance of horse teeth eruption rate?
Teeth grows and wear most rapidly in first 5 years after eruption - this means that up to 9 yrs old there is a higher risk of creating sharp points
What is the clinical relevance of constant tooth eruption in herbivores?
Can lead to too much tooth pushing into jaw if growth/eruption rate is greater than the degradation of the tooth
What muscles close the carnivores mouth during mastication and what nerve supplies them?
Temporalis
Masseter
V3 (mandibular branch of trigeminal nerve)
What muscle opens the carnivores mouth during mastication and which nerves supply it?
Digastricus
V3 (manidbular branch of trigeminal nerve) and VII (facial)
What are the masticatory muscles in herbivores and what nerve supplies them?
Temporalis
Lateral and medial pterygoideus
Masseter
V3 (mandibular branch of trigeminal)
What is the arterial supply of the upper teeth
Infraorbital artery
Major palatine artery
What is the arterial supply of the lower teeth?
Inferior alveolar artery
What is the clinical relevance of the major palatine artery?
Can be damaged during upper teeth extraction
What is the venous drainage of the masticatory muscles?
maxillary vein and deep facial vein
Describe the nerve supply to the maxilla
Infraorbital nerve (V2)
Enters maxillary foramen
Sensory branches to tooth rooth
exits at infraorbital foramen
Describe the nerve supply to the mandible
Mandibular nerve (V3)
Enters mandibular foramen
Travels in mandibular canal
Sensory branches to tooth roots (PM + M)
Middle mental nerve is sensory to I+C (incisors and canines)
What are the 4 dental nerve blocks and what do they block?
Maxillary nerve (V2) - I+C+PM+M
Infraorbital nerve (V2) - I+C+PM
Inferior alveolar nerve (via the mandibular foramen) (V3) - I+C+PM+M
Middle mental nerve (via the middle mental foramen) (V3) - I+C
Identify these nerve block sites
Describe the anatomy and function of the temporo-mandibular joint
Synovial joint
Hinge joint
Also has lateral movement and rostro-caudal movement to allows for grinding and opposing of teeth
Well developed meniscus which develops 2 synovial compartments:
- skull-side for translation movements
- mandible-side for hinge movements
Explain the modified triadan system
3 digits to identify the tooth
1st digit = quadrant (1-4 or 5-8 in deciduous teeth)
2nd and 3rd digit identifies tooth
Incisors: 01, 02, 03
Canines: 04
Premolars: 05, 06, 07, 08
Molars: 09, 10, 11
Describe the use of dental formulae
Describe carnivore dentition
Brachydont
Erupt to set height
Jaws have to move laterally to bring carnassials into action
What are the functions of carnivorous teeth
Incisors: nibbling/nipping
Canines: puncute/grasp
Carnassials: cut/shear
Molars: crush
How many teeth does a cat have?
30
How many teeth does a dog have?
42
What is the dental formulae for a dog?
What is the dental formulae for a cat?
Which teeth are the carnassial teeth and what is their function?
Large cutting teeth
Upper PM4
Lower M1
What are the eruption times for kitten deciduous teeth?
Incisors: 3-4wks
Canines: 3-4 wks
Premolars: 5-6wks
What are the eruption times for puppy deciduous teeth?
Incisors: 4-6wks
Canines: 3-5wks
Premolars: 5-6 wks
hello
goodbye
What are the eruption times for dog permanent teeth?
Incisors: 3-4m
Canines: 3-4m
Premolars: 4-5m
Molars: 4-6m
Clinical relevance of brachcephalic dog teeth
Jaws bred to be short so less from for teeth
Describe the dentition of herbivores
Hypsodont - high crown
adapted dentition of cheek teeth (molars and premolars) - flat surfaced and folded enamel
Grinding
Continuous eruption/growth to match wear
Describe bovidae dentition
Selenodont and hypsodont
Folded enamel creates multiple grinding edges
Teeth are moved sideways during chewing
Incisors and canines are brachyodont
Have no upper incisors or canines (have a dental pad instead)
What is the basic dental formulae for horses and when may it differ?
How can a horses lower incisors be used to find its age?
Hypsodont - erupt throughout life - can work out age by cross section due to wear
Can also use eruption ages:
2.5 yrs - x01 erupts
3.5yrs - x02 erupts
4.5yrs x03 erupts
What are tushes?
equine canine teeth
can get them in stallions and geldings (rare in mares)
Brachydont
What are wolf teeth?
first PM of upper jaw in horses (rarely get first PM of lower jaw)
Redundant regressed teeth
appear at 3-5yrs
if small can wobble and interfere with bit (get removed)
if large then quite stable
Describe the structure of equine premolars and molars
Lophodont
Folded enamel creates multiple grinding edges
teeth are moves sideways for chewing
clinical relevance of premolar and molar eruption times in horses
PM4 erupts last and has to erupt inbetween M1 and PM3 so may become impacted
Describe the dentition of lagomorphs (rabbits and hares)
All teeth elodont (grow continually)
Shed deciduous teeth at birth
4 incisors in maxilla
Describe the dentition of rodentia (rats, mice, beavers)
elondont incisors
brachydont PM+M
2 incisors in maxilla
Describe pig dentition
bunudont - low, rounded cusps
cusps covered with enamel
food trapped between occlusal faces and crushed (not much grinding)
Incisors point forwards to aid digging
Piglet teeth clipped 2-3 days old
Elodont canines
Have the max number of teeth for mammals
