Teeth, Mastication and sinuses 1 Flashcards
What are the primary germ layers?
- Ectoderm
- Mesoderm
- Endoderm
What specifically does the ectoderm form?
- epidermis of the skin, oral/nasal cavities epithelium, nervous system and sense organs
What specifically does the mesoderm form?
- forms muscles and connective tissue, including bone and components of the circulatory, urinary and genital systems
What specifically does the endoderm form?
- forms mucosal epithelium and glands of respiratory and digestive systems
What does distinct thickening of the oral epithelium form?
- forms dental lamina
What happens after dental lamina is formed?
- underlying mesenchyme condenses
What happens after mesenchyme condenses?
- dental lamina invaginates to form the dental bud
As the dental bud expands what happens?
- it branches to form an enamel organ to surround dental papilla
What does a complex of dental papilla and enamel organ form?
- will form the deciduous tooth
What cells are involved in cell differentiation (in the tooth)
- ameloblasts
- odontoblasts
- cementoblasts
What do ameloblasts do?
- form epithelium
- secrete enamel matrix
What do odontoblasts from?
- from neural crest
- produce dentine (surrounds tooth pulp - produce tooth root)
What do cementoblasts do?
- from mesenchyme = secretes cementum around root
What do dental buds do?
- give rise to individual teeth
What determines the size, shape, and location of the teeth?
- genetically and independently determined for each tooth
What happens if the bud is destined to form a deciduous tooth?
- An additional bud for its permanent replacement develops superficial and medial to the deciduous bud
- this is called a lingual extension leading to successional lamina
How is successional lamina formed?
- through the same stages of development of deciduous teeth
What happens if the deciduous tooth is congenitally missing?
- no permanent tooth will develop
When does calcification occur?
- from day 55 gestation to day 20 pp
what does the 1st premolar and the molars not have in some species?
- no deciduous teeth
When should dogs and cats deciduous teeth have fully erupted?
- fully erupted by 2 months old
In dogs and cats when should their deciduous teeth have been replaced by adult teeth?
- 6 months
What is the order of eruption in dogs?
- canines erupt, followed by incisors, then 4th, 3rd, 2nd premolars
- for total of 28 primary teeth
When should Equine deciduous teeth erupt by?
- 6 months
When should the adult incisors have fully erupted in the horse?
- first incisors = 2.5 yrs
- second incisors = 3.5 yrs
- third incisors = 4.5 yrs
Describe the eruption of the temporary tooth?
- eruption after crown is fully formed, but before completion formation of the root
- eruption provides space for completion of root
- epithelial covering is continuous with gums upon eruption
- wear removes epithelium
Describe how the permanent tooth replaces the deciduous tooth
- migrates into socket of temporary tooth
- pressure increases = resorption of temporary tooth
- tooth root loosens and shreds = permanent tooth replaces
What is enamel?
- from ameloblasts
- hardest material in body
- between dentin and cementum
- no healing
What is dentine?
- from odontonblasts
- with enamel = outer two layers
- form during crown stage
What is a periodontal ligament?
- specialised connective tissue
- inserts into root cementum and alveolar
- holds teeth in sprung suspension
- also has sensory function - teeth in contact (enamel insert)
What is cementum?
- from cementoblats within root
- thickest at root apex
- gives attachment to periodontal ligament
what is a brachydont?
- low-crowned teeth, seen in humans dogs, cats, pigs
- tooth consists crown above gingiva, constricted neck at the gum line and a root embedded in the jawbone
- enamel covers entire body of the tooth, but not root
What is a hypsodont?
- high- crowned teeth, seen in horses, cows
- teeth extend usually far below the gumline - lots of extra material for wear
- crown continues continues to erupt, in response to age and wear
What is radicular?
- the root closes after eruption (horses, cows)
What is aradicular?
- open-rooted, doesn’t close, tooth grows continually through life = elodont (rabbits, guinea pigs, chinchillas and degus)
What is heterodonty?
- teeth differentiated into incisors, canines and molar
What is homodonty?
- teeth all, the same form
What is the contact surface of teeth?
- where adjacent teeth touch
What is the occlusal of teeth?
- where opposing teeth touch
Describe incisors 3/3
- tricuspid in upper jaw
- bi-loped in lower jaw
- smaller rostrally
- single root
Describe premolars 4/4
- irregular, closely-spaced
- complex and larger caudally
- discontinuous cutting crown
Describe canine 1/1
- large curved laterally compressed
- root longer than crown
- single root
Describe molars 2/3
- broader than premolars
- number of cusps
- similar in all breeds
What happens to dogs gums with age?
- gums recede with age which exposes the non-enamel coated surface
What’s is different in brachycephalic breeds teeth?
- do not possess all canine cheek teeth
- often have teeth with fused roots
What are carnassial teeth?
- last upper premolar, paired with lower molar
- laterally flattened, provides shearing action for cutting food
- characteristic of carnivore dentition
What type of teeth do horses have?
- hypsodont - teeth continually erupt
- erupted crown and un-erupted reserve crown
Describe horse incisors 3/3
- high crowns, folded enamel surfaces
- root converge
- useful for aging
Describe canines 1/1 in horses?
- sometimes present, uncommon in females
- erupt 4-6 years of age
What are wolf teeth?
- sometimes present
- vestigial premolars, sit against PM1
- may interfere with bit
Describe horse premolars PM 3-4/3
- 4 upper if wolf tooth
- continuous with molars
- very high wear, erupt continuously
- upper wider than lower
Describe horse molars M3/3
- continuous with PM
- very high wear, erupt continuously
- upper wider than lower
Horse - what is the infundibulum?
- infolding of enamel
Horse - what is the cup?
when does it wear away and what happens to it?
- centre of infundibulum
- Disappears at 8yrs and leaves enamel spot = deepest part of infundibulum
Horse - what is the dental star?
- corresponds with pulp cavity - appears at 8 yrs in first incisor
- appears as a line and then changes to a large round spot as occlusal surface is worn further
Describe rodent dentition
- no canines
- very large diastema
- no pulp cavity = thus teeth insensitive
Describe pig dentation
- incisors project rostrally
- canine present as continuously erupting tusks for digging and tearing
- PM have rounded cups for crushing and grinding
Describe cattle dentition
- no upper canines = replaced by hard fibrous dental pad
- incisors do not erupt continuously
- lower canine teeth very similar to incisors
- PM increased size caudally
- very similar to horse
- do not erupt continuously
- very pronounced enamel ridges
What reptiles don’t have teeth?
- turtle and tortoise
What type of teeth do reptiles have except venomus snakes and crocodilians?
- homodont
What are the variations in anchors in reptile teeth?
- very loose arrangement (accordant)
- stronger attachment (pleurodont) = most common
- strongest (thecodont) - in sockets within jaw
