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tooth development Flashcards

1
Q

when do deciduous teeth begin formation

A

week 6-7 of interuterine life

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2
Q

when do permanent teeth begin developing

A

week 14

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3
Q

when do permanent molars begin developing

A

week 20

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4
Q

what two tissue components begin the development of teeth

A

primitive oral epithelium
underlying ectomesenchyme

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5
Q

what is the ectomesenchyme derived from

A

craniofacial neural crest cells

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6
Q

what is the purpose of the primitive oral epithelium and the ectomesenchyme

A

they instruct each other to determine the formation and location of the teeth

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7
Q

how does tooth formation begin

A

thickening of the primitive oral epithelium to form the primary epithelial bands, with one on each jaw

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8
Q

what happens after the formation of the primary epithelial bands

A

each one splits into two - the inner dental lamina and the outer vestibular lamina

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9
Q

what does the vestibular lamina do

A

it hollows out to form the vestibule of the mouth, which is the space between the alveolar bone and the labial/buccal surfaces

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10
Q

which signal proteins causes the dental lamina cells to proliferate

A

FGFs
BMPs
ectodisplacin

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11
Q

what are dental placodes

A

localised projections in the dental lamina which are invaginations for the positions of the future teeth. form the enamel organ

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12
Q

what happens when the dental placodes proliferate

A

the teeth undergo morphogenesis, resulting in different tooth shapes.

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13
Q

what guides the proliferation of the dental placode

A

interactions between the epithelial and mesenchymal tissues

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14
Q

what are the three main stages of tooth morphogenesis

A

bud
cap
bell

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15
Q

describe the bud stage

A

this is when the dental placodes form bud like structures attached to the oral epithelium by the dental lamina
ectomesenchymal cells cluster around the bud to form a condensation of the ectomesenchyme right beneath the bud

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16
Q

what are the cell types forming the enamel organ at the bud stage

A

outer layer of low columnar cells and an inner bundle of polygonal cells

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17
Q

why is the bud stage unique

A

due to differential proliferation, ie the cells at the centre are slower to differentiate than those at the peripherals

18
Q

what makes the bud shape of the enamel organ become a cap shape

A

the differential proliferation of the bud stage cells

19
Q

describe the cells found in the cap stage of the enamel organ

A

inner enamel epithelium
outer enamel epithelium
stellate reticulum

20
Q

where is the inner enamel epithelium of the cap stage found

A

as a low columnar lining of the inner surface of the central depression of the cap

21
Q

describe the outer enamel epithelial lining of the cap

A

cuboidal lining around the side of the cap on the outside

22
Q

what is the stellate reticulum

A

cells linked by desmosomes that secrete glycosaminoglycans into the extracellular space, which attracts water in the ECS, pushing on their membranes to turn them into the shape of a star

23
Q

what are the enamel knots

A

non dividing cells at the inner enamel epithelium which are the signalling centre that functions to regulate the formation of the cusps of the developing tooth

24
Q

describe the change from cap to bell stage in the tooth formation

A
  • ectomesenchymal cells continue to accumulate, particularly by the invagination of the cap
  • dense condensation beneath the cap is known as the dental papilla
  • accumulation encircling the dental papilla and the enamel organ is the dental follicle
  • as the enamel organ grows, the invagination deepends, forming the cervical loop where the inner and outer enamel epithelium meet
25
Q

what is the stratum intermedium formed by

A

epithelial cells between the stellate reticulum and the inner enamel epithelium that differentiate into a layer of spindle shaped cells - this is the stratum intermedium

26
Q

function of the stratum intermedium

A

glycogen storage

27
Q

what does the bell shaped structure of the enamel organ represent

A

the shape of the crown of the tooth

28
Q

what happens in the late bell stage of the enamel formation

A

future shape of the crown is determined

29
Q

what happens to the stellate reticulum in the bell stage

A

collapses to reduce the distance between the inner and outer enamel epithelium

30
Q

what forms odontoblasts

A

dental papilla

31
Q

what forms ameloblasts

A

inner enamel epithelium

32
Q

what happens to the dental lamina as the ameloblasts and odontoblasts are secreting their mineralised matrixes

A

it disintegrates to detach the tooth germ from the oral epithelium

33
Q

what does the disintegration of the dental lamina lead to

A

epithelial pearls being left over, which can give rise to supernumerary teeth, odontoma and eruption cysts

34
Q

when does root formation begin

A

after crown development

35
Q

describe root formation

A
  • cervical loop cells proliferate downward to form HERS
  • HERS migrates downward to guide root formation and induce the differentiation of odontoblasts
  • limited growth potential determines the length of the root
  • distintegration of hers leads to rests of malassez, which allows cells of the dental follicle to come in contact with root dentine and their differentiation into cementoblasts
36
Q

what forms periodontal ligament

A

fibroblasts which differentiate from the dental follicle cells

37
Q

what does the dental follicle give rise to

A

fibroblasts and osteoblasts to form the periodontal ligament and alveolar bone

38
Q

describe development of the permanent teeth

A
  • extension of a tiny bit of dental lamina behind the deciduous tooth bud
  • this is the successional lamina
  • gives rise to all permanent teeth except the molars
  • dental lamina in the posterior regions of the jaw bury into the oral epithelium and give off tooth buds that undergo the same stages of development as deciduous tooth buds
39
Q

what forms the enamel organ

A

dental placodes

40
Q

what process allows formation of ameloblasts and odontoblasts

A

histodifferentiation

41
Q

when do the permanent molars develop

A

from week 20 to five years after birth

42
Q

where do the permanent molars develop from

A

directly from the dental lamina

Revision (48 decks)

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