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BDS 2 Semester 1 > Odontogenesis > Flashcards

Odontogenesis Flashcards

1
Q

What is odontogenesis?

A

Tooth development; formation, eruption and integration with surrounding tissues.

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2
Q

Stages of odontogenesis

A

Initiation
Bud stage
Cap stage
Bell stage
Apposition
Maturation

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3
Q

Initiation stage of odontogenesis

A
  • NCC migrate to 1st branchial arch
    • Thickening of epithelium on surface of 1st branchial arch
    • Continuous band of thickened epithelium forms around the mouth = primary epithelial band = primitive oral epithelium
    • This epithelium gives rise to the dental (inner/ lingual) and vestibular (outer/ buccal -> becomes the vestibule: proliferation into ectomesenchyme, then rapid degeneration into a cleft) through ingrowth into underlying mesenchymal NCC
    • Thickening of epithelium within the dental lamina forms placodes, from invaginations of epithelium: which eventually form the tooth bud. This occurs due to signalling proteins
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4
Q

Bud stage of odontogenesis

A

Bud stage: around 8 weeks of embryonic development
- Dental lamina grows from placodes into a bud shape = enamel organs, penetrating into underlying ectomesenchyme
- Little change to shape or function of epithelial cells
Cellular density of ectomesenchyme increases (condensation) as epithelial bud proliferates

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5
Q

Cap stage of odontogenesis

A

Cap stage: around weeks 9-10
- Tooth bud grows larger, and into the shape of a ‘cap’ on top of condensed ectomesenchyme = dental papilla (gives rise to dentine and pulp). Dental follicle forms a ‘sac’ around enamel organ
- Dental lamina forms laternal lamina
- Morphogenesis of tooth structure; guided by epithelial and mesenchymal tissues
- Histodifferentiation of epithelial cells; joined by desmosomes as fluid increases in enamel organ, cells forced apart and become stellate. Centre of enamel organ = stellate reticulum
- Enamel knot (transient histological structure) = cluster of non=dividing epithelial cells in the central part of the internal enamel epithelium; forms a bulge in the dental papilla. Number and location of enamel organs = cusps
Stellate reticulum collapses: inner enamel epithelium and outer enamel epithelium become closer

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6
Q

Bell stage of odontogenesis

A

Bell stage: around weeks 11-12
- Tooth germ continues to grow, resembling the shape of a bel
- Morpho differentiation of the crown
- Peripheral epithelial cells (OEE) have cuboidal shape, inner enamel epithelium have a columnar shape. These layers are continuous, and where they meet = cervical loop
- Histodifferentiation of ameloblasts from IEE, odontoblasts from dental papilla, Cementoblasts/osteoblasts/fibroblasts from dental follicle
- Proliferation continues until crown reaches its full size
- Stratum intermedium forms between IEE and stellate reticulum. Spindle (star shaped) cells assist in collapse of stellate reticulum
- Dental lamina disintegrates and detaches from oral epithelium

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7
Q

Apposition stage of odontogenesis

A

Apposition: continues from foetal period, into post-natal life
- Enamel, dentine, cementum and bone deposited in layers
- Organic matrix laid down first at cusp tips and goes downwards
- Vasculature from blood vessels in dental papilla and vessels along periphery of OEE
epithelial cells from outer and inner layers proliferate from the cervical loop to form a double layer = Hertwig’s epithelial root sheath
- Initiates differentiation of odontoblasts for form dentine of root
Root sheath fragments separated from surrounding CT by a basal layer = epithelial rests of Malassez

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8
Q

Maturation stage of odontogenesis

A

Maturation: is complete 2 years post-eruption
Calcification of permanent 1st molar starts shortly after birth

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9
Q

Primary epithelial band

A

= primitive oral epithelium
Continuous band of thickened epithelium that forms around the mouth
Gives rise to the dental and vestibular lamina

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10
Q

What does thickening of epithelium within the dental lamina forms?

A

Thickening of epithelium within the dental lamina forms placodes, from invaginations of epithelium: which eventually form the tooth bud. This occurs due to signalling proteins

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11
Q

Stellate reticulum

A

Histodifferentiation of epithelial cells; joined by desmosomes as fluid increases in enamel organ, cells forced apart and become stellate. Centre of enamel organ = stellate reticulum

Stellate reticulum collapses: inner enamel epithelium and outer enamel epithelium become closer

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12
Q

Enamel knot

A
  • Enamel knot (transient histological structure) = cluster of non=dividing epithelial cells in the central part of the internal enamel epithelium; forms a bulge in the dental papilla. Number and location of enamel organs = cusps
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13
Q

Hertwig’s epithelial root sheath

A

Vasculature from blood vessels in dental papilla and vessels along periphery of OEE
epithelial cells from outer and inner layers proliferate from the cervical loop to form a double layer = Hertwig’s epithelial root sheath

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14
Q

Cervical loop

A

Peripheral epithelial cells (OEE) have cuboidal shape, inner enamel epithelium have a columnar shape. These layers are continuous, and where they meet = cervical loop

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15
Q

Histodifferentiation of different cells during odontogenesis

A

Histodifferentiation of ameloblasts from IEE, odontoblasts from dental papilla, Cementoblasts/osteoblasts/fibroblasts from dental follicle

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16
Q

Epithelial rests of Malessez

A

Root sheath fragments separated from surrounding CT by a basal layer = epithelial rests of Malassez

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17
Q

What does Hertwig’s epithelial root sheath initiate?

A

Initiates differentiation of odontoblasts for forming dentine of root

18
Q

Label the image

A

Black arrow = Meckel’s cartilage
Black dashed circle = tooth germ
Pink dashed circle = dental papilla
Red arrow = dental follicle

19
Q

What stage of tooth development does this image show?

A

Cap stage of odontogenesis

20
Q

What stage of tooth development does this image show?

A

Bell stage of odontogenesis

21
Q

Label the image

A

Black arrow = dental lamina
Red arrow = oral epithelium
Black dashed circle = successional dental lamina
Orange dashed circle = stellate reticulum
Red dashed circle = alveolar bone
Pink dashed circle = dental papilla

22
Q

Label the image

A

green dashed circle = stellate reticulum
orange rectangle = outer enamel epithelium
purple rectangle = inner enamel epithelium
red circle = cervical loop
pink circle = dental papilla

23
Q

Label the image

A

red circle = stellate reticulum
purple rectangle = stratum intermedium
green rectangle = inner enamel epithelium
blue star = accellular zone
black circle = dental papilla

24
Q

What stage of tooth development does the image show?

A

(late) bell stage of odontogenesis/ apposition

25
Q

Label the image

A

red arrow = stratum intermedium
black arrow = ameloblasts
blue star = pre-dentine
yellow arrow = odontoblasts
red circle = stellate reticulum

26
Q

What stage of tooth development does the image show?

A

late bell stage

27
Q

Label the image

A

red arrow = enamel matrix
black arrow = dentine
blue star = enamel space
yellow arrows = cervical loop
red circle = dental pulp

28
Q

Label the image

A

red arrow = stratum intermedium
black arrow = ameloblasts
red circle = enamel matrix
blue star = enamel space
yellow arrow = dentine

29
Q

What is mesiodens? During what stage of odontogenesis does this condition arise?

A

supernumary tooth between two central incisors
arises during initiation stage of odontogenesis

30
Q

What is microdontia? During what stage of odontogenesis does this condition arise?

A

teeth that are smaller than normal
arises during bud stage of odontogenesis

31
Q

What is dens in dente? During what stage of odontogenesis does this condition arise?

A

‘tooth within a tooth’
arises during cap stage of odontogenesis

32
Q

What is tubercle? During what stage of odontogenesis does this condition arise?

A

projection of ‘extra’ enamel in a tooth crown
arises during cap stage of odontogenesis

33
Q

What is amelogenesis imperfecta? During what stage of odontogenesis does this condition arise?

A

affected enamel structure and appearance
arises during apposition/ maturation stages of odontogenesis

34
Q

Order/ process of ameloblast/ odontoblast differentiation and secretion

A
  1. Preameloblasts induce dental papilla cells to differentiate into odontoblasts
  2. Predentine is secreted by odontoblasts
  3. The basal lamina between preameloblasts and odontoblasts disintegrates
  4. Preameloblasts differentiate to secretory ameloblasts
  5. Ameloblasts start secreting enamel matrix
35
Q

Enamel shows pits and grooves but does not wear off rapidly. Primary and permanent dentition affected. What condition could this be?

A

Amelogenesis imperfecta - hypoplastic type

36
Q

Teeth with normal contour at eruption but greyish translucent and lost rapidly. What condition could this be?

A

Dentinogenesis imperfecta

37
Q

Enamel has brown and opaque white spots in areas corresponding to dental development at 3-4 years of age. What condition could this be?

A

Fluorosis

38
Q

Enamel relatively normal at the time of eruption but rapidly wears off. What condition could this be?

A

Amelogenesis imperfecta - hypocalcification type

39
Q

Three adjacent teeth fail to erupt and radiographically show thin faintly radiopaque shells. What condition could this be?

A

Regional odontodysplasia

40
Q

What gene encodes for the protein that makes up the bulk of enamel?

A

AMELX (amelogenin)

41
Q

Which of the following molecules is involved in the differentiation of cementoblasts?
Osterix
Osteocalcin
Osteopontin
Osteoprotegerin
Platelet-derived growth factor

A

Osterix

42
Q

Which of the following homeobox genes is associated with the development of molar teeth?
Msx-2
Dix-2
Msx-1
Barx-1

A

Barx-1

BDS 2 Semester 1 (21 decks)

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