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OCB02 > Root Development & Tooth Eruption > Flashcards

Root Development & Tooth Eruption Flashcards

1
Q

What is the cervical loop?

A

Region where the inner and outer enamel epithelia meet with no stellate reticulum in between

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2
Q

What does the HERS do? (3)

A

Maps out root shape

Induce odontoblast differentiation

Initiates cementum and PDL formation

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3
Q

What type of odontoblasts are formed during the growth of HERS?

A

Root odontoblasts

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4
Q

When does the HERS disintegrate?

A

When root odontoblasts lay down predentin

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5
Q

How does the HERS induce cementum and PDL formation?

A

HERS disintegrates; root odontoblast predentin becomes mineralised

Dental follicle mesenchymal cells contact root dentin triggering differentiation into cementoblasts

Cementoblasts secrete cementum

Fibroblasts will secrete collagen = PDL

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6
Q

What are the two types of cementum and where are they found?

A

Acellular cementum - coronal two-thirds of root

Cellular cementum - apical third of root

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7
Q

Contrast the basic structures of cellular and acellular cementum.

A

Cellular - thicker with cementocytes

Acellular - thin layer

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8
Q

What are the cell rests of Malassez?

A

Persisting clusters of epithelial cells remaining from HERS disintegration

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9
Q

What complications could arise from the cell rests of Malassez?

A

Odontomas

Cysts

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10
Q

Describe the formation of the root apex.

A

At a certain horizontal level, the HERS will change orientation and grow at right angles until they meet and fuse in the centre - epithelial diaphragm

A small gap is left - apical foramen

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11
Q

When does the PDL start to develop?

A

Tooth eruption

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12
Q

What cells secrete the collagen for the PDL?

A

Dental follicle fibroblasts

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13
Q

What do the epithelial layers fuse to become before eruption?

A

Reduced enamel epithelium

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14
Q

*What happens as the tooth makes its way to the oral cavity?

A

Alveolar bone resorbed to form the epithelial canal

REE fuses with oral epithelium

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15
Q

Is there any bleeding when teeth erupt and why?

A

No

Tooth erupts through the epithelial canal

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16
Q

Why is decay of enamel more problematic after tooth eruption?

A

No ameloblasts available to replace enamel

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17
Q

What epithelia form the dento-gingival junction?

A

Oral epithelium

Reduced enamel epithelium

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18
Q

What is the Gubernacular cord?

A

Dental lamina which connects the teeth to the oral epithelium from within the bony crypt

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19
Q

Where does bone resorption start for tooth eruption?

A

Gubernacular cord

20
Q

Why are the roots of deciduous teeth resorbed?

A

No more anchoring so it can fall out and allow permanent teeth to erupt

21
Q

What are the three proposed mechanisms of tooth eruption?

A

Pulling by the PDL

Pushing by root growth

Pushing by alveolar bone remodelling

22
Q

What is the most likely mechanism of tooth eruption?

A

Pushing by alveolar bone remodelling

23
Q

How is bone remodelled during tooth eruption?

A

Resorbed above tooth by osteoclasts

Deposited below tooth by osteoblasts

24
Q

What part of the dental follicle is osteogenic?

A

Basal/apical half

25
Q

What part of the dental follicle is osteoclastic?

A

Coronal half

26
Q

What factor does the osteogenic half of the dental follicle release and what does it do?

A

BMP2

Promotes osteoblast differentiation

27
Q

What tissue controls alveolar bone metabolism?

A

Dental follicle

28
Q

What factors does the osteoclastic half of the dental follicle release and what do they do?

A

M-CSF1 (macrophage colony stimulating factor 1)

RANKL (receptor activator of nuclear factor Kappaβ ligand)

MCP1 (monocyte chemotactic protein 1)

Promote osteoclast differentiation

29
Q

Where is NF1-C expressed and where do defects occur?

A

Crown and root odontoblasts

In root odontoblasts

30
Q

What is the function of NF1-C?

A

Promotes odontoblast differentiation (in root)

31
Q

What is characteristic of NF1-C mutant mice?

A

Rootless teeth

32
Q

What two disorders result in short roots?

A

Dentin dysplasia type 1

Sponastrime dysplasia

33
Q

Which gene is affected in dentin dysplasia type 1?

A

DSPP/dentin sialophosphoprotein gene

34
Q

What is the difference between sponastrime dysplasia and dentin dysplasia type 1?

A

Sponastrime dysplasia also results in short limbs/dwarfism and spinal and facial bone abnormalities

35
Q

What syndrome results in abnormally long roots?

A

OFCD oculo-facio-cardio-dental syndrome

36
Q

What does BCOR usually do?

A

Inhibit methylation of H3K4 and H3K36 to promote odontoblast differentiation

37
Q

What does a mutation in BCOR result in?

A

Methylation of H3K4 and H3K36

Mesenchymal cells do not differentiate so roots keep growing and have an open apex

(OFCD syndrome)

38
Q

What is taurodontism?

A

Failure of HERS to invaginate at the proper horizontal level (epithelial diaphragm forms too late)

39
Q

What syndrome results in taurodontism?

A

Tricho-dento-osseous

40
Q

What are the three types of taurodonts?

A

Hypotaurodont

Mesotaurodont

Hypertaurodont

41
Q

What is different about the teeth in taurodontism? (3)

A

Enlarged pulp chamber

Apical displacement of pulp floor

No constriction at cementoenamel junction

42
Q

What type of mice will have variable root numbers?

A

EDA+/-

43
Q

The loss of what gene would result in single rooted molars?

A

Ezh2 in dental mesenchyme

44
Q

What can mutations in the ectodysplasin pathway result in?

A

Taurodontism

Variable root (and cusp) number

45
Q

What does Ezh2 code for?

A

Histone methyl transferase which methylates H3K27

46
Q

Which pathway determines cusp number?

A

Ectodysplasin pathway

47
Q

Why does the osteoclastic half of the dental follicle secrete chemokines?

A

To recruit monocytic precursors and macrophages to produce osteoclasts

OCB02 (19 decks)

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