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BDS2 BAMS Oral Biology > 6. Tooth Development > Flashcards

6. Tooth Development Flashcards

1
Q

Types of primary embryonic layers (3)

A

Ectoderm
Mesoderm
Endoderm

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2
Q

Definition of ectomesenchyme (2)

A

Part of the neural crest that develops beside the primitive nervous system (ectoderm)
Fourth cell type (also called the neural crest)

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3
Q

From which primary embryonic layers are tooth structures derived (2)

A

Enamel from ectoderm

All others from ectomesenchyme

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4
Q

Cause of mandibular dysostosis

A

Failure of ectomesenchymal cells to migrate

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5
Q

Stages in tooth development (5)

A 
Initiation
Morphogenesis
Cytodifferentiation
Matrix secretion
Root formation
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6
Q

First part of tooth development (3)

A

Development of primary epithelial band
At 6wks iul
Appears as a thickening in epithelium of the embryonic mouth

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7
Q

Second part of tooth development (3)

A

Development of the dental lamina
At 7wks iul
PEB has grown into the jaw and divided into two parts

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8
Q

At 7wks iul, what has the PEB divided into (2)

A 
Vestibular lamina (breaks down to form buccal sulcus)
Dental lamina (from which enamel organ forms)
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9
Q

Third part of tooth development (4)

A

Bud stage, 8-10wks iul
Enamel organ forms
Dental lamina thickens into a bud stage enamel organ
Ectomesenchymal condensation appears (dental papilla)

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10
Q

Fourth part of tooth development (3)

A

Cap stage, 11wks iul
Enamel organ forms a cap over papilla
Cap stage enamel organ is IEE and EEE

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11
Q

Where do IEE and EEE meet

A

At the cervical loop

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12
Q

Fifth part of tooth development (3)

A

Bell stage, 14wks iul
More cell layers differentiated
Tooth shape is being defined

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13
Q

Cell layers of the bell stage enamel organ (4)

A

Stratum intermedium
Stellate reticulum
Internal enamel epithelium
External enamel epithelium

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14
Q

Definition of enamel knot

A

Where cusps, mammelons and cingulums are established

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15
Q

What happens at 12wks iul and what is this

A

Extension appears on the lingual side of the dental lamina

This is the dental lamina for the permanent successor

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16
Q

What happens at 16wks iul (2)

A

First permanent molar germ develops

Develops as a backwards extension of the dental lamina

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17
Q

Sixth part of tooth development (3)

A

Late bell stage, 18wks iul
Crown shape is well defined
Apposition of enamel and dentine begins

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18
Q

Dental papilla cells adjacent to IEE differentiate into

A

Odontoblasts

19
Q

What happens when dentine formation has begun (2)

A

IEE cells differentiate into ameloblasts

Ameloblasts form enamel

20
Q

Process of dentinogenesis (3)

A

Odontoblast differentiation from IEE
Deposition of unmineralised dentine matrix (predestine)
Mineralisation of dentine (hydroxyapatite)

21
Q

Process of ameloblast formation (4)

A

Differentiation
Secretion
Maturation
Regression

22
Q

Stages in ameloblast differentiation (7)

A 
Morphogenic
Histodifferentation
Secretory (initial)
Secretory (Tomes process)
Maturative (ruffle-ended)
Maturative (smooth)
Protective
23
Q

Process of ameloblast differentiation (3)

A

Dentine induces IEE cells to differentiate into ameloblasts
Elongation, they become columnar
Nucleus migrates to basal end of the cell

24
Q

Process of secretory phase (3)

A

Ameloblasts become secretory cells
They synthesise and secrete enamel matrix proteins (amelogenins)
Matrix is then partially mineralised (30%)

25
Q

Process of maturation phase (2)

A

Removal of most matrix proteins

Enamel mineral content increased (95%)

26
Q

Process of protection phase (3)

A

Ameloblasts regress to form protective layer (reduced enamel epithelium)
Involved in eruption
Formation of epithelial attachment

27
Q

Definition of amelogenesis imperfecta, AI

A

Congenital disease, abnormal formation of enamel

Unreleated to any systemic/generalised conditions

28
Q

Cause of AI

A

Malfunction of proteins in enamel due to abnormal enamel formation via amelogenesis

29
Q

Types of enamel proteins (4)

A

Ameloblastin
Enamelin
Tuftelin
Amelogenin

30
Q

Type of condition of AI

A

Autosomal recessive hypoplastic hypomaturation AI

31
Q

Genetics of AI (2)

A

MMP20 gene located on long (q) arm

On chromosome 11, position 22.3

32
Q

Definition of dentinogenesis imperfecta, DI (2)

A

Genetic disorder of tooth development

Dentine dysplasia that causes teeth to be discoloured

33
Q

Causes of DI (3)

A 
Genetic factors (mainly)
Any environmental/systemic upset that impedes calcification or metabolism of Ca
34
Q

Function of enamel organ

A

Map out shape of crown

35
Q

How is the crown shape mapped out

A

Migration of the cervical loop

36
Q

How is the root shape defined (2)

A

By apical growth of the cervical loop

Cervical loop is now called Hertwig’s epithelial root sheath (HERS)

37
Q

Difference between enamel organ and HERS

A

Enamel organ - 4 cell layers

HERS - 2 cell layers (IEE and EEE)

38
Q

HERS induces

A

Formation of root dentine

39
Q

Root formation process (4)

A

Once initial layer of root dentine is formed, HERS breaks up
Remains of HERS persist as debris of Malassez (may develop into a cyst)
Mesenchymal cells from the follicle contact dentine, differentiating into cementoblasts
Fibre’s from developing PDL (Sharpey’s) are embedded into cementum

40
Q

Why does HERS break up so soon

A

No enamel in the root

41
Q

Type of tissue, origin and products for enamel organ (3)

A

Epithelium
Ectoderm
Enamel

42
Q

Type of tissue, origin and products for dental papilla (3)

A

Ectomesenchyme
Neural crest
Dentine, pulp

43
Q

Type of tissue, origin and products for dental follicle (3)

A

Ectomesenchyme
Neural crest
Cementum, PDL, part of alveolar bone

44
Q

Types of tooth development abnormalities (9)

A 
Prenatal
Postnatal
Inherited
Acquired
Number
Shape
Size
Structure
Eruption

BDS2 BAMS Oral Biology (14 decks)

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