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Oral Biology > Dental Development > Flashcards

Dental Development Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

What are the 3 primary embryonic layers

A

Ectoderm
Mesoderm
Endoderm

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2
Q

What are the tooth structures derived from

A

Enamel is derived from ectoderm

All other parts of the teeth and supporting structures are derived from the endoderm

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3
Q

What is the ectomesenchyme

A

Part of the neural crest that develops beside the ectoderm

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4
Q

What do teeth develop from

A

Tooth germs

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5
Q

Where does the neural crest form

A

Between the neural tube and the ectoderm

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6
Q

Describe the movement of neural crest cells

A

Migrate towards the front from dorsal portion to ventral portion

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7
Q

What is mandibulofacial dysostosis

A

Failure of ectomesenchymal cells to migrate

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8
Q

What are common signs of mandibulofacial dysostosis

A

Distance between pupils becomes greater
Ears are positioned lower
Malformation of the ears
Maxilla and mandible small in relation to the skull which relates to crowding of the teeth

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9
Q

What are the stages of tooth development

A 
Initiation
Morphogenesis
Cytodifferentiation
Matrix secretion
Root formation
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10
Q

When does tooth initiation occur

A

5-6 weeks

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11
Q

Describe the events of tooth initiation

A

Mandibular processes seam together in the midline to form the mandible
Maxillary processes will seam with the frontal nasal process, working the nose

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12
Q

When does the primary epithelial band develop and what does it appear as

A

6 weeks

Appears as thickening in epithelium of embryonic mouth (stomodeum)

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13
Q

What does the primary epithelial band form

A

Vestibular lamina, which will break down to form the buccal sulcus
Dental lamina, from which the enamel organ develops

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14
Q

When does the dental lamina develop

A

7 weeks

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15
Q

Describe the dental lamina

A

Horseshoe shaped structure with regions of thickness called tooth germs

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16
Q

When does the bud stage occur

A

8-10 weeks

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17
Q

Describe the events of the bud stage

A

Dental lamina thickens into a bud stage enamel organ

An ectomesenchymal condensation appears, this is the dental papilla

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18
Q

When does the cap stage occur

A

11 weeks

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19
Q

Describe the events of the cap stage

A

The enamel organ forms a cap over the papilla made from the external enamel epithelium and the internal enamel epithelium
The EEE and IEE meet at the cervical loop

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20
Q

What are placodes

A

Embryonic structures that give rise to structures such as hair follicles, feathers and teeth
Different ways that a tissue will form its bud stage

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21
Q

What is hypohidrotic ectodermal dysplasia

A

A genetic skin disease that can cause absence of teeth and hair

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22
Q

Why are both hair follicles and teeth affected by hypohidrotic ectodermal dysplasia

A

The dental placodes are formed from the same process as the hair follicle placodes

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23
Q

How can genetic disorders be cured

A

By gene therapy, the condition may be reversed

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24
Q

When does the bell stage occur

A

14 weeks

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25
Q

What are the 4 cell layers of the enamel organ during the bell stage

A

Stellate reticulum
Stratum inter medium
External enamel epithelium
Internal enamel epithelium

26
Q

What is the purpose of the stellate reticulum

A

Holds the energy, materials and sugars necessary for the ameloblasts to develop the enamel matrix

27
Q

Where do odontoblasts acquire their nutrients from

A

The dental papilla

28
Q

Describe the pattern in which the crown is formed

A

Differentiation starts at the incisal region and then proceeds towards the cervical loop
Matrix formation will follow the differentiation of those cells

29
Q

Describe the stages of permanent tooth germ formation

A

At 12 weeks, an extension will appear on the lingual side of the dental lamina - the permanent successor
At 16 weeks, the first permanent molar starts to develop in a backwards extension of the dental lamina

30
Q

Why does the permanent first molar develop in the way it does

A

It doesn’t have a deciduous counterpart

31
Q

When does the late bell stage occur

A

18 weeks

32
Q

Describe the late bell stage

A

Crown shape is well defined

Apposition of enamel and dentine begins

33
Q

Describe the key events in the formation of dentine and enamel

A

Dental papilla cells adjacent to the IEE differentiate into odontoblasts
Odontoblasts lay down dentine matrix, which is later mineralised
Once dentine formation has begun, IEE cells differentiate into ameloblasts which form enamel

34
Q

What is the purpose of stem cells in dentinogenesis

A

Will be responsible for the formation of tertiary dentine if the odontoblasts die

35
Q

What happens in dentinogenesis

A

Odontoblasts differentiate from dental papilla cells
Dentine matrix is deposited (mainly collagen)
Unmineralised dentine is predentine
Dentine is mineralised by hydroxyapatite

36
Q

What happens in enamel formation

A

Protein matrix is deposited which is partially mineralised (30%)
Once this framework is established, the organic part is removed and mineralisation is completed (maturation)
The ameloblasts change form and function several times during amelogenesis

37
Q

What are the stages of ameloblast differentiation

A 
Morphogenic
Histodifferentiation
Secretory (initial)
Secretory (tomes process)
Maturative (ruffle-ended)
Maturative (smooth)
Protective
38
Q

Describe the position of ameloblasts during differentiation

A

In early stages they’re closer to the cervical region

In later stages they’re closer to the cusp

39
Q

What happens during the initial stages of ameloblast differentiation

A

Dentine induces IEE cells to differentiate into ameloblasts
They elongate, becoming columnar
The nucleus migrates to the basal end of the cell (away from the ADJ)

40
Q

What happens during the secretory phase of ameloblast differentiation

A

Ameloblasts become secretory cells
They synthesis and secrete the enamel matrix proteins (amelogenins)
The matrix is partially mineralised (30% mineral as seeded crystallites)

41
Q

What happens during the maturation phase of ameloblast differentiation

A

Most of the matrix proteins are removed

Mineral content of enamel is increased

42
Q

What happens during the protection phase of ameloblast differentiation

A

Ameloblasts regress to form a protective layer - the reduced enamel epithelium
Involved in eruption and formation of epithelial attachment

43
Q

What is amelogenesis imperfecta and what is it caused by

A

A group of genetic conditions where the enamel fails to develop properly
Caused by a mutation in the MMP20 gene which provides instruction for making enamelysin

44
Q

Describe a radiograph of a patient with amelogenesis imperfecta

A

Can’t tell when enamel stops and dentine starts because enamel has lost so much mineral content so it becomes very similar to dentine

45
Q

What is dentinogenesis imperfecta

A

Dentine is not developed or mineralised to the level that it should be

46
Q

Describe a radiograph of a patient with dentinogenesis imperfecta

A

Cannot see the pulp

47
Q

Why is the root formed last

A

Need to have the correct shape, arrangement and cervical loop before the root is formed

48
Q

What happens to the cervical loop in root formation

A

Apical growth of the cervical loop which becomes Hertwig’s epithelial root sheath - a 2 cell-layered structure

49
Q

Describe how root formation occurs

A

HERS induces formation of root dentine
Then HERS breaks up as there is no enamel in the root
Remainder of HERS persists as ‘debris of Malassez

50
Q

How is the cementum formed

A

The breakdown of HERS allows the follicle to come into contact with dentine
Mesenchymal cells from the follicle contact the dentine and differentiate into odontoblasts
Fibres from the developing PDL are embedded in the cementum - Sharpey’s fibres

51
Q

What may happen to the debris of Malassez

A

May produce a cyst

Because they are associated with odontogenesis they are called odontogenic cysts

52
Q

Name the type of tissue, origin and products of the enamel organ

A

Epithelium
Ectoderm
Enamel

53
Q

Name the type of tissue, origin and products of the dental papilla

A

Ectomesenchyme
Neural crest
Dentine and pulp

54
Q

Name the type of tissue, origin and products of the dental follicle

A

Ectomesenchyme
Neural crest
Cementum, PDL and part of the alveolar bone

55
Q

What are the different types of teeth developmental abnormalities

A

Prenatal
Postnatal
Inherited
Acquired

56
Q

What can teeth development abnormalities have an effect on

A 
Number 
Shape
Size
Structure
Eruption
57
Q

What is germination

A

Teeth that are together because a tooth has broken down into two

58
Q

What is fusion

A

When teeth have joined together

59
Q

What is concrescence

A

When teeth get together by the cementum

60
Q

What type of epithelium is found in the primary epithelial band

A

Stratified squamous

Oral Biology (12 decks)

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