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PTD Beatriz > Chapter 8 B: Teeth Embryological Development > Flashcards

Chapter 8 B: Teeth Embryological Development Flashcards

1
Q

Pathologies in the dental organ are caused by?

A

Disorders in the odontogenesis

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2
Q

What are the characteristics of odontogenesis that differeinate it from other organs?

A
  • its a very long and dynamic process
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3
Q

Very long process:

A

Because it ranges from earlier development embryonic stadiums to practically adolescence

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4
Q

Dynamic process:

A

It requires complex interactions between structures in development, constant interaction with the environment, the process is then very sensitive to embryological aggressions, manifesting itself in different pathologies

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5
Q

The stomodeum is

A
  • the development of the primitive cranium and the oronasal cavity
  • the primitive oral pit or stomodeum is the invagination of the surface epithelium positioned anteriorly between the forebrain and the adjacent centrally developing heart
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6
Q

During the 3rd prenatal week, the deep end of the oral pit is lined with ____, which is in close contact with the ____ of the foregut

A

Ectoderm, endoderm

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7
Q

The area of contact between the two epithelia (ecto and endoderm) is called

A

Oropharyngeal membrane

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8
Q

The Oropharyngeal membrane then disintegrates to create an?

A

Anterior external opening of the gastrointestinal tract in the 4th week of life

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9
Q

The ectoderm is?

A

The outermost layer of the embryo

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10
Q

Mesoderm is?

A

Intermediate, is one of the three cell layers constituting the embryo

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11
Q

The endoderm is?

A

The inner tissue layer of the three layers in which divides the tissues of the embryo

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12
Q

When does the face develop? and from what?

A

During the fifth to seventh week of uterine life , from four primordia that surround a central depression (the primitive oral pit) and develop different parts of our face

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13
Q

The facial primordia are?

A
  • frontal process
  • maxillary process
  • mandibular arch or prominence
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14
Q

The frontal process is ?

A

A single process located above the oral pit

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15
Q

The maxillary processes are?

A

2, located lateral to the oral pit

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16
Q

The mandibular arch or prominence is?

A

Located below the oral pit

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17
Q

Where do the two maxillary processes arise from?

A

The first pharyngeal arch

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18
Q

The mandibular process gives rise to?

A

The mandible, the lower part of the face, and the body of the tongue

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19
Q

The upper face arises from the ?

A

Frontal process

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20
Q

The two maxillary processes will form the ?

A

Cheeks and most of the upper lip

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21
Q

The 20 primary and 32 permanent teeth develop from the interaction of?

A

The oral epithelial cells and the mesenchyme

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22
Q

What are the 3 stages of tooth development ?

A

Bud, cap, bell

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23
Q

The oral epithelial cells come from?

A

Enamel organ
EPC EO

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24
Q

The mesenchyme cells come from?

A

Dental papilla
MC DP

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25
Q

Enamel develops from the ?

A

Enamel organ
OPC E EO

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26
Q

Dentin develops from the?

A

Dental papilla

MC D DP

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27
Q

What other cells other than the oral epithelial cells and the mesenchymal cells contribute to the tooth development?

A

Neural crest cells

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28
Q

What is the first sign of tooth formation ?

A

The development of dental lamina rising from the oral epithelium

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29
Q

After primary teeth develop from the buds, the leading edge of the lamina continues to grow to develo the permanent teeth, this part of the lamina is called?

A

Successional lamina

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30
Q

How many of the permanent teeth replaces the 20 primary teeth ? and how many molars develop behind the primary dentition ?

A

20
12

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31
Q

What are the last teeth to develop and when do they develop?

A

Third molars, 15 years after birth

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32
Q

Which teeth do not succeed primary teeth?

A

Molars

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33
Q

What do the molars form from (the general/successional lamina)?

A

The general lamina

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34
Q

What forms the general and the successional lamina?

A

The initiating dental lamina, and it begins to function in the 6th prenatal week and continues to function until the fifteenth year, producing all 52 teeth

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35
Q

The bud stage?

A
  • rounded, localised growth of epithelial cells surrounded by proliferating mesenchymal cells
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36
Q

The cap stage ?

A

As the rounded epithelial bud enlarges, it gains a concave surface, 11th week
The epithelial cells become the enamel organ
The mesenchyme cells the dental papilla which becomes the dental pulp
The tissue sounding these 2 structures is the dental follicle

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37
Q

The bell stage?

A

The tooth reaches morphodifferentiation and histodifferentiation , 14th week
The inner enamel epithelial cells are characterised by the shape of the tooth they form
The cells of the enamel organ have differentiated into the outer enamel epithelial cells (which cover the enamel organ) and the inner enamel epithelial cells (which becomes the ameloblasts that form the enamel of the tooth
And there’s the Stellate reticulum and stratum intermedium cells
Cells in the periphery of the dental papilla become odontoblasts (they differeinate from mesenchymal cell), the odontoblasts form predentin then after 24 hours dentin
After enamel organ is differentiated the dental lamina begins to degenerate by lysis

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38
Q

Where do the stratum intermedium cells lie and what is their function?

A

Adjacent to the IEE
Assist the ameloblasts in the formation of enamel

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39
Q

What is the function of the OEE?

A

To organise a network of capillaries that will provide the ameloblasts with nutrition

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40
Q

Which process happens first, amelogenesis or dentinogenesis?

A

Dentinogenesis

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41
Q

The dental papilla then forms into the ?

A

Dental pulp

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42
Q

As the odontoblasts move pulpward, the cell process known as? Elongates

A

Odontoblast process

43
Q

The dentinal matrix is first a mesh work of collagen fibers then within 24 hours it?

A

Calcifies

Before calcification: pre dentin
After: dentin

44
Q

Where do the odontoblasts maintain their elongating processes?

A

In the dentinal tubules

45
Q

Where is the site of initial formation?

A

Cusp tips

46
Q

What are the 2 phases of dentinogenesis?

A

Predentin and dentin

47
Q

Dentinogenesis steps?

A

Collagen matrix formation then the deposition of calcium phosphate crystals in the matrix

48
Q

The initial calcification appears as ___ then they coalesce until the matrix is?

A

Crystals, calcified

49
Q

What is the only part that is uncalcified?

A

The newly formed band of dentinal matrix along the pulpal border

50
Q

When do ameloblasts begin enamel deposition?

A

After a few micrometers of dentin have been deposited at the DEJ

51
Q

When do the cells of the IEE differntiate ?

A

Bell stage , they elongate and are ready to be active secretory ameloblasts

52
Q

The 5 functional stages are?

A
  1. Morphogenesis
  2. Organisation and differentiation
  3. Secretion
  4. Maturation
  5. Protection
53
Q

What are the short conical processes that develop at the apical end of the ameloblasts during the secretory stage?

A

Tome’s processes

54
Q

What are the junctional complexes that appear at the junction of the cell bodies and tome’s processes and maintain contact between adjacent cells?

A

Terminal bar apparatus

55
Q

What establishes the DEJ?

A

The fist enamel deposited on the surface of dentin

56
Q

Does the center of the rod form at the same time as the rod walls?

A

No, causes an indent

57
Q

What happens when ameloblasts begin secretion?

A

The overlying cells of the stratum intermedium change in shape from spindle to pyramidal

58
Q

What holds the ameloblasts and the stratum intermedium together?

A

Desmosomes

59
Q

What do the substance needed for enamel production that arrive via blood vessels pass through ?

A

Stellate reticulum, to the stratum intermedium and ameloblasts

Which produces the protein Amelogenin

60
Q

The initial deposition of mineral amounts to ___% of the total enamel

A

25
The other 70% is due to a growth of the crystal
5% of enamel is water

61
Q

Which is the first enamel mineralised?

A

The first matrix deposited

62
Q

Matrix formation and mineralisation continue

A

Peripherally to the tips of the cusps
Laterally to the side of the crowns

63
Q

What is the last region of the crown to mineralise?

A

The cervical region , during this process, protein of the enamel changes or matures and is termed enamel

64
Q

The mineral content of enamel is?
Dentin?

A

95
69

65
Q

What is the most highly calcified tissue in the human body?

A

Enamel

66
Q

Because of the high mineral content of enamel?

A

Almost all water and organic materials are lost during maturation

67
Q

Does mineralisation of the enamel continue after teeth eruption?

A

Yes

68
Q

What happens after the ameloblasts have completed their contributions to the mineralisation phase?

A

They secrete an organic cuticle on the surface of the enamel (developmental or primary cuticle)

69
Q

How do the ameloblasts attach themselves to the primary cuticle?

A

Hemidesmosomes

70
Q

Difference between desmosomes and hemidesmosomes ?

A

Desmosomes: attaching a cell to an adjacent cell
Hemidesmosomes: attaching a cell to a surface membrane

71
Q

The hemidesmosomes attachment plaque is developed by the ameloblast and this stage of plaque formation and attachment is known as?

A

Protective stage of ameloblast function

72
Q

The reduced enamel epithelium is formed by?

A

The ameloblasts shorten and contact the stratum intermedium and other enamel epithelium

73
Q

Where do the IEE and OEE join to form the root sheath?

A

Cervical region or base of enamel organ

74
Q

When the crown is completed, cells in this region of the enamel organ continue to grow, forming a double layer of cells called?

A

Epithelial root sheath or Hertwig’s root sheath

75
Q

The inner layer of the root sheath forms from?

A

The IEE or ameloblasts

76
Q

In the root, these cells induce odontoblasts of the dental papilla to differntiate and form?

A

Dentin

77
Q

Where does the root sheath originate?

A

At the point that enamel deposits end

78
Q

The length , curvature, thickness, and the number of roots depend on?

A

The inner root sheath cells

79
Q

As the formation of root dentin takes place, cells of the outer root sheath function in?

A

Deposition of intermediate cementum

80
Q

Intermediate cementum?

A

A thin layer of acellular cementum that covers the end of dentinal tubules and seals the root surface

81
Q

Then the outer root sheath cells disperse into small clusters and move away from the root surface and are called?

A

Epithelial rests

82
Q

At the proliferating end, the root sheath bends at a 45 degree angle , this area is called?

A

Epithelial diaphragm

83
Q

What does the epithelial diaphragm encircle?

A

The apical opening of the dental pulp during root development

84
Q

Pulp proliferation zone is ?

A

In pulp adjacent to the epithelial diaphragm , cellular proliferation occurs

85
Q

The root thickness until the apical opening is restricted to?

A

1-3mm which is enough to allow neural and vascular communication between the pulp and the periodontium

86
Q

Cementoid is?

A

Non calcified cementum that soon calcifies into mature cementum

87
Q

Which set of teeth require less time to develop?

A

Primary

88
Q

When do permanent teeth begin formation ?

A

At or after birth

89
Q

Primary teeth function in the mouth for ?

A

8.5 years

90
Q

These 8.5 years can be divided into 3 periods:

A
  1. Crown development and root development: 1 year
  2. Root maturation and root resorption: 3.75 years
  3. Shedding of teeth: 3.5 years
91
Q

The movements related to coach eruption begin during crown formation and require adjustments relative to the forming of bony crypt, this is what phase?

A

Preeruptive phase

92
Q

Tooth eruption is also involved in the initiation of root development and continues until the tooth’s emergence into the oral cavity, and the teeth continue to erupt until they reach incisal or occlusal contact, this is which phase?

A

Pre functional eruptive phase

93
Q

Then they develop functional eruptive movements, which include compensation for jaw growth and occlusal wear of the enamel, this is which phase?

A

Functional eruptive phase

94
Q

So the 3 phases of teeth eruption are?

A
  • pre eruptive phase
  • pre funcional eruptive phase
  • functional eruptive phase
95
Q

Pre eruptive phase:

A
  • includes all the movements of the primary and permanent tooth crowns
  • phase is finished with early initiation of root formation
  • the developing crowns move constantly
  • the permanent anterior teeth begin developing lingual to the insical level of the primary teeth
  • then as the primary teeth erupt, the permanent successors are positioned lingual to the apical third of their roots
  • except molars that have no primary predecessors
96
Q

Pre functional eruptive phase:

A
  • starts with initiation of root formation and ends when the teeth reach occlusal contact
    4 major events occur in this phase: root formation, movement, penetration, intraoral occlusal or incisal movement
97
Q

Root formation:

A
  • first step is proliferation of the epithelial root sheath
    Inc in fibrous tissue
98
Q

Movement:

A

Inicisally or occlusally through bony crypt of the jaws to reach oral mucosa
REE fuses with oral epithelium

99
Q

Penetration :

A

Only the organic developmental cubical covers the enamel

100
Q

Intraoral occlusal or incisal movement

A

Erupting tooth continues until clinical contact
Increasing apical shift of the gingival attachment

101
Q

Possible cause of tooth eruption?

A

-most frequent? Root growth, and pulpal pressure
- other causes: cell proliferation, increased vascularity, increased bone formation around teeth
- endocrine influence, vascular changes,enzymatic degradation

  • most important ones: elongation of the root, modification of the alveolar bone and periodontal ligament
102
Q

6/4 rule?

A

For every 6 months of age, 4 teeth erupt

6,4
12,8
18, 12
24, 16
30,20

103
Q

Appearance in the oral cavity of primary teeth?

A

MONTHS
LCI 6-8
UCI 7-10
ULI 8-11
LLI 8-13
UFM 12-15
LFM 12-16
UC 16-19
LC 17-20
LSM 20-26
USM 25-28

104
Q

Appearance in oral cavity of permanent teeth?

A

YEARS
LFM 6-7
UFM 6-7
LCI 6-7
UCI 7-8
LLI 7-8
ULI 8-9
LC 9-10
UFPM 10-11
LFPM 10-11
USPM 10-12
LSPM 11-12
UC 11-12
LSM 11-12
USM 12-13
LTM 17-20
UTM 18-20

PTD Beatriz (9 decks)

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