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3RD yr- CCD1- Anatomy > Initiation and crown development > Flashcards

Initiation and crown development Flashcards

1
Q

Name the different stages of tooth development n

A
  1. Primary epithelial band splits into vestibule lamina and dental lamina
  2. Dental lamina progresses into BUD stage
  3. Cap stage
  4. Early bell stage
  5. Late bell stage
  6. Root development
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2
Q

What does the dental lamina dictate

A

It maps out where the upper and lower dental arches form

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3
Q

While the tooth is developing what other changes are happening

A
  1. A plate of bone is forming below the tooth germ- the lateral plate of the mandible
  2. . Bone of the jaw form denovo within the mesenchyme- intramembranous bone
  3. second, medial, plate of bone will develop to form a trough in which the tooth germs are contained
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4
Q

Name the cartilage found in the mandible

A

Meckels cartilage

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5
Q

Where us the tooth germ contained

A

A trough of bone

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6
Q

What happens to the trough of bone where the tooth germ sits during development

A

The trough will become subdivided by cross plates of bone to form individual sockets

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7
Q

As the jaw is developing what is happening to the tooth

A

The enamel organ has started to grow in to the beginnings of a cap shape marking out where the primary cusps of the toot will from

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8
Q

Has histogenesis started in the cap stage

A

Yes

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9
Q

What is hostogeneisis

A

More than one cell type making up the enamel organ

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10
Q

Describe the ectomesenchyme in the cap stage

A

It has proliferated to form a dose condensation in and around the enamel organ

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11
Q

What is the dental papilla

A

The part enclosed by the enamel organ

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12
Q

What is the dental follicle

A

The part surrounding the enamel organ

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13
Q

What does the dental papilla eventually form

A

The dentine and pulp

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14
Q

What does the dental follicle eventually form

A

The periodontal ligament and cementum

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15
Q

Where does the enamel organ proliferate as it develops

A

Proliferates downwards to enclose more of the mesenchyme

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16
Q

Describe the later cap stage

A
  1. Beginnings of the socket are evident
  2. Bone surrounds tooth germ
  3. Further histogenesis
  4. Enamel organ has grown
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17
Q

Describe the histogenesis of the later cap stage

A

Distinct inner layer of columnar cells- inner enamel epithelium
Cuboidal cells forming the ‘outer’ envelope termed -outer enamel epithelium

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18
Q

What is the inner enamel epithelium

A

Distinct inner later of columnar cells

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19
Q

What is the outer enamel epithelium

A

Cuboidal cells forming the outer envelope

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20
Q

What is the bulk of the enamel organ made up of in the later cap stage

A

Stellate reticulum

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21
Q

What is the stellate reticulum

A

Loose stellate cells

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22
Q

Name the 2 transitionary structures found in the enamel organ during the late cap stage

A
  1. Enamel knot

2. Enamel septum

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23
Q

What is the significance of the name knot

A

Recent studies show it may have a important role in interacting with the mesenchyme in cuspal initiation and initial control

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24
Q

What is the significance of her enamel septum

A

May be site where cell diction is occurring to proceed more cells fro the stellate reticulum as it enlarges

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25
Q

name the most significant development of the later cap stage

A

The down growth lingually of a branch of the dental lamina

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26
Q

What is the significance of the downward growth of the dental lamina

A

It develops the bud of the permanent tooth

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27
Q

What happens to the enamel organ as tooth developing continues into the bell stage

A

The enamel organ develops such that the inner enamel epithelium is more pronounced and has a shape that resembles a bell
Shape of the incisal edge or cusp of teeth are clearly outlines

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28
Q

What does the junction between the inner enamel epithelium and the adjacent papilla map out?

A

The future amelo-dentinal junction (ADJ).

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29
Q

Describe the cells of the inner enamel epithelium in the bell stage

A

They are more elongates especially at the top of the cusps

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30
Q

Which part of a developing tooth is the most mature

A

The cusps

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31
Q

What is happening to the outer cells of the papilla during the bell stage

A

They are beginning got differentiate into odontoblasts

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32
Q

What do odontoblasts do

A

They produce dentine

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33
Q

Name the least mature part of a developing tooth

A

The cervical loop

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34
Q

How do we know the cervical loop is the least mature area of a developing tooth

A

As the inner enamel epithelium cells are still cuboidal

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35
Q

Describe the stellate reticulum in the bell sage

A

They have grown and become more uniform

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36
Q

What is the part surrounding the enamel organ called?

A

Dental follicle

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37
Q

What is the part enclosed by the enamel organ called

A

Dental papilla

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38
Q

What is the bulk of the tooth made up of in the bell stage

A

A matrix rich in glycosaminiglycans (GAGs)

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39
Q

Wha too glycosaminiglycans (GAGs) attract

A

Attracts hate and makes the enamel organ relatively turgid

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40
Q

What new layer of cells develops in the early bell stage

A

A single or double layer of cells lying adjacent to the base of the inner enamel epithelium cells called the ‘stratum intermedium’.

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41
Q

What is the stratum intermedium

A

A single or double layer of cells lying adjacent to the base of the inner enamel epithelium cells

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42
Q

What is the significance of the stratum intermedium

A

Appear to be important in the final differentiation of the inner enamel epithelium cell into ameloblasts

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43
Q

What do ameloblasts do

A

They produce enamel

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44
Q

Describe the jaw as the tooth forms into the early bell stage

A

Both lateral and medial plates are present alongside a considerable amount of the body of the mandible

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45
Q

Describe Meckel’s cartilage as the tooth is in the early bell stage

A

Meckel’s cartilage has been reduced in size and displaced by the bone.

46
Q

What significant event has occurred in the later bell stage

A

Dentine matrix has been secreted at the cusp/incisal edge

47
Q

What differentiates the late bell stage from the early bell stage

A

The secretion of dentine matrix

48
Q

How does mineralised dentine appear on a radiograph

A

As snow capped peaks

49
Q

Describe the cells that secrete dentine

A

they are dull elongates functional odontoblasts

50
Q

What is triggered by the production of dentine

A

The cells of the inner enamel epithelium are triggered to terminally differentiate into ameloblasts

51
Q

What happens to the stellate reticulum during the later bell stage

A

They collapse to markedly reduce the distance between the inner enamel epithelium and the outer enamel epithelium

52
Q

Where did the inner enamel epithelium initially receive its nutrients from

A

The vasculature in the papilla

53
Q

What happens to the vasculature in the papilla during the later bell stage

A

The mineralising dentine matrix cuts it off so it can no longer provide nutrients to the inner enamel epithelium

54
Q

Where does the inner enamel epithiun receive its nutrients from during the LATER bell stage

A

Capillaries invaginate the outer enamel epithelium to provide an alternative supply (The papillary layer)

55
Q

What is the papillary layer

A

The capillaries that invaginate the outer enamel epithelium

56
Q

What does the bell stage represent in terms of crown formation

A

It represents the very earliest stage in crown formation

57
Q

In terms of cell development what pattern do we see in developing teeth

A

There is gradient from cusp tip to cervical loop

Most mature teeth are at the cusp tip and least mature at the cervical loop

58
Q

What controls the differentiation of ameolblasts and odontoblasts

A

The conversation between the inner enamel epithelium and the papilla

59
Q

What is the inner enamel epithelium derived from

A

The ectoderm

60
Q

What is the papilla derived from

A

The ectomesenchyme

61
Q

What controls cell morphology in a developing tooth

A

The papilla

62
Q

What brings about mitotic changes in pre ameloblastic and pre odontblastc cells

A

A change in the receptiveness of the papilla cell to signals from the IEE that brings about this change in its mitotic status

63
Q

What events occur when the odotnblasts become full developed

A

They begin to secrete extra cellular matrix long the basal lamina
The basal lamina then subsequent degenerates

64
Q

What does the degeneration of the basal lamina intimate

A

signals the pre amelobalsts to withdraw from the cell cycle

65
Q

What is required for enamel production to occur

A

Dentine production

66
Q

Until when do the ameloblasts secrete enamel matrix

A

Unti the full thickness of the enamel has been secreted

67
Q

What is a cereal parameter in deterring crown morphology

A

Enamel thickness

68
Q

Until when do the odontoblasts secrete dentine

A

They produce dentine throughout the life of the tooth

69
Q

What happens to the basal lamina

A

The position of the basal lamina will be ‘fossilised’ as the amelodentinal junction.

70
Q

What do ectodermal/mesenchymal interactions and tooth development involve

A

Temporary and spatially regulated production of growth factors, their receptors and hox genes

71
Q

Give some examples of growth factors

A

BMP
TGF beta
FGF

72
Q

What are hox genes

A

homeobox GENES

73
Q

What is responsible for controlling tooth type and shape

A

The dental papilla

74
Q

How does the dental papilla determine tooth type and shape

A

By controlling proliferation within the inner enamel epithelium

75
Q

What happens to the enamel matrix once fun thickness has been reached

A

The matrix at the ADJ will begin to mineralise

76
Q

Is the mineralisation of the matrix at the ADJ uniform

A

no there are variations in rate of deposition at any given moment in tim

77
Q

What forms due to the variation in the rate of matrix mineralisation

A

growth line within the enamel

78
Q

Give an example of a growth line found in enamel

A

striae of Retzius.

79
Q

What are the striae of Retzius.

A

Growth lines found oblique to the ADJ and surface

80
Q

what is mature enamel made up of

A

Hydroxyapatite crystals

81
Q

what does the development of enamel start with

A

The secretion of a dense protein matrix

82
Q

What is the initial protein matrix that makes up enamel made up of

A

A protein called amelogenin

Other enamel specific proteins are present in much smaller amounts (<10%)eg enamelin and ameloblastin.

83
Q

Is amelogenin found in mature enamel

A

NO

84
Q

What are diseases involving tooth enamel usually caused by

A

Mutations in the genes coding for the matrix proteins eg amelogenin, enamelin and ameloblastin

85
Q

What happens to the protein matrix of enamel once full thickness has been secreted by ameloblasts

A

The protein matrix is degraded and removed from the tissue (proteolysis)

86
Q

Which cell is responsible for the process of producing enamel, degrading it and then adding mineral to mature it

A

Ameloblasts

87
Q

What are Ameloblasts derived from

A

They are the terminally differentiated form of the cells of the inner enamel epithelium.

88
Q

What changes do the ameloblasts undergo ro preform their function

A

newly differentiated cells are a short columnar shape, approximately 5μm wide and 30μm long with significant amounts of rough endoplasmic reticulum, mitochondria and golgi, Their nucleus is displaced towards the basal end of the cell, away from the AD

89
Q

How are neighbouring ameloblasts cells joined together

A

By desmosomes and gap junctions

90
Q

Where is the matrix secreted from in the amelobalsts

A

Secreted at the apex of the cell towards the ADJ

91
Q

As the ameloblasts migrate what do they do

A

They leave matrix behind

92
Q

What changes do the ameloblsats undergo as they migrate

A

They elongate and their apical ends develop the Tomes process

93
Q

What is the significance of the tomes process

A

Its shape dictates the orientation of the secreted matrix to the ADJ

94
Q

For the bulk of matrix secretion the cells will have what?

A

A tomes process

95
Q

Having a tomes process means what for enamel

A

Means bulk of enamel thickness will be prismatic

96
Q

What stage follows the late bell stage?

A

Transition stage

97
Q

What happens to ameloblasts in the transition stage

A

They decrease in length and become less active
Their tomes processes disappear
20% of cells die from apoptosis

98
Q

What does the loss of tomes process mean for amelobalsts in the transition stage

A

Results in a second thin layer of prismatic enamel being deposited at the surface.

99
Q

Which stage follows the transition phase

A

Maturation phase

100
Q

What happens in the maturation phases

A

The matrix will be totally degraded, removed and replaced by mineral so that hydroxapatite crystals can grow

101
Q

What she does hydroxyapatite start at and what does it end up as

A

Starts as long thin ribbons and ends as large hexagonal crystals

102
Q

How would you describe the process of amturation

A

It is cyclical

103
Q

Why is the process of maturation described as cyclical

A

As cells oscillate between so-called smooth-ended and ruffle-ended forms
With each cycle a little bit more matrix is removed and more mineral is added

104
Q

What happens simultaneously with maturation of cells

A

The pH of the underlying mineralising matrix also changes in acidity

105
Q

Why is a regal change in acidity important during maturation

A

As it is needed for sustained crystal growth

106
Q

What happens to the ameloblsats and other elements of the enamel Organ once maturation of enamel is complete

A

They collapse down to form a layer 2-3 cels thick which covers the surface of the enamel-reduced enamel epithelium

107
Q

what does the collapsing of the ameloblsars following maturation of enamel lead to

A

the reduced enamel epithelium

108
Q

What is the reduced enamel epithelium involved in

A

Tooth eruption and the shedding of deciduous teeth.

109
Q

What is the final act int the formation of enamel

A

The secretion of a thin layer of protein at the enamel surface called the primary enamel cuticle

110
Q

What is the primary enamel cuticle

A

The outermost thin layer of protein found on the enamel surface

3RD yr- CCD1- Anatomy (6 decks)

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