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Tooth Development Flashcards

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1
Q

when does tooth development start?

A

5-6 W.I.U

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2
Q

what r the morpholgical stages of tooth development?

A

1-Stage of dental lamina
2-Bud stage
3- Cap stage
4- Bell stage, divided into:
- Early bell stage
(before any hard-dental tissue formation).
- Late or advanced bell stage
(starts when first layer of dentin is formed).

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3
Q

At the age 5-6 W.I.U., the primitive oral cavity, or stomodeum, is lined w/ ??

A

by stratified squamous epithelium
(oral ectoderm)

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4
Q
  • The surface layer consists of ______ cells and a basal layer of ______ cells.
  • The epithelium is separated from the CT by a ________
A

flattened
columnar
basement membrane

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5
Q

What r the Histophysiological Stages of tooth development?

A

1- INITIATION
2- PROLIFERATION
3- HISTO-DIFFERENTIATION
4- MORPHO-DIFFERENTIATION
5- APPOSITION

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6
Q

what happens @ 6th. W.I.U.L.?

A
  • the basal cells proliferate at a faster rate than the adjacent cells
  • forming separate islands in the underlying mesenchyme under the influence of the ectomesencymal cells (neural crest cells)
  • These islands grow to coalesce together forming primary epithelial band which extends along the free margin of the developing jaw
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7
Q

what happens @ 7th W.I.U.L. ?

A

The primary epithelial band divides into two laminae:
- a facially located vestibular lamina
- a lingual dental lamina.

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8
Q

info on dental lamina:

A
  • Sheet-like structure, band or lamina which extends along entire free margin of jaws
  • Permanent successors develop from lingual extension of the dental lamina (successional dental lamina
  • Permanent molars develop from a D extension of the dental lamina
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9
Q

what is the life Span of the dental lamina:

A

The dental lamina is active from
5th WIU
(beginning of development of primary teeth)
To
5 years
(when the 3rd permanent molar is initiated).

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10
Q

info on the bud stage:

A

proliferation of the dental lamina on its labial surface leads to the formation 10 swellings (buds) for the development of the deciduous teeth.

*These buds are called enamel organ (also called dental organ).

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11
Q

The ectomesenchymal cells condensation beneath the enamel organ is cld…

A

dental papilla

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12
Q

The connective tissue-beneath-and around the enamel organ and dental papilla forming what is cld…..

A

dental sac (follicle)

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13
Q

what r the sources of nutrition for the dental organ?

A

dental sac and dental papilla

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14
Q

what forms the tooth germ?

A
  • dental organ
  • dental papilla
  • dental sac
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15
Q

dental organ forms the??

A

enamel

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16
Q

dental papilla forms??

A

dentine and pulp

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17
Q

dental sac forms???

A

-Cementum
-Periodontal Ligament
-Alveolar bone proper

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18
Q

what happens in the cap stage?

A
  • The tooth bud continues to grow.
  • It does not expand uniformly into a larger sphere
  • due to unequal growth in the different parts of the enamel organ leading to a shallow invagination on the deep surface of the bud.
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19
Q

what r the Histological structures of the cap stage??

A

1- Outer enamel epithelium
2- Inner enamel epithelium
3- Stellate reticulum
4-Transitory structures:
A- Enamel Knot
B-Enamel cord
5-Dental papilla
6-Dental sac

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20
Q

what is the only component that arises from ectodermal tissue?

A

enamel organ

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21
Q

talk about Outer enamel epithelium (O.E.E):

A
  • Single layer of cuboidal epithelial cells
  • w/ deeply stained rounded nucleus
  • It forms the outer convex surface of the enamel organ.
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22
Q

rant on the inner enamel epithelium (I.E.E)

A
  • it consists of a single layer of columnar epithelium
  • w/ deeply stained nucleus
  • arranged at the concave surface of the enamel organ.
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23
Q

Stellate reticulum…

A

*It occupies the central portion of the enamel organ between its outer and inner enamel epithelia.

  • It consists of several layers of branching star shaped cells.

*Their branches anastomose with those of adjacent cells and w/ the outer and inner enamel epithelia forming desmosomes

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24
Q

The intercellular spaces are rich in
____________ which are _______

A

Glycosaminoglycans (GAGs)
hydrophilic

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25
Q

talk about the enamel knot

A
  • It is a localized cellular condensation in the region of the inner enamel epithelium, @ center of the tooth germ.
  • It disappears before enamel formation.
  • It controls cuspal morphogenesis.
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26
Q

who is zat Enamel cord?

A

it appears as a strand of cells running from the enamel knot to the O.E.E.
* It disappears before enamel formtn
* It may give rise to stallate reticulum

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27
Q

what r the Transient Structures in the Cap Stage?

A

Enamel Knot and Enamel Cord

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28
Q

what is the Dental papilla??

A

The ectomesenchymal cells condensed beneath the enamel organ form dental papilla.

The cells of this layer show remarkable division and condensation.

It is separated from the inner enamel epithelium by a cell free zone.

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29
Q

The ______ part of the dental papilla appears _____ cells but contains their cytoplasmic processes and fine argyrophilic fibers. This layer is cldd _____ or acellular zone.

A

peripheral
free from
cell free zone

30
Q

Dental sac?!

A

is the condensation of the ecto- mesenchymal cells and fibers surrounding the enamel organ and dental papilla.

31
Q

what is the role of the transient structures?

A
  • determining the cusp position in molars
    or
  • may give the stratum intermedium in the bell stage.
32
Q

@ what age does the cap stage occur??

A

occurs for the primary dentition between 9th and 10th w.i.u.

33
Q

The vestibular lamina???

A

It is formed of ectodermal proliferation into the underlying ectomesenchyme buccal to the dental lamina.

Epithelial degeneration occurs inside the vestibular lamina to form the oral vestibule separating the cheek & lip from the teeth bearing area in both mandible and maxilla.

34
Q

what arises from Lateral Dental Lamina??

A

Deciduous Teeth

35
Q

what arises from Successional Dental Lamina?

A

Permanent Successors

36
Q

how does the Permanent Molars arise in the dental arch?

A

From Distal Extension After The 5th Tooth from the Main Dental Lamina

37
Q

in Early bell stage:
hard dental tissues is ____

and in Late bell stage:
hard dental tissue is ____

A

absent
present

38
Q

TRUE OR FALSE: Once the first layer of dentin is laid down it becomes advanced or late bell stage.

A

TRUE

39
Q

in early bell stage:

the decid. dental organ is connected to main dental lamina (which is connected to the oral epithelium) by a _______ cld ________

A

long and narrow epith. connection
lateral dental lamina.

40
Q

in early bell stage:
The main dental lamina will grow ________ to the decid tooth germ forming a __________, giving the tooth germ of the _________ (type of tooth).

A

lingually
successional dental lamina
permanent successors

41
Q

in early bell stage:
The cells of OEE become ______

A

low cuboidal

42
Q

in early bell stage:
IEE show elongation of____ (no.)

A

40 microns

43
Q

what happens in the early bell stage, regarding the IEE?

A

IEE elongation is towards the dental papilla resulting in disappearance of cell-free zone.

44
Q

explain the process of induction:

A

As the I.E.E cells get in contact w/ the peripheral connective tissue cells of the dental papilla, they exert an organizing influence on the undifferentiated mesenchymal cells (UMCs) to differentiate into odontoblasts.

45
Q

rant about the IEE showing alteration in their functional polarity

A

by migration of the nucleus and mitochondria to the proximal end of the cell. At the same time, the Golgi bodies and centrioles migrate to the distal end.

46
Q

what happens to the stellate reticulum in the early bell stage?

A

At this stage the stellate cells expand further apart mainly by the increase of the intercellular fluid.

47
Q
A

Stratum intermedium :
* It is composed of 2-3 layers of flattened cells.
* It is in b2ian I.E.E. and
stellate reticulum.
* This layer is derived from cells inside the enamel organ (IEE) or from enamel knot.
* This layer seems to be essential for enamel
formation as they contain alkaline phosphatase enzyme .

48
Q

another name for cervical loop

A

zone of reflection

49
Q

what happens to the dental papilla in the early bell stage?

A

Differentiation of odontoblasts at the periphery of the dental papilla

50
Q

TRUE OR FALSE: Deposition of the first layer of dentine changes the early bell stage into late bell stage.

A

TRUE

51
Q

What happens to the dental lamina in the late bell stage?

A
  • The lateral dental lamina degenerates by the invasion of the mesodermal cells.
  • Remnants of the dental lamina are cld
    (Serres’ pearls) (Epithelial Rests Of Serres).
52
Q

what are. the names given to the remnants of the dental lamina in the late bell stage?

A

Serres’ pearls
OR
Epithelial Rests Of Serres

53
Q

what happens to the OEE in the late bell stage?

A

The convex surface of the O.E.E. will be folded and elongated.
* Capillary loops appear between the folded epithelium.
* The cells of the O.E.E. becomes flat.

54
Q

The cells of the O.E.E. show criteria of active transporting cells by:

A
  • Microvilli to increase SA
  • Cytoplasmic vesicles for transport.
  • increased mitochondria for energy.
55
Q

what is the name of the process. that changes the IEE to ameloblast?

A

reciprocal induction

56
Q

describe the process of Reciprocal induction:

A
  • Under the influence of the first formed dentin layer
  • the I.E.E. will be differentiated into tall columnar cells
  • which have the power to produce enamel matrix, called Ameloblasts.
57
Q

how r ameloblats attached to each other?

A

They r attached to each other by junctional, complexes laterally + by desmosomes to stratum intermediaum.

58
Q

what happens to the Stellate reticulum in the late bell stage:

A
  • Shrinkage of the stellate reticulum by the loss of the intercellular fluid.
  • The shrinkage begins @ the height of the cusp or the incisal edge and progresses cervically.
59
Q

what is the stratum intermediam rich in?

A
  • alkaline phosphatase enzyme
  • acid mucopolysaccharides
  • glycogen
    (High metabolic activity)
60
Q

what happens to the shape of IEE in each stage:

*cap
*early bell (after induction)
*late bell (During D, E formation)

A

ans in order:
columnar
Tall Columnar
Tall Columnar

61
Q

what happens to the shape of OEE in each stage:

*cap
*early bell (after induction)
*late bell (During D, E formation)

A

ans in order:
cuboidal
low cuboidal
flat

62
Q

what happens to the shape of stellate reticulum in each stage:

*cap
*early bell (after induction)
*late bell (During D, E formation)

A

ans in order:
star shape
smaller w/ longer processes
shrinkage of the space

63
Q

initiation is present in which stages?

A

dental lamina and bud stage

64
Q

proliferation is present in which stages?

A

nearly all stages

65
Q

History- differentiation is present in which stages?

A
  • cap
  • bell stages (early and late)
66
Q

morph-differentiation is present in which stages??

A

bell stages (early and late).

67
Q

apposition is present in which stages?

A

late bell only

68
Q

what r the func of OEE?

A

a -Active transport of materials, specially after hard dental tissues formation.
b- Protective barrier.

69
Q

what r the brief funcs of IEE?

A
  • Organizing
  • Morphology
  • Nutritive
  • Root formation.
  • Enamel matrix
  • Reduced Enamel epithelium
  • primary enamel cuticle
70
Q

stellate reticulum funcs??

A

a- Act as a buffer against physical forces.
b- It acts as a store house for the nutritive materials.
c- It keeps room for the developing enamel.

71
Q

list the Strutum Intermedium funcs:

A

a- It controls fluid diffusion into and out of the ameloblasts.
b- It contains alkaline phosphatase enzyme needed enamel mineralization.
c- together with I.E.E form a single functional unit responsible for enamel formation.

72
Q

cervical loop funcns??

A

a –Its cells continue to divide until the crown attain its full size.

b- It gives rise to the epithelial component during root formation.

Oral Bio (1 decks)

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