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Tooth Development Flashcards

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
talk about the enamel knot
* 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.
26
who is zat Enamel cord?
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
27
what r the Transient Structures in the Cap Stage?
Enamel Knot and Enamel Cord
28
what is the Dental papilla??
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.
29
The ______ part of the dental papilla appears _____ cells but contains their cytoplasmic processes and fine argyrophilic fibers. This layer is cldd _____ or acellular zone.
peripheral free from cell free zone
30
Dental sac?!
is the condensation of the ecto- mesenchymal cells and fibers surrounding the enamel organ and dental papilla.
31
what is the role of the transient structures?
- determining the cusp position in molars or - may give the stratum intermedium in the bell stage.
32
@ what age does the cap stage occur??
occurs for the primary dentition between 9th and 10th w.i.u.
33
The vestibular lamina???
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
what arises from Lateral Dental Lamina??
Deciduous Teeth
35
what arises from Successional Dental Lamina?
Permanent Successors
36
how does the Permanent Molars arise in the dental arch?
From Distal Extension After The 5th Tooth from the Main Dental Lamina
37
in Early bell stage: hard dental tissues is ____ and in Late bell stage: hard dental tissue is ____
absent present
38
TRUE OR FALSE: Once the first layer of dentin is laid down it becomes advanced or late bell stage.
TRUE
39
in early bell stage: the decid. dental organ is connected to main dental lamina (which is connected to the oral epithelium) by a _______ cld ________
long and narrow epith. connection lateral dental lamina.
40
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).
lingually successional dental lamina permanent successors
41
in early bell stage: The cells of OEE become ______
low cuboidal
42
in early bell stage: IEE show elongation of____ (no.)
40 microns
43
what happens in the early bell stage, regarding the IEE?
IEE elongation is towards the dental papilla resulting in disappearance of cell-free zone.
44
explain the process of induction:
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
rant about the IEE showing alteration in their functional polarity
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
what happens to the stellate reticulum in the early bell stage?
At this stage the stellate cells expand further apart mainly by the increase of the intercellular fluid.
47
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
another name for cervical loop
zone of reflection
49
what happens to the dental papilla in the early bell stage?
Differentiation of odontoblasts at the periphery of the dental papilla
50
TRUE OR FALSE: Deposition of the first layer of dentine changes the early bell stage into late bell stage.
TRUE
51
What happens to the dental lamina in the late bell stage?
- 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
what are. the names given to the remnants of the dental lamina in the late bell stage?
Serres' pearls OR Epithelial Rests Of Serres
53
what happens to the OEE in the late bell stage?
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
The cells of the O.E.E. show criteria of active transporting cells by:
- Microvilli to increase SA - Cytoplasmic vesicles for transport. - increased mitochondria for energy.
55
what is the name of the process. that changes the IEE to ameloblast?
reciprocal induction
56
describe the process of Reciprocal induction:
- 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
how r ameloblats attached to each other?
They r attached to each other by junctional, complexes laterally + by desmosomes to stratum intermediaum.
58
what happens to the Stellate reticulum in the late bell stage:
* 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
what is the stratum intermediam rich in?
- alkaline phosphatase enzyme - acid mucopolysaccharides - glycogen (High metabolic activity)
60
what happens to the shape of IEE in each stage: *cap *early bell (after induction) *late bell (During D, E formation)
ans in order: columnar Tall Columnar Tall Columnar
61
what happens to the shape of OEE in each stage: *cap *early bell (after induction) *late bell (During D, E formation)
ans in order: cuboidal low cuboidal flat
62
what happens to the shape of stellate reticulum in each stage: *cap *early bell (after induction) *late bell (During D, E formation)
ans in order: star shape smaller w/ longer processes shrinkage of the space
63
initiation is present in which stages?
dental lamina and bud stage
64
proliferation is present in which stages?
nearly all stages
65
History- differentiation is present in which stages?
- cap - bell stages (early and late)
66
morph-differentiation is present in which stages??
bell stages (early and late).
67
apposition is present in which stages?
late bell only
68
what r the func of OEE?
a -Active transport of materials, specially after hard dental tissues formation. b- Protective barrier.
69
what r the brief funcs of IEE?
- Organizing - Morphology - Nutritive - Root formation. - Enamel matrix - Reduced Enamel epithelium - primary enamel cuticle
70
stellate reticulum funcs??
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
list the Strutum Intermedium funcs:
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
cervical loop funcns??
a –Its cells continue to divide until the crown attain its full size. b- It gives rise to the epithelial component during root formation.

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