ANATOMY AND PHYSIOLOGY OF REPRODUCTIVE SYSTEM.pptx
Tooth development
1.
2.
3.
4. Introduction
Initiation of Tooth Development
Tooth development
Developmental Stages
Root development
Histophysiology
Crown Pattern Determination
Nerve & Vascular supply during early development
5. Formation of Permanent Dentition
Hard Tissue Formation
Formation of Supporting Tissues
Tooth Eruption
References
6. Tooth development (ODONTOGENESIS) is the
complex process by which teeth form from the
embryonic cells, grow, and erupt into the oral cavity.
For human teeth to have healthy oral environment,
enamel, dentin, cementum & the periodontium all
must develop during appropriate stages of fetal
development.
7. Entire primary dentition is initiated between 6th and
7th weeks of embryonic development.
Successional permanent teeth initiated between 20th
week in utero and 10th month after birth.
Permanent molars between 20th week in utero (first
molar) and 5th year of life (third molar).
8. The primitive oral cavity is called stomodeum – lined by
stratified squamous epithelium - oral ectoderm.
The oral ectoderm contact the endoderm of the
foregut to form the buccopharyngeal membrane.
At about 27th day of gestation buccopharyngeal
membrane ruptures and the primitive oral cavity
establishes a connection with the foregut.
9. Most of connective tissue cells
underlying the oral ectoderm are of
neural crest.
These cells induce the overlying
ectoderm to start tooth
development.
Which begins in anterior portion of
what will be the future maxilla and
mandible and prooced posteriorly
10. About 37 days of
development –
continuous band of
thickened epithelium
forms around the mouth
presumptive upper and
lower jaws.
Bands are roughly horse
shoe shaped and
correspond in position
of the future dental
arches.
11. Thickening of epithelial band occurs due to change
in orientation of mitotic spindle & cleavage plane of
dividing cells.
Each band of epithelium is called PRIMARY
EPITHELIAL BAND.
Quickly give rise to 2 subdivisions
- vestibular lamina
- dental lamina
12.
13. Lingual (inner) process of primary epithelial band.
Primordium for the ectodermal portion of deciduous
teeth.
Permanent molars arise from distal extension.
Successional lamina: lamina from which permanent
teeth develop.
Fate: Remnants of dental lamina persists as epithelial
pearls or islands within the jaw as well as gingiva--
Cell Rest of Serres.
15. Buccal (outer) process of primary epithelial band.
Lip Furrow Band
Cells rapidly enlarge.
Becomes the vestibule between the lips and cheek &
the tooth-bearing area.
16. Primary epithelial
band
Vestibular lamina (labially)
Dental lamina (lingually)
Milk teeth
Its Lingual extension
(successional)
All permanents except
molars
Distal extensiongives rise to
permanent molars
17. 10 small swellings
develop in the region of
future primary teeth.
They form enamel organ
and give rise to the
enamel of the teeth.
TOOTH DEVELOPMENT
18. Peripheral condensation
of ectomesenchymal
cells around enamel
organ forms dental
papilla
Surrounding dental
papilla and enamel organ
is dental follicle or sac
19.
20. Tooth germ is formed by
Enamel organ enamel
+
Dental papilla pulp and dentin
+
Dental sac cementum and PDL
22. The epithelium of the dental lamina is
separated from the underlying
ectomesnchyme by a basement membrane.
The cells of the epithelium proliferate faster
than the adjacent cells.
The enamel organ consist in this stage
peripherally located low columnar cells &
centrally located polygonal cells
23.
24. The next step is mitosis of cells of tooth bud and
surrounding mesenchyme.
As a result of increased mitotic activity and
migration of neural crest cells in to the area of the
ectomesenchymal cells surrounding the tooth bud
condense.
The area of ectomesanchymal condensation
immediately adjacent to enamel organ is called dental
papilla.
The condensed ectomesenchyme that surround the
tooth bud and dental papilla is the dental sac.
Both dental papilla and dental sac become more well
defined as enamel organ grows into the cap and bell
shapes.
25.
26. Shallow invagination on
the deep surface of the
bud.
Peripheral cells are
cuboidal, cover the
convexity of the cap–
Outer Enamel
Epithelium.
Cells in the concavity of
the cap become tall,
columnar– Inner Enamel
Epithelium
27.
28. Polygonal cells located between the outer and inner
enamel epithelia. They begin to separate as more
intercellular fluid is produced and form a cellular
network called the stellate reticulum.
The cells assume a branched reticular form.
The spaces in this reticular network are filled with a
mucoid fluid that is rich in albumin, which gives the
stellate reticulum a cushionlike consisstency that may
support and protect the dellicate enamel-forming
cells.
29. Organizing influence of proliferative epithelium of
enamel organ
Papillary cells proliferate
Budding of capillaries and mitotic figures
Later differentiate – odontoblasts – dentin
30. marginal condensation in the ectomesenchyme
surrounding the enamel organ and dental papilla.
in this zone a denser and more fibrous layer
Develops
primitive dental sac
formation of cementum and the periodontal ligament
31. Temporary structures, disappear before enamel
formation begins.
1. Enamel Niche: Enamel organ has double attachment
of dental lamina to the overlying oral epithelium
enclosing ectomesenchyme.
32. The center of
enamel organ
contains densely
packed cells & are
called enamel knot.
They extend slightly
into the dental
papilla & form knob
like projection
33. A vertical projection
is seen from this
knot known as
enamel cord.
Both knot & cord are
temporary
structures.
Function : both acts
as a reservoir of
dividing cells.
34. Enamel Septum: Enamel cord extends to meet outer
enamel epithelium.
Enamel Navel: (resembles umbilicus) Outer enamel
epithelium at a point of meeting shows small
depression
35. Enamel organ
resembles a bell.
Undersurface of the
epithelial cap deepens.
Continuation of
histodifferentiation
(ameloblasts and
odontoblasts are
defined) & beginning
of
morphodifferentiation
(tooth crown assumes
its final shape).
36. Consists of four distinct
layer:
a. Inner Enamel Epithelium
b. Stratum Intermedium
c. Stellate Reticulum
d. Outer Enamel
Epithelium
37.
38. Consists of a single layer of cells
differentiate prior to amelogenesis into
tall columnar cells
Ameloblasts
39. The cells of the inner enamel epithelium
exert an organizing influence on
mesenchymal cells in the dental papilla
later differentiate into odontoblasts.
40. Formed by a few layers of squamous cells between
the inner enamel epithelium and the stellate
reticulum.
The well-developed cytoplasmic organelles acid
mucopolysaccharides, and glycogen deposits indicate
a high degree of metabolic activity.
This layer seems to be essential to enamel formation.
It is absent in the part of the tooth germ that
outlines the root portions of the tooth that does not
form enamel.
41. The stellate reticulum expands further mainly by an
increase in the amount of intercellular fluid.
The cells are star shaped, with long processes that
anastomose with those of adjacent cells.
Before enamel formation begins, the stellate
reticulum collapses, reducing the distance between
the centrally situated ameloblasts and the nutrient
capillaries near the outer enamel epithelium.
This change begins at the height of the cusp or the
incisal edge and progresses cervically.
42. These cell flatten to a low cuboidal form.
At the end of the bell stage, the formerly
smooth surface of the outer enamel
epithelium is laid in folds. Between the folds
the adjacent mesenchyme of the dental sac
forms papillae that contain capillary loops and
thus provide a rich nutritional supply for the
intense metabolic activity of the avascular
enamel organ.
43. Extends lingually.
Successional Dental
Lamina as gives rise to
enamel organs of
permanent successors
of deciduous teeth
(permanent incisor,
canines & premolars).
44. The dental papilla is enclosed in the
invaginated portion of the enamel organ.
Before the inner enamel epithelium begins to
produce enamel, the peripheral cells of the
mesenchymal dental papilla differentiate into
odontoblasts under the organizing influence
of the epithelium. First, they assume a
cuboidal form; later they assume a columnar
form and acquire the specific potential to
produce dentin
45. The basement membrane
separates the
enamel organ and the dental papilla
just prior to dentin formation
membrana preformativa
46. Before formation of dental tissues begins the
dental sac shows a circular arrangement of its
fibers and resembles a capsular structure.
With the development of the root, the fibers
of the dental sac differentiate into the
periodontal fibers that become embedded in
the developing cementum and alveolar bone.
47. This point is where the cells
continue to divide until the tooth
crown attains its full size.
The inner epithelium begins at the
point where the outer epithelium
bends to form the concavity into
which the cells of the dental
papilla accumulate. The region
where the internal and external
dental epithelia meet at the rim of
the enamel organ is known as the
zone of reflexion or cervical loop.
Cervical loop
48. Commencement of mineralization & root formation.
Boundary between inner enamel epithelium & odontoblasts–-
outlines future DEJ.
1st formation of dentin.
Proceeds pulpally & apically.
After first layer of dentin is formed, ameloblast which has
already differentiated from IEE cells lay down enamel over
dentin in future incisal & cuspal areas.
Proceeds coronally & cervically.
Cervical portion of the enamel organ gives rise to Hertwig’s
epithelial root sheath.
Outlines the future root.
Responsible for the shape, length, size & number of roots.
49. After odontoblasts
form due to
organizing influence
of epithelial cells,
they instruct
ameloblasts in turn
to secrete enamel
matrix
(reciprocal
induction)
50.
51. Root formation commences once the enamel and
dentin formation have reached the future
cementoenamel junction(CEJ).
Cervical loop from the enamel organ forms the
Hertwigs epithelial root sheath (HERS).
HERS determines shape of the roots and inititates
radicular dentin formation.
HERS consists of the outer and inner enamel
epithelium only.
52. • At the future CEJ, HERS turn inwardly to a
horizontal plane forming the epithelial diaphragm.
• Plane of diaphragm remains relatively fixed during
development and growth of the root.
• Proliferating cells of epithelial diaphragm induce
proliferation and differentiation of cells of dental
papilla to odontoblasts and form root dentin.
53. • The cells of dental follicle proliferate and invade the
root sheath dividing it in to network of strands.
• Degradation of the HERS allows contact of the
dental follicle cells with the dentin surface and they
differentiate into cementoblasts.
• The cementoblasts cover the root dentin and undergo
cementogenesis – laying down cementoid
54.
55.
56. The first layer of dentin has been laid down
the epithelial root sheath loses its structural
continuity & its close relation to the surface of the
root.
Its remnants persists as an epithelial network of
strands or tubules near the external surface of the
root.
These epithelial remnants are found in the periodontal
ligament of erupted teeth
called rests of malassez.
57. Root sheath forms epithelial diaphragm
Outer and inner epithelia bend at future
CEJ into a horizontal plane
Narrowing of wide cervical opening of
tooth germ
Cells of epithelial diaphragm and
connective tissue of pulp proliferate
adjacent to diaphragm
Free end of epithelium proliferates coronal
to diaphragm
58. Differentiation of odontoblasts and formation
of dentin after root lengthening
Connective tissue of dental sac proliferates and
invades continuous double epithelial layer
forming epithelial strands
Connective tissue cells come in contact with
outer surface of dentin causing differentiation
of cementoblasts and deposition of cementum
Proliferation of epithelium in diaphragm lags
behind connective tissue
Width of apical foramen is reduced by further
apposition of dentin and cementum to apex of
root
59. Division of root trunk in 2/3 roots is due to
differential growth of epithelial diaphragm
Expansion of cervical opening occurs in long
tongue like extensions of horizontal
diaphragm
Before division of root trunk, free ends of
these epithelial flaps grow towards each
other and fuse
Single cervical opening of coronal enamel is
divided into 2-3 openings
On pulpal aspect – dentin formation starts
and on periphery – root development starts
60. • Anterior teeth, premolars and molars all begin as a
single root – root trunk.
• Root of the posterior teeth divides from the trunk
into the correct number of root branches.
• Differential growth of the Hertwig’s epithelial root
sheath results in the division of the root trunk into
two or three roots.
61.
62.
63.
64. INITIATION
• The dental lamina and associated tooth buds represent
those parts of the oral epithelium that have potential for
tooth formation.
• Initiation induction requires ectomesenchymal-epithelial
interaction.
• Lack of initiation results in absence of either a single
tooth or multiple teeth, or there may be a complete lack
of teeth.
• Abnormal initiation may result in the devalopment of
single or multiple supernumerary teeth.
65. • Enhanced proliferative activity ensues at the points
of initiation and results successively in the bud, cap
and bell stages of the odontogenic organ.
• Causes regular changes in the size and proportions of
the growing tooth germ.
66. • Histodifferentiation is the process in which a mass of similar
epithelial cells transforms itself into morphologically and
functionally distinct components.
• Histodifferentiation begins in the late cap stage and reaches
its highest development in the early bell stage.
• The organizing influence of the inner enamel epithelium on the
mesenchyme is evident in the bell stage and causes the
differentiation of the adjacent cells of the dental papilla into
odontoblasts.
• With the formation of dentin, the cells of inner enamel
epithelium differentiate into ameloblasts and enamel matrix is
formed.
67. • The morphologic pattern is established by
differential growth.
• The cells arrange themselves along the site which
out lines the basic form and relative size of the
future tooth.
• The advance bell stage is the important stage for it
outlining the future dentinoenamel junction
68. • The dentinoenamel and dentinocemental junctions
which are different and characteristic for each
tooth, acts as blue print pattern.
• Inconformity with this pattern, ameloblasts,
odontoblasts and cementoblasts deposit the enamel,
dentin and cementum, giving the completed tooth its
characteristic form and size.
• Disturbances may cause supernumerary cusps or
roots, loss of cusps or roots, peg tooth.
69. • Apposition is the deposition of the matrix for the
hard dental structures.
• There is regular and rhythmic layer like deposition
of the extracellular matrix resulting in additive
growth.
• This matrix is partially calcified- serves as a frame
work for later calcification proper.
• Disturbances can cause hypocalcified or
hypomineralized enamel or dentin.
70.
71. Future crown patterning -- bell stage, by folding of
the inner enamel epithelium.
Cessation of mitotic activity within the inner enamel
epithelium determines the shape of a tooth.
The point at which inner enamel epithelium cell
differentiation first occurs represent the site of
future cusp development.
72.
73. Vascular supply:
Cap stage.
Blood vessels grow in the dental follicle and enter
the dental papilla.
The number of blood vessels reaches a maximum at
the beginning of the crown stage, and the dental
papilla eventually forms in the pulp of a tooth.
74. Pioneer nerve fibres approach developing
tooth during bud to cap stage development.
Nerve fibre ramify and form a rich plexus
around the tooth germ in that structure.
Nerve fibres penetrate dental papilla when
dentinogenesis begins.
Initial innervation – sensory for future p.d.l &
pulp.
75. Arises from dental lamina.
Form in essentially the same manner, though at
different times.
The tooth germs that give rise to permanent incisors,
canines and premolars form as a result of further
proliferative activity within the dental lamina, lingual
to the deciduous tooth germ.
The developing permanent molars have no deciduous
predecessor and their tooth germs originate from
the dental lamina that extends posteriorly beneath
the oral epithelium after the jaws have grown.
76.
77. The next step in development of tooth is terminal
differentiation of ameloblast and odontoblast and
formation of enamel and dentin.
Until crown assumes the final shape durind cap to
early bell stage,all cells of inner enamel epithelium
continually divide.
First layer of dentin appears at the cusp tips and
progresses cervically, & the columnar cells of the
inner enamel epithelium becomes elongated & show
reverse polarization, with the nuclei adjacent to
stratum intermediate (ameloblasts).
78. Undifferentiated ectomesenchymal cells increase
rapidly in size and ultimetly differentiated into
odontoblast .
In the absence of epithelial cells no dentin develops.
As devlpoment continues ,progressive dfferentiation
of cells of IEE down cusp slopes,
odontoblast are differentiate begin to elaborate the
organic matrix of dentin,which ultimately mineralize.
As the organic martrix deposited,odontoblast move
towards center of dental papilla,leaving behind the
cytoplasmic extension around which dentin is formed
79. Inner enamel epithelial cells continue their
differentiation into ameloblast that produce organic
matrix against the newly formed dentinal surface.
Organic matrix is mineralize and becomes initial
enamel layer of crown.
Ameloblast moving away from the dentin , leaving
behind an ever increasing thickness of enamel.
the differentiating odontoblasts and ameloblasts
receive signals from each other n viceversa –-
Reciprocal Induction.
cells of enamel organ receives its nourishment from
two sources-blood vessels of dental papilla.
-vessels situated at periphery of OEE.
80.
81. While roots are forming, the supporting tissues of
the tooth also develop.
The supporting tissues(cementum, PDL, bone) of the
tooth are formed from the dental follicle.
As the root sheath fragments, ectomesenchymal cells
of dental follicle penetrates between the epithelial
cells & lie close to the newly formed root dentin.
82. These cells differentiate into cementum-forming
cells- Cementoblasts.
Fibers of the periodontal ligament, which will also
form from the cells of the dental follicle will get
anchored in the organic matrix of the cementum
which later gets mineralized.
Bone in which ligament fiber bundles are embedded is
also formed by cells that differentiate from dental
follicle.
83. After formation of root is initiated, the tooth begins
to erupt.
Axial movement-- from its developmental position
within the jaw to its final functional position in the
occlusal plane.
Formation of reduced enamel epithelium.
REE + oral epithelium = solid mass of epithelial cells
over crown of the tooth.
Central cells in this mass disintegrate–- epithelial
canal–- crown of the tooth erupts
84.
85.
86.
87. TYPES OF OPEN
APICES
These can be of two
configurations.
NON BLUNDERBUSS
Broadly opened apex
(Cylinder – shaped root
canals).
BLUNDERBUSS
Funnel shaped apex
(Apical opening can be
wider than the coronal
root canal orifice
(inverted root canal
conicity)
Acc to BEENA PHILIP MATHEW *
MITHRA N. HEGDE **,Endodontology.
88. Diagnosis:
-visual examination
-clinical examination
-radiographic examination
-laser doppler flowmetry-potential aid to vitality
testing and pulp
revascularization.
Management:
-apexification
-apexogenesis
89. Ten Cate’s Oral Histology Development, Structure,
and Function Antonio Nanci : 7th edition.
Orban’s Oral Histology and Embryology : 12th edition.
Inderbeer Singh: Human Embryology
James k avery-oral development and histology,3rd
edition
