Basic Science Seminar

1. GOODMORNING
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2. PRESENTED BY: DR.VINI MEHTA
MDS 1ST YR
Development of tooth &
Developmental Defects
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3. Contents
 Introduction
 Primitive oral Cavity
 Genes expressed
 Stages of tooth formation
 Vascular and Nerve Supply
 Root formation
 Developmental Disorders of Teeth
 Prevalence of developmental defects
 Conclusion
 References
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4. Introduction
 Tooth Development is a complex process by which
teeth form from embryonic cells, grow and erupt
into the mouth.
 Primary teeth start to form between 6th & 8th
week in utero. Permanent teeth begin to form in 20th
week in utero.
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5. PRIMITIVE ORAL
CAVITY/STOMODEUM
Oral epithelium
Mesenchymal
cells 5

6. Vestibular lamina & Dental
lamina
Dental lamina
Lip Furrow band
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7. Dental Lamina
 Phase 1: Initiation of entire deciduous dentition (8th wk).
 Phase 2:Initiation of successors of deciduous dentition.
(5thmonth to 10th month IUL)
 Phase 3:Initiation of permanent molars
 1st Permanent Molar: 4th month. IUL
 2nd Permanent Molar: 1st year post natally
 3rd Permanent Molar: 4th to 5th year
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8. Genes and Growth factors in
Odontogenesis
• A number of genes and growth factors leads to
differentiation of a simple cell to different forms of teeth
which are located in their particular position.
• In this the activation of MSX HOMEOBOX genes are
considered to be an important event in the biological
mechanism responsible for switching on the cascades of
events for tooth development.

9. Stages of tooth Development
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10. MORPHOLOGICAL
1. Dental lamina
2. Bud stage
3. Cap stage
4. Early bell stage
5. Advanced bell stage
6. Formation of enamel and dentin matrix
PHYSIOLOGICAL
Initiation
Proliferation
Histodifferentiation
Morphodifferentiation
Apposition
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11. BUD STAGE
 Time span - 8th week of IUL
 Main process- proliferation
 Enamel organ appears as a
simple, spherical to ovoid
epithelial condensation.
 Cells undergo mitosis & condense.
 Separated by basement
membrane
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12. CAP STAGE
 Time span:
 Early cap stage(11th week)
 Late cap stage(12th week)
 Main process:
Proliferation, Differentiation
 Early cap stage shows:
 IEE - Low columnar
 OEE - Cuboidal
 Central rounded cells
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13.  Late cap stage shows:
 IEE more columnar
 OEE remain cuboidal
 Stellate reticulum - Polygonal cells b/w Outer & Inner EE
form a cellular network.
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14. Successional Dental
Lamina
Outer Enamel
epithelium
Stellate Reticulum
Dental Papilla
Dental Sac
Inner Enamel
epithelium
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15. BELL STAGE
 Bell stage is divided into 2 stages.
 Early bell stage
 Late bell stage
 EARLY BELL STAGE (14th week):
 Dental lamina breaks down and
enamel organ Looses connection
with oral epithelium.
 Shows 4 distinct layers:
 OEE
 Stellate reticulum
 Stratum intermedium
 IEE
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16. Outer enamel epithelium
 Role of OEE :
 OEE folds and forms the
shape of enamel organ.
Between folds the
adjacent mesenchyme
of dental sac forms
papillae that contains
the blood capillary
loops which provides
the nutritional supply
to avascular enamel
organ
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17. Stellate reticulum
mechanical
Role of stellate reticulum
nutritive
Protects tissue
Maintains tooth
shape
Early bell stage
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18. STRATUM INTERMEDIUM
 Two to three layers of flattened
squamous cells.
 Exceptionally high activity of
alkaline phosphatase.
 Along with IEE, essential for
Enamel formation.
 Absent in root.
 Functions:
 Synthesis of proteins.
 Transport of materials to & from
the IEE
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19. INNER ENAMEL EPITHELIUM:
 Single layer of tall columnar cells.
 Begins where OEE bends.
 High glycogen & RNA content.
 Organizing: Influence the underlying
mesenchymal cells to differentiate into
Odontoblasts.
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20. LATE BELL STAGE (18th week of IUL)
 IEE become taller---
Pre- ameloblasts.
 Peripheral cells of dental papilla---
Odontoblasts.
 Secrete ground substance &
collagen fibers– Dentin matrix.
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21. FORMATION OF ENAMEL & DENTIN
MATIX ( APPOSITION)
• Apposition is the deposition of the matrix of the hard enamel
structures
• Appositional growth of the enamel & dentin is a layer like
deposition of an extracellular matrix.This type of growth is
therefore additive
• Appositional growth is characterised by regular & rhythmic
deposition of the extracellular matrix, which is of itself incapable
of further growth

22. Mineralization:
 Of the first-formed predentin is thought to occur in one
of two ways:

 1. Small mineral crystals appear, and mineralization
spreads from these sites throughout the first-formed
predentin.
 2. Small mineral crystals are nucleated in spaces which
exist in collagen fibrils ,Crystals are oriented along the
long axis of these fibrils.These minute crystals grow and
spread throughout the predentin, until the newly formed
band of collagen along the pulp is uncalcified.
 As each daily increment of predentin forms along the
pulpal boundary, the more peripheral adjacent predentin,
which formed, mineralizes and becomes dentin.

23. Dentinogenesis
 Oval or polygonal cells located near the basal lamina
That Separates the enamel organ from the dental papilla
are the Preodontoblast.These cells elongate and
become young Odontoblast.
 In the process of differentiation, odontoblasts become
columnar polarized cells having a secretary or apical pole
and a nonsecretory or basal pole.
 An extensively developed endoplasmic reticulum and
Golgi apparatus are characteristic of the active secretory
odontoblast.
 The odontoblast process, also known asTomes’ fiber,
becomes embedded in the extra cellular matrix of the
predentin & elongates as the odontoblast retreats from
the ameloblast layer of the enamel organ.
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25. Amelogenesis
 As the preameloblast differentiate to become a
secretory ameloblast it also polarizes. Intracellular
changes involve a lengthening of the cell,
proliferation of ER, and redistribution of cellular
organelles
 As enamel matrix is deposited, the ameloblast
migrates in an outward direction and acquires a set
of apical and basal terminal bars, as well as a
specialized apical process,Tomes‘ process
Tomes' process can be defined as that part of the
ameloblast, apical to the apical terminal bars.
 Tomes process contains numerous secretion
granules.Tomes' process can be divided into two
portions, a proximal and distal part.
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27. Vascular supply during early
development
 Clusters of blood vessels are found around the tooth
germ in the dental follicle and entering the dental papilla
during the cap stage.
 Their number increases in bell stage when matrix
deposition begins.
Nerve supply during early development
 Pioneer nerve fibers approach the developing tooth
during the bud-to-cap stage of development.
 The nerve fibers form a rich plexus around the tooth
germ in the follicle.
 The fibers penetrate the papilla .
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28. Root Formation
Cervical loop
Hertwig’s epith.
root sheath
Odontoblast
differentiation
Dentin formation
Disintegration
of root sheath
Cementoblast
differentiation
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29. Root formation
•Begins when the enamel &
dentin formation reaches the
future cemento-enamel junction
•The epithelial cells of inner & outer
enamel epithelium proliferate from
the cervical loop to form a double
epith. membrane known as
Epithelial root sheath of Hertwig
•It bends forming obtuse angle to
the enamel organ at the future
cemento-enamel junction to form the
epithelial diaphragm.
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30. Cervical loop Hertwig’s epith.
root sheath
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31. Odontoblast
differentiation 31

32. Dentin formation
Disintegration
of root sheath
Cementoblast
differentiation 32

33. Formation of multi- rooted
teeth
* The root trunk of molars is formed like single rooted tooth.
* At the bifurcation area, the epithelial diaphragm produces 2 or
3 tongue- like processes in case of 2 rooted & 3 rooted teeth.
* The processes grow towards each other & fuse dividing the
wide root trunk into 2 or 3 roots.
* Each one of these roots proceeds in development as in single
rooted tooth. 33

34. Clinical consideration
Accessory root canals Enamel Pearls
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35. Developmental Disorders of Teeth :
1. Size of teeth : Microdontia & Macrodontia.
2. Shape of teeth : Gemination, Fusion, Concrescence,
Dilaceration,Talon’s cusp, Dense in dent, Dens
evaginatus & taurodontism.
3. Number of teeth : Anodontia, Supernumery teeth
4. Structure of teeth : Amelogenesis Imperfecta,
Enamel hypoplasia, Dentinogenisis Imperfecta
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36. Developmental Disturbance in size ofTeeth
 1.Microdontia
 a.True generalized microdontia
 b.Relative generalized microdontia
 c.Microdontia involving single tooth.
 2.Macrodontia
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37. HUTCHINSON’S INCISOR
MULBERRY MOLARS

38. Fusion Gemination
Dens invaginatus
Talon’s cusp 38

39. DILACERATION
• Dilaceration refers to an angulation
or a sharp bend or curve anywhere
along the root portion of a tooth
• Condition probably occurs
subsequent to trauma or any other
defect of development which alters
the angulation of the tooth germ
during root formation
• Can easily be detected by
radiographs
• Care should be taken during
extraction since these teeth are
more prone to fracture

40. CONCRESCENCE
Concrescence is a
condition of teeth where
the cementum overlying
the roots of at least two
teeth join together.The
cause can sometimes be
attributed to trauma or
crowding of teeth.
Radiographic diagnosis is
mandatory before
attempting tooth
extraction

41. CompleteAnodontia PartialAnodontia
SUPERNUMERARY
TEETH
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42. Enamel Hypoplasia AMELOGENESIS IMPERFECTA
DENS EVAGINATUS
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43. Dentinogenisis Imperfecta
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44. Prevalence of developmental
defects
 The common group was number anomalies.The
most common number anomaly was hypodontia
(4.19%), hyperdontia (2.40%). Analyzing the next
prevalent group of shape anomalies,
microdontia (2.58%) was found to be the most
common, followed by taurodontism (2.49%),
dens evaginatus (2.40%) and talon cusp (0.97%).
Dentinogenesis imperfecta (0.09%) was the
rarest, followed by amelogenesis imperfecta
(0.27%) and fusion (0.27%).
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45. Conclusion
 Being a public health dentist it’s our duty, not
only to understand accurately the mechanism
of tooth development but also to understand
the developmental defects for correct
diagnosis and to develop certain curative and
preventive measures to diminish the disease
burden on the community
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46. REFERENCES:
 ORAL HISTOLOGY, DEVELOPMENT, STRUCTURE
AND FUNCTION : 5TH edTENCATE.
 ORARBAN’S ORAL HISTOLOGY AND EMBROLOGY
: 11TH edition BHASKAR.S.N.
 Oral Pathology : by Shafer Hine Levi.
 COLOUR ATLAS OF ORAL HISTOLOGY AND
EMBRYOLOGY
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