initiation of tooth development stages of development clinical significance timings of development

1. DEVELOPMENT OF TEETH

2. INTRODUCTION:
• 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.

3. • 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)

4. INITIATION OF TOOTH DEVELOPMENT
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.

5. 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 proceed posteriorly

6. • Connective tissue cells underlying the oral
ectoderm induce overlying ectoderm to start
tooth development.
• Ectomesenchyme proliferation form primary
epithelial band in the 6th week of intrauterine life
which corresponds in position to future dental
arches.
• In the 7th week it divides into :
• A lingual process called dental lamina
• A buccal process called vestibular lamina

7. DENTAL LAMINA:
• Total activity of dental lamina extends over a period
of minimum of 5 years.
• As dentine and enamel start to develop dental
lamina begins to degenerate separating into clumps
but whose thickness of lamina is not perforated.
• Breaking upon of dental lamina determines crown
pattern.
• Degeneration of dental lamina separates developing
tooth from oral epithelium as a result of
degeneration tooth continues its development
within tissues of jaw.
• Penetration of lingual epithelium by tooth is unique
example of natural break in the epithelium of the
body.

8. VESTIBULAR LAMINA
• Also called as furrow band or vestibular band.
• It is horse shoe shaped in growth of epithelium,
which develops buccal to dental lamina.
• Vestibular band grows deeply into mesenchyme
of premature jaws separating lips and cheeks
from tooth forming region.
• It subsequently thickens and clears at vestibular
growth from oral vestibular lamina.

13. BUD STAGE
• Differentiation of dental lamina leads to formation
of round, ovoid swelling at 10 different points
corresponding to future position of deciduous
teeth.
• These are the primordial of enamel organ.
• Enamel organ consists of peripherally location low
columnar cells and centrally located polygonal
cells.

14. • Dental papilla is the area of ectomesenchyme
condensation subjacent to enamel organ.
• Dental sac is the area of ectomesenchyme
condensation surrounding the tooth bud and
dental papilla.
• Cells of dental sac will form cementum and
periodontal ligament.

16. CAP STAGE:
• Characterized by a shallow invagination of deep
surface of a bud.
• Outer and inner enamel epithelium.
• Stellate reticulum: polygonal cells begin to
separate as more intercellular fluid is produced
and forms cellular network called stellate
reticulum.
• Enamel knot: cells in center of the enamel
organ are densely packed. The knot projects
towards the underlying dental papilla. Vertical
extension of enamel knot forms enamel cord.

17. • Both the structures disappear before enamel
formation begins
• DENTAL PAPILLA AND DENTAL SAC:
dental papilla is for mature organ of dentine and
shows active budding of capillaries and mitotic
figures.
• Dental sac are important for the formation of
cementum and periodontal ligaments.

19. BELL STAGE:
• Stage of Histodifferentiation and Morpho
differentiation.
• During histodifferentiation some cells of dental
organ differentiates into specific form and
shape. This is seen in early bell stage.
• During morpho differentiation dental organ
assumes characteristic shape of tooth. This is
seen in late bell stage.
• The invagination of epithelium deepens and its
margins continue to grow and enamel organ
assumes a bell shape.

21. • 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:

22. • 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.
ADVANCED BELL STAGE:

23. APPOSITION:
• The tooth germ forms calcified tissues of the
tooth.
• There is a layer like deposition of an
extracellular matrix resulting in additive growth.
• There is regular and rhythmic deposition, which
is capable of further growth.

26. WHAT CAN GO WRONG?
• Ectodermal dysplasia: Tooth bud may be
absent.
• Anodontia: Complete absence of teeth.
• Accessory teeth: There may be extra or
supernumerary teeth buds.
• Neonatal teeth: Teeth are seen to erupt
immediately after birth.
• Gemination: Two teeth may be fused to each
other.

27. • Malocclusion: the alignment of upper and
lower teeth maybe incorrect.
• Hypocalcified/Hypomineralized dentin:
if organic matrix is normal but its
mineralization is defective.
• Enamel hypoplasia: disturbance in the
synthesis and secretion of the organic matrix of
enamel.
• Hutchinson’s incisor: The maxillary central
incisors may become notched at the edges in
the individuals born with congenital syphilis.

28. TIME SCALE OF HUMAN TOOTH
DEVELOPMENT:
AGE DEVELOPMENT CHARACTERSTICS
42-48 days Dental lamina formation.
55-56 days Bud stage, deciduous incisor canine and molar.
14 weeks Bell stage for deciduous teeth, bud stage for
permanent teeth.
18 weeks Dentine and functional ameloblasts in
deciduous teeth.
32 weeks Dentine and functional ameloblasts in
permanent teeth.

29. REFRENCES
• Ten Cate’s Oral Histology Development,
Structure, and Function Antonio Nanci : 7th
edition.
• Orban’s Oral Histology and Embryology : 12th
edition.

30. THANK YOU