1. Tooth Development
(Odontogenesis)
By: Hasu.Chaudhari

2. Dentition
Primary dentition – develops during prenatal
period
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20 teeth
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Permanent dentition – develops as the jaw
grows and matures
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32 teeth
period in between – during the preteen years
(mixed dentition period)
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3. TOOTH DEVELOPMENT
Multiple stages:initiation stage – 6th to 7th week
bud stage – 8th week
cap stage – 9th to 10th weeks
bell stage – 11th to 12th weeks
apposition stage – varies per tooth
maturation stage – varies per tooth
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4. BUD STAGE
Tooth formation
 Proliferation of ectoderm lining the Alveolar Process & Epithelium
become thick on convex side of this process form Dental lamina
Dental lamina where tooth formation will occur - on
the 1st branchial arch.
Dental lamina, even apparent before the alveolar
process itself is defined.
Alveolar process – Semicircular in outline
Similarly, Dental lamina – Curved.
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5.  Dental lamina shows local thickening which results
to form 1 milk tooth.
 Deeper part of dental lamina enlarges to form
enamel organ.
 These thickening called enamel organs.
 10 in number – 5 on each side of alveolar process.

6. Stages in the formation of an enamel organ &
developing tooth
CAP STAGE
 As the enamel organ downwards into the mesenchyme its lower
end forms a cup shape appearance.
 Then cup occupied by mass of mesenchyme called a dental
papilla.
 This mesenchyme originate from neural crest cells.
 Enamel organ + Dental papilla = Tooth germ.
 At this stage developing tooth looks like a cap.

7. BELL STAGE
 The cells of the enamel organ that line the papilla become columnar these are
called ameloblasts.
 Mesodermal cells of the papilla that are adjacent to the ameloblast cells
arrange themselves as a continuous epithelium like layer. Cells of this layer are
called Odontoblasts.
 The ameloblasts & odontoblasts are separated by a basement membrane.
 The remaining cells of the papilla form the pulp of tooth.
 The developing tooth looks like a bell.

8. APPOSITIONAL STAGE
 Ameloblasts secrete enamel on the superficial surface of the basement
membrane.
 The odontoblasts secretes dentine on its deeper surface.
 The process of secretion of enamel & dentine is similar to that of formation of
bone by osteoblasts.
 Ameloblasts & odontoblasts move far away from each other by increasing layers
of enamel & dentine.

9. MATURATION STAGE
After the enamel is fully formed, the ameloblast
disappear leaving a thin membrane, the dental
cuticle, over the enamel.
The odontoblasts, continue to separate the
dentine from pulp throughout the life of the
tooth.
Alveolar part of the maxillae & the mandible are
formed by ossification.
As ossification progresses, roots of the teeth
become surrounded by bone.

10. The root of the tooth is established by continued
growth into underlying mesenchyme.
Odontoblasts in this region secrete dentine (no
ameloblasts cells).
As layers of dentine deposited, the pulp space
becomes narrower & converted into a canal through
which nerves & blood vessels pass into the tooth.
Dentine is covered by mesenchymal cells that
differentiate into cementoblasts.
These cells lay down a layer of dense bone called
Cementum.
Mesenchymal cells form a periodontal ligament which
connects the root with the socket in the jaw bone.

11. Formation of permanent tooth
 The dental lamina gives off a series of buds, one of which lies on the medial
side of each developing milk tooth.
 These buds form the enamel organs.
 They give rise to permanent incisors, canines & premolars.
The permanent molars are formed from buds that arise from the dental lamina
posterior to the region of last milk tooth.

12. Dental lamina is established in the 6th week of
intrauterine life.
The germ of 3rd molar is formed after birth & germ of
premolar & 2nd molar are not very developed & rest
of all show considerable development at birth.
The developing tooth germs undergo calcification
(accumulation of calcium salts in a body tissue).
All the temporary teeth & permanent lower 1st molar
begin to calcify before birth.
The permanent teeth begin to calcify at varying ages
after birth.

13. Anomalies of teeth
1. Anodentia :- one or more teeth may be absent or complete
absence.

14. Supernumerary teeth may be present

15. Gemination :- Two or more teeth may be fused to
each other.

16. Malocclusion :- Alignment of the upper & the lower
teeth may be incorrect.

17. The End :D