Primary dentition – develops during prenatal
Permanent dentition – develops as the jaw
grows and matures
period in between – during the preteen years
(mixed dentition period)
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
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.
Dental lamina shows local thickening which results
to form 1 milk tooth.
Deeper part of dental lamina enlarges to form
These thickening called enamel organs.
10 in number – 5 on each side of alveolar process.
Stages in the formation of an enamel organ &
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
This mesenchyme originate from neural crest cells.
Enamel organ + Dental papilla = Tooth germ.
At this stage developing tooth looks like a cap.
The cells of the enamel organ that line the papilla become columnar these are
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
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.
Ameloblasts secrete enamel on the superficial surface of the basement
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.
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
Alveolar part of the maxillae & the mandible are
formed by ossification.
As ossification progresses, roots of the teeth
become surrounded by bone.
The root of the tooth is established by continued
growth into underlying mesenchyme.
Odontoblasts in this region secrete dentine (no
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
Mesenchymal cells form a periodontal ligament which
connects the root with the socket in the jaw bone.
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.
Dental lamina is established in the 6th week of
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
Anomalies of teeth
1. Anodentia :- one or more teeth may be absent or complete