1. Development of teeth- Odontogenesis
Dr Jamal N. Naim
PhD in Orthodontics

2. Objectives
To provide a detailed description of tooth formation and development.
To explain different hypothesis about tooth initiation and type determination.
To understand the histological aspect of different stages of tooth development.
To discuss the formation and development of dental root and supporting tissues.
To give a brief comments on related clinical aspects.

3. Stages of tooth development
formation of primary epithelial band
down growth of dental lamina
development, differentiation & morphogenesis of tooth bud
Bud stage
Cap stage
Bell stage
Crown stage
dentinogenesis
amelogenesis
root formation
tooth eruption

4. ... ... ... Three processes overlap the development stages
Histogenesis
differentiation of cells
Initiation
site of future teeth established
Morphogenesis
shape of the tooth determined

5. Stages of tooth development
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

6.
tooth development occurs in the primitive oral cavity – stomatodeum
First signs of formation – day 11
stomatodeum
lined by thin epithelium derived from ectoderm
embryonic connective tissue – ectomesenchyme
development of teeth involves interactions between ectoderm and ecto-mesoderm.
mechanisms remain unknown

7. Primary epithelial Band

8. Initiation of tooth development
Involves epithelial-ectomesenchymal interactions
Thickening of the epithelium where tooth formation will occur on the 1st branchial arch

9. Primary epithelial band
appears at ~ 5-6 weeks of development
in future maxilla & mandible
horseshoe shaped band of thickened epithelium in the position of future dental arches
superficial epithelial thickening
From Nanci (2003) Ten cate oral histology
showing the location of the primary epithelial bands

10. Dental lamina derived from the primary epithelial band
epithelial band divides into two at 7 weeks and grows away from the epithelial surface
vestibular lamina (buccally  vestibule)
dental lamina (lingually  teeth)

11. Dental lamina

12. Tooth formation -initial stage-
The dental lamina develops a series of epithelial outgrowths - grow deep into the mesenchyme
develops in the future spot for the dental arches
will form the midline for these arches
arches then form posteriorly from this point
the ingrowths represent the future sites for each deciduous tooth

13. Tooth formation -initial stage-
the vestibular lamina cells rapidly enlarge and then degenerate – forms a cleft that becomes the vestibule of the oral cavity
The initiation of tooth formation starts around the 37th day of gestation.

14. Early Dental Lamina Tongue Dental lamina Vestibular lamina
©Copyright 2007, Thomas G. Hollinger, Gainesville, Fl

15. Late Dental Lamina

16. Late Dental lamina
from: Ten Cate: Oral Histology - Development, Structure and Function

17. Both deciduous & permanent dentitions arise from dental lamina
deciduous teeth arise from the initial development of the dental laminae
~ 13 weeks in utero
epithelium proliferates at 10 sites in each dental lamina to form the early tooth germs
(from: Berkovitz. Oral Anatomy, Histology and Embryology, Mosby- Wolfe, Inc.)

18.
Permanent incisors, canines & premolars form as a result of further proliferation of the dental laminae on the lingual aspect of the deciduous tooth germ.
The permanent tooth germ remains dormant for sometimes
(from: Berkovitz. Oral Anatomy, Histology and Embryology, Mosby- Wolfe, Inc.)

19. ... ... ... Permanent molar teeth have no deciduous predecessor
Permanent molars develop from growth of the dental lamina below the epithelium of the oral cavity posteriorly.
from: Ten Cate: Oral Histology - Development, Structure and Function

20. Tooth type determination
Patterning means the determination of specific tooth type at the correct position.
Homodont are animals with same shaped teeth
Heterodont are the most mammals with different tooth types
Two theories for the determination of tooth type

21. Tooth type determination
The field model theory proposes that factors responsible for the determination reside within the ectomesenchyme, but graded fields for each tooth
The clone model theory proposes that each tooth is derived from a clone of ectomesenchymal cells programmed by the epithelium to produce a given pattern.

22. Tooth germ formation bud stage cap stage early bell stage
late bell stage rapid change in size & shape
crown stage enamel formation
root formation cementum formation
dentine formation

23. Bud stage ~8 weeks in utero
individual epithelial bud (swellings) on the deep surface of the dental lamina are recognisable
little changes in shape or function of epithelial cells
ectomesenchyme cells are closely packed around epithelial bud

24. Bud stage A B
(A) Epithelial bud.
(B) Ecto- Mesenchymal Cells.

26. Tongue
Bud stage
Future dental papilla

27. Cap stage 11 weeks in utero
Proliferation of epithelial bud & invagination of the deeper surface of the epithelial bud forms the cap shape
More condensation of ectomesenchyme
Increase in morphogenesis
central cells of enamel organ spherical while peripheral cells become cuboidal

28. Cap stage 11 weeks in utero More condensation of ectomesenchyme
characterized by continuation of the ingrowth of the oral epithelium into the mesenchyme.
tooth bud of the dental lamina proliferates unequally in different parts of the bud
forms a cap shaped tissue attached to the remaining dental lamina
looks like a cap sitting on a ball of condensing mesenchyme

29. Cap stage occurs for the primary dentition during the fetal period
this stage marks the beginning of histodifferentiation; (differentiation of similar epithelial cells into functionally and morphogically distinct components)
the tooth germ also begins to take on form – start of morphodifferentiation

30. Cap stage
a depression forms in the deepest part of each tooth bud and forms the cap or enamel organ (or dental organ) – produces the future enamel (ectodermal origin)

31. Cap stage
below this cap is a condensing mass of mesenchyme – dental papilla – produces the future dentin and pulp tissue (mesenchymal origin)

32. Cap stage
the basement membrane separating the dental organ and the dental papilla becomes the future site for the dentinoenamel junction (DEJ)

33. Cap stage
remaining mesenchyme surrounds the dental/enamel organ and condenses to form the dental sac or the dental follicle

34. Cap Stage of Tooth Development
Dental (enamel) organ
Dental papilla
dental follicle
Tooth germ
©Copyright 2007, Thomas G. Hollinger, Gainesville, Fl
Oral Histology, 5th edition, A R Ten Cate

35. Cap Stage
©Copyright 2007, Thomas G. Hollinger, Gainesville, Fl

36. Cap stage
together the enamel organ + dental papilla + dental follicle is considered the developing tooth germ or tooth primordium
these primordium will be housed in the developing dental arches and will develop into the primary dentition

37. Cap stage
Enamel knots are clusters of nondividing epithelial cells visible in sections of molar cap stage tooth germs.
They play an important role by the cuspal morphogenesis.