INDIAN DENTAL ACADEMY
Leader in continuing dental education
www.indiandentalacademy.com

www.indiandentalacademy.com
Tooth Development

Karen Lyons, PhD
2641 MacDonald Research Laboratories
klyons@mednet.ucla.edu
825-5480
www.indiandentala...
epithelial mesenchymal interactions
epithelium

apical

basal
basal lamina
(ECM)
mesenchyme
tight junction
adherens unctio...
Determination of tooth region
Oral ectoderm
(dental epithelium)

Jaw mesenchyme

Nonoral ectoderm
(nondental epithelium)
w...
Determination of tooth region
Dental lamina
(region of thickened
epithelium)

www.indiandentalacademy.com
Formation of tooth buds
oral ectoderm

dental mesenchyme

dental lamina
mesenchymal
Tooth placode condensation

Future cro...
Dental lamina

Bud stage

Bell stage
www.indiandentalacademy.com
Tissue recombination experiments reveal sources of
secreted factors that control tooth development at
different stages
ora...
Ectodermal signals are required for the initiation of
tooth development
oral ectoderm

Tooth formation
nondental mesenchym...
The sources of secreted signals that control tooth
development shift between epithelium and mesenchyme
Dental lamina
epith...
Pax9:

Transcription factor

PAX9+/- humans have oligodontia

Bud stage

Bell stage
Pax9-/- mice:
Tooth development is
arr...
Msx1:

Transcription factor
Expressed in dental mesenchyme
Required for tooth formation

MSX1+/- Humans have
oligodontia

...
Pax9 and Msx1 are
expressed in dental
mesenchyme

Dental lamina (epithelium) is
the source of the secreted
signal(s) contr...
Hypothesis: The dental lamina is the source of a
secreted signal that induces expression of Pax9 and
Msx1 in the underlyin...
Secreted factors involved in tooth formation
Fibroblast growth factors (FGFs)

Bone morphogenetic proteins (BMPs)

www.ind...
Ectodermal signals are required for the initiation of
tooth development
oral ectoderm
Mice lacking Pax-9 or
Msx1 do not fo...
FGF8 is an epithelial signal required for initiation of
tooth development
oral ectoderm
Pax-9
Msx1

Mice lacking Pax-9 or
...
FGF8 is expressed throughout entire dental epithelium
Dental epithelium

Pax-9

Pax-9
Jaw mesenchyme

Nondental
epithelium...
Positioning of sites of tooth formation: antagonistic
signaling of FGF8 and BMP4
Dental epithelium

Pax-9

Pax-9
Jaw mesen...
The sources of secreted signals that control tooth
development shift between epithelium and mesenchyme
Dental lamina
Epith...
LEF1 is a
transcription
factor

The development of
teeth in LEF1-/mice is arrested at
the bud stage

LEF1 is expressed in ...
Bud stage
BMP4 is an essential mesenchymal signal for tooth bud
development

How is BMP4
expression induced
in the mesench...
FGF8
Pax9

BMP4

Pax9 induces expression of BMP4 in the
condensing mesenchyme
www.indiandentalacademy.com
LEF1

Pax9

BMP4

BMP4 produced in the dental mesenchyme induces
LEF1 expression in the epithelium
www.indiandentalacademy...
The sources of secreted signals that control tooth
development shift between epithelium and mesenchyme
Dental lamina
Epith...
Reciprocal signaling during early stages of
tooth development
Bud stage

Initiation stage

Epithelial Signaling

BMP4
(+ F...
Control of tooth shape

epithelium

molar
mesenchyme

www.indiandentalacademy.com

incisor
The enamel knot is the source of secreted signals
that cause proliferation of neighorbing epithelial
cells
Bud stage
mesen...
The enamel knot is
induced by BMP4
BMP4

The enamel knot
produces FGFs that
stimulate
proliferation of
adjacent epithelium...
SUMMARY
Reciprocal inductive interactions between
epithelium and mesenchyme control tooth
morphogenesis

FGF8 is an epithe...
BMP4 is an inhibitory signal (secreted by epithelium)
at early stages of tooth initiation
BMP4 is a stimulatory signal (se...
Thank you
For more details please visit
www.indiandentalacademy.com

www.indiandentalacademy.com
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Tooth development /certified fixed orthodontic courses by Indian dental academy

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The Indian Dental Academy is the Leader in

continuing dental education , training dentists

in all aspects of dentistry and offering a wide

range of dental certified courses in different

formats.

Indian dental academy provides dental crown &

Bridge,rotary endodontics,fixed orthodontics,
Dental implants courses.for details pls visit

www.indiandentalacademy.com ,or call
0091-9248678078

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Tooth development /certified fixed orthodontic courses by Indian dental academy

  1. 1. INDIAN DENTAL ACADEMY Leader in continuing dental education www.indiandentalacademy.com www.indiandentalacademy.com
  2. 2. Tooth Development Karen Lyons, PhD 2641 MacDonald Research Laboratories klyons@mednet.ucla.edu 825-5480 www.indiandentalacademy.com
  3. 3. epithelial mesenchymal interactions epithelium apical basal basal lamina (ECM) mesenchyme tight junction adherens unction www.indiandentalacademy.com
  4. 4. Determination of tooth region Oral ectoderm (dental epithelium) Jaw mesenchyme Nonoral ectoderm (nondental epithelium) www.indiandentalacademy.com
  5. 5. Determination of tooth region Dental lamina (region of thickened epithelium) www.indiandentalacademy.com
  6. 6. Formation of tooth buds oral ectoderm dental mesenchyme dental lamina mesenchymal Tooth placode condensation Future crown invagination Bud stage Future root Bell stage www.indiandentalacademy.com
  7. 7. Dental lamina Bud stage Bell stage www.indiandentalacademy.com
  8. 8. Tissue recombination experiments reveal sources of secreted factors that control tooth development at different stages oral ectoderm oral ectoderm ? jaw mesenchyme nondental mesenchyme nonoral ectoderm nonoral ectoderm ? www.indiandentalacademy.com nondental mesenchyme jaw mesenchyme
  9. 9. Ectodermal signals are required for the initiation of tooth development oral ectoderm Tooth formation nondental mesenchyme nonoral ectoderm no tooth formation jaw mesenchyme The ectodermal signal is a secreted factor www.indiandentalacademy.com
  10. 10. The sources of secreted signals that control tooth development shift between epithelium and mesenchyme Dental lamina epithelium Bud stage mesenchyme Bell stage epithelium www.indiandentalacademy.com
  11. 11. Pax9: Transcription factor PAX9+/- humans have oligodontia Bud stage Bell stage Pax9-/- mice: Tooth development is arrested at Bud stage www.indiandentalacademy.com
  12. 12. Msx1: Transcription factor Expressed in dental mesenchyme Required for tooth formation MSX1+/- Humans have oligodontia Msx1-/- mice: Tooth development is arrested at Bud stage www.indiandentalacademy.com
  13. 13. Pax9 and Msx1 are expressed in dental mesenchyme Dental lamina (epithelium) is the source of the secreted signal(s) controlling tooth formation www.indiandentalacademy.com
  14. 14. Hypothesis: The dental lamina is the source of a secreted signal that induces expression of Pax9 and Msx1 in the underlying mesenchyme. Pax9 Msx1 What is/are the secreted factor(s)? www.indiandentalacademy.com
  15. 15. Secreted factors involved in tooth formation Fibroblast growth factors (FGFs) Bone morphogenetic proteins (BMPs) www.indiandentalacademy.com
  16. 16. Ectodermal signals are required for the initiation of tooth development oral ectoderm Mice lacking Pax-9 or Msx1 do not form teeth Pax-9 Msx1 jaw mesenchyme Remove ectoderm No expression of Pax-9 no tooth or Msx1 development www.indiandentalacademy.com
  17. 17. FGF8 is an epithelial signal required for initiation of tooth development oral ectoderm Pax-9 Msx1 Mice lacking Pax-9 or Msx1 do not form teeth jaw mesenchyme Control bead Bead soaked in FGF8 Pax-9 No Pax-9 induction Pax-9 induction www.indiandentalacademy.com
  18. 18. FGF8 is expressed throughout entire dental epithelium Dental epithelium Pax-9 Pax-9 Jaw mesenchyme Nondental epithelium Why doesn’t the a single continuous tooth form? www.indiandentalacademy.com
  19. 19. Positioning of sites of tooth formation: antagonistic signaling of FGF8 and BMP4 Dental epithelium Pax-9 Pax-9 Jaw mesenchyme (neural crest) Sites of coexpression of FGF8 and BMP4 FGF8 Pax9 www.indiandentalacademy.com BMP4 Nondental epithelium
  20. 20. The sources of secreted signals that control tooth development shift between epithelium and mesenchyme Dental lamina Epithelium FGF8 = +ve signal BMP4 = antagonistic Bud stage mesenchyme Bell stage epithelium www.indiandentalacademy.com
  21. 21. LEF1 is a transcription factor The development of teeth in LEF1-/mice is arrested at the bud stage LEF1 is expressed in the epithelium Source of secreted signal controlling tooth formation www.indiandentalacademy.com
  22. 22. Bud stage BMP4 is an essential mesenchymal signal for tooth bud development How is BMP4 expression induced in the mesenchyme? LEF1 BMP4 condensed mesenchyme www.indiandentalacademy.com
  23. 23. FGF8 Pax9 BMP4 Pax9 induces expression of BMP4 in the condensing mesenchyme www.indiandentalacademy.com
  24. 24. LEF1 Pax9 BMP4 BMP4 produced in the dental mesenchyme induces LEF1 expression in the epithelium www.indiandentalacademy.com
  25. 25. The sources of secreted signals that control tooth development shift between epithelium and mesenchyme Dental lamina Epithelium FGF8 = +ve signal BMP4 = antagonistic Bud stage Mesenchyme BMP4 = +ve signal Bell stage epithelium www.indiandentalacademy.com
  26. 26. Reciprocal signaling during early stages of tooth development Bud stage Initiation stage Epithelial Signaling BMP4 (+ FGF8) Mesenchymal signaling FGF8 LEF1 Pax-9 www.indiandentalacademy.com BMP4
  27. 27. Control of tooth shape epithelium molar mesenchyme www.indiandentalacademy.com incisor
  28. 28. The enamel knot is the source of secreted signals that cause proliferation of neighorbing epithelial cells Bud stage mesenchyme BMP4 = +ve signal Bell stage enamel knot The enamel knot is induced by BMP4 www.indiandentalacademy.com
  29. 29. The enamel knot is induced by BMP4 BMP4 The enamel knot produces FGFs that stimulate proliferation of adjacent epithelium www.indiandentalacademy.com
  30. 30. SUMMARY Reciprocal inductive interactions between epithelium and mesenchyme control tooth morphogenesis FGF8 is an epithelial signal that positively regulates morphogenesis at the initiation stage FGF8 is an epithelial signal produced by the enamel knot that stimulates proliferation of neighboring epithelial cells to control cusp formation www.indiandentalacademy.com
  31. 31. BMP4 is an inhibitory signal (secreted by epithelium) at early stages of tooth initiation BMP4 is a stimulatory signal (secreted by mesenchyme) at the Bud stage BMP4 induces the formation of the enamel knot Pax9, Msx1, and LEF1 are transcription factors that are required for tooth morphogenesis www.indiandentalacademy.com
  32. 32. Thank you For more details please visit www.indiandentalacademy.com www.indiandentalacademy.com

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