tooth development - ii man-kyo chung, dmd, phd ([email protected]) assistant professor department...

Tooth Development - II

Man-Kyo Chung, DMD, PhD([email protected])

Assistant ProfessorDepartment of Neural and Pain Sciences

University of Maryland Dental School

Stages of tooth development

1. Bud stage

2. Cap stage

3. Bell stage

4. Appositional stage (mineralization)

5. Root formation

6. Eruption

(epithelial ingrowth into ectomesenchyme)

(further epithelial growth)

(histo- and morpho-differentiation)

(formation of enamel and dentin of crown)

(formation of dentin and cementum of root)

Oral Histology and Embryology by Leslie P. Gartner, 1988

Bud stage

http://www.iob.uio.no/studier/undervisning/histologi/index.php

1

2

34

5

1. oral epithelium2. dental lamina3. tooth bud4. ectomesenchymal cells5. vestibular lamina

Cap stage

1. Enamel organ (=dental organ)

2. Dental papilla

3. Dental sac (=dental follicle)1

2

3


Enamel organ of cap stage

21

3

1) Inner enamel ep

2) Outer enamel ep

3) Cervical loop

4) Stellate reticulum

5) Enamel knot

6) Enamel cord

7) Enamel navel

4

5

6

7

transient structure during cap stage


Bell stage

1. outer enamel ep.2. inner enamel ep.3. stellate reticulum4. stratum intermedium3

2

14


Appositional stage

1. oral ep.2. outer enamel ep.3. stellate reticulum4. inner enamel ep.5. dental papilla6. cervical loop

3

2

1

5

4

6

blood vessels


1. dental papilla2. preameloblasts3. Preodontoblasts4. odontoblasts5. predentin6. ameloblasts 7. dentin8. stratum intermedium9. enamel

3

2

8

5

4

67

9

1http://www.iob.uio.no/studier/undervisning/histologi/index.php

Appositional stage

Development of permanent dentition

Embryonic age

0 1 2 3 4 5 6 7 8 months

Primary incisor

Permanent incisor

bud Cap mineralization of crownbell

bud Cap mineralizationbell

dental lamina

tooth germs of primary teeth

tooth germs of permanent teeth

Hertwig epithelial root sheath (HERS)- Apical extension of cervical loop - Inner+outer enamel ep.- Not making enamel- Framework of root formation

root sheath epithelial diaphragm(size/shape/number of roots)


Formation of roots

Formation of roots


disintegrated

cementum

odontoblasts root dentin

cementoblasts

fibroblastsosteoblasts

periodontal ligament

alveolar bone

1. Formation of root dentin by odontoblasts2. Disintegration of HERS3. Migration of ectomesenchymal cells from dental sac to the root dentin

through the disintegrated HERS4. Differentiation of ectomesenchymal cells into cementoblasts and

fibroblasts5. Formation of cementum and collagen fibers- cementoblasts : secret cementoid (matrix) and mineralize cementum on

root dentin- fibroblasts : synthesis of collagen fibers of periodontal ligament* Sharpey’s fiber : collagen fibers embedded in cementum

Formation of roots

odontoblasts

cementoblasts

cementum

dentindental sac

HERS

dental sac cells becoming

cementoblasts

4

1

3

2

5

Nerves within tooth pulp

• Sensory and sympathetic nerves

• Form subodontoblastic plexus

• Project into dentinal tubules• No motor and

parasympathetic nerves

Sensory nerve terminals within mouse tooth pulp

Cap stage : axons enter dental follicle

Bell stage : axons enter dental papilla following the initiation of dentinogenesis

dentin

dental follicle

axon

axon

http://www.anat.ucl.ac.uk/research/arnett_lab/

1 mm

4

1

23

5

6

1. oral ep.2. connective tissue3. alveolar bone4. Enamel5. Dentin6. HERS

Tooth eruption

Tooth eruption


1 mm

• Axial movement toward oral epitheliumbegin when the root formation begin.• Source of erupting force : contraction of fibroblasts generating periodontal ligaments?

Tooth eruption

reduced enamel ep.

osteoclasts

Alveolar bone and connective tissueare resorbed as teeth erupt.


Changes in epithelium during eruption

reduced enamel ep.

enamel cuticle

oral ep.

junctional ep.

Periodontal tissues

Junctional ep

oral ep

Periodontal ligament

Alveolar bonehttp://www.iob.uio.no/studier/undervisning/histologi/index.php

Relationship of primary teeth and succedaneous permanent teeth

s

open apexresorption of rooterupting erupting

D : deciduous toothP or S : succedaneous tooth

Summary of tooth development

Oral epithelium

Dental lamina

ameloblastsInner enamel ep

Stellate reticulum

Stratum intermedium

Outer enamel ep HERS

Ectomesenchyme

Dental sac

Dental papilla odontoblasts

cementoblasts

fibroblasts

fibroblasts

osteoblasts

dentin

cementum

pulp


alveolar bone

enamel

guide root formation

oral epithelium

reduced enamel ep junctional ep.

Most odontogenic epithelial cells degenerate following the completion of tooth formation

Oral epithelium

Dental laminaDental lamina

ameloblastsameloblastsInner enamel ep

Stellate reticulum

Stratum intermedium

Outer enamel ep HERSHERS

Ectomesenchyme

Dental sac

Dental papilla odontoblasts

cementoblasts

fibroblasts

fibroblasts

osteoblasts

dentin

cementum

pulp


alveolar bone

enamel

guide root formation

oral epithelium

junctional ep.reduced enamel ep.reduced enamel ep.

Remnants of odontogenic epithelial cells

• Dental lamina epithelial pearl

• Dental lamina epithelial pearl

• HERS epithelial rests of Malassez in periodontal ligament

• Potential etiology of pathological conditions- Supernumenary teeth- Odontogenic cysts- Odontogenic tumors (ex: ameloblastoma)

Remnants of odontogenic epithelial cells

Molecular mechanism of tooth development

• Many genes control tooth development but not completely understood– shape, number of cusp (incisor vs molar)– size – number (2 vs 3 molars…..)– location (mesio-distal, maxillo-mandibular….)– timing of formation and eruption

• Future of dentistry?– Control the number and location of teeth– In vitro formation of tooth

Further studies

<Must >1. Oral Histology and Embryology by Leslie P. Gartner, 1988. Chapter

1-2.2. University of Maryland BCDS learning center

a. Odontogenesis I - Development of the Enamel Organ b. Odontogenesis II - Appositional Stage - Development of the Crown c. Odontogenesis III - Appositional Stage - Development of the Root d. Tooth Development Practical III

<Strongly recommended>1. Ten Cate’s Oral histology by Antonio Nanci, 7th Ed., Elsevier, 2008. 2. The cutting-edge of mammalian development; How the embryo makes

teeth. Nature Reviews, 5:499-508, 20043. Biomineralization during early stages of the developing tooth in vitro

with special reference to secretory stage of amelogenesis. Int J Dev Biol, 39:203-212, 1995.

Acknowledgements

The images in the lectures are derived from these websites with permission.

• University of Oslo, Oral and Craniofacial Histology web site• Dr. Tim arnett at the University College of London• Oral Histology and Embryology by Leslie P. Gartner, 1988.• University of Maryland BCDS learning center

Question?

Man-Kyo Chung, DMD, PhD([email protected])

Assistant ProfessorDepartment of Neural and Pain Sciences

University of Maryland Dental School

Question #1

The hardest tissue found in the oral cavity is:

A. enamel B. dentinC. cementumD. boneE. enamel cuticle

Question #2

The dental lamina:

A. appears at 12 weeks of gestationB. is synonymous with the vestibular

laminaC. is derived from neural crest materialD. is derived from ectodermE. will give rise to cementum

Question #3

Collagen in not the major component of matrix of:

A. dentin B. enamel C. cementum D. periodontal ligament

Question #4

One of the following is not present in the bell stage of tooth development:

a. outer enamel epitheliumB. inner enamel epitheliumC. stellate reticulumD. stratum intermediumE. enamel knot

Question #5

Cementogenesis starts prior to : A. amelogenesis B. dentinogenesis C. disintegration of dental lamina D. formation of apical foramen E. disintegration of Hertwig’s epithelial root sheath

Question #6

Two of the following is not the product of dental sac: A. dentinB. cementumC. alveolar boneD. periodontal ligamentE. enamel

Question #7

One of the following is not the component of tooth germ:

A. Dental papillaB. Enamel organC. Dental follicleD. Vestibular lamina

Question #8

One of the following remains after the completion of tooth development:

A. amelogeninB. Hertwig’s epithelial rooth sheathC. ameloblastsD. odontoblasts

Question #9

Which one of the following is derived from ectomesenchyme?

A. AmeloblastsB. OdontoblastsC. Stellate reticulumD. Stratum intermediumE. Reduced enamel epithelium

Question #9

Which one of the following is derived from ectomesenchyme?

A. AmeloblatsB. OdontoblastsC. Stellate reticulumD. Stratum intermediumE. Reduced enamel epithelium

Question #10

Odontoblasts are characterized byA. being located on external surfaces of rootsB. being shed from the tooth at the time of eruptionC. differentiating first at the cervical region of a forming

toothD. secreting a non-fibrous matrix composed of chains of

amino acidsE. possessing long cytoplasmic processes which lie within

dentinal tubules

Question #11

The pulp chamber of a mature tooth containsA. Cells that form periodontal ligamentB. An enamel lining for thermal protectionC. Blood vessels and nervesD. cementoblastsE. ameloblasts

tooth development - ii man-kyo chung, dmd, phd ([email protected]) assistant professor department...

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