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Tooth germ tissues

1. Ectodermal (epithelial) 2. Mesodermal (mesenchymal - CT)

What part of tooth forms first, the crown or root?


Which occurs first in development, shape or layers?

shape occurs first and then tissues are laid down to form layers

What must be completed before Cytodifferentiation can occur?



process of tooth development resulting in tooth's shape


process of differentiation of special cells to form enamel, dentin, cementum and pulp

Tooth development moves from

the incisal/occlusal/cup tip and moves apically toward root

Tooth development begins during

the sixth and seventh week of fetal development

Which teeth development first, anterior or posterior?



tooth forming/developing

Three stages of morphodifferentiation

1. Bud stage (8th wk) 2. Cap stage (9th - 10th wk) 3. Bell stage (11th - 12th wk) (none can happen until have jaw and arch appearance)

Three parts of tooth germ

1. Enamel organ 2. Dental papilla 3. Dental sac/follicle

Enamel organ develops from

ectodermal (epithelial)

Dental papilla develops from

mesodermal (CT)

Dental sac/follicle develops from

mesodermal (CT)

Enamel organ makes


Dental papilla makes

dentin and pulp

Dental sac/follicle makes

alveolar bone proper, periodontal ligament and cementum

Cells that make enamel


Cells that make dentin


Cells that make pulp


Cells that make alveolar bone proper


Cells that make PDL


Cells that make cementum


Dental papilla is located

under the enamel organ

Dental sac/follicle surrounds

the enamel organ and dental papilla

Alveolar bone proper lays

next to or connects to tooth

When tooth starts to erupt

the apical 1/3 of root is not formed yet

Completion of morphodifferentiation occurs

when the Bell stage is complete (have complete crown shape of tooth)

Four layers of enamel organ

1. Inner enamel epithelium 2. Stratum intermedium 3. Stellate reticulum 4. Outer enamel epithelium

Inner enamel epithelium

differentiates into ameloblasts the form enamel matrix. epithelial cells communicate with dental papilla

Stratum intermedium

supports the production of enamel matrix

Stellate reticulum

supports the production of enamel matrix

Outer enamel epithelium

serves as protective barrier for enamel organ

Enamel organ

formation of tooth bud in a cap shape with deep central depression

Dental papilla

condensed mass of mesenchyme within the concavity of the enamel organ

Dental sac/follicle

condensed mass of mesenchyme surrounding the enamel organ

Each individual tooth germ

must attach to epithelial tissue

First communication is

morphodifferentiation (instructs oral epithelium to thicken and grow down into CT to shape the tooth)

Inner enamel epithelial cells

cytodifferentiate into ameloblasts to lay down enamel

Steps of Morphodifferentiation

1. must have epithelial tissue and CT with cells communicating 2. oral epithelium thickens and grows down into CT forming a bud 3. tooth germ now connected to oral epithelium by dental lamina 4. continues growing apically and outward forming a cap 5. continues growing until crown shape is complete (bell stage) 6. cytodifferentiation can now begin in the crown

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