Teeth

The tooth development begins in the 6th week as U-shaped thickenings of the oral epithelium. These structures, called dental laminae, are placed along the length of the upper and lower jaw. Dental laminae soon give rise to the ten proliferation centers called tooth buds which penetrate into underlying mesenchyme. Tooth buds soon develop a cup-shaped enamel organ due to the invagination of the mesenchyme condensation called the dental papilla. The enamel organ consists of the inner and outer enamel epithelium and enamel reticulum, while dental papilla contains dense collection of stelate cells that will give rise to the most of the tooth proper, including the pulp cavity, dentin and blood supply for the teeth. Enamel organ and dental papilla are surrounded by a mesenchyme condensation called the dental sac.
Cells of the inner enamel epithelium differentiate into ameloblasts, which produce the enamel.


Tooth - 8th week


Tooth - 10th week



1. Dental lamina
2. Oral epithelium
3. Tooth bud
4. Jaw mesenchyme

 

 

 

 

 


1. Inner enamel epithelium
2. Dental papilla
3. Outer enamel epithelium
4. Dental lamina


 

 

 


The mesenchymal cells in the dental papilla adjecent to the inner enamel epithelium differentiate into odontoblasts, which produce predentin and deposit it adjecent to the inner enamel epithelium. During the 6th month, the predentin calcifies and becomes the dentin.
The formation of the root of the tooth begins when the inner and outer enamel layer penetrate into the underlying mesenchyme and form the epithelial root sheath. The odontoblasts adjecent to it form a continuos layer of dentin. The inner cells of the dental sac differentiate into cementoblasts which produce the cementum.



Tooth - 3rd month



1. Stellate reticulum
2. Odontoblasts
3. Ameloblasts
4. Dental sac
5. Dental papilla



The eruption of the deciduous or milk teeth occurs 6 to 24 months after birth. The buds for the permanent teeth are located on the lingual aspect of the milk teeth and are formed during the 3rd month of the development. The tooth buds for the permanent teeth with deciduous predecessor develop from deep continuations of the dental lamina at about the 10th fetal weeks. The permanent molars with no deciduous predecessors develop as buds from the posterior extensions of the dental laminae.



Tooth - 6th month



1. Stellate reticulum
2. Ameloblasts
3. Enamel
4. Epithelial root sheath
5. Odontoblasts
6. Dentine
7. Dental pulp