Amelogenesis Flashcards
What is amelogenesis
Formation of enamel
Enamel definition
Composite biological mineral with apatite crystals oriented in a complex three-dimensional pattern
When does amelogenesis occur?
After dentinogenesis begins in the crown stage of odontogenesis
What must be present for enamel to form?
Dentin
What is required for odontoblast to be differentiated?
Ameloblasts
What makes enamel unique compared to the other 3 mineralized tissues?
It does not have an unmineralized preenamel stage
What does enamel formation require?
- Specialized cells (ameloblasts)
- Alkaline phosphatase
- Rich blood supply
Where is alkaline phosphatase located?
Stratum Intermedium layer of enamel organ
What is the first area of the tooth to develop enamel?
The coronal-most area of the inner layer of the enamel organ
The process continues apically toward the cervical loop
What are the stages of enamel formation?
1) Presecratory stage
2) Secretory stage
3) Postsecratory stage
What are the phases of the Presecratory stage?
Morphogenetic stage
Histodifferentiation phase
What are the phases of the Secretory stage?
Inner mineralized phase Interrod substance secretion phase Rodsecretion phase Maturation phase Outer immediately mineralization secretion Final Ameloblast secretion phase
What are the phases of the postsecretory stage?
Protective phase
What occurs during the Morphogenetic phase?
Clear or acellular layer is seen between the inner cells of the enamel organ and the peripheral cells of the dental papilla
What occurs during the Histodifferentiation phase?
Ameloblasts extend down to clear layer, touch the peripheral cells of the papilla, and then grown the other way
When the ameloblasts touch the peripheral cells, it causes them to differentiate to odontoblasts
Do ameloblasts or odontoblasts secrete firsts?
Odontoblasts
What occurs during the inner mineralized
Inner rodless enamel is secreted and immediately mineralized
It is secreted on top of the DEJ
There are no rods here, but it is still enamel - it is so the rods do not touch dentin
Distal portions of ameloblasts are smooth
What occurs during the Interrod substance secretion phase?
Distal portions of ameloblasts go form smooth to a Tomes’ process
Tomes’ processes of adjacent ameloblasts secreted the interrod substance that secretes encircles Tomes’ processes
Tomes’ pit
The space that is initially occupied by Tomes’ processes until the ameloblasts move
What is the structure of interrod substance when it is secreted?
Partially mineralized
What is the content of partially mineralized substances?
70% organic and water
30% inorganic
What are the walls of Tomes’ pits made of?
Interrod substance
What occurs during Rod secretory phase?
Tomes’ process moves out of the pit as the ameloblast moves toward the future enamel surface
As the process withdraws, it secretes partially mineralized rods into the pits
This continues until the length of the immature interrod substance and rod is reached
What occurs before the maturation phase begins?
The rod and interrod enamel is partially mineralized and the distal end of the ameloblast is Tomes’ process
What occurs during the maturation phase?
The distal end of the ameloblasts alternates between an even/smooth edge and an uneven/ruffled edge
What is occurring when the ameloblast distal edge is even/smooth?
The ameloblast is resorbing or removing organic material and water
What is occurring when the ameloblast distal edge is ruffled/uneven?
The ameloblast is secreting mineral salts (inorganic substances)
When is the maturation phase complete?
Inorganic material reaches 96%
Organic material reaches 1%
Water reaches 3%
What occurs during outer mineralized phase?
The outer rodless enamel is secreted
T/F - the outer rodless enamel is the final secretion of an ameloblast?
False - it is the last mineralized secretion, but not the last secretion
What occurs in the final ameloblast secretion phase?
The basal lamina is secreted by the ameloblasts
Basal lamina
Final secretion by ameloblasts
Nonmineralized
Stuck to the outer rodless enamel
What occurs in the Protective phase?
The four cell layers of the enamel organ come together to form the reduced enamel epithelium
Reduced enamel epithelium
Protective layer of the enamel that becomes the junctional epithelium during the emergence of the tooth into the oral cavity
Attached to the enamel by the basal lamina
How long does maturation phase take for permanent teeth?
5 years
