EX1; Amelogenesis Flashcards
True or False
Amelogenesis occurs after dentinogenesis during the crown stage of odontogenesis
True
True or False
Dentin must be present for enamel to be formed
True
True or False
Ameloblasts must be present for dentinogenesis to occur even though denim must be present for enamel to be formed
True
What is the term describing the relationship between the formation of enamel (epithelium) and dentin (mesenchyme)
reciprocal induction
*What is unique regarding enamel and its mineralization phases
it does not have an unmineralized pre-enamel phase
What is formed via a two step process
enamel rods, sheath, and interrod substance
What is the first step in amelogenesis
secretion of an immature or partially mineralized enamel
What is the composition of the immature or partially mineralized enamel
70% organic and water
30% inorganic
Once the what of immature enamel is deposited does the second step occur
width
What is the second step of amelogenesis
significant influx of additional mineral coincident with the removal of organic material and water
What is the enamel described as during the second step
having secretory and maturative phases
*This specialized cell is the differentiated inner cells of the enamel organ
ameloblast
*This is located in the stratum intermedium layer of the enamel organ
alkaline phosphatase
*This is located in the dental follicle part of the tooth germ
rich blood supply; dentin is blocking the blood supply from the dental papillae
Cells in which area of the enamel organ are the first to differentiate into the ameloblasts
coronal most area; it then spreads cervically
What are the three main stages of amelogenesis
presecretory phase
secretory phase
postsecretory phase
What are the two phases of the presecretory phase
morphogenetic phase
histodifferentiation phase
What are the six phases of the secretory phase
inner immediately mineralized secretion interrod substance secretion rod secretion maturation phase outer immediately mineralized secretion final ameloblast secretion phase
What is the phase of the postsecretory phase
protective phase; reduced enamel epithelium
What is the composition of the inner immediately mineralized secretion
ultra-thin inner rodless enamel layer
What is the mineralization content of the interred substance secretion and rod secretion
initially immature or partially mineralized
What occurs during the maturation phase of amelogenesis
removal of organic substances until 1%
removal of water until 3%
influx of mineral salts until 96%
What is the composition of the outer immediately mineralized secretion
ultra-thin outer rodless enamel layer
What is the non-mineralized portion of the final ameloblast secretion phase
basal lamina
What is located between the inner cells of the enamel organ and the peripheral cells of the dental papilla
clear or acellular layer
What cells are formed during the histodifferentiation phase
odontoblasts ameloblasts (columnar epithelial cells)
True or False
The inner rodless (structureless) enamel immediately mineralizes upon secretion
True
During interred substance phase, what happens to the distal end of the ameloblasts
it changes from a smooth configuration to Tomes’ process
What does Tomes’ process secrete
the interrod substance that encircles the Tomes’ process
What is the mineralization state of interrod substance
partially mineralized;
70% organic and water
30% inorganic
Tomes’ pits are made of/surrounded by what
interrod substance
Tomes’ process move out the pit as what occurs
as the ameloblast moves toward the future enamel surface
As the Tome’s process withdraws itself from the pit, what is secreted into the pit
partially mineralized enamel rod
The presence of Tomes’ processes and partially mineralized enamel indicate that the ameloblasts are in which phase
rod secretory
When the distal edge of the ameloblast is even (smooth) what does that mean
the ameloblast is resorbing or removing organic material and water
When the distal edge of the ameloblast is ruffled (rough) why does that mean
the ameloblast is secreting mineral salts (inorganic)
Maturation is complete when what occurs
the inorganic, organic, and water composition reaches the proper composition
When the distal ends of the ameloblast alternates from smooth to rough what does that mean for the Tomes’ process
they are no longer present
True or False
The outer rodless enamel is secreted by Tomes’ processes
False; it is not secreted by them (that’s why it does not contain enamel rods)
*Which is the last mineralized secretion of ameloblasts
outer rodless enamel; it is not the final secretion
*What is the final ameloblast secretion phase
basal lamina
What composes the reduced enamel epithelium
remnant of enamel organ (4 layers) giving protection of enamel until tooth enters oral cavity
What does the reduced enamel epithelium become during emergence of the tooth into the oral cavity
junctional epithelium
What is used to attach the reduced enamel epithelium to the enamel surface
basal lamina
When is the initial mineralization for permanent teeth
birth to 9 years
When is the completed mineralization for permanent teeth
5 to 14 years
