Amelogenesis

Question 1

recipriocal induction

Answer 1

between the epithelial cells of the enamel organ and the mesenchymal cells of the dental papilla
**ameloogenesis happens AFTER dentinogenesis at the crown stage. Dentin must be present for enamel to be formed and dentinogenesis must have ameloblasts to happen

Question 2

what is the two step (basic process) of forming enamel

Answer 2

1. secrete an immature (partially mineralized) enamel that is 30% inorganic and 70% organic and water
   once the width is sufficient of these type of enamel…
2. influx of additional minerals coincident with the removal of organic material and water (secretory and maturation phases in this step)

Question 3

what does enamel formation need?

Answer 3

ameloblasts (inner cells enamel organ), alkaline phosphastase (stratum intermedium enamel organ layer) and blood supply from the dental follicle of the tooth germ

Question 4

what are the first cells to differentiate into ameloblasts and where do they move?

Answer 4

coronal most inner layer of enamel organ and go apically to the cervical loop

Question 5

there are 3 stages and 9 phases of amelogenesis, what are they?

Answer 5

1. presecretory stage
   -has the morphogenetic phase and the histodifferentiation phase
2. secretory stage
   -has the inner immediately mineralized secretion, interrod substance secretion, rod secretion, maturation phase, outer mineralized secretion and final ameloblast secretion phases
3. Postsecretory stage
   protective phase (REE)

Question 6

at the morphogenetic phase, what is seen between the inner cells of the enamel organ and the periphery cells of the dental papilla?

Answer 6

clear or acellular layer

Question 7

in the histodifferentiation stage, what happens?

Answer 7

the ameloblasts and ODB form, so the acellular (clear) layer is gone

Question 8

explain the inner rodless enamel layer

Answer 8

• immediately mineralized, ultra-thin layer, smooth because only crystals and no rods (next to/touching dentin)
• *basically the DEJ

Question 9

explain the interrod substance secretion

Answer 9

-the distal end of the ameloblast changes to become tomes process (not smooth anymore). The tomes processes then secrete interrod substance that encircle the tomes processes. When the interrod substance is layed down, a rod is formed inside.

Question 10

what kind of enamel is from the interrod to the surface?

Answer 10

immature

Question 11

tomes pit

Answer 11

initially occupied by the tomes process

Question 12

what is interrod substance made of?

Answer 12

70% organic and 30% inorganic (opposite of mature enamel)

Question 13

explain rod substance secretion

Answer 13

ameloblast moves towards “surface enamel” and the tomes process is dragged with it leaving a partially mineralized rod in tomes pit. continues until rod and interrod length reached (2.5mm))

• *at this point only inner rodless enamel is mature
• *rods and interrod substance are immature

Question 14

what are the dark dots indicative of?

Answer 14

mark junction between the body and tomes processes of the ameloblasts

Question 15

maturation phase

Answer 15

during the maturation phase the distal end of teh ameloblasts alternates btwn a smooth and an uneven border. smooth border ameloblasts removes (resorbs) organic material and ruffled border means that ameloblast is secreting mineral salts (inorganic)

• *maturation of enamel complete when inorganic is 96% and organic is 3%
• *tomes process not present

Question 16

outer rodless layer

Answer 16

mineralized immediately (not secreted by tomes process) so no enamel rods

• **last mineralized secretion of ameloblasts, but not last secretion total
• *everything is mineralized below the outer rodless layer

Question 17

final ameloblast secretion

Answer 17

the basal lamina (non-mineralized) that connects permanently to the outer rodless enamel and attached to the REE
***important for eruption into the mouth

Question 18

Reduced Enamel Epithelium

Answer 18

remnant of enamel organ and protector of enamel until the tooth enters the oral cavity
-becomes junctional epithelium

Question 19

how long does the maturation phase take n permanent teeth?

Answer 19

5 years

Question 20

initial and complete enamel mineralization timeline for all permanent teeth

Answer 20

birth to 9 years (initial) and 5 to 14 years for it to be complete