Enamel Flashcards
(43 cards)
What are the properties of enamel?
It is acellular, non-vital (no living cells), and non-vascular
What is the origin of enamel?
It is of ectodermal origin
What is meant by saying enamel is somewhat dynamic?
It can be demineralized and remineralized
What is the purpose of the proteins in enamel?
They organize the HA crystals
What is enamel composed of?
94% inorganic (HA), 1% organic (proteins), and 3% water
What major protein is not found in enamel? Which ones are found in enamel?
Collagen is not found in enamel but amelogenins, ameloblastins, enamelin, and tuftelin are found in enamel.
What differs between the rod and interrod enamel?
The orientation is different locking the two together so it resists shear forces
What separates the rod and interrod enamel?
A sheath where the protein component of enamel is located
HA is the most common type of crystal found but there is a good amount of what other type of crystal? What does this cause?
Carbonatoapatite (carbonated apatite). It causes a change in the shape crystal making it so that it doesn’t pack together as well. It is more common in the deeper layers because ameloblasts produce carbonate and it gets integrated into the crystals
What shape are the enamel crystals?
Hexagonal, they are 60-70nm wide and 25-30nm thick, they get bigger as they mature and kind of lose their hexagonal shape and become slightly more rounded
In what direction do the enamel rods run?
Perpendicular to the DEJ
How are enamel rods organized?
In rows, alternating the the direction in which they run.
How much of the rod is surrounded by the sheath?
about 3/4s of the rod
How many ameloblasts contribute to the “keyhole” interrod enamel? How many ameloblasts contribute to one rod?
4 and 1 respectively
What percent of initial enamel deposit is mineralized?
Only about 30%
What causes the initial deposition of enamel?
The pre dentin that is secreted by the odontoblasts
What are the 3 phases of ameloblast maturation?
Pre-secretory (from pre-ameloblasts to ameloblasts), Secretory (deposition of enamel) Maturation (reduction of organic component and increased mineralization via ion transport)
What does the apical end of the ameloblast form when it is in the secretory phase?
Tome’s processes. (Not Tome’s fibers)
T or F: Initial enamel has rods?
False, it is uniform. The interrod enamel starts first forming a pit for the Tome’s processes to form in.
Does the outermost layer of enamel have rods?
No because the Tome’s processes retract as they get to the end. So Tome’s processes equal enamel rods.
What happens after enamel deposition stops?
Ameloblasts return to squat shape, and form a new basal lamina. OEEs and IEEs fuse to make REE. In order to harden the enamel, water and organic component must be removed.
How much time of amelogenesis is spent in maturation?
About 2/3s of the time
What are the two phases that happen during maturation?
Ruffled-during this phase enzymes are secreted into the enamel that break down the protein parts and promote HA crystal growth. Smooth-As the crystals get bigger, it forces the water and broken down proteins out, in order for this to occur the cells change to smooth apical ends
What is the primary enamel cuticle?
The partially mineralized basal lamina
