Enamel Flashcards
(57 cards)
What is enamel and what is the precursor cell?
Specialized covering over teeth developed from mandibular epithelium.
The precursor cell is called an ameloblast.
During tooth eruption, ______ are removed.
Ameloblast
Enamel is what color?
Translucent/ light yellow to gray-white
from 2.5 mm to very thin
Enamel is thinnest at the _______ and thickest at the ________.
Gingival line (CEJ), Crown cusp
Enamel is highly mineralized. True or false?
True
What are the 3 main components of enamel ?
How does the ratio of these components contribute to the physical properties of enamel?
96% mineral
3% Water
1% Organic Material
Makes enamel hard and BRITTLE
Where does the ___ % of organic material in enamel come from?
1% ; It is a proteins of pre-enamel left behind after mineralization of the other 96% has occurred
This 1% contains TRAP (tyrosine-rich amelogenin) and nonamelogenin proteins where are a family of SECRETORY proteins that form the matrix that then will become mineralized to become mature enamel.
What is the ____% of inorganic material in enamel made of?
Crystalline calcium or carbonated phosphate
hydroxyapatite
______ is a necessary base or enamel fracture.
Dentin
How can enamel fracture?
Caries or improper cavity preparation
Enamel and dentin are separated layers.
NO! They are confluent.
The basic unit of the enamel is the _______. Surround it is the ________.
Rod, Inter-Rod Region
Rods are cylinders surrounded by inter-rod enamel wrapping around them
Enamel rod and interrod are both made of _____________ that can be ____ wide and ____ long.
Long crystals made of hydroxyapatite
60-70 nm (0.06-0.07 micrometer)
>100 micrometer
What is the difference between rods and interrods?
The direction they run! Rods run parallel. Interrods go at an angle leaning onto the rods as they wrap them
How are enamel crystals formed?
They form from the first layer of pre-enamel (proteins) that can be mineralized by calcium.
As enamel grows, the crystals become hexagonal due to the structure of calcium phosphate.
In the most mature state that enamel crystals are pushed together. They become organized as rod or inter-rod enamel depending on where they are secreted.
NO NEED TO KNOW CALCIUM PHOSPHATE CHEMISTRY
Aside from 96% _________, 3%______ and 1%________, what else can be found in enamel?
Hydroxyapatite crystals
Water
Protein from pre-enamel left behind
Ions: Flouride, Mg, Strontium, Lead
Acid can dissolve enamel crystals.
What is the major enemy of enamel?
Acid
Enamel starts out as organic material and becomes inorganic when it gets _______.
Mineralized
What is a rod sheath and what is it made of?
The region between the rod and interrod region.
More organic material in rod sheath (water and amelogenin pre-enamel matrix protein)
Rod and interrod are continuous with each other; they are not completley different structures
At the end of enamel maturation, organic material is removed and the remnants are present mostly in the _________.
Rod Sheath
What are the 3 steps of amelogenesis ?
- Presecretory - Inner Enamel Epithelium
Cells differentiate and become protein secreting ameloblasts.
- Secretory
Ameloblasts make and organize enamel
- Maturation
Remove organic material and transport ions for mineral deposition
Which stage of amelogenesis determines tooth morphology via the production of rods and interrods ?
Secretory
From the secretary stage to late maturation, water content_________, mineral content_________ and protein content________.
(Increases/decreases)
Decreases
Increases (29% to 95%)
Decreases (66% to 4%)
Amelogenesis requires _______ which is involved with _________ induction.
Describe this process.
Dentin ; Reciprocal
Inner Enamel Epithelium stimulates dental papilla to become odontoblasts which form dentin. Dentin production then stimulates inner enamel epithelium (presecretory ameloblasts) to become secretory ameloblasts
