Enamel 2 Flashcards
1
Q
What are the enamel proteins?
A
1) amelogenin
2) Amloblastin
3) enamelin
2
Q
What does amelogenin do?
A
- main protein in developing enamel
- only expressed while enamel is being produced
- restris lateral HA crystal growth, preventing fusion
- loss of function = no rods
3
Q
What does amloblastin do?
A
- 10% of enamel organic content
- expressed all the what thru maturation
- no Expression = loss of adherence for ameloblasts
4
Q
What does enamelin do?
A
- least abundant but largest
- only present at leading edge of enamel disposition
- loss of function = no enamel
5
Q
What makes up the organic enamel component?
A
- Enamelysin
- enamel matrix serine proteases
6
Q
What does enamelysin do?
A
- MMP
- essential in removing ameloblastin and enamelin
- loss of function = thin, immature enamel
7
Q
What does enamel matrix serine protease do?
A
- secreted during modulation
- degrades amelogenins
- loss of function = immature enamel
8
Q
How does enamel etch?
A
- from the inside out
9
Q
What are the types of etching?
A
- Type 1: prefetnial removal of rods, most common
- type 2: interrod enamel removed first, opposite type 1
- Type 3: irregular and indiscrete pattern
- overall probably due to the orientation of rods (perp. to enamel surface) and interrod enamel
10
Q
What are the different types of enamel wear?
A
- Attrition: wear, enamel cannot be replaced
- Abrasion: removed of enamel by abrasive forces (brushing)
- Abfraction: non-carious cervical lesion caused by cyclical loading
- Erosion: removed of enamel by break down of crystal rods (acid)
11
Q
What are some changes that happen in enamel as one gets older?
A
- Color: gets darker, thinner enamel, staining
- water content decreases, crystals enlarge and decrease pore size
- brittleness increases
- decrease permeability
- increase caries resistance
12
Q
What is the stria of Retzius?
A
- longitudinal lines running from the DEJ to the surface; appear best in longitudinal sections
- may delicate cohorts of differentiation or act as rings on a tree for deposition
13
Q
What is the neonatal line?
A
- most accentuated stria of retzius
- reflects physiological changes occurring during birth
- found in all primary teeth, sometimes cusps of first permanent molars
14
Q
What is the perikymata?
A
- visible on the enamel surface
- they are surface manifestation of stria of retzius
- shallow furrow were stria interest surface
15
Q
What are cross striations?
A
- run at a right angle to the rod direction
- relatively close together; enamel growth rate –> 4 micrometers/day
- may indicated crystal variation in rods
