Enamel 2 Flashcards
What are the enamel proteins?
1) amelogenin
2) Amloblastin
3) enamelin
What does amelogenin do?
- main protein in developing enamel
- only expressed while enamel is being produced
- restris lateral HA crystal growth, preventing fusion
- loss of function = no rods
What does amloblastin do?
- 10% of enamel organic content
- expressed all the what thru maturation
- no Expression = loss of adherence for ameloblasts
What does enamelin do?
- least abundant but largest
- only present at leading edge of enamel disposition
- loss of function = no enamel
What makes up the organic enamel component?
- Enamelysin
- enamel matrix serine proteases
What does enamelysin do?
- MMP
- essential in removing ameloblastin and enamelin
- loss of function = thin, immature enamel
What does enamel matrix serine protease do?
- secreted during modulation
- degrades amelogenins
- loss of function = immature enamel
How does enamel etch?
- from the inside out
What are the types of etching?
- 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
What are the different types of enamel wear?
- 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)
What are some changes that happen in enamel as one gets older?
- Color: gets darker, thinner enamel, staining
- water content decreases, crystals enlarge and decrease pore size
- brittleness increases
- decrease permeability
- increase caries resistance
What is the stria of Retzius?
- 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
What is the neonatal line?
- most accentuated stria of retzius
- reflects physiological changes occurring during birth
- found in all primary teeth, sometimes cusps of first permanent molars
What is the perikymata?
- visible on the enamel surface
- they are surface manifestation of stria of retzius
- shallow furrow were stria interest surface
What are cross striations?
- run at a right angle to the rod direction
- relatively close together; enamel growth rate –> 4 micrometers/day
- may indicated crystal variation in rods
What are the bands of Hunter-Schreger?
- optical phenomenon due to differential light scattering when adjacent groups of rods alternate direction
- appear as alternating light/dark bands
What is gnarled enamel?
mostly seen around the DEJ under the cusps/incisal area short distance to the enamel
- formed from a complex twisting of rods as they proceed vertical away from the DEJ
- “twisting of vertically directed rods around a small diameter ring
What are Enamel Tufts?
- Project about 1/3 into the enamel, do not arch the top
- contain more enamel proteins and are hypo calcified
- perhaps caused by changes in enamel rod direction
- due to over crowding of ameloblasts
- Allows enamel to have some ‘give’, preventing fractures
What are enamel Lamellae?
- appear as cracks
- contain organic material proteins
- Developmental: area where enamel proteins not completely removed or trapped bits of enamel organs
- Many function to give enamel more structural support
What are enamel Spindles?
- Result from odontoblastic processes that traverse the DEJ and penetrate enamel
- proceed only a short distance into enamel
- often appear at incised and cusps tips
THEY ARE NOT ENAMEL, MAY HAVE SMALL TRACES OF DENTIN
