Amelogenesis Flashcards
what are 3 Proteins and their associated genes Contributing to Appositional Growth in Thickness of the Enamel Layer
1) amelogenin= AMELX, AMELY
2) enamelin =ENAM, 4q21
3) ameloblastin =AMBN, 4q21
amelotin and gene?
AMTN
*Proteins Related to Basal Lamina Covering Maturing and Mature Preeruptive Enamel
Tuftelin
legacy protein
proteinases: enamelysin, MMP20, kallikrain4
Proteins Involved in Postsecretory Processing and Degradation of Amelogenins and Nonamelogenins
what do teeth look like when enamel formatio nis disturbed?
teeth become characterized by
distinctive bands of malformed enamel
what do teeth look like with tetracycline-induced disturbances?
Tetracycline antibiotics are incorporated into mineralizing tissues LIKE ENAMEL
*result in a band of brown pigmentation or even total pigmentation. Hypoplasia or absence of enamel also may occur
what do teeth look like with fluoride ion can interference?
- Chronic ingestion of fluoride ion concentrations in excess of 5 ppm
- interferes sufficiently with ameloblast function
- PRODUCES MOTTLED ENAMEL
- very unsightly white patches of hypomineralized and altered enamel but STILL RESISTS CARRIES
What are the genes associated with amelogenesis imperfecta?
AMELX, ENAM, DLX3, FAM83H, MMP-
20, KLK4, and WDR7
What is amelogenesis imperfecta?
3 clinical correlates
X-linked, autosomal inherited defect
- disrupts the structure and clinical appearance of enamel
1) hypoplastic
2) hypocalcified
3) hypomature defective enamel
what is surprising about AMBN gene?
mutant mice show major defects in enamel formation but NO amelogenesis imperfecta has been linked to it
what is amelogenesis? how many steps?
It enamel formation and considered a TWO STEP process
1) secretory stage
* * transitional stage
3) maturation stage
enamel organ is made up of what cell layers in secretory stage of amelogenesis?
1) ameloblasts
2) stratum intermedium
3) stellate reticulum
4) outer enamel epithelium
enamel… basic facts you need to know
- hardestcalcified matris of the body
- cannot renew itself becuz ameloblasts that make it are lost as the tooth erupts
- ALMOST totally absent of organic material
- has extremily long crytals
fully formed enamel is ___% inorganic mineral
96% inorganic mineral and 4% organic material/water
inorganic mineral is composed of?
non-stoichiometric carbonate-substituted hydroxyapatite, contains trace amounts of: fluoride (F), sodium (Na),
magnesium (Mg), zinc (Zn) and strontium (Sr)
why is dentin necessary to maintain enamel?
the high mineral content of enamel makes it hard and able to withstand mechanical force BUT its makes enamel BRITTLE so the underlying RESILIENT layer of dentin is necessary to maintain integrity
what are the fundamental organizational units of mammalian enamel? shape?
1) rods= hexagonal and prism-LIKE (rods do
not have a regular geometry and hence are not prismatic)
2) interrod= interprismatic substnace
Enamel is built from closely packed and long, ribbon-like?
carbonate apatite crystals
*measuring 60-70nm in width and 25-30nm in thickness AKA REALLY LONG
young vs old enamel?
- young= hexagonal symmetry
- old= no longer hexagonal but exhibit an irregular outline as they press together ( grouped together as rod or interrod enamel)
tomes processes
location of rods and interrods
distal end of cells
*when ameloblasts deposit and mineralize matrix and retreat from DEJ
RODS ON DISTAL TIP
INTERROD ON PROXIMAL SIDES
During the long-lasting process of enamel maturation, ameloblasts cyclically change structure and function between?
ruffled ended (RA) and smooth-ended (SA) ameloblasts!!!
difference between ruffled-ended (RA) and smooth-ended (SA) ameloblasts?
- *RA= add mineral to the immature enamel
* SA= removes degraded matrix proteins and water
During maturation, an additional 25% of the cells ____?
die
Once mineralization is complete, the ameloblasts again shorten and become?
protective (reduced) ameloblasts
FIRST during the pre-secretory stage, differentiating ameloblasts acquire?
*phenotype
*change polarity
*develop an extensive protein synthetic
apparatus
*prepare to secrete the organic matrix of enamel
SECOND during the secretory stage ameloblasts
elaborate and organize the entire enamel thickness = very ordered tissue
THIRD during the maturation stage, ameloblasts
modulate and transport specific ions
Enamel formation begins when?
involves?
early crown stage
*involves the differentiation of IEE first at the tips of the cusp
enamel formation starts?
at the tips of cusps and then goes down the slopes of the crown until all cells of the epithelium have differentiated into ameloblasts
differentiating ameloblasts are located where?
away from the blood vessels that lie outside the IEE
