Enamel 2 Flashcards
amelogenins
main protein in developing enamel (80-90%)
only present when enamel is being produced
restricts lateral HA crystal growth, prevents crystal fusion
loss of function: no rods just a blob
ameloblastin
10% of organic content
expressed through maturation
helps ameloblast adhere to developing enamel
loss of function: ameloblast falls off and no enamel
enamelin
least abundant protein (<5%)
only present at leading edge of enamel deposition
possibly plays a role in crystal elongation
loss of function: no enamel
enamelysin
MMP
chops up ameloblastin and enamelin
loss of function: thin immature enamel
removes organic for increased minerlaization
enamel matric serine proteases
secreted during modulation events of enamel maturation
degrades amelogenins
loss of function: immature enamel
Enamel acid etching
cabonated apatitie (center) more vulnerable type 1: dissolve rods type 2: dissolve interrrod enamel type 3: irregular and indiscrimiante patterns most like a difference due to orientation
attition
tooth on tooth
abrasion
enamel removed by rubbing against a not tooth
abfraction
notch like cervical lesions caused by cyclic loading of teeth
erosion
acid eats away
Age changes in enamel
color- darkens, thins and extrinsic staining nature of surface layer- depends on ions water decreses brittleness increases decreases in permeability overall decrease in caries potential
striae of retzius
longitudinal striped (non demineralized) running from DEJ to enamel surface
may indicate a weekly rhythm in enamel deposition, rings on a tree
straie may dilineate cohorts of ameloblasts
parallel to enamel rods
neonatal line
most accentuated stria of retzius
reflects the physiological trauma occurred during birth
found in all primary teeth and sometimes cusps of first permanent molars
perikymata
visible on surface
surface manefestations of straie of retzius
shallow furrows where stria intersect surface
cross striation
run at right angle to rod direction. typically about 4nm or ones day worth away from each other
can be variations in rod composition (organic/ density)
bands of hunter-schreger
optical phenomenon due to differential light scattering when groups of rods alternate directions
alternating light/ dark bands
cross sections/ and longitudinal running rods
extends 2/3 the difference from DEJ to surface (outer 1/3 more straight)
Gnarled Enamel
seen around DEJ under the cusps/incisal area short distance into enamel
formed from a complex twisting of rods around small diameter ring as teh proceed vertically from dej
enamel tufts
look like small cracks
projecct 1/3 to 1/2 the way into enamel- do not reach surface
contain proteins and are hypocalcified
caused by abrupt changes in enamel rod direction, possibly by overcrowding of ameloblasts
structurally convey on enamel a bit of give to prevent fractures
enamel lamellae
cracks which transverse the whole length of enamel
contain proteins
not all proteins removed or trapped parts of enamel organ
fault lines to resist fracture
enamel spindles
odontoblastic processes that traverse DEJ and penetrate the enamel
very short distance into enamel
often appear at incisal and cuspal tips
may have collagen from dentin in them
disturbances to enamel formation
genetic dysplasia: developmental problems with tooth development/enamel formation
ameloblassts are very sensitive to physiological changes
minor changes can cause structural changes seen histologically
severe changes cause death to ameloblast
tetracycline staining
tetracycline incorporated into minerlaizing tissues
only cosmetic
fluoride induced defects
excess fluoride interferes with amelogenesis
fluorosis or mottles enamel
hypermineralized
can result in pits on teeth but form is normal
