Enamel 2

Question 1

amelogenins

Answer 1

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

Question 2

ameloblastin

Answer 2

10% of organic content
expressed through maturation
helps ameloblast adhere to developing enamel
loss of function: ameloblast falls off and no enamel

Question 3

enamelin

Answer 3

least abundant protein (<5%)
only present at leading edge of enamel deposition
possibly plays a role in crystal elongation
loss of function: no enamel

Question 4

enamelysin

Answer 4

MMP
chops up ameloblastin and enamelin
loss of function: thin immature enamel
removes organic for increased minerlaization

Question 5

enamel matric serine proteases

Answer 5

secreted during modulation events of enamel maturation
degrades amelogenins
loss of function: immature enamel

Question 6

Enamel acid etching

Answer 6

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

Question 7

attition

Answer 7

tooth on tooth

Question 8

abrasion

Answer 8

enamel removed by rubbing against a not tooth

Question 9

abfraction

Answer 9

notch like cervical lesions caused by cyclic loading of teeth

Question 10

erosion

Answer 10

acid eats away

Question 11

Age changes in enamel

Answer 11

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

Question 12

striae of retzius

Answer 12

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

Question 13

neonatal line

Answer 13

most accentuated stria of retzius
reflects the physiological trauma occurred during birth
found in all primary teeth and sometimes cusps of first permanent molars

Question 14

perikymata

Answer 14

visible on surface
surface manefestations of straie of retzius
shallow furrows where stria intersect surface

Question 15

cross striation

Answer 15

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)

Question 16

bands of hunter-schreger

Answer 16

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)

Question 17

Gnarled Enamel

Answer 17

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

Question 18

enamel tufts

Answer 18

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

Question 19

enamel lamellae

Answer 19

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

Question 20

enamel spindles

Answer 20

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

Question 21

disturbances to enamel formation

Answer 21

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

Question 22

tetracycline staining

Answer 22

tetracycline incorporated into minerlaizing tissues

only cosmetic

Question 23

fluoride induced defects

Answer 23

excess fluoride interferes with amelogenesis
fluorosis or mottles enamel
hypermineralized
can result in pits on teeth but form is normal