Enamel and dentine basic histo

Question 1

Most mineralised tissue in the body

Answer 1

enamel

Question 2

mineral percentage of enamel and dentin

Answer 2

96 and 70%

Question 3

where does enamel come from

Answer 3

produced by ameloblasts

Question 4

why doesnt enamel have no capacity for repair?

Answer 4

ameloblasts are lost during development

Question 5

why is enamel difficult to study?

Answer 5

tissue is so hard

Question 6

what feature does ground section lack compared to a decalcified section of the tooth?

Answer 6

no pulp in ground sections

Question 7

what are the enamel crystals called and where do they reside?

Answer 7

hydroxyapatite, arranged into rods and interrods

Question 8

enamel rods are —– to DEJ.

Answer 8

perpendicular

Question 9

how thick are the enamel rods?

Answer 9

4 microns

Question 10

what is interrod?

Answer 10

enamel material between rods

Question 11

what direction are the crystals in the rod?

Answer 11

obliquely

Question 12

what is rod sheath and its feature?

Answer 12

where rod and interrod meet and its highly organic material

Question 13

what does each ameloblast produce specifically?

Answer 13

one rod and adjacent interrod

Question 14

what is tomes process?

Answer 14

a cytoplasmic projection is a conical structure that points towards the forming enamel matrix; produces rod enamel and interrod enamel.

Question 15

ameloblasts secrete enamel matrix through the ….

Answer 15

tomes process

Question 16

amelogenesis begins at — of tooth development and intiated on —- sides of tooth through a — process.

Answer 16

bell stage, reciprocal induction

Question 17

what causes the formation of incremental lines?

Answer 17

rhythmic production of enamel

Question 18

what causes dark and light bands in the enamel

Answer 18

diurnal rhythm of ameloblats which varies amount of matrix and mineral

Question 19

in ground sections of the enamel the rods appear —- and the interrod appear —.

Answer 19

rods light , interrod dark.

Question 20

why can we distinguish rods and interrods in ground sections?

Answer 20

crystallites of calcium and hydroxyapatite are oriented parallel in the rods but obliquely in the interrod- so light can pass the rods more than the interrod hence light rod dark interrod.

Question 21

how are enamel spindles formed?

Answer 21

when odontoblast processes extend across DEJ

Question 22

lamellae extend from — towards—.

Answer 22

enamel surface towards DEJ.

Question 23

tufts extend from —- to —

Answer 23

DEJ towards enamel

Question 24

what are hunter schreger bands?

Answer 24

fully mineralised rods following a twisted path through enamel layer that causes these visible bundles in ground sections.

Question 25

what are gnarled enamel?

Answer 25

in regions of high curvature rods follow curved path and twists.

Question 26

which one forms first enamel or dentin?

Answer 26

enamel

Question 27

2nd hardest tissue in the body?

Answer 27

dentin

Question 28

what produces dentin?

Answer 28

odontoblasts

Question 29

is dentin fixable/able to regrow?

Answer 29

yes, odontoblasts stick around unlike ameloblasts

Question 30

odontoblasts reside at ----

Answer 30

periphery of the pulp

Question 31

what is dentin before mineralisation?

Answer 31

pre dentin

Question 32

where are odontoblasts organised?

Answer 32

they remain the pulp, however their processes extend into dentinal tubules which extends towards DEJ.