Enamel II

Question 1

how are the enamel rods oriented in relation to the DEJ ?

Answer 1

perpendicular to it

-vertical near the cusp tip and more horizontally near the cervical area , inclined towards root at cementoenamel junction

Question 2

what is the course each aneml rod follows like?

Answer 2

moving to the left and right it is not straight except in cervical enamel

Question 3

what is gnarled enamel ?

Answer 3

twisted enamel found near the cusp tip

Question 4

the cyclic activity of ameloblasts secreting enamel is manifested visually as:

Answer 4

incremental lines of retzius (long incremental lines) and cross striations (short incremental lines) formed due to daily activity. these lines appear as dark lines that are pigmented due to the presence of increased protein in that area as the ameloblasts rest

Question 5

human enamel is produced at a rate of ___ per day

Answer 5

4

Question 6

9

Answer 6

9

Question 7

describe the phenomenon of hunter schreger bands .

Answer 7

it is an optical phenomenon that appears as dark and light alternating bands seen on incident illumination

this happens due to some light rays passing through and some light rays being reflected by the //\/\/\/\/\ shape of enamel rods

Question 8

how do you differentiate between enamel lamellae and cracks ? what are some unique features that indicate an enamel lamellae?

Answer 8

enamel lamellae are hypo mineralized areas of enamel caused by defective ameloblasts. Since the ameloblast is suddenly defective while secreting enamel , it is expected that it stays that way all the way through amelogenesis so the line of hypo-mineralized enamel always continues to the outer surface of the tooth.

enamel lamellae still contain inorganic material unlike cracks which are just empty

in a decalcified section , enamel cracks will disappear while the enamel lamellae can still be observed

Question 9

enamel cracks are filled with :

Answer 9

salivary proteins

Question 10

long incremental lines are known as:

Answer 10

incremental lines of retzius

Question 11

short incremental lines are known as:

Answer 11

cross striations

Question 12

enamel tufts are best seen in ____ sections

Answer 12

transverse

Question 13

what are enamel tufts ?

Answer 13

hypomineralized areas of enamel rich in enamel protein called tufts

-they are found near the DEJ and are formed during the inital stages of matrix secretion

-they project into the DEJ for a short distance and resemble grass

Question 14

enamel tufts are found near ____

Answer 14

DEJ

Question 15

What are enamel spindles ?

Answer 15

extension of odontoblastic process into the ameloblast layer when enamel formation begins –> trapped—> forms spindles

Question 16

enamel spindles are found most frequently at___

Answer 16

cusp tip

Question 17

describe the profile of the DEJ

Answer 17

SCALLOPED (in cross section )
-this type of profile increases adherance between dentin and enamel

-it also prevents shearing of enamel during function

• it is most prominent in the coronal dentin where occlusal stress is greatest

Question 18

scalloped profile of DEJ is most pronounced where?

Answer 18

in coronal dentine

Question 19

what is the perikymata ?

Answer 19

shallow grooves manifesting on surface of enamel as result of incemental lines ,

they are transverse wavelike grooves and furrows
each other and to the cementoenamel junction

Question 20

which layers of enamel are prisim-less?

Answer 20

the first layer secreted over the DEJ as well as the final layer of enamel in unerupted teeth which is usually lost due to abrasion , attrition and erosion once the tooth erupts—-> this prisimless structure must be removed before application of orthodontic appliances