enamel tissue Flashcards Preview

Oral Histo > enamel tissue > Flashcards

Flashcards in enamel tissue Deck (35):
1

from what germ layer is enamel derived?

ectoderm...formed by ameloblasts (which come from the inner epithelial layer of enamel organ)

2

what 2 stages is enamel in

1. immature 2. mature....never in an unmineralized form

3

when does the ameloblast complete its enamel formative cycle

once the thickness of enamel is reached at a particular site

4

does enamel appear before or after dentin

after

5

enamel does not have

b.v, cells, nerves, lymphatic vessels (acellular, avascular, aneural, alymphatic)

6

microporosity defined

pathways for diffusion of small molecules such as water. electrochemical effects on pore walls lead to carious lesions

7

remineralization

when mineral is returned to the molecular structure of enamel by way of the saliva. when demineralization exceeds remineralization, cavitation occurs.

8

chemical components of enamel

1. inorganic substance (96%) 2. organic substance (1%) 3. water (3%)

9

inorganic substance is made of

calcium hydroxyapetite crystals...these crystals are larger and have more impurities (than other mineralized tissues)

10

organic substance is made of

proteins. amelogenin is the main protein, but other non-amelogenin proteins exist. NO COLLAGEN.

11

what is a hydration shell

water forms a hydration shell around each crystal. this water distribution is the route of fluoride, calcium, and phosphorous ions for remineralization (also whitening substances, and acidophilic microorganisms)

12

how does enamel change with age

wears slowly, darkens in color, composition of surface changes, fluoride increases at surface, reduced porosity, reduced susceptibility to caries

13

DEJ configuration at the coronal area

wavy/scalloped to adapt to occlusal forces

14

DEJ configuration at the cervical area

smooth at non-loading bearing areas

15

what is the most common CEJ configuration

cementum overlapping enamel...but this relationship varies around a tooth and from tooth to tooth

16

what are lines of retzius

growth lines of enamel

17

what are perikymata

transverse ridges on the exposed surface of enamel. created by lines of retzius

18

what are the structural components of enamel

1. enamel rods
2. enamel sheath
3. interrod substance

19

what is an enamel rod composed of

several million crystallites are packed in each rod. crystals are most dense in the center/core of the rod. the crystals run parallel to the long axis of the rod. each rod is formed by one ameloblast

20

what is the enamel sheath composed of

outer surface of the rod. crystals are less dense than the rod. crystals run in different directions. there is a higher % of organic substance here (highest % of amelin...protein)

21

what is interrod substance composed of

b/w the sheaths of the rods. crystals are more dense than sheath. crystals run at different directions than sheath crystals. 2 or more ameloblasts secrete the interrod substance.

22

dark lines that separated segments of enamel rods

interrod striations. the rod is segmented because it's secreted in a rhythmic manner (the rest period of a ameloblast is marked by an interrod striation)

23

3 types of hypomineralized enamel structures

1. enamel lamella
2. enamel tuft
3. enamel spindle

24

enamel lamella

extend for varying depths from the surface of enamel. consist of longitudinally oriented defects filled with enamel protein or organic debris

25

what is the clinical significance of enamel lamella

access by acidophilic microorganisms (caries) and stain substance (esthetics)

26

enamel tuft

tufts project from DEJ into the enamel and contain greater concentration of enamel protein than the rest of enamel (tuftelin)

27

clinical significance of enamel tuft

contributes to the spread of caries at the DEJ

28

enamel spindle

extend from the dentin cross the DEJ into the enamel

29

clinical significance of enamel spindle

contributes to spread of caries along the DEJ

30

formation of enamel spindles

cell processes of odontoblasts extend b/w ameloblasts and when enamel formation begins the processes become embedded within the newly secreted enamel

31

hunter schreager bands

alternating dark and light bands or varying width. originate at the DEJ border and pass outward ending at some distance from the outer enamel surface. they are caused by the different direction of enamel rods in adjacent layers. (this is a functional adaptation to minimize the risk of cleavage in the axial direction during masticatory functions)

32

where dues differentiation of the inner epithelial cells and the peripheral cells of the dental papilla begin

in the coronal most sit of the future DEJ

33

what is the name for ectopic enamel formation

enamel pearls

34

tetracycline stain is caused by

antibiotics

35

mulberry molars are caused by

congenital syphilis