Enamel Tissue

Question 1

of the 4 connective tissues is enamel the only one that is not a connective tissue?

Answer 1

yes (all are ectoderm derived though)

Question 2

what other (other than epithelial derived) difference is there is enamel over the 4 other tissues?

Answer 2

does NOT have an unmineralized (preenamel) stage only a partially (immautre) and full mineralized stage (mature)

Question 3

what place is enamel in for mineralized tissues appearing?

Answer 3

2nd

Question 4

what is the thickest cusp of enamel and how big is it?

Answer 4

M/B cusp of the Maxillary 1st molar is 2.5 mm

Question 5

is the enamel subject to malformation?

Answer 5

yes, genetic and external factors

Question 6

what does enamel not have?

Answer 6

enclosed cells (acellular), nerves, blood vessels and lymph vessels

Question 7

what happens to enamel when its not wet (in saliva)?

Answer 7

dissolves (also if you put it in acid it will dissolve)

Question 8

What is enamel?

Answer 8

composite biological tissue with apatite crystals oriented in a 3D pattern

Question 9

what are some physical properties of enamel?

Answer 9

brittle (w/o dentin), translucent, hard as mild steel (strength of 5 on Mohs scale), hue dependent on location and conditions, subject to attrition, abrasion and erosion, microporosity and remineralization

Question 10

attrition

Answer 10

normal mastication

Question 11

microporosity

Answer 11

pathways for diffusion of small molecules like water

leads to carious lesions electorchemically

Question 12

what are the chemical properties of enamel?

Answer 12

1. inorganic (96%) hydroxyapitate crystals (mainly calcium) crystals are larger and contain more impurities than other tissues (Fl, carbonate)
2. organic (1%)
3. water (3%)

Question 13

where do caries form in enamel?

Answer 13

in the pores

Question 14

what is in the organic portion of enamel?

Answer 14

proteins like AMELOGENIN, enamelin, amelin and tuftelin

• *90% of proteins in enamel is amelogenin which is a seed protein for normal mineralization
• arranged in lace like patterns but closely associated to surface of the crystals
• ***ONLY mineralized tissue NOT to have COLLAGEN fibers

Question 15

if you dont have amelogenin, what happens?

Answer 15

no mineralized

Question 16

what does the eater do for enamel?

Answer 16

(more than organic substance) distributed through micropores
**forms a hydration shell around crystals and provides pathways for Fl, Ca, and Ph ions and remineralization :) and acidophilic microorganisms with age change :(

Question 17

age changes in enamel

Answer 17

attrition, darker color, surface composition (more Fl??), reduced porosity, less susceptibility to caries, systemic age changes??

Question 18

configuration at DEJ

Answer 18

at crown scalloped b/c occlusal forces and smooth cervically because not load bearing

Question 19

configuration at CEJ

Answer 19

1. most common: cementum overlaps enamel
2. next common: cementum meets enamel
3. least common: cementum and enamel don’t meet

Question 20

if dentin is exposed (because C and E not touching)

Answer 20

pain

Question 21

what type of cells are ameloblasts?

Answer 21

tall columnar epithelium

Question 22

what are the growth lines of enamel called?

Answer 22

lines/strae of Retzius

Question 23

what are perikymata?

Answer 23

transverse ridges that are formed in between the line of Retzius grooves
** look like waves

Question 24

what are the structural components of enamel?

Answer 24

enamel rods, sheaths and iterrods substance

**structure of enamel is due to the density and direction of the apatite crystals

Question 25

enamel rod

Answer 25

• structural unit of enamel
• diamter of 5-6 um and a length of up to 2.5 mm
• several million crystals are in each rod and run parallel to the long axis of the rod (most dense at center of rod)
• each rod is formed by one ameloblast

Question 26

enamel sheath

Answer 26

• outer surface of the rod
• less dense crystals, run in different direction than the core, and have higher organic percentage
• highest percentage of organic material is amelin

Question 27

interrod substance

Answer 27

between the sheaths of rods (more dense than sheath, diff direction than sheath)
**two or more AB secrete interrod substance

Question 28

interrod striation

Answer 28

marks the rest period of the ameloblast’s rythmic pattern of secretion of rods. dark and light appearance.

Question 29

what direction do the rods form?

Answer 29

right angle to dentin

Question 30

enamel lamella

Answer 30

hypomineralized enamel structure

• extend from varying depths from the enamel surface (can even pass into pulp?!)
• linear, longitudinal defects filled with enamel protein or organic debris
  (ex. getting hit and microbes or stain getting into)

Question 31

enamel tuft

Answer 31

from the DEJ into the enamel for short distance and contain a great amount of the protein (tuftelin) and look like a tuft
**spreads caries at the DEJ

Question 32

Enamel spindle

Answer 32

starts in dentin, across DEJ into enamel for short distance
**spreads caries along the DEJ
OD cell bodies in the pulp have processes that extend between ameloblasts and get stuck once enamel secreted

Question 33

Hunter-Schreagar bands

Answer 33

Alternating dark and light bands (of varying width) due to the enamel rod direction changing in adjacent layers starting from DEJ and extending outward
**thought to be and adaption to minimizing cleavage in the axial direction under masticatory forces

Question 34

ameloblasts move where and odotoblasts move where when secreting respective substances?

Answer 34

AB outwards and OB inwards

Question 35

ectopic enamel (enamel pearl)

Answer 35

if formed where cementum forms then an open space in the perio ligament