Enamel

Front 1

does enamel contain collagen?

Back 1

no

Front 2

describe the enamel blood vessels and innvervation

Back 2

it has none

Front 3

what secretes/forms enamel

Back 3

ameloblasts

Front 4

where is enamel thickest?

Back 4

in areas exposed to attrition and risk of fracture

Front 5

Why do teeth turn yellow as we age?

Back 5

enamel translucency increases with age allowing the darker yellow colour of dentine to be transmitted

Front 6

what is contained in an enamel prism?

Back 6

several million HA crystaliites

Front 7

where do enamel prisms run from?

Back 7

amelodentinal junction to tooth surface

Front 8

why do enamel prism arrangements have a keyhole appearance?

Back 8

the prism are arranged in staggered rows such that the tail of the prism lies between two heads in the row below

Front 9

what causes sinusoidal lines in enamel?

Back 9

prisms path bending

Front 10

what creates hunter-schreger bands?

Back 10

periodic changes in prism direction that make the enamel more resistant to fracture

Front 11

Where is gnarled enamel found?

Back 11

near cusps and incisal regions

Front 12

what is the arrangement of prisms in gnarled enamel?

Back 12

spirals

Front 13

where is prismless enamel found?

Back 13

first few microns of formed enamel adjacent to dentine and the outer 20-70 micrometres of enamel

Front 14

what are the features of prismless enamel?

Back 14

the absence of prism boundaries means that there is less organic material present and the highest degree of mineralisation occurs

Front 15

where and when do cross striations form in enamel?

Back 15

formed every 24 hours, they cross prisms at right angles

Front 16

what are the straie of retzius?

Back 16

prominent dark lines running obliguely across enamel prisms to the surface (in longitudinal sections)

Front 17

what are perikymata ridges formed by?

Back 17

the straie of retzuis at tooth surface creat a series of fine grooves running around the tooth crown. Perikymata grooves are separated from each other by perikymata ridges

Front 18

what sort of patten is the amelodentinal junction?

Back 18

scalloped

Front 19

what are enamel spindles?

Back 19

seen in longitudinal sections as narrow round tubules extending up enamel, not aligned with prisms. Thought to be odontoblast processes

Front 20

what are enamel tufts?

Back 20

resemble tufts of grass, tubules extending from amelodentinal junction travelling with prisms

Front 21

what is contained in enamel tufts?

Back 21

tuftelin - a non-amelogenin protein of enamel

Front 22

In which section are lamellae distinguishable from enamel cracks?

Back 22

decalcified sections as cracks disappear

Front 23

what are enamel lamellae?

Back 23

sheet-like structural fault across entire thickness of enamel in transverse sections. Hypomineralised and filled with debris.

Front 24

what happens to enamel as we age?

Back 24

increased wear and tear, darkening colour, equilibrates with oral environment

Front 25

when does amelogenesis occur?

Back 25

during bell stage of tooth development, process begins at amelodentinal junction

Front 26

what does crystal formation of enamel begin with?

Back 26

an organic matrix secreted by ameloblasts moving away from Amelodentinal junction

Front 27

what are the 5 stages of the life cycle of the ameloblast?

Back 27

presecretory, secretory, transition, maturation, post-maturation

Front 28

what occurs when ameloblasts are in the pre-secretory phase?

Back 28

resorption of basal lamina

Front 29

what occurs when ameloblasts are in the secretory phase?

Back 29

Secrete aprimsmatic Enamel. Cells become polarised. Rings of webs form via tight junctions and desmosomes in ameloblast layers. Extensions of cytoplasm: Tomes process develops. Enamel laid down.

Front 30

what forms prisms?

Back 30

one ameloblast contributes to the formation of one prism core.

Front 31

What are tomes processes responsible for in enamel formation?

Back 31

they secrete the matrix and are therefore responsible for the prism structure of enamel

Front 32

What are 90% of enamel matrix proteins?

Back 32

amelogenins

Front 33

what role do the enamel matrix proteins play?

Back 33

regulate the formation of long enamel crystals and prism pattern/structure.

Front 34

What happens to amelogenins in maturation phase of enamel?

Back 34

virtually all removed by controlled extracellular degradation

Front 35

What role do ameloblasts play in maturation phase?

Back 35

they move calcium, phosphate and carbonate ions into the immature matrix and move water/degraded proteins out of it

Front 36

when are mature ameloblasts ruffled ended?

Back 36

secretory phase: calcium phosphate and carbonate ions

Front 37

when are mature ameloblasts smooth ended?

Back 37

resorptive phase: water and degraded proteins

Front 38

what is formed when reduced post-maturation phase ameloblasts merge with the enamel organ?

Back 38

reduced enamel epithelium

Front 39

what forms reduced enamel epithelium?

Back 39

merging of post-maturation ameloblasts and enamel organ.

Front 40

What is amelogenesis imperfecta?

Back 40

hereditary disorders affecting only enamel, via malfuntion of enamel proteins. Teeth are abnormal in colour, have a high risk of dental caries and are hypersensitive to temperature changes