mineralization and fluoride

Question 1

mineralization

Answer 1

1) initiation
2) crystal growth

Question 2

initiation

Answer 2

1) dental lamina
2) mineralization
- amelogenesis and dentinogenesis

Question 3

amelogenesis secretory stage

Answer 3

1) enamel matrix proteins
- amelogenin
- ameloblastin
- enamelin
2) enamel precursors form during the early secretory stage
- initiation at DEJ

Question 4

amelogenin

Answer 4

1) 90% of enamel organic matrix made from it
2) essential for enamel crystal growth and orientation
- rod/interrod
3) calcium phosphate nucleation with amelogenin assemply
- crystalline structure

Question 5

amelogenin organization

Answer 5

1) nanosphere model
- electric charges attract into balls, which align into rod structure
2) nanoribbon directed crystal growth
- head and tail which make dimers => self assembly into ribbons

Question 6

ameloblastin

Answer 6

1) glycoprotein
2) 8-10% of the organic matric
3) role in cell matrix attachment and maintenance of ameloblast differential statee

Question 7

enamelin

Answer 7

1) glycoprotein
2) trace amount

Question 8

transition stage

Answer 8

1) morphology change
- tomes process
- PDL
2) ameloblast gene expression change
- EMP coding genes
- ion transport, proteolysis, pH homeostasis genes

Question 9

maturation stage

Answer 9

1) crystals expand in width and thickness
2) morphology
- ruffle ends and smooth ended

Question 10

proteolytic enzymes

Answer 10

1) MMP20
- dominate in secretory stage
2) KLK4
- dominate mature stage
3) remove proteins

Question 11

endocytosis

Answer 11

1) uptake proteins via endocytosis
2) lysosomes containing the enzymes break it down

Question 12

pH balance and ion transport

Answer 12

1) lots of protons released
2) secretory is neutral
3) maturation is acidic
4) ameloblasts use a number of transport mechanisms to modulate pH

Question 13

acid base transport mechanisms

Answer 13

1) bicarbonate transporter
2) carbonic anhydrases
3) chloride channels
4) H+ pump
5) other ion pumps

Question 14

calcium transporters

Answer 14

1) secretory
- uptake is either passive and/or store Ca2+ entry (SOCE)
- extrusion: PM Ca2+/ATPase or sodium/calcium exchanger (NCX)
2) maturation
- uptake: RA via SOCE
- extrusion: NCKX4, with NCX1/3 and PMCA

Question 15

phosphate ions

Answer 15

1) unclear mechanism
2) Pi from circulation to enamel is fast
3) via transporter or paracellular/intracellular route?

Question 16

water fluoridation

Answer 16

1) reduces caries and tooth decay in USA
2) F- stablizes the hexagonal symmetry and crystal lattice
3) 1 ppm

Question 17

fluoride metabolism

Answer 17

1) 50% will go to the bone in adults, 70-80% in infants
2) rest excreted in kidneys
- half life is 4 hrs

Question 18

fluoride toxicity

Answer 18

1) when over 1 gram
- fatal: acute lethal
- inhibits enolase
- reacts with Ca2+ in ECF, which causes toxicity
2) 10-100 mG
- osteofluorosis, hypermineralization
- bone structure change
3) 1-10 mG
- dental fluorosis
- enamel hypomineralization due to Ca2+ removal from enamel

Question 19

stages of fluorosis

Answer 19

1) very mild
- small chalky <25% of surface
2) mild
- white opacities <50% of surface
3) moderate
- brown staining
4) severe
- extensive discoloration and hypoplasia

Question 20

fluoride incorportation over time

Answer 20

1) increases in the tooth over time
2) replaced hydroxyl group
3) inhibit enolase which is antibacterial effect