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z OE > demineralisation and remineralisation > Flashcards

demineralisation and remineralisation Flashcards

1
Q

3 things requried for caries and demineralisation?

A

bacteria

sugar

weak saliva defences

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2
Q

appearance of initial caries lesion

A
  • white spot
    • indication of change of porosity of enamel surface
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3
Q

initial caires lesion under polarised light micrograph

A
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4
Q

hydroxyapatite chemical formula

A

Ca10(PO4)6(OH)2

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5
Q

effect of acidic pH on hydroxyapatite

A
  • HAP converted into more stable salt
    • has lower [Ca]/[PO4] molar ratio

Ca10(PO4)6(OH)2 + 8H+ -> 6 CaHPO4 +2H2O + 4Ca2+

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6
Q

effect of pH <4 on dicalcium phosphate

A

dicalcium phosphate is most stable at this pH and it dissociated into its constituent ions

CaHPO4 + H+ -> Ca2+ + H2PO4-

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7
Q

formulas for hydroxyapatite solubility produce equilibrium constant Ksp

A
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8
Q

if ionic activity product is higher than solubility product equilibrium constant (Ksp)

A
  • solution is super saturated
  • salt precipitation will occur
  • remineralisation
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9
Q

if ionic activity product is lower than solubility product equilibrium constant (Ksp)

A
  • solution is not saturated
  • dissolution of solid will occur
  • demineralisation
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10
Q

what is happening at stages 1 2 3 & 4

A
  1. Lowering the pH from ~7 to 4.5 at the enamel surface by fatty acids from bacteria
  2. Dissolution of calcium and phosphate
  3. saliva flows over the affected area resulting in rise of pH
  4. If fluoride is present, together with saliva the softened surface is repaired, at least partially.
  • If fluoride is not present then step 4 stops at the enamel line.
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11
Q

As plaque pH decreases,

effect on calcium phosphate solubility

A

calcium phosphate solubility increases

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12
Q

rising pH effect on dicalcium phosphate

A

converts dicalcium phosphate into salt with high [ca]/[PO4] molar ratio

eventually becomes hydroxyapatite

remineralisation

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13
Q

what is the pellicle layer

A
  • layer on top of enamel
  • predominantly saliva components
  • provides protective layer
    • hydrophobic potential
    • semipermeable barrier
    • restricted movement of mineral ions through enamel surface
  • acellular organic layer
    • facilitates precipitation of mineral at surface
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14
Q

how do calcium salts pass between saliva and enamel through the pellicle ?

A
  • they exist as ions in saliva and enamel layer
  • must become electroneutral form to pass through pellicle layer and dissociate into ions once passing through
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15
Q

what factors does progress of demineralisation depend on

A
  • the rate of acid produced externally
  • the production of net-neutral species which diffuse more readily across the pellicle layer than charged species
  • the rate of inward diffusion of the unionised forms of acids through the pellicle layer and the water filled inter-crystalline organic phase of enamel.
  • the rate of apatite dissolution
  • the outward dissolution of calcium phosphate in the form of uncharged aqueous complexes
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16
Q

what changes occur within the zone of caries lesions

A
  • Pore structure
  • Relative ion concentration
  • Possible crystal changes
17
Q

what factors influence enamel dissolution

A
  • Biogenic apatites display some variety in their ion stoichiometry depending on tissue, developmental stage, individual etc.
  • Incorporation of impurities such as magnesium, sodium and carbonate tend to increase solubility
    • Calcium can be replaced by magnesium, sodium, potassium, lead, strontium, or barium
    • Carbonate can replace either hydroxyl or phosphate
  • Replacement of the hydroxyl group with fluoride leads to the formation of fluorapatite and fluoridated apatites, which reduces solubility
18
Q

factors influencing tooth surface loss

biological

chemical

health

behavioural

A
19
Q

strategies for prevention of demineralisation

A
  • good dental hygiene and frequent rinsing
  • toothpastes with fluoride
    • interferes with enolase in glycolysis and inhibitors adhesion to teeth
      • inhibits glucosyltransferase used by bacteria to produce dextran
    • antibacterial agents
    • zinc
  • fissure sealants
    • prevents diffusion of neutral salts in and out of enamel surface
20
Q

draw summary flowchart of demineralisation and remineralisation

A

z OE (35 decks)

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