Chemistry of enamel caries

Question 1

describe the concept of supersaturation

Answer 1

• ionic materials will only precipitate if surrounding solution is above saturation point
• ionic material will only dissolve is the surrounding solution is below the saturation point
• saturation is achieved when the solubility product reaches a certain value

Question 2

when will ionic materials precipitate

Answer 2

if surrounding solution is above the saturation point

Question 3

when will ionic materials dissolve

Answer 3

if surrounding solution is below the saturation point

Question 4

when Is saturation achieved

Answer 4

when the solubility product reaches a certain value

Question 5

what is the solubility product for binary salt XY

Answer 5

Ksp = [X] + [Y]

Question 6

what is Ksp

Answer 6

• Product of conc of component ions
• split into separate ions when in contact with fluid

Question 7

what does fluoride drive

Answer 7

remineralisation due to solubility product between fluorapaite and hydroxyapatite
decreases solubility product, lowers saturation point, above which precipitation occurs
- less soluble than HAP

Question 8

what is unsaturated with respect to enamel

Answer 8

plaque but super saturated with respect to fluroapatite

Question 9

what is critical to understanding g enamel HAP dissolution

Answer 9

ionisation of phosphate ions
phosphate slats = positively charged ions attached to negatively charged oxygen atoms of phosphate ions- forming ionic compound
- HAP has Ca as positive ion
- crystalline HAP in minerlaizsed tooth will dissolve in plaque if pH is reduced to less than 5.5

Question 10

which forms is inorganic phosphate present in

Answer 10

PO43-, HPO42− , H2PO4− and H3PO4 (dependant on ph)

Question 11

what happens to the concentration of phosphate when the PH is low

Answer 11

lower the ph, the lower conc of phosphate

Question 12

when the pH is low what happens

Answer 12

more H+ ions added to plaque fluid or saliva
phosphate ions increasingly less able to maintain bond to calcium ions within HAP mineral in enamel

Question 13

what is the concept of critical PH

Answer 13

• above PH 5.5 dominant phosphate ion HPO42-
• below pH 5.5 dominant phosphate ion
  H2PO4-

Question 14

what happens below and above PH 5.5.

Answer 14

above ph - ionic binding to lattice especially to adjacent calcium ions is weakened and ions can move into solution ,
below critical pH - enamel starts to dissolve

Question 15

what does protonation of enamel mineral by plaque acid do

Answer 15

H+ is added to bacterial biofilm metabolism of fermentable carbohydrates
H+ ions bind to PO4 ions
- reducing ionic binding of phosphate ions to calcium ions in HaP crystal lattice as PH drops

Question 16

describe enamel caries demineralisation

Answer 16

• in presence of fluoride in dental biofilm
• sugars are converted to acids in biofilm
  PH below 5.5 undersaturation with respect to HA is reached in biofilm fluid= mineral dissolution
  PH higher than 4.5 and fluoride present- biofilm is supersaturated with respect to fluorapatite
  -reprecipitaiton of minerals in enamel
• net mineralisation is reduced
  after exposure of sugar ceases, acids in biofilm are cleaned by saliva and converted to salts
• PH increases to 5.5 or higher
• biofilm fluid is supersaturated with respect to HAP and fluorapatite
• calcium and phosphate loss by enamele can be efficiently recovered if fluoride is still present in the biofilm
• fluoride ion appears to be less susceptible to acidic environment; less soluble and shifting the equilibrium towards precipitation

Question 17

Describe the appearance of an interproximal caries lesion

Answer 17

• clinically early caries -seen as white spot on tooth surface
• due to dissolution of mineral by acid produced by bacteria in the plaque biofilm
• acid produced tiny pores which dry out producing white spot due to light scatter

Question 17

what is the appearance of carious lesion showing subsurface demineralisation ?

Answer 17

• beneath early demineralisation, more advanced carious lesions
• porosity increases right down to the level of dentine
• surfaces appearances mean - great deal of damage beneath

Question 18

describe the layers of caries lesion of enamel imbibition image

Answer 18

• deepest part of lesion; translucent zone adjacent to sound enamel
  ( first change which indicates large holes)
• one more superficial to this , dark or positively birefringent zone - increase in porosity but presence of small holes inaccessible to imbibing fluid
• body of lesion shows more posterity with large pores
• dark zone = puzzling and looks if re precipitation of dissolved mineral has occurred
• finding raised possibility caries lesions could reminerlasied
• temporary re precipitation may provide means of encouraging natural tooth repair

Question 19

learn table of chemistry of the carious lesion

Answer 19

Question 20

where is fluoride greater in non caveatted caries or surrounding sound enamel

Answer 20

fluoride in enamel is greater where there is non cavitated caries lesion than there is in surrounding sound enamel

Question 21

what is the fluoride distribution within the zones of a carious lesion

Answer 21

• amount of fluoride in sound enamel around caries lesion and at surface with that form 4 zones of non cavitated lesions
• fluoride content higher in sound surface enamel than sound subsurface enamel
• higher fluoride in surface enamel. overlying body of lesion than in sound surface enamel

Question 22

Can we boost the effectiveness of fluoride use in patient with high caries risk?

Answer 22

• gian nét remineralisation of enamel HAP
• Action of fluoride which may be limited by the availability of intrinsic salivary Ca 2+ AND PO43- has the potential to be facilitate by supplementation of bioavailable calcium and phosphate into oral cavity
• even more critical , is the length of time fluoride persists near the enamel surface. this may also be helped by the use of a source of calcium mourned the time of fluoride exposure , which aim to increase the formation of CaF2 and calcium fluoride like mineral and in doing so increase fluoride persistence near the enamel surface
• additionally, patients are instructed on a appropriate formulation,timing and frequency of brushing with fluoride toothpaste and advised not the rinse following use of flouride toothpaste

Question 23

what is biomimemetic reminerlasition

Answer 23

includes techniques which attempt to mimic nature with respect to remineralisation, Products include those delivering proteins to stabilise calcium and phosphate ions and others which deliver peptides into early lesions to control the mineralisation process

Question 24

what does CPP stand for

Answer 24

Casein Phosphopeptide: Amorphous Calcium Phosphate

Question 25

what does CPP do

Answer 25

has potential to promote remineralisation by stabilising high concentrations of calcium and phosphate ions at the tooth surface as it binds these ions to form nano clusters

Question 26

how does CPP complexes bind

Answer 26

• the complexes bind into the biofilm and buffer Ca2+ and PO43- activities in the biofilm fluid at the tooth surface ,establishing an envrioenermtn supersaturated with respect to calcium and phosphate , including tooth mineral, encouraging precipitation of claim phosphate ions onto the exposed tooth surface

Clinical trials limited - application of CPP - ACP pastes can be attempted if fluoride applications alone show no success in select cases

Question 27

what are SAPs

Answer 27

self assembling peptides

Question 28

what is the role of SAPs

Answer 28

SAPS are bioactive peptides synthesised from natural AA which have shown promising results
- increased net mineral Gian via inhibition od demineralsirion and promotion of remineralisation
- nucleate hydroxyapatite de novo
- mimic enamel matrix proteins which control inertial mineral deposition ‘nucleation’ and subsequent crystal growth
- infiltrate early ‘white spot’ caries lesions and following self- assembly within the lesion, generate subsurface bioactive scaffold capable of inducing mineral deposition
- are candidate materials for ‘ filling without drilling”