Chemistry of enamel caries Flashcards
describe the concept of supersaturation
- 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
when will ionic materials precipitate
if surrounding solution is above the saturation point
when will ionic materials dissolve
if surrounding solution is below the saturation point
when Is saturation achieved
when the solubility product reaches a certain value
what is the solubility product for binary salt XY
Ksp = [X] + [Y]
what is Ksp
- Product of conc of component ions
- split into separate ions when in contact with fluid
what does fluoride drive
remineralisation due to solubility product between fluorapaite and hydroxyapatite
decreases solubility product, lowers saturation point, above which precipitation occurs
- less soluble than HAP
what is unsaturated with respect to enamel
plaque but super saturated with respect to fluroapatite
what is critical to understanding g enamel HAP dissolution
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
which forms is inorganic phosphate present in
PO43-, HPO42− , H2PO4− and H3PO4 (dependant on ph)
what happens to the concentration of phosphate when the PH is low
lower the ph, the lower conc of phosphate
when the pH is low what happens
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
what is the concept of critical PH
- above PH 5.5 dominant phosphate ion HPO42-
- below pH 5.5 dominant phosphate ion
H2PO4-
what happens below and above PH 5.5.
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
what does protonation of enamel mineral by plaque acid do
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
describe enamel caries demineralisation
- 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
Describe the appearance of an interproximal caries lesion
- 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
what is the appearance of carious lesion showing subsurface demineralisation ?
- beneath early demineralisation, more advanced carious lesions
- porosity increases right down to the level of dentine
- surfaces appearances mean - great deal of damage beneath
describe the layers of caries lesion of enamel imbibition image
- 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
learn table of chemistry of the carious lesion
where is fluoride greater in non caveatted caries or surrounding sound enamel
fluoride in enamel is greater where there is non cavitated caries lesion than there is in surrounding sound enamel
what is the fluoride distribution within the zones of a carious lesion
- 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
Can we boost the effectiveness of fluoride use in patient with high caries risk?
- 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
what is biomimemetic reminerlasition
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
what does CPP stand for
Casein Phosphopeptide: Amorphous Calcium Phosphate
what does CPP do
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
how does CPP complexes bind
- 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
what are SAPs
self assembling peptides
what is the role of SAPs
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”
