W11 Flashcards
what are the key histological features of enamel
hardest substance in the body
highly mineralised
acellular
96% inorganic (hydroxyapatite - calcium and phosphate rod formation)
3% organic - proteins cover crystals in delicate lattice, influencing chemical behaviour of enamel
1% water in space between crystals
what are enamel prisms
tightly packed separated by intercrystalline spaces or pores (microporons) - a net flow of fluid out of enamel prisms
are enamel hydroxyapatite crystals pure
no as they contain other ions (fluoride, carbohydrate and sodium)
carbohydrate makes them more susceptible to dissolving
what is the histological features of dentin
70% mineral and acellular (hydroxyapatite)
30% organic water cologen and mucopolysacharide)
describe the demin/remin process
Demin- in prensence of acid phosphate ions will be combined with hydrogen ions producing hydrogen phosphate= unable for crystal formation, PH supersaturated solution is lowered to just saturated due to loss of minerals= critical ph appears (5.5) - if we go beyond that point- inbalance and loss of ions into solution and binding with hydrogen and being lost
Remin - reversal - fluoride brings up ph - fluoropatite crystals
when does a cavitation form
first intial white spot lesion - ICDAS
if the demineralisation and remin imbalance continue - the surface of the incipient lesion collapses, so the structure of the enamel becomes extremely weak leading to cavitation icdas 3
what does ICDAS stand for
international caries detection and assessment system
why can dental caries be classified as a phasic disease process
there is supersaturation, saturation and undersaturation
what are the chemical reactions during the caries process
when exposed to sugars, acids and carbohydtrates the ph goes down to 5.5 and Hydroxyapatite is reactive with hydrogen ions
if it stays at this level - phosphate ions bind to hydrogen ions - hydrogen phosphate = DEMINERALISATION
would a new tooth or old tooth have higher concentration of flouro-hydroxyapatite?
one that has been in the mouth for some time
it requires the demineralisation and remineralisation process to allow flouride to be incorporated into the crystal (need cariogenic challenges or acidic challenges for flouride to be incorporated)
What is the critical PH for hydroxyapatite
5.5
What is the critical PH for fluoro-hydroxyapatite
4.5
What is the critical PH for Dentin
6.3
What is the critical PH for Cementum
6.7
what are the key zones of incipient enamel lesions
surface zone
Body of lesion
Dark Zone
Translucent zone
which zone has the largest pores
Body of lesion
what are the key zones of a cavitated dentinal lesion
zone of destruction
zone of penetration
demineralised dentine
what zones of a cavitated dentinal lesion get kept during the cavity prep stage
demineralised dentine - keep and remineralise (firm affected dentine)
what are the soft dentin zones of a cavitated dentinal lesion and what do you do with them
zone of destruction
zone of penetration
Destroy/get rid of them
under what circumstances can caries be arrested and remineralised
must have favourable environment in the mouth
improve oral hygeine
why is the pulp chamber in a molar in a 40year old likely to be smaller than one in a 10year old
pulp chambers decrease in size as you age
tubular serosis and the formation of new dentin are the pulps responses to destructive processes - it works to slow down the advancemennt of the lesion
dead tracts occur when odontoblasts die without tubular sclerosis - new odontoblasts can still be formed
CONTINUED DEPOSITS OF SECONDARY DENTIN INTO THE PULP CHAMBER
how does root caries occur
cementum exposed due to recession or perio treatment - higher critical ph of 6.7
does not have that layer of enamel that is highly mineralised and less soluble
will see quite early and easily - easy to arrest and remineralise
what is recurrent caries
occurs at margins of restorations
what is residual caries
infected or demineralised dentin is left in cavities during cavity prep
how can radiographs tell the difference between recurrent and residual caries
residual = radiolucent area under recently placed restoration
what are the characteristics of soft dentin
INFECTED DENTIN
- high levels of bacteria
- complete demineralisation
- complete or partial collapse of the tubule structure
- loss of dentin sensitivity
what are the characteristics of firm dentin
AFFECTED DENTIN
- there is enough mineral content to maintain tubular structure
- there are minimal levels of bacteria
- as long as there is 10% of the organic level of mineralisation, remin can occur
What are the 7 steps in dentine destruction
Sclerotic dentin (white streaks)
Zone of demineralisation (gets bigger)
Odontoblasts lay down secondary dentine
Pointed cavitation (allows bacteria to go through enamel)
Cavitation gets bigger
As biofilm comes into contact with dentine one of destruction forms
Masses of bacteria and destruction of dentin (all need to be removed)
