define caries
progressive destruction of the tooth structure initiated by microbial action at the tooth surface (crown or exposed root)
give the 4 factors that are required to bring about caries
- susceptible tooth
- plaque bacteria
- substrate
- time
what is the structure of enamel?
Prism core in centre and prism sheath in the peripheries
what can be said about the prism core?
tightly packed hydroxyapatite with little inter-crystaline spaces
what can be said about the prism sheath?
- less well packed hydroxyapatite = pores
- pores contain water and organic material
- allows easier diffusion of acids
- WHERE DEMINERALISATION STARTS
what does enamel caries look like?
white spot lesion that can be seen on clean dry tooth - matt appearance
how can enamel be viewed under a microscope?
by using quinoline
why is quinoline used to aid view of enamel?
they have the same refractive index so most accurate view
what are the different zones of enamel caries? 4 zones
- surface zone
- body of the lesion (i
- dark zone ( in 90-95% of lesions)
- translucent zone (in 50% of cases)
how much mineral loss occurs at the translucent zone?
1-2%
how does the translucent zone appear under quinoline?
- some large pores (due to prism sheath loss)
- appears more translucent
- quinoline fills peripheries
how does the dark zone appear under quinoline?
- dark brown
- porosities of 5-10%
describe the types of porosities seen in the dark zone
large pores small pores ( not penetrated by quinoline - appear dark)
demineralisation and remineralisation occurring here
what % porosity is there in the body of the lesion?
25-50%
how does the body of the lesion (largest part and centre of lesion) appear under quinoline?
- enamel relatively translucent
- striae of Rezius more obvious (incremental growth lines)
- corresponds to the radiographic appearance
facts about the surface zone..
- relatively intact
- 30 micrometres thick
- highly mineralised due to high Fluoride content at surface
- porosity of 1-2%
- protected
- forms and reforms during caries process (redeposition of mineral dissolved from deeper layers
how can caries become arrested and what does it look like clinically and microscopically?
due to
- dietary changes
- plaque control + fluoride
clinically - brown exogenous stain
microscopically - a wide, well-developed dark zone
what occurs as enamel caries advances at adj?
- sclerotic dentine formation mid way into dentine
- reactionary tertiary dentine formation next to pulp
what does an intact surface mean for the caries?
no bacterial invasion
what occurs when there is an intact surface but the advancing front has gone into dentine?
- caries spreads more rapidly and laterally
- more reactionary & sclerotic dentine laid down
after cavitation you get ….?….. and this leads to which 3 zones of established dentine caries?
bacterial invasion leads to
- zone of destruction
- zone of bacterial penetration
- advancing front into dentine
what is the zone of destruction?
- where you have mixed bacterial population - 2ry infectors
- proteolytic enzymes
- destroys organic matrix
what occurs as the zone of bacterial penetration?
- bacteria into tubules
- lateral spread via branched tubules
- lactobacilli
what is happening at the advancing front?
- zone of demineralised dentine
- acid demineralisation (no bacteria)
