CAP2 + 3- Enamel and dentine caries Flashcards
What is dental caries?
progressive destruction of the tooth surface
what is dental caries initiated by?
microbial activity at the tooth surface (crown or exposed root)
Depending on the environment , how can caries progress?
- Can progress unhindered to pulp
- Can remineralise (can arrest)
What 4 factors are needed for dental caries to occur?
- plaque bacteria
- time
- substrate
- susceptible tooth
what can be used to stop a susceptible tooth?
Fissure seal to prevent - acid etch and apply resin to smooth out surface and make suspectible area non-susceptible
What does brushing teeth do to prevent caries?
Takes out time factor and can be managed by diet
what are the 4 non-carious causes of tooth surface loss?
- Erosion
- Abrasion
- Attrition
- Abfraction
What is erosion?
Acid from gastric reflex- balemic patients , reflux disorders , low pH from stomach ,palatal surface -palatal erosion
other acid to cause erosion : diet- acidic food(fruit, drinks)
What is abrasion?
Abrasion-tooth brush abrasion, tooth wear caused by something outside the mouth touching the tooth (toothpaste), vigorous brushing with whitening toothpaste
What is attrition?
Tooth on tooth wear -this can be incisal ,occlusal and aproximal
What is abfraction?
Explains cervical notches, weaking of cervical aspect of the tooth ,when you bite hard on something, tooth flexs, cause micro cracks at cerical margins where enamel is thin
What are the key observations of acidogenic theory?
– many organisms can produce acid from fermentation of sugar
– Many oral bacteria produce lactic acid
– Sugar/bread + saliva + bacteria + extracted teeth = demineralisation
How is acid produced at tooth surface?
Bacterial fermentation of dietary CHOs
what does boiling microbes do?
-stopped acid production
– acid production needed starches and sugars
– no acid production if lean meat or fats were the substrate
What is the enamel structure of the prism core?
– Tightly packed hydroxyapatite
– Little inter-crystalline spaces
What is the enamel structure of the prism sheath?
– Less well packed crystals
– Space (= pores) contains water and organic material
– Allows easier diffusion of acid
– Where demineralisation starts
What is the clinal appearance of enamel caries?
- “white spot lesion”
- Matt appearance
what is required to see enamel caries clinically?
– Clean teeth – plaque free
– Dry teeth
what do areas that are demineralised look like when light is shone through?
looks darker
what does the appearance of enamel caries depend on?
- Refractive index (RI) of the mounting medium
- penetration of the medium
- RI Air = 1.00
- RI Enamel = 1.62
- RI Water = 1.33
- RI Quinoline = 1.62 – a large molecule
- Water or air appear dark
what does enamel and caries look like on a radiograph?
- enamel looks lighter on radiograph , but caries looks darker
- different zones reflecting -different zones of activity
what are the lesion zones from the advancing front?
- Translucent zone
- Dark Zone
- Body of Lesion
- Surface Zone
Describe the features of the translucent zone.
- 1st carious change
- Loss of ~1-2% mineral
- 5-100μm wide
- ~50% of cases
- Few large pores due to loss of prism periphery
What happens to the translucent zone when penetrated by quinoline?
– Appears structure less/translucent
– Quinoline fills prism periphery
Describe the features of the dark zone.
- Dark brown with quinoline
- Seen in 90-95% of lesions
- Porosity now 5-10%
- Consists of:
>Large pores
> Small pores
• not penetrated by quinoline
• appears dark
- Demineralisation and remineralisation occurring
Describe the features of the body of lesion.
- the largest part and centre of the lesion
- 25-50% porosity
- enamel is relatively
translucent
- striae of Retzius more obvious
- corresponds to the radiographic appearance
Describe the view of the body of lesion in a radiograph.
Resin gets into spaces and so looks light because light shines through it
the radiograph under estimates the extent of caries
for caries- bite wing photo- in this if caries looks close to dentine, probably is affecting dentine already
Describe the features of the surface zone.
- Relatively intact
- ~30μm thick
- Highly mineralised – high F- content
- Porosity of ~1-2%
> Protected
> Forms / reforms during carious
process?
• Redeposition of mineral dissolved from deeper layers
what can plaque do for the surface zone?
plaque limits how ions diffuse in and out, forms barrier to diffusion
presence of plaque- gives this surface zone - provides some protection
What should you not do to a carious lesion?
probe it
Describe the pore structure of carious enamel.
Translucent zone- acid demineralisation causes spaces in the translucent zone
Dark zone- porous
body of lesion- full of big spaces because the loss of a lot of enamel
Surface zone- porous
Describe arrested caries.
> Remineralised > Changes in environment: – Plaque control + F- – Altered diet > Can be brown – exogenous stains > Histologically: wide, well-developed dark zone
what is the appearance of where demineralisation takes place?
dark zone
why is dentine a vital tissue?
it controls cell processes
why is it hard to clean plaque away from approximate surface?
Toothbrush does not fit
what happens when the caries is advancing front AT dentine?
- sclerotic dentine
- DENTINE RESPONSE- reactionary tertiary dentine
what happens when the caries is advancing front IN dentine at the intact surface?
- Demineralisation
- No bacterial invasion
what happens when there is a cavitation in the lesion?
Enamel Cavitation:
• Demineralisation
• Bacterial invasion
what happens when the cavitation spreads towards pulp?
spreads towards the pulp and laterally dentine lesion is wider than enamel (not at a point) as it spreead along ADJ
what are the zones in dentine following cavitation from the enamel inwards?
- zone of destruction
- zone of bacterial penetration
- advancing front in dentine
- sclerotic dentine
Name the defence response of zones of established dentine caries.
- reactionary tertiary dentine
- translucent /sclerotic zone (blocks tubules)
what happen if there is rapid progression of dentine caries?
– No sclerosis
– Odontoblasts die
– Possibly reparative tertiary dentine
Describe the advancing front zone.
– Zone of demineralised dentine
– Acid demineralisation, no bacteria
Describe the zone of bacterial penetration.
– Bacteria in tubules
– Lateral spread via branched tubules
– Lactobacilli
Describe the zone of destruction.
– Mixed bacterial population : 2ry infectors
– Proteolytic enzymes
– Destroys organic matrix
what are the 2 main zones in dentine caries?
- outer, superficial zone
- inner, deeper zone
Describe the outer, superficial zone.
– Highly infected
– Irreversibly demineralised dentine
– Proteolytic degradation of collagen matrix
Describe the inner, deeper zone.
– Dentine has been reversibly attacked
– Collagen matrix not severely damaged
– Minimally infected
– Potential for repair
How many lesions are in occlusal caries?
2
what do the lesions follow in occlusal caries?
prisms
why is the lesion wider in occlusal caries?
Caries follows prism direction- it doesnt reach dentine at a point, it gets wider and so lesion is wider towards dentine
How detectable is occlusal caries?
hard to detect -looks intact but damage is severe
what can be done to treat occlusal (fissure) caries?
Non cleans-able fissure becomes cleans-able after fissure seal
