lesion initiation and progression

Question 1

define plaque biofilm

Answer 1

community of micro-organisms attached to a surface

Question 2

what makes a tooth surface suceptible to caries?

Answer 2

1. pellicle formation (protein rich film derived from saliva)
2. plaque stagnation areas take 0-4 hrs to colonise gram -ve bacteria

multi-colony formation takes 4-24hrs

Question 3

give examples of plaque stagnation areas

Answer 3

• occlusal surface (pits and fissures)
• approximal surface with adjacent tooth
• sites adjacent to partial dentures
• sites adjacent to restorations

Question 4

what is cariogenic bacteria? and what are they two types of cariogenic bacteria?

Answer 4

bacteria capable of causing caries

1. acidogenic - transforms sugars from diet into acid
2. aciduric - thrive at low pH

Question 5

what is the microbial succession?

Answer 5

streptococci —–1 to 14 days——->actinomycetes

Question 6

what are the 3 theories of caries progression

Answer 6

1. specific plaque hypothesis
2. non-specific plaque hypothesis
3. ecological plaque hypothesis

Question 7

what is the specific plaque hypothesis?

Answer 7

States that out of around 300 species of bacteria in the mouth that ONLY A FEW of these microorganisms are cariogenic

Giving the idea that we could immunise against these bacteria

Question 8

what is the non-specific hypothesis?

Answer 8

States that caries is a result of the OVERALL activity of all he micro-organisms within the biofilm

Giving the idea that all plaque should be removed

Question 9

the ecological plaque hypothesis is?

Answer 9

States that the microflora changes depending upon local environment (stagnation areas/sugar/saliva) which in turn favours acidogenic and aciduric bacteria.

Giving the idea that plaque should be removed from suceptible sites and sugar intake reduced

Question 10

what is the stefan curve?

Answer 10

a sucrose rinse is given (low oral pH) and the gradual rise in pH is observed.

conclusion = increased frequency of refined carbohydrate intake is more harmful than the amount of sugar a the oral environment never gets the opportunity to return to a normal pH

if saliva flow restricted after sucrose rinse then increased time to return to pH 7 - possibly due to less buffer in saliva

Question 11

the infected zone is also called..?

Answer 11

the outer zone

Question 12

the affected zone is also called..?

Answer 12

the inner zone

Question 13

ways that the biofilm can be challenged?

Answer 13

• good OH
• fissure sealant
• ultraconservative caries removal
• stepwise excavation

Question 14

what is stepwise excavation?

Answer 14

1. removal of superficial layer of necrotic dentine
2. ensure peripheral caries removal but base of cavity may have some caries left
3. place CaOH lining and GI
4. leave for 6-12 months for pulp-dentine reaction and aiming to see a decreased level of infection with the cavity being harder, dry and dark
5. on second visit ensure that you re-clean the cavity and permanently restore