Aetiology of Dental Caries

Question 1

What is dental caries?

Answer 1

a bacterial disease of the calcified tissue of the teeth characterized by the demineralisation of the inorganic and destruction of the organic substance of the tooth

Question 2

What is the acidogenic theory?

Answer 2

dental lesions result from a shift in the metabolic activity accompanied by a gradual change in the ecology of the dental biofilm

an imbalance in the equilibrium between tooth mineral and biofilm fluid develops

Question 3

What do bacteria ferment to produce acid?

Answer 3

carbohydrate

Question 4

What does bacteria producing acid lead to?

Answer 4

decalcification of the hard tissue tooth substance and disintegration of the organic matrix

Question 5

What are the 4 factors associated with caries development?

Answer 5

microorganisms
time
food
tooth
saliva

Question 6

What are the primary modifying factors?

Answer 6

these are modifiable factors, patient can control

saliva
biofilm
pH
fluorides
oral hygiene factors

Question 7

What are secondary modifying factors?

Answer 7

Things the patient cannot control, but have a susceptibility to developing caries

socioeconomic background

age

ethnic group

unemployed

Question 8

Describe this diagram, caries development

1. what are the orange circles
2. what is the oink area
3. what is the green area
4. what is the yellow area

Answer 8

Orange circles represent teeth covered by microbial deposits

The metabolism in the microbial deposit will have an effect on pH (dependent upon acid attacks)

Overtime may result in caries/ demineralisation in the tooth (pink area)

green area influence demineralisation, patient can influence

yellow circle shows social factors which a patient cant influence

Question 9

How does saliva influence caries?

Answer 9

buffer ability

pH 6.8

Question 10

Is caries a multifactorial disease?

Answer 10

yes

Question 11

What is the acquired pellicle?

Answer 11

absorbed of mainly salivary glycoproteins that forms on clean enamel to which bacteria adheres

amorphous organic film formed of glycoprotein from salivary origin.

Question 12

Define dental plaque?

Answer 12

biofilm of bacteria embedded in a matrix of salivary mucins and extracellular polysaccharide polymers (glucans and fructans)

on all surfaces in the oral cavity

Question 13

What are the common monomers in dental plaque?

Answer 13

glucan and fructans

Question 14

What is a biofilm?

Answer 14

microbial community growing on a tooth’s surface

Question 15

What are the areas of pink and dark pink?

Answer 15

pink = pellicle

dark pink = plaque to the naked eye you would not see

Question 16

What are the 5stages of dental biofilm formation?

Answer 16

1. pellicle formation
2. attachment of early colonisers
3. co-adhesion and growth of of attached bacteria leading to the formation of microcolonies
4. microbial succession leading to increased species diversity concomitant with continued co-adhesion ad growth of microcolonies (1-7 days)
5. climax community/ mature biofilm (1 week or older)

Question 17

When does the climax community/ mature biofilm form?

Answer 17

1 week

Question 18

When do bacteria attach to pellcile?

Answer 18

0-14 hours

Question 19

When do co-adhesion and microcolonies form?

Answer 19

4-24hr

Question 20

What are the initial colonisers? (examples)

Answer 20

S. sanguis, S. oralis, S. mitis

95% streptococci

There are also actinomyces spp and neiserria spp

Question 21

What binds what, bacteria to pellicle?

Answer 21

receptors in pellicle attach to the adhesins in the Bactria

receptors attract bacteria to attach onto them

Question 22

What acts as the primary source of carbohydrates and amino acids in the initial coloniser stage?

Answer 22

the salivary glycoproteins and proteins in the acquired pellicle

Question 23

Apart from streptococci, what other spp are in the initial colonisers?

Answer 23

Actinomyces and neiserria spp

Question 24

What species dominate the initial colonisers?

Answer 24

streptococcus

Question 25

What bacterial spp dominates the plaque community

Answer 25

actinomyces (microbial succession)

Question 26

What is the shift called from streptococcus to actinomyces?

Answer 26

microbial succession

Question 27

What happens to teh biofilm when actinomyces are presnt?

Answer 27

plaque

Question 28

What contributes to the biofilm matrix?

Answer 28

polysaccharides

glucans

Question 29

What type of bacteria present in the climax community (mature biofilm)?

Answer 29

majority facultative or obligately anaerobic

acid producing gram positive cocci

Also, gram positive rods

Question 30

What specific bacteria are found in the mature biofilm?

Answer 30

S. mutans

S. sobrinus

Question 31

What are the gram-positive rod in the mature biofilm?

Answer 31

actinomyces and lactobacilli

Question 32

Why can cariogenic bacteria survive but beneficial bacteria not?

Answer 32

cariogenic bacteria are acid tolerant