Microbiology Of Caries

Front 1

Caries - factors

Back 1

1) Key Oral Microorganisms
i) Lactobacillus
ii) Bifidobacterium
iii) Mutans Streptococci
2) Susceptible host
i) Sjrogens syndrome
ii) Cancer patients
3) Environmental factors
i) Poor diet with fermentable sugars
ii) Poor oral hygiene
iii) Xerostomia
Confounding factors: Fluoride availability, diverse natural microbiota, non specific virulence traits.

Front 2

What evidence is there that caries is an infectious disease?

Back 2

1) Gnotobiotic animal studies (Sterile animals, causative relationship)

2) Human epidemiology studies

- Cross-sectional (Correlation)

- Longitudinal (Causation)
3) Vaccination (unethical to do on humans)

Front 3

Microorganisms that cause caries

Back 3

Streptococcus mutans: Gram +ve cocci, causative + associative, form adhesins

S. Sobrinus

Lactobacillus: Gram +ve rod, implicated in advanced caries

Bifidobacterium: Gram +ve rod, implicated

Front 4

Challenges faced when finding out microbial aetiology of caries

Back 4

1) Disease occurs at sites with natural, diverse microbiota

2) Pathogen found in healthy sites in small numbers

3) Difficult to correlate microbiota to enamel status

4) Lesions can remineralise

5) Pathogenic traits non specific (can't differentiate)

6) Multifactorial nature of caries

Front 5

What role do other microorganisms apart from S.mutans play?

(See next flashcard for A.Naeslundii)

Back 5

S.Mitis + S.Oralis: Acidogenic

Veillonella Spp. Gram -ve, anaerobic, uses lactic acid -> proprionate/acetate

Salivarius: Urea + H20 -> Ammonia + CO2

Front 6

A.Naeslundii converts arginine to ammonia: what are the steps for the urea cycle

Back 6

Front 7

Timeline of microorganisms

Back 7

Nursing bottle caries: Mutans streptococci + Lactobacilli

Root Surface Caries:

Early studies: Actinomyces SPP.

Later studies: Mutans Streptococci + Lactobacillus

Recent studies: Actinomyces Spp., Mutans Streptococci, gram -'ve rods, Actinomyces israelli

Front 8

Diet of bacteria

Back 8

In health: Bacteria live off glycoproteins - long time to break down + easily buffered

In caries: Fermentable sugars, frequent exposure to biofilm, rapidly metabolised, slow buffering

Front 9

Characteristics of cariogenic bacteria

Back 9

Rapid sugar transport + acid production

Acidurity (acid tolerance)

EPS - Sticky polymers (adhesins)

IPS - Storing excess sugar as glycogen

The main characteristics of cariogenic bacteria are rapid sugar transport, high acid production and high acid tolerance.

Front 10

Hypotheses relating plaque to caries

Back 10

1) Specific plaque hypothesis

Specific microorganisms in the plaque lead to caries

2) Non-Specific plaque hypothesis

All bacteria do different things which have a net effect

3) Ecological plaque hypothesis (lecturer prefers this)

Balance between bacteria + sugar, aetiology of plaque doesn't not monospecific.

Environmental regulation of gene expression

Front 11

Disease is preventable/controllable by:

Back 11

1) Direct inhibition of the organisms that cause disease

2) Maintenance of a natural balance of microorganisms with non out-competing each other

3) Interference with factors causing damaging shifts in microbiota (fermentable sugars = <acid, ecology of microorganisms changed -> caries.
Can be reduced by better oral care, fluoride, change in diet

Front 12

How can you control dental caries

Back 12

1) Plaque control brushing, flossing, dentists

2) Fluoride To form fluoroapatite, helps remineralise, acidify cell interior, inhibit IPS synthesis, reduces glycolysis

3) Sugar substitutes Bulking agents: xylitol, sorbitol, intense sweeteners Saccharin

4) Antimicrobial/antiplaque agents: Toothpastes + mouthwashes, chlorhexidine,

5) Replacement therapy: Dairy strains: exclude cariogenic bacteria, S.Salivarius: bacteriocin producing strains, GM S.Mutans: Don't produce acid, exclude other S.mutans

6) Vaccinations: SlgA, IgA, neutrophils. Vaccines (untested on humans)

7) Passive immunisation: Coating surfaces with antibodies, reduces MS colonisation, safe + acceptable, non-invasive procedure.