Lecture: Micro of Caries

Question 1

What three components form the multi factorial nature of Caries?

Answer 1

Key Oral Microorganisms
Susceptible Host
Environmental Trigger (poor diet./oh)

Question 2

What are the three groups of evidence for Caries as an infectious disease?

Answer 2

1) Gnotobiotic Animal Studies:
- Specificity -Diet -Transmission -Antimicrobial agents
2) Human Epidemiology Studies
- Cross sectional -Longitudnal
3) Vaccinations in Rodents and Primates

Question 3

Why are Vaccinations restricted to experiments?

Answer 3

Vaccines left for life threatening conditions

Question 4

What are the 4 implicated microbes in Caries?

Answer 4

Mutans Streptococci (MS)
Actinomyces
Lactobacilli
Bifidobacteria

Question 5

What are the species and serotypes of Mutans Streptococci?

Answer 5

Srep. mutans ( c,e,f)

Strep, sobrinus (d,g)

Question 6

What species and serotypes of MS are also found but not in humans?

Answer 6

Strep. cricetus (a)

Strep. rattus (b)

Question 7

What are the species of Actinomyces?

Answer 7

A. naeslundii
A. odontolyticus
(A. israeli/ A.gerencseriae)

Question 8

What is the species name for Lactobacilli and Bifidobacterium?

Answer 8

Lactobacillus spp.

Bifidobacterium spp.

Question 9

Describe Mutans Streptococci

Answer 9

• Gram Positive Cocci/short rods cocci bacilli
• Generally found on hard non shedding surfaces (not soft)
• Implicated in initiation of Caries
• Lot of acid production- pH 3.9-4.2
• Very Rapid Sugar transport
• High Acid Tolerence
• Produces Soluble and Insoluble EPS
• Produces IPS (Strep. sobrinus is low IPS)

Question 10

Describe Actinomyces

Answer 10

-Gram Positive branched rods
-Common in dental plaque
Spome species implicated in root caries
-Opportunistic Pathogen
-Medium sugar transport, little known about systems
-pH 4.4 to 4.8.
-Medium Acid Tolerence
-Medium EPS production
Produces IPS

Question 11

Describe Lactobacilli

Answer 11

• Gram Positive rod implicated in adcanced dental caries
• Later stages of disease
• Rapid Sugar Production little known about systems
• pH 3.8 to 4.1
• Very high growth at pH 5
• Low production of EPS
• Produces IPS

Question 12

Describe Bifidobacterium

Answer 12

• Gram positive rod
• Branched cells
• Recently implicated in Caries

Question 13

What are key differences in study deisgn to investigate microflora

Answer 13

Cross Sectional: Single time point samples compare areas of health to areas of disease
Longitudnal design:- Multiple samples over time and compare areas where disease occurred to areas of health

Question 14

What are the challenges in understanding the microbial aetiology of dental caries?

Answer 14

Challenges:

• Disease occurs at sites with natural, diverse microflora
• Pathogens found at health sites (often component of dental plaque))
• Lesions can remineralise
• Pathogenic traits are relatively non specific
• Multi-factorial nature of Caries

Question 15

What do cross sectional human studies show?

Answer 15

Increased MS at caries sites
(Proportions and isolfation frequency)
There is an INVERSE relationship between MS and Strep. sanguinis
Some sites with Caries have no MS, some sites have MS but not caries

Question 16

What do cross sectional studies show about fissure caries?

Answer 16

71% of Caries Fissures had >10% MS (percentage of total cultivable microflora)
70% of caries free fissures had no detectable MS

Question 17

What do longitudnal human studies show?

Answer 17

-Confirm increased MS at caries sites
MS can occur after first signs of demineralisation
Caries cna occur without MS
Role of other species in progression (Lactobacilli in advanced lesions)

Question 18

What role do other bacteria?

Answer 18

Some are acidogenic and low pH isolaes, eg Strep. mitis and Srep oralis. (Maybe also Actinomyces and Bifidobacterium)
Others are Lactate using species

Question 19

What species uses Lactate?

Answer 19

Veillonella spp. Converts Lactate into Propionate and Acetate
Veillonella is a gram negative coccus, anaerobic and utilizes acid in plaque
-Produces weaker acids

Question 20

What can be said about the variations in species and strain acid production?

Answer 20

Strep. sobrinus - very fast
Strep. mutans - very fast
Some overlap

Question 21

What three bacteria produce base and what specifically do they produce?

Answer 21

S. salivarius - urea
S. sanguinis -arginine
A. naeslundii - urea

Question 22

Briefly describe the Arginine deminase system

Answer 22

Arginine-> Citruline + AMMONIA

Citruline + Carbamyl -P -> ATP + CO2 + AMMONIA

Question 23

What is the role of Bacteria in Other forms of Caires?

Answer 23

Nursing Bottle Caries: MS and Lactobacilli
Root surface Caries:
Early studies: Actinomyces spp
Later studies: Mutans streptococci/ lactobacilli
Recent studies: DIverse microflora
Actinomyces spp. MS and gram negative rods

Question 24

What Culture Bacteria are found in Infected Dentine?

Answer 24

CULTURE: MS, Lactobacilli, Actinomyces spp., Gram negative Anaerobic rods (eg Prevotella spp.)

Question 25

What Molecular Bacteria have been found in Infected Dentine?

Answer 25

31 New Taxa Strep Mutans Eubacterium saburreum Diverse array of Lactobacillus spp (50% of species) Diverse array of Prevotella spp (50% of species)

Question 26

What does Data suggest about the make up of infected dentine bacteria?

Answer 26

Data suggest combinations of acidogenic bacteria combined with proteolytic and collagenolytic anaerobes

Question 27

What are the Bacterial Metabolism essential steps in Health and in Caries?

Answer 27

HEALTH: Host Glycoproteins-> Dental Plaque -> Slow acid production and neutral pH-> Little or no demineralisation In CARIES: Fermentable sugars-> Dental Plaque-> Rapid Acid Production -> Demineralisation

Question 28

What are the charecteristics of Cariogenic Bacteria?

Answer 28

- Rapid Sugar Transport and acid Productions (eg PEP-PTS Sugar Transport system) - Acidurity - Extracellular Polysaccharide (EPS) - Intracellular Polysaccharide (IPS)

Question 29

What are the characteristics of Strep. sanguinis?

Answer 29

``` Medium sugar transport pH 4.4- 4.8 Poor Acid Tolerance Soluble and Insoluble EPS produced Does produce IPS ```

Question 30

What are the three hypothesise for Plaque?

Answer 30

Specific P. H. (Target on certain types) Non specific P.H. (outcome related, net effect) Ecoological P.H.

Question 31

What characterises the Ecological Plaque Hypothesis?

Answer 31

Certain Bacteria Important Extended Ecological to show bacteria can adapt to new conditions AETIOLOGY MAY NOT BE MONO SPECIFIC many species contribute CARRIAGE OF PATHOGENS Clinically insignificant leves environmental regulation of gene expression DISEASE PREVENTABLE AND CONTROLLABLE BY direct inhibition of causative organisms- maintenance of natural balance- interference with factors driving deletrious shifts in microflora

Question 32

What are the four key elements in controlling dental caries? What three other approaches also exist?

Answer 32

``` PLAQUE CONTROL FLUORIDE SUGAR SUBSTITUTES ANTIMICROBIAL & ANTI PLAQUE AGENTS Replacement therapy, Vaccination, Passive immunisation ```

Question 33

What does the Fluoride approach to Controlling Dental Caries involve?

Answer 33

- Fluorapatite - Remineralisation (targeted) - Acidify cell interior (H+F-) - Inhibit IPS synthesis - Remove competitve opportunity for MS (low pH environment)

Question 34

What does the Sugar Substitute approach to Dental Carie involve?

Answer 34

-Bulking agents (Sorbitol , Xylitol) -Intense Sweetners (Saccharin , Aspartame) -Not, or weakly metabolised to Acid -Stimulate Saliva Flow -Weal antimicrobial activity (Xyltol to s. Mutans) -

Question 35

What is the Antimicrobial and Antiplaque approach in controlling caries?

Answer 35

- Toothpastes and mouthwashes - Chlorhexidine gold standard anti plaque - Triclosan, metal salts, plant extracts - MIC v sub MIC effects (eg inhibit glycolysis , sugar transport) - Antimicrobial and antiplaque activity

Question 36

What is replacement therapy?

Answer 36

Probiotics in oral cavity to reduce of effect of carious bacteria Dairy Strains: Exclude cariogenic bacteria ? Strep. salivarius is a bacteriocin producing strain

Question 37

Describe Caries Vaccination

Answer 37

Mouth has full immune response Streptococci are targetable pathogens Vaccines based on whole cells, glucosyltransferases, cell wall associated proteins Vaccines worked in rodents and primates, no approval for humans

Question 38

What is Passive Immunisaiton?

Answer 38

- Coat surface with ANTIBODIES or SYNTHETIC ANTIBODY FRAGMENTS - Reduces MS colonisation - Safe, acceptabel and non invasive