Lecture 9: Oral Cavity as a microbial habitat-dental biofilms

Question 1

What is the hardest substance? (according to Puri)

Answer 1

Dentin

Question 2

What is the plaque above the gum line called?

Answer 2

Supragingival plaque

Question 3

What is the plaque below the gum line called?

Answer 3

Subgingival plaque

Question 4

What is the typical temperature range of the healthy oral cavity?

Answer 4

35-36C

Question 5

How does temperature effect microbial growth in the oral cavity?

Answer 5

can increase to 39C in periodontal pockets with inflammation

-change can regulate gene expression in bacteria for genes encoding enzymes (proteases, SOD) and Fimbriae

Question 6

What does SOD (superoxide dismutase) do?

Answer 6

removes oxidative stress

Question 7

What is the oxygen tension on the tongue?

Answer 7

varies from 12-16%

Question 8

What is the oxygen tension on the buccal folds?

Answer 8

0.3-0.4%

Question 9

Which colonizers are more aerotolerant?

Answer 9

Early colonizers

Question 10

How does redox potential affect microbial growth in the oral cavity?

Answer 10

• Redox changes oxygen tension
• oxygen content varies between location
• Most oral organisms are facultative or obligate anaerobes

Question 11

How does the saliva regulate pH?

Answer 11

the bicarbonate in saliva acts as a buffer and therefore is responsible for regulating pH

Question 12

How does sugar intake affect the pH of the oral cavity?

Answer 12

sugar will cause a decrease in pH due to the byproducts of bacteria (lactic acid) after it metabolizes the sugar
sugar decreases pH (fermentation)

Question 13

What is the pH range for a healthy oral cavity?

Answer 13

6.75-7.25

Question 14

What is the pH for the Palate?

Answer 14

7.34

Question 15

What is the pH for the buccal mucosa?

Answer 15

6.3

Question 16

What is the pH of the healthy gingival crevice?

Answer 16

6.9

Question 17

What is the pH of diseased gingival crevice?

Answer 17

7.4+

Question 18

What disease is related to a decrease in pH?

Answer 18

Caries

Question 19

What disease is related to a increase in pH?

Answer 19

Periodontitis

Question 20

What pH range are S. mutans able to live/survive in?

Answer 20

pH4-8, causes caries

Question 21

What pH range can P. gingivalis live/survive in?

Answer 21

pH 6-8.5 causes Periodontitis

Question 22

What are the Endogenous nutrients?

Answer 22

Whats already present:
Saliva (amino acids, peptides, proteins)
GCF (albumin, protein)
Bacterial products

Question 23

What are the Exogenous nutrients?

Answer 23

stuff you consume:
Dietary (fermentables, carbohydrates, metals)
excess iron can cause bacterial growth

Question 24

What are the Specific Host Defense Factors of the mouth?

Answer 24

Intra-epithelial lymphs (langerhans cells)
slgA
IgA, IgG, IgM
Complement
Neutrophils/macrophages

Question 25

What is the source of IgG, IgA, IgM and complement?

Answer 25

GCF

Question 26

What favors Expulsion/Death of bacteria entering the mouth?

Answer 26

Mechanical shearing Antimicrobial properties Antagonistic bacteria Agglutination

Question 27

What favors the Colonization of bacteria entering the mouth?

Answer 27

Nutritional substrates Adherence properties Temp and moisture Synergistic bacteria

Question 28

What are the antimicrobial agents that affect the microbial growth in the oral cavity?

Answer 28

Fluoride Chlorhexidine Antibiotics

Question 29

What is Quorum Sensing?

Answer 29

Intercellular signalling as a regulatory mechanism that plays a significant role in coordinating various stages of biofilm - Responds to population density - Controls gene expression - Capable of auto-induction - self-recognized secreted molecules called auto-inducers

Question 30

What are the stages of dental plaque formation?

Answer 30

1. Pellicle Formation 2. Association (Reversible binding) 3. Adhesion (Irreversible binding) 4. Coadhesion: secondary colonizers that attach to primary colonizers with the help of Lectin

Question 31

What mediates coaggregation/coadhesion of interbacterial interaction?

Answer 31

Lectins

Question 32

What are the components of the acquired enamel pellicle?

Answer 32

``` Salivary proteins & Glycoproteins (Sialic acid, proline-rich proteins -PRP, Mucins, Agglutination, Amylase) Bacterial Components (glucan, glucosyltransferases) ```

Question 33

What are the beneficial factors of microbial interactions in dental plaque?

Answer 33

``` Enzyme complementation Food Chains Coadhesion Cell-cell signalling Gene transfer ```

Question 34

What are the antagonistic factors of microbial interactions in dental plaque?

Answer 34

``` Bacteriocins Hydrogen Peroxide Organic acids Low pH Nutrient Competition ```

Question 35

What factors affect microbial growth in the oral cavity?

Answer 35

``` Temp Redox potential pH Nutrients Host Defenses Host Genetics Antimicrobial agents & inhibitors ```