Cariology First Test

Question 1

Country A has a DMFT score of 1 and Country B has a DMFT score of 3. What can you say about Country A compared to Country B? How do you calculate DMFT?

Answer 1

People in Country A generally have better oral health than people in Country B.

The lower the DMFT score, the better average oral health is.

DMFT is the sum of the Decayed, Missing and Filled permanent teeth (divided by population).
DMFT measures caries prevalence.

Question 2

Humans that have completely sterile mouths cannot develop caries. True or False?

Answer 2

True

Question 3

What are two host factors that increase susceptibility to dental caries?

Answer 3

Lowered salivary flow rate ; Hyposalivation or Xerostomia

Poor buffering capacity (naturally low salivary pH)

Teeth with deep fissures

Question 4

What are the 3 types of caries?

Answer 4

1) Smooth Surface Cavity
2) Pit and fissure Cavity
3) Root Cavity (in Cementum)

Question 5

Omid and all the bacteria that live inside and on him can be described as the:

Answer 5

Holobiont

Question 6

What is the difference between microbiota, microbiome, holobiont, and micro flora?

Answer 6

Microbiota is all the living microbes
Microbiome is microbiota + the habitat (ie gut microbiome)
Holobiont is a discrete ecological unit (species + microbiomes (ie humans))

Microflora is all the living microbes that are plants

Question 7

The human microbiome project was a principle component analysis. What was interesting about the oral microbiome compared to the nasal microbiome?

Answer 7

Our oral cavity has microbial communities that are more similar to each other compared to our nasal cavity. This is dictated by the dispersion of the points on the principle component analysis graph.

Question 8

Every human has similar microbes in their oral cavity. Every human has similar microbes on their skin.

A) Both statements are true
B) One statement is false
C) Both statements are false

Answer 8

A) Colonization is generally site-specific

Question 9

How can oral bacteria influence systemic health? (3 points)

Answer 9

1) Chronic oral inflammation can cause inflammatory mediators to circulate in our body.

2) Oral microbiota can colonize non-oral sites.

3) Colonization of non-oral sites can lead to inflammation of those sites.

Question 10

What are ways oral microbiota benefit us? (3 points)

Answer 10

1) Non-carcinogenic/benign bacteria can colonize surfaces and prevent the colonization of harmful pathogens.

2) Modulate our immune fitness/response; train immunostimulatory and immunosuppressive mechanisms

3) Metabolite Nitrate to NO

Question 11

What are the benifits of NO?

Answer 11

Anti-thrombotic, Anti-proliferation, Anti-atherogenic

Question 12

How is dietary nitrate metabolized by oral microbiota?

Answer 12

1) Eat nitrate
2) Nitrate secreted in saliva
3) Bacteria reduce nitrate into nitrite
4) Nitrite becomes NO in stomach

*Reduction rxns

Question 13

How are bacteria classified?

Answer 13

Morphology, Simple physiology, Cell component analysis

M- Size, Shape
SP- What substrate they use
CCA- Cell wall comp, proteins, etc

Question 14

What are the differences between gram positive vs gram negative bacteria?

Answer 14

GP- Purple when dyed, Thick PG wall, Techoic acids

GN - Pink when dyed, Thin PG wall, LPS cell membrane

Question 15

Streptococcus is gram ________. What are two things about general streptococcus physiology that we have to note?

Answer 15

Gram positive

1) Facultative anaerobes (prefers O2 but can live without)

2) Fermentative metabolism

Question 16

Discussion Class Question:

In what ways might the oral microbiota contribute to oral/general health?
What common bacterial species do you expect to find in the oral cavity? (we will build on this over the next couple of weeks)
Streptococcus sanguinis is not associated with oral disease, but why is it interesting? (You will find the answer to this in the video on Canvas)

Answer 16

Open ended

Question 17

What is gingival crevicular fluid (GCF)?

Answer 17

Fluid in the gingiva sulcus

Question 18

Explain the process of microbes forming a biofilm on a tooth. Start with a clean, sterile, tooth surface.

Answer 18

1) Salivary molecules (proteins/glycoproteins) bind onto enamel forming the acquired pellicle (aka conditioning film).

2) Adhesins on microbes bind onto receptors on the conditioning film.

3) Microbes multiply and facilitate binding of more microbes.

4) Quorum sensing releases auto-inducers that stimulate extra-cellular matrix secretion.

Question 19

Monozygotic twins are likely to have a more similar oral microbiome than dizygotic twins. True or false?

What are the exceptions to this?

Answer 19

True

Only possible when co-habiting together. Differences are seen when twins are separated and raised in different households.

Question 20

How do genetics influence oral microbiome?

Answer 20

1) Salivary flow rate variances
2) Taste receptor and food preferences
3) Immune molecules and other molecular variances (ie muffins, histadins)

Question 21

A baby is born. Explain the progression and changes in his microbiota overtime.

Answer 21

1) No teeth, only mucosa: Pioneering microbes, particularly streptococcus (S.mitis, s.oralis, s. sanguinis). These colonize because they can defend against IgA with protease

2) Eruption of teeth enable new surfaces for microbes to grow on *(No diff, mixed findings)

3) Dietary changes provides new substrates for microbes to feed off of

Question 22

Saliva contains anti-microbial properties. True or false?

Answer 22

True

Question 23

What are ways our mouth cleans itself of bacteria?

Answer 23

1) Saliva flow washes bacteria area

2) Destroy bacteria. Ie. Lysozyme in saliva lyse bacteria

3) Sequester essential nutrients. Ie. Lactoferrin binds iron in saliva, making bacteria die (Fe is essential for metabolism)

Question 24

GCF is can promote and demote bacteria growth. Argue both sides of this statement.

Answer 24

GCF is full of nutrients. High protein concentration and haem-containing molecules make it a favourable spot for bacteria to grow.

GCF also contains a lot of defense mechanisms to protect against bacterial growth, such as immune cells (leukocytes)

Question 25

Open ended:

Q: What different factors might be associated with an increased microbial diversity from initial colonisation at/after birth to “microbial homeostasis” in a healthy adult?

Q: Discuss how the different factors influencing the composition of the oral microbiome can do so? (you will build on this information as you move through the year)

Q: Compare the use of DNA probes with DNA sequencing for examining the oral microbiome. What are the advantages and disadvantages of these techniques? What do you need to consider when comparing clinical studies employing different laboratory techniques?

Question 26

What are the techniques for detecting microorganisms and what are the pros/cons for each technique?

Answer 26

DNA sequencing

Pros: Can detect large amounts of information/species, dead is fine, no need to cultivate
Cons: high error rate, high computation, easy contamination

DNA probe
Pros: dead is fine, multiple species
Cons: only can target specific species

Bacterial culture
Pros: can investigate physiology , anti microbial resistance, and biochemistry
Cans: must be alive, cannot culture fastidious orgnaisms

Question 27

Name as many bacteria in the oral microbiome as you can and their relevance

Answer 27

Streptococcus mitis - infective endocarditis
Streptococcus mutans - infective endocarditis on valves
Actinomyces israelli -cervicofacial actinomycosis
Lactobacillis casei - dental caries
Cornebacterium sp. - plaque development
Neisseria sp. - early colonizer
Veillonella sp - early colonizer; can reduce harmful effects of lactic acid through conversion to weaker acids

Fusobacterium nucleatum - Secondary coloniser, bridging organism for coaggregration
Prevotella spp. - Secondary coloniser

Porphyromonas gingivalis - periodontal disease + bone/tissue destruction host immune response ** protein for metabolism
Tannerella forsynthia - late coloniser periodontal disease
Trepnonema denticola - later coloniser periodontal disease
Aggregatibacter actinomycetemcomitans -late coloniser - capnophilic + aggressive periodontal disease

Question 28

What are the features of a biofilm?

Answer 28

Heterogenous structure

1) Bulk fluid layer above
2) Channels for nutrient and waste diffusion
3) Dense lower microbe layer bound together by polysaccahride matrix

Question 29

5 interactions within biofilm?

Answer 29

1) Food sharing
2) Protection of environmental conditions
3) Killing
4) Travel
5) Quorum Sensing

Question 30

Bacteria A, B, C, and D are studied by scientists. When each bacteria is cultured alone, bacteria C dies and bacteria A,B,D grows. Co-culturing bacteria C with A, results in normal growth for both bacteria. When bacteria B is added to the culture with bacteria C and A, all species exponentially grow beyond the scientist’s expectations. However, when bacteria D is added to the culture of BCA, bacteria C starts to die; the rest of the bacteria grow normally.

Explain all the interactions in this bacterial culture cocktail.

Answer 30

A and C is commensalistic

B, C, and A are synergistic

D is antagonistic towards B,C,A

Question 31

Autoinducers affect __________, and are used to monitor _________. The two types of Autoinduces are _____ and ______, with the first type being ________ and the second type being _______.

Answer 31

Gene expression, population size. AI-1, AI-2, species specific, non-species specific.

Question 32

How do biofilms benefit microorganisms?

Answer 32

1) protect from host defense (ie leukocytes)

2) protect of antimicrobial agents

3) Enhanced virulence (closer together, pathogenic synergism)

4) Broad habitat range in plaque (many different niches)

Question 33

Difference of planktonic culture vs biofilm culture? (1 point)

Answer 33

Protein expression is different

Question 34

Open ended:
Q. Describe some of the ways bacteria may interact with one another.
Q: Describe quorum sensing. How is it beneficial for microorganisms? How could it be exploited for biofilm-associated disease prevention?
Q: What are some benefits afforded to bacteria growing as a biofilm compared to growing planktonically?
Q: Bacteria growing as a biofilm have a decreased susceptibility to antibiotics. How can this decreased susceptibility be explained?

Question 35

After you brush your teeth, when does dental plaque form?

How does it form?

Answer 35

It forms immediately after brushing.

1) Development of acquired pellicle from salivary proteins/glycoproteins
2) Microbes in saliva bind to pellicle via adhesin-receptor interactions; this is called adhesion
3) Bacteria bind onto other bacteria; coadhesion (coaggregation) via A-R interactions
4) Multiplication
5) Detachment of bacteria from plaque to colonize elsewhere

Question 36

In saliva, there are 3 mystery proteins (X, Y, Z) that bind onto the tooth surface and form the pellicle. Protein X and Y are larger than Protein Z. Protein X and Y first bind onto the tooth surface, followed by protein Z.

Why does this occur?

What can you tell about the composition of each protein?

Answer 36

The surface of enamel is charged with negative and positively charged ionic structures. Therefore, you can suggest that protein X and Y have charged amino acids. Such amino acids include phosphoserines, aspartates, histadins.

Protein X and Y are likely histatins and statherins, that are charged and have higher binding affinity to enamel.

Question 37

Open ended:

Studies of dental plaque development indicate that there may be a ordered sequence to the colonisation by different bacterial species. How might this ordered colonisation be explained?

• Describe the various components of the dental plaque biofilm including their origin and role
in dental plaque (we will build on this over the next few lectures).
Answhattasked

Question 38

Bob eats about 100 grams of sugar per day. Bill also eats 100 grams of sugar per day. Bob and Bill are monozygotic twins living in the same household with a similar diet. Despite this, Bob suffers from multiple dental caries compared to Bill. Explain why this might be the case?

Answer 38

Frequency of sugar consumption matters. Frequent sugar consumption can cause:

1) vertical compression of remin/demin curves
2) decrease oral microbiota diversity and species richness
3) increase in stretococci (non-mutans)
4) promote growth of bacteria (cariogenic) with frequent nutrient source

Bob likely eats 100g of sugar through “snacking” throughout the day while Bill likely eats 100g of sugar in an intermittent fasting diet (1-2 meals).

Question 39

Below are some bacteria that colonize supragingival plaque. Propose an ecological succession theory.

• • Aerobic
    ** - Falculative Anaerobic
    *** - Anaerobic
    + - Strictly saccharolytic

Bacteria X **+
Bacteria Y **
Bacteria Z ***

Answer 39

Y , X , Z

salivary proteins and glycoproteins are the primary nutrient source for oral bacteria and most frequent/abundant

Y colonizes first.

After food intake, carbs become available, X colonizes

Z can only colonize once plaque is formed and anaeorobic environement is established

Question 40

What are the reprucussions to consistent low plaque ph?

Answer 40

1) Promotion of acidogenic/aciduric species
2) Favoured formation of DCPD crystals

Question 41

What are koch’s postulates?

Answer 41

The micro-organism must be present in every case of the disease, but not in healthy individuals

The micro-organism must be isolated from the diseased individual and grown in a pure culture

The isolated micro-organism should reproduce the specific disease when inoculated into a healthy individual

The same micro-organism must be re-isolated from the experimental infection

Question 42

Why are Koch’s postulates debunked?

Answer 42

Microorganisms associated with plaque-related diseases are part of the normal oral microbiota

Some micro-organisms are not easily grown (fastidious)

Sometimes more than one micro-organism is involved (polymicrobial)

Question 43

What are Socransky’s modifications to koch’s postulates?

Answer 43

In order to be considered a causative agent of disease an organism should meet the following criteria:
– Present in high numbers in disease
– Absent,or in low numbers in health
– Mimic human disease in animal models
– Produce virulence factors which correlate with damage seen – High levels of antibody in diseased subjects
– Removal of the organism results in clinical improvement

Question 44

What is critical pH and why is it important?

Answer 44

Ph of 5.2 -5.4

Causes HA dissociation into ions

Question 45

What are the 3 theories of plaque and dental caries development?

Answer 45

1) Non-specific Plaque hypothesis - Chemico-parasitic — fermentation of sugars cause dissolution of HA (all plaque causes disease)

2) Specific Plaque Hypothesis - Certain species in plaque cause caries (ie. S.mutans)

3) Ecological Plaque Hypothesis - Polymicrobial consideration: cariogenic bacteria exist in dental plaque and only cause issues when there is net demin,

Question 46

Open ended

If the ecological plaque hypothesis explains how dental caries is caused, how would it help you treat and prevent future disease?

How is your dietary advice to a patient for caries prevention related to the ecological plaque hypothesis? (you will build on this during the year)

What lifestyle choices in addition to diet might reduce the ecological pressure selecting for aciduric species? How might they reduce the ecological pressure?

Question 47

What are factors that make a highly cariogenic bacteria? (Virulence factors)

Answer 47

1) Highly efficient sugar transport system
2) Fast glycolytic rate/metabolism; acidogencity
3) Aciduricity: survive in low pH
4) Adherance; able to adhere to surfaces
5) Polysaccharide production: Contributes to plaque matrix (ECM), and produces acids without sugars (dietary)

Question 48

List some specific virulence factors of s.mutans:

Answer 48

1) PEP:PTS System (highly efficient) for wide range of sugars and host glycoproteins (oligosaccharides)

2) ATP Binding Cassette (ABC) system for metabolism of sugars and transporting breakdown products of EC poly sac

3) Glucosyltransferases (GTFs) allow Glucan production

4) Synthesize glycogen (Glycogen-like glucose homopolymer) for intracellular polysaccharide storage

5) Adhesins (multiple binding capacity; salivary glycoproteins or other bacteria)

6) Acid Tolerance Response (ATR) —> gene expression and metabolism changes on acid exposure to protect/repair macromolecules and maintain intracellular pH

Question 49

Open ended:

Describe how each virulence factor discussed associated with dental caries.

Streptococcus mutans is associated with dental caries, but is often not dominant in dental plaque associated with caries. How can this observation be explained?

Question 50

In order to precipitate a crystal in solution, where the Ksp of the crystal is very high, the IAP must be also

Answer 50

very high

Question 51

A scientist is trying to create Hydroxyapatite in the lab. Explain to him what he needs to do.

Answer 51

Spatial delineation, Diffusion limited ion flow, Organic Matrix, Chemical Regulation

Question 52

A scientist has a lab that creates artificial hydroxyapatite. The lab produces 10 kg of hydroxyapatite everyday and makes over 10 mil in revenue. One day, a lab tech accidentally spills the anionic binding motifs into the solution in the production line. What do you think would happen?

Answer 52

Anionic binding motifs will prevent nucleation and inhibit crystal growth by sequestering cationic ions in solution.

Question 53

What are the reprecussions of cavitation?

Answer 53

1) Surface layer breaks
- allows for more diffusion of lactic acids
- allows for bacteria penetration to dentine