Role of Oral Biofilm (Amaechi 5)

Question 1

Caries is a _____ dependent oral disease.

Answer 1

Biofilm

Question 2

The acquired salivary pellicle is a layer of structureless, homogeneous biofilm
formed post-eruptively, on the surface of dental
mineral, by the _____ adsorption of
_______ salivary glycoprotein.

Answer 2

• selective

- hydroxyapatite-reactive

Question 3

Pellicle composition:

1. ___% amino acids (___% acidic)
2. ___% Carbohydrates
3. ___% Lipids

Answer 3

1. 45-50%, 20%
2. 10-15%
3. 23%

Question 4

Functions of the pellicle include:

1. _____ of microorganisms
2. _____ – by selective permeability
3. ______ for microorganisms

Answer 4

1. Attachment
2. Protection
3. Substrate/nutrient

Question 5

_______ is a population of microorganisms growing on a surface, firmly attached to and enmeshed in an extracellular polysaccharide matrix.

Answer 5

Plaque Biofilm

Question 6

Bacterial plaque is soft, densely packed mass consisting by dry weight of:
___% bacteria
___% intercellular matrix

Answer 6

• 70%

- 30%

Question 7

The intercellular matrix is composed of:

• Carbohydrate ____%
• Protein ____%
• Lipid ____%
• Inorganic elements (including ____, ____, and ____)

Answer 7

• Carbohydrate 13-18%
• Protein 40-50%
• Lipid 10-14%
• Inorganic elements (including calcium, phosphate, and fluoride)

Question 8

Plaque is not removed by mouth rinsing, but is easily removed by ______.

Answer 8

Mechanical means (prophylaxis)

Question 9

Classifications of plaque

Answer 9

1. Supragingival

2. Subgingival

Question 10

Supragingival plaque

Answer 10

• located above the gingivae

- bacteria population predominantly Streptococcus spp. and Actinomyces spp.

Question 11

Subgingival plaque

Answer 11

• located underneath the gingivae

- predominantly anaerobic organisms

Question 12

Part of dental plaque formation is expression of _____, _____, _____, and _____ by S. mutans.

Answer 12

• Adhesin (Antigen I/II)
• Glucosyltransferase (gtf B,C, D)
• Fructosyltransferase (ftf)
• Glucan binding protein (GBP)

Question 13

_______ phase is characterized by rapid bacterial growth mediated by extracellular glucans and streptococcal glucan receptors.

Answer 13

Colonization (Accumulation)

Question 14

______ phase: early dominance by Streptococci followed by a shift towards more anaerobic and filamentous flora.

Answer 14

Remodeling

Question 15

3 stages of plaque formation

Answer 15

1. Initial attachment phase
2. Colonization (Accumulation) phase
3. Plaque biofilm formation phase

Question 16

Plaque composition:

1. Total bacteria count
2. Streptococci %

Answer 16

1. ≈ 2 x 1011 bacteria/g

2. 17-38%

Question 17

____ and ____ are present in high proportions on all sites on tooth surface.

Answer 17

Streptococcus and Actinomyces

Question 18

Carbohydrates of plaque composition exist mainly as extra-cellular polymers…

Answer 18

• Glucans (dextrans and mutans)
• Fructans (levans)
• Heteropolysaccharides

Question 19

Glucan-producers

Answer 19

Strep. mutans
L. casei
L. acidophilus

Question 20

Fructan-producers

Answer 20

Actinomyces viscosus

Strep. mutans

Question 21

Heteropolysaccharides-producers

Answer 21

Actinomyces viscosus

Question 22

Proteins of plaque composition have contributions from the following components of bacteria…

Answer 22

glucosyl transferase
glucanhydrolase
hyaluronidase
phosphatase
Protease
amylase

Question 23

Proteins of plaque composition have contributions from the following components of saliva and gingival fluid…

Answer 23

amylase
lysozyme
IgA
IgG
IgM
Albumin

Question 24

Lipids of plaque composition are mainly a component of bacterial ______.

Answer 24

Cell membrane

Question 25

Inorganic components of plaque composition are _____, _____, and _____.

Answer 25

Fluoride, Ca, and PO4

Question 26

______ is present in high concentration (14-20 ppm) and mainly bound to other inorganic components and bacteria.

Answer 26

Fluoride

Question 27

____ and ____ are also in high concentration and bound to saliva-derived proteins e.g. statherin.

Answer 27

Ca and PO4

Question 28

Plaque can be separated by centrifugation into | liquid (______) and solid (_______) phases.

Answer 28

-plaque fluid -bacteria/insoluble Matrix components

Question 29

Plaque fluid composition

Answer 29

Fluoride, Ca, PO4, sodium, potassium, calcium, Chloride as well as the acids and bases produced by bacterial metabolism.

Question 30

Plaque fluid anions vary according to the availability of ______.

Answer 30

Fermentable carbohydrate

Question 31

At resting plaque pH the dominant acid species is _____; following exposure to fermentable carbohydrate there is a rise in _____ concentrations and a synchronous fall in _____ concentrations.

Answer 31

- acetate - lactate - acetate

Question 32

Factors affecting the extent and rate pH changes in plaque: - Bacteria composition (_____ and ____) - the _____ and _____ of the plaque - _____: flow rate/ access/ composition - the frequency of _____ - type and consistency of ______ ingested

Answer 32

- type and quantity - thickness and age - saliva - ingestion - carbohydrate

Question 33

_______ utilize more environmental substrate to produce acid at higher rate per unit time than other microorganisms

Answer 33

Strept. mutans

Question 34

Individuals with poor oral hygiene (caries-prone individuals) harbors higher proportion of ______ which produce _______ that cause the fall in plaque pH.

Answer 34

- Strept. mutans | - Stronger acid (lactate)

Question 35

The 3D community of bacteria attached to a surface includes...

Answer 35

- Fluid interaction - Channels/pores - Complex structure

Question 36

Caries-prone individuals also harbor higher proportion of bacteria capable of synthesizing and storing _________ and ________, which serve as CHO storage compound for extended period of acid production.

Answer 36

Intracellular polysaccharides (ICP) and extracellular polysaccharides (ECP)

Question 37

All the factors that determine the extent and rate of pH changes in plaque are risk indicators of dental caries, such as...

Answer 37

- Oral Hygiene - Frequency of eating - Type of food

Question 38

Bacterial organic acids

Answer 38

Formic acid Acetic acid Lactic acid Propionic acid

Question 39

As pH falls... -Trivalent phosphate ions (PO4-3) become ______ -PO4-3 converted to _________ -HPO4-2 weakens the calcium-phosphate bond thereby allowing _____ to be released

Answer 39

- protonated - divalent phosphate ions (HPO4-2) - calcium

Question 40

Remineralization is the delivery of calcium and phosphate, from outside the tooth, into the enamel lesion, effecting deposition of mineral onto the _______ enamel within.

Answer 40

demineralized

Question 41

Fall in pH is _______.

Answer 41

Reversible

Question 42

Biochemical events leading to recovery of plaque pH back to neutrality: - ______ by the salivary components - Proton-binding by the products of _______ - Proton-binding with ________ - Decreased ______ by the bacteria - Diffusion of acid products away into the _____ - Washing away of acid by _____

Answer 42

- Buffering - Mineral dissolution (OH- & PO43-) - Elements on bacterial cell wall - Acid production - Saliva - Saliva

Question 43

The _______ provides about 85% of the total buffer capacity of saliva.

Answer 43

bicarbonate system

Question 44

____ and ____ in saliva constitute the other buffering system, but their concentrations are too low to be of significance

Answer 44

PO4 and Proteins

Question 45

Ammonia production from hydrolysis of urea by the enzyme urease in bacteria, such as ______ and ______.

Answer 45

S. gordonii and S. sanguinis

Question 46

Ammonia production from deamination of amino acids by some oral bacteria by means of the arginine deiminase system (ADS) e.g. ______, ______, and ______.

Answer 46

S. sanguis, S. milleri & b serotype of S. mutans.

Question 47

Ammonia production from coupled oxidation-reduction of pairs of amino acids (_______).

Answer 47

Stickland Reaction

Question 48

Ammonia is highly _____ and causes a rise in ____.

Answer 48

- Alkaline | - pH

Question 49

Decarboxylation of amino acids resulting to the production ____ with the loss of ____ leading to a rise in pH.

Answer 49

- amines | - CO2

Question 50

Ammonia production and decarboxylation of amino acids are only effective in plaque under _________.

Answer 50

Moderate sugar intake

Question 51

Conversion of the stronger lactic acid to weaker acids e.g. -_______ convert lactate to propionate, acetate and ethanol -_______ degrade lactate to acetate and CO2

Answer 51

- Veillonella sp. | - Neisseria sp.

Question 52

When the plaque pH returns to neutrality, ______ of dissolved calcium phosphate occurs.

Answer 52

redeposition

Question 53

Fluoride in solution during de- and remineralization can react with the outer surfaces of dissolving HA crystals thereby forming a shell (of CaF2 nature) that has solubility properties of _______.

Answer 53

fluorapatite

Question 54

Cycles of de- and re- mineralization result to a mineral of ______. A remineralized surface is more resistant to subsequent acid attack than the original apatite.

Answer 54

better quality

Question 55

- During remineralization process different phases of calcium phosphate are formed, such as... - These intermediate products can transform to ______

Answer 55

CaHPO4 CaHPO4.2H2O Ca3(PO4)2 Ca8H2(PO4)6.5H2O HA or FA

Question 56

At least 3 credible fluoride reservoir mechanisms have been proposed: - Deposition of ________ in plaque , tooth surfaces and early lesions - Association of calcium and fluoride with bacteria, particularly ________ - Deposition of _______ in the plaque matrix

Answer 56

- ‘Calcium fluoride-like’ material - Bacterial Lipoteichoic acid (LTA) - Crystalline calcium salts

Question 57

The first reason the rate of formation of FA is relatively slow at resting oral pH values, reducing the pH from 7.0 to ≈ 5.0 increases the rate considerably because....

Answer 57

Low pH may prolong mineral ions’ access to the lesion body by preventing surface-blocking and arrest

Question 58

The second reason the rate of formation of FA is relatively slow at resting oral pH values, reducing the pH from 7.0 to ≈ 5.0 increases the rate considerably because....

Answer 58

Both calcium and fluoride, associated with LTA, are likely to be released during acidogenesis via protonation of anionic binding sites

Question 59

The third reason the rate of formation of FA is relatively slow at resting oral pH values, reducing the pH from 7.0 to ≈ 5.0 increases the rate considerably because....

Answer 59

Calcium-fluoride-like deposits and other calcium salts may dissolve, releasing calcium and/or fluoride at the site of action when needed most, potentiating such effects as laid out above

Question 60

The porous demineralized surface may absorb ______ so that following remineralization the lesion remains dark brown in color.

Answer 60

extrinsic stains