Role of Oral Biofilm (Amaechi 5) Flashcards
Caries is a _____ dependent oral disease.
Biofilm
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.
- selective
- hydroxyapatite-reactive
Pellicle composition:
- ___% amino acids (___% acidic)
- ___% Carbohydrates
- ___% Lipids
- 45-50%, 20%
- 10-15%
- 23%
Functions of the pellicle include:
- _____ of microorganisms
- _____ – by selective permeability
- ______ for microorganisms
- Attachment
- Protection
- Substrate/nutrient
_______ is a population of microorganisms growing on a surface, firmly attached to and enmeshed in an extracellular polysaccharide matrix.
Plaque Biofilm
Bacterial plaque is soft, densely packed mass consisting by dry weight of:
___% bacteria
___% intercellular matrix
- 70%
- 30%
The intercellular matrix is composed of:
- Carbohydrate ____%
- Protein ____%
- Lipid ____%
- Inorganic elements (including ____, ____, and ____)
- Carbohydrate 13-18%
- Protein 40-50%
- Lipid 10-14%
- Inorganic elements (including calcium, phosphate, and fluoride)
Plaque is not removed by mouth rinsing, but is easily removed by ______.
Mechanical means (prophylaxis)
Classifications of plaque
- Supragingival
2. Subgingival
Supragingival plaque
- located above the gingivae
- bacteria population predominantly Streptococcus spp. and Actinomyces spp.
Subgingival plaque
- located underneath the gingivae
- predominantly anaerobic organisms
Part of dental plaque formation is expression of _____, _____, _____, and _____ by S. mutans.
- Adhesin (Antigen I/II)
- Glucosyltransferase (gtf B,C, D)
- Fructosyltransferase (ftf)
- Glucan binding protein (GBP)
_______ phase is characterized by rapid bacterial growth mediated by extracellular glucans and streptococcal glucan receptors.
Colonization (Accumulation)
______ phase: early dominance by Streptococci followed by a shift towards more anaerobic and filamentous flora.
Remodeling
3 stages of plaque formation
- Initial attachment phase
- Colonization (Accumulation) phase
- Plaque biofilm formation phase
Plaque composition:
- Total bacteria count
- Streptococci %
- ≈ 2 x 1011 bacteria/g
2. 17-38%
____ and ____ are present in high proportions on all sites on tooth surface.
Streptococcus and Actinomyces
Carbohydrates of plaque composition exist mainly as extra-cellular polymers…
- Glucans (dextrans and mutans)
- Fructans (levans)
- Heteropolysaccharides
Glucan-producers
Strep. mutans
L. casei
L. acidophilus
Fructan-producers
Actinomyces viscosus
Strep. mutans
Heteropolysaccharides-producers
Actinomyces viscosus
Proteins of plaque composition have contributions from the following components of bacteria…
glucosyl transferase glucanhydrolase hyaluronidase phosphatase Protease amylase
Proteins of plaque composition have contributions from the following components of saliva and gingival fluid…
amylase lysozyme IgA IgG IgM Albumin
Lipids of plaque composition are mainly a component of bacterial ______.
Cell membrane
Inorganic components of plaque composition are _____, _____, and _____.
Fluoride, Ca, and PO4
______ is present in high concentration (14-20 ppm) and mainly bound to other inorganic components and bacteria.
Fluoride
____ and ____ are also in high concentration and bound to saliva-derived proteins e.g. statherin.
Ca and PO4
Plaque can be separated by centrifugation into
liquid (______) and solid (_______) phases.
-plaque fluid
-bacteria/insoluble
Matrix components
Plaque fluid composition
Fluoride, Ca, PO4, sodium, potassium, calcium,
Chloride as well as the acids and bases produced by
bacterial metabolism.
Plaque fluid anions vary according to the availability of ______.
Fermentable carbohydrate
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.
- acetate
- lactate
- acetate
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
- type and quantity
- thickness and age
- saliva
- ingestion
- carbohydrate
_______ utilize more environmental
substrate to produce acid at higher rate per
unit time than other microorganisms
Strept. mutans
Individuals with poor oral hygiene (caries-prone individuals) harbors higher proportion of ______ which produce _______ that cause the fall in plaque pH.
- Strept. mutans
- Stronger acid (lactate)
The 3D community of bacteria attached to a surface includes…
- Fluid interaction
- Channels/pores
- Complex structure
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.
Intracellular polysaccharides (ICP) and extracellular polysaccharides (ECP)
All the factors that determine the extent and rate of pH changes in plaque are risk indicators of dental caries, such as…
- Oral Hygiene
- Frequency of eating
- Type of food
Bacterial organic acids
Formic acid
Acetic acid
Lactic acid
Propionic acid
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
- protonated
- divalent phosphate ions (HPO4-2)
- calcium
Remineralization is the delivery of calcium and phosphate, from outside the tooth, into the enamel lesion, effecting deposition of mineral onto the _______ enamel within.
demineralized
Fall in pH is _______.
Reversible
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 _____
- Buffering
- Mineral dissolution (OH- & PO43-)
- Elements on bacterial cell wall
- Acid production
- Saliva
- Saliva
The _______ provides about 85% of the total buffer capacity of saliva.
bicarbonate system
____ and ____ in saliva constitute the other buffering system, but their concentrations are too low to be of significance
PO4 and Proteins
Ammonia production from hydrolysis of urea by the enzyme urease in bacteria, such as ______ and ______.
S. gordonii and S. sanguinis
Ammonia production from deamination of amino acids by some oral bacteria by means of the arginine deiminase system (ADS) e.g. ______, ______, and ______.
S. sanguis, S. milleri & b serotype of S. mutans.
Ammonia production from coupled oxidation-reduction of pairs of amino acids (_______).
Stickland Reaction
Ammonia is highly _____ and causes a rise in ____.
- Alkaline
- pH
Decarboxylation of amino acids resulting to the
production ____ with the loss of ____ leading to
a rise in pH.
- amines
- CO2
Ammonia production and decarboxylation of amino acids are only effective in plaque under _________.
Moderate sugar intake
Conversion of the stronger lactic acid to weaker
acids e.g.
-_______ convert lactate to propionate, acetate and ethanol
-_______ degrade lactate to acetate and CO2
- Veillonella sp.
- Neisseria sp.
When the plaque pH returns to neutrality, ______ of dissolved calcium phosphate occurs.
redeposition
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 _______.
fluorapatite
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.
better quality
- During remineralization process different phases of calcium phosphate are formed, such as…
- These intermediate products can transform to ______
CaHPO4
CaHPO4.2H2O
Ca3(PO4)2
Ca8H2(PO4)6.5H2O
HA or FA
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
- ‘Calcium fluoride-like’ material
- Bacterial Lipoteichoic acid (LTA)
- Crystalline calcium salts
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….
Low pH may prolong mineral ions’ access to the lesion body by preventing surface-blocking and arrest
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….
Both calcium and fluoride, associated with LTA, are likely to be released during acidogenesis via protonation of anionic binding sites
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….
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
The porous demineralized surface may absorb ______ so that following remineralization the lesion remains dark brown in color.
extrinsic stains
