Dental plaque

Question 1

define dental plaque

Answer 1

a community of microorganisms that are found on surface of tooth
- embedded in a matrix of polymers of salivary and bacterial origin

Question 2

how does antibiotic effectiveness differ with bacteria in matrix and free flowing bacteria

Answer 2

bacteria growing in biofilm matrix are less susceptible to antibiotics

Question 3

Dental biofilm formation is divided into 7 stages. what are they

Answer 3

1. conditioning film -acquired pellicle
2. transport of microbes-saliva
3. reversible phase- low range, weak
4. irreversible phase- adhesin-receptor
5. co-adhesion
6. growth and matrix synthesis
7. detachment

Question 4

describe the formation of conditioning film step

Answer 4

1. rapidly formed
2. 1um thick
3. derived from saliva. GCF, and bacteria

Question 5

the molecules which form the pellicle/ conditoning film have host and bacterial origin. give examples of host derived molecules

Answer 5

amylase
Ig
PRP
mucins
statherin 
agglutinin

Question 6

give examples of bacterial derived molecules on the pellicle

Answer 6

glucans

glucosyl-transferase

Question 7

describe the passive transport of microbes via saliva step

Answer 7

transport via saliva
weak
long-range forces between the bacteria and molecules of pellicle

Question 8

what is the reversible phase

Answer 8

the weak, long rage forces between the bacteria and pellicle are mostly VanDerWaals..thus reversible

Question 9

describe the irreversible phase

Answer 9

refers to SPECIFIC ADHESIN-RECEPTOR interactions

bacterium= has own bacterial adhesins.
receptors for such adhesions are either on surface or hidden - cryptitopes

Question 10

give examples of adhesion-receptor interactions and which bacteria the adhesions belong to

Answer 10

streptococcus spp. antigen 1/11 —> bind salivary agglutnin

streptococcus mutans. glucan binding protein —> bind glucan

actinomyces naeslundii. type 1 fimbrae —> bind PRPs

Question 11

describe the co-adhesion step

Answer 11

gram -ve fusobacterium= bridging molecule between early and late colonisers

e. g.
- alpha amylase on tooth surface
- binds to steptococcus oralis
- fusobacterium binds
- allows other bacteria/ organisms to bind such as porph gingivalis

Question 12

describe the biofilm maturation step

Answer 12

1. gram +ve= make peptides= cell signalling
2. gram -ve= make AutoInducer-2 = cell signalling
3. within the biofilm will have food chain reactions (glucose—> lactate–> acetate +proponate) (streptococcus and veillonella respectively)
4. mucins which are glycoproteins are broken down sequentially by glycosidases
5. within the plaque biofilm, the bacteria are all working together to break down substrates
6. altered gene expression

Question 13

why are mucins broken down sequentially

Answer 13

increases the time to metabolise

less effect on reducing pH

Question 14

30% of the plaque volume is…

Answer 14

bacterial polysaccharides: fructan, glucan, mutan, heteropolymers
bacterial polymers: eDNA

Question 15

which enzyme breaks sucrose into glucan and ___

Answer 15

sucrose —> glucan + n-fructose via Glucosyltransferase

Question 16

which enzyme breaks sucrose into fructan and ___

Answer 16

sucrose —> frucatan + n-glucose via Fructosyltransferase

Question 17

describe the detachment step

Answer 17

when bacteria sense the environment no longer favourable, synthesise protease enzymes to degrade their adhesion

Question 18

list the key functions of the matrix within the dental plaque

Answer 18

protection - from host defence 
nutritional reserve
stabilises biofilm - structurally 
interacts with molecules
water retention
retards penetration of antimicrobials

Question 19

list antagonistic interactions within microbial communities

Answer 19

1. bacteriocins - made by bac that inhibits neighbouring bacteria
2. hydrogen peroxide - toxic
3. organic ACIDS
4. low ph
5. nutrient competition

Question 20

list beneficial interactions within microbial communities

Answer 20

food chain/ web
enzyme complementation
cell-cell signalling
inhibitor neutralisation
subversion of host defences 
gene transfer (reistant genes)

Question 21

what is meant by enhanced pathogenicity

Answer 21

within the biofilm, there is spatial and functional organisation
the organisms all POOL together their properties- prevent the molecules of IS penetrating

Question 22

differences between the early and late stages of biofilm maturation

Answer 22

by later there is diverse community, highly anearobic, high cell-cell associations and microbial interactions. there is RESILLIENCE AND BALANCE.

in early there is less diversity, mainly streptococci, mainly aerobic/ facultatively anearobic

Question 23

what structures are seen in a diverse dental biofilm formation

Answer 23

‘corn-cob’ structure