16. Dental Plaque Flashcards
Cycle of plaque build up
- 0-18 hr is initial colonization phase on tooth surface with pellicle
- 18 hr-4d is pre-organization phase
- 4-7 d is microflora alteration phase
- cleaning occurs taking it back to the initial colonization phase
What part of the plaque build up cycle goes wrong for caries?
- no cleaning
- goes to dental caries and gingivitis/periodontitis
- rather than to the intial colonization phase
Why do we need to floss?
- brushing doesn’t remove plaque from gumline
- flossing is used
Attachment and biofilm formation in plaque
- aggregates in saliva drive initial attachment
- biofilms reform from cells that haven’t been removed at gingival margins etc
- uses proteins, glycoproteins that are complex and hard to break down
What’s the one saving grace of oral biofilms?
- most bacteria after sticking to teeth
- are not well adapted to grow in saliva
3 stages of biofilm formation
- attachment
- biofilm initiation
- biofilm development
Environmental factors affecting dental plaque accumulation
- diet
- smokingH
Host factors affecting dental plaque accumulation
- saliva (amount and composition)
Bacterial factors affecting dental plaque accumulation
- adhesins that recongise pellicle
- coaggregation
Dental plaque starts to accumulate … after cleaning
It occurs faster during the day/night?
- minutes
- day
… attach to the saliva pellicle to initiate biofilm
pioneer colonisers
How do bacteria initially attach to teeth?
- primary colinising bacteria in dental plaue attaches to conditioning layer
- is acquired enamel pellicle in teeth
Features of the acquired enamel pellicle
- thickness
- toughness
- presence where?
- composition
-1-3 micrometers thick
- may permeate outer layer of enamel/sub-surface cuticle
- not easily removed
- present on most enamel surfaces
- originally thought to be Nasmyth’s membrane
- now is known as a deposit of saliva proteins
The acquired enamel pellicle is a deposit of what?
saliva proteins
How does the pellicle form?
- precipitation of denatured salivary proteins
- selective absorption of salivary proteins
- tooth surface charged due to calcium and phosphate and molecules bind in proportion to affinity for substrate
- enrichment of high binding rather than medium or low
Additional components of pellicle include …
- gingival crevicular fluid
- oral mucosa
- microbial cells
How do MG2 and MG1 interact with pellicle?
- MG1 is viscous and gets into the pellicle
- MG2 is non-mucin and not involved as much
Role of pellicle in oral environment
- acts as a lubricant to reduce tooth wear
- reduces mobility of calcium and phosphate ions (diffusion barrier and binding of PRP, reduces enamel demineralisation/erosion and caries)
- prevents inappropriate crystal growth (statherin and PRP)
- contains active enzymes
- can inhibit bacterial adhesion
- substrate for bacterial adhesion
What enzymes does the pellicle contain?
- amylase
- lysozyme
- peroxidase
- carbonic anhydrase isotope VI
- glucosyltransferase
Explain how the pellicle is a substrate for bacterial adhesion
- salivary proteins in pellicle act as receptors for bacteria
- has MG1 (sticks within plaque and allows some bacteria to stick/stop some that don’t recognise it to protect tooth surface)
- amylase to bind some strep
- proline-rich proteins
- statherin (changes shape in binding and bacteria attach)
- GP340 (salivary agglutinin) - in lungs for aggregating bacteria and sticking bacteria in pellicle
Role of MG1 in pellicle
- sticks within plaque
- allows bacteria to stick and stops those that don’t recognise it
- protects tooth surface
Role of amylase in pellicle
- some strep can recognise it
- binds to them
Role of statherin in pellicle
- changes shape in binding
- bacteria attach
Role of Gp340 in pellicle
- in lungs for aggregating bacteria
- sticks bacteria in pellicle
… make up over half bacteria in initial plaque
streptococci
… group strep are the most numerous in the mouth
mitis
… group of strep are normally commensal but are associated with a certain issue?
- anginosus
- with absesses
… group of strep are generally commensal and investigated as probiotics?
salivarius
Which group of strep is associated with dental caries?
mutans
There is very little of which kinds of strep in plaque?
- salivarius
- mutans
What is antigen I/II?
- an important streptococcal adhesin
- large protein (around 170 kDa) on surface of oral strep
Role of adhesin I/II
- mediates adhesion of gp340 (salivary agglutinin) in fluid phase or pellicle
- binds bacteria like actinomyces spp. and p.gingivalis
Is there a vaccine against antigen I/II?
- no
- attempts have been made against S. mutans antigen I/II
- lots of things that vaccinate against, not just strep
Antigen I/II is a multi-domain protein. What does this mean?
- it has the N-terminal domain
- alanine-rich repeats
- variable region
- proline-rich repeats
- carboxy-terminal domain, containing motif for wall anchoring
Aside from strep, name 2 pioneer colonisers
- actinomyces spp.
- veillonella spp.
Features of actinomyces spp.
- gram postive
- pleimorphic rods
- facultative anaerobes
- mostly harmless but can cause disease
- A. naeslundii, A. oris, A,israelli
Features of veillonella spp.
- gram negative cocci
- strict anaerobes
- feed on lactate, produced by other oral bacteria
- not associated with disease
- V. atypica, V.dispar
Explain growth-food webs in saliva
- intial growth uses nutrients from saliva
- digestion of salivary glycoproteins requires enzymes contributed by multiple species
- some bacteria use waste products of other species
5 stages of dental plaque formation
- attachment
- growth
- coadhesion
- mature biofilm
- dispersal
Mature supragingival dental plaque contains … microbial cells/gram and has a … appearance
- around 10 to the 11
- stratified appearance (gram positive cocci and short rods at tooth surface, filaments towards outer layers)
How does mature supragingival plaque cause problems?
- caries follows shift towards acidogenic/aciduric bacteria
- gingivitis occurs when plaque grows below gumline
What occurs if there is failure to control dental plaque?
- doesn’t directly correlate with dental caries
- accumulation of plaque at gum margins irritates tissue and forms calculus
- leads to gingivitis, untreated this can become periodontitis
Gingivitis is … but periodontitis is …
- reversible
- destructive
In health, the subgingival crevice has how many of what kind of bacteria?
- relatively few (10 to the 3 to 6 CFU)
- anaerobic bacteria not usually found elsewhere in mouth or on dorsal surface of the tongue
- find some asaccharolytic, proteolytic bacteria but not same as in perio disease (fewer treponemes or A. actinomyucetemcomitans)
Microbial changes in subgingival plaque
- strep sp.
- fusobacterium nucleatum
- treponema denticola
- porphyromonas gingivalis
What is fusobacterium nucleatum?
- gram negative, proteolytic, anaerobic, long rod-shaped cells
- coaggregates with early colonisers (e.g strep spp.) and late colonisers (e.g T.denticola)
- can invade host epithelium
- present in high numbers in subgingival plaque (over 20% of total bacteria)
Dental calculus is also known as …
tartar
Supragingival calculus is a deposit from … whereas subgingival is from …
- saliva
- serumS
Subgingival calculus is also known as …
- serumnal calculus
How does calculus affect mouth?
- rough surface of calculus triggers inflammation
- leads to gingavitis and ultimately periodontitis
Role of tartar in skeletons
- useful source of DNA
- to analyse ancient dental plaque microbiomes
Where does calculus form?
- preferentially near salivary duct openings
Calculus is … and the epitactic agent is …
- mineralised plaque
- probably a bacterium
What are sialoliths?
- supersaturated calcium phosphate forms
- in salivary ducts
- at high pH
