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Caries and pulpal infections share the same features, they are?
1. caused by normal microbiota
2. tissues are irreversibly damaged
3. neither can undergo spontaneous remission
4. neither can be treated by abx
Prevalence of apical periodontitis?
Before age 50 (30%)
After age 50 (50%)
Over 60 (62%)
Define dental plaque?
diverse community of microorganisms adhered to tooth a complex biofilm embedded in extracellular polymers
Materia alba, define?
bugs, leukocytes, desquamated oral epithelium
bug community, firmly attached to a substratum, interface, or each other, in polymer matrix produced by themselves, altered phenotypes
Bacterial biofilms comprise what percentage of infections?
unattached MO cells
Advantages of being a biofilm?
1. Broader habitat for growth. Early colonizers setting stage for late.
2. Increased metabolic diversity and efficiency (food chains and webs)
3. Protection (from each other, host, environment)
4. Enhanced ability to cause disease
What is horizontal gene transfer?
movement of genetic material between unrelated bacterial species
(adv of biofilm)
What is quorum sensing?
bacteria communication via diffusing of signal molecules (autoinducers)
What is pathogenic synergism?
Bacteria working together to cause disease, diverse virulence traits
Mechanism of abx resistance of a biofilm?
1. Biofilm structure resists penetration (retained neutralizing enzymes in biofilm)
2. Bacteria in stationary phases, if stationary then inactive and not growing, abx work on divding bacteria
3. Subpopulation of persisters (survivors)
Name two types of auto-inducers?
Acyl homoserine lactones (-)
Modified oligopeptides (+)
What does quorum sensing regulate?
2. compentence of DNA uptake
3. entry into stationary phase
4. biofilm formation
BF Formation (Stage 1) conditioning salivary film?
(acquired pellicle) host and bacterial molecules coating enamel
varies in thickness .1-.3 um
BF Formation (Stage 2) transport of bacteria to pellicle tooth coated surface?
bacteria in planktonic state brought into contact w/ tooth surface
BF Formation (Stage 3) early reversible adhesion?
early colonizers, weak interactions, initial adhesion
BF Formation (Stage 4) stronger interactions?
stronger interactions between bacterial adhesins and pellicle receptors
early colonizers grow and modify environment
include s. mitis, s. oralis
BF Formation (Stage 5) latecomers?
Binding of latecomers (coaggregation)
Between genetically different cells unlike agglutination or aggregation
BF Formation (Stage 6) multiplication of the attached bacteria?
increased pop density
BF Formation (Stage 7) detachment?
Sessile ones produce enzymes that break adhesins and allow planktonic bacteria to colonize other surfaces.
Caries can be categorized as follows:
Occlusal (pit and fissure)
Dental caries of enamel is first observed as:
white spot lesions
What is awhite spot lesion?
demineralized subsurface enamel
white because of changes in refractive index
50% mineral loss (as much as)
What acid is formed in biofilms leading to caries?
Lactic, formic, acetic, and propionic
What promotes dissolution of tooth mineral?
diffusing of hydrogen ion
Lost calcium and phosphate and fluoride can diffuse back into noncavitated lesion forming mineral crystal surface
much stronger than original carbonated hydroxyapatite
Define the non-specific plaque hypothesis?
caries develops by overall activity of plaque microbiota
Define the specific plaque hypothesis?
Only one or few species are responsible for caries
Define the ecological plaque hypothesis
shift in natural balance of the resident plaque microbiota
significant change in environment changes the whoel community causing cariogenic bacteria to outcompete
pH is this factor (s. mutans, lactobacilli)
critical enamel pH is 5.5
Who and what is the chemoparasitic theroy?
oral bacteria convert dietary carbohydrates to acids dissolving calcium phosphate of enamel
Three properties common to cariogenic bacteria
1. rapid transport of sugar
2. convert rapidly to acid
3. do so under low pH
ability to produce intra(more acid) extracellular polysaccharides (more adhesion)
Acidogenic and aciduric?
produce acid, and do so under low pH
Who and when isolated s. mutans?
s. sobrinus now too
Two methods of attachment of s. mutans to tooth surface?
Sucrose independent and dependent
Ind: adhere to salivary proteins, others, lectinlike interactions
Dep: break sucrose into fructosyl (into cell) and glucosyl
glucosyl polymerized into extracellular polysaccs glucans (mutan and dextran)
mutan: higly branched insoluble biologic glue
What role due lactobacilli play in caries formation?
They do not form but propagate the lesion, their adherence is low
not high producers of extracell polysaccs
What species increase pH?
Veillonella and Actinomyces
What % of microbiota are yet to be id in caries lesion?
What is the zone of destruction?
Superficial layer of dentin decomposed by acid in a cavitated lesion
What is the zone of demineralization?
separates the infected dentin from sclerotic dentin
What bugs predominate as carious lesion progresses?
Lactobacilli and/or proteolytic anaerobic bacteria like prevotella
What is responsbile for symptoms of a cavity?
Ammonia and indole produced by anaerobic bacteria
LPS from gram (-)
What are some first line host defense antimicrobial systems in saliva?
Primary mechanisms of fluroide?
inhibits demineralization: adsorbes to surface of carbonated hydroxyapatite, resists acid dissolution
enhances remineralization: by adsorbption it attracts calcium and phosphate ions, a fluorapatite like crystal forms
inhibits bacterial metabolism: fluoride combins with hydrogen ions goes into cell and acidfy cell and fluoride interferes with bacterial enzymes
What lines the dentinal tubules?
Lamina limitans, sheathlike
What is anachoresis?
Theory, bacteria from gingival crevice or perio pocket reach the root canals through severed bloods vessels of periodontium during trauma
Estimated number of bacterial cells in oral cavity? Species?
700 taxa, 13 phyla
50-60% remain to be cultivated
What major ecological factors determine composition of root canal microbiota?
- O2 tension
- type and amount of nutrients
temp, pH, receptors for adhesins
Main sources of nutrients for bacteria in root canal?
1. necrotic tissue
2. proteins and glycoproteins from tissue exudate via apical and lateral foramina
3. components of saliva
4. products from other bacteria
What is amensalism?
Seen as a negative interaction between bugs, production of substance inhibits other species
C. Albican % in primary infection?
Archae type detected in primary infections?
Which viruses are detected in apical periodontitis?
Epstein Barr and CMV
Secondary intraradicular infections, cause?
MO not present in primary infection, some time after professional intervention
either during treatment, between appoint, or even after root canal filling
Predominant MO in persistent or secondary infections?
Gram positive or facultative anaerobics
Persistent and secondary infections are a major cause of endo failure, why?
1. inc risk of adverse tx outcome when bacteria are present in the canal at time of obturation
2. most obturated teeth have been shown to harbor intraradicular infections
What do residual bacteria have to do to cause persisten apical periodontitis?
1. adapt to changed environment during treatment, antimicrobial effects of root filling
2. reach critcal numbers for virulence
3. unrestrained access to periradicular tissues
4. induce host reponse
E. Faecalis prevalence in endodontically tx teeth?
9 times more likely
Situations that permit Actinomyces or P propionicum to reach periradicular tissue?
1. Apical extrusion of debri during instrumentation
2. direct advance from the infected root canal into the lumen pocket cysts
3. previous participation in acute apical abscesses, followed by persistence after acute response subsides
Percent corresponding apical actinomycosis of apical perio?
What are three potential antigens of s. mutans for vaccine development?
Surface fibrillar adhesins (antigen I/II)
Glucan binding proteins